NRLF 73fi THE SCHUYLKILL COUNTY MEDICAL LIBRARY $ NO.. PRESENTED BY A THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA PRESENTED BY PROF. CHARLES A. KOFOID AND MRS. PRUDENCE W. KOFOID AN ELEMENTARY TREATISE HUMAN ANATOMY. BY JOSEPH LEIDY, M.D., PROFESSOR OF ANATOMY IN THE UNIVERSITY OF PENNSYLVANIA; CURATOR OF THE ACADEMY OF NATURAL SCIENCES; MEMBER OF THE AMER. PHILOS. SOC. J COL. OF PHYSICIANS, PHILADELPHIA; AMER. ACAD. OF ARTS AND SCIENCES; NAT. HIST. SOC., BOSTON; LYC. NAT. HIST., NEW YORK; ELLIOT NAT. HIST. SOC., CHARLESTON; MED. SOC. OF VIRGINIA; ACAD. OF SCIENCES, ST. LOUIS; IMP. SOC. OF NATURALISTS, MOSCOW; IMP. LEOPOLD. CAROL. ACAD. OF SCIENCES, JENA ; BOY. ACAD. OF SCIENCES, MUNICH ; BIOLOG. SOC., PARIS; soc. OF ARTS AND SCIENCES, MONS; ZOOLOG. soc., LQNDON; UNIV. ZOOL. AND EOT. ASSOO., DUBLIN, ETC. WITH THREE HUNDRED- AND NINETF-TWO ILLUSTRATIONS. PHILADELPHIA : J. B. LIPPINCOTT & CO. 1861. Entered, according to act of Congress, in the year 1860, by JOSEPH LEIDY, M.D., In the Clerk's Office of the District Court of the United States for the Eastern District of Pennsylvania. PREFACE. As indicated by its title, the present work is intended as an elementary treatise on human anatomy, and is not an elaborate system adapted to the use of those who have already advanced in anatomical knowledge. The author has attempted to prepare such a book as he feels would have been of service to himself in the commencement of his studies, and he hopes it may be found worthy of the approbation of students, for whom, and by whose frequent solicitation, it was written. Much of the difficulty, of which we hear constant complaint, in the acquisition and retention of anatomical knowledge, arises from an excessive, and, in some other respects, objectionable no- menclature. Not only has' the naming of comparatively unim- portant parts been carried to an extreme, but, in numerous instances, the same parts are designated by a multitude of names, which are indiscriminately used by different writers. The nomen- clature of anatomy has been founded on no particular system ; the names having been chosen, according to the fancy of anato- mists, from the shape, function, or supposed resemblance of the part, or in commemoration of the original investigator. In some measure to avoid the difficulty to which we refer, the author has adopted the plan of generally using a single name for each part ; (iii) iv PREt of the many names employed, to use that which is most expres- sive of the character of the part ; and, when admissible, the name is anglicized. A copious synonymy is added, in foot-notes, which may be found useful for future reference. Many of the drawings accompanying the work are original, and were made by the author, or by his friend Dr. H. D. Schmidt, favorably known for his anatomical investigations. The excellent wood engravings, with few exceptions, are from the masterly hand of August Wilhelm, a young artist of this city. CONTENTS. CHAPTER I. PAGE INTRODUCTION - - - - - - - - - - - -17 Ultimate Chemical Elements of the Human Body .... 25 Proximate Chemical Elements of the Human Body - - - - 20 Group 1. Nitrogenized Elements peculiarly Organic 26 " 2. Non-Nitrogenized Elements peculiarly Organic - - 27 " 3. Elements not peculiarly Organic ----- 28 " . 4. Elements arising from the disintegration of the different parts of the body, for the most part expelled in the excretion ---------28 Ultimate Physical Elements of the Human Body 29 The Proximate Physical Elements of the Tissues of the Human Body - 32 CHAPTER II. THE SKELETON --___-____-_ 33 Development and Growth of the Skeleton 42 Articulations or Joints of the Skeleton - - - - - - 46 Of the Relative Position of the Different Structures entering into the Composition of Articulations ------- 48 Bones of the Head or Skull 50 Bones of the Cranium ----------50 The Occipital Bone 50 The Sphenoid Bone 52 The Ethmoid Bone - 56 The Frontal Bone "- - - -58 The Parietal Bone ---60 The Temporal Bone 61 Structure and Articulation of the Bones of the Cranium 65 General Conformation of the Cranium -------67 Mechanical Construction of the Cranium ------ 70 Development of the Cranium --------73 Supernumerary Bones of the Cranium 75 Bones of the Face ---------- 75 The Superior Maxillary Bone -------- 7G The Palate Bone 78 The Lachrymal Bone -----__-_ 80 The Nasal Bone 81 The Turbinated Bone - - 81 The Vomer 82 The Malar Bone 83 v j CONTENTS. THE SKELETON Continued. PAGE The Inferior Maxillary Bone - 83 Structure and Articulation of the Bones of the Face ... 85 The Temporo-maxillary Articulation - 86 General Conformation and Position of the Face - 87 The Side of the Skull 88 The Base of the Skull 90 The Orbits - 91 The Nasal Cavities 92 Development of the Face -94 Changes of the Skull at Different Periods of Life 94 The Hyoid Bone 96 The Trunk 96 The Vertebral Column 97 The True Vertebra 97 The Cervical Vertebrae ----99 The Dorsal Vertebrse 102 The Lumbar Vertebrae ... - 103 The False Vertebrae 103 The Sacrum 104 The Coccyx 105 Development of the Vertebrae --'.;- ----106 Articulations of the Vertebral Column 107 Articulations of the Occipital Bone, the Atlas, and the Axis - - 111 The Vertebral Column viewed Entire - - -. - - 113 The Ribs 114 The Sternum - - 117 Articulations of the Ribs with the Vertebrae and Sternum - - ^118 The Thorax - 119 The Hip or Innominate Bones - - 121 Articulations of the Hip Bones ------- 125 The Pelvis - 126 Sexual Differences of the Pelvis -128 The Upper Extremities -_.- .___ 129 Bones of the Shoulder ------ ... 129 The Clavicle 129 The Scapula - - 130 Bones of the Arm and Forearm - - - - - - - -132 The Humerus - - - 132 The Ulna 134 The Radius , ,- ' 135 Bones of the Hand - - 136 Bones of the Carpus 136 Bones of the Metacarpus --------- 138 Bones of the Fingers 139 The Hand - - 140 Development of the Bones of the Upper Extremities - 141 Articulations and Movements of the Upper Extremities. The Sterno- clavicular Articulation 141 CONTENTS. Vii THE SKELETON Continued. PAGE The Scapulo-clavicular Articulation ------- 142 The Shoulder Joint - - 143 The Elbow Joint - - - - 144 The Superior Radio-ulnar Articulation - - - - - - 145 The Middle " " 145 The Inferior " " 145 The Wrist Joint, or Radio-carpal Articulation ----- 146 The Intercarpal and Carpo-metacarpal Articulations - 147 The Metacarpo-phalangial and Phalangial Articulations - 147 The Lower Extremity 148 The Femur 148 The Patella 150 The Bones of the Leg 150 The Tibia 150 The Fibula - 152 Bones of the Foot ----- 153 Bones of the Tarsus 153 Bones of the Metatarsus 156 Bones of the Toes 157 The Foot 157 Development of the Bones of the Lower Extremity - 158 Articulations and Movements of the Lower Extremities - - - 158 The Hip Joint 159 The Knee Joint 160 The Tibio-fibular Articulations 163 The Ankle Joint 163 The Intertarsal and Tarso-metatarsal Articulations Articulations of the Astragalus, Calcaneum, and Scaphoid Bone - - - - 164 Articulation of the Calcaneum and Cuboid Bone - - - - 165 Articulation of the Scaphoid, Cuboid, and Cuneiform Bones together and with the Bases of the Metatarsal Bones ----- 165 Metatarso-phalangial and Phalangial Articulations - - - - 166 CHAPTER III. THE FIBROUS, CARTILAGINOUS, FIBRO-CARTILAGINOUS, ELASTIC, AND ADIPOSE TISSUES 167 Fibrous Tissue .... 167 Cartilage and Fibro-cartilage - - - 171 Elastic Tissue 175 Adipose Tissue --176 CHAPTER IV. THE MUSCULAR SYSTEM - - - - - - -- - - 178 General Remarks on the Head 183 Fascia of the Head ---- 185 Muscles of the Scalp 185 Muscles of the Eyelids and Eyebrows ------ 187 viii CONTENTS. THE MUSCULAR SYSTEM Continued. PAGE Muscles of the Nose 188 Muscles of the Lip and Cheek - - - - r - - - 188 The Muscles of the Lower Jaw, or of Mastication - 191 The Neck - - 193 Muscles and Fasciae of the Neck. The Subcutaneous Cervical Muscle 193 The Cervical Fascia - 194 The Sterno-mastoid Muscle 195 Depressors of the Hyoid Bone and Larynx - 195 Elevators of the Hyoid Bone and Larynx - - - - - 196 Deep Muscles of the Front of the Neck - - - - - -197 Topographical Sketch of the Anatomy of the Neck - 199 Front of the Thorax 200 Muscles of the Front and Sides of the Thorax 201 The Back - - - - 203 Superficial Muscles of the Back ----- - 203 Deep Muscles of the Back, or Extensors of the Head and Trunk - 206 Muscles of the Ribs 210 The Abdomen ------ 211 Superficial Fascia of the Abdomen 212 Muscles of the Abdomen - - - - - - - - -213 The Lumbar Fascia 218 The Transverse Fascia of the Abdomen 218 The Inguinal Canal 219 Remarks on Inguinal Hernia - - - - - - - . - 220 The Diaphragm - 221 The Upper Extremity 223 Fasciae of the Upper Extremity 224 Muscles of the Shoulder 226 Muscles of the Arm 227 Muscles of the Front of the Forearm 230 Muscles of the Back of the Forearm - 233 Muscles of the Hand 236 Muscles of the Ball of the Thumb - 236 Muscles of the Little Finger - - 237 The Interosseous Muscles - 237 The Lower Extremities - - - 238 Fasciae of the Lower Extremity 238 Sketch of the Anatomy concerned in Femoral Hernia - - - 242 Muscles of the Buttock 244 The Iliac Fascia 247 Muscles of the Iliac Region and Loin - - - - - - 247 Muscles on the Front of the Thigh - 248 Muscles on the Back of the Thigh 250 Muscles of the Front and Outer Part of the Leg, and Upper Part of the Foot 252 Muscles on the Back of the Leg 254 Muscles of the Sole of the Foot 256 The Interosseous Muscles of the Foot 258 CONTENTS. i x CHAPTER V. PAGE ANATOMICAL ELEMENTS OF SEROUS AND Mucous MEMBRANES, THE GLANDS, THE LUNGS, AND THE SKIN --------- 259 Serous Membranes ---------- 268 Mucous Membranes ---------- 266 The Glandular System 267 Unstriated Muscular Tissue -------- 271 CHAPTER VI. THE ALIMENTARY APPARATUS _________ 273 The Mouth 273 Muscles of the Palate and Fauces ------- 277 The Salivary Glands 278 The Tongue 280 Muscles of the Tongue 283 The Teeth 285 Characters of the Permanent Teeth 286 Characters of the Temporary Teeth 288 Structure of the Teeth 289 Development of the Teeth 292 The Pharynx 294 Muscles of the Pharynx --------- 295 The (Esophagus --------__ 297 The Cavity of the Abdomen - - - - - - - 298 The Peritoneum -------.._ 300 The Stomach 395 The Small Intestine 309 The Large Intestine - 315 The Rectum 318 The Pancreas --__.__ ._ 320 The Liver 321 Structure of the Liver ----...__ 324 Biliary Ducts and Gall-bladder 328 The Spleen - 329 CHAPTER VII. THE VASCULAR SYSTEM 332 General Character of the Arteries ------- 332 General Character of the Veins 335 The Capillaries .... 337 The Blood 333 The Heart 341 Structure of the Heart - - - - 347 The Pericardium 349 Mechanism of Action of the Heart 349 The Arteries 351 x CONTENTS. THE VASCULAR SYSTEM Continued. PAGE The Aorta 351 The Arch of the Aorta - - 351 The Coronary Arteries ._------- 353 The Innominate Artery --------- 353 The Common Carotid Artery --- 354 The External Carotid Artery 355 The Internal Carotid Artery 363 The Subclavian Arteries 367 The Axillary Artery - 372 The Brachial Artery 374 The Radial Artery - 376 The Ulnar Artery 379 Thoracic Aorta 381 Abdominal Aorta ---------- 383 The Coeliac Axis - - - - 384 The Superior Mesentery Artery 386 The Inferior Mesentery Artery 388 The Middle Sacral Artery - 389 Arteries in Pairs from the Abdominal Aorta - 389 The Common Iliac Arteries -------- 390 The Internal Iliac Artery 391 The External Iliac Artery 395 The Femoral Artery 396 The Popliteal Artery 399 The Anterior Tibial Artery 400 The Dorsal Pedal Artery 401 The Posterior Tibial Artery * 402 The Pulmonary Artery 405 The Veins 405 The Coronary Vein 405 The Superior Cava ... - - 406 The Innominate Veins - 406 Veins of the Head and Neck - 408 The Internal Jugular Vein 409 Sinuses of the Dura Mater - - -"- - - - - - 409 Veins of the Brain - 412 The Diploic and Meningeal Veins ------- 413 The Ophthalmic Vein 413 The External Jugular Vein - - - - - - - -413 The Facial Vein 414 The Temporal Vein - 414 The Internal Maxillary Vein 415 The Temporo-maxillary Vein -------- 415 The Posterior Auricular Vein 415 The Occipital Vein - 416 The Veins of the Tongue 416 The Pharyngeal Vein 416 The Superior Thyroid Veins 416 CONTENTS. XI THE VASCULAR SYSTEM Continued. The Veins of the Upper Extremities ------ The Subclavian Vein -------- The Deep Veins of the Upper Extremity - - - - - The Superficial Veins of the Upper Extremity The Azygos Vein - - - - -- The Inferior Cava - Branches of the Inferior Cava ------- The Portal Vein The Veins of the Vertebral Column ------ The Common Iliac Veins ------- The Internal Iliac Vein -___-___ The External Iliac Vein The Deep Veins of the Lower Extremity The Superficial Veins of the Lower Extremity - The Pulmonary Veins The Lymphatic System -------- The Trunks of the Lymphatic System The Thoracic Duct The Right Lymphatic Duct -_--._. Lymphatics of the Head and Neck ------ Lymphatics of the Cranial Cavity Lymphatics of the Exterior of the Cranium - - - - Lymphatics of the Face Lymphatics of the Neck -------- Lymphatics of the Upper Extremities, and of the Exterior of Thorax Lymphatics of the Cavity of the Thorax - Lymphatics of the Lower Extremities and of the Pelvis - Lymphatics of the Cavity of the Abdomen - - - - - the PAGE 416 417 417 417 419 420 420 421 423 423 424 425 426 426 428 428 430 431 432 432 432 433 434 434 435 435 437 438 CHAPTER VIII. THE VOCAL AND RESPIRATORY APPARATUS - The Larynx - Cartilages of the Larynx - - - - Articulations and Ligaments of the Larynx Muscles of the Larynx - The Cavity of the Larynx The Organs of Respiration The Trachea The Lungs ------- The Pleura The Thyroid Body The Thymus Body - ... 440 440 440 442 443 445 447 447 450 454 455 456 xii CONTENTS. CHAPTER IX. PAGE THE URINARY ORGANS 458 The Kidneys 458 The Urinary Bladder - 462 The Urethra 465 The Supra-renal Bodies --------- 465 CHAPTER X. THE GENERATIVE APPARATUS - -- - - - - - - 468 The Male Organs of Generation ------- 468 The Testicles 468 The Seminal Vesicles and Ejaculatory Ducts 473 The Penis 475 The Urethra of the Male 478 The Prostate and Suburethral Glands 480 The Female Organs of Generation ------- 481 The Uterus 481 Ligaments of the Uterus 484 The Ovaries 485 The Parovarium ----- -..._ 437 The Fallopian Tubes, or Oviducts 488 The Vagina 489 The Vulva - ... 491 The Cavity of the Pelvis 494 The Perineum 496 The Pelvic and Perineal Fascise 496 Muscles of the Perineum. --------- 498 The Mammae 499 CHAPTER XI. THE NERVOUS SYSTEM 503 General Character and Structure of the Cerebro-spinal Axis - - 503 General Character and Structure of the Cerebro-spinal Nerves - 507 Origin and Termination of the Cerebro-spinal Nerves -'' 509 General Character and Structure of the Sympathetic Nerves - - 511 General Character and Structure of the Ganglia - 512 The Cerebro-spinal Axis, or Brain and Spinal Cord - - - - 513 The Brain 514 The Cerebrum 515 Fornix - 521 Pellucid Septum 521 Lateral Ventricles 621 Corpora Striata, or Striated Bodies - - - - - - 523 Third Ventricle 523 Thalami 524 Quadrigeminal Body 525 CONTENTS. x iii THE NERVOUS SYSTEM Continued. PAGE Pineal Gland 526 Commissures of the Third Ventricle 526 The Cerebellum 526 Dentated Body -- 528 Crura of the Cerebellum 528 The Pons 529 The Medulla Oblongata 530 Fourth Ventricle 531 The Spinal Cord 533 Membranes of the Brain and Spinal Cord ----- 535 The Pia Mater 535 Pia Mater of the Brain 535 Pia Mater of the Spinal Cord 536 The Ependyma ---- 537 The Dura Mater 537 Dura Mater of the Brain - - - -- - - - 537 Dura Mater of the Spinal Cord 539 The Arachnoid Membrane -------- 539 The Nerves of the Brain, or the Cerebral Nerves - - - - 540 The Olfactory, or First Pair of Nerves - 540 The Optic, or Second Pair of Nerves 541 The Oculo-motor, or Third Pair of Nerves ----- 541 The Pathetic, or Fourth Pair of Nerves 542 The Trifacial, or Fifth Pair of Nerves - 542 The Ophthalmic Nerve - 543 The Ophthalmic Ganglion -------- 544 The Superior Maxillary Nerve -------- 545 The Spheno-palatine Ganglion --_____ 545 The Inferior Maxillary Nerve -------- 543 The Otic Ganglion ._ ... 559 The Submaxillary Ganglion -------- 559 The Abducent, or Sixth Pair of Nerves 550 The Facial, or Seventh Pair of Nerves ------ 551 The Auditory, or Eighth Pair of Nerves ----*-- 553 The Glosso-Pharyngeal, or Ninth Pair of Nerves - 553 The Pneumogastric, or Tenth Pair of Nerves ----- 555 The Accessory, or Eleventh Pair of Nerves ----- 553 The Hypoglossal, or Twelfth Pair of Nerves - ... 559 The Spinal Nerves 559 The Cervical Nerves - - 561 Posterior Branches of the Cervical Nerves ------ 561 Anterior Branches of the Cervical Nerves - - - - - 562 The Cervical Plexus ----- 562 The Brachial Plexus 563 The Thoracic Nerves 570 Posterior Branches of the Thoracic Nerves ----- 571 Anterior Branches of the Thoracic Nerves 571 The Intercostal Nerves 571 xiy CONTENTS. THE NERVOUS SYSTEM Continued. PAGE The Lumbar Nerves ---------- 572 The Lumbar Plexus ---- 573 The Sacral and Coccygeal Nerves ------- 57$ The Sacral Plexus -_-. 577 The Sympathetic System of Nerves - - - - - - 581 Cervical Portion of the Sympathetic Nerve 582 The Cardiac Plexus 584 ' Thoracic Portion of the Sympathetic Nerve 585 The Solar Plexus 585 Lumbar and Sacral Portions of the Sympathetic Nerves - - - 587 The Hypogastric Plexus 587 CHAPTER XII. THE ORGANS OF SPECIAL SENSE --------- 588 The Nose 588 The Nasal Cavities - - 591 The Eye 594 The Eyebrows ----------- 595 The Eyelids - - - 595 The Conjunctiva __--__-_-. 597 The Lachrymal Apparatus -------- 593 The Eyeball - - 600 Muscles of the Eyeball - - - - 601 The Sclerotica - - - - 602 The Cornea 603 The Choroidea - 604 The Iris 607 The Retina 608 The Aqueous Humor --------- 610 The Crystalline Lens --610 The Vitreous Humor - 611 The Ear 612 The External Ear - 612 The Middle Ear 616 The Internal Ear - - - 621 The Organ of Taste 628 The Skin and its Appendages - - - - - -.- - 628 The Dermis - - 629 The Epidermis 631 The Sweat Glands - 633 The Sebaceous Glands 634 The Hairs ... 636 The Nails 640 LIST OF ILLUSTRATIONS. [Those marked with an asterisk are by the author. The names opposite the others indicate the authorities from which they have been obtained. When the illustrations differ from the original draw- ings they have been altered by the author or by Dr. Schmidt.] FIG. 1 Monas crepusculum.* 2 Vibrios.* 3 Diagram of a typical organic cell.* 4 Trachelomonas volvocina, from stagnant water.* 5 Protococcus, from damp pavements, multiplying by division.* 6 Ciliated epithelial cell.* 7 Progressive division or segmentation of the yolk in the human egg.* 8 Process of multiplication of cartilage cells.* 9 Process of development of an organic cell from a granule.* 10 Three secreting cells from the submaxillary salivary gland.* 11 A lymph corpuscle.* 12 Epithelial cells of a serous membrane.* 13 Exhibits the progressive development of the epidermis.* 14 Mode of development, from below upward, of columnar epithelial cells.* 1.5 Mode of development of unstriated muscular fibre.* 16 Nerve cell* 17 Mode of development of capillary vessels from cells.* 18 Development of striated muscular fibre, from cells.* 19 Development of fibrous tissue.* 20 Longitudinal section of the proximal extremity of the femur. Ibbotson. 21 Horizontal section of the condyles of the femur. Ibid. 22 Vertical section, antero-posteriorly, of the calcaneum. Ibid. 23 Transverse section of the shaft of a phalanx.* 24 Transverse section of bone from the shaft of the femur.* 25 An osseous lacuna.* 26 Thin plate from the ethmoid bone.* 27 Development of the femur. Wilhelm. 28 Development of the vertebrae. Quain Sf Sharpey. 29 Development of the epiphyses to the vertebrae. Ibid. 30 External view of the occipital bone. Wilson. 31 Internal view of the occipital bone. Ibid. 32 Front view of the sphenoid bone. Schmidt. (xv) xvi LIST OF ILLUSTRATIONS. FIG. 33 Upper view of the sphenoid bone.* 34 Upper view of the ethmoid bone. Wilson. 35 External view of the frontal bone. Ibid. 36 Internal view of the frontal bone. Ibid. 37 Outer view of the left parietal bone. Ibid. 38 Inner view of the left parietal bone. Ibid. 39 External view of the temporal bone of the right side.* 40 Internal view of the temporal bone of the left side. Packard. 41 Inferior view of the left temporal bone.* 42 Internal view of the base of the cranium of the left side. Schmidt. 43 External view of the base of the skull, right side. Ibid. 44 Antero-posterior section of the cranium.* 45 Horizontal section of the cranium.* 46 Transverse section through the front of the cranium.* 47 Transverse section in advance of the middle of the cranium.* 48 Transverse section through the middle of the cranium.* 49 Transverse section posterior to the middle of the cranium.* 50 Two pieces of the temporal bone. Quain $ Sliarpey. 51 Superior maxillary bone of the left side. Schmidt. 52 Superior maxillary bone of the left side. Ibid. 53 Posterior view of the right palate bone. Wilson. 54 Exterior view of the right palate bone. Ibid. 55 External view of the right lachrymal bone. Ibid. 56 Anterior view of the left nasal bone. Ibid. 57 External view of the right turbinated bone. Homer. 58 Left side of the vomer. Wilson. 59 Outer view of the right malar bone. Ibid. 60 Inferior maxillary bone. Ibid. 61 Yertical section of the articulation of the lower jaw. Ibid. 62 External view of the temporo-maxillary articulation. Ibid. 63 The skull, seen partly in front and on the right side. Wilhelm. 64 View of the right side of a portion of the face and cranium. Schmidt. 65 Yiew of the right half of the base of the skull. Ibid. 66 Yertical section of the face. Ibid. 67 Yiew of the outer wall of the right nasal fossa. Ibid. 68 The hyoid bone. Wilson. 69 The vertebral column. Morton. 70 Side view of a dorsal vertebra. Wilson. 71 Upper view of a cervical vertebra. Ibid. 72 Upper view of the atlas. Ibid. 73 Side view of the axis. Ibid. 74 Side view of a dorsal vertebra. Ibid. 75 Side view of a lumbar vertebra. Ibid. 76 Front view of the sacrum. Ibid. 77 Back view of the sacrum. Ibid. 78 Posterior view of the coccyx. Morton. LIST OF ILLUSTRATIONS. xv ii FIG. 79 Development of the vertebrae. Quain Sf Sharpey. 80 Development of the epiphyses to the vertebrae. Ibid. 81 Upper view of a lumbar vertebra. Ibid. 82 Yertical section of two lumbar vertebrae. Ibid. 83 Three vertebral arches removed from as many dorsal vertebrae. Wilson. 84 Portion of the occipital bone, with the atlas and axis. Ibid. 85 Three dorsal vertebras. Ibid. 86 Portion of the cranium and of the atlas and axis. Ibid. 87 Bodies of three dorsal vertebrae. Ibid. 88 Portion of the occipital bone, with the atlas and axis. Ibid. 89 Portion of the occipital bone and the upper three cervical vertebrae. Ibid. 90 Portion of the skull, the atlas, and axis. Ibid. 91 Front view of the thorax. Ibid. 92 Anterior view of three dorsal vertebrae and their articulation with the ribs. Ibid. 93 Posterior view of four dorsal vertebrae and their articulation with the ribs. Ibid. 94 Front view of the thorax. Ibid. 95 Inner view of the left hip or innominate bone. Schmidt. 96 Outer view of the left hip or innominate bone. Wilson. 97 Ligaments of the pelvis and hip joint. Ibid. 98 Ligaments of the pelvis and hip joint. Ibid. 99 Front view of a female pelvis. Ibid. 100 Clavicle of the right side. Ibid. 101 The scapula of the left side. Ibid. 102 Anterior view of the scapula. Ibid. 103 Humerus of the left side. Ibid. 104 The two bones of the left forearm. Ibid. 105 Bones of the carpus. Ibid. 106 The left hand. Ibid. 107 Sterno- clavicular, costo-clavicular, and costo-sternal articulations. Ibid. 108 Scapulo-clavicular and scapulo-humeral articulations. Ibid. 109 The elbow joint. Ibid. 110 The same elbow joint. Ibid. 111 Ligaments of the wrist and hand. Ibid. 112 Femur of the right side. Ibid. 113 Patella of the right side. Ibid. 114 Tibia and fibula of the left leg. Ibid. 115 Tibia and fibula of the right leg. Ibid. 11 6 Dorsal surface of the right foot. Ibid. 117 Sole of the left foot. Ibid. 118 Ligaments of the hip. Ibid. 119 The right knee joint. Ibid. 120 Front view of the right knee joint. Ibid. 121 Longitudinal section of the left knee joint. Ibid. 122 Posterior view of the inferior tibio-fibular and ankle joints. Ibid. LIST OF ILLUSTRATIONS. FIG. 123 External view of the right ankle joint. Wilson. 124 Internal view of the ankle joint. Ibid. 125 Ligaments of the sole of the foot. Ibid. 126 Example of fibrous tissue.* 127 Examples of fibrous tissue.* 128 Portion of connective tissue.* 129 Fibrous tissue.* 130 Portion of connective tissue.* 131 Crossing bands of fibrous tissue.* 132 Cartilage.* 133 Vertical section of articular cartilage.* 134 Section of costal cartilage.* 135 Section of costal cartilage.* 136 Section of fibro-cartilage from the auricle of the ear.* 137 Elastic tissue.* 138 Elastic tissue. Kolliker. 139 Elastic tissue. Ibid. 140 Adipose tissue, with connective tissue.* 141 Transverse section of the lower end of the ulno-carpal flexor.* 142 Transverse section of a muscular fasciculus.* 143 Two portions of a muscular fasciculus.* 144 Two muscular fibres.* 145 Fibrils from a muscular fibre of the axolotl. Kolliker. 146 A muscular fibre of a salamander.* 147 Muscles of the head and neck. Sappey. 148 Yiew of the interior part of the left side of the face. Jamain. 149 Yiew of the temporal muscle. After Bonamy Beau, Morton. 150 Inner part of the ramus of the lower jaw. Wilson. 151 Front view of the muscles of the neck. Ibid. 152 Deep muscles of the front of the neck. Morton. 153 Muscles of the front of the thorax and abdomen. Wilson. 154 Muscles of the back. Ibid. 155 Extensor muscles of the back. Ibid. 156 Muscles of the front of the trunk. Ibid* 157 Yiew of the left side of the abdomen. Ibid. 158 Yiew of the inguinal canal. Sappey. 159 Inferior view of the diaphragm. Wilson. 160 Muscles of the back of the scapula. After Bonamy Beau, Morton. 161 Muscles of the front of the scapula. Ibid. 162 The deltoid muscle. Ibid. 163 Muscles of the fore part of the arm. Wilson. 164 Yiew of the triceps extensor, on the back of the right arm. Ibid. 165 Superficial muscles of the front of the forearm. Ibid. 166 Deep muscles of the front of the forearm. Ibid. 167 Metacarpal and phalangial bones of the fingers, with their tendons and ligaments. Quain Sharp ey. LIST OF ILLUSTRATIONS. x i x FIG. 168 Muscles of the back of the forearm. Wilson. 169 Deep muscles of the back of the forearm. Ibid. 170 Muscles of the palmar surface of the hand. Ibid. 171 Yiew of the inguinal canal. Sappey. 172 Muscles of the buttock. Wilson. 173 Muscles of the iliac region and front of the thigh. Ibid. 174 Muscles of the back of the right buttock and thigh. Ibid. 175 Muscles of the front of the leg and back of the foot. Ibid. 176 Superficial muscles on the back of the right leg. Ibid. 177 Deep muscles of the back of the leg. Ibid. 178 Muscles of the sole of the foot. Ibid. 179 Deep muscles of the sole. Ibid. 180 Diagram exibiting the relative position of the common anatomical ele- ments of serous and mucous membranes, the glands, the lungs, and the skin.* 181 Squamous epithelium.* 182 Pavement epithelium.* 183 Polyhedral epithelium.* 184 Diagram of a vertical section of mucous membrane of the small intes- tine.* 185 Diagram of a vertical section of the bronchial mucous membrane.* 186 Diagram of a section of the mucous membrane of the mouth.* 187 Diagram exhibiting the relation of a serous membrane, the pleura, to the organ it invests and the cavity it lines.* 188 Diagram of two simple tubular glands.* 189 Simple gland dilated into a pouch.* 190 Glands rendered slightly complex by division at bottom.* 191 Increase of complexity of glands.* 192 A tubular gland.* 193 Gland of complex form.* 194 Gland of complex form.* 195 Gland of complex character.* 196 A racemose gland.* 197 Unstriated muscular fibre.* 198 Vertical section of the face and neck, through the median line, antero- posteriorly, exposing to view the nose, mouth, pharynx and larynx. Sappey. 199 Section of a follicular gland from the root of the tongue. Kolliker. 200 Posterior view of the muscles of the palate and fauces. After Bonamy Sf Beau, Morton. 201 Yiew of the upper surface of the tongue. Sappey. 202 Diagram of the papillae of the tongue.* 203 Papillae of the tongue.* 204 Side view of the muscles of the tongue. After Bonamy $ Beau, Morton. 205 Upper and lower permanent teeth, exterior view. Schmidt. 206 Lateral views of same. Ibid. xx LIST OF ILLUSTRATIONS. FIG. 207 Temporary teeth of one side. Schmidt. 208 Vertical section of a molar tooth.* 209 Vertical section of the fang of a canine tooth.* 210 Section of dentine.* 211 Three enamel columns.* 212 Section of enamel.* 21 3 Diagram of the mode of development of the teeth. After Goodsir, Kolliker. 214 Posterior view of the muscles of the pharynx. Wilson. 215 Side view of the muscles of the pharynx. Ibid. 216 Cavity of the abdomen laid open, with the viscera retained in their relative position. Ibid. 217 Diagram of the reflections of the peritoneum in a vertical section of the abdomen.* 218 The stomach and intestines. Schmidt. 219 Wrinkled or rugous surface of the mucous membrane of the stomach. Sappey. 220 Mammillae of the mucous membrane of the stomach. Ibid. 221 Small portion of the mucous membrane of the stomach, with the imbedded gastric glands.* 222 A gastric gland.* 223 Small portion of the mucous membrane from the upper part of the jeju- num.* 224 Portion of mucous membrane from the ileum.* 225 Diagram of the structure of the mucous membrane of the ileum.* 226 Portion of the duodenum. Sappey. 227 A vertical section of the duodenum.* 228 Portion of the mucous membrane from the upper part of the ileum. Sappey. 229 Portion of the ileum. Ibid. 230 The caecum laid open, to expose the ileo-caecal valve. Morton. 231 Section of the mucous membrane of the colon.* 232 Inferior surface of the liver.* 233 Portion of the liver of the hog. After Kiernan, Kolliker. 234 Portion of the liver of the hog. Ibid. 235 Section of several lobules of the liver of the rabbit. Kolliker. 236 Polyhedral epithelium.* 237 Diagram representing the section of a lobule of the liver.* 238 Diagram representing a transverse section of one of the cords of the hepatic cell-net* 239 Transverse section of the walls of the aorta. Kolliker. 240 Elastic tissue from the middle coat of the popliteal artery. Ibid. 241 Unstriated muscular fibres from the middle coat of the arteries. Ibid. 242 Diagrams exhibiting the arrangement of the valves of veins. Morton. 243 A small artery magnified. Kolliker. 244 Red blood corpuscles.* 245 Front view of the heart. Quain Sf Sharpey. LIST OF ILLUSTRATIONS. xxi FIG. 246 Posterior or lower surface of the heart. Quain $ Sliarpley. 247 View of the heart, with the anterior portions of ihe ventricles removed. Schmidt. 248 Striated muscular tissue of the heart.* 249 The aorta. Bourgery. 250 Left common carotid dividing into the external and internal carotid arte- ries. Ibid. 251 The external carotid artery and its branches. Ibid. 252 Internal maxillary artery. Ibid. 253 Arteries of the interior of the cranium. Ibid. 254 View of the axillary artery. Schmidt. 255 View of the axillary and brachial artery. Ibid. 256 Arteries of the forearm. Bourgery. 257 Arteries of the hand ; palmar surface. Ibid. 258 The aorta. Ibid. 259 Distribution of the cceliac artery. Wilson. 260 Distribution of the superior mesenteric artery. Jamain. 261 Distribution of the inferior mesenteric artery. Ibid. 262 Yiew of the left side of the pelvis, the bladder, uterus, vagina, and rec- tum. Ibid. 263 Yiew of the perineum, exhibiting the distribution of the internal pudic artery. Bourgery. 264 Arteries of the front of the thigh. Jamain. 265 Arteries of the back of the thigh. Ibid. 266 Arteries of the front of the leg. Ibid. 267 Arteries of the back of the leg. Ibid. 268 Arteries of the sole of the foot. Ibid. 269 Yeins of the thorax and abdomen. Bourgery. 270 Yeins of the head and neck. Ibid. 271 Sinuses at the base of the cranium. Schmidt. 272 Vertical section of the skull. Ibid. 273 Superficial veins of the upper extremity. Ibid. 274 Yeins of the thorax and abdomen. Bourgery. 275 The portal system of veins. Quain fy SJiarpey. 276 Superficial veins of the back of the leg. Bourgery. 277 Superficial veins of the inner part of the lower extremity. Ibid. 278 Lymphatic capillary net-work of the skin of the ear. Sappey. 279 Yiew of the great lymphatic trunks. Bourgery. 280 Lymphatics of the head and neck. Ibid. 281 Cartilages of the larynx. Quain fy Sharpey. 282 Yiew of the vocal membrane.* 283 Muscles of the larynx.* 284 Vertical section of the face and neck, through the median line antero- posteriorly, exposing to view the nose, mouth, pharynx and larynx. Sappey. 285 Front of the larynx, trachea and bronchi, and back of the same. Rich- ardson. xxii LIST OF ILLUSTRATIONS. FIG. 286 The trachea, lungs and heart. Bourgery. 287 Diagram of the two primary lobules of the lungs.* 288 Portion of the thyroid body in section. Kolliker. 289 One lobe of the thymus body, with its cavity laid open, and exhibiting the lobular recesses. * Ibid. 290 Section of a lobule of the thymus body. Ibid. 291 Longitudinal section of a kidney.* 292 Diagram of the structure of the kidneys.* 293 Section of the cortical substance of a supra-renal body. Kolliker. 294 Cells from the supra-renal body. Ibid. 295 Testicle, with the vaginal tunic laid open. Quain $ SJiarpey. 296 Transverse section of the testicle. Kolliker. 297 Testicle, deprived of its tunics. After Arnold, Kolliker. 298 Portion of a seminiferous tubule. Kolliker. 299 Posterior view of the fundus of the bladder. Cruveilhier. 300 Spermatozoids. Kolliker. 301 Transverse section of the penis. After Weber, Morton. 302 Vertical section of the penis and bladder.* 303 Part of the bladder and penis, witfr the urethra laid open from above. Wilson. 304 Sketch of the uterus and its appendages. Ibid. 305 Section of the uterus antero-posteriorly, and section of the uterus from side to side.* 306 Transverse section of an ovary. Kolliker. 307 Human ovum. Ibid. 308 Two corpora lutea. Ibid. 309 Ovary, parovarium, and Fallopian tube of the left side.* 310 Section of female pelvis, from before backward. Schmidt. 311 External organs of generation.* 312 Side view of the male pelvis and its contents. Wilson. 313 View of the perineum. Bourgery. 314 Several small lobules of the mammary gland of a pregnant woman. After Langer, Kolliker. 315 Diagram, exhibiting the course of a lactiferous duct. After Cooper, Morton. 316 Corpuscles observed in milk. Kolliker. 317 Nerve fibres of the white substance of the cerebrum.* 318 Portion of gray substance, from the exterior of the cerebellum.* 319 Large nerve cells from the anterior horns of the gray substance of the spinal cord. Kolliker. 320 Transverse section of the small sciatic nerve. Ibid. 321 Mode of anastomosis and branching of nerves.* 322 Structure of nerve fibres.* 323 Pacinian corpuscles.* 324 Elements of the sympathetic system. Kolliker. 325 Nerve cells from the semilunar ganglion of the trigeminal nerve. Ibid. LIST OF ILLUSTRATIONS. xx jii FIG. 326 Base of the brain. After Hirsclifeld, Sappey. 327 Transverse section of the hemispheres of the cerebrum on a level with the corpus callosum.* 328 Section of the brain along the great longitudinal fissure. After Hirsch- feld, Sappey. 329 Transverse section of the cerebral hemispheres, the corpus callosum re- moved, and the lateral ventricles exposed.* 330 Striated bodies, thalami, quadrigeminal body, and cerebellum. After Hirsclifeld, Sappey. 331 Segment of the spinal cord.* 332 Oculo-motor and abducent nerve. After Hirschfeld, Sappey. 333 Trifacial nerve. Ibid. 334 Ophthalmic ganglion, the outer part of the right orbit removed. Ibid. 335 Superior maxillary nerve, the external wall of the left orbit and of the superior maxillary bone removed. Ibid. 336 View of the spheno-palatine ganglion, the outer wall of the left nasal cavity, and the olfactory nerve. Ibid. 337 Distribution of the inferior maxillary nerve. Ibid. 338 The facial nerve. Ibid. 339 The last four cerebral nerves, the facial nerve, the sympathetic, and the upper two cervical nerves. Ibid. 340 The pneumogastric nerve. Ibid. 341 The bracial plexus. Ibid. 342 Cutaneous nerves of the upper extremity. Ibid. 343 The same. Ibid. 344 External cutaneous, median, ulnar, and musculo-spiral nerves. Ibid. 345 The same. Ibid. 346 Cutaneous nerves of the front of the thigh. Ibid. 347 Lumbar plexus and its branches. Ibid. 348 External popliteal nerve and its branches. Ibid. 349 Popliteal nerves. Ibid. 350 Partition of the nose. Sappey. 351 Cartilages of the nose. Ibid. 352 Outer wall of the left nasal cavity. Ibid. 353 Nerves of the partition of the nose. Ibid. 354 The left eyelid and lachrymal gland, turned forward and inward so as to see their inner surface. Ibid. 355 The left eye, with a portion of the eyelids removed, to exhibit the lachry- mal canals and sac. Ibid. 356 Muscles of the eye. Morton. 357 Vertical section antero-posteriorly of the eyeball. Sappey. 358 The choroidea and iris. Ibid. 359 Veins of the choroidea and iris. Ibid. 360 View from behind of the anterior part of the eyeball. Ibid. 361 The same view, with the crystalline lens and retina removed. Ibid. 362 Segment of the choroidea and iris, seen on its inner surface. Ibid. xxiv LIST OF ILLUSTRATIONS. FIG. 363 Arteries of the iris. Sappey. 364 The eyeball, with the sclerotica, cornea, choroidea, and iris removed. Ibid. 365 Retina, seen on its posterior inner surface. Ibid. 366 The crystalline lens. Ibid. 367 Crystalline lens, breaking up into segments. Ibid. 368 Segment of the crystalline lens. Ibid. 369 The auricle. Ibid. 370 General view of the ear, right side, laid open from the front. Ibid. 371 Cavity of the tympanum and mastoid sinuses. Ibid. 372 Small bones of the ear. Ibid. 373 The internal ear, consisting of the labyrinth and internal auditory meatus, laid open. Ibid. 374 Internal ear laid open. Ibid. 375 Nerves of the vestibule and semicircular canals. Ibid. 376 The cochlea, laid open, its summit turned upward. Ibid. 377 The cochlea, laid open, and viewed from its summit toward the base. Ibid. 378 Distribution of the cochlear nerve. Ibid- 379 Vertical section of the skin of the forefinger across two of the ridges of the surface.* 380 Scurf from the leg.* 381 Fragment of dandruff from the head.* 382 Sebaceous glands opening into the mouth of a hair follicle. Todd $ Bow- man. 383 A large sebaceous gland from the nose. Kolliker. 384 Sebaceous matter, from one of the sebaceous glands of the nose.* 385 Structure of the sebaceous glands. Kolliker. 386 Portion of the shaft of a light hair. Ibid. 387 Portion of a hair from the outer part of the thigh.* 388 Root of a hair lodged within its follicle. Kolliker. 389 Diagram of structure of the root of a hair within its follicle.* 390 Matrix of the nail. Sappey. 391 Under surface of the nail. Ibid. 392 Vertical section of the end of a finger. Ibid. AN ELEMENTARY TREATISE HUMAN ANATOMY CHAPTER I. INTRODUCTION. THE word Anat'omy means dissection ; but it has become to be ap- plied to the study of the physical structure of organized bodies. The word is variously modified, according to its application ; and thus we have vegetable anatomy, comparative anatomy, human anatomy, patho- logical anatomy, etc. Hu/man anat'omy, the special object of our attention, may be sub- divided into general, special, and topographical anatomy. Gen/eral anat'omy treats, in common, of the physical elements of struc- ture of the various organs of the body. It is frequently named Micro- scopic anatomy, from the necessity of employing the microscope in its study. The term Histology, from the Greek I^, a description, is also applied to it. Special or Descriptive anat'omy treats of the properties, such as form, color, size, and situation of the organs of the body arranged into sys- tems ; and thus we have the anatomy of the bones, of the muscles, etc. Topographical anat'omy treats of the relative position of organs in particular regions of the body. Thus, the topographical anatomy of the groin refers to all the organs in this region. It is also called Surgical anatomy, from its importance in surgery. In commencing with the study of human anatomy, the author thinks it not amiss in directing the student to take a cursory glance at the general structure, characteristic phenomena, and conditions of existence of living bodies, of which man constitutes the highest or most complex type. According to the present state of chemical knowledge, about sixty 2 (17) 18 INTRODUCTION. different kinds of matter, the so-called simple or ultimate elements, enter into the composition of the earth. The phrase " kinds of matter" is expressive of the idea of the ponderable agencies of nature which are not reducible to a simpler condition with all the aids of modern science, are incapable of conversion into one another, and are indestructible. All the material masses or bodies of the earth are divisible into two great groups mineral bodies and organized bodies. The former are known as minerals, and comprehend the rocks, stones, ores, soils, water, air, and gasses ; the latter are known as plants and animals, including all their parts. Mineral bodies, in contradistinction to organized bodies, are also called unorganized. They are homogeneous in structure ; and, under ordinary circumstances, either have no definite form, expressed by the term amorphous, or they are crystalline ; that is to say, they are of regular form, defined by plane surfaces and sharp angles. Under special circumstances, it is probable that all mineral bodies may assume a crys- talline form. Thus, water and mercury, ordinarily liquid, at lower tem- peratures become crystalline solids ; and even certain aeriform fluids, such as carbonic acid or nitrous oxide, under the combined influence of high pressure and intense cold, assume the condition of crystalline masses. Organized bodies are composed of a few simple physical elements, which may be arranged as follows : 1. Homogeneous liquid, and its transitions toward a solid condition. 2. Homogeneous granules. 3. Homogeneous filaments. 4. Homogeneous membrane. Every organized body originates in a homogeneous liquid, the most complex as well as the most simple ; and every one starts into definite existence as a homogeneous granule, invisible except with the aid of the microscope. The granule is the first appreciable step in the production of the seed of plants, and of the egg of animals. There are certain specific living beings, which, throughout their exist- ence, appear to consist of a simple granule ; as, for instance, the Monas crepusculum, represented in figure 1. This measures less than the 10,000th of an inch in CREPUSCCLUM. di ame ter, or is so minute that 500,000,000 may be Highly magnified. crowded in a drop of water, in which they are often observed endowed with the power of movement. Homogeneous filaments are the least frequent constituents of organized bodies. They constitute the vibrating appendages of certain microscopic INTRODUCTION. 19 plants, of many animalcules, of the so-called ciliated cells of more com- plex animals, and of the spermatozoids of the male seminal liquid. They also appear to form the structure of areolar tissue. Some of the simplest forms of specific organic life consist, apparently, of mere homogeneous filaments ; as, for instance, the various species of Yibrio, (figure 2,) millions of which, endowed with the power of movement, may be observed in any organic infusion that has been exposed for a short time to the air. The thin, oil-like, iridescent film, often seen on standing water, is sometimes composed of these living homogeneous filaments, which, decomposing the rays of light falling on them, give rise to the charac- teristic hues of the rainbow. Homogeneous membrane is an important solid ele- ment of organized structures, and is mostly the con- taining part when the other elements are in association with it. Organized bodies derive their materials of composition from the min- eral world, and they are subject to the control of the same laws which govern unorganized bodies. In the final dissolution of organized bodies, the material of composition again reverts to the mineral world. Though we cannot comprehend the idea of a beginning to matter, it is nevertheless conceivable that organized bodies may have had a definite commencement or origin in time. Be this as it may, the nature of the origin of organized bodies in time is involved in the deepest obscurity. If the view of many cosmogenists and geologists be adopted, that the earth was once in a highly heated or incandescent condition, it is obvious such a state would have been incompatible with the contemporaneous existence of organized bodies ; and it would follow, of necessity, that they were subsequently produced or introduced when the temperature of the earth was reduced to the condition favorable to the support of life. Philosophers have contended that the simplest forms of organized bodies may originate directly and spontaneously from the mineral world, under the operation of ordinary physical causes. Aside from the im- portant fact that it is never pretended that the more complex plants and animals spring into existence in this manner, no authentic evidence has yet been presented to us that microscopic organisms may originate spon- taneously ; but, on the contrary, all careful investigations and well-con- ducted experiments have so far tended to refute the hypothesis. Organized bodies have existed for incalculable ages, as is proved by the great quantity and variety of their remains, which extend through an enormous depth of the stratified rocks composing the surface of the earth. Perhaps a more remarkable fact, ascertained in the exploration 20 INTRODUCTION. of the latter, is, that the earliest series of organized bodies became ex- tinct to give place to a new series, which in like manner subsequently became extinct; and this process of the successive origin and extinction of races or series of species has continued without interruption down to the present period ; from which it is probably not unsafe to infer the ultimate fate of the existing race of living beings. For convenience in study and easy reference, organized bodies are arranged or classified in some system, which may vary according to our extent of knowledge of those bodies. Thus, we have kingdoms, classes, orders, families, genera, species, and varieties, each division exhibiting certain characters in common, by which its relative position is main- tained and readily perceived. How far these divisions accord with any apparent natural plan, is a subject of much controversy. The first grand division of organized bodies is into the vegetable and animal kingdom, or into plants and animals. This arrangement, how- ever obvious it may appear, is not without its difficulties ; for, although the higher types of both are readily distinguishable, it appears to be impossible, in the present condition of our knowledge, to indicate a positive separation between the lower types ; and hence we find natu- ralists classifying the simplest forms of organized bodies indiscrimi- nately as plants or animals. As regards the subdivisions of the vegetable and animal kingdoms, though there is, perhaps, rather more concurrence of opinion, yet the attempt to define positive lines of separation frequently results in failure. In accordance with the systematic labors of naturalists, who classify the material objects of nature, a species of organized body is one pos- sessing some character by which it may be distinguished from another ; and this character is constant, so far as the history of the species is known. Varieties are founded upon distinctive characters, which, as is known by their history, are temporary. A genus consists of a group of species possessing some structural characters in common ; and, in like manner, a group of genera approaching in character makes a family; and thus we may advance to the starting-point of classification into kingdoms. It has already been indicated that the matter of mineral or unorgan- ized bodies, and that of organized bodies, is the same. When, however, we speak of the material of the latter, it is called organic matter, in contradistinction to that of the former, which is called inorganic matter. In other words, so long as the material constitutes mineral or unorgan- ized bodies, it is inorganic matter ; but, the same material having entered into the constitution of plants and animals, or organized bodies, is then named organic matter. INTRODUCTION. 21 The derivation, directly or indirectly, of organized bodies from the inorganic world, is termed organization, and their reduction to the primi- tive condition, disorganization, or decomposition. Of the sixty ultimate elements of the earth, less than a third enter into the composition of organized bodies seventeen being the number usually detected. All the other elements of nature are unorganizable, or inca- pable of entering into the perfect constitution of plants and animals. Of the seventeen organizable elements, Ox'ygen, Hy'drogen, Car'bon, and Ni'trogen are so universally existent in plants and animals, that they are viewed as the necessary or essential elements of every organized body. Coincident with this highly important circumstance, the four ele- ments mentioned are the most widely diffused and abundant in nature. The remaining or incidental chemical elements of organized bodies, arranged in the order of their relative importance, or frequency and quantity, are as follow: Cal'cium, Potas'sium, So'dium, Chlo'rine, Phos'phorus, Sul'phur, Silicon, I'ron, Magnesium, Manganese', I'odine, Flu/orine, and Bro'mine. These are almost never found in a simple condition, but are in combination with oxygen, hydrogen, and carbon, and with one another. The ultimate elements by union constitute the proximate chemical elements of organized bodies, which are those entering immediately into the structure of the latter, and are obtained separately by the simplest methods of analysis. The proximate elements of organized bodies are numerous, and in many instances are imperfectly known. They may be divided into four groups, as follow : 1. Nitrogenized elements peculiarly organic, such as gluten and legumen in plants, and fibrin and albumen in animals. 2. Non-nitrogenized elements peculiarly organic, such as cellulose, starch, sugar, and fats. 3. Elements not peculiarly organic, as water, carbonic acid, and phosphate of lime. 4. Elements resulting from the disintegration of the former during the ordinary vital actions, and mostly found in the secretions and excretions, such as urea, and uric acid in animals. Through a variety of conditions the agency of disease, spontaneously under ordinary circumstances after death, or aided by artificial means the proximate principles are resolved into a vast number of new com- pounds, such as the ordinary fat acids, glycerin, gelatin, the alcohols, ethers, etc. etc. Every organized body, in its construction, exhibits a series of phe- nomena called those of life, or vital ; and hence, when an organized body presents such phenomena, it is said to live, or possess life or vitality which terms are expressive of the actions peculiar to, or ob- 22 INTRODUCTION. served only in association with, organic forms. Vital phenomena, or the display of the peculiar actions of organized bodies, require a con- stant supply of the elements of their structure in a liquid state, the influ- ence of the air, and a certain range of temperature. Without these conditions vital activity cannot be maintained ; and hence these condi- tions are viewed as essential to life. No one can be removed with- out a cessation of vital action often forever in some instances only while the condition is absent. Thus, a dried seed exhibits no vital activity, but may do so when the essential conditions are brought to play upon it. Every organized body must have lived during the period of its con- struction ; but it may be subsequently preserved without those actions which characterize life such a condition being distinguished as that of death. Thus, the timbers of our buildings and the clothes we wear were once living, but are now dead organized bodies. The phenomena which characterize life are as follow : the origin of the organized body from a parent ; its successive development and growth ; the processes of nutrition and assimilation ; the combustion of effete particles of structure ; and reproduction. The cessation of these phenomena constitutes death. All living bodies proceed from parents, whose remotest ancestry can- not now be traced. All of them commence in or start from the con- dition of a homogeneous liquid ; and the first defined step in organization is the appearance of a granule, whose form, beneath the highest powers of the microscope, appears to be spherical. The homogeneous liquid in which living bodies originate is the so-called nutritive matter. 1 It contains all the chemical elements of structure of the organized bodies in complete solution. In the development and constitution of organized bodies, we find the four ultimate physical elements, previously mentioned, very generally, more or less associated in the composition of a common characteristic structure named the organic cell. All organized bodies, except such as are of so simple a nature as to consist alone of isolated granules or fila- ments, are, for the most part, composed of organic cells and their trans- formations. The primitive form of the organic cell, as represented in figure 3, is that of a spherical vesicle with a filamentary appendage. In this condi- tion, however, the organic cell is not often observed, for generally the filamentary appendage is absent, and the spherical form of the vesicle is quickly modified after its development. The minute being, Trachelo- 1 Plasma; Blastema. INTRODUCTION 23 monas volvocina, (figure 4,) found in stagnant water, may be viewed as a specific organized body consisting of a single typical organic cell. The minute plant, Protococcus, (figure 5,) which coats damp walls and pave- FIG. 3. Fro. 4. TRACHELOMONAS VOLVOCINA, DIAGRAM OF A TYPICAL FROM STAGNANT WATER. ORGANIC CELL. Highly magnified. PROTOCOCCUS, FROM DAMP PAVE- MENTS, MULTIPLYING BY DIVI- ments, in shaded places, with a green cover- SIGN, i, a simple ceil; 2, the ing, consists of isolated organic cells without . < ~ *> the filamentary appendage. 4, a ceil dividing into two. The outer portion of the vesicle of the organic cell, or the cell wall, is homogeneous membrane. The cell con- tents may be liquid, semi-liquid, granular, or filamentous. Among the cell contents very generally there is observed a second and much smaller vesicle, called the nu/cleus, 1 which though liable to transformation is much less so than the containing cell The wall of the nucleus is also of homogeneous membrane, and its contents likewise liquid, semi-liquid, or granular. Occasionally organic cells are observed with several nuclei. Among the nuclear contents, almost always, a spherical granule, con- spicuous for its size, may be distinguished from the others, and this is technically called the nucle'olus. A ciliated epithelial cell, as seen in figure 6, from the mucous mem- brane of the nasal and bronchial passages, pre- sents an association of all the ultimate physical elements of organized bodies. Thus we have |H CILIATED EPITHELIAL homogeneous membrane in the cell wall and nu- CELL ' from the pul " fag mo nary mucous clear wall ; homogeneous granules and liquid in B membrane; exhibit- the cell contents ; and homogeneous filaments in ing the granular con- W tents, together with the vibrating appendages. the nucleus, and, at In plants, organic cells are generally developed the "?*** frce tremit y , the ' . /,-,... vibrating appendages or cilia. and multiplied through division and subdivision of the contents of pre-existing cells, which contents at the same time increase in bulk or grow through a constant supply of nutritive matter, The process is observed in the germination of seeds and the production of the stem, leaves, flowers, and fruit of plants. In the simplest of vege- 1 Cytoblast. 24 INTRODUCTION. FIG. 7. FIG. 8. tables, such as the Protococcus, as represented in figure 5, it is the mode of reproduction of the plant. This method of production and multiplication of organic cells is also observed in the course of develop- ment of the embryo from the egg. After the latter has been fecundated or exposed to the influence of the male spermatic liquid, the yolk divides into two spheres; these subdivide into four, and this process continues until the yolk is reduced to the condition of a mass of nucleated cells, as represente d in figure T. Another instance in which the multiplication of cells through division of the con- tents is strikingly observed > in the animal, is in the devel- opment of the cartilages. In the early condition of carti- lage, it consists of a homo- geneous matrix with isolated PROCESS OF MCLTIPL1CATIOJf nucleated Cells imbedded. TILAGE CELLS. 1, simple cartilage cell ,, ,, ,,. , , , ,. . from the embryo; 2, increase of car- ^ These multiply through divi- tilage cells by division of the prl . Sion and form groups Of niary cell; 3, 4, groups of cartilage . cells, from an adult articular carti- from a pair to twenty or l ' more, (figure 8,) as may be seen at any time in the permanent cartilages of the adult. Another mode of production of cells, with a con- tinual reproduction in the same manner, is observed in animals, in the formation and renovation of the epi- dermis and its appendages, the hairs and nails, of the YOLK IN THE HUMAN EGG. epithelium of mucous and serous membranes, and of i, a ripe ovum; 2, the th secret i ng ce n s O f glandular organs. In the deepest yolk divided into two; 3, yolk divided into part of these structures, in the nutritive liquid con- g^antlv exuding from the capillarv vessels, homogeneous J granules originate. These, which constitute nucleoli, successively become nuclei and organic cells in the following manner. A granule or nucleolus first appears ; and upon this a vesicular wall is developed, inclosing the nucleolus. In the liquid contents of the nucleus thus formed, granules may originate ; and a second vesicular wall is de- veloped, which incloses the nucleus and thus constitutes an organic cell. The contents of the latter, at first liquid, become more or less granular. The steps of the process just related are represented in figure 9. the four; 4, 5, the yoikdivid ed into numerous cells. INTRODUCTION. 25 FIG. FIG. 10. THREE SECRETING CELLS FROM THE SUB- MAXILLARY SALIVART GLAND. PROCESS OF DEVELOPMENT OF AN OR- GANIC CELL FROM A GRANULE. 1, a granule; 2, a vesicle developed upon the granule: the two constituting the nucleus and contained nucleolus; 3, the same, increased in size; 4,5, granules developed in the contained liquid of the nucleus; 6, the cell wall developed on the nucleus ; 7, 8, 9, suc- cessive increase of the cell, and de- velopment of granular contents. Subsequent to the development of organic cells, they most usually undergo more or less trans- formation in the produc- tion of the various parts of plants and animals. In some cases the modifica- tion is so slight that the original form remains man- ifest, as instanced, by the glandular cells generally, in animals. Thus in the figure 10, representing several secreting cells of the salivary glands, the typical organic cell form is readily recognized. In other in- stances the transformation of cells is so great that their existence would not be sus- pected from an examination alone of the structure produced from them. Thus the fibrous tissues, which consist of bundles of the finest homogeneous filaments, are the result of the subdivision or splitting of organic cells. Through continued reproduction, aggregation, and transformation of organic cells, the various textures or tissues are produced, which consti- tute the proximate physical elements of the various organs of animals. ULTIMATE CHEMICAL ELEMENTS OF THE HUMAN BODY. 1. Oxygen. 5. Chlorine. 9. Sodium. 12. Iron. 2. Hydrogen. 6. Phosphorus. 10. Potassium. 13. Fluorine. 3. Carbon. 7. Sulphur. 11. Magnesium. 14. Silicon. 4. Nitrogen. 8. Calcium. Ox'ygen, Hy'drogen, and Car'bon are found in all the tissues and liquids of the human body. Ni'trogen is likewise found in all except fat; Chlo'rine forms with hydrogen the chlorohydric acid of the gastric juice. It also exists in combination with sodium and potassium in most of the tissues and liquids of the body. Phos'phorus, or Sul'phur, or both together, exist in all the nitrogenized proximate elements of the body. Calcium, oxydized as lime, in the form of phosphate of lime, and in that of carbonate of lime, enters largely into the composition of the bones and teeth, and is also found in small quantities in some other parts of the body. So'dium and Potas'sium, as common salt or chloride of sodium, and as chloride of potassium, exist in most of the tissues and liquids. 26 INTRODUCTION. Magne'sium, as phosphate of magnesia, is found in the bones, and in small quantity elsewhere. I'ron exists in the coloring matter of the blood corpuscles. Flu/orine, in small quantity, as fluoride of calcium, is found in bones. Sil'icon, as silica, is found in hairs. ^ PROXIMATE CHEMICAL ELEMENTS OF THE HUMAN BODY. GROUP 1. NlTROGENIZED ELEMENTS PECULIARLY ORGANIC. Fibrin. Collagen. Crystallin. Pancreatin. Albumen. Chondrigen. Keratin. Pepsin. Albuminose. Elasticin. Haematin. Mucosin. Casein. Neurin ? Ptyalin. Melanin. Musculin. Globulin. Many of the elements belonging to this group are those which are least known. Thus the character of the albumenoid matter (Neurin) of the nervous system has not been ascertained, nor are we familiar with the important proximate constituents of the liver, kidneys, salivary glands, and some other organs. They all contain oxygen, hydrogen, carbon, and nitrogen ; most of them sulphur ; and many of them phosphorus. Fi'brin exists in the blood and lymph in a liquid condition. Its most striking peculiarity is its spontaneous coagulation on being removed from the circulation. Albu/men is found in the blood, lymph, and fluids of the serous cavities in a liquid condition. It coagulates above a temperature of 160 Fahr.; also through the agency of alcohol, tannin, the mineral acids, and the metallic salts. Albu/minose is found in the blood and chyle in a liquid condition. It results from digestion, in the alimentary canal, of the albuminous, fibrinous, and caseous matters of food, and from flesh ; and it differs from albumen in not being coagulable by heat. Ca'sein is the most important constituent of milk, in which it exists in the fluid condition. It coagulates through the agency of acids, but not through heat, nor spontaneously. The curdling of milk is due to the development of lactic acid from the sugar of milk. Mus'culin is the soft substance of flesh or muscles, endowed during life with the power of contractility. It is soluble in dilute muriatic acid ; boiling in water renders it more solid. Col'lagen is the principal constituent of the so-called bone cartilage, ligaments, tendons, fibrous membranes, the dermis, and the areolar tissue. By boiling in water it is resolved into gelatin or glue. Chon'drigen is the basis of the true cartilages and of the cornea. Long INTRODUCTION. 27 boiling resolves it into chondrin, which differs from gelatin in being pre- cipitated from solution by acetic acid and some other agents not acting on the latter. Elas'ticin is the peculiar solid material of the elastic tissue. It is remarkably insoluble in all ordinary menstrua. Neu/riii? is the supposed albumenoid principle of the nervous system. GloVulin forms with haematin the contents of the red blood corpuscles. Crys'tallin is the basis of the crystalline lens of the eye. It is coagu- lable by heat and by alcohol ; but unlike albumen, is precipitated from solution' by carbonic acid. Ker'atin is the principle which gives the horn-like character to the epidermis, nails, and hairs. Haem/atin is the coloring matter of the red blood corpuscles. Pty'alin is found in the salivary glands and the saliva. Pancrea'tin exists in the pancreas and its secretion. Pep'sin is a peculiar principle of the gastric mucous membrane and gastric juice. Mu/cosin is the viscid matter of mucus and the mucous epithelial mem- branes. Mela'nin is the dark coloring matter of the choroid tunic of the eye and of the skin of the negro. GROUP 2. NON-NlTROGENIZED ELEMENTS PECULIARLY ORGANIC. Olein. Stearin. Glycogen. Lactin. Margarin. Butyrin. Glucose. Inosit. All of these have for their ultimate elements oxygen, hydrogen, and carbon. O'lein, Mar'garin, and Ste'arin, mingled together, form the greater part of the fats of the human body margarin being the most abundant, and stearin the least so. Olein remains liquid even below the freezing point ; and at the ordinary temperature of the body it retains the other fatty matters in solution. Margarin, isolated, becomes a crystalline solid, below 118 Fahr. ; and stearin assumes the same condition below 143 Fahr. With alkaline solutions, the three fatty substances men- tioned undergo decomposition, evolving oleic, margaric, and stearic acids, which combine with the alkaline base, as in the ordinary forma- tion of soaps. The original fat base, in combination with water, consti- tutes the peculiar sweet liquid, glycerin. Bu'tyrin, in combination with margarin and stearin, forms the fatty part of cream or milk. Glyc'ogen is a peculiar substance in the tissue of the liver, which undergoes transformation into glucose. 28 INTRODUCTION. Glu'cose, commonly known as grape sugar, is found in the liver and the blood of the hepatic vein, and in less quantity in other blood. Lac'tin, or sugar of milk, is developed in the mammary gland, and may be obtained from the whey of milk, in a crystalline condition. The souring of the latter liquid arises from the conversion of its sugar into lactic acid. In'osit is a saccharine substance, incapable of vinous fermentation, found in the muscular structure of the heart. GROUP 3. ELEMENTS NOT PECULIARLY ORGANIC. Water. Phosphate of soda. Carbonate of potassa. Chloride of sodium. Phosphate of potassa. Fluoride of calcium. Chloride of potassium. Carbonate of lime. Silica. Phosphate of lime. Carbonate of soda. Chloro-hydric acid. Phosphate of magnesia. Water is one of the most important proximate principles of the human and all other organized bodies. It is the vehicle through which all the other proximate elements, with perhaps the exception of a portion of the fatty matters, are rendered capable of entering into the composition of the body. The amount of water in the different parts of the latter varies. In blood it is equal to 795 parts in the thousand; in muscles about 750 parts ; and in bones about 130 parts. The entire body con- sists of more than two-thirds its weight of water. Chlo'ride of So'dium and of Potas'sium, and more especially the former, are contained in solution in most of the liquids of the animal body. Phos'phate of Lime, of Magne'sia, of So'da, and of Potas'sa are found in solution in most of the animal liquids. The first of these elements is the chief material to which the hardness of the bones is due. Car'bonate of Lime, of Soda, and of Potassa are found in compara- tively small quantity in the human body the first chiefly in the bones, the latter two in most of the tissues. Flu'oride of Cal'cium and Sil'ica also exist, in small quantity, in the body the former in bones, the latter in hairs. Chlo'ro-hy'dric Acid exists in the gastric juice. GROUP 4. ELEMENTS ARISING FROM THE DISINTEGRATION OF THE DIFFERENT PARTS OF THE BODY, FOR THE MOST PART EXPELLED IN THE EXCRETIONS. Urea. Taurocholate of soda. Butyric acid. Creatin. Urates of soda, potassa, Formic acid. Creatinin. and ammonia. Acetic acid. Biliverdin. Cholesterine. Oxalate of lime. Uroerythrin. Lactic acid. Carbonic acid. INTRODUCTION. 29 TTre'a, with a composition of carbon, hydrogen, oxygen, and nitrogen, is the most important constituent of the urine forming, as it does, about three-fourths of the solid matter left after the evaporation of the water. It crystallizes in the form of four-sided prisms. In small quantity, it is found in the blood and the humors of the eye, and is considered to be derived from the disintegration of the nitrogenized tissues. Cre'atin and Crea'tinin, containing the same ultimate elements as the preceding, are two crystallizable principles found in the muscles, from which they appear to be given up to the blood, to be excreted in the urine. Biliverd'in and TJroer/ythrin are coloring matters the former of the bile, the latter of the urine. Both have the four ultimate elements carbon, oxygen, hydrogen, nitrogen entering into their composition. Taurochol'ate of Soda, consisting of taurocholic acid, containing the same elements as the former substances, in combination with soda, is an important ingredient of the bile. The TJ'rates of Soda, Potassa, and Ammonia, consisting of uric acid, with the same elements as the preceding, in combination with the alka- line bases, are found in the urine. Chol'esterine is a crystallizable, fatty substance, with a composition of carbon, hydrogen, and oxygen, but is unsaponifiable. It is found in the juices of the nerve-centres and the blood, and is excreted in the bile. Lac'tie Acid, with a composition of carbon, hydrogen, and oxygen, is found in the muscles and gastric juice. Butyr'ic, Ace'tic, and Form'ic Acids, containing the ultimate elements, carbon, hydrogen, oxygen, are obtained from the juice of the muscles, and are excreted in the sweat. Ox'alate of Lime is found in small quantity in the urine. Carbon/ic Acid is found in the blood and other liquids of the body. ULTIMATE PHYSICAL ELEMENTS OF THE HUMAN BODY. 1. Homogeneous liquid and its transitions to a solid condition. 2. Homogeneous granules. 3. Homogeneous filaments. 4. Homogeneous membrane. Homoge'neous liquid is observed in the fluids of the body, varying in consistence in different cases, as instanced by the liquor of the blood and lymph, serum, mucus, and the juices of the tissues. Homoge'neous gran'ules form an important constituent of many tis- sues, as in the contents of the secreting cells of glands, and epithelial cells, and in the ash-colored portion of the nervous system. 30 INTRODUCTION. Homoge'neous fil'aments form the principal constituent of the true fibrous tissues, and the vibrating appendages of ciliated epithelial cells. Hbmoge'neous mem/brane constitutes the basement membrane of the serous and mucous membranes, and glands. It also forms the wall of capillary vessels, the sheath of muscular and nerve fibres, and the parietes of organic cells. The human body has its origin in the ovary of the mother, and starts into definite existence as a homogeneous granule, which, in course of development, becomes an organic cell. This constitutes the primitive ovum ; which, after escaping from the ovary, traverses the oviduct, to be received into the uterus. Being subjected to the influence of the sper- matic liquid of the male, its contents undergo a series of segmentations, resulting in the production of a mass of organic cells, inclosed within the parent cell. Continually imbibing nourishment from the exterior, the ovum gradually increases in size, and step by step the embryo is evolved, the development of all its parts being preceded by the production of organic cells, through division of previously existing cells. It thus fol- lows, that all the organs and tissues of the human body and this will equally well apply to all organized bodies, except the simplest forms before mentioned are derived from organic cells. The degree of transformation of organic cells, in the production of the fully-developed tissues of the human body, varies from a condition of no perceptible change in the typical form, through a gradation of condi- tions, to such as lose all trace of the original cell-form. In the lymph corpuscles (figure 11) and the simple ganglionary cells, we have an instance of organic cells retaining, throughout their existence, the original form. In the medullary cells of the spongy part of bones, the adipose cells, and the secreting cells of many glands, the A LYMPH COR- original cell-form is simply modified, by mutual pressure, so as to assume a polyhedral appearance. In the epithelium of serous membranes, the original cell-form is modi- fied by its not only assuming the polyhedral outline, but from the breadth transcending the thickness, as represented in figure 12. In the epidermis, and the epithelium of, the mouth, the organic cells, which continually orig- inate in the deep parts of these structures, as EPITHELIAL CELLS OF A SEROUS they rise toward the free surface, assume the form MKMBRANE viewed on the of broad gcal ag represented by the diagrams broad surface; o, viewed in the * thickness. m figure 13. INTRODUCTION. 31 In the epithelium of the stomach and intestines, the organic cells, which originate as in the former instance, assume the form of prismatic columns, as represented in figure 14, a. FIG. 13. MODE OF DEVELOP- MENT, FROM BELOW UP- WARD, OF THE COLUM- NAR EPITHELIAL CELLS. a, epithelial cell of the stomach and in- testines; 6, epithelial cell of the pulmonary mucous membrane. In the epithelium of the air- passages, the organic cells un- dergo the same changes as in the case just mentioned ; but, in addition, have developed, upon their free extremities, vibrating appendages, as represented in figure 14,6. In the formation of the unstriated muscular fibres, the organic cells become elongated into fusiform bands, as represented in figure 15, a-c. EXHIBITS THE PROGRESSIVE DEVELOPMENT, FROM BELOW UPWARD, OF THE SCALES OF THE EPIDERMIS, or the scale-like epithelium of the mouth, a, the thickness; b, the breadth. FIG. 17. FIG. 15. FIG. 16. MODE OF DEVELOPMENT OF UNSTRIATED MUSCULAR FIBRE, a, b, c, cells success- ively elongating into a fusiform fibre. NERVE CELL, from the ash-colored mat- ter of the cerebrum. MODE OF DEVELOPMENT OF CAPILLARY VESSELS FROM CELLS, a, cell with four prolongations; b, vessels formed from the conjunction of the prolongations of cells. The nuclei remain adhering to the structureless walls of the vessels. The caudated nerve cells are produced by the organic cells sending off a number of processes, as represented in figure 16. In the formation of capillary vessels, organic cells protrude append- ages, which unite with one another, and thus form an intercommunicating system of tubes, as represented by the diagram, figure IT. In the development of the seriated muscular fibres, cells arrange them- selves in rows, and become united into continuous columns, as repre- sented in figure 18, a-d. 32 INTRODUCTION. FIG. 19. In the formation of the fibrous tissues, constituting the ligaments, ten- dons, the dermis, and areolar tissue,^ organic cells split up into bundles of fine filaments, as represented in figure 19, a-/ FIG. 18. A DEVELOPMENT OF STRIATED MUSCULAR FIBRE, FROM CELLS, a, simple cell ; 6, a pair of cells fused to- gether ; c, three cells fused, and their contents as- suming the striated character ; d, a muscular fibre, exhibiting its original composition of cells. DEVELOPMENT OF FIBROUS TISSUE, a, simple cell; 6, the same elongated ; c, d, e, the same becoming successively more and more divided ; /, the same split into a bundle of filaments, among which the nucleus remains. THE PROXIMATE PHYSICAL ELEMENTS OR TISSUES OF THE HUMAN BODY. 1. Tissue of free cells floating in a liquid. Blood corpuscles, with the contain- ing liquor. Lymph corpuscles, with the con- taining liquor. 2. Tissue of cells arranged in layers usually on free surfaces. Epidermis, nails, and cuticle of hairs. Epithelium of serous and mucous membranes. Glandular cells. Pigment cells. Nerve cells of retina and labyrinth. Enamel. 3. Tissue of cells aggregated in masses. Adipose tissue. Medullary tissue of spongy bones. Medulla of hairs. Ash-colored nerve tissue. Closed gland tissue. 4. Tissue of cells imbedded in a solid non-cellular substance. Cartilage. Bone. 5. Tissue of cells forming fusiform bands. Unstriated muscular fibres. Cortical portion of hairs. 6. Tissue of cells metamorphosed into tubes with liquid, semi- liquid, or solid contents. Capillaries. Nerve fibres. Striated muscular fibres. Crystalline fibres. Dentine. 7. Tissue of cells completely meta- morphosed into filaments. Fibrous tissue. Elastic tissue. CHAPTER II. THE SKELETON. THE Skeleton is the frame-work of the body, and is composed of an articulated assemblage of hard organs, the bones. It serves to preserve the shape of the body ; forms cases for the protection of the most important viscera ; and gives attachment to muscles and forms levers of movement. For convenience of description and study it is usually considered in parts corresponding with the ordinary divisions of the body ; as the head, trunk, and the upper and lower extremities. The number of distinct pieces or bones composing the skeleton varies at different periods of life. Some remain distinct from the first moment of their development, such generally being of the simplest form, as the bones of the carpus, the parietal bone, and the patella. Others, which are viewed as single bones in the adult, not only consist of several pieces in the beginning, but in the progress of develop- ment have other pieces 'successively added, as in the case of the vertebrae and the thigh-bones. Again, bones considered as distinct pieces when the body has arrived at maturity, at a later period may become united with those which are contiguous, as in the co-ossification of the cranial bones. The number of bones to which we usually refer in the description of the skeleton is as follows : For the head ; including the hyoid bone and excluding the teeth and the small bones of the ear 23 For the trunk; counting the coccyx as four, the sternum as three, and including the hip-bones 59 For the upper extremities; including the sesamoid bones, thirty-four to each extremity .68 For the lower extremities ; thirty-two to each ...... 64 214 The bones are connected together, in the construction of the skeleton, by various means, viz. : by cartilages, fibro-cartilages, and ligaments. 3 (33) 34 THE SKELETON. The connections are named the joints or articulations, and the parts of the bones involved are called the artic'ular extremities, borders, or surfaces, as the case may be. The bones of the two sides of the skeleton are either in pairs, as the ribs and those of the extremities, or they are single and symmetrical ; that is, they consist of two similar halves, as the vertebra. They vary much in relative proportion and form, and in these respects are divisible into four classes : the long bones, such as the principal ones of the limbs ; the tabular bones, 1 as those of the vault of the cranium ; the irregular bones, as the vertebras ; and the short bones, 2 as those of the wrist. The long bones have a more or less cylindroid or prismoid shaft or body ; which latter term is also applied to the massive part of irregular bones. The extremities of a long bone are dilated, and support smooth articular surfaces. From their respective position in relation with the vertebral column, that which is nearer to the latter is called the proximal extremity, and the more distant, the distal extremity. If an extremity forms a single rounded prominence it is called a head ; but if there are such a pair of prominences, they are called con'dyles ; though this name is also applied to the single articular eminences of the occipital bone and the lower jaw, and even to the tubercles on each side of the distal end of the humerus. The narrow or constricted portion intervening between a head, condyles, or other articular eminence, and the principal part of a bone, is called the neck. Any elevation or prominence may be termed a proc'ess. 3 If this be narrow and tapering it is usually named a spi'nous process, though the term is frequently applied to an obtuse prominence, which is also called a tu'bercle, or a tuberos'ity. An eminence supporting an articular surface is termed an artic'ular proc'ess An elevation extending some distance along the surface of a bone, or a prominent border, is named a line, ridge, or crest. An aperture in a bone or between several bones is called a fora'men, (plural : fora'mina,) and if this is prolonged for some distance it becomes a canal, or mea'tus. A broad shallow depression is termed a fos'sa, (plural : fos'sae,) and a cavity with a small external communication is a si'nus. Bones in the fresh condition are white, with a faintly bluish translu- cency, tinged with pink from the blood with which they are supplied ; and they are more pink or red the younger they are, from their greater degree of vascularity. When cleansed of their softer attachments by boiling or maceration, and dried, they lose in weight and become dull yellowish 1 Synonym : Broad bones. 2 Thick, or massive bones. 3 Apophysis. THE SKELETON. 35 white ; and if exposed to the combined influence of the air, moisture, and light, they acquire a more or less chalk-white appearance. They are hard, tough, and moderately elastic, which qualities vary with their age ; being tougher and more elastic the younger they are, and harder and more brittle the older they are. Human bones are nearly twice as heavy as water, their specific gravity being T92. Their chemical composition at mature age, according to recent analyses, is as follows : Bone-cartilage and blood-vessels 32'56 Phosphate of lime 53-61 Carbonate of lime 9*41 Phosphate of magnesia, fluoride of calcium, chloride of sodium, soda, oxides of iron and manganese, traces of silex, and loss . . . 4-42 100-00 Prom this table it will be perceived that about one-third of peculiar animal matters and two-thirds of ordinary mineral matters enter into the composition of bones. The relative proportion of the different matters, however, varies with age. The skeleton commences in the em- bryo in a cartilaginous condition ; the mineral matters are subsequently added in the course of development, and they increase in relative quan- tity with the advance of age. In the infant the different matters exist in the proportion of about half and half; from old bones as much as seven-eighths of mineral matters have been obtained. To the peculiar animal matters, bones owe their tenacity and elasticity; to the mineral matters, their hardness and rigidity. These qualities vary in degree with age, in accordance with the difference in relative propor- tion of the two kinds of matters. Hence the great predominance of mineral matters in the bones of old persons is one of the reasons why they are so much more liable to fracture than in young persons. When bones are burned, from the charring of their cartilage they become black and brittle ; in this condition constituting the bone-black of the arts. If the bone cartilage is entirely consumed, the mineral matters remain, still preserving the original form of the bones, which have now become pure white and exceedingly friable. From such calcined bones the phosphorus of commerce is obtained. When bones are steeped in diluted hydrochloric acid, most of the mineral matters are dissolved out, and the cartilage is left as a tough, flexible, gristle-like substance, retaining the original form of the bones. This bone cartilage, by boiling, is reduced into the condition of gelatin. When bones are boiled under high pressure, the gelatin is extracted; and it has been obtained in this manner for the making of jellies and 36 THE SKELETON. soups. Dogs, wolves, cats, and other carnivorous animals eat bones, from which the gastro-intestinal liquids thoroughly extract the gelatin, while the mineral matters are expelled as excrement. 1 The surface of bones, closely examined, exhibits a more or less distinctly fibrous appearance ; and it is perforated with numerous minute foramina for the transmission of blood-vessels. The articular surfaces present an even or close structure, and in the recent condition are covered with plates of cartilage. The extremities of long bones and the bodies of irregular bones present numerous comparatively large foramina, which transmit blood-vessels, chiefly veins. The bones are composed of an exterior more compact layer, and an interior looser arrangement of the same structure ; the two being distin- guished as the compact and spongy substances. In the long bones the compact substance forms the wall of the hollow shaft, and gradually diminishes to a thin layer investing the extremities. The spongy substance forms the great bulk of the latter, and gradually diminishes in the interior toward the middle of the shaft. The large hollow occupying the interior of the shaft of the long bones of the limbs is the med'ullary cavity, It is filled with a soft, yellow fat, the marrow or medulla. At the sides, and especially at the ends, of the medullary cavity, a portion of spongy substance is found, consisting of a delicate network of fibres, 2 which appears to be serviceable in sustaining the position of the mass of marrow and supporting the blood-vessels that supply the latter. The medullary cavity communicates with the exterior by means of one or more long, oblique canals, which pierce its wall from near the middle of the shaft, and accommodate the principal medullary nutritious blood- vessels. The areolae or interspaces of the spongy substance are occupied by a red, semi-solid marrow, resembling in chemical composition the extract of beef. In the foetus the medullary cavity does not exist, but is gradually formed through a solution or removal of spongy substance occupying the axis of the bone. It gradually increases in size with the advance of age ; and in its progress successive layers of compact substance become spongy substance, which in turn becomes looser in structure, and is finally removed. 1 This fact it appears is not sufficiently estimated in the question whether gelatin is nutritious or not. 2 Cancellated or reticulated substance. THE SKELETON. 37 FIG. 20. The broad bones are composed of an exterior moderately thick layer of compact substance, with an intervening layer of spongy substance. 1 The bodies of irregular bones, and the short bones, are composed of a mass of spongy substance enveloped with a comparatively thin layer of compact substance. The spongy substance of bones generally is pervaded by irregular canals for the accommodation of veins. They are especially conspicuous in the bones of the cranial vault. 2 All the foramina of the surfaces of bones, canals, and areola3 of the spongy substance and medullary cavities, where they exist, freely inter- communicate ; so that if mercury be poured in at one extremity of a long bone deprived of its marrow, it may be observed to stream from the foramina at the other extremity. The compact substance is relatively thickest or most abundant where bones are most slender or thin, in positions in which they are required to give the strongest support or offer the greatest degree of resistance to muscular action, and in parts of the body most exposed to injury from external violence. The introduction of the spongy substance into bones increases their bulk to a convenient size without a proportionate increase in weight ; and the extension of surface pro- duced by its presence where they articulate, very much reduces the liability of their displacement or dislocation. Further, the substitu- tion of the spongy for the compact substance, very much reduces the force of concussion from blows or falls. In animals whose recumbent position renders them little liable to the latter accidents, the bones contain a comparatively small quan- tity of spongy substance, as in the alligator. At first view it might be supposed that the spongy substance consisted of small plates and fibres of bone arranged without order, and even LONGITUDINAL SECTION OF THE PROXIMAL EXTREM- ITY OF THE FEMUR, exhibiting the arrangement of the spongy substance. 1, 2, positions in which the compact substance appears to resolve itself into a series of arches. 1 Diploe ; diploic structure. 2 Where they are named the diploic sinuses. THE SKELETON. FIG. 21. thrown into the utmost confusion. This is, however, not the case, as it always has the same general arrangement in the corresponding bones ; and this arrangement is of such a character that it contributes to give strength. Thus, if a longitudinal section be made of the proximal extremity of the femur, (figure 20,) it will be observed that, as the compact substance forming the walls of the shaft thins out, it appears to do so by sending off on each side successive arching plates, which, by crossing, not only mutually sustain one another, but also contribute to the support of the surfaces with which they are connected. In a transverse section of the condyles of the same bone, (figure 21,) it may be noticed that the exterior is formed of a layer of compact sub- stance, very little thicker than the numerous plates of the spongy sub- stance, which act as so many beams extending between the anterior and posterior surfaces. These antero- posterior plates are supported, at short distances, by cross-pieces ; and the whole is further strength- ened by numerous plates, radiating from a compact nucleus, situated at the bottom of the inter-condyloid notch. In a vertical section, antero-posteriorly, of the calcaneum, (figure 22,) the bone will be seen to be com- posed of a thin exterior layer of compact substance, with thickened nuclei at the position of support of the astragalus, and at its base. From the upper nucleus, plates of the spongy substance radiate in all directions ; and these are crossed by arching plates, proceeding from the nucleus at the base of the bone. A vertical section, antero-poste- riorly, of a vertebra, exhibits the body composed of an exterior thin layer of compact substance, with the spongy substance composed of ver- tical and transverse columns, mutually supporting one another and the surfaces of the bone. The spinous process, which performs the part of a HORIZONTAL SECTION OF THE CONDYLES OF THE FE- MUR, exhibiting the arrangement of the spongy substance. FIG. 22. VERTICAL SECTION, ANTERO-POSTERIORLY, OF THE CALCANEUM, exhibiting the arrangement of the spongy substance. 1, nucleus of compact sub- stance below the articulation of the astragalus, from whence start off numerous radiating fibres; 2, nucleus of compact substance, sending off nu- merous arching fibres. THE SKELETON. 39 lever for muscular action, is composed of a thick layer of compact sub- stance, with a very small proportion of strong spongy substance. The section of one of the tabular bones of the cranial vault presents two moderately thick plates of compact substance, mutually supported by intervening columns of spongy substance, with lateral offsets. The examples thus given are amply sufficient to prove that the spongy substance possesses an admirable mechanical arrangement, adapted to contribute strength to the bones of which it forms a part. The hollow, columnar condition of the shaft of the long bones of the limbs gives several advantages over a solid rod containing the same amount of material. Besides the increase of surface for muscular attach- ment, an increase of strength is obtained ; as it is well known, in the mechanic arts, that a hollow column is much stronger, or capable of sus- taining a much greater weight, than a solid column containing the same amount of material ; and hence it is that metallic columns of support are made hollow. Another familiar application of this principle in nature is exhibited in the construction of the culm or stem of most grasses so admirably adapted to the support of their treasures of grain, while they are yet so light as to bend beneath the gentlest breeze. The exterior of bones, except at the articular surfaces, is everywhere invested with a fibrous membrane, called perios'teum, which serves as a nidus for the blood-vessels entering the numerous foramina of bones, while it affords a medium of attachment for muscles and other organs. From young bones, this membrane may be readily separated by dissection ; but in the progress of age it becomes most intimately blended with the sur- face of the bones. The delicate vascular network, strengthened by a few filaments of fibrous tissue, lining the areolaB of the spongy substance and the medullary cavity, is called endos'teum. The marrow, or medulla, is of two kinds that which fills the hollow shaft or medullary cavity of the long bones of the limbs, and that which fills the areolaB or interspaces of the spongy substance generally. The former is a soft, yellow fat, consisting of delicate adipose cells ; the latter is a red, pulpy matter, which, in chemical composition, resembles the ex- tract obtained in boiling meat. It also contains fat, which increases in quantity with the advance of age. Examined with the microscope, it is found to consist of nucleated cells. The bones are pervaded by blood-vessels, which communicate with those of the periosteum and endosteum. The general course of these nutritious vessels corresponds with the fibrous arrangement more or less distinctly observable on the surface of bones ; and hence it is, for the most part, longitudinal in the shaft of long bones. 40 THE SKELETON. The osseous tissue is arranged in concentric layers around the course of the vascular canals 1 of the bones ; so that if a transverse section of the shaft of a long bone be made of sufficient thinness to transmit light, and be viewed with the micro- scope, it will be observed to be perforated with circular and oval orifices of the divided vascular ca- nals, surrounded by rings of osseous tissue, as represented in figure 23. In a longitudinal section the vas- cular canals are seen generally pur- suing the same direction, inclosed on each side with plates of osseous tissue. In very many instances, in the transverse section of a bone, it may be observed that the outer lamina of a series of ossific plates sur- rounding the vascular canals are more or less interrupted, in their course, by the encroachment of con- tiguous laminae belonging to neigh- boring canals, apparently the result of absorption, from pressure, more or less mutual and outward, from the vascular canals. In young and growing bones, in accordance with their greater de- gree of vascularity, the vascular canals are more numerous than in older ones. The surrounding osseous lamina? are, however, less numerous; and these appear to increase in number with the development and growth of bones. At the surface of bones, in transverse sections, parallel layers of osseous tissue, more or less interrupted, are observable, which are those last deposited by, or formed from, the periosteum. The fibres and plates of the spongy substance are composed of lamina) of osseous tissue, which appear to be the remains of concentric series of laminaB that once surrounded vascular canals but now form walls to the areolae containing marrow. TRANSVERSE SECTION OF THE SHAFT OF A PHA- LANX, moderately magnified. The upper part of the figure corresponds with the exterior surface of the bone; the lower part with the interior spongy substance. 1 Canals of Havers; Haversian canals. THE SKELETON. 41 Fio. 24. In and between the laminae of osseous tissue, as seen in figure 24, there exist numerous minute lenticular excavations, called lacu/nae, 1 from which diverge a multi- tude of exceedingly fine branching tubes or can- alic'uli, perforating the osseous laminas, and free- ly communicating with one another and with the vascular canals. By means of this arrange- ment a free intercommu- nication is established for the conveyance of nu- tritive matter through- out the osseous structure. The lacunaB and canal- iculi, when viewed in a section of bone by trans- mitted light, appear as black fusiform Spots with TRANSVERSE SECTION OF BONE FROM THE SHAFT OF THE FEMUR, -. . highly magnified. The large circular orifices are transverse sections numerous minute divei'g- of the vascular canalgj 8urrounded by conc entric layers of osseous illg black lines. By re- substance. Between the latter are seen the lenticular excavations fleeted light they appear F laCUnS5 int ~- icatin S by means of canaliculi. opaque white upon a more translucent ossific matrix. The osseous laminae, when isolated and highly magnified, exhibit a FIG. 25. FIG. 26. AN OSSEOUS LACUNA, exhib- iting its numerous diverging canaliculi; highly magnified. faintly longitudinal retic- ular arrangement, as if they were composed of an intertexture of filaments; and indeed when the car- tilage of bone is mace- rated in diluted muriatic acid, it is resolved into a mass of the finest cotton- like filaments. In positions where bones or parts of them are very thin, as in the lachrymal bYe~buu>ne oniyln focus. THIN PLATE FROM THE ETHMOID BONE, without pre- paration ; highly magnified. Two planes of lacuna? visi- Corpuscles of Purkinje. 42 THE SKELETON. bone, the edge of the squamous portion of the temporal bone, and the thin plates of the ethmoidal sinuses, (figure 26,) they are composed of parallel osseous lamina, with intervening lacunae, which communicate by means of their canaliculi with the exterior surfaces covered with perios- teum, from the vessels of which they imbibe nutritive matter. DEVELOPMENT AND GROWTH OF THE SKELETON. FIG. 27. The skeleton at its earliest period is perceptible as a soft cell structure, which soon assumes the more consistent char- acter and composition of cartilage. Ossi- fication, or the deposit of the calcareous matters, commences as early as the sixth or seventh week of embryonic life. The process occurs from one or more points for each bone, which are called the centres of ossification. 1 Bones of simple form generally have but a single centre of ossification, as the parietal and the carpal bones. The others are developed from a number of centres, in most cases holding a relationship with their degree of complexity. Ossification begins in the principal part of a bone, which is thence called the diaph/ysis. 2 The accessory portions, subsequently ossifying more or less in succession, are called epiph/yses, Thus, for example, (figure 2t,) the shaft or diaphysis of the thigh-bone first begins to ossify, then follow in succession, as epiphyses, the con- dyles, the head, the great trochanter, and finally the small trochanter. In a vertebra, (figures 28, 29,) three diaph- yses simultaneously undergo ossification; that is to say, the body and each half of the arch. Then follow the epiphyses together of the spinous and transverse processes; and lastly a thin plate of bone is added to the upper and lower surface of the body. Epiphyses are united with their diaphysis by continuous cartilaginous FEMUR, from an individual about sixteen years of age. exhibiting the diaphysis (1,) distinct from the epiph- y 8 es, (2, 3, 4 5.) Puncta ossificationis. Body ; corpus ossis. THE SKELETON. 43 structure, which remains until both have reached their full development and growth, when they become united through ossification of the inter- vening cartilage. FIG. 29. FIG. 28. a DEVELOPMENT OF THE VERTEBRAE, a, vertebra of a foetus, in a cartilaginous condition, with three centres of ossification; 1, 2, lateral pieces; 3, the body ; b, vertebra of an infant. The lateral pieces, 1, 2, are co-ossified at the spinous process, and join the body 3, at the sutures 4. The ends of the trans- verse and spinous processes yet in a cartilaginous state. DEVELOPMENT OF THE EPIPHYSES TO THE VERTE. BRJE. a, dorsal vertebra, with the epiphyses 4, 5, to the transverse processes; 6, to the spinous pro- cess; and 7, to the body; 6, arch with its processes; and c, body of a lumbar vertebra; 4, 5, epiphyses of the transverse processes; 6, of the spinous pro- cess; 7, 8, of the body; 9, 10, of tubercles of the upper articular processes. Ossification commences in the skeleton with the clavicle and lower jaw as early as the sixth or seventh week of embryonic life ; it then occurs successively in the vertebrae, humerus, femur, ribs, etc. At birth the diaphyses of most bones are ossified ; but none of the epiphyses ordin- arily have commenced the process, and this is also the case with the pa- tella and the carpal and tarsal bones, except the calcaneum and astragalus. Ossification of epiphyses commences with that of the condyles of the femur about the period of birth ; and it occurs with the numerous others of the skeleton at different periods up to adult age. The construction of bones from several centres of ossification faciltates the development of complex forms, though this means is not essential, for we find corresponding and equally complex bones in other animals developed from single centres. Thus the human humerus, which is developed from seven centres of ossification, and the femur from five, in birds, many lizards, and turtles, are developed from one. In most instances, separate centres of ossification, or groups of such cen- tres, are significant of permanently distinct bones in other parts of the same skeleton, or in the skeleton of other animals. Thus, as examples, we recognize the epiphysis of the olecranon of the ulna as representing the distinct patella ; the coracoid epiphysis of the scapula represents the distinct coracoid bone of birds ; the five divisions of the sacrum repre- sent as many true vertebrae : in whales, dolphins, and serpents, always remaining as separate elements in the vertebral series. 44 THE SKELETON. The presence of epiphyses, and the intervening plates of elastic carti- lage to the diaphyses, gives an important incidental condition in the pro- tection of the body from injury at a period of life when it is most liable to falls or blows. Through this condition the shock from such accidents is much lessened ; and the jar, which if communicated to the large and soft growing brain, or other delicate internal organs, might impair their structure, is much weakened, diffused, or intercepted. Frogs and toads, which from their remarkable leaping power might be supposed to be liable to violent concussions, retain epiphyses to the long bones of their limbs almost throughout life ; while the alligator and turtle, which in their sprawling condition are not liable to falls, have the long bones of their limbs developed without epiphyses. The cartilage of the embryonic skeleton consists of a comparatively soft, translucent, opalescent, homogeneous or faintly granular matrix, crowded with spherical or oval cells, which have finely granular contents and a central, nucleolated nucleus. In the progress of development of the young being, the cartilage cells multiply through division, and the intercellular matrix increases so as gradually to widen the spaces between the groups or rows of cells. In the cartilaginous diaphysis of long bones, the cartilage cells mul- tiply in linear rows, generally parallel with one another and with the long diameter of the diaphysis. In epiphyses and short bones, the cartilage cells form oblong groups irregularly dispersed from the centre. Just previous to ossification channels become developed in the inter- cellular matrix of the cartilage by resolution of its substance, and blood- vessels extend into them by continuous development from those of the exterior investing membrane. The cartilage at the centres of ossification assumes a yellowish hue and an indistinct fibrous appearance ; and at this time the chondrin is either converted into, or displaced by, the gelatinoid element. The calcareous substances are now deposited in the intercellular matrix as minute granules, which gradually become fused. The cartilage cells likewise receive the same deposit, and their walls coalesce with the ossified intercellular matrix. The remaining cavities of the cells, still filled with soft contents, constitute the lacunaB of bone. A few of the coarser canaliculi of the lacunae appear to be narrow unossified tracts, along which, perhaps, there are comparatively strong currents of nutritive matter. Most of the canaliculi, however, apparently originate by a subsequent resolution of ossific substance. The diaphysis of long bones grows in length by continuous develop- ment and ossification of cartilage at the extremities. Hence in the experiment, in which two holes are bored at a certain distance apart THE SKELETON. 45 in the shaft of a long bone of a young animal, after the latter has advanced in growth, the holes are found to remain the same distance from each other, while the shaft has increased in length in both direc- tions. Tabular bones extend in a similar manner at their borders ; and short bones and epiphyses generally in all directions from their centres of ossi- fication. The diaphysis of long bones grows in thickness by the development from the under surface of the periosteum of successive layers of a sub- stance, at first resembling incipient fibrous tissue, but subsequently em- bryonic cartilage. 1 In the latter condition, this substance, which con- sists of a homogeneous matrix crowded with cartilage cells, and pervaded with vessels from the periosteum, undergoes ossification in the manner already described. The tabular bones of the cranial vault and the bones of the face originate from the fibrous layers, which subsequently constitute their periosteum, in the same mode that the outer layers of the diaphysis of long bones are produced, as just described ; and they afterwards grow in thickness through the same process. The spongy substance of the bones is produced by a resolution of ossific structure, and the medullary cavity of long bones is formed by the gradual solution and absorbtion of spongy substance. At first the me- dullary cavities, as well as the interspaces of the spongy substance, are filled with a nutritive matter and numerous nucleated cells. The latter for the most part become converted into the adipose cells of the marrow of the medullary cavities. At birth, the canal near the middle of the shaft of long bones, which contains the principal medullary nutritious vessels, is the largest space in their interior; and it is from this canal that the medullary cavity is gradually extended by absorption of the spongy substance occupying the axis of the bone. As the diaphysis of the long bones of the limbs grows in length through ossification of the terminal cartilage, and grows in thickness through successive deposits from the periosteum, the medullary cavity increases almost as rapidly by absorption of previously formed osseous tissue. There- fore it is, before such a bone has reached its full growth, it appears to have been repeatedly absorbed and regenerated. Thus for example, the femur at the period of birth contains none of the osseous tissue of this bone in the embryo, and that of the child after a few years contains none 1 Which differs from ordinary cartilage in yielding gelatin instead of chondrin by boiling. 46 THE SKELETON. of the osseous tissue which existed at birth, and before maturity the bone changes several times again. After bones have reached their full growth, calcareous deposits con- tinue still to be made gradually throughout life, thus rendering them harder and more brittle. The medullary cavities, and also in a less striking manner the interspaces of the spongy substance, slowly increase in size, so that the bones of old persons are rendered comparatively brittle from this circumstance, as well as from the increase of calcareous deposits. ARTICULATIONS OR JOINTS OF THE SKELETON. The articulations or joints 1 of the skeleton exhibit a gradation of union from those which are immovable to such as possess motion in all directions. The most immovable articulations 2 are those which exist between the bones of the skull, constituting what are called the sut'ures. 3 Many of the sutures are formed through indentations of the contiguous mar- gins of the bones, which are mutually adapted to one another, often in a somewhat dovetailed manner. From their toothed appearance they are called dent'ated or seriated sut'ures. 4 Examples of them are seen in the union of the frontal, parietal, and occipital bones. In other sutures the contiguous borders of bones are beveled off and mutually coadapted, as observed in the union of the sphenoid and temporal bones with the parietal. Such, from their scale-like arrangement, are called squa'mous sutures. 5 In some sutures, 6 plane borders of contig- uous bones, slightly roughened, are coadapted, as in the union of the upper maxillary bones. Occasionally the border of one bone is grooved to receive the sharpened edge of another, 7 as in the articulation of the vomer with the sphenoid bone. The next form of articulation possesses more or less flexibility without allowing other motion. Such a joint is called a sym'physis, 8 and is formed by the union of broad surfaces of contiguous bones through means of an intervening plate of nbro-cartilage. Examples of this mode of junction are presented in the union of the bones of the pelvis, the bodies of the vertebrae, and the pieces of the sternum. In the movable articulations 9 the bones have their opposed sur- 1 Arthroses. 6 Harmonia ; harmony ; false suture. 2 Synarthroses. 7 Schindylesis. 3 Suturae. 8 Amphiarthrosis. * S. dentatse; s. serratae. 9 Diarthroses ; dinrthrodial articulations. 5 S. squamosse. THE SKELETON. 47 faces invested with cartilage, and their union is preserved by means of ligaments, which inclose the joints. Muscles or their tendons, which in many instances more or less surround these joints, very much contribute to the firmness of their union, and thus to prevent dislocation To facili- tate movement, they are lined with syno'vial membrane, which secretes a lubricating liquid, named the syno'via. Of the movable articulations there are several varieties, which exhibit different degrees of mobility. In some instances the movements are exceedingly limited, amounting only to a slight degree of gliding of the opposed surfaces upon each other, as instanced in most of the joints of the carpus and tarsus, and those of the articular processes of the vertebrae. In other cases the joints are restricted to a hinge-like motion, 1 as ob- served in the elbow and knee joints, and those of the fingers and toes. 2 The hinge-like movement, together with a motion toward either side, is observed in the wrist and ankle joints. Occasionally joints admit only of a rotary motion, as in the two radio- ulnar articulations and those between the atlas and axis. The most movable articulations are the ball-and-socket joints, 3 in which the head of one bone fits into a more or less deep cup-shaped con- cavity of the contiguous bone. Examples of such joints are presented in the shoulder and hip. The movements of these joints are those of flexion and extension, abduction and adduction, circumduction and rota- tion. Of the different movements of the articulations, flex'ion is that in which one or more bones of a joint are made to describe an angle with others, in moving either backward or forward. Thus the bending of the bones of the forearm forward, is the flexion of the forearm upon the arm ; the bending of the leg backward, is its flexion upon the thigh. Extension is the opposite movement of flexion, in which the bones are generally brought into a line with one another. Thus the bending of the forearm backward after it has been flexed, so as to bring it on the same line with the arm, is the extension of the forearm. Abduc'tion is that movement in which a bone is directed outwardly from another, or from the body ; and adduction is the opposite move- ment, in which a bone is directed inwardly. Thus the movement by which the thumb is moved outwardly from the fingers is abduction, and that by which it is made to approach them is adduction. CircTimduc'tion is that motion of a bone when its head acts as a pivot 1 Ginglymus ; ginglymoideus. 2 Ginglymoid joints. 3 Enarthroses. 48 THE SKELETON. and the distal end is made to describe a circle. This character of move- ment is best exemplified with the humerus and glenoid cavity of the scapula. Rota'tion is the motion made by a bone when it rolls on its axis, as in the movements of the radius upon the ulna. OF THE RELATIVE POSITION OF THE DIFFERENT STRUCTURES ENTERING INTO THE COMPOSITION OF ARTICULATIONS. The bones articulating by suture are continuously associated by inter- vening cartilage, which is apt to ossify after the bones have reached maturity. The fibrous periosteum in all cases passes over the sutures, resembling in this position the capsular ligaments of movable joints. In symphyses an intervening plate of fibro-cartilage intimately connects the surfaces of the contiguous bones ; and they are surrounded with bands of fibrous tissue, corresponding with the capsular ligaments of movable articulations. In movable joints the opposed surfaces of the bones are invested with a layer of cartilage, which from its position is called artic'ular car'ti- lage. 1 When the cartilage covers a depressed or concave surface, it usually becomes thicker toward the borders, so as to deepen the con- cavity ; but if it invests a head, condyle, or other articular prominence, it becomes thinner toward the margins. The ligaments surrounding movable joints are of two kinds : the cap'sular 2 and band-like lig'aments. 3 The former are cylindrical sacs, including by their extremities the borders of the articular surfaces of bones, where they become continuous with the periosteum of the latter, and frequently with the contiguous tendons of muscles. They vary in thickness ; are composed of an intertexture of bundles of fibrous tissue, and are highly flexible and slightly extensible. In many posi- tions, broad tendons of muscles, passing over joints, assume their place, as in the case of the tendon of the quadriceps extensor muscle of the thigh, and the extensor tendons on the backs of the phalangeal articula- tions. The band-like ligaments are accessory to the capsular ligaments, contributing to the strength of joints in particular positions. They are strong bundles of parallel filaments of^ fibrous tissue, quite flexible, but entirely inextensible. They constitute the numerous lateral ligaments of the joints. The syno'vial mem'branes belong to the class of serous membranes. They line the interior of capsular ligaments ; and in the adult are re- flected upon the border of the articular cartilages ; but in infancy they 1 Diarthrodial cartilage. 2 Capsulse articulares. 3 Funicular ligaments. THE SKELETON. 49 invest the entire cavity of joints. They secrete a viscid, albuminoid liquid resembling the white of eggs, and called the syno'via, which lubri- cates the surfaces of joints, and, by lessening friction, facilitates motion. The synovial, like other serous membranes, are composed of a delicate structureless layer, or basement membrane, attached beneath by a layer of connective tissue, in which blood-vessels are distributed, and invested on the free surface with several layers of pavement-like, nucleated cells. Their inner surface is smooth, and they possess no glands. At the borders of joints they are frequently thrown into folds and processes, containing connective tissue, fat, and an occasional isolated cartilage cell. These syno'vial fringes 1 apparently act as cushions to fill up interspaces, though from their greater comparative vascularity than other portions of the membrane, they are no doubt especially active in the production of synovia. Concave articular surfaces are frequently rendered deeper by the pro- vision of a band of fibro-cartilage tipping or surrounding their margin, as in the case of the glenoid cavity of the shoulder and the acetabu- lum of the hip-joint. Occasionally joints are partially or completely divided into two parts by the introduction of an inter-articular fibro- cartilaginous disk, as in the case of the articulation of the lower jaw and the knee-joint. In some instances bones are connected by ligaments totally different from the ordinary ones, being composed of an elastic substance ; such are the yellow ligaments which conjoin the vertebral arches ; and such also is the nature of the nuchal ligament which sustains the head of quadrupeds. The various structures which have been mentioned as entering into the composition of the articulations consist of bones, cartilages, fibro-carti- lages, ligaments, and synovial membranes. The constitution of bones or of the osseous tissue has been described, but a consideration of the tissues comprising the remaining structures is deferred at present, on account of their entering into the constitution of many other organs. The structure of the cartilages and nbro-cartilages will be found under their appropriate head; the structure of ligaments in the description of the white fibrous, and yellow elastic tissues ; and the synovial mem- branes are again mentioned in the account of the serous membranes. 1 Synovial glands of Havers ; Haversian glands ; glandulae articulares ; synovial fimbrise. 4 50 THE SKELETON. BONES OF THE HEAD OR SKULL. The bones of the head or skull are twenty-two in number, and with one exception, that of the lower jaw, are firmly and immovably articu- lated. They form together cases for the reception and protection of the brain, the organs of especial sense, and the commencement of the alimentary and respiratory passages. They are divisible into two groups : those of the cranium or brain case, eight in number, and those of the face, fourteen in number. BONES OF THE CRANIUM. Of the eight bones of the cranium, four are single and symmetrical : the occipital, sphenoid, ethmoid, and frontal bones, situated at the occi- put, base, and forehead. The other bones are in pairs : the parietal and temporal bones, situated at the top and sides of the cranium. THE OCCIPITAL BONE. The Occip'ital bone 1 occupies the posterior extremity of the cranium, FIG. 30. FIG. 31. EXTERNAL VIEW OF THE OCCIPITAL BONE. 1, su- perior curved line ; 2, external occipital protuber- ance; 3, occipital crest; 4, inferior curved line; 5, occipital foramen; 6, condyle; 7, fossa behind the condyle, in which a venous foramen frequently opens; 8, position of condyloid foramen; 9, trans- verse process ; 10, notch contributing to form the jugular foramen; 11, basilar process. INTERNAL VIEW OP THE OCCIPITAL BONE. 1, fossa for the cerebrum; 2, fossa for the cerebellum; 3-6, occipital cross; 3, groove for the longitudinal sinus ; 4, ridge for the attachment of the cerebellar falx; 5, groove for the lateral sinus; 6, internal oc- cipital protuberance; 7, occipital foramen; 8, ba- silar process; 9, 10, groove for the lateral sinus, de- scending on the transverse process to the jugular notch; 11, border for the parietal bone; 12, bor- der for the temporal bone ; 13, position at which the ninth, tenth, and eleventh cerebral nerves pass through the jugular foramen; 14, condyloid fora- men. 1 Os occipitis; os puppis; os memorise; os basilare; part of the os spheno-basil- are ; os lambdoides ; os nervosum ; os prorse ; os pyxidis ; os laudge ; os fibrosum ; os pelvicephalicum ; os sextum cranii. THE SKELETON. 51 extending forward into the base of the latter. It has a general quadrate outline, with a convex external and a concave internal surface. Its lower portion presents a large oval aperture, the occipital fora'- men, 1 which gives transmission to the spinal cord, the spinal accessory nerves, and the vertebral arteries. In advance of the foramen is a thick plate, the bas'ilar proc'ess, 2 the lateral borders of which are rough and contiguous to the petrous por- tion of the temporal bone; and its anterior extremity is rough and con- nected with the body of the sphenoid bone by means of an intervening plate of cartilage. The latter ossifies about the age of puberty, thus associating the occipital and sphenoid bones into one piece. 3 The upper surface of the basilar process is a smooth, shallow groove, 4 inclining to the occipital foramen, and supporting the medulla oblongata. The under surface 5 is impressed by muscular attachments, and overhangs the pharynx. On each side of the occipital foramen anteriorly, and on the under part of the bone, are situated the con/dyles. These are two oblong prominences, converging forward, with their lower surface convex, inclined outwardly, and covered with cartilage. Between them and the corresponding articulating processes of the atlas, the backward and for- ward movements of the head occur. At their inner border, they are roughened for the attachment of ligaments. Piercing the bone, above the middle of the condyles, from within out- wardly, is the con/dyloid fora'men, 6 for the transmission of the hypo- glossal nerve. Frequently at the back of the condyles there is another foramen, 7 for the transmission of a vein. To the outer side of the condyles is an angular prominence, the trans'- verse proc'ess, which presents a ridge 8 below for muscular attachment, a groove above to accommodate the termination of the lateral sinus, and an articular surface at the extremity covered with cartilage. In front of the process is a wide notch, which, with the contiguous border of the temporal bone, forms the ju/gular fora'men, for the conjunction of the lateral sinus with the jugular vein and the transmission of the spinal accessory, pneunio-gastric, and glosso-pharyngeal nerves. The upper expanded portion of the bone is convex externally, and 1 F. occipitale magnum ; f. magnum. 5 Basilar surface. 2 Pars basilaris; body of the occipital 6 Anterior condyloid foramen, bone; basi-occipital bone; processus 7 Posterior condyloid foramen, cuneiformis. 8 Jugular tubercle, or paramastoid pro- 3 Os basilare ; os spheno-occipitale. cess of lower animals. 4 Basilar fossa. 52 THE SKELETON. presents just above its centre the external occip'ital protuberance. From this a ridge, the occip'ital crest, 1 descends to the occipital fora- men and gives attachment to the nuchal ligament. From the protuber- ance there extends outwardly the superior curved line, 2 so called in contradistinction to another lower down, the inferior curved line, 3 These lines, which are only well marked in well-developed muscular indi- viduals of mature age, together with the surfaces between and below them, give attachment to the muscles which sustain the erect position of the head. The inner surface, of the expanded portion of the bone, is divided by ridges, forming the occip'ital cross, into four broad, shallow fossee, of which the lower two accommodate the hemispheres of the cerebellum, and the upper two the posterior lobes of the cerebrum. The prominent centre of the cross is the internal occip'ital protu'berance, which is situated a little lower than the external one. The upper limb of the occipital cross is marked by a groove indicating the course of the terminal portion of the longitudinal sinus ; and it has attached to it the posterior extremity of the cerebral falx of the dura mater. The lower limb, extending to the occipital foramen, has the cerebellar falx attached to it. The lateral limbs are marked with grooves indicating the course of the lateral sinuses and the attachment of the tentorium. The superior borders of the bone are dentated, and converge to form the occip'ital angle, which is received between the parietal bones. The lateral borders inferiorly articulate with the mastoid portions of the tem- poral bones. The upper extremity of the occipital bone is occasionally found to be separated from the other portion by a transverse suture at any position down to the superior curved line. Such an anomalous piece corresponds with the interparietal bone of certain of the lower animals, as many rodents and ruminants. Occasionally the anomalous human inter- parietal bone is divided in the median line into two parts. THE SPHENOID BONE. The Sphe'noid bone 4 is situated across the base of the cranium, and extended up on each side, just in advance of the middle. It contributes 1 Occipital spine. tiforme; os azygos; os inconjugatum ; os 2 Superior semicircular ridge. alatum; osalaeforme; os polymorphon ; 8 Inferior semicircular ridge. os pterygoideum ; os colatorii ; os cuneo * Os 'sphenoideum ; os sphecoideum ; comparatum ; sphenoidal part of the os os cuneiforme ; os vespiforme ; os basil- spheno-basilare, or of the os spheno- are; os baxilare ; ospapillare; os mul- occipitalis. THE SKELETON. 53- FIG. 32. to the formation of the cranial cavity, the orbits, and the temporal, spheno-maxillary, and nasal fossae. From its complex form we may examine in succession its body, its small and great wings, its pterygoid processes, and its foramina. The body 1 or central portion of the bone is irregularly cuboidal, and articulates posteriorly by a rugged surface, in the manner previously men- tioned, with the occipital bone. Its upper surface presents a deep excava- tion, the pitu/itary fos- sa, 2 which lodges the pi- tuitary body of the brain. Posteriorly the fossa is bounded by an oblique plate, the dCCliv'ity, 3 FRONT VIEW OF THE SPHENOID BONE. 1, 2, sphenoidal crest and whioh rontinnps the slone rostrum for J inin s the nrtsal P late of the ethmoid bone and the 10 P e vomer; 3, entrance of the sphenoidal sinuses; 4, small wing; 5, Of the basilar prOCeSS Of O ptic foramen piercing its base ; 6, sphenoidal foramen; 7, rotund the occipital bone, and supports the pons. The convex prominence in front, is the olivary proc'ess, 4 upon the slight- ly depressed surface of which the commissure of the optic nerve rests. In advance of this, is a smooth surface inclining toward the ethmoid bone, with which it articulates by its anterior border. The prominent angles of the declivity are called the posterior cli'noid processes, 5 in contradistinction to the obtuse, backward projections, of the small wings, called the anterior cli'noid processes. 5 On each side of the body, below the pituitary fossa, there is a shallow groove, 6 for the accommodation of the internal carotid artery, which curves from a notch at the back of the bone to the interval between the anterior clinoid and olivary processes. The inferior surface of the body, which overhangs the posterior nares, foramen; 8, orbital surface of the great wing; 9, temporal sur- face of the same; 10, ridge separating the temporal and spheno- maxillary fossae; 11, position of the pterygo-palatine canal; 12, pterygoid canal; 13, internal pterygoid process, ending in a hook 14; 15, external pterygoid process; 16, spinous process; 17, oval foramen; 18, spi nous foramen. 1 Basisphenoidbone; posterior or prin- cipal sphenoid bone ; basis sive corpus partis sphenoidalis ossis spheno-occipi- talis. 2 Sella turcica; s. equina; ephippium. 3 Dorsum ephippii; clivus; clivus Blu- menbachii. 4 Tuberculum ephippii. 5 Processus clinoidei posteriores et an- teriores ; apophyses clinoides. 6 Sulcus caroticus. 'tHcJ 54 THE SKELETON. FIG presents a median acute ridge, the ros'trum, 1 with which the expanded border of the vomer articulates ; and on each side is a thin projecting plate, which joins the reflected margin of the same bone. The anterior surface, directed toward the nasal fossae, presents a median ridge, the sphe'noidal crest, 2 which articulates with the nasal plate of the ethmoid bone. On each side of the crest is an opening communicating with the sphe'noidal sinuses, 3 which are two large cavities hollowed in the interior of the body, and separated by a usually unsymmetrical par- tition. In infancy the sphenoidal sinuses do not exist ; and the body then presents inferiorly a thick median ridge, with a triangular space on each side. These spaces receive a pair of hollow cones, 4 projecting from the ethmoid bone, which subsequently coalesce with the sphenoid bone and detach themselves from the former, thus producing the sphenoidal sinuses. The small wings 5 of the sphenoid bone are two sabre-like processes, which extend horizontally outward from the antero- lateral portion of the body. Their anterior rugged bor- der articulates with the orbital plates of the fron- tal bone ; and their pos- terior smooth and curved border is received into the fissure separating the an- terior and middle lobes of the cerebrum. Their outer end is sharp pointed ; and their posterior end forms the blunt anterior cli'noid process. The great wings 6 pro- ject laterally from the body, curve outward, for- ward, and upward, and present three important surfaces. The superior UPPER VIEW OP THE SPHENOID BONE. 1, pituitary fossa; 2, olivary process; 3, declivity; 4, anterior clinoid process; 5, pos- terior clinoid process; 6, posterior border of the body; 7, cerebral surface of the great wing; 8, articular surface for the frontal bone ; 9, articular border for the temporal bone ; 10, spineus pro- cess; 11, small wing; 12, border articulating with the orbital plate of the frontal bone; 13. border joining the ethmoid bone; 14, optic foramen ; 15, sphenoidal foramen ; 16, rotund foramen ; 17, oval foramen; 18, spinous foramen; 19, groove for the internal carotid artery. 1 Processus azygos. 2 Crista or spina sphenoidalis. 3 Sinus sphenoidales. 4 Ossicula Berlin! ; cornua sphenoi- dalia; pyramids of Wistar; ossa triangu- laria. 5 Alae minores; processus enciforoies; apophyses Ingrassii. 6 Alao magnse, temporal wings. THE SKELETON. 55 or cer'ebral surface 1 is a crescentic concavity contributing to form the middle cerebral fossa. The anterior or orVital surface 2 is an oblique quadrate, vertical plane, forming part of the outer wall of the orbit. The external or temporal surface 3 is divided by a ridge into two parts, of which the upper, slightly concave and directed outwardly, forms part of the temporal fossa, while the lower division directed downward forms part of the spheno-maxillary fossa. From the back part of the great wing projects the thick, angular, spinous process, 4 which is received in the interval between the squamous and petrous portions of the temporal bone. Upon the broad rough surface inclining from the summit of the great wing forward, rest the anterior prolonged angle of the parietal bone and the orbital plate of the frontal bone. The anterior border of the orbital surface articulates with the malar bone, and its lower border forms the upper boundary of the spheno-maxillary fissure. The posterior concave border of the great wing joins the squamous portion of the tem- poral bone. The pter'ygoid proc'esses 5 project vertically downward from the junc- tion of the great wings with the body. They consist of a pair of plates united at an angle anteriorly, and diverging posteriorly, so as to inclose an angular groove, the pter'ygoid fossa. 6 The external pter'ygoid pro- cess is broad and thin, and directed outward and backward. The inter- nal pter'ygoid process is longer and narrower than the other ; and it forms the lateral border of the posterior nares. At its upper part behind is a fossa 7 for the origin of the tensor muscle of the palate ; and its lower part is prolonged into a hook 8 around which the tendon of the latter muscle turns in its course to the palate. The pterygoid fossa at its lower part presents a deep angular notch, 9 which is occupied by the pyramidal process of the palate bone. The foramina of the sphenoid bone are numerous and important. The op'tic fora'men 10 pierces the base of the small wing from the side of the olivary process outward and forward. It transmits the optic nerve and ophthalmic artery from the cranial cavity to the orbit. The sphenoid'al fora'men 11 in the separated bone is open at its outer end, but is closed by the apposition of the frontal bone. It is club- 1 Superficies cerebralis ; s. interna. 7 Scaphoid fossa. 2 S. orbitalis; s. anterior. 8 Hamuluspterygoideus; hamular pro- 3 S temporalis ; s. externa. cess. 4 Lamina triangularis ; spina angu- 9 Incisura pterygoidea ; fissura ptery- laris. goidea. 5 Processus pterygoidea ; aloe inferi- 10 Foramen opticum. ores; a. palatinae; processus aliformes. n F. sphenoidalis; f. orbitalis superior ; 6 Fossa pterygoidea. f. lacerum superius. 56 THE SKELETON. shaped, with the broad end internal, and separates the small and great wings. It opens into the orbit and transmits the occulo-motor, pathetic, ophthalmic, and abducent nerves, and the ophthalmic vein. The rotund' fora'men 1 pierces the great wing from behind forward, just below the inner extremity of the preceding foramen. It opens from the cerebral surface into the pterygo-m axillary fossa, and transmits the superior maxillary nerve. The oval fora'men, 2 larger than the last, and less than half an inch behind it, pierces the great wing vertically, and transmits the inferior maxillary nerve. The spinous fora'men, 3 quite near the preceding, pierces the spinous process vertically, and transmits the great meningeal artery. The pter'ygoid. canal 4 penetrates the root of the pterygoid processes from before backward, and transmits the pterygoid nerve. The pter'ygo-pal'atine canal 5 is a small groove situated internally to the former, and converted into a complete canal by the apposition of the palate bone. THE ETHMOID BONE. The Eth'moid bone 6 is situated at the anterior part of the base of the cranium, between the cavity of the latter and the nasal fossae, and between the orbits. It is cuboidal in form, and is exceedingly light, in conse- quence of its excavated character. We may consider, separately, its vertical lamina, its cribriform plate, and its lateral masses. The vertical lamina occupies the median line. Its upper portion, pro- jecting into the cavity of the cranium, is the ethmoid'al crest, 7 which is thick and prominent in front, and rapidly declines posteriorly. It sepa- rates the ethmoidal gutters, and has attached the anterior extremity of the cerebral falx. From its front project the ethmoid'al wings, 8 two small processes resting against the frontal bone. The lower four-fifths of the vertical lamina form the na'sal plate, 9 which contributes about one-third to the extent of the nasal partition. Its posterior border joins the sphenoidal crest ; its inferior, the vomer ; and its anterior below, the triangular cartilage ; and above, the nasal process of the frontal bone. Its superior border on each side is pierced by vertical canals, for the passage of branches of the olfactory nerves. 1 F. rotundum. spongiosum; os cristatum; os cubicum; 2 F. ovale. os colatorium ; os foraminulentum ; os 8 F. spinosum. coliforme : os multiforme. 4 Canalis pterygoideus; c. Vidianus. 7 Crista ethmoidalis ; crista galli. 5 Canalis pterygo-palatinus. 8 Processus alares. 6 Os ethmoideum ; os cribrosum ; os 9 Lamella nasalis. THE SKELETON. 57 FIG. 34. si'nuses, 3 which are usually separated into three sets : terior. the anterior, middle, and pos- The criVrifonn plate 1 is the horizontal perforated portion connecting the lateral masses with the vertical lamina, and occupying the interval of the orbital plates of the frontal bone. It separates the cavity of the cranium from the nasal fossae, and is depressed on each side of the ethmoidal crest, so as to form the ethmoid'al gutters, for the lodg- ment of the olfactory bulbs. Its numerous orifices 2 transmit the nerves from the latter, except the larger anterior one, which gives passage to the nasal branch of the ophthalmic nerve. The lateral masses consist of an aggrega- tion of thin walled cavities, the ethmoid'al UPPER VIEW OF THE ETHMOID BONE 1, orbital surface of the lateral mass; 2, posterior extremity of the cribri- They are bounded externally by the fa &**#> which unite8 the lateral ,.._,. i i / /> j.i masses, and is depressed and perfo- orbital plate, 4 which forms part of the inner rated with numerou3 foramina on Wall Of the Orbit. The plate is Square, but each side of the ethmoidal crest 3; the . , fy, . , , . i 11 j -i two oblique processes in advance of not being sufficiently extensive to close all the the latter are the ethmoidal wings; Sinuses, this is done in front by the lachrymal 4, anterior extremity of the nasal and maxillary bones, above by the borders of plate; 5 ' th ' the orbital plates of the frontal bone, and behind by the sphenoid and palate bones. The inner or nasal surface of the lateral masses presents two oblique, scroll-like laminae, the superior and inferior tur'binated proc'esses. 5 The former is posterior, shorter than the other, and is thin and narrow. The latter extends the length of the lateral mass, and presents a convex surface toward the nasal partition, a concave surface toward the eth- moidal sinuses, and a convoluted and rough border downward. Between the turbinated processes is an oblique fissure, the superior mea'tus 6 of the nose, into which opens the posterior and middle ethmoidal sinuses. Above the processes, the surface is perforated by branches of the olfactory nerve. The inferior turbinated process forms the upper boundary of the middle mea'tus 7 of the nose, into which opens the anterior, and sometimes the middle ethmoidal sinuses. 1 Lamina cribrosa. 2 Foramina cribrosa. 3 Cellulae ethmoidales. 4 Os planum ; lamina papyracea. 5 Superior and middle turbinated bones ; concha sup. et inf. ; c. minor et major; ossa spongiosa sup. et medius; superior and middle spongy bones. 6 Meatus narium superior. 7 M. n. medius. 58 THE SKELETON. From the lower portion of the lateral mass, where it rests upon the maxillary bone, one or two small irregular plates 1 project downward so as to diminish the size of the aperture of the maxillary sinus. FIG. 35. THE FRONTAL BONE. The Front'al bone 2 is situated at the anterior part of the cranium, and forms the basis of the forehead, the root of the nose, and the roofs of the orbits. Externally it is convex and smooth, and presents on each side the front'al eminence, 3 usually the most prominent part of the fore- head, and especially well marked in the young. At the lower border of the bone on each side is an arching ridge, the supra-orbital margin, the ex- tremities of which terminate in the external* and internal angular processes. At the inner part of the ridge is a foramen, or a notch converted into one by a ligament, the supra-orb'ital fora'men, which transmits an artery and nerve to the forehead. Above the supra-orbital margin is an arching prominence, the super- ciliary ridge, 5 which is situated just above the eyebrow, and varies in degree of development in different individuals. The prominence between the ridges of the two sides is the nasal eminence, 6 the width of which has much influence in the intellectual expression of the face. Below, it terminates at the root of the nose, 7 which is a rough surface, for articu- lating with the nasal and maxillary bones. From this surface projects the nasal spine, 8 which serves as a point of support to the nasal bones, and joins behind the nasal plate of the ethmoid bone. EXTERNAL VIEW OF THE FRONTAL BONE. 1, situa- tion of the frontal eminence; 2, situation of the superciliary ridge; 3, supra-orbital margin; 4, 5, external and internal angular processes; 6, supra- orbital notch or foramen; 7, nasal eminence; 8, temporal ridge ; 9, nasal spine. 1 Processus uncinatus; p. Blumen- bachii. 2 Os sincipitis; os coronale; os prorae; os puppis; osrationis; os inverecundum. 3 Tuber frontalis; frontal protuber- ance. 4 Processus zygomaticus. 5 Arcus superciliaris. 6 Nasal tuberosity ; glabella ; inter- cilium; met opium; mesophryon. 7 Pons nasalis. 8 Spina nasalis superior. THE SKELETON. 59 FIG. 36. At the side of the bone, curving upward and backward from the external angular process, is the tem'poral ridge, which includes the anterior part of the temporal fossa. The internal surface of the frontal bone is generally concave and impressed by the convolutions of the cerebrum. In its middle below is a ridge, the front/al crest, 1 which gives attachment to the cerebral falx, and disappears above at the sides of a shallow groove for ac- commodating the longitudinal sinus. At the bottom of the crest is a blind-pit, 2 or a canal, 3 transmitting a vein from the nose to the latter sinus. From the lower part of the in- ternal surface project the two broad, arching orb'ital plates, 4 which form the roofs of the orbits. They are separated by a wide interval, the ethmoid'al fissure. 5 Above, they are convex, and strongly marked by the inferior convolutions of the anterior cerebral lobes. Below, they are concave and smooth, and are deeply depressed within the position of the external angular process for the accommodation of the lachrymal gland. 6 Just above the internal angular process, on the same surface, is a small impression, 7 made by the fibro-cartilaginous pulley of the superior oblique muscle of the eyeball. The outer border of the orbital plate and the external angular process articulate with the malar bone ; and the posterior border of the former joins the small wing of the sphenoid bone. Its inner border exhibits several superficial excavations, which form the upper boundary of the ethmoidal sinuses, and in front of them is the communication with the INTERNAL VIEW OF THE FRONTAL BONE. 1, com- mencement of the groove for the longitudinal sinus, formed by the divergence of .the frontal crest ; 2, is placed in the ethmoidal fissure, and points to a small venous canal; 3, superior dentated border, articulating with the parietal bones; 4, pos- terior border of the orbital plate 5, which joins the small wing of the sphenoid bone ; 6, irregular inner border of the same plate which covers the upper part of the ethmoidal sinuses; 7, points to the posi- tion of the ethmoidal foramina; 8, nasal spine; 9, thick rough border articulating with the great wing of the sphenoid bone; 10, refers to the black spot which indicates the position of a fossa for the trochlea of the superior oblique muscle; to its outer side is the supra-orbital notch ; 11, internal angular process, and entrance to the frontal sinus; 12, external angular process. 1 Crista frontalis. 2 Foramen coecum. 3 Porus cranio-nasalis. 4 Paries orbitales or horizontales. 5 Incissura ethmoidalis. 6 Fovea glandulae lachrymal! 7 Foveola trochlearis. 60 THE SKELETON. front/al si'nus. 1 This cavity extends upward and outward within the position of the superciliary ridge, and varies in size in different individ- uals. Very rarely it does not exist ; but not unfrequently it extends as high as the frontal prominence, and backward into the orbital plate. It is separated from the other by a partition, and communicates through the anterior ethmoidal sinuses with the nose. The upper thick dentated border 2 articulates with the parietal bones, and the lateral beveled and roughened border with the sphenoid bone. THE PARIETAL BONE. The Pari'etal bone 3 forms the upper part of the cranial vault between the frontal and occipital bones, and is united with its fellow in the median line. It is square, with the external surface convex and smooth, FIG. 37. FIG. OUTER VIEW OF THE LEFT PARIETAL BONE. 1, upper border; 2, beveled lower border, which ar- ticulates with the squamous portion of the tempo- ral bone; 3, anterior border, joining the frontal bone; 4, occipital border; 5, temporal ridge; (, venous foramen; 7, prolonged anterior inferior angle joining the summit of the great wing of the sphenoid bone ; 8, posterior inferior angle articu- lating with the mastoid portion of the temporal bone. INNER VIEW OF THE LEFT PARIETAL BONE. 1-4, borders corresponding with same numbers in for- mer figure; 5, groove for the longitudinal sinus, and communication with it, of a venous foramen, 6; 7, 8, anterior and posterior inferior angles; the groove on the latter accommodates the lateral sinus. The arborescent lines on the inner concave surface of the bone indicate grooves produced by the great meningeal artery. and the internal surface concave, ridged, and impressed by the aborescent branches of the great meningeal artery. Toward the middle of the bone externally is the most prominent part, named the pari'etal eminence ;* and just below this is a superficial curved 1 S. superciliaris; s. pituitarii front is; caverna frontis. 2 Margo coronalis. 3 Os parietale ; o. bregmaticum ; o. verticale; o. verticis; o. tetragonum ; o. nervale. 4 Tuber parietale; parietal protuber- ance. THE SKELETON. 61 line, the tem/poral ridge, which defines the upper part of the temporal fossa. Along the superior border internally, of the two bones in conjunction, a shallow groove is visible, indicating the course of the longitudinal sinus. Of the four angles of the parietal bone, the anterior inferior is most prolonged, and articulates with the great wing of the sphenoid bone. The posterior inferior angle joins the mastoid portion of the temporal bone, and internally is impressed by the lateral sinus. Of the four borders of the bone, the anterior, superior, and posterior are nearly straight, thick, and dentated for articulation with the frontal, the opposite parietal, and the occipital bones. The inferior border is curved and beveled to a sharp edge for articulation with squamous por- tion of the temporal bone. THE TEMPORAL BONE. The Tem/poral bone 1 extends into its base. It is of complex form, and divisible into the squamous, mastoid, and petrous portions. The squa'mous por- tion, 2 so named from its scale-like form, presents an external smooth sur- face, which contributes to the temporal fossa; and an internal surface, marked by the cerebral convolutions and great meningeal artery, form- ing part of the middle cerebral fossa. Its up- per border is beveled to a thin edge, and over- laps the contiguous bor- der of the parietal bone ; and its anterior border, less beveled, articulates is situated at the side of the cranium, and FIG. 39. EXTERNAL VIEW OP THE TEMPORAL BONE OP THE RIGHT SIDE. 1, squamous portion; 2, mastoid portion; 3, apex of the petrous por- tion; 4. zygomatic process; 5, glenoid cavity; 6, glenoid tubercle 7, glenoid fissure; 8, mastoid process; 9, back part of digastric groove; 10, mastoid foramen; 11, auditory process, by extension inwardly, forming the vaginal process ; 12, external auditory meatus ; 13, styloid process; 14, slight impression of the deep temporal artery. with the sphenoid bone. From near the 1 Os temporale ; o. temporis ; o. parietale inferius; o. lapidosum ; o. squamosum ; o. crotaphy ticum ; o. memento mori ; o. mendosum; o. arcuale; o. armale. 2 Pars squaitiosa ; squama; lepisma; os lepidoides; os squamiforme. 62 THE SKELETON. FIG. 40. middle of its lower border externally, the zygomat'ic process 1 arches outward and forward to join the corresponding process of the malar bone, and thus form the zygo'ma 2 or yoke through which the tem- poral muscle proceeds to its insertion. Beneath and internal to the position of the root of the process, is a transverse concavity, the gle'noid fossa, 3 and in advance of this a transverse eminence, the gle'- noid tubercle, 4 both of which enter into the artic- ulation of the lower jaw. Posteriorly, the fossa is separated from the pet- rous portion of the bone by the gle'noid fissure, 5 The mas'toid portion, 6 named from its nipple-like prominence, occupies the back part of the bone, and articulates with the pari- etal and occipital bones. It is thick, and occupied interiorly with the mas'- toid sinuses, 7 which com- municate with the tym- panum. The flattened nip- ple-shaped prominence, or mas'toid process, 8 pro- jects downward, and is roughened for muscular attachment. On its inner side is situated the di- gas'tric groove, 9 for the origin of the correspon- sively named muscle. INTERNAL VIEW OF THE TEMPORAL BONE OF THE LEFT SIDE. 1, squamous portion ; 2, posterior border of the mastoid portion articulating with the occipital bone ; 3, petrous portion ; \4, bev- eled edge, which overlaps the lower edge of the parietal bone ; 5, thick upper border of the mastoid portion, articulating with the posterior inferior angle of the parietal bone; 6, end of the zygomatic process; 7, groove produced by the great meningeal artery; 8, mastoid process; 9, digastric groove; 10, mastoid foramen opening into the groove 11, for the lateral sinus ; 12, in- ternal auditory meatus; 13, styloid process; 14, prominence produced by one of the semicircular canals of the labyrinth ; 15, Fallopian hiatus; 16, foramen for the transmission of a branch of the tympanic nerve ; 17, cleft which transmits a small blood-vessel to the vestibule of the labyrinth; 18, termination of the carotid canal; 19, Eustachian tube; 20, groove of the euperior petrosal sinus. The inner sur f ace mastoid portion forms part of the cerebellar fossa, and presents a wide 1 Processus zygomaticus; p. jugalis. 2 Arcus zygomaticus; zygomatic arch. 3 Fossa glenoidalis. 4 Tuberculum articulare. 5 Fissura Glasseri ; Glasserian fissure. 6 Pars mastoidea; p. mammillaris. 7 Cellulae mastoideae ; antrum mas- toideum. 8 Processus mastoideus ; apophysis mammillaris. 9 Digastric fossa; mastoid groove; in- cissura mastoidea. THE SKELETON. 63 descending groove, 1 which indicates the course of the lateral sinus. From the groove a foramen 2 generally perforates the border of the bone for the transmission of a vein from the scalp. The petrous portion, 3 named from its comparative hardness, contains the labyrinth and tympanum. 4 It forms a prostrate, trilateral pyramid projecting into the base of the cranium inward and forward. Its base rests against the junction of the other two portions of the bone, and between these, externally, presents the external auditory mea'tus, 5 a wide oval canal, directed inward and forward to the tympanum, and bounded below by a scroll-like plate, the auditory process, the border of which is rough, for the attachment of the auricle. The apex of the petrous portion is received in the interval between the spinous process of the sphenoid bone and the anterior part of the occipital bone. Of the three surfaces of the petrous portion, the anterior forms part of the middle cerebral fossa; the posterior forms part of the cerebellar fossa ; and the inferior surface is directed downward. The anterior surface is an inclined plane with its inner end impressed by the semilunar ganglion of the trifacial nerve, and its upper part ren- dered prominent by one of the semicircular canals of the labyrinth. Its inner third presents an inconspicuous narrow groove, 6 leading outwardly to a small foramen, 7 which communicates with the Fallopian canal, and transmits a branch of the pterygoid nerve. Below the groove are one or two smaller foramina, 8 likewise intended for the transmission of nerves. The posterior surface also forms an inclined plane. At its inner third is an oblique canal directed outwardly, the internal auditory mea'tus, 9 which transmits the auditory and facial nerve. The bottom 10 of the meatus is divided by a transverse ridge into two pits, in the upper one of which commences the Fallo'pian canal, 11 for the further passage of the facial nerve. The canal is at first directed forward, and then turns abruptly backward and outward at the upper part of the tym- panum, and subsequently descends to the stylo-mastoid foramen. The 1 Sulcus sinus transversi ; fossa sig- 7 Fallopian hiatus ; hiatus Fallopii ; moidea. hiatus canalis Fallopiae ; foramen Vidi- 2 F. mastoideum. ani; apertura spuria; for. Tarini; f. 3 Pars petrosa ; pars pyramidalis ; pe- anonymum Ferreinii. trous process ; os lapideum; o. durum; 8 Canaliculi petrosi. o. lithoides; o. saxeum; o. petrosum ; o. 9 Meatus auditorius internus; porus praeruptae rupi assimilatum; o. nervale. or sinus acusticus int. 4 See Organ of Hearing. Macula cribrosa. 5 Meatus auditorius externus. n Canalis Fallopiae; aqueductus Fal- 6 Semicanalis nervi Vidiani. lopise ; can. facialis. 64 THE SKELETON. FIG. 41. other portions of the bottom of the internal auditory meatus transmit the divisions of the auditory nerve to the labyrinth, in a manner more particularly described hereafter. 1 About the fourth of an inch external to the entrance of the meatus there is a short cleft, which communicates with a small foramen 2 for the transmission of a vein from the vestibule of the labyrinth. At the upper border of this surface is a groove 3 for conducting the superior petrosal sinus to the lateral sinus. The inferior surface of the petrous portion of the bone presents many points of interest. At its anterior outer part is the plate of bone which forms the aud'itory proc'ess, 4 defined above by the glenoid fissure, and below by a sharp crest named the vag'inal process, 5 which partly ensheathes the base of the sty'loid proc- ess. 6 The latter is a tapering spine, of variable length, projecting downward, forward, and in- ward, and connected to the hyoid bone by means of a round, fibrous cord, the stylo-hy'oid lig'a- ment. Between the styloid and mastoid processes is the sty'lo-mas'toid fora'men, 7 which is the termination of the Fallopian canal, and gives exit to the facial nerve. Behind the styloid process is a surface tipped with cartilage, the artic'ular process, which joins the transverse process of the occipital bone. To the inner side of this surface is a concave depression, the ju/gular fos'sa, 8 in which the internal jugular vein commences. To the inner side of the fossa is a notch, part of the jugular foramen, containing a three-sided pit, at the bottom of which is a foramen 9 for the transmission of a vein from the cochlea of the labyrinth. INFERIOR VIEW OP THE LEFT TEMPORAL BONE. 1, squamous por- ' tiou; 2, mastoid portion; 3, pe- trous portion ; 4, border articulat- ing with the great wing of the sphenoid bone ; 5, zygomatic proc- ess; 6, glenoid cavity; 7, glenoid tubercle; 8, glenoid fissure; 9, ex- ternal auditory meatus; 10, mas- toid process; 11, digastric groove; 12, styloid process; 13, stylo-mas- toid foramen; 14, jugular fossa; 15, pit which transmits a vein from the cochlea of the vestibule; 16, position between which and the occipital bone the ninth, tenth, and eleventh cerebral nerves escape from the cavity of the cranium; 17, articular process; 18, vaginal process; 19, 20, en- trance and exit of the carotid ca- nal; 21, Eustachian tube; 22, mastoid foramen. 1 See Organ of Hearing. 2 Aqueductus vestibuli. 3 Sulcus petrosus superior. 4 Processus auditorius. 5 Processus vaginalis. 6 P. styloideus. 7 F. stylo-mastoideum. 8 Fossa jugularis ; thimble-like cavity. 9 Aqueductus cochleae. THE SKELETON. 65 Below the notch is the entrance of the carot/id canal, 1 which ascends and then turns at a right angle forward and inward to the apex of the petrous portion of the bone, and transmits the internal carotid artery to the cavity of the cranium. In the crest, which separates the jugular fossa and carotid canal, is a small foramen, 2 which transmits the tympanic branch of the glosso- pharyngeal nerve to the tympanum. The anterior border of the petrous portion, in the notch separating it from the squamous portion, exhibits the irregular orifice of a canal, which communicates with the tympanum and is divided into two parts by a par- tition. 3 The upper division 4 of the canal accommodates the tensor muscle of the tympanum, and the lower one forms part of the Eusta'- chian tube. 5 STRUCTURE AND ARTICULATION OF THE BONES OF THE CRANIUM. The bones of the cranium, excepting when they are especially thin, as in the case of the ethmoid bone, the orbital plates of the frontal bone, the squamous portion of the temporal bone, and the cerebellar fossae of the occipital bone, are composed, as in the case of tabular bones gener- ally, of two layers of compact substance, with an intervening spongy sub- stance. 6 The outer table of compact substance is much more tenacious than the inner one, which from its comparative brittleness has received the name of the vitreous table. The spongy substance varies in the extent of its development in different individuals and races ; and gener- ally it is more abundant in the negro than in the white race. The bones of the cranium are nearly all united by suture. Before puberty, the basilar process of the occipital bone articulates with the body of the sphenoid bone, by means of fibro-cartilage, which speedily ossifying, unites the two bones into one piece. The transverse process of the occipital bone is connected with the articular process of the temporal bone by cartilage, which likewise speedily ossifies. The anterior border of the petrous portion of the temporal bone is simply coadapted with the posterior border of the great wing of the sphenoid bone ; but its apex and posterior border, as far as the jugular foramen, are united with the contiguous borders of the sphenoid and occipital 1 Canalis caroticus. * Semicanalis tensoris tympani. 2 Canaliculus tympanicus. 5 Bony portion of the Eustachian tube. 3 Processus cochlearifonnis. 6 Dipke ; diploic structure, 66 THE SKELETON. bones, by fibro-cartilage, which ordinarily remains to a late period of life. In all other instances, the cranial bones are united by suture, generally of the dentated or serrated variety, in which the contiguous borders of the bones are jagged, and mutually knit together in such a manner as frequently to require considerable force to separate them. The remaining sutures are of the squamous, or scale-like variety, in which the contigu- ous borders of the bones are beveled off, roughened, and mutually coadapted. The bones of the cranium are, however, not merely conjoined by suture th#y are actually continuous through intervening cartilage ; for if an unmacerated cranium be treated with muriatic acid, so as to remove the calcareous salts, the sutures disappear, and the cranium remains as a flexible case of bone-cartilage. The principal sutures of the cranium are the fronto-parietal, 1 the inter-parietal, 2 the occipito-parietal, 3 and occipito-temporal, 4 which are of the dentated or serrated variety; and the temper o-parietal, 5 and spheno-parietal, which are of the squamous variety. The spheno-tem- poral, spheno-frontal, and fronto-ethmoida! partake of both the den- tated and squamous character. The sutures of the cranial vault are remarkable for their exceedingly intricate and winding course, which has always rendered them one of the most striking characters in the anatomy of the skull. This intricacy is, however, confined to the exterior of the cranium, for it extends only through the outer layer of compact substance of the bones. In the interior of the cranium the same sutures present a merely waving, or slightly tortuous course. In early life, the sutures are less intricate than later ; and after the brain has reached its full development and growth, they gradually become more or less completely obliterated by the ossification of the intervening cartilage. This obliteration usually commences with the occipito-temporal suture, then occurs with the inter-parietal, then the fronto-parietal, and afterwards the occipito-parietal suture. Occasionally the inter-parietal suture ossifies at a comparatively 1 Coronal suture ; sutura coronalis ; 5 Squamous suture ; s. squamosa ; s. s arcualis. mendosa ; s. lepidoides. The part of the 2 Sagital suture; sutura biparietalis ; suture which is not squamous and unites 8. virgata ; s. rhabdoides; s. jugalis. the parietal bone with the mastoid por- 3 Lambdoidal suture; s. lambdoidalis ; tion of the temporal bone is the addita- s. occipitalis. mentum suturce squamosse. 4 Additamentum suturje lambdoidalis. THE SKELETON. tfj early period, when, in consequence of the subsequent growth of the brain being less retarded antero-posteriorly, the cranium becomes more elongated than usual. The frontal bone at birth consists of two distinct pieces united in the median line. The two pieces usually co-ossify before the third year of infantile life, but occasionally remain connected by serrated suture. In such cases the front'al suture is apt to be among the most perma- nent. GENERAL CONFORMATION OF THE CRANIUM. ' The Cra'nium 1 is egg-shaped or ovate ; the long diameter being antero-posterior, and the narrow extremity forward. It is moulded upon its contents, so that its interior surface presents impressions cor- responding with the form of the brain, and grooves corresponding with the sinuses and arteries of the dura mater. Its exterior, however, is not the exact counterpart of the interior, so that even if the different facul- ties of the brain were localized, as pretended by phrenologists, they could not be accurately determined by an examination of the cranium. Most of the perceptive faculties indeed would have nothing to do with the brain, if they were situated, as phrenologists have placed them, over the position of the vacant spaces constituting the frontal sinuses. The interior surface of the vault or top of the cranium is marked by the cerebral convolutions. Along its median line may be observed the shallow groove impressed by the course of the longitudinal sinus. On each side of the position of this groove, more especially on the parietal bones, irregular depressions, resembling ulcerations, are not unfrequently observable. These are the result of absorption from the pressure of certain anomalous deposits of the membranes of the brain, called Pac- chionian bodies. The bottom of the cavity of the cranium presents three pairs of well- marked fossae. The anterior cranial fossae 2 accommodate the anterior cerebral lobes, and correspond with the roofs of the orbits. They are formed by the orbital plates of the frontal bone, strongly marked by cerebral convolutions, and the small wings of the sphenoid bone, which constitute their posterior boundary. Between them projects the eth- moidal crest, separating on each side the ethmoidal gutters, for the lodg- ment of the olfactory bulbs. 1 The cranium proper; the brain pan ; 2 Fosses anteriores basis cranii ; f. ce- brain case ; cranion ; scaphion ; con- rebrales anteriores. chus ; theca cerebri ; ollacapitis. 68 THE SKELETON. The middle cranial fossae, 1 FIG. 42. INTERNAL VIEW OF THE BASE OF THE CRANIUM OF THE LEFT SIDE, a, I, c, an- terior, middle, and posterior cranial fossae ; 1, orbital plate of the frontal bone; 2, small wing of the sphenoid bone; 3, great wing of the same; 4, squamous portion of the temporal bone ; 5, petrous portion of the same ; 6, inastoid portion ; 7, parietal bone; 8, occipital bone; 9, ethmoidal gutter and ethmoidal crest; 10, pituitary fossa ; 11, an- terior clinoid process ; 12, declivity ; 13, oc- cipital foramen ; 14, optic foramen ; 15, ro- tund foramen ; 16, oval foramen ; 17, spin- ous foramen and groove from it, indicating the course of the great meningeal artery; 18, lacerated foramen 19, internal audit- ory meatus ; 20, jugular foramen; 21, con- dyloid foramen ; 22, commencement of the groove for the lateral sinus. The course of the groove is observed along the horizontal limb of the occipital crest, the posterior inferior angle of the parietal bone, the mastoid portion of the temporal bone, and the transverse process of the occipital bone, terminating at the jugular foramen. which receive the middle cerebral lobes, are formed by the great wings of the sphe- noid bone, the squamous portions of the temporal bones, and the anterior surfaces of the petrous portions of the latter. Their anterior boundary is the sharp crescentric border of the small wings of the sphenoid bone, and their posterior boundary the upper border of the petrous portion of the temporal bones. They intercommuni- cate through the pituitary fossa. Between the apex of the petrous por- tion of the temporal bone and the body and great wing of the sphenoid bone, there is a large irregular aperture, the lacerated fora'men, 2 which is closed be- low by a thin plate of cartilage, but is occupied at the upper part of its area by the internal carotid artery, as it proceeds from the carotid canal to the side of the body of the sphenoid bone. From the spinous foramen, the groove for the middle meningeal artery ascends a short distance near the anterior border of the squamous portion of the tem- poral bone, when it divides into two branches. One of these continues along the squamous portion of the bone to its back part, when it mounts upon the parietal bone, subdividing in numerous branchlets. The other branch turns over the summit of the great wing of the sphenoid bone, and then, like the preceding, ascends on the parietal bone. The posterior cranial fossae, 3 more capacious than the others, receive the lobes of the cerebellum. They are formed by the posterior surfaces of the petrous portions of the temporal bones, the mas- toid portions of the latter, and the occip- 1 F. med. basis cranii ; f. cereb. med. 2 Foramen lacerum ; f. lacerum medius. 3 F. post, basis cranii; f. cerebelli. THE SKELETON. 69 ital bone below the lateral limbs of the occipital cross. They are sepa- rated posteriorly by the vertical limb of the latter, and anteriorly com- municate through the inclined surface of the declivity of the sphenoid bone and the basilar process, upon which rest the medulla oblongata and the pons. From the groove for the longitudinal sinus, that for the lateral sinus may be seen following the course of the horizontal limb of the occipital cross, then curving down upon the mastoid portion of the temporal bone, and over the transverse process of the occipital bone to the jugular fora- men. Usually the groove upon the right side is larger than that upon the left. The ju/gular fora'men 1 is an irregular orifice formed by the con- tiguity of two notches between the petrous portion of the temporal bone and the occipital bone. It is usually more or less subdivided by a short process projecting from near the middle of the notch of the petrous portion of the temporal bone. The outer and larger division admits of the termination of the lateral sinus in the internal jugular vein, and the inner division transmits the ninth, tenth, and eleventh cranial nerves. In accordance with the usually larger size of the right lateral sinus than the left one, the right jugular foramen and the right internal jugular vein are also larger than those of the left side. The external surface of the vault of the cranium, 2 covered by the scalp, is smooth ; and its front forms the forehead, its back the occiput, and its sides contribute to the temporal fossae. 3 The latter give origin to the temporal muscles, and are defined above by a superficial ridge or line commencing at the external angular process of the frontal bone, and arching upward and backward upon the parietal bone to the divid- ing line between the squamous and petrous portions of the temporal bone. Inferiorly the temporal fossa is defined by a ridge proceeding inward and forward from the root of the zygomatic process of the tem- poral bone, and becoming continuous with another dividing the external surface of the great wing of the sphenoid bone into two parts. The exterior of the base of the cranium is exceedingly irregular. Transverse lines directed from external conspicuous points would indi- cate important parts as follows : 1. A line between the ends of the mastoid processes would pass nearly through the middle of the occipital foramen. 2. A line between the external auditory meatuses would pass through the jugular foramina and the anterior part of the occipital foramen and condyles. 1 F. jugulare ; f. lacerutn posterius. 2 Skull cap ; calvaria ; calva; camera. 3 Fossae temporales. 70 THE SKELETON. 3. A line between the glenoid cavities would pass through the entrance of the carotid canals. 4. A line between the glenoid tubercles would pass through the exit of the carotid canals and the lacerated fora- mina. 5. A line between the middle of the zygomat- ic processes of the tem- poral bones would pass through the roots of the pterygoid processes which separate the oval foramina and the pos> terior nares. The occipital con- dyles, by which the skull is supported on the vertebral column, are placed posterior to the middle line of the cranium. The posterior ob- lique border of the great wing of the sphen- oid bone forms, with the contiguous border of the petrous portion of the temporal bone, a groove which accommodates the inferior portion of the Eustachiau tube. FlG. 43. EXTERNAL VIEW OF THE BASE OF THE SKULL, RIGHT SIDE. 1, palate plate of the superior maxillary bone ; 2, palate plate of the pal- ate bone; 3, vomer; 4, 5, internal and external pterygoid processes; 6, pyramidal process of the palate bone ; 5, 6, occupy the pterygoid fossa ; 7, under part of the great wing of the sphenoid bone, form- ing part of the spheno-maxillary fossa ; 8, temporal surface of the great wing of the sphenoid bone ; 9, zygoma; 10, zygomatic process of the malar bone ; 11, zygomatic process of the temporal bone; 12, squamous portion of the temporal bone; 13, glenoid tubercle; 14, glenoid fossa; 15, auditory and vaginal process ; 16, styloid proc- ess; 17, external auditory mea- tus ; 18, mastoid process ; 19, di- gastric fossa; 20, conjunction of the basilar process and body of the sphenoid bone ; 21, occipital condyle; 22, occipital protuber- ance, and crest leading from it downward; 23, 24, superior and inferior semicircular ridges; 25, occipital foramen ; 26, incisive for- amen; 27, posterior palatine for- amen ; 2S, spheno-maxillary fis- sure ; 29, posterior naris ; 30, oval foramen ; 31, spinous foramen ; 32, lacerated foramen; 33, Eustachian tube; 34, entrance of the carotid canal; 35, jugular foramen ; 36, stylo-mastoid foramen; 37, pit with a posterior coudyloid foramen ; 38, mastoid foramen. MECHANICAL CONSTRUCTION OF THE CRANIUM. A sphere is best adapted to resist pressure equally applied on all sides, and therefore of all abstract forms is the strongest. It or its modi- fications into the oval and ovate forms are constantly employed in the organic kingdom in the construction and protection of delicate structures, as instanced in the organic cell, the eggs of animals, etc. Under special circumstances the oval or ovate forms are better adapted to the preservation of delicate structures than the perfect sphere. THE SKELETON. 71 FIG. 44. The human cranium, especially adapted to the protection of the brain, is ovate, with the narrow end strongest and situated forward, where it is most liable to violence. The cranium of the infant varies, from the more mature ovate form, in presenting a number of prominent points in positions liable to receive pressure during birth, or subsequently to receive the first impression from falls or blows. Prior to co-ossification of the bones of the cranium, they are so inti- mately and admirably articulated, that it requires considerable force to separate any one of them, but after this is done the connection of the whole becomes more or less enfeebled. The sphenoid bone is the most important agent of connection of the bones of the cranium ; extending transversely across the base of the latter it articulates with all the other bones and its body appears to be a central point of support for the whole of them. If sections are made in different directions through the cranium, they will exhibit the intimate rela- tionship existing in the con- nection of the bones by which so many pieces are enabled to preserve the integrity of the cranium. Thus a vertical antero-pos- terior section of the cranium exhibits a connection of its segments, as represented in figure 44. The upper border of the frontal bone rests upon the beveled COntigUOUS bor- ANTERO-POSTERIOR SECTION OF THE CRANIUM, exhibiting rlor. ^f fliA T^ariofnl hnnpc the mode by which the connection of the different bones con- 6S ' tributes to preserve its integrity. 1, parietal bone ; 2, front- these behind abut against al bone ; 3, its orbital plate ; 4, frontal sinus ; 5, body of the OCCipital bone, and the 8 P henoid bone '> 6 > sphenoidal sinus; 7, occipital bone; 8, marginal ridge of the occipital foramen. circle, after bifurcating and surrounding the occipital foramen, terminates in the basilar process, which is firmly supported against the body of the sphenoid bone. The latter by its lesser wings affords a support to the orbital processes of the frontal bone, and thus the circle is completed. A horizontal circle of the cranium, as represented in figure 45, exhibits the borders of its frontal segment overlapped by the parietal segments, and these likewise slightly overlapped by the occipital segment. A circle lower down will exhibit the frontal segment overlapped by the great wings of the sphenoid bone, and these by the squamous portions 72 THE SKELETON. FIG. 45. of the temporal bones, which likewise behind inclose the parietal bones, also slightly overlapped by the occipital bone. A vertical transverse circle at the front of the cranium, as represented in figure 46, exhibits a frontal arch inter- locked by the sphenoid bone. A second circle a short dis- tance behind the preceding, as represented in figure 4T, exhibits the parietal bones dove-tailed above, and in- terlocked by the sphenoid bone below. A third circle further back, as represented in figure 48, exhibits the parietal bones articulating as in the pre- ceding instance, and interlocked below by the temporal bones, which abut against the sphenoid and occipital bones. HORIZONTAL SECTION OF THE CRANIUM. 1, frontal bone 2, parietal bone ; 3, occipital bone. FIG. 46. FIG. 47. TRANSVERSE SECTION THROUGH THE FRONT OF THE CRANIUM. 1, transverse arch formed by the frontal bone ; 2, great wing of the sphenoid bone, includ- ing or overlapping the abutments of the frontal arch ; 3, body of the sphenoid bone, with its sinuses. TRANSVERSE SECTION IN ADVANCE OF THE MIDDLE OF THE CRANIUM. 1, parietal bone forming with its fellow an arch ; 2, great wing of the sphenoid bone ; 3, horizontal portion of the wing ; 4, body, with the sphenoidal sinuses. A fourth circle at the back of the cranium, as represented in figure 49, exhibits the parietal bones joined as in the two preceding instances, and fitting into a notch below, between the squamous and mastoid portions of the temporal bones, which, as before stated, abut against the sphenoid and occipital bones. THE SKELETON. 73 FIG. 48. FIG. 49. TRANSVERSE SECTION THROUGH THE MIDDLE OP THE CRANIUM. 1, parietal bone ; 2, squamous por- tion of the temporal bone ; 3, petrous portion ; 4, body of the sphenoid bone. TRANSVERSE SECTION POSTERIOR TO THE MIDDLE OP THE CRANIUM. 1, back part of the parietal bones ; 2, mastoid portion of the temporal bone ; 3, mastoid process with the sinuses ; 4, petrous por- tion of the temporal ; 5, sphenoidal body, or the basilar process of. the occipital bone. DEVELOPMENT OF THE CRANIUM. The occipital bone is developed from seven distinct centres of ossifica- tion : four for the expanded portion, and three for the lower portion. At birth it consists of three pieces : the upper expanded portion, 1 the two condyloid portions, 2 and the basilar portion. 3 They usually become united into one piece by the fifth or sixth year. The sphenoid bone is developed from twelve ossific centres, including the formation of the sphenoidal sinuses from the ethmoidal pyramids. At birth it consists of three pieces : the body and small wings as one, and the great wing and pterygoid processes making one on each side. Subsequently, during the first year, the three pieces are united into one. The ethmoidal pyramids become the sphenoidal sinuses on the approach of puberty. The ethmoid bone is developed from five centres of ossification, exclu- sive of the pyramids. At birth, its two lateral masses only are ossi- fied, but during the first year the vertical and cribriform plates ossify and become united with the former. The frontal bone is developed from two ossific centres, which corre- spond with the supra-orbital ridges. At birth it consists of two halves united at the median line. They usually co-ossify before the third year ; but occasionally the suture remains as one of the least disposed to obliteration. 1 Supra-occipital bone; inter-parietal bone ; squama occipitalis. 2 Exoccipitals ; lateral occipitals. 3 Basioccipital bone; basilar bone; inferior occipital bone. 74 THE SKELETON. The parietal bones are each developed from a single centre of ossifica- tion, corresponding with the parietal protuberance. The temporal bones are each developed from four ossific centres : one for the squamous portion, one for the combined petrous and mastoid portions, one for the auditory process, and one for the styloid process. At birth it usually consists of three pieces : the squamous portion as one, the petrous and mastoid portions as a second, and the auditory process as a third, which then appears as a ring of bone, incomplete at its upper part, and encircling the tympanic membrane. The three pieces speedily unite after birth, and the ring of bone encircling the tympanic membrane gradually elongates outward into the external auditory meatus. The styloid process subsequently ossifies, TWO PIECES OF THE TEMPORAL BONE, . . , /> i i -i a* observed about the period of Vari6S m lts de g ree f development, and birth; the third piece corresponding sometimes never unites with the temporal with the petrous and mastoid por- -, tions, not represented. 1, the squa- mous portion of the temporal bone; The tabular bonCS of the Vault Of the Cl'a- t the P eriod of birth > P resent the a P- pearance of depressed cones ; being conspicu- ously prominent at their centres, which correspond with the frontal, parietal, and occipital protuberances. From the summits of the cones the ossific structure radiates in well-marked lines to the borders of the bones, which overlap instead of interlocking with each other, as they do subsequently. The parietals overlap both the frontals and the occipital. From this arrangement of the vault of the cranium, compression may reduce its diameters, which is an important provision in the passage of the head of the child through the pelvis of the mother. The bones at the base of the skull meet at their borders without overlapping so as not to permit diminution from pressure, which is not only unnecessary from the small size of the base compared with the vault, but which would prove inju- rious to the parts of the brain concerned in this position. At or near the period of birth, there are several membranous spaces left in the line of the sutures, through which ossification has not extended, and which are named font/anels, 1 The largest of these interspaces, the anterior font'anel, 2 is situated at the contiguous angles of the two frontals with the two parietal bones. It is quadrangular, with the anterior angle much prolonged and acute, and the posterior short and 1 Fontanellee ; fonticuli ; lacunae. fons pulsatilis ; vertex palpitans ; fonti- 2 Great, sincipital, or frontal fontanel ; culus quadrangularis. THE SKELETON. 75 obtuse. It remains unossified for several months after birth; and at the membranous space, the pulsations of the brain may be felt. The posterior fonl/anel, 1 situated between the parietal bones behind, is usu- ally closed at birth by the summit of the occipital bone. The anterior fontanel, and the posterior one, or the three sutures which lead to its position, afford important means to the midwife in determining the relative position of the head of the child while within the pelvis of the mother. At the sides of the cranium are the lateral font'anels, of which one is situated between the frontal, temporal, parietal, and sphenoid bones, 2 and the other is placed between the occipital, temporal, and parietal bones. 3 The bones of the foetal cranium consist of a single layer of compact substance ; the spongy substance being developed in them subsequent to birth. The frontal and mastoid sinuses are developed by a resolution of the spongy substance. SUPERNUMERAKY BONES OF THE CRANIUM. Not unfrequently there are found in the course of the sutures of the cranium supernumerary, islet-like bones, 4 which have originated frf>m distinct centres of ossification. They rarely occur in any other than the sutures of the vault of the cranium, and of these are most frequent in the course of the occipito-parietal suture. These bones vary much in number and size ; and in hydrocephalic cases are often numerous and large. Frequently they may be found on the two sides of the cranium, alike or symmetrical in position. Occasionally one 5 is found occupying the former position of the anterior fontanel. BONES OF THE FACE. Of the fourteen bones of the face, twelve are in pairs : the superior maxillary, palate, lachrymal, nasal, turbinated, and malar bones; the remaining two are single and symmetrical : the vomer, situated in the par- tition of the nose, and the inferior maxillary bone. 1 Small, bregmatic, or occipital font- 4 Ossa inlercalaria; o. suturarum; o. anel. Wormiana; o. triquetra; o epactalia; o. 2 Sphenoid fontanel. raphogeminantia ; o. triangularia Blasii; 3 Mastoid fontanel ; fonticulus mas- claves calvariae. toideus ; f. Casserii. 5 Os antiepilepticum. 76 THE SKELETON. THE SUPERIOR MAXILLARY BONE. The Superior Max'illary bone 1 forms with its fellow the upper jaw, and contributes in the construction of the roof of the mouth, the nasal fossae, the orbits, the cheeks, and the spheno-maxillary fossa3. SUPERIOR MAXILLARY BONE OF THE LEFT SIDE, outer view. 1, body; 2, tuberosity; 3, alveolar border; 4, orbital plate; 5, nasal process; 6, nasal notch; 7, nasal spine; 8, lachrymal groove; 9, en- trance of the infra-orbital canal ; 10, infra-orbital foramen ; 11, orifices of the posterior dental canals ; 12, malar process ; 13, articulation for the internal angular process of the frontal bone; 14, incisor teeth; 15, canine tooth; 16, premolar teeth; 17, large molar teeth. SUPERIOR MAXILLARY BONE OF THE LEFT SIDE, inner view. 1, nasal surface of the body ; 2, sur- face for the palate bone ; 3, alveolar border ; 4, orb- ital plate ; 5, nasal process ; 6, ridge for the articu- lation of the turbinated bone ; 7, nasal spine ; 8, groove contributing to form the lachrymo-nasal duct; 9, maxillary sinus; 10, palate plate, its ar- ticulating border for the right maxillary bone ; 11, incisive foramen continuous with the naso-palatine canals ; 12, tuberosity ; 13, articular extremity for the internal angular process of the frontal bone; 14. incisor teeth; 15, canine tooth; 16, premolar teeth ; 17, large molar teeth. The body of the bone, independent of its processes, is wedge-shaped, and is hollowed into a large cavity, the max'illary si'nus, 2 which com- municates, by a large irregular orifice, through the inner wall, with the nasal fossa. Above the orifice just mentioned, the inner surface of the body articulates with the lachrymal and ethmoid bones, and behind it, with the palate bone. The anterior surface of the body, forming part of the cheek, is depressed 3 and is bounded above by the infra-orbital margin. Just 1 Os maxillare superius ; upper jaw- bone ; maxilla sup. ; mandibula sup. ; maxilla syncrania. 2 S. maxillaris ; antrum Highmoria- num ; nntrum of Highmore ; genyan- trum ; gnathantrum; sinus genge pitui- tarius; antrum genae. 3 Fovea maxillaris ; canine fossa. THE SKELETON. 77 below the latter is the in'fra-orb'ital fora'men, 1 which transmits the infra-orbital nerve and blood-vessels. The posterior convex surface of the body constitutes the tuberos'ity, 2 and contributes to form the spheno-maxillary fossa. It presents a per- forated surface ; and several of the larger orifices are the commencement of the posterior dent'al canals', 3 which are narrow passages transmit- ting nerves and arteries to the molar teeth. The upper surface of the body, or orb'ital plate, 4 forms the floor of the orbit, and terminates behind in an obtuse border, which is the lower boundary of the spheno-maxillary opening. From the latter border, the infra-orb'ital canal' 5 proceeds forward in the orbital plate, and term- inates at the corresponding foramen. From the canal two fine passages, the anterior dent'al canals', 6 descend in the outer wall of the body, and conduct arteries and nerves to the anterior teeth. Both the anterior and posterior dental canals are partially visible within the maxillary sinus. At the lower part of the superior maxillary bone is the thick pyra- midal ridge, called the alve'olar border, 7 which arches from behind for- ward and inward, and projects obliquely downward and outward. The free margin presents the orifices of a number of deep conical pits, the alve'oli, 8 or sockets for the insertion of the teeth. The outer surface of the border is marked by alternating vertical ridges and depressions, cor- responding with the alveoli and their intervals. The posterior extremity of the border is rough, and abuts against the pyramidal process of the palate bone. The anterior extremity is likewise rough, and articulates with the corresponding border of the opposite bone. Above the anterior extremity of the alveolar border is a pointed process, the na'sal spine, 9 prolonged backward into a ridge, to which the cartilage of the partition of the hose is attached. To the outer side of the spine is a concave notch, which forms part of the anterior nasal orifice. The margin of the na'sal notch in the white race is usually acute, but is rounded off to the anterior surface of the alveolar border in the black race. Above the notch just mentioned is a plate of bone, the na'sal proc'ess, 10 1 F. infra orbitale. 7 Processus, or limbus alveolaris. 2 Tuberositas maxillaris. 8 Alveoli dentis ; cavernae dentium ; 3 Canales, or canaliculi alveolares, or odontobothria ; mortarioli. dentales posteriores. 9 Spina nasalis ; s. nasalis anterior. * Planum orbitale. w Processus nasalis ; p. frontalis ; p. 5 Canalis infra-orbitalis. ascendens. 6 Canalis alveolaris, ordentalismedius et anterior. 78 THE SKELETON. which extends upward to join the internal angular process of the frontal bone. Its outer surface forms part of the side of the nose ; and its inner surface, directed toward the cavity of the latter, is concave and bounded below by a ridge for the attachment of the turbinated bone. Its ante- rior border is thick and rough for junction with the nasal bone. Its pos- terior border joins the lachrymal bone, and is grooved to form part of the naso-lachrymal canal. From the internal part of the base of the alveolar border there pro- jects horizontally inward, the pal'ate plate, 1 which contributes to form the roof of the mouth and the floor of the nose. Its nasal surface is smooth and concave ; and its oral surface, continuous with the inner one of the alveolar border, is vaulted and rough. Its inner border rises into a ridge which articulates with the vomer, and forms a thick rough surface for junction with that of the opposite bone. The posterior border is thin and rough, and joins the palate bone. From the outer part of the body there projects a strong protuberance, the ma'lar proc'ess, 2 which presents a large trilateral roughened surface for the support of the malar bone. Between the anterior extremity of the alveolar border and the palate plate of the superior maxillary bone, the na'so-pal'atine canal' 3 descends from the nasal fossa, and, converging, forms with that of the opposite bone, in the intermediate suture, the anterior pal'atine fora'men. 4 From the canal and foramen a fine fissure may be traced a short distance outwardly, which is a vestige of the separation, existing in other mammals, of that portion of the bone containing the incisive teeth, and called the intermaxillary bone. The representative of the latter is ob- scurely indicated in the human embryo prior to the third month ; the line of its separation dividing off the incisive portion of the alveolar border and the lower third of the nasal process. THE PALATE BONE. The Pal/ate bone 5 is situated at the back part of the superior max- illary bone, between it and the sphenoid bone. It contributes, with its fellow, to form the mouth, nasal fossae, and orbits. It has the outline of the letter L, consisting of a horizontal and vertical plate, together with smaller processes. 1 P. palatinus. 4 F. palatinum anterius ; f. incisivum ; 2 P. zygomaticus. f. alveolare anterius ; f. coecum. 3 Canalis, or ductus naso-palatinus, 5 Os palatinum ; o. palati. or incisivus. THE SKELETON. 79 The horizontal or pal'ate plate 1 is square, and contributes a smooth concave surface to the floor of the nose, and a smaller surface to the hard palate. Its inner border rises into a crest 2 and articulates with that of FIG. 53. POSTERIOR VIEW OF THE RIGHT PALATE BONE. 1, palate plate; 2, nasal plate; 3, pyramidal process; 4, articular border for the left palate bone; 5, palate spine; 6, ridge for junction with the turbi- nated bone ; 7, spheno-palatiue notch, between 8, the orbital, and 9, the sphenoidal process; 10, groove for the internal pterygoid process of the sphenoid bone ; 11, position of the posterior palatine fora- men. EXTERIOR VIEW OF THE RIGHT PALATE BONE. 1, rough surface articulating with the superior maxillary bone, and diminishing the aperture of the maxillary sinus ; 2, posterior palatine canal ; completed by the tuberosity of the superior max- illary bone ; 3, spheno-palatine notch ; 4, 5, 6, orb- ital process; 4, surface directed toward the ptery- go-maxillary fossa; 5, orbital surface ; 6, maxillary border ; 7, sphenoidal process ; 8, pyramidal process. the opposite side; the crests of the conjoined palate plates aiding in the support of the vomer, and projecting backward into a pointed process, the palate spine. 3 The anterior border of the palate plate articulates with that of the superior maxillary bone ; and the posterior crescentic border has the soft palate attached to it. The vertical or na'sal plate 4 is thinner than the other, and extends from it to the base of the cranium. Its inner or nasal surface is divided into two parts by a horizontal ridge, 5 with which the turbinated bone articulates. Its outer surface is divided by a vertical ridge bounding a groove, 6 which, by the approximation of the sphenoid and superior max- illary bones, is converted into the posterior pal'atine canal V descend- ing from the pterygo-maxillary fossa to the hard palate. The posterior portion of the outer surface of the nasal plate articulates with the in- ternal pterygoid process, and the anterior portion with the maxillary bone, partially closing the entrance of the maxillary sinus. 1 Pars palati ; p. horizontalis. 2 Crista nasalis. 3 Spina palatina ; s. nasalis posterior. 4 Pars nasalis ; p. perpendicularis. 5 Crista turbinalis ; c. t. inferior. 6 Sulcus pterygo-palatinus. T Canalis palatina posterior ; c. ptery- go-palatina. 80 THE SKELETON. At the .upper border of the nasal plate is a large, round notch, which, in conjunction with the under part of the body of the sphenoid bone, is converted into the sphe'no-pal'atine fora'men 1 communicating from the pterygo-maxillary fossa with the nasal fossa. Behind the notch just mentioned is the sphenoid'al proc'ess, 2 which articulates with the under part of the body of the sphenoid bone. In the upper border of this process is a groove, which, in conjunction with the latter bone, is converted into the pter'ygo-pal'atine canal'. 3 In advance of the notch indicated, is the orVital proc'ess, 4 which is received between the orbital plates of the superior maxillary and ethmoid bones at the posterior inferior part of the orbit, where it closes the poste- rior ethmoidal sinuses. At the posterior angle of conjunction of the nasal and palate plates of the palate bone, there projects the pyramidal proc'ess, 5 which occu- pies the notch of the pterygoid processes of the sphenoid bone. Some- times it completely incloses the lower part of the posterior palatine canal ; and not unfrequently it is pierced by one or two branches from the latter descending in the same direction. FIG. 55. THE LACHRYMAL BONE. The Lach'rymal bone, 6 the smallest of those of the face, is situated one at the fore part of the inner wall of each orbit. It contributes to form the latter, the lachrymo-nasal duct, the nasal fossa, and the anterior ethmoidal sinuses. It consists of a thin, oblong square plate, articulating above, behind, and below with the orbital plates of the frontal, ethmoid, and maxillary bones, and in front with the nasal process of the latter bone. The outer surface forms part of the inner wall of the orbit, and in advance contributes a fossa or groove 7 to the lach/rymo-na'sal duct. 8 The outer surface closes in the anterior eth- moidal sinuses. EXTERNAL VIEW OP THE RIGHT LACHRYMAL BONE. 1, orbital sur- face; 2, lachrymal fossa; 3, small process bounding the latter iufe- riorly; 4, frontal border; 5, eth- moidal border; 6, maxillary bor- der; 7, process articulating with the turbinated bone. 1 F. spheno-palatinum. 2 Processus sphenoidalis ; apophysis pterygoideus. 3 C. pterygo-palatina. 4 P. orbitalis. 5 Pterygoid process ; apophysis sphe- noidalis. 6 Os lachrymale ; os unguis ; ungui- form bone. 7 Lachrymal fossa. 8 Ductus ad nasum. THE SKELETON. 81 From the anterior inferior angle a process 1 projects downward, which joins with one from the turbinated bone, and serves to prolong the lach- rymo-nasal duct. THE NASAL BONE. The Na'sal bone 2 projects from the root of the nose downward and forward, and with its fellow, together with the nasal processes of the superior maxillary bones, forms the bridge of the nose. It is irregularly quadrate, and thicker and narrower above than below, and not unfrequently is so narrow as to assume a fan-like shape. In its length it presents a sigrnoid curve, though occasion- ally it is simply concave in this direction. The outer surface is smooth, transversely con- vex, and generally presents a small but con- spicuous foramen 3 near its middle. The inner surface, directed toward the corresponding na- f1$| sal fossa, is transversely concave, and presents Lr ^ a longitudinal groove for the accommodation of a branch of the nasal nerve. ANTERI * TV"", 1E " NA ' SAL BONE. 1, frontal border ; 2, na- The Upper border Of the nasal bone is thick sal border; 3, maxillary border: and roughened for articulation with the frontal 4 ' lower border ; 5 ' nasal foramen ' bone ; the lower border is thin and notched, and forms the superior boundary of the anterior nasal orifice. The inner border is thick above, narrows off below, and conjoins with that of the opposite bone. The outer border is beveled off and overlapped by the corresponding border of the nasal process of the superior maxillary bone. THE TURBINATED BONE. The Tur'binated bone* is quite rudimentary in comparison with the corresponding one of most other animals, in which it often acquires an extraordinary degree of development, as the student may observe in any of the common carnivorous animals the cat, dog, weasel, bear, etc. It projects horizontally from the outer wall of the nasal fossa, and separates the middle and inferior meatus. The bone presents the form of an irregular scroll, with a rough convex surface directed toward the partition of the nose, and a con- 1 Hamulus lacbrymalis. * Os turbinatum ; o. t. inferius ; spongy 2 Os nasale ; os nasi. bone; o. spongiosum; concha inferior; c. 8 F. nasalis. veneris ; buccinum. 6 82 THE SKELETON. cave surface directed outwardly. FIG. 57. Its lower part is thick and spongy; its anterior extremity joins the transverse ridge at the root of the nasal process of the superior max- illary bone ; and its posterior nar- rower extremity articulates with a like ridge of the palate bone. From the middle of the upper border a hook-like plate 1 overhangs the inferior edge of the entrance to the maxillary sinus; and a small process 2 ascending from this plate diminishes the aperture of the lat- ter, and frequently joins a process from the ethmoid bone. In advance of the hook-like plate, another small process 3 ascends to join one from the lachrymal bone, and assists in the formation of the lachrymo-nasal duct. EXTERNAL VIEW OF THE RIGHT TCRBINATED BO\E. 1, anterior extremity articulating with the superior maxillary bone ; 2, posterior extremity articulat- ing with the palate bone ; 3, hook-like plate over- hanging the lower border of the maxillary sinus. The process in advance of it above joins the lachry- mal bone to contribute in the formation of the lachrymo-nasal duct. 4, inferior, obtuse border. FIG. 58. THE VOMER. The Vo'mer 4 is a lozenge-shaped plate of bone, situated at the back part of the partition of the nose. Its lateral surfaces form part of the inner wall of the nasal fossa?. The upper border is grooved to re- ceive the rostrum of the sphenoid bone, and its edges 5 are reflected to join a thin plate springing out of the root of the pterygoid processes. The lower border articulates with the crest formed at the conjunction of the palate plates of both the superior maxillary and palate bones. The anterior border is grooved to receive the cartilage of the nasal partition, and at its upper part ar- ticulates with the nasal plate of the ethmoid bone. The posterior bor- der is thin and crescentic, and forms the oblique line of separation of the posterior nasal orifices. LEFT SIDE OF THE VOMER. 1, 1, broad groove re- ceiving the rostrum of the sphenoid bone ; 2, 2, inferior border articulating with the palate plates of the superior maxillary and palate bones; 3, posterior border, the dividing line of the posterior Dares; 4, 4, grooved border receiving a narrow slip of cartilage, situated between the vomer and the nasal plate of the ethmoid bone ; 5, 5, border for the cartilaginous septum of the nose; 6, 6, na- sal surface. 1 Processus maxillaris. 2 P. ethmoidalis. 3 P. lachrymalis. 4 Osvomeris; aratrum. 5 Also vomeris. THE SKELETON. 83 THE MALAR BONE. The Ma'lar or cheek bone 1 forms the most prominent part of the cheek, and contributes to the construction of the orbit and temporal fossa. It is quadrangular, and rests by a broad, trilateral, rough surface upon the malar process of the superior maxillary bone. From the upper part a strong front/al proc'ess ascends to articulate with the external angular process of the frontal bone ; and from the back part projects a strong zygo- mat'ic proc'ess to articulate with the corresponding process of the temporal bone. The upper, anterior, concave bor- der forms the inferior and external margin of the orbit. From this border there proceeds backward and inward the orb'ital plate, which separates the orbit from the temporal fossa, articulates with the corresponding plates of the max- illary, sphenoid, and frontal bones, and contributes to the spheno-maxillary foramen. The posterior border of the bone, included between the frontal and zygomatic processes, is sigmoid, and gives attachment to the temporal fascia. The inferior border is convex and rugged, and contributes about one-half to the extent of the lower margin of the zygoma. The fa/cial surface, directed more or less outwardly and forward, is for the most part convex, and pretty constantly presents one or two con- spicuous foramina, which are continuous with canals 2 from the orbital and temporal surfaces. The temporal surface is concave, directed backward, and forms the anterior part of the temporal fossa. OUTER VIEW OF THE RIOHT MALAR BONE. 1, ex- ternal or facial surface; 2, malar foramen ; 3, front- al process; 4, 5, orbital border; 6, maxillary bor- der; 7, zygomatic process; 8, temporal border; 9, inferior border. THE INFERIOR MAXILLARY BONE. The Inferior Max'illary, or lower jaw bone, 3 is the second of the symmetrical bones of the face, in which it occupies the lower semi- 1 Os malare ; o. malse ; o. zygomat- icum ; o. jugale ; o. suboculare ; o. hypo- pium ; o. pudicum ; o. jugamentum ; o. genoe. 2 C. zygomaticus facialis, or tempo- ralis. 3 Maxilla inferior ; os maxillare infe- rius ; inferior maxilla ; mandibula. 84 THE SKELETON. FIG. 60. circumference. It is also the largest and strongest bone of the face, and is the only movable one of the skull. From the other bones of the face it is actually isolated through con- tact of the teeth, and it articulates with the cranium at the glenoid cavities of the temporal bones. It is divisible for description into the body, and rami or branches. The body is the curved portion of the bone supporting the teeth. Its outer surface is convex, and at the middle presents a prominent line, indicating the early separation of the bone into two pieces, and hence called the sym/physis. The prominent portion of the body in front is the chin, 1 which in the negro is vertical or even receding. Its lower protuberant part is the men'tal protu/berance, 2 on each side of which is the men'tal fora'men, 3 the termination of the inferior dental canal. The inner surface of the body presents at the lower part of the sym- physis the men'tal tu/bercle. 4 On each side, below the position of the molar teeth, is the oblique mo'lar ridge, 5 to which is attached the mus- cular floor of the mouth, Beneath the ridge the surface is slightly im- pressed by the position of the submaxillary gland, and the lower obtuse border of the bone is its base. The upper portion of the body forms its alve'olar border, 6 which is constructed on the same plan, and for the same purpose as in the superior maxillary bones. In relation with the corresponding part of the latter, it is usually vertical in position, though in the negro it is generally directed a little forward and upward. The ram'i 7 are the quadrate plates ascending from the posterior extremities of the body, reaching as high as the zygomatic arches. Their outer surface forms a nearly vertical plane. Near the middle of INFERIOR MAXILLARY BONE. 1, body ; 2, ramus ; 3, symphysis; 4, base; 5, angle; 6, mental fora- men ; 7, condyle ; 8, coronoid process ; 9, semilunar notch; 10, inferior dental foramen, the entrance of the corresponding canal; 11, alveolar border; 12, incisor teeth; 13, canine tooth ; 14, premolars ; 15, large molars. 1 Mentum. 2 Protuberantia mentalis. 3 F. mentale ; f. maxillare anterius. 4 Spina mentalis interna ; spinae men- tales; internal mental tubercle. 5 Mylo-hyoid ridge ; linea mylohy- oidea ; 1. obliqua interna. 6 Processus alveolaris. 7 The name rami is frequently applied by comparative anatomists to the two halves of the jaw. THE SKELETON. 85 the inner surface is the entrance 1 of the inferior dent/al canal', 2 which descends to the body of the bone and proceeds beneath the alveolar bor- der to terminate at the mental foramen. The entrance of the canal is bounded by a prominent crest, 3 which gives attachment to the spheno- maxillary ligament ; and below it, there descends a groove for the accom- modation of a small nerve. The posterior border of each rarnus is obtuse, and terminates below in the angle, 4 which is more or less obtuse in its relation with the base of the bone. The inner and outer surfaces of the angle are variably rugged, for the attachment of two of the masticating muscles. The anterior border of the ramus is sigmoid in its descent to the outer side of the body, where it terminates just exterior to the last tooth. The upper border of the ramus exhibits a large semilunar notch, 5 in advance of which is a flat conical eminence, th.e cor'onoid proc'ess, 6 into which the temporal muscle is inserted. Posterior to the notch is another process, which supports a transverse articular convexity, the con'dyle, 7 and its narrow part below constitutes the neck 8 of the jaw, the inner side of which presents a depressed surface, directed forward, for the attachment of the external pterygoid muscle. STRUCTURE AND ARTICULATION OF THE BONES OF THE FACE. The bones of the face are remarkable for their light and laminar char- acter, with the exception of the inferior maxilla, which is the stoutest and strongest bone of the skull, and contains within it, like most of the cra- nial bones, a quantity of spongy substance. All the bones of the face, except the lower jaw, are firmly and immov- ably articulated with one another and with the cranium. The face and cranium together constitute the skull, or bony portion of the head. Across the root of the nose, at the external angular processes of the frontal bone, and at the zygomatic arches, the face articulates by well- marked serrate sutures 9 with the cranium. Among themselves the bones of the face generally articulate by the mutual adaptation of more or less 1 Foramen maxillare internum ; infe- 5 Incisura semilunaris ; i. sigmoidea. rior dental foramen. 6 Processus coronoideus. 2 Canalis maxillaris ; c. alveolaris in- Condylus ; capitulum. ferior. 8 Cervix ; collum. 3 Lingula. 4 Angulus maxillae. 9 The transverse facial suture. 86 THE SKELETON. roughened borders. 1 The different sutures are named from the bones they connect, or from their position, and thus we have a na'so-front'al su/ture, an intermaxillary su/ture, a middle and transverse pal'ate su/ture, etc. THE TEMPEKO-MAXILLARY ARTICULATION. The movable articulation of the inferior maxillary bone is formed be- tween the condyle of the latter and the glenoid cavity and tubercle of the temporal bone, which are invested with cartilage. The motions of the lower jaw are as follows : 1. the opening and shutting of the mouth, in which the condyles roll on their axes in the glenoid cavities, as in the movement of a hinge ; 2. the movement of the lower jaw forward and backward, in which the condyles move forward from the glenoid cavities upon the glenoid tubercles and back again ; and 3. the movement from side to side, when the condyles move alternately and obliquely from the glenoid cavities to the glenoid tubercles and back again. The hinge-like or downward and upward movement of the lower jaw is the act of biting; the movements of the jaw forward and backward, and from side to side, are those of mastication or chewing. FIG. 61. FIG. 62. VERTICAL SECTION OP THE ARTICULATION OF THE EXTERNAL VIEW OF THE TEMPERO-MAXILLARY AR- LOWER JAW. 1, is placed above the glenoid cav- TICULATION. 1, zygoma; 2, glenoid tubercle, 3, ra- ity ; 2, glenoid tubercle ; 3, inter-articular cartilage mu8 o f the inferior maxillary bone; 4, mastoid dividing the joint into two cavities, 4 and 5 ; 6, an process; 5, external lateral ligament; 6, stylo- inter-articular cartilage separated from a joint, to maxillary ligament, a process of the cervical fascia, exhibit its form. The articulation of the lower jaw is rendered more movable by an in'terartic'ular fi'bro-car'tilage, 2 which is a discoidal plate horizontally dividing the joint into two cavities, each lined with a synovial mem- brane. The margin of the fibro-cartilage is thickened and attached to the capsular ligament; and it is signioid in section antero-posteriorly. It follows the movements of the condyle, and reduces the force of its impressions. 1 Suturse harmonise. 2 Cartilago-interarticularis. THE SKELETON. 87 FIG. 63. The cap'sular lig'ament, inclosing the joint, is thin and loose, and is attached above to the articular margin of the glenoid cavity and tubercle, and below to the neck of the lower jaw. The external lat'eral lig'ament 1 strengthens the former on the outer side of the joint. It consists of a short, strong band attached to the root of the zygomatic process, and extending downward and backward to the neck of the lower jaw. GENERAL CONFORMATION AND POSITION OF THE FACE. The Face is placed beneath the fore part of the cra'nium, together with which it forms the skull, as previously stated. In out- line it has the shape of a wedge-like segment from an oval figure. The rounded portion of the segment is formed by the front and sides of the face; the sectional surfaces are formed by the conjunction of the latter with the cranium and the base of the lower jaw; and the apex, which is truncated, is formed by the back borders of the rami of the lower jaw. The face is mainly consti- tuted of a series of receptacles for the accommodation and protection of the organs of sight, smell, taste, and others belonging to the commence- ment of the alimentary appa- ratus. In relation with the size of the cranium, it is smaller than in other mam- mals. In the white race it forms about one-fifth of the bulk Of the Skull, but in the onoid process ;?, neck supporting the condyle ; m, angle; n, inferior races is considerably lachr y m - nasal duct - larger. The greater its size in relation with that of the cranium, the THE SKULL, SEEN PARTLY IN FRONT AND ON THE RIGHT SIDE- 1, frontal bone; 2, parietal bone; 3, temporal bone, its squa- mous portion ; 4, the sphenoid bone, temporal surface of its great wing ; 5, ethmoid bone, its orbital surface ; 6, superior maxillary bone; 7, malar bone; 8, lachrymal bone; 9, nasal bone; 10, inferior maxillary bone, a, orbital plate of the frontal bone; ft, temporal surface; c, orbital surface of the great wing of the sphenoid bone; d. mastoid portion of the temporal bone; e, orbital surface of the malar bone; /, orb- ital plate of the superior maxillary bone ; g, infra-orbital foramen; h, mental foramen; t, symphysis;.;', ramus; k, cor- 1 Ligamentum maxilloB laterale externum ; membrana articularis ligamentosa. 88 THE SKELETON. less does it project in advance of the latter ; and with its proportionate diminution, as its front approaches a line vertical with the forehead, the nearer does it approximate the ideal standard of an intellectual coun- tenance. Hence the advancing forehead and retiring face are most striking features in the white race, especially in its more cultivated fami- lies ; while the prominent face, with large jaws, and receding forehead, are coexistent with the less intellectual character of the inferior races of men. The angle of inclination of the fore part of the skull is viewed to deter- mine the comparative degree of development of the face and cranium, and in some measure to form an estimate of the mental capacity of races and individuals. Though open to many objections, such as variations being produced in the angle, from the presence or absence of teeth, from the different degrees of development of the frontal sinuses, from projection of the forehead in hydrocephalus, or its depression by artificial means, yet independently of these and similar reasons, the fa'cial angle 1 is still looked upon, in some measure, as an index of intellectual character. The usual method of estimating the angle, is by drawing a line from the front of the forehead to the front of the upper jaw, and crossing this line by another proceeding from the latter position to the external auditory meatus. In the white race, the facial angle ranges between 75 and 85 ; in the negro, between 70 and 80. In idiots it is 65, or even much less ; and in the adult orang-outang it is about 30. In speaking of the bones which compose the skull, eight were indicated as belonging to the cranium, and fourteen to the face. The ethmoid bone, included in the account of the former, really contributes more to the composition of the latter ; and the face, as we usually refer to it, includes the forehead as formed by the frontal bone. THE SIDE OF THE SKULL. The Tem/poral fos'sa 2 occupies a great portion of the side of the skull, and is bounded above by the temporal ridge, 3 and below by the zygomat'ic arch. The former proceeds from the external angular process of the frontal bone upward and backward upon the parietal bone to the dividing ridge between the squamous and mastoid portions of the temporal bone. The tem'poral surface, which gives origin to the tem- poral muscle, is formed by the frontal, sphenoid, parietal, and temporal bones ; and it terminates inferiorly at a ridge proceeding from the root 1 Facial angle of Camper ; angulus faciei Camperi. 2 Fossa temporalis. 3 Linea temporalis. THE SKELETON. FIG. 64. of the zygomatic process of the temporal bone, across the great wing of the sphenoid bone to the outer extremity of the spheno- maxillary foramen. The Zygomat'ic arch, 1 be- neath which passes the tem- poral muscle to its insertion, is formed by the zygomatic process of the temporal and the malar bone, and gives support to the cheek. The Sphe'no-max'illary fos'sa 2 is the space between the bottom of the great wing and the external pterygoid process of the sphenoid bone, and the back part of the VIEW OF THE RIGHT SIDE OF A PORTION OF THE FACE AND CRA- maxillary bone, and NIUM. 1, frontal bone; 2, malar bone, a portion of its zygo 1S OCCUpied by the external matic process removed; 3, zygomatic process of the temporal f t m bone ; 4, glenoid tubercle, and back of it the glenoid cavity ; 5, pterygoid mUSCle. At its Up- squ anious portion of the temporal bone ; 6, anterior inferior per part anteriorly is a large an le of the P arietal bone ; 7 > temporal surface of the frontal . bone ; 8, temporal surface of the great wing of the sphenoid aperture, the Sphe nO-maX - bone; 9, inferior surface of the great wing; 10, external fbra'men, 3 Which COm- pterygoid process; 11, internal pterygoid process ; 12, superior maxillary bone; 13, ptery go-maxillary fossa; 14, spheno-pala- . , , ,. T With the Orbit. It tine foramen; 15, spheno-maxillary foramen; 16, oval fora- 1S bounded by the Sphenoid, men; 17, spinous foramen; 18, infra-orbital foramen. Figures .-,, , 5-8 occupy the fore part of the temporal fossa; the space Superior maxillary, malar, between 9> 10 , and U , 15, is the spheno-maxillary fossa. and palate bones; and cor- responds to the free communication, or rather continuation, of the tem- poral fossa and orbit in most of the inferior mammals. The Ptery'go-max'illary fos'sa 4 is the deep, wedge-shaped fissure, at the bottom of the former fossa, extending from the inner extremity of the spheno-maxillary foramen downward, between the pterygoid processes of the sphenoid bone, and the superior maxillary and palate bone. It is beneath the apex of the orbit, and has, opening from its upper part backward, the pterygoid canal ; and inward, the spheno-palatine foramen. 1 Arcus zygomaticus ; zygoma ; pons zygomaticus. 2 Fossa spheno-maxillaris ; zygomatic fossa. 3 Foramen spheno-uiaxillare; fissura orbitalis inferior, or spheno-maxillaris ; foramen lacerum inferius. 4 Fossa pterygo-maxillaris ; f. pterygo- palatina. 90 THE SKELETON. THE BASE OF THE SKULL. FIG. 65. VIEW OF THE RIGHT HALF OF THE BASE OF THE SKULL. 1, palate plate of the superior maxillary bone ; 2, palate plate of the palate bone; 3, vomer ; 4, internal ptery- goid process; 5, external ptery- goid process ; 6, pyramidal process of the palate bone ; 7, under sur- face of the great wing of the sphenoid bone; 8, its temporal surface; 9, zygomatic arch; 10, zygomatic process of the malar bone; 11, zygomatic process of the temporal bone; 12, squamous portion of the temporal bone; 13, glenoid tubercle ; 14, glenoid cav- ity; 15, vaginal process, its outer border constituting the auditory process; 16, styloid process; 17. external auditory meatus; 18, mastoid process; 19, digastric groove ; 20, basilar process of the occipital bone co-ossified with the body of the sphenoid bone; 21, condyle; 22, occipital protuber- ance ; 23, superior, and 24, inferior semicircular ridges ; 25, occipital foramen ; 26, incisive foramen ; 27, posterior palatine foramen; 28, spheno-maxillary foramen ; 29, posterior naris ; 30, oval fora- men ; 31, spinous foramen ; 32, lacerated foramen; 33, Eustachian tube ; 34, carotid canal ; 35, jugular foramen ; 36, stylo-mastoid fora- men ; 37, 38, foramina for veins. and transverse pal'ate su/tures. 3 At the fore part of the middle suture is the anterior pal- atine fora'men, 4 which communicates above with the two naso-palatine canals entering the nasal fossa3. At the posterior part of the hard palate, on each side, is the posterior pal'atine fora'men, 5 from which coarse grooves are directed forward for the accommodation of the pal- atine nerves and blood-vessels. The Gut'teral region, 6 so named because it forms the upper boundary The Base of the Skull, included in the occipital and inferior maxillary outline, is ovate in form, and in- cludes the palatine, gut- teral, and occipital re- gions. The Pal'atine or oral region 1 is inclosed by the upper and lower jaws, and is bounded above by the vaulted hard palate. Its depth ordinarily is about two and a half inches, but before the protrusion of the teeth, and sub- sequent to their loss, it is reduced to an inch or less in depth. The hard pal'ate 2 presents a roughened surface, divided by the middle 1 Regio palatina : cavum oris. 2 Palatum durum ; p. osseum. 3 Sutura palatina cruciata. 4 F. palatinum anterior ; f. incisivum. f. alveolare anterius ; f. coecum. 5 F. palatinum posterior, or descen- dens; f. palato-maxillare ; f. alveolare postering. 6 Regio gutteralis. THE SKELETON. 91 of the pharynx or throat, has the posterior nares opening into it in front, and is limited behind by the occipital foramen and condyles. On each side are the pterygoid processes, and above, it is bounded by the basilar process of the occipital bone and the body of the sphenoid bone. The Occipital region includes that part of the base of the skull pos- terior to the occipital foramen and condyles. THE ORBITS. The OrVits 1 are quadrately pyramidal cavities situated beneath the anterior part of the cranium, with their axes directed forward and outward. The apex of each orbit corresponds with the optic foramen, and the base forms the orVital entrance, 2 This is situated beneath the forehead, and is transversely quadrate-oval, with a slight obliquity from the median line downward, and a direction forward and a little outward. The roof of the orbit is vaulted, and is formed by the orbital plate of the frontal bone and the lesser wing of the sphenoid bone. The floor is slightly depressed below the infra-orbital margin, and is formed by the orbital plate of the superior maxillary bone and the orbital process of the palate bone. The inner wall is nearly vertical and parallel with that of the other orbit, and is formed by the nasal process of the superior max- illary bone, the lachrymal bone, the orbital plate of the ethmoid bone, and the body of the sphenoid bone. The outer wall is also nearly vertical, but is directed obliquely outward ; and it is composed of the orbital plate of the great wing of the sphenoid bone and that of the malar bone. At the bottom or apex of the orbit are the optic and sphenoidal fora- mina, already described, and between the outer wall and floor is the spheno-maxillary foramen, also previously described. At the anterior part of the inner wall of the orbit is the lach/rymo- na'sal duct'. 3 Commencing as a fossa 4 or groove between the nasal pro- cess of the superior maxillary and lachrymal bones, by the addition of a process of the turbinated bone, its lower half forms a complete tube. It descends with a slight inclination backward, and terminates at the anterior part of the inferior meatus of the nasal fossa. At the upper border of the inner wall of the orbit, in the suture 1 Orbitao; trochiae ; conchi; cavitates, 3 Ductus or canalis lachrymo-nasalis, or fovese, or pelviculae oculorum ; orb- or naso-lachrymalis ; ductus ad nasum : itarfossoe; orbitar cavities. lachrymal duct; nasal duct; ductus na- 2 Apertura orbitalis. sails orbitse. 4 Fossa lachrymalis. 92 THE SKELETON. between the ethmoid and frontal bones, are the anterior and posterior ethmoid'al fora'mina, 1 for the transmission of a nerve and an artery. FIG. 66. THE NASAL CAVITIES. The Na'sal cavities or fos'sae 2 are two complicated spaces separated by a thin vertical partition, the os'seous na'sal sep'tum. 3 They open on the front of the face by the anterior na'sal or'ifice, and communicate posteriorly with the gutteral region by the posterior na'sal or'ifices or na'res. Communicating with them are the frontal, ethmoidal, sphenoidal, and maxillary sinuses, which are accessory chambers. The height and depth of each nasal cavity are about two inches ; the greatest width, which is below the turbinated bone, is about half an inch. The anterior na'sal or'ifice* is pyriform, and is bounded by the supe- rior maxillary and na- sal bones. Its border is thin and sharp ; in the negro, however, it is rounded off at the bot- tom. From the middle of its base, the na'sal spine 5 projects, for the attachment of the column of the nose. The posterior na'sal or'ifices 6 are quadrate apertures separated by the vomer, and, in addi- tion to the latter, are bounded by the body and internal pterygoid proc- esses VERTICAL SECTION OF THE FACE, exhibiting the osseous nasal sep- turn. 1, frontal bone; 2, frontal sinus; 3, nasal spine of the frontal bone bone; 4, nasal bone; 5, nasal spine of the superior maxillary bone; 6, nasal process of the same bone ; 7, border of the palate plate of the same; 8, incisive foramen; 9, left posterior naris; 10, palate plate of the palate bone ; 11, nasal plate of the ethmoid bone ; 12, ethmoidal crest; 13, vomer; 14, left turbinated bone; 15, sphenoidal sinus; 16, internal pterygoid process ; 17, external pterygoid process. of the sphenoid r and the palate The OS SGOUS na Sal coYj'fmn. IS formed bv the nasal plate Of the 6th- 1 F. ethmoidale anterius et posterius ; f. orbitale ant. et post. 2 Cavi narium ; nares internae. 3 Septum narium osseum. * Apertura narium anterior. 5 Anterior nasal spine. 6 Posterior nares ; aperturae narium posteriores. THE SKELETON. 93 FIG. 67. moid bone and the vomer, which have between them anteriorly a deep angular notch for the reception of the cartilaginous septum. Frequently the nasal septum is bent to one side, thus increasing the width of one cavity at the expense of the other. The roof of the nasal cavities is antero-posteriorly concave, and is narrower and longer than any other portion. It is formed by the nasal bones, the nasal spine of the frontal bone, the cribriform plate of the ethmoid bone, and the body of the sphenoid bone. The floor of the nasal cavities is a little depressed below the level of the base of the anterior nasal orifice ; and is formed by the palate plates of the maxillary and palate bones. The outer wall is the most complicated portion of the nasal cavities. From it project inward and downward, like three scrolls, the turbinated processes of the ethmoid bone and the turbinated bone ; and below these are situated the na'sal mea'tuses. 1 The superior mea'tus is the shortest, is situated VIEW OF THE OUTER WALL OF THE RIGHT NASAL FOSSA. 1, frontal ,, bone ; 2, its orbital plate ; 3, its nasal spine ; 4, nasal bone ; 5, eth- ' DaCK part OI moid bone; 6j itg upper turb i nate(i pr0 cess; 7, its lower turbinated each Cavity, and is di- process ; 8, turbinated bone; 9, process of the lachrymal bone, within , -, -,-, i -, the position of which is the lachrymo-nasal duct ; 10, nasal spine of rected obliquely down- th / superior maxillary bone . naso _ palati . ne canal; 12 , palate Ward and backward tO plate of the superior maxillary bone; 13, nasal process of the latter; the UDDer Dart Of the 14> external P tei Tgid process; 15, internal pterygoid process; 16, nasal plate of the palate bone ; 17, its palate plate ; 18, posterior pal- Corresponding posterior atine foramen ; 19, superior meatus of the nose ; 20, middle meatus ; nasal Orifice Into it 21, inferior meatus ; 22, frontal sinus; 23, sphenoidal sinus; 24, its communication with the upper back part of the nose ; 25, spheno- the posterior and middle palatine foramen ; 26, orifice of the maxillary sinus. ethmoidal sinuses open ; and above its posterior extremity, the sphenoidal sinus communicates with the nose. The middle meatus is situated between the ethmoid and turbinated bones along the middle of the nasal cavity. Into it open the anterior 1 Meatus narium. 94 THE SKELETON. ethmoidal and frontal sinuses and the maxillary sinus. The orifice of the latter is much reduced in size compared with its condition in the isolated maxillary bone ; the ethmoid, palate, turbinated, and lachrymal bones all contributing to its diminution. The inferior mea'tus, situated below the turbinated bone, is trans- verse in its direction from before backward ; and it has communicating with its anterior part, the lachrymo-nasal duct. DEVELOPMENT OF THE FACE. In all mammals below man, that portion of the superior maxillary bone which supports the incisor teeth is separated from the principal portion, and is known as the intermaxillary bone. It may be observed in the skull of any domestic animal. As a distinct piece, it is obscurely visible in the human embryo as late as the third month, and may be detached from the superior maxillary bone. It soon becomes co-ossified with the latter, and its line of separation is distinguishable subsequently only for a short distance transversely outward from the incisive fora- men. Occasionally, as in some cases of hare-lip, the intermaxillary bone remains permanently distinct. To the main portion of the maxil- lary bone, the author has not been able to detect more than a single point of ossification, from which the bony rays shoot upward, backward, and outward. The palate bone is developed from a single ossific point, commencing at the angle of conjunction of the vertical and horizontal portions. The lachrymal, nasal, turbinated, and malar bones, and the vomer, are each developed from one centre of ossification. In the development of the inferior, maxillary bone, each half appears to originate in a single ossific point, which commences before any other in the skeleton, except that of the clavicle. At birth the lower jaw con- sists of two halves, united at the symphysis by fibro-cartilage, but which, during the first year, subsequently co-ossify. CHANGES OF THE SKULL AT DIFFERENT PERIODS OF LIFE. In the embryo and early foetus the skull has a spheroidal figure, with a comparatively small conical prominence corresponding to the face. At birth, and for some time subsequently, the cranium is still more spher- oidal than afterwards, and at this early period is much larger in com- parison with the face than at maturity. The facial angle also is greater than it is at a later period. The skull is composed of a greater number of pieces at birth than THE SKELETON. 95 afterwards, as already indicated in the account of the individual bones. The texture of these, due to their greater proportion of bone carti- lage, is more flexible, and they are rather disposed to bend than to break. The bones likewise are more readily movable upon one another, so that from this and the preceding circumstance, the head in infancy is readily modified in shape artificially, as instanced in the change of form produced in the cranium, customary among the Flat-head Indians, and other savage tribes. In the infant skull, the bones of the vault of the cranium are more conical than concavo-convex, as they afterwards become. The greatest transverse diameter of the skull is at the parietal protuberances ; but later, is at the temporal fossae. The latter are proportionately small, in accordance with the moderate development of the temporal muscles, which are not yet required for mastication. The face is low, and situated entirely beneath the cranium. The nasal cavities are small, and the various sinuses communicating with them only begin to be developed. The mouth or palatine region in vertical depth is not more than half an inch ; and the rami of the lower jaw project comparatively little above its body, and are more oblique than afterwards. As the child grows, the bones of the skull acquire greater hardness, become thicker, and gradually develop their spongy substance and their sinuses. With the development of the teeth and alveolar processes, and the protrusion of the former, the face becomes more prominent and deeper, the facial angle declines, and the spaces occupied by the masticating muscles enlarge. The rami of the lower jaw lengthen downward, and become less oblique ; and the mouth increases to two and a half inches of vertical depth. With the advance of the face, there is also a recession of the cranium; and from the development of the frontal sinuses, the superciliary ridges become the most prominent portion of the forehead, instead of the frontal protuberances as in infancy. From puberty to adult age, but little change occurs in the skull, except a comparatively slight and very gradual increase in size and strength. At maturity the sutures gradually disappear ; and in old age a sort of retrograde metamorphosis occurs. The bones of the skull become thinner and more brittle, and the spongy substance decreases, though the sinuses enlarge. With a diminution in quantity of the brain, the cranium undergoes an actual reduction in size. The teeth drop out, and the alve- olar borders of the jaws disappear, reducing the depth of the mouth almost to the condition of that in infancy. In consequence of these changes, the face loses much of its vertical extent, and the facial angle is increased. As the body of the lower jaw forms a much larger 96 THE SKELETON. FIG. 68. arch than the upper jaw, it mounts upon and incloses the latter, thus bringing the prominent chin just beneath the nose, as so strikingly observed in the aged. THE HYOID BONE. The Hy'oid bone 1 is situated in the front of the neck, at the root of the tongue, and is readily felt just above the larynx. It consists of a median symmetrical body, with a pair of horns on each side. The body 2 is the middle piece in front, and is quadrate in outline. Anteriorly it is convex and impressed on each side by muscles, and posteriorly is concave. The greater horns 3 project backward from the ends of the body; and are comparatively long, thin processes ending in a tubercle. The lesser horns, 4 usually in a cartilaginous condi- tion until late in life, are conical, and project upward and backward from the junction of the body with the greater horns. The lesser horns connect the hyoid bone with the styloid process of the temporal bone, by means of a long, narrow, fibrous cord, the sty'lo- hy'oid liga'ment, 5 Generally they are only two or three lines long, and often vary in length and degree of ossification on the two sides. Some- times ossification extends from them up the stylo-hyoid ligament, and rarely, its entire length. HYOID BOXE. 1, body; 2, greater horn ; 3, lesser horn. THE TRUNK. That division of the skeleton called the trunk 6 is composed of the vertebral column, the ribs, the sternum, and the hip bones. Its upper extremity forms the bony axis of the neck ; below this is the thorax or chest ; then follows the axis of the loins ; and the lower part of the trunk forms the pelvis. 1 Os hyoides ; os linguae, or lingualc ; os ypsiloides ; os gutteris, or gutterale ; os bicorne ; os lambdoides. 2 Basis ; ossiculum medium hyoidis. 3 Cornua majora; branches; rami. * Cornua minora ; corpuscula, or grana triticea ; cornicula ; ossa pisiformia lin- gualia ; styloid cornua. 5 Ligamentum stylo-hyoideum. 6 Truncus. THE SKELETON. 97 THE VERTEBRAL COLUMN. The Vert'ebral column 1 is the axis of sup- port of the body, and is situated along the middle line of the trunk posteriorly. It is composed of twenty-nine symmetrical pieces, named vert/ebrae, 2 which are divided into twenty-four true and five false vertebrae. In front, the vertebral column is composed of a series of half cylindroid segments con- joined by fibro-cartilage ; posteriorly, of a series of arches supporting processes for mutual ar- ticulation, and others for muscular attachment. From the elongated spine-like character of its posterior median processes, the entire column is ordinarily named the spine. 3 FIG. 69. THE TRUE VERTEBRAE. The True vert'ebrae, 4 twenty-four in number, extend from the skull to the pelvis, and gradu- ally increase from the first to the last, which rests on the sacrum. From their relative po- sition in the trunk they are divided into cer- vical or neck vertebrae, dorsal or thoracic ver- tebrae, and lumbar vertebrae. The true vertebrae are composed of a body and an arch supporting seven processes. The body 5 is at the fore part, and usually possesses the form of a transverse segment of a half cylinder, concave posteriorly, and con- stricted at the front and sides. Its broad sur- face above and below is generally flat, with a slightly elevated border; and is conjoined with the contiguous vertebral body by means of a 8 to iMorsai vertebra; 20 to 24, lumbar vertebrae : 25, sacrum; 26, plate of nbro-cartilage. coccyx. THE VERTEBRAL COLUMN, lateral view; exhibiting the curvatures, 1 to 24, true vertebrae; 25, 26, false vertebrae; 1 to 1. cervical vertebrae ; 1 Columna vertebralis; spinal column; columna spinalis ; columna dorsi ; spine; spina dorsi; back bone; rachis ; carina; dorsum; tergum; notos; acnestis ; acantha; compages vertebrarum ; sacra fistula; hiera syrinx. 2 Spondyli ; spondles; whetle bones. 3 Spina. 4 Vertebrae veroe. 5 Corpus vertebrae; centrum. 98 THE SKELETON. FIG. 70. SIDE VIEW OF A DOBSAL VERTEBRA. 1, body ; 2, articular facets for ribs ; 3, arch ; 4, 5, interverte- bral notcb.es; 6, spinous process; 7, transverse process; 8, 9, articular processes. The arch 1 is attached to the sides of the body posteriorly by narrow ped/icles, 2 and the passage through it is the spi'nal fora'men, 3 forming part of the spinal canal for contain- ing the spinal cord. In form the arch is angular, and its sides ex- pand below ; so that in the verte- bral column the arches together present a somewhat imbricated ap- pearance. From the summit of the arch posteriorly projects the spi'nous proc'ess, 4 and from each side, the trans'verse proc'ess, 5 all of which serve as points of attachment for muscles. Above and below, the arch supports a pair of artic'ular proc'esses, 6 which present smooth discoidal facets for articulation with those of the contiguous vertebra?. Between the position of the articular and spinous processes, the arch is formed of a pair of shelving plates, 7 of which the upper border behind and the lower border in front are roughened for the attachment of the elastic yellow ligaments. Above and below the pedicles of the arch, and between the articular processes and body, are the intervert/ebral notches, of which the infe- rior pair is generally the deeper. By the approximation of the notches of the contiguous vertebra they form the intervert'ebral fora'mina, 8 for the transmission of the spinal nerves and blood-vessels. In structure, the body of the vertebra? is composed of a mass of spongy substance covered with a thin layer of compact substance, which is perforated with numerous comparatively large nutritious or vascular foramina. At the middle of the body posteriorly there are two of these foramina particularly conspicuous, which communicate with channels for conducting veins from the spongy substance to the vertebral sinuses. The vertebral arch, together with its processes, requiring greater strength 1 Arcus vertebrae; vertebral arch; neural nrch. 2 Neurapophyses. 3 Foramen spinale, or vertebrale ; ver- tebral foramen. 4 Processus spinosus; neural spine. 5 P. trans.versus ; diapophysis. 6 P. articulares; oblique processes ; p. ascendentes et descendentes; zyga- pophyses. 7 Veriebral plates; laminae ; neurapo- physes. 8 F. intervertebralia ; f. vertebralia; f. conjugata. THE SKELETON. 99 than the body, have a predominance of compact substance composing them. The characters, thus given of the true vertebrae, are modified in the three regions to which we have referred ; so that the cervical, dorsal, and lumbar vertebrae will now require a special description. In each region, however, the characters are not constant for all the vertebrae, as we find those of contiguous regions assuming more or less the appearance of one another ; and in several instances they are much modified, so as to be adapted to some special function, as in the case of the upper pair of the neck. THE CERVICAL VERTEBRA. The Cer'vical vert'ebrae 1 are seven in number, and form the bony axis of the neck, extending from the skull to the thorax. The most striking peculiarity, by FIG. 71. which they may be distinguished from those of the other regions of the trunk, is the large foramen in the transverse processes. The body is widest transversely, and this disposition increases from the first to the last of the series. Its upper surface is rendered transversely concave from the elevation of the lateral borders; and its lower surface is in a less degree concave in the opposite direction UPPER VIEW OF A CERVICAL VERTE- from the prolongation of the anterior and pos- BRA from tho naiddle of the series - . 1, body; 2, 3, arch; 4, spinous proc- terior borders. From this arrangement the ess; 5, transverse process; 6, its fo- COntlgUOUS bodies interlock, thus affording a ramen; 7, superior articular process; 8, inferior articular process; 9, ele- prOVlSlOn against dislocation where the Verte- vated lateral border of the body. brae are smallest. The arch is less deep, but wider than in the dorsal or lumbar vertebrae ; and the spinal foramen is trilateral, with rounded angles, and larger than in the other true vertebrae. The upper and lower intervertebral notches are nearly equal in size. The spinous process is comparatively short, and is bifid at the extremity. The transverse processes are also comparatively short, and they consist of two portions. The posterior portion, 2 springing from the pedicle of the vertebral arch, corresponds with the transverse processes of the dorsal vertebrae, while the anterior portion corresponds with the ribs. 3 The two portions being conjoined by an isthmus, a foramen 4 is formed, 1 Vertebras colli ; v. cervicis. 3 Parapophysis. 2 Diapophysis. * F. transversarium ; f. vertebrate. Carbon, 100 THE SKELETON. which, in the case of the upper six vertebrae of the neck, transmits the vertebral artery. The upper articular processes have their facets directed obliquely back- ward and upward ; the lower ones, downward and forward. The description thus given of the cervical vertebrae applies especially to those from the third to the sixth inclusive ; the remaining three pos- sess peculiarities requiring special notice. The first cervical vertebra is named the Atlas, 1 from its supporting the head. It is an irregular ring, and is broader than any other of the vertebrae of the neck. The large space included by the ring is divided by the transverse ligament into two parts, of which that anterior is the smallest, and is occupied by the pivot-like odontoid process of the second vertebra ; the posterior portion is the true spinal foramen. Anteriorly, the atlas presents a short transverse bridge, with a tubercle in front, and a smooth articular facet behind, which moves on the odontoid process. The arch of the atlas is rounded, and its rudimental spinous process is in the form of a small tuberosity. The transverse process is much prolonged beyond that of the other UPPER VIEW OF THE ATLAS, i, anterior tubercle; cervical vertebrae, and ends in a 2, articular facet for the odontoid process; 3, arch, , ., , with its rudimental spinous process; 4, groove for founded tuberOSlty. the vertebral artery ; 5, transverse process ; 6, its The Upper articular prOCCSSeS form elliptical concavities inclining inwardly, and having their long diameter directed forward and inward. They articulate with the occip- ital condyles, and are the centre of the backward and forward motion of the head. The lower articular processes have oval, slightly depressed facets, directed downward and inward. The portions of the atlas forming the articular processes are the thickest and strongest of ths bone ; and they are adapted to sustain the pressure of the skull, which is subsequently transmitted, through the obliquity of the inferior articular processes, to the body of the second cervical vertebra, and thence through all the other vertebral bodies. Between the position of the upper and lower articular processes intern- ally, is a tuberosity, for the attachment of the transverse ligament, which retains the odontoid process in its place. 1 Atlantion ; astragalus. THE SKELETON. 101 The intervertebral notches of the atlas are behind the articular processes, those below being the smaller. The upper ones are continuous with a groove from the foramen of the transverse process, and transmit the ver- tebral arteries in their course to the occipital foramen. Sometimes these upper notches are converted by a bridge of bone into foramina. The second cervical vertebra is called the Ax'is, 1 from its supporting the pivot upon which the atlas and the skull together rotate. FlG - 73< The body of the axis presents a median prominence in. front, and its upper part is pro- longed into the pivot-like odontoid proc'ess, 2 which projects within the circle of the atlas. The process is conical, has a smooth facet in front to articulate with the bridge of the atlas, and another behind, against which the trans- SIDE VIEW OF THE AXIS, i, body; verse ligament moves. The summit and sides ^n^?T^,t are also impressed by the attachment Of the transverse process, with its foramen; ligaments Which moderate the rotation Of the 7, 8, superior and inferior articular processes. head. The arch of the axis is more robust than in any other of the cervical vertebrae. The spinous process is comparatively very strong ; and it has depressed sides, a deep groove below, and a cleft extremity. The transverse process is the shortest in the cervical series, and its foramen ascends at first beneath the upper articular processes, and then turns abruptly outward and backward. The upper articular processes are oval in form and slightly convex, and rest obliquely upon the sides of the body and the pedicles. They are the circle of the rotary movements of the head, while the odontoid process is the centre. The upper intervertebral notches are obsolete ; while those below, and other parts of the bone in this position, correspond with the condition of the other vertebra? of the neck. The last cervical vertebra 3 partakes strongly of the characters of the dorsal series, and is particularly remarkable for the length of its spinous process, which is tuberous at the end, instead of being cleft as in the others. 1 Vertebra dentata; epistropheus ; 2 P. odontoideus, or odontoides; p. axon ; maschalista. dentatus ; p. dentiformis ; p. pyrenoides. 3 V. prominens. 102 THE SKELETON. THE DORSAL VERTEBRAE. The Dor'sal vert'ebrse, 1 twelve in number, form the bony axis of the thorax, and extend from the neck to the loins. The most characteristic marks by which they may be distinguished from other vertebra are the articular facets for the ribs. The bodies decrease in breadth from the first to the third, then are nearly uniform in this respect to FlG - 74 - the fifth, and afterwards gradually increase to the last. They are more demi-cylindroid in form than either those of the neck or loins. Their upper and lower surfaces are flat. The arches are smaller and stronger than in the cervical verte- bra. The spinal foramen is nearly circular, and is smaller than in the r SIDE VIEW OP A DORSAL VERTEBRA. 1, body ; 2, facets for ribs; 3, arch; 4, 5, interverte- The lower interVCrtebral notches are much lar e er than the ones. The spinous processes are long and narrow, are trilateral, and have a tuberous extremity. They are directed backward and downward, suc- cessively increasing in the latter inclination to the lower ones of the series. The transverse processes 2 are long and strong, and terminate in a thick tuberosity. They are directed outward, with a successively increasing inclination backward. The articular processes are nearly ver- tical ; those above being directed backward, those below forward. The articular facets for the ribs are situated one at the upper and lower margin of the body, on each side posteriorly, and another in front of the extremity of the transverse processes. The facets, at the sides of the bodies of contiguous vertebrae, together form pits, 3 for the articu- lation of the head of the ribs. The facet of the transverse process articu- lates with the tubercle of the ribs. The bodies of the first and last two dorsal vertebra present each a complete articular facet for the heads of the corresponding ribs. V. dorsales; v. thoracis ; thoracic vertebrae. 2 Diapopliyses. 3 Foveae articulares. THE SKELETON. 103 THE LUMBAR VERTEBRAE. The Lum'bar vert'ebrae, 1 five in number, form the bony axis of the loins, and extend from the thorax to the pelvis. They are the largest of the true vertebrae, and are readily distinguished from the others by the absence of a foramen in the transverse processes and articular facets for ribs. The bodies are oval in transverse section, and successively increase in size to the last. As in the dorsal series, their upper and lower surface is flat. The arches are strong, and increase in width from first to last. The spinal foramen is large and trilateral. The intervertebral notches are large, and nearly equal in size above and below. The spinous process forms a SlDE VIEW OF A 1UMBAR VRTEBRA . i, body; 2. Strong Vertical plate projecting side of the arch; 3,4, intervertebral notches; 5, ,. . ,,. , spinous process; 6, transverse process; 7, 8, artic- backward and ending in a thick- ular proce8se8 . ened extremity. The transverse processes 2 are narrow, directed outwardly, and suc- cessively increase in length to the middle of the series, and then dimmish to the last. They represent ribs ; while the part corresponding with the transverse processes of the dorsal vertebra is a tubercle projecting from the outer side of the upper articular process. The articular processes are vertical ; the upper ones being directed toward, while the lower ones are directed from each other, by which arrangement those of the contiguous vertebrae interlock, and thus aid in maintaining the articular integrity of the column, where it has no lateral support as in the thorax. THE FALSE VERTEBRAE. The False vert'ebrae 3 are so called because they consist of nine seg- ments corresponding with the true vertebrae, which in the mature condi- tion are co-ossified into comparatively few pieces. The upper five pieces, co-ossified, constitute the sacrum ; the lower four pieces form the coccyx. 1 V. lumbales; vertebra} of the loins. 2 Purapopliyses. 3 V. spurite. 104 THE SKELETON, SACRUM. The Sa'crum 1 is a triangular bone, inserted obliquely backward and downward between the hip bones, at the posterior part of the pelvis. Its base is upward, joining the last lumbar vertebra ; its apex down- ward, joining the coccyx. FRONT VIEW OF THE SACRUM. 1, transverse ridges, indicating the original separation of the bone into five segments; 2, sacral foramina; 3, promontory; 4, articular surface for the hip bone; 5, sacral bor- der of the sacro-sciatic notch ; 6, base of the sa- crum, with its articular surface for the last lumbar vertebra ; 7, wing of the sacrum ; 8, articular proc- ess ; 9, apex of the sacrum, with its articular sur- face for the coccyx ; 10, pedicle of the last verte- bral arch of the sacrum ; 11, notch for the last sa- cral nerve. BACK VIEW OF THE SACRUM. 1, rudimental spi- nous processes ; 2, 2, sacral canal, terminating below in a notch between the pedicles, 3, 4, of the last vertebral arch; 3, 3, rudimental articular proc- esses; 5, sacral foramina; 6, 6, rudimental trans- verse processes; 7, articular surface for the hip bone ; 8, sacral border of the sacro-sciatic notches ; 9, articular surface for the last lumbar vertebra ; 10, articular processes for the latter bone ; 11, apex of the sacrum ; 12, rough surface on the wing of the sacrum, for the sacro-iliac ligaments. It is curved forward, and has a broad, smooth, concave surface in front, and an irregular, narrower, convex surface behind. It varies in degree of curvature and relation of length with breadth in different indi- viduals, as well as sexes. As a general rule, it is more curved and longer in proportion with its breadth in the male. The bone corresponds with five vertebrae, whose elements are more or less obscured by co-ossification and feeble development. The front surface of the sacrum exhibits four transverse lines, indi- cating the original separation of the bodies of the sacral vertebrae. The first division of the bone presents an oval articular surface for the 1 Os sacrum; os latum; os clunium ; os basilare; os alagas; vertebra magna ; lus; luz ; clunis; subvertebra; hieron osteon; albagiazi ; vetula. THE SKELETON. 105 body of the last lumbar vertebra, and the last division a similar but smaller surface for the first piece of the coccyx. The posterior part of the sacrum is composed of the co-ossified arches of the vertebral segments. The fifth arch is generally incomplete or open at its back part; and sometimes this condition extends to the arch above, or even through the others. The continuation of the spinal canal is called the sa'cral canal', 1 and is trilateral. It diminishes in its descent, and terminates in the notch 2 produced by the incompleteness of the fifth sacral arch. In front, and behind the sacrum, on each side, are the four sa'cral fora'mina, 3 which communicate with the sacral canal, and correspond with the intervertebral foramina. They successively diminish in size from above downward, and transmit the sacral nerves and blood-vessels. The anterior ones are the larger, and lead outwardly into grooves. The spinous processes successively diminish in size. The upper three are in the .form of tubercles, and more or less confluent into a ridge. The fourth one is usually cleft into two tubercles, which likewise conjoin with those above. The upper articular processes of the first sacral division form vertic- ally concave facets directed backward and inward. They are separated by a wide notch, which is occupied by the last pair of the yellow liga- ments. The other articular processes are rudimental, and are obscurely distinguishable bounding the inner side of the posterior sacral foramina. The wings 4 or lateral portions of the sacrum correspond with the ribs and transverse processes of the dorsal vertebrae, which are here fused together, so as to afford a broad surface of articulation for the hip bones. Below the surface for the latter, the obtuse margin of the bone gives attachment to the sacro-ischiatic ligaments. The rough sur- face behind the articulation gives attachment to the sacro-iliac ligaments. THE COCCYX. The Coc'cyx 3 is situated at the lower end of the sacrum, from which it curves downward and forward. It corresponds with four of the true vertebras, and though described as consisting of as many pieces, it pre- sents a very variable condition of co-ossification of these. The four bones successively decrease in size, and as vertebras become 1 Canalis sacralis. 5 Os coccygis; caudal vertebrae ; crup- 2 Hiatus sacralis. per bone ; rump bone ; os alagas ; ossis 3 F. sacralia. sacri acumen ; cauda ; cuculus ; uropy- 4 Aloe sacraliae. gion. 10<5 THE SKELETON. more rudiinental. FIG. 78. POSTERIOR VIEW OF THE COCCYX. 1, first piece; 2, 2, pedicles of a ver- tebral arch ; 3, transverse processes; 4, 5, 6, lower three pieces of the coccyx, consisting of rudimental vertebral bodies. The first of the series has a compressed body, with oval articular faces for conjunction with the sacrum and the second bone of the coccyx. From each side projects a transverse process. This is not unfrequently co-ossified with the margin of the sacrum, giving rise to a fifth sacral fora- men. Behind the body on each side is another short process, 1 which corresponds with the pedicle of a vertebral arch. The remaining three bones present mere flattened bodies successively diminishing in size. The pieces of the coccyx correspond with the caudal or tail vertebra? of lower animals. DEVELOPMENT OF THE VERTEBRAE. Ossification commences in the vertebra about the seventh or eighth week of embryonic life, and is not entirely completed until near the twenty-fifth year after birth. As a general rule, each true vertebra is developed from three principal ossific points, of which one belongs to the body, and one to each side of the arch with its processes. To these are added five epiphyses, of which three arise at the ends of the spinous and transverse processes, and the remaining two appear as thin plates on the articular surfaces of the body. FIG. 80. FIG. 79. DEVELOPMENT OF THE VERTEBR.E. a, vertebra of a foetus, in a cartilaginous condition, with three centres of ossification; 1, 2, latent! pieces; 3, the body ; 6, vertebra of an infant. The lateral pieces, 1, 2. are co-ossified at the spinous process, and join the body 3, at the sutures 4. The ends of the trans- verse and spinous processes yet in a cartilaginous state. DEVELOPMENT OF THE EPIPHYSES TO THE VERTE- BRA, a, dorsal vertebra, with the epiphyses 4, 5, to the transverse processes; 6, to the spinous pro- cess; and 7, to the body; b, arch with its processes; and c, body of a lumbar vertebra; 4, 5, epiphyses of the transverse processes; 6, of the spinous pro- cess; 7, 8, of the body; 9, 10, of tubercles of the upper articular processes. 1 Cornua sacralia. THE SKELETON. 107 The atlas is usually developed from three principal points only. The axis has two additional points for the odontoid process. The anterior division of the transverse process of the last cervical vertebra sometimes has a distinct ossific point, and this is occasionally developed into a rudi- mental and movable rib. The lumbar vertebrae have epiphyses at the ends of the transverse processes corresponding with ribs, as well as those upon the tubercles which represent the true transverse processes. The sacrum has three principal points of ossification for each division, as in the true vertebra?. In addition to these, epiphysial plates form on the articular surfaces of the bodies ; points originate on each side of the upper three divisions representing ribs ; and subsequently two epiphysial plates originate at each lateral border of the bone. In the coccyx each bone is developed from a single ossific centre. ARTICULATIONS OF THE VERTEBRAL COLUMN. The ligaments which connect the different pieces of the vertebral column together and with the skull are as follows : Twenty-seven intervertebral ligaments. Twenty-three pairs of yellow ligaments. The anterior vertebral ligament. The posterior vertebral ligament. Twenty-five pairs of capsular ligaments. The supra-spinous ligament. The interspinous ligaments. The nuchal ligament. The anterior and posterior occipito-atloid ligaments. The anterior and posterior atlo-axoid ligaments. The transverse ligament. Three odontoid ligaments. The Intervert'ebral liga'ments 1 or disks are plates of fibro-cartilage interposed between the bodies of the vertebrae, except the atlas and axis, constituting a most tenacious but pliant means of connection. They vary in thickness in different parts of the vertebral column ; being thickest in the lumbar region, and thinnest in the coccyx and dorsal region. They also vary in this respect in different parts of themselves ; thus, the disks of the cervical and lumbar regions are thickest in front, while those of the dorsal region are somewhat thicker behind. To this 1 Ligmenta intervertebralia; fibro-cartilagines intervertebrales ; intervertebral substance, cartilages, or fibro-cartilages. 108 THE SKELETON. arrangement, together with the more or less wedge-like condition of the vertebral bodies, the curves of the vertical column are due, excepting that of the sacrum, which belongs to the bending of the bone itself. FIG. 81. FIG. 82. UPPER VIEW OF A LUMBAR VERTEBRA, with a horizontal section of an intervert- ebral ligament. 1, concentric layers of fibrous tissue ; 2, pulpy fibro-cartilage. VERTICAL SECTION OF TWO LUMBAR VERTEBRA, with the in- tervening intervertebral ligament. The intervening articular processes, enveloped by a capsular ligament, are also repre- sented. 1, 1, concentric layers of fibrous tissue, curving out- wardly ; 2, 2, concentric layers curving inwardly ; 3, pulpy fibro-cartilage in the middle. Each intervertebral ligament is composed at the circumference of con- centric layers of fibrous tissue, and at the centre of a pulp-like fibro-car- tilage. The concentric layers consist of short bundles of fibres extended obliquely between the vertebraB and successively alternating in direction in the different laye^, so that if the first proceeds from left to right, the second take their course in the reverse direction, and so on through the series. The concentric layers are not quite vertical, but the more super- ficial ones bend outwardly, while the deeper ones bend inwardly. The interior pulp-like fibro-cartilage appears to be closely compressed in its position ; so that when an intervertebral disk is cut through, the fibro-cartilage rises above the level of the exposed surface. The intervertebral ligaments, while firmly associating the segments of the vertebral column, at the same time give it a decided though restricted flexibility. The exterior concentric fibrous layers strongly attach the vertebral bodies, while their alternately crossing arrange- ment permits a slight degree of torsion or twisting motion ; and at the same time the interior compressed fibro-cartilage gives elasticity to the structure. Under pressure of the body in its erect position, the curvature of the concentric layers of the intervertebral ligaments increases, and the fibrous bundles composing them become more depressed, so that the trunk diminishes in length. In the recumbent position, pressure being removed, THE SKELETON. 109 FIG. 83. the condition is reversed ; and in this manner may be explained the fact that a man is slightly taller on rising from bed in the morning than on retiring at night. In the conjunction of the vertebral bodies by means of the interverte- bral ligaments, we may discover some analogy to the ball-and-socket joint, which allows movement in all directions, though in this case it is of a very restricted character. The interior compressed fibro-cartilage of the disks between the resisting vertebral bodies serves the part of a ball, while the exterior concentric layers of alternately crossing fibrous bun- dles act as check ligaments. The entire arrangement is an admirable provision, to give a slight degree of movement in all directions to the vertebral column without endangering the integrity of the delicate nerv- ous cord which it incloses and protects. The Yellow lig'aments, 1 of which there are twenty-four pairs, situ- ated between the vertebral arches from the axis to the sacrum, are most distinctly seen within the spinal ca- nal. They are attached to the an- terior surface of the lower part of the arches above, and the posterior surface of the upper part of those below, between the position of the spinous and transverse processes. They are composed of yellow, elas- tic tissue, the fibres of which are extended between the vertebral arches. The Anterior vert'ebral lig'a- ment 2 is a strong band extending the entire length of the vertebral column, from the basilar process of the occipital bone to the end of the coccyx. Its upper extremity forms a rounded end, and is usually viewed as a distinct ligament. 3 It widens in its descent, is thickest and most obvious opposite the vertebral bodies, thinnest upon the sacrum, and adheres most tightly to the intervertebral disks and the contiguous margins of the vertebral bodies. It is com- posed of closely associated bundles of fibres, of which the superficial THREE VERTEBRAL ARCHES REMOVED FROM AS MANY DORSAL VERTEBR.E, viewed in front, and exhibiting 1, the yellow ligaments ; and 2, the capsular liga- ments of the articular processes. 1 L. flava; 1. subflava ; 1. intercruralia. 2 Anterior common ligament ; liga- mentum longitudinale anterius; 1. cor- poribus vertebrarum commune anterius; fascia longitudinalis anterior. Its lower end, the 1. sacro-coccygeum anterins. 3 Anterior middle occipito-atloid liga- ment. 110 THE SKELETON. extend the length of three or four vertebrae ; those deeper, the length of two or three ; and the deepest, between the contiguous vertebra. FIG. 84. PORTION OF THE OCCIPITAL BONE, WITH THE ATLAS AND AXIS, front view. 1, origin of the anterior ver- tebral ligament from the basilar process; 2, ante- rior occipito-atloid ligament on each side of the former ; 3, widening of the anterior vertebral lig- ament from the axis ; 4, anterior atlo-axoid liga- ment; 5, 6, 7, capsular ligaments of the articular THREE DORSAL VERTEBRA, with the articulations of the ribs, viewed in front. 1, portion of the an- terior vertebral ligament ; 2, radiating ligament ; 3, anterior costo-transverse ligament; 4, articulation of the head of the rib, laid open, and exhibiting the interarticular ligament separating two synovial cavities. This ligament, besides forming a strong bond of union to the verte- brae, also affords an origin to the crura of the diaphragm, and gives attachment to the pharynx and oesophagus, the aorta, thoracic duct, azygos vein, and inferior cava. The Posterior vert'ebral lig'ament 1 is a strong fibrous band, with fes- FIG. 86. FIG. 87. PORTION OF THE CRANIUM AND OF THE ATLAS AND AXIS, viewed from behind ; the posterior portions of the occipital and two last bones removed. 1, declivity of the sphenoid bone; 2, occipital bone; 3, atlas ; 4, axis ; 5. origin of the posterior verte- bral ligament from the basilar process ; 6, 7, capsu- lar ligaments of the articular processes. BODIES OF THREE DORSAL VERTEBRA, connected by the intervertebral ligaments, viewed from behind; the vertebral arches having been removed. 1, intervertebral ligaments ; 2, pedicles of the verte- bral arches; 3, portion of the posterior vertebral lig- ament, exhibiting its lateral festooned borders, 4. THE SKELETON. Ill tooned margins, situated within the spinal canal, and extending from the inner surface of the basilar process of the occipital bone to the end of the coccyx. In its course it widens opposite the intervertebral disks, to which and the contiguous margins of the vertebral bodies it tightly adheres ; and it narrows toward the middle of the latter, from which it is separated by the transverse veins of the spinal sinuses. The articular processes of the vertebrae are invested with cartilage ; and each joint possesses a synovial membrane and a thin capsular liga- ment. 2 The extent of motion in the joints formed by the vertebral artic- ular processes generally is very feeble, consisting only of a slight gliding in the bending of the vertebral column. The Su/pra-spi'nous lig'ament 3 is a thin fibrous band connecting the summits of the spinous processes from the last cervical vertebra to the end of the coccyx. It is strongest in the lumbar region, and is continu- ous at its upper extremity with the nuchal ligament. Its lower extremity, by expanding, closes, in this position, the spinal canal. The Interspi/nous lig'aments 4 are thin fibrous membranes connecting the contiguous spinous processes of the vertebra, and extending from the former ligament. The Nu/clial lig'ament 5 is a partition of loose fibrous tissue, separat- ing the muscles of the two sides of the neck, and extending from the cervical spinous processes along the median line of the occipital bone to the occipital protuberance. In man this ligament is a mere rudiment of the powerful elastic nuchal ligament which sustains the pendant head in quadrupeds. ARTICULATIONS OF THE OCCIPITAL BONE, THE ATLAS, AND THE AXIS. The Anterior and posterior occip'ito-at'loid lig'aments 6 are thin, broad fibrous membranes extended between the contiguous borders of the occipital foramen and atlas, before and behind the position of the con- dyles and articular processes. 1 Posterior common ligament ; 1. longi- 4 Lig. interspiualia ; membrana inter- tudinale posterius; 1 corporibus verte- spinalis brarum posterius; fascia longitudinalis 5 Lig. nuchre; fascia nuchalis ; paxy- postica. The upper extremity, usually waxy ; paxwax ; packwax ; faxwax ; tax- described as distinct, with the names wax ; lig. cervical ; descending ligament apparatus ligamentosus, membrana liga- of Diemerbroeck. inentosa, and occipito-axoidean ligament. 6 Membrana annuli anterioris et pos- 2 Ligamenta processuum obliquorum. terioris atlantis; m. obturatoria ante- 3 Ligamentum apicum ; its lower end, rior et posterior, the lig. sacro-coccygeum posticum. 112 THE SKELETON. The Anterior and posterior at'lo-ax'oid lig'aments are likewise thin fibrous membranes, the former connecting the anterior bridge of the atlas with the front of the body of the axis, and the latter connecting the contiguous borders of the arches of the atlas and axis. FIG. FIG. 80. PORTION OF THE OCCIPITAL BONE, WITH THE ATLAS AND AXIS, front view. 1, origin of the anterior vertebral ligament ; 2, anterior occipito-atloid liga- ment on each side of the former ; 3, widening por- tion of the anterior vertebral ligament ; 4, anterior atlo-axoid ligament ; 5, 6, 7, capsular ligaments of the articular processes. PORTION OF THE OCCIPITAL BONE AND THE UPPER THREE CERVICAL VERTEBRAE. 1, atlas ; 2, axis ; 3, posterior occipito-atloid ligament; 4, capsular lig- aments of the occipital condyles and articular processes of the atlas; 5, posterior atlo-axoid liga- ment ; 6, capsular ligaments of the articular proc- esses between the atlas and axis ; 7, first pair of yellow ligaments; 8, capsular ligaments of the ar- ticular processes between the second and third cer- vical vertebrae. The membranes constituting the above four ligaments are compara- tively loose and flexible, so as not to interfere with the peculiar move- ments of the skull and first pair of cervical vertebra?. The capsular ligaments of the articular processes of the occiput, atlas, and axis are likewise comparatively loose, so as to permit rotation, flexion, and extension of the head. The Trans 'verse lig'ament 1 is a strong band extended between the tubercles on the inner side of the atlas, and serves the purpose of re- taining the odontoid process of the axis in its proper position. To render its functions more effective, it sends from its middle a process upward, to be attached to the ante- rior border of the occipital fora- men, ad another one downward, to be attached at the root of the odontoid process, so that altogether it has a crucial form. 2 FIG. 90. PORTION OF THE SKULL, THE ATLAS, AND AXIS, viewed from behind ; the posterior portions of the occipital and two latter bones removed. 1, up- per extremity of the posterior vertebral ligament; 2, transverse ligament, with its two appendices, 3 and 4; 5, odontoid ligaments; 6,7, capsular liga- ments. 1 L. transversum atlantis; 1. transversale. 2 L. cruciatum. THE SKELETON. H3 The Odon'toid lig'aments 1 are three bands which ascend from the sides and summit of the odontoid process of the axis, to be attached to the anterior border of the occipital foramen. The lateral bands are much stronger than the middle one. These ligaments serve to limit the rotary movement of the head. The contiguous surfaces of the odontoid process and atlas are invested with cartilage, and form a joint lined with a synovial membrane and en- circled with a capsular ligament. 2 A similar joint is formed between the odontoid process and the transverse ligament. The movements of flexion and extension of the head, as before indi- cated, occur between the occipital bone and atlas, for which the pecu- liar construction of the condyles of the former and articular processes of the latter are well adapted ; while they are limited in extent by the capsular, occipito-atloid, and nuchal ligaments. The rotary movement of the head occurs between the atlas and axis ; the centre of motion being the odontoid process, and the circle of rotation the contiguous articular processes. It is limited by the capsular, atlo-axoid, and odon- toid ligaments. The general flexibility of the cervical portion of the vertebral column permits a slight increase in the movements indicated. THE VERTEBRAL COLUMN VIEWED ENTIRE. The Vertebral column averages about two and a quarter feet in length, and varies but little in this respect in comparison with the stature of persons, the difference depending more on the proportionate length of the lower extremities. The first vertebra forms a capital to the column sustaining the head. The other true vertebrae successively increase in bulk, forming a tapering column resting with its base upon the sacrum, which, like the key-stone of an arch, is inserted between the hip bones. The breadth of the vertebrae increases from the second to the seventh, then decreases to the fourth of the dorsal region, and afterwards grad- ually increases again to the sacrum, which rapidly diminishes to the end of the coccyx. The height of the cervical vertebra? is nearly uniform ; the others gradually increase in this respect to the last. The intervertebral ligaments gradually increase in thickness from the third dorsal vertebra to the sacrum. Above the former point they increase to the middle of the neck, and then again decrease. 1 Ligamenta alaria and 1. rectum medium ; 1. dentis suspensorium ; moderator and middle straight ligaments. 2 Vaginal ligament. 8 114 THE SKELETON. The intervals between the vertebral arches are occupied by the yellow ligaments. They are widest in the loins, and least so in the lower por- tion of the neck and back. The spi'nal canal 71 is largest and is triangular in the neck and loins, is narrower and cylindrical in the dorsal region, and is smallest and triangular in the sacrum. The intervertebral foramina increase in size from the first to the last ; the sacral foramina successively decrease. The spaces between the spinous and transverse processes constitute the vertebral gutters, and are occupied by the extensor muscles of the back. Viewed in profile, the vertebral column presents a series of four curves, which, except in the case of the sacrum, depend on the difference in thickness between the fore and back parts of the vertebral bodies and the intervertebral disks. In the neck and loins the convexity of the curves is directed forward, in the dorsal region and pelvis backward. The strongest degree of convexity is that presented in the loins ; its lower part being produced by the promontory of the sacrum. The curvatures commence to become particularly evident with the first efforts of the child to stand or walk ; prior to this period the vertebral column being nearly straight. More or less lateral curvature is quite frequently observable in the dorsal region, most usually with the convexity toward the right. This abnormal character appears to depend on the excess of muscular action upon the side to which the convexity is directed. The sacrum is the only portion of the vertebral column which is entirely immovable, and it is through this bone that the weight of the trunk is communicated to the lower extremities. The mobility in other portions of the vertebral column varies, being greatest in the cervical region, and least in the dorsal region. The motions of the vertebral column, though very restricted, occur in all directions ; being those of flexion and extension, bending to either side, and rotation upon its axis. THE EIBS. The Eibs, 2 of which there are twelve pairs, form a series of narrow arches on each side of the trunk, extending from the dorsal vertebrae toward the sternum. Anteriorly they are prolonged by the cos'tal car'- 1 Vertebral canal ; rachidian canal ; 2 Costae ; pleurae ; pleurapophyses ; canalis medullaa spinalis ; specus pro pleuromata. medulla spinali, or vertebralis ; solen. THE SKELETON. 115 tilages. 1 The upper seven pairs join the side of the sternum through the latter, and are called true or ster'nal ribs. 2 Of the others, called false or aster'nal ribs, 3 three successively join one another and the cartilage of the last true rib, by means of their cartilages. The remaining two have their cartilages unattached, and are thence called free or floating ribs. 4 The ribs successively increase in length from the first to the eighth, and then decrease to the last one. In breadth and degree of curva- ture they gradually diminish from first to last. In direction from the vertebral column, they are first di- rected from the bodies outward and backward to the transverse processes, from thence outward and slightly forward, and subsequently more abruptly forward and inward. In proceeding from the vertebrsB they likewise incline downward, so that their anterior extremity is lower than the posterior. In the latter direction the ribs exhibit a slight twist, so that they will not lie with their whole length in con- tact with a level surface. The ribs have an outer and inner broad smooth surface ; an upper rounded border and a lower sharp one. Within the greater part of the length of the lower border there is a groove 5 for the intercostal blood-vessels. The posterior extremity of a rib is the head, 6 and this presents two articular facets, separated by a slight ridge, which articulate with the corresponding facets of a contiguous pair of vertebral bodies. The narrow part of the rib succeeding the head is its neck, 7 and this is bounded externally by the tu/bercle, 8 upon which is an articular facet for the transverse process of the lower of the two vertebra? joined by the FRONT VIEW OF THE THORAX. 1, 2, 3, the three pieces of the sternum; 4, 5, the dorsal vertebrse; 6, the first true rib; 7, its head; 8, neck ; 9, tubercle; 10, the seventh true rib ; 11, costal cartilages ; 12, the floating ribs; 13, groove for the intercostal blood-vessels. 1 Cartilagines costarum ; haemapophy- ses. 2 Costae verge ; c. genuinae ; c. sternales. 3 Costae spuriae ; c. mendosae ; c. aster- nales ; nothae costae. 4 Costae fluctuantes. 5 Sulcus costalis. 6 Capitulum costaa. 7 Cervix ; collum. 8 Tuberculum. 116 THE SKELETON. head of the rib. Externally to the tubercle is a rough mark called the angle, 1 corresponding with the point at which the rib is rather abruptly directed forward. The distance of the angle from the tubercle succes- sively increases from the first to the last rib. The anterior extremity of the rib is the most compressed portion, is obtuse at both borders, and is continuous with its costal cartilage, which, after separation by maceration, leaves an elliptical pit at the end of the bone. The broad surfaces of the ribs are so arranged in succession that the outer ones present the periphery of an oval, and the inner ones in the same manner are related to the interior of an oval. Several of the ribs present exceptional characters to those given in the general account. The first rib has no twist, has its broad surfaces directed upward and downward, and its borders, which are narrow, inward and outward. The upper surface at its fore part is marked by two slight impressions produced by the subclavian blood-vessels. The head presents but a single articular facet. The eleventh and twelfth ribs are compara- tively feebly developed; have only one articular facet to the head, and have no tubercle. The Cos'tal cartilages 2 successively increase in length from the first to the seventh, and then decrease to the last. Their direction is one of convergence toward the sternum ; the first one descends, that succeeding is horizontal, and the others gradually become more and more ascending. The outer extremity of the costal cartilages is absolutely continuous with the structure of the ribs. The inner extremity of those of the true ribs, except the first pair, forms a movable articulation with the side of the sternum. The inner end of the succeeding three pairs of cartilages is pointed and attached to the cartilage next above. The last two pairs of costal cartilages are pointed and free. Between the fifth to the eighth pair of costal cartilages, processes usually exist blending their contiguous borders together. The ribs commence ossification even before the vertebra?. They are formed from a principal piece, an epiphysis for the head, and another for the tubercle, except in the last two pairs, which have no epiphysis for the latter process. Usually after the prime of life, in the male, the costal cartilages become partially ossified, but in the female this is much less liable to occur, and then only in advanced age. 1 Angulus, or cubitus costse. 2 Cartilagines costarum ; hgemapophyses. THE SKELETON. H7 THE STERNUM. The Ster'num or breast bone 1 is situated in the median line, in front of the thorax, sloping from above downward and forward. It is long, broad, and nearly flat, and bears a general resemblance to the ancient broad-sword, from which the older anatomists called its three pieces the handle, the blade, and the point. Its anterior surface is slightly convex ; its posterior surface slightly concave. In structure it is light and spongy, and is invested with a thin layer of moderately compact substance. The handle or first piece 2 is the broadest and thickest bone of the sternum. It is irregularly hexahedral ; slightly convex in front, and slightly concave behind. Its upper border is thick, rounded, and trans- versely concave ; 3 its lower border is straight, and joins the second bone of the sternum. The upper, short, lateral border slopes off and articu- lates with the clavicle.* The lower, long, lateral border curves downward and inward ; its upper end is continuous with the first costal cartilage ; its lower end articulates with part of the second costal cartilage. The second piece or body 5 is the longest portion of the sternum. It is oblong, quadrate in form, and usually widest at its lower part. Its anterior and posterior surfaces are nearly flat, and are commonly more or less marked by several transverse lines indicating the original separa- tion of the bone into parts. Its lateral borders present successively, first, at the upper end an articular surface forming part of the articulation for the second costal cartilage, then four notches for the third to the sixth costal cartilages inclusive, and finally, at the lower end a surface for part of the seventh costal cartilage. The distance between these articulations successively decreases from above downward. The third piece or point 6 of the sternum is usually the narrowest, thinnest, and shortest portion. It is quite variable in shape, being flat, long and pointed, or ensiform; tongue-shaped, or discoidal; or it is forked. It commences ossification several years after birth, and even in advanced age is rarely entirely ossified ; hence its name of en'siform car'tilage. 7 With the commencement of its lateral border, the seventh costal cartilage partially articulates. The upper two pieces of the sternum commence ossification about the fifth or sixth month of foetal life ; and they do so from a variable number 1 Sternon ; os pectoris ; o. xiphoides ; * Incisura clavicularis. o. gladioli; o. ensiforme; o. asser;scu- 5 Corpus; blade; mesosternum. turn pectoris, or cordis ; haemal spine. 6 Processus xiphoideus; p. mucrona- 2 Manubrium; episternum. tus ; p. ensiformis ; hyposternum. 3 Incisura semilunaris ; os jugularis. 7 Cartilage ensiformis. 118 THE SKELETON. of points. At puberty the handle forms a single bone ; the body usually presents five segments, which successively co-ossify from below upward. Generally the three pieces or bones of the sternum remain separated, but frequently the upper two become united, and occasionally in old age all three are found co-ossified. The sternum is variable in its form in different individuals, principally in the proportion of length and breadth of the different pieces. Articulations of the Sternum. The three pieces of the sternum are conjoined by fibro -cartilage, and are much strengthened in their union by a thick fibrous investment, partially derived from the costo-sternal ligaments. ARTICULATIONS OF THE RIBS WITH THE VERTEBRAE AND STERNUM. Costo-vertebral articulations. The articulation between the head of the ribs and the bodies of the dorsal vertebra is surrounded with a cap'- sular lig'ament, and, except in the case of that of the first and the last two ribs, is divided into two parts by an inter artic'ular lig'ament, 1 FIG. 93. FIG. 92. ANTERIOR VIEW OF THREE DORSAL VERTEBRA AND THEIR ARTICULATION WITH THE RIBS. 1, portion of the anterior vertebral ligament ; 2, radiating liga- ment ; 3, anterior costo-transverse ligament ; 4, ar- ticulation of the head of the rib laid open, exhibit- ing the cavity divided into two by aninterarticular ligament. POSTERIOR VIEW OF FOUR DORSAL VERTEBRAE AND THEIR ARTICULATION WITH THE RIBS. 1, SUpni-Spi- nous ligament; 2, yellow ligament, seen just below the edge of the vertebral arches ; 3, anterior costo- transverse ligaments ; 4, posterior costo-transverse ligaments. which is a short band connecting the ridge on the head of the ribs with the contiguous intervertebral disk. In front the articulation is strength- ened by the ra'diating lig'ament, 2 consisting of three bands diverging 1 L. interarticulare ; 1. transversum. 2 L. capituli costoe anterius ; 1. radiatum. THE SKELETON. H9 from the head of the rib to the sides of the contiguous pair of vertebral bodies and the intervertebral disk. The slightly movable articulation between the tubercle of the upper ten ribs and the neighboring transverse processes of the dorsal vertebrae is likewise surrounded with a cap'sular lig'ament Besides this, each rib is connected with the transverse processes by three ligaments, as follows : The anterior cos'to-trans'verse lig'ament, 1 This is a membranous band connecting the neck of the rib with the transverse process above. The posterior cos'to-trans'verse lig'ament. 2 This is a short band connecting the tubercle of the ribs with the end of the contiguous trans- verse process. The middle cos'to-trans'verse lig'ament, 3 This consists of short fibres intervening between the neck of the rib and the contiguous trans- verse process. Costo-sternal articulations. The costal cartilages, except the first, form articulations with the side of the sternum surrounded by capsular ligaments and lined with synovial membranes. Behind, and especially in front, the articulations are strengthened by fibres radiating from the cos- tal cartilages upon the sternum, constituting the anterior and posterior cos'to-ster'nal lig'aments. 4 Those of the two sides blend together and with the aponeurotic origin of the pectoral muscles. A thin fibrous band connecting the seventh costal cartilage with the third piece of the sternum is called the cos'to-xi'phoid lig'ament. 5 The contiguous margins of the costal cartilages from the sixth to the ninth, if not blended together, have opposed articular surfaces surrounded with cap'sular lig'aments. THE THORAX. The Tho'rax or chest 6 is a conical or ovoidal case, with its narrower part uppermost. It is flattened before and behind, which is the reverse of the condition observable in the lower mammals generally, and hence it is that man can readily lie on his back, while the lower animals cannot. It is formed of the dorsal vertebrae, ribs, and sternum ; and its sides are also called its walls. 1 L. costo-transversale anterius; 1. 3 L. costo-trans. medius; 1 colli costse; transversarium internum; int. costo- 1. cervicum costse. transverse ligament ; 1. costo-transver- * L. costo-sternalia ant. et post. ; 1. sarium inferius. radiata. 2 L. costo-transversale posterius ; 1. & L. costo-xiphoideum. transversarium externum; ext. costo- 6 Pectus ; stethus; cassa; venter me- transverse ligament. dius; citharus; scutum pectoris ; bir; chelys. 120 THE SKELETON. The front wall of the chest, or the breast, is flatter and shorter than any other portion, and is formed of the sternum and cartilages of the true ribs. It slopes forward and downward to such an extent that the lower end of the sternum is re- moved twice the distance of the upper end from the vertebrae. The posterior wall is the back, in the most restricted use of the term. It is also flattened, is di- vided in the middle by the imbri- cating spinous processes of the dor- sal vertebrae, and is denned on each side by the angles of the ribs, which indicate the extent to which the dorsal extensor muscles reach outwardly. The lateral walls of the chest are the longest, most prominent, and convex. The cavity of the tho'rax 1 is subdivided posteriorly by the intru- sion of the bodies of the dorsal vertebrae ; and it is open above, below, and between the ribs. The superior opening of the tho'rax 2 is formed by the first dor- sal vertebra, the first pair of ribs, and the first piece of the sternum. It is reniform, with its transverse diameter more than twice as great as the antero-posterior, and with its plane inclining a little downward and forward. The inferior opening, 3 by far the largest, is formed by the last dorsal vertebra, the last pair of ribs, the cartilages of all the false ribs, and the last piece of the sternum. It is likewise reniform, with its transverse diameter about one-third greater than the antero-posterior, and with its plane inclining upward and forward. The intercostal spaces 4 increase in width anteriorly, and are occupied by muscles of the same name. The greatest circumference of the thorax is just below the middle, and not at the bottom or base. The ribs incline downward and forward in such a manner that the anterior extremity of the first rib is on a level FRONT VIEW OF THE THORAX. 1, 2. 3, the three pieces of the sternum ; 4, 5, the dorsal vertebrae ; 6, the first true rib; 7, its head; 8, neck; 9, tu- bercle ; 10, the seventh true rib ; 11, costal cartil- ages; 12, the floating ribs; 13, groove for the inter- costal blood-vessels. 1 Cavum thoracis. 2 Apertura thoracis superior. 3 Apertura thoracis inferior. 4 Spatia intercostalia. THE SKELETON. 121 with the second dorsal vertebra, the anterior extremity of the seventh rib is on a level with the tenth dorsal vertebra, and the end of the last rib is on a level with the first lumbar vertebra. The movements of the thorax consist of a moderate degree of eleva- tion and depression of the ribs and sternum, as in inspiration and expiration. From the direction of the ribs, when their anterior part is raised they assume a more horizontal position, and the diameter of the chest is increased. The thorax is more ovoidal and less compressed antero-posteriorly in the female than the male. Tight-lacing makes it still more assume the form of an oval. THE HIP OR INNOMINATE BONES. The Hip or Innominate bones, 1 though included in the account of the trunk, really belong to the lower extremities, holding the same relation to them that the shoulder bones do to the upper extremities. In the lower animals their presence is observed to be in a great measure dependent on the existence of hinder extremities. 2 Together with the sacrum, they constitute the pelvis, which incloses a portion of the diges- tive and genito-urinary apparatus. For convenience of description they are viewed as consisting of three parts : the il'ium, is'chium, and pu/bis, corresponding with the original divisions of the bones as existing in infancy. The Il'ium 3 is a broad, thick plate forming the upper part of the hip bone. Its inner side presents three surfaces : an anterior, broad, smooth concavity, called the il'iac fos'sa ;* a posterior, uneven surface, partly devoted to articulation with the sacrum, and partly to ligamentous attachment ; and an inferior, small, nearly plane surface, forming part of the true pelvis. The outer or dorsal surface of the ilium is convex at its fore part, and concave behind. It is marked by two feeble ridges, called the superior and inferior curved lines. 5 The space between them gives origin to the small gluteal muscle ; the space above them to the middle gluteal muscle, except a rough surface at the posterior superior part of the bone, which gives attachment to the great gluteal muscle. 1 Ossa innominata ; ossa anonyma ; 3 Os ilium ; os ilei ; ileum ; ileon ; o. coxarum; o. lateralia pelvis; the haunch; haunch bone. haunch bones. * Fossa iliaca. 2 In some animals hip bones exist -with- 5 Linese arcuatse ; 1. semicircularis su- out the presence of limbs, but in such perior et inferior. cases they are quite rudimentary; as in the dolphin, whale, and glass snake. 122 THE SKELETON. The upper border, or crest of the il'ium, 1 is thick and rounded, and is convex and sigmoid in its course. It gives attachment to the broad FIG. 95. FIG. 96. INNER VIEW OF THE LEFT HIP OR INNOMINATE BONE. The dotted line indicates its division into three parts : 1, the ilium, 2, the ischium, and 3, thepubis. (1, iliac fossa:) 4, crest of the ilium; 5, 6, anterior superior, and inferior spinous processes ; 7, 8, pos- terior superior, and inferior spinous processes ; 9, articular surface for the sacrum ; 10, rough surface for the attachment of ligaments. (2, body of the pubis :) 11, symphyses ; 12, horizontal, and 13, de- scending ramus ; 14, upper border of the body ; 15, spine of the pubis ; 16, pectineal line. (3, plane of the ischium :) 17, ramus of the ischium ; 18, tuber- osity; 19, spine of the ischium; 20, ilio-pubic eminence; 21, obturator foramen; 22, great sciatic notch ; 23, lesser sciatic notch. OUTER VIEW OF THE LEFT HIP OR INNOMINATE BONE 1, ilium; 2, ischium; 3, pubis. (1, dorsal surface of the ilium :) 4, crest of the ilium ; 5, 6, superior and inferior curved lines ; 7, surface of the great gluteal muscle ; 8, 9, anterior superior, and inferior spinous processes ; 10, 11, posterior superior, and inferior spinous processes. (2, body of the ischium:) 12, spine of the ischium ; 13, great sciatic notch ; 14, lesser sciatic notch ; 15, tuberosity of the is- chium ; 16, ramus of the ischium. (3, body of the pubis :) 17, horizontal ramus of the pubis ; 18, de- scending ramus; 19, acetabulum; 20, obturator foramen. muscles of the abdomen, and terminates at each end in a prominence, called the anterior superior, and posterior superior spi'nous proc'ess, 2 Below these processes is a notch, succeeded by the anterior inferior, and posterior inferior spi'nous proc'ess. 3 Following these processes are other notches : one anteriorly, terminated below by the ilio-pubic eminence ; the other posteriorly being the great sciat'ic notch. 4 1 Crista ilei. 3 P. s. ant. inf. et post, inf.; spina ant. 2 Processus spinosus ant. sup. et post. inf. et post. inf. sup.; spina ant. sup. et post. sup. 4 Incisura ischiadica major; incisura iliaca; part of the sacro-sciatic notch. THE SKELETON. 123 The Is'chium 1 forms the inferior part of the hip bone, and consists of a body and a ramus, united in the form of a hook. The body 2 is the posterior thicker portion joining the ilium. It is trilateral, one side looking outward, another inward, and the third backward. Below, it forms a strong prominence, the tuberos'ity, 3 upon which we sit, and which gives origin to the flexor muscles of the back of the thigh. Behind, the ischium possesses a strong process, the spine, 4 which separates the greater sciat'ic notch 5 above from the lesser sciat'ic notch 6 below. The ra'mus 7 of the ischium proceeds from the lower extremity of the body upward and forward to the pubis. It presents an inner and an outer surface, and an anterior thick border, which gives attachment to the crus of the penis. The Pu/bis 8 is situated at the anterior part of the hip bone, and con- sists of a body and two ra'mi or branches. The body is the inner ex- panded part, flattened before and behind, and having at its inner border an uneven articular surface, forming part of the sym/physis, or junction of both pubes. The upper part of the body forms an obtuse ridge 9 termin- ating externally in a small eminence, the spine, 10 which gives attachment to the lower end of Poupart's ligament. The horizontal ra'mus of the pubis proceeds outward from the body, and at its junction with the ilium forms the il'io-pu/bic eminence. 11 It is three sided, and presents three margins, of which one is inferior, another is obtuse and proceeds from the spine of the pubis outwardly to the acetabulum, and the third is sharp and is called the pecti'neal line, 12 This proceeds from the spine of the pubis to the inner side of the ilio- pubic eminence, and at its commencement gives attachment to Gimber- nat's ligament. The descending 1 ra'nms of the pubis proceeds outward and downward to join the ramus of the ischium. It is small and flattened from without inward. Having described the separate divisions of the hip bones, it remains to point out some anatomical characters formed by their conjunction. At the union of the three pieces of the hip bone, externally there is 1 Os ischii; os coxendicis; ischion ; 8 Os pubis; os pectinis; pecten ; epis- huckle bone ; seat bone. chion. 2 Ramus descendens. Crest ; crista pubis. 3 Tuberositas or tuber ischii ; os seden- 10 Tuberosity of the pubis ; tuberculum tarium. pubicum ; spina pubis. 4 Spina ischii : spinous process. n Ilio-pectineal protuberance ; tuber- 6 Incisura ischiadica major. culum ilio-pubicum ; tub. ilio-pectineum. 6 In. isch. minor; luna Albini. 12 Crista; pecten; linea pectinea; cris- 7 Ramus ascendens. ta ilio-pectinea. 124 THE SKELETON. situated a hemispherical or cup- shaped cavity, the acetaVulum, 1 for articulation with the head of the thigh bone. To it, the pubis contributes one-fifth, and the ilium and ischium contribute each about two-fifths. It is bounded by a prominent margin, 2 except internally, where it is deeply notched. 3 The greater part of the surface of the acetabulum is smooth and covered with cartilage, but at its bottom there is an irregular pit, 4 communicating with the notch of its margin, which is occupied by a cushion of fat. In advance of the acetabulum, between the pubis and ischium, is a large hole, the obtura'tor fora'men, 5 which is closed by a fibrous mem- brane. It is oval, with a tendency to assume a trilateral form, especially in the female. Above the position of the acetabulum is the il'io-pu/bic emi'nence, 6 corresponding with the union of the horizontal ramus of the pubis with the ilium. To the inner side of this eminence there proceeds for- ward and backward the ilio-pectineal line, which separates the true and false pelvis. Internal to the position of the acetabulum, within the pelvis, there is a vertical surface formed by the ilium and ischium, and called by obstet- ricians the plane of the is'chmm, Behind it, formed between the poste- rior inferior spinous process of the ilium and the spine of the ischium, is the great sciatic notch. The hip bone is composed of spongy substance with a moderately thick investment of compact substance, which is perforated in many places with large foramina for nutritious blood-vessels. Frequently the two plates of compact substance come into contact at the middle of the iliac fossa, and in this position are so thin as to be translucent. The hip bone is ossified from three principal pieces, corresponding with its divisions indicated, and four epiphyses. Ossification commences early in foetal life, and is not completed until after adult age. The epiphyses, which begin to appear subsequent to puberty, consist of one for the crest of the ilium, another for the tuberosity, and small ones for the anterior inferior spinous process and the pubic symphysis. 1 Cotyle ; cotyloid cavity ; fossa coty- 5 F. obturatum or obturatorium ; f. loidea; sinus coxae ; acetabulum pyxis. ovale; f. thyroideum; f. infra-pubianum; 2 Supercilium acetabuli. f. amplum pelvis. 3 Incisura acetabuli. 6 Ilio-pectineal eminence. 4 Fossa acetabuli. THE SKELETON. 125 ARTICULATIONS OF THE HIP BONES. The hip bones are immovably articulated together and with the sacrum by means of fibre-cartilaginous plates and strong ligaments. The Pu/bic sym'physis 1 is formed by the conjunction of the pubes through a thick plate of fibro-cartilage, as in the union of the vertebral bodies. It is strengthened by fibrous bands passing from one bone to the other, constituting the pu'bic lig'aments, which are named, from their relative position to the symphysis, anterior, posterior, etc. The inferior or sub-pubic ligament 2 is the strongest. FIG. 98. FIG. 97. LIGAMENTS OF THE PELVIS AND HIP JOINT. 1, pos- terior sacro-iliac ligament; 2, great sacro-sciatic ligament ; 3, small sacro-sciatic ligament ; 4, great sacro-sciatic foramen ; 5, small sacro-sciatic fora- men; 6, cotyloid ligament surrounding the border of the acetabulum ; 7, round ligament ; 8, cut edge of the capsular ligament ; 9, obturator membrane. LIGAMENTS OF THE PELVIS AND HIP JOINT. 1, lower part of the anterior vertebral ligament ; 2, pubic symphysis; 3, ilio-lumbar ligament; 4, sacro-iliac symphysis, with the anterior sacro-iliac ligament ; 5, obturator membrane ; 6, edge of the tendon of the external oblique muscle of the abdomen, techni- cally named Poupart's ligament ; 7, extension of the latter along the pectineal line named Gimbernat'a ligament; 8, capsular ligament of the hip joint; 9, a strong accessory band of the latter ligament. The Obturator mem'brane 3 is a fibrous structure, closing the obturator foramen, except at its upper and outer part, where there is an orifice* for the passage of the obturator vessels and nerve. The surfaces of the membrane give origin to the obturator muscles. The Sa'cro-il'iac sym'physis 5 is formed by the union of the corre- 1 Symphysis pubis. 2 Lig. arcuatum. 3 Membrana obturatoria ; ligamentum obturatorium ; sub-pubic membrane. 5 Symphysis sacro-iliaca. * Canalis obturatorius. 126 THE SKELETON. spending articular surfaces of the ilium and sacrum through means of fibro-cartilage, which is separable by force into two plates adhering one to each bone. The joint is strengthened by the anterior and posterior sa'cro-il'iac lig'aments. 1 The former consists of short bands uniting the contiguous bones in front of the symphysis. The latter is composed of strong bands passing transversely and obliquely from the posterior spi- nous processes and contiguous uneven surface of the ilium to the corre- sponding surface of the sacrum, behind the symphysis. The Il/io-lum/bar lig'ament 2 is a fibrous band springing from the end of the transverse process of the last lumbar vertebra, and expanding outwardly to be attached to the posterior part of the crest of the ilium. The Great sa'cro-sciat/ic lig'ament 3 is a strong triangular band attached by its base to the posterior inferior spinous process of the ilium and the margin below of the sacrum and coccyx, and by its apex to the inner margin of the tuberosity of the ischium, along which it presents a narrow expansion. The Small sa'cro-sciat'ic lig'ament, 4 I GSS strong than the preceding, springs in conjunction with it from the margin of the sacrum and coccyx, and converges to be attached to the spine of the ischium. By means of the sacro-sciatic ligaments, the sciatic notches are con- verted into the great and small sciatic fora'mma, 5 The former is oval and transmits the pyramidal muscle, the sciatic nerve, and the gluteal, pudic, and ischiatic vessels and nerves. The latter foramen is more tri- lateral, and transmits the obturator muscle, and the internal pudic vessels and nerve. THE PELVIS. The Pel'vis 6 is the basin-like portion of the trunk formed by the hip bones, the sacrum, and the coccyx. It is situated in an oblique position from the vertebral column, downward and backward, so that the end of the coccyx is nearly on a level with the middle of the pubic symphysis. By means of the il'io-pectine'al line, 7 and the upper projecting part of the sacrum, called its promontory, 8 the pelvis is divided into the superior or false, and the inferior or true pel'vis. 1 Lig. sacro-iliacum ant. et post. ; the 5 Foramina sciatica, or ischiatica, or posterior consisting of the lig. sacro-ili- ischiadicum majus et minus, or major acum longum et breve. et minor. 2 L. ilio-lumbale. 6 Choana; pyclos ; lecane. 3 L. sacro-ischiaticum majus ; 1. posti- 7 Linea arcuata interna ; 1. innomina- cus ; 1. tuberoso-sacrum. ta ; 1. terminalis. 4 Lig. sacro-ischiaticum minus, or an- 8 Promontorium. ticus, or internum; 1. spinoso-sacrum. THE SKELETON. 127 FIG. 99. The superior pel'vis 1 is formed on each side by the ilium, and is com- pleted by the lumbar verte- brae and the soft walls of the abdomen. The inferior pel'vis 2 is composed of the pubes and ischia, the sacrum and coccyx. Its cavity is curved cylindrical, nar- rowing below and becom- ing deeper from before backward. Its inlet and outlet are also called the superior and inferior straits, the ideal planes of which converge anterior- The superior strait 3 corresponds with the ilio- pectineal line and pro- montory of the sacrum, FRONT VIEW OF A FEMALE PELVIS. 1, last lumbar vertebra ; 2, intervertebral ligaments; 3, sacrum, the figure being placed on its promontory ; 4, transverse lines, indicating the original separation of the sacrum into five vertebral segments ; 5, end of the coccyx ; 6, iliac fossa; 7, 8, anterior superior, ancl inferior spinous processes; 9, acetabulum; 10, its notch on the inner side ; 11, body of the is- the projection Of Which chium; 12, tuberosity of the ischium; 13, spine of the ischium, ,. seen through the obturator foramen; 14, body of the pubis; 15, gives It a COrdlform OUt- Bymphy8i8 of the pubis; 16 , arch of the pubis; 17, upper part m1 . /. j_ j_ A. The inferior strait 4 is of the body of the pubis ; 18, spiue of the pubis ; 19, pectineal line ; 20, ilio-pubic eminence ; 21, great sacro-sciatic notch. bounded by three prominences, separated by as many notches. Of the prominences, two are lateral and correspond with the tuberosities of the ischia, and the other is formed by the sacrum and coccyx. Of the notches, one is the pu'bic arch, 5 bounded on each side by the rami of the ischium and pubis. It is triangular, and has for its apex the symphysis of the pubes. The other notches, called from their position sa'cro-sci- at'ic, by means of ligaments of the same name are converted into fora- mina likewise distinguished by the same designation. The axis of the inferior pelvis constitutes a curved line 6 passing out at the centre of the straits. 1 The great, or greater pelvis ; false pelvis ; labrum pelvis. 2 The small, or lesser pelvis ; pelvis minor; p. vera. 3 Brim of the pelvis ; apertura pelvis superior ; introitus ; angustia abdomi- nalis ; upper opening. 4 Apertura pelvis inferior ; lower open- ing ; exitus ; angustia perinaealis. 5 Arcus ossium pubis ; arch of the pubis. 6 The curve of Carus. 128 THE SKELETON. In the infant the capacity of the inferior pelvis is so small that the urinary bladder for the most part occupies the space, of the superior pelvis. SEXUAL DIFFERENCES OF THE PELVIS. The sexual differences of the pelvis are greater than in any other por- tion of the skeleton. In the female the pelvis is more capacious in its breadth and less deep than in the male. In consequence of this most important difference, the birth of the infant is easier and quicker than it could be under the opposite conditions. The bones of the pelvis are thinner and less marked by muscular attachments. The sides of the superior pelvis, formed by the ilia, are more expanded. The promontory of the sacrum is less projecting, and in consequence of this difference the superior strait is less cordiform or is more oval. The cavity of the inferior pelvis is more uniformly cylindrical, from the ischia converging less below or from their being more parallel. The depth of the inferior pelvis is less, but its breadth is greater. The diminution in depth depends on the less extent of the ischia. The sub-pubic arch is lower, wider, more obtuse at the summit, and less everted at the sides. The sacrum and coccyx are shorter and wider; the ilio-pectineal line is longer ; and the obturator foramen is more trilateral. The following table gives the comparative measurements of the inferior pelvis in the two sexes : SUPERIOR STRAIT. MALE. FEMALE. Antero-posterior diameter 1 ..... 4 inches. 4| inches. Transverse diameter 4| " 5^ " Oblique diameter . . . . '. . .4* " 4| " Circumference 15 " 16* " CAVITY. Antero-posterior diameter . . . . Transverse diameter Depth at the pubic symphysis Depth posteriorly Depth at the sides Circumference INFERIOR STRAIT. Antero-posterior diameter ; from the mobility of the coccyx capable of being extended an additional inch ......... 3| inches. 4^ inches. Transverse diameter ....... 3^ " 4^ " At the approach of the end of pregnancy, the symphyses of the pelvis undergo a slight degree of relaxation, which facilitates child-birth. 4^ inches. 4* inches. 4 " 4* " If 1* " 5 " 5 4 " 3* " 13* " 15* " Conjugate diameter. THE SKELETON. 129 THE UPPER EXTREMITIES. The Upper extremities are suspended from the thorax at the sides of the skeleton, with which they articulate only by the inner end of the clav- icle, so that when this bone is absent, as in many quadrupeds, the fore legs have no ligamentous union with the other part of the skeleton. Each upper extremity consists of two bones to the shoulder, one to the arm, two to the forearm, and twenty-nine to the wrist and hand. BONES OF THE SHOULDER. The two bones of the shoulder are the clavicle and scapula. By means of the former it is connected with the sternum and first rib, and by means of the latter with the arm bone. THE CLAYICLE. The Clavicle 1 or collar bone is situated in front of the upper part of the thorax, extended transversely between the sternum and the acromion of the scapula. It is cylindroid, with a sigmoid curve; is more curved and robust in the male, and most so in vigorous persons. The ster'nal end 2 is thickened, and presents an irregular triangular surface, partly for articu- lation with the sternum, and partly for the attach- ment of ligaments. The acro'mial end 3 is com- pressed from above down- CL ^ CLE OF THE RIGHT ^ upper yjew 1? gternal end; Ward, and has a Small ar- tion which joins the cartilage of the first rib; 3, anterior convexity ticular r SUrface for Union and line f attachment of the g reat pectoral muscle; 4, upper surface of the acromial end; 5, its articular surface; 6, anterior With the acromion. concavity, giving attachment to the deltoid muscle; 7, posterior The Upper Surface Of convexit y> gi vin g attachment to the trapezius muscle; 8, position of origin of the sterno-mastoid muscle. the clavicle is covered only by the skin and subcutaneous fascia. The lower surface is directed toward the first rib and the coracoid process of the scapula, and is marked by the ligamentous attachments with these bones. In the curva- tures of the clavicle, the convexity of its acromial extremity is directed backward ; that of the sternal extremity forward. 1 Clavicula; clavis; furcula; ligula; 2 Extremitas sternalis. osjuguli; jugulum; cleidion. 8 Extremitas acromialis. 130 THE SKELETON. The clavicle is a most important agent in maintaining the position of the upper extremity ; removing the shoulder joint a convenient distance from the thorax, thus contributing to the greater range and freedom of movement of the limb. If it is removed or broken, the shoulder is de- pressed, and the head of the arm bone falls against the side of the tho- rax and is much restricted in its movements. In animals which use the fore legs only for support, the clavicle does not exist, as in the ruminants and the horse ; its degree of development is intimately related with the freedom of movement of the fore extremi- ties of other animals. Thus it is well developed in squirrels, bats, and birds, and is feebly developed in dogs and cats. THE SCAPULA. The Scap'ula 1 or shoulder blade is situated at the upper back part of the thorax, extending from the position of the second to the seventh rib. It is broad, flat, thin, and triangular, and presents two surfaces, three borders, three angles, and three processes. Of the surfaces, the anterior 2 forms the shallow subscap'ular fos'sa, 3 which is crossed by ridges, 4 and gives attachment to the subscapular mus- cle. The posterior surface 5 is divided by a projecting plate, the spine, into two unequal parts, of which the upper and smaller is called the su'pra-spi'nous fos'sa, 6 and the lower the in'fra-spi'nous fossa; 7 both being occupied by like-named muscles. Of the borders, the superior 8 is the shortest and thinnest. At its outer part is the cor'acoid notch, 9 which is converted by a transverse fibrous band, the cor'acoid lig-ament, 10 into the cor'acoid fora 'men. 11 The posterior border 12 or base is the longest, is irregularly convex in its course, and gives attachment to muscles. The inferior border 13 inclines toward the axilla, and is thick and partially grooved. At its upper part is a rough impression produced by the attachment of the long head of the triceps extensor muscle. 1 Scapulum ; spatula ; scaptula ; pla- 6 Fossa supra-spinatus. ta; omoplata; pterygium; chelonium; 7 F. infra-spinatus. epinotion; os latum huireri; scutum tho- 8 Costa superior ; cervical border, racis; latitude humeri ; blade bone; plate 9 Incisura coracoidea ; i. scapulae ; lu- bone; spade bone; shield bone. nula; supra-scapular notch. 2 Venter. 10 Lig- coracoideum. 3 Fossa subscapularis. u Foramen coracoideum. * Costse scapulares. 12 Vertebral border. sDorsum; dorsal surface; testudo 13 Costa inferior ; axillary border. scapulae. THE SKELETON. 131 Of the angles, the superior is thin, and is formed at the conjunction of the upper border and base. The inferior angle is thick, and expanded FIG. 101. FIG. 102. THE SCAPULA OF THE LEFT SIDE, posterior view. 1, supra-spinous fossa; 2, infra-spinous fossa; 3, supe- rior border; 4, coracoid notch; 5, inferior border; 6, glenoid cavity; 7, inferior angle; 8, neck of the scapula; 9, posterior border or base ; 10, spine; 11, its triangular commencement, upon which the ten- don of the trapczius muscle moves ; 12, acromion ; 13, one of the nutritious foramina; 14, coracoid process. ANTERIOR VIEW OF THE SCAPULA. 1, ridges cross- ing the subscapular fossa ; 2, upper boundary of the latter ; 3, superior border ; 4, superior angle ; 5, co- racoid notch; 6, coracoid process; 7, acromion; 8, spine of the scapula; 9, articular surface for the clavicle ; 10, glenoid cavity ; 11, elevated bor- der of the same; 12, neck; 13, inferior border; 14, inferior angle ; 15, base ; 16, position at which the spine commences posteriorly. at its outer part, where it gives origin to the greater terete muscle. The external angle 1 is massive, and supports a vertically ovate, shallow, con- cave surface, the gle'noid cavity, 2 forming part of the shoulder joint. The cavity has an obtuse prominent border, and is supported by a nar- rowed portion of the bone, named the neck of the scap'ula, 3 Of the processes, the spine* is the most conspicuous, consisting of a strong triangular plate springing backward and a little upward from the posterior surface of the scapula and separating the supra- and infra-spi- nous fossae. Its anterior border curves over the neck of the scapula, and is thick and rounded. Its posterior border commences in a triangular expansion at the base of the bone, is thick and strong, and has attached 1 Corpus scapulae. 2 Cavitas, or fossa glenoidea ; acetabu- lum huraeri ; cavitas humeri glenoicles ; omocotyle; entyposis. 8 Cervix, or collum scapulj * Spina scapulae. 132 THE SKELETON. the trapezius and latissimus muscles. The angle of conjunction of the anterior and posterior borders is prolonged outwardly and expanded into a broad process, the acro'mion, 1 which forms the summit of the shoulder and overhangs the joint. From above the glenoid cavity the strong hook-like cor'acoid proc'ess 2 curves outwardly toward the front of the shoulder joint. Its end and base are tuberous for the attachment of ligaments, and behind it is the coracoid notch. The scapula is almost completely enveloped in muscles, and it is only the posterior border of its spine and the acromion that can be readily felt beneath the skin, and which become conspicuous in emaciated persons. The processes and borders of the bone are for the most part thick and strong. In the position of the infra- and supra-spinous fossa3 the bone is usually thin and translucent, and sometimes is even imperfect. At the base of the spine there are usually from one to three large nutritious foramina. BONES OF THE AKM AND FOREARM. A single bone, the humerus, enters into the constitution of the arm. 3 It joins the glenoid cavity of the scapula, from which it extends verti- cally, with a slight inclination inward, to join the bones of the forearm. 4 These are the radius and ulna, which lie side by side, separated by an interspace, and extend downward to the wrist with a slight inclination outward and forward. THE HUMERUS. The Hu/merus 5 or arm bone is long and cylindroid, and presents for special examination its shaft and extremities. The shaft or body is rounded at its upper, and trilateral at its lower part. The posterior surface is smooth, rounded above and flat- tened below, and is occupied its entire extent by the triceps extensor muscle. The anterior surface below inclines on each side to a ridge separating it from the posterior surface, and is occupied by the brachial muscle. Near the middle of the shaft internally, is a slight roughness 1 Aeromium ; acrocolium ; os acromii ; 3 Brachium. humerus, or armus summus ; caput scap- * Antibrachium. ulse ; mucro humeri ; rostrum porcinum. 5 Os brachii ; os brachiale ; os humeri ; 2 Processus coracoideus ; p. uncinatus; os adjutorium; brachium ; lacertus; p. cornicularis ; p. anchoralis ; p. rostri- shoulder bone. formis ; p. ancyroides. THE SKELETON. 133 produced by the insertion of the coraco-brachial muscle. Above the middle, on the outer aspect, is a broad, superfi- ^ ^ cial, rough eminence, 1 into which the deltoid muscle is inserted. Between this eminence and the ridge descending to the outer condyle, the shaft presents a slight spiral tract, from its upper back part outwardly to its lower front part, indicating the course of the supe- rior profound artery and the musculo-spiral nerve. At the upper third of the shaft is a longitudinal gutter, the bicip'ital groove, 2 which accommodates the tendon of the long head of the biceps muscle. The groove is bounded by ridges, 3 of which the outer one gives attachment to the great pectoral muscle, and the inner one to the latissimus and greater terete muscles. The upper extremity of the bone expands and supports a large hemispherical eminence, the head, 4 which is directed backward and inward, and forms part of the shoulder joint. To the outer side of the head, and separated from it by a slight groove corresponding with the neck 5 Of the bone, are the tliberOS'itieS, 4, greater tuberosity; 5, lesser tub- separated from eaeh other by the bicipital S^y^'SEfc groove. The greater tuberosity 6 is external ing attachment to muscles ; 9, posi- to the other, and at its upper part presents t^^ three impressions for the attachment of the men ; 11, articular eminence for the supra- and infra-spinous and lesser terete mus- radius ' 12 ' trochlea for the ulna; 13 > x 14, external and internal condyles ; cles. The smaller tuberosity 7 gives attachment 15, to the subscapular muscle. Surgical writers apply the term neck 8 to that portion of the bone just below the tuberosities, which, though not anatomically correct, is convenient for practical purposes. The lower extremity of the humerus is expanded laterally, and pre- sents at the sides prominent tuberosities, the con'dyles, from which condyioid ridges ascending from the latter; 17 ' f 88a for the coronoid process of the ulna. 1 Tuberositas. 2 Sulcus, or fossa bicipitalis ; sulcus intertubercularis. 3 Bicipital ridges ; spina tuberculi ma- joris et minoris. 4 Caput. 5 Cervix humeri anatomicum. 6 Tuberculum majus. 7 Tuberculum minus. 8 Cervix humeri chirurgicum. 134 THE SKELETON. ascend the con'dyloid ridges. The internal con'dyle 1 is more promi- nent than the other, gives attachment to the internal lateral ligament of the elbow joint, and gives origin to the short pronator and most of the flexor muscles on the inner part of % the forearm. The external con'- dyle 2 gives attachment to the external lateral ligament, and the ridge above it, more prominent than the opposite one, gives origin to the supinator and extensor muscles on the outer and back part of the forearm. Between the condyles is the articular surface for the bones of the fore- arm. The outer portion of this surface is" a convex eminence 3 adapted to the head of the radius. The inner portion, the troch/lea, as expressed by the name, is pulley-like, and articulates with the ulna. Above the front of the trochlea is a pit 4 which accommodates the point of the coro- noid process of the ulna in the flexion of the forearm; and above it posteriorly is a more extensive fossa 5 , which receives the olecranon in extension of the forearm. The canal for the nutritious artery of the marrow descends at the lower third of the shaft internally. THE ULNA. The TJl'na 6 occupies the inner side of the forearm, and is a little longer than the radius. It is prisnioid in form, and diminishes toward its lower extremity. Its shaft presents three surfaces separated by prominent borders. The anterior surface is slightly depressed, and gives origin to the deep flexor of the fingers The inner surface above is expanded for the origin of the latter muscle, and below is rounded and subcutaneous. The posterior surface above presents an elongated, shallow depression, which accom- modates the anconeus muscle, and below this a flattened surface for the extensor muscles of the thumb. Of the three borders, the inner two are obtuse, and the outer one is acute and gives attachment to the inter- osseous membrane. The upper extremity, which is the thickest portion of the ulna, term- inates in two robust processes inclosing the articular surface for the 1 Condylus interims ; c. flexorius. 5 Fovea supra-trochlearis posterior ; 2 Condylus extensus ; c. extensorius. greater sigmoid cavity. 3 Eminentia capitata ; capitellum ; the 6 Cubitus; focile majus or inferius; little head; rotula. canna major brachii; os cubiti inferius; 4 Fovea supra-trochlearis anterior; cubit; os procubitale; arundo brachii lesser sigmoid cavity. major; olene. THE SKELETON. 135 FIG. 104. humerus. The posterior and larger process, the olec'ranon, 1 is on a line with the shaft of the bone. Its upper part is truncated and receives the insertion of the triceps extensor muscle. Its back part presents a tri- lateral surface, which is subcutaneous. The cor'onoid process 2 projects from the front of the bone, and is roughened 3 at the fore part of its base for the insertion of the brachial muscle. Between the olecranon and coronoid processes is the greater sig'- moid cavity, 4 which articulates with the trochlea of the humerus. Its outer side is continuous with the lesser sig'moid cavity, 5 a transverse concave surface, which ar- ticulates with the head of the radius. The lower extremity of the ulna is narrow and cylin- droid. It terminates in a rounded head articulating with the radius, and a coni- cal sty'loid process, 6 to which is attached the internal lat- eral ligament of the wrist. Between the styloid proc- ess and head is a depression, into which is inserted a fibro- cartilage separating the ra- dio-ulnar from the radio-car- pal articulation. Behind the styloid process is a groove which transmits the tendon of the ulno-carpal extensor. THE TWO BONES OF THE LEFT FORE- ARM, viewed in front; the ulna to the right and the radius to the left of the figure. 1, shaft of the ulna; 2, greater sigmoid cavity ; 3, lesser sigmoid cavity articulating with the head of the radius; 4, olecra- non; 5, coronoid process; 6, nutri- tious foramen ; 7, sharp ridges of both bones of the forearm for the attachment of the interosseous membrane; 8, head of the ulna; 9, styloid process; 10, shaft of the radius ; 11, head of the same ; 12, neck ; 13, tuberosity ; 14, rough- ened attachment of the terete pro- nator muscle; 15, carpal extremity of the bone ; 16, its styloid process. THE RADIUS. The Ra'dius 7 is placed at the outer side of the ulna, and extends a little lower in the forearm. Its shaft is trilateral, with an acute border internally for the attach- 1 Olecranon; o. mobile; olecranum; acrolenion; ancon; processus anconaeus; p. uncinatus ulnae ; glans ulnae ; corona ulnae; corona posterior ulnae; addita- mentum necatum, or uncatum ulnae ; ver- tex cubiti; patella fixa; rostrum exter- num, or posterius ; top of the cubit. 2 Processus coronoideus. 3 Tuberositas ulnae. 4 Cavitas sigmoidea major; c. lunata major; semilunar fossa: olecranoid cav- ity- 5 Cavitas sigmoidea minor; c. lunata minor. 6 Processus styloideus. 7 Manubrium manus ; focile minus, or superius ; additamentum ulnae ; canna minor ; cercis ; os ad cubitale ; arunclo brachii minor ; parapechyon. 136 THE SKELETON. nient of the interosseous membrane. The external surface is rounded, and near its middle is impressed by the insertion of the terete pronator muscle. The anterior surface is flattened, expands below, and is slightly grooved at the middle for the origin of the long flexor of the thumb. The posterior surface is rounded above, and is flattened below, where it accommodates the extensor of the thumb. The upper extremity of the bone in front presents a rough eminence, the tuberos'ity, 1 into which the biceps muscle is inserted. Above it is the neck, 2 and this supports a discoidal head, 3 the wide margin of which articulates with the ulna, and the upper concave surface with the humerus. The lower extremity of the radius is its thickest portion. In front, it is broad and depressed, and bounded below by a prominent ridge giving attachment to the capsular ligament of the wrist. Behind, it is irregu- larly convex, and exhibits a narrow groove separating two broad ones, all of which transmit extensor tendons. Its outer side presents another broad groove, which likewise transmits tendons. Below the latter groove is a pyramidal eminence, the sty'loid process, 4 with which the external lateral ligament of the wrist is connected. On the inner side of the lower extremity is a transverse excavation, the semilunar cavity, 5 for articulation with the head of the ulna. Below is a large concavity, the carpal articular surface, 6 which is divided by a slight ridge into two parts, corresponding with the position of the scaphoid and lunar bones. The canal for the nutritious artery of the marrow, in both bones of the forearm, ascends from the front of their upper third. BONES OF THE HAND. The bones of the hand are situated in the same general plane with those of the forearm, and are subdivided into those of the carpus, of which there are eight ; of the metacarpus, of which there are five ; and of the fingers, of which there are sixteen. BONES OF THE CAEPUS. The Carpal bones,' or those of the carpus or wrist, 8 eight in number, are arranged in two rows, of which one joins the forearm, the other the metacarpus. Those of the first row, indicated from the outer side of 1 Tuberositas ; bicipital tuberosity. 5 Incisura semilunaris. 2 Cervix; collum. 6 Fossa scaphoidea; f. navicularis. 3 Caput. 7 Ossa carpi. 4 Processus styloideus. 8 Carpismus; brachiale; raseta. THE SKELETON. 137 FIG. 105. the wrist, are the scaphoid, lunar, cuneiform, and pisiform bones ; and those of the second row, in the same direction, are the trapezial, trape- zoid, capitate, and unciform bones. The Scaphoid bone 1 is the largest of the first row of the carpus, and is oblique in its position. It is oblong, concavo- convex, with a tubercle on the outer end for the attachment of the annular liga- ment. It articulates with the radius above, the lunar bone within, and the trapezial, trapezoid, and capitate bones below. The Lunar bone 2 is the second in size of the first carpal row, and is square and concavo-convex. It articulates with the radius above, the scaphoid bone on its outer, and the cuneiform bone on its inner side, and the capitate and unciform bones below. The Cu/neiforin bone 3 is irregularly pyramidal, and articulates with the lunar and unciform bones on its outer side, and the pisiform bone in front. The Pisiform bone, 4 irregularly round- ed, is the smallest of the first carpal row, and articulates alone with the cuneiform bone. The Trape'zial bone 5 is the third in size of the second carpal row, and is irregular in form. In front it has a groove, which accommo- dates the tendon of the radio-carpal flexor, bounded by a ridge exter- nally, which gives attachment to the annular ligament. It articulates above with the scaphoid bone, below with the first metacarpal bone, and on the inner side with the trapezoid and second metacarpal bones. The Trap'ezoid bone 6 is the smallest of the second carpal row, and is BONES OF THE CARPUS, and those with which they articulate ; right hand, poste- rior view. Of the npper bones U is the lower end of the ulna, and II is the lower end of the radius ; F indicates the posi- tion of a nbro-cartilage which separates the radio-carpal from the radio-ulnar ar- ticulation. Of the bones of the carpus, in the first row, S is the scaphoid, L the lu- nar; C the cuneiform, and P the pisiform bone ; and in the second row, T T are the trapezial and trapezoid bones, 7 the capi- tate, and U the unciform bones. Below, are the bases of the metacarpal bones. 1 Os scaphoideuin; os scaphoides; os naviculare ; os cotyloides ; os cymbi- forme ; boat-like bone. 2 Os lunatum, or lunare ; os semiluna- tum, or semilunare. 3 Os cuneiforme ; os triquetrum ; os pyramidale ; os cubitale ; os triangu- lare. 4 Os pisiforme ; os subrotundum ; os orbiculare ; os lentiforme ; os extra or- dinem carpi. 5 Trapezium; os trapezium, or trape- zoides; os multangulum majus; os rhom- boides. 6 Os trapezoides ; os multangulum mi- nus ; os trapezium ; os pyramidale. 138 THE SKELETON. an irregular truncated pyramid, wedged, with its narrow end forward, be- tween the scaphoid bone above and the second metacarpal bone below, the trapezial bone on its outer side and the capitate bone on its inner side. The Cap'itate bone, 1 the largest of the second carpal row, has a promi- nent convex head articulating with the scaphoid, lunar, and unciform bones, and an irregular cubical base joining the trapezoid and unciforrn bones at the sides, and the intermediate three metacarpal bones below. The TJn/ciform bone, 2 the second in size of the second carpal row, is irregularly quadrate, and has a broad hook-like process in front for the attachment of the annular ligament. It articulates above with the lunar and cuneiform bones, on its outer side with the capitate bone, and below with the last pair of metacarpal bones. All the carpal bones are composed of spongy substance, with a thin layer of compact substance. Associated, the bones of the carpus form a convexity on the dorsal surface, and a concavity toward the palmar surface. The concavity on the inner side is bounded by the pisiform bone and the hook-like process of the unciform bone ; on the outer side by the tuberosity of the scaphoid bone and the ridge of the trapezial bone. Between the two sides a strong fibrous band, the anterior annular ligament, is extended, con- verting the carpal concavity into a canal, through which the flexor ten- dons reach the palm of the hand. The upper border of the carpus, as formed by the scaphoid, lunar, and cuneiform bones, is convex, and forms the lower part of the radio-ca-rpal articulation, with which the pisiform bone has no connection. The lower border of the carpus forms an irregular transverse plane, with which the metacarpus articulates. The capitate and unciform bones together form a convex prominence received into a concavity formed by the scaphoid, lunar, and cuneiform bones, an arrangement of the two rows of carpal bones which contributes to the strength of their articu- lation. BONES OF THE METACAEPUS. The Metacar'pal bones, 3 or those which compose the metacarpus, 4 correspond in number with the fingers, which they join below. They belong to the class of long bones, and are slightly bent forward. Their shaft is trilateral, convex behind, and sloping off on each side 1 Os capitatum; os magnum. In some 3 Ossa metacarpi. animals the smallest bone of the wrist. 4 Metacarpion ; postcarpium ; postbra- 2 Os unciforme, or uncinatum; os ha- chiale; torsus manus. matum ; os cuneiforme. THE SKELETON. 139 FIG. 106. anteriorly. Their upper extremity or base is quadrate, and varies in character with the difference of articulation with the carpus. Their lower extremity forms a spheroidal head, 1 with a pit and pair of tuber- cles on each side for ligamentous attachment. The metacarpal bone of the thumb 2 is the shortest and most robust. It is also disconnected and divergent from the others. The succeeding bones gradually dimin- ish in size to the last, and lie nearly parallel to one another. They are articulated at their contiguous ex- tremities, and form the least mov- able portion of the hand. The spaces between the meta- carpal bones are called inter- osseous, are numbered from with- out inward, and are occupied by muscles. BONES OF THE FINGERS. THE IEFT HAND, viewed in front, or on the palmar surface. 1, scaphoid bone ; 2, semilunar ; 3, cunei- form; -J, pisiform; 5, trapezial; 6, groove in the latter; 7, trapezoid; 8, capitate; 9, unciform; 10, the five metacarpal bones; 11, first row of pha- langes of the fingers; 12, second row; 13, las.t row ; 14, 15, phalanges of the thumb. The Fingers 3 are named, in suc- cession, the thumb, 4 the index or forefinger, 5 the middle finger, 6 the ring finger, 7 and the little finger. 8 Each has three bones, called pha- lan'ges, 9 or joints, except the thumb, which has two. The middle finger is the longest, the index and ring fingers are next in length and nearly equal. The three bones of the little finger are longer than the two of the thumb, but these are much more robust, and the last phal'- anx of the latter is larger than the corresponding bone of any of the other fingers. 1 Capitulum. 2 Os metacarpi pollicis. 3 Digiti, dactyli. 4 Pollex; allus pollex; digit us primus, or magnus : promanus ; anticheir ; ma- ims parva majori adjutrix. 5 Digitus index, secundus, salutaris, or demonstratorius ; indicator ; demon- strator ; lichanos. 6 Digitus medius, tevtius, famosus, in- famis, impudicus, obscoenus, or verpus ; long finger. 7 Digitus annularis, quartos, medicus, or cordis ; paramesos ; iatricus. 8 Digitus parvus, minimus, quintus, auricularis, myops, or otites. 9 Phalangial bones ; oesa, nodi, inter- nodia, articuli, condyli, agmina, acies, scutulee, or scytalides digitorum manus. 140 THE SKELETON. The first row of phalan'ges 1 are the largest. They have a demi- cylindrical shaft, convex behind and flattened in front, with a ridge on each side for the attachment of the vaginal ligaments. The upper extremity or base is the most expanded portion of these bones, and supports a concave articular surface for the head of the metacarpal bones, and on each side a tubercle for the attachment of lateral liga- ments. The inferior extremity presents a pulley-like articular surface, or troch'lea, for the second phalanges, and a slight fossa on each side for lateral ligaments. The second row of phalan'ges 2 are constructed like those of the first row, except that their upper extremity supports a double concavity, to correspond with the trochlea of the former. The third row of phalanges 3 are the shortest. Their base is con- structed like that of the second row, their shaft is compressed conical, and they end in a rough tuberosity for the attachment of the soft tips of the fingers. In front of the head of the metacarpal bone of the thumb are placed, side by side, the two ses'amoid bones. 4 They are oval, with a palmar convex surface enveloped in the tendon of the short flexor of the thumb, and with an articular facet moving upon the head of the metacarpal bone. THE HAND. The Hand at rest occupies the same plane as the forearm, but by means of the mobility of the radio-carpal articulation or wrist joint it may be brought nearly to a right angle before and behind, and also may be moved at an obtuse angle outward and inward. The dorsal surface or back of the hand is convex. When the hand is closed as in forming the fist, the heads of the metacarpal bones and extremities of the phalanges become prominent, as the knuckles. The inner or palmar surface is concave, and is rendered more so by the flexion of the fingers. The concavity of the metacarpus is the basis of the palm 5 or hollow of the hand. The fingers may all be flexed or bent inward at a right angle to the metacarpus, but cannot be extended or bent backward beyond the line of the latter. They are all capable of convergence and divergence, or of adduction and abduction. The phalanges may be flexed at right 1 Metacarpal phalanges ; procondyli. * Ossa sesamoidea. 2 Middle phalanges ; mesocondyli. 5 Palma; vola; platea; thenar; pocu- 8 Phalanges unguium ; metacondyli. lum; patera; supellex Diogenis. THE SKELETON. 141 angles with one another, and extended back to their former straight line, but have no other movement. From the mobility of the first metacarpal on the trapezial bone, the thumb is opposable to the other fingers, and enjoys a greater range of movement. The different length of the fingers makes their tips cor- respond with the hollow of the hand when this is closed, and perhaps adapts them better for seizing objects of varied forms ; and thus when a spherical body is clasped it will be found that the tips of the fingers are brought to the same plane. DEVELOPMENT OF THE BONES OF THE UPPER EXTREMITIES. The clavicle commences to ossify earlier than any other bone. It is developed from a principal piece, and an epiphysis which appears at the sternal end on the approach of adult age. The scapula commences ossification about the same time as the vert- ebrae. It is formed from a principal piece, and several epiphyses added subsequent to birth. The acromion and coracoid process are each formed from two epiphyses, another is developed at the lower angle, and one along the base of the scapula. The humerus commences to ossify after the clavicle, and before the vertebrae. At birth the shaft is ossified, but the extremities are car- tilaginous. The head and tuberosities are formed from two ossific centres ; the condyles and lower articular extremity from four centres. The radius and ulna begin to ossify shortly after the humerus. Their extremities are cartilaginous at birth, and an epiphysis is formed for each. The carpus is cartilaginous at birth, and ossification commences with the capitate bone during the first year. Each bone is developed from a single ossific centre. At birth the shaft of the metacarpal bones and phalanges is ossified. Subsequently the head of the inner four metacarpal bones is formed as an epiphysis ; but in the first metacarpal bone and the phalanges, it is the base which appears as an epiphysis. ARTICULATIONS AND MOVEMENTS OF THE UPPER EXTREMITY. THE STERNO-CLAVICULAR ARTICULATION. The joint formed between the upper angle of the sternum and the end of the clavicle is surrounded by a cap'sular lig'ament, the stronger por- 142 THE SKELETON. tions of which constitute the anterior and posterior ster'no-clavic'- ular lig'aments. The joint is divided into two parts by a biconcave inter-artic'ular fi'bro-car'tilage, FIG. 107. which is attached by its margin to the capsular ligament, the firskcos- tal cartilage, and the upper border of the clavicle. The sterno-clavicular articulation is further strengthened by two ac- cessory ligaments: the inter-clav- ic'ular lig'ament, 1 a narrow band connecting both clavicles across STERNO-CLAVICULAR, COSTO-CLAVICULAR, AND cos- , -, D ,-. TO-STERNAL ARTICULATES. 1, capsular ligament the U PP 6r P art f the Sternum J and of the sterno-clavicular articulation ; 2, inter-clav- the COS'tO-Clavic'lllar ligament, 2 a icular ligament ; 3, costoclavicular ligament; 4, ^ ^^ Connecting the first inter-articular nbro-cartilage ; 5, anterior costo- stemai ligaments. costal cartilage with the under part of the clavicle. Notwithstanding the strong ligamentous union of this joint, which is the only one between the trunk and the upper extremity, it possesses a considerable degree of mobility in every direction. In this motion the entire limb participates, while the sternum is passive. THE SCAPULO-CLAVICULAR ARTICULATION. The joint formed between the acromion and clavicle is surrounded by a cap'sular lig'ament, the stronger portions of which are the superior and inferior acro'mio-clavic'ular lig'aments. It possesses but little mobility, end is further restricted by the cor'aco-clavic'ular ligament, 3 which consists of two strong fibrous bands passing between the base of the coracoid process and the under surface of the clavicle. In the movements of the bones of the shoulder the centre of motion is the sterno-clavicular articulation. The clavicle and scapula from this point move upward and downward, forward and backward. In the movements of the scapula, it glides upward and downward, or forward and outward ; or it rotates on its axis, as in the shrugging of the shoul- ders. 1 L. interclaviculare. 3 L - coraco-claviculare ; 1. conoides et 2 L. costo-claviculare ; 1. rhomboides. trapezoides ; 1. scapulae commune con- oides et trapezoides. THE SKELETON. 143 FIG. 108. THE SHOULDER JOINT. The Scapulo-humeral articulation or shoulder joint is surrounded by a thin, loose cap'sular lig'ament, 1 which is attached above to the margin of the glenoid cavity, and below to the neck of the humerus. Its upper part is much strengthened by a broad band, the cor'aco-hu'- meral lig'ament, 2 which extends between the coracoid process and the greater tuberosity of the humerus. The shoulder joint is the most movable one of the body; possessing a wide range of motion in every di- rection. From this circumstance it is very liable to dislocation, not- withstanding its many means of protection. The head of the humerus has more than three times as much sur- face as the glenoid cavity upon which it moves. To deepen the cavity, a prismoid, fibre-cartil- aginous band, the gle'noid lig'- ament, 3 is attached around its mar- gin. The upper part of this lig- ament gives origin to the tendon of the long head of the biceps flexor muscle, which passes through the shoulder joint to the bicipital groove of the humerus, and acts functionally the part of a ligament. As it passes through the joint it is separated from the cavity by a reflection of the synovial membrane. A strong, triangular, fibrous band, the cor'aco-acromial ligament, 4 is attached by its apex to the acromion, and by its base to the coracoid process. The two processes thus associated form a wide arch above the shoulder joint, which prevents the dislocation of the humerus in this direc- tion, unless the arch is broken. The deltoid muscle also contributes greatly to the strength and protection of the upper part of the shoulder joint. In front and behind, the latter is closely enveloped by the tendons of the subscapular, supra- and infra-spinous, and lesser terete muscles, as SCAPULO-CLAVICULAR AND SCAPULO-HUMERAL AR- TICULATIONS. 1, acromio-clavicular articulation, surrounded with its capsular ligament ; 2, coraco- clavicular ligament ; 3, coraco-acromial ligament; 4, coracoid ligament ; 5, capsular ligament of the shoulder joint; t>, coraco-humeral liganrent; 7, ten- don of the biceps flexor muscle. 1 L. capsulare magnum. 2 L. ascititium ; accessory ligament. 3 L. glenoides. * L. coraco-acromiale ; 1. triangulare ; 1. scapulae proprium anterius. 144 THE SKELETON. they proceed to be inserted into the tuberosities of the humerus. Infe- riorly the joint is in relation with the long head of the triceps extensor muscle. If the muscles surrounding the shoulder joint are detached, on account of the looseness of the capsular ligament, the head of the humerus falls nearly an inch below its usual point of contact with the glenoid cavity. The movements of the shoulder joint are forward, backward, outward, upward, and downward, and those of circumduction and rotation. THE ELBOW JOINT. The Elbow joint is formed between the humerus and both bones of the forearm, is lined with a single synovial membrane, and is inclosed by a capsular ligament strengthened with lateral ligaments. FIG. 109. FIG. 110. THE ELBOW JOINT, right side, viewed antero-inter- nally. 1, the capsular ligament in front ; 2, inter- nal lateral ligament; 3, annular ligament; 4, round ligament; 5, interosseous membrane; 6, internal condyle. THE SAME ELBOW JOINT, viewed externally. 1, posterior surface of the humerus ; 2, ulna ; 3, ra- dius; 4, external lateral ligament; 5, 6, annular ligament; 7, 8, capsular ligament; 9, interosseous membrane. The cap'sular lig'ament, 1 thin and loose, is attached above the articu- lar surface of the humerus, including the pits for the accommodation of the olecranon and coronoid process ; and is attached below to the margin of the sigmoid cavities of the ulna and to the annular ligament. Its back portion is much weaker than its fore part. Membrana capsularis cubiti. THE SKELETON. 145 The internal lateral ligament 1 is a strong band radiating from the internal condyle of the humerus to the inner margin of the greater sig- moid cavity of the ulna, between the olecranon and coronoid process. The external lateral ligament 2 is a narrow band extended between the external condyle and the annular ligament surrounding the head of the radius. The ordinary movements of the bones of the forearm upon the humerus are those of flexion and extension. The motions of the ulna are restricted to these alone, but the radius has in addition a rotary movement occur- ring upon the ulna and humerus together. THE SUPERIOR RADIO-ULNAR ARTICULATION. The superior radio-ulnar articulation forms part of the elbow joint, one synovial membrane and capsular ligament being common to both. The head of the radius and the lesser sigmoid cavity of the ulna form this articulation, the former being surrounded by a strong fibrous band, the an'nular ligament, 3 the extremities of which are attached to the ulna before and behind the latter cavity. THE MIDDLE RADIO-ULNAR ARTICULATION. The lower four-fifths of the interval of the radius and ulna are occu- pied by the interos'seous membrane, 4 which is thin but strong, and is composed of oblique fibres descending from the sharp edge of the radius to the opposed edge of the ulna. It is perforated by blood-vessels, and serves to give origin to some of the muscles of the forearm, as well as to connect the bones. At the upper part of the interosseous space an oblique band, the round ligament, 5 descends from the coronoid process of the ulna to the radius below its tuberosity. THE INFERIOR RADIO-ULNAR ARTICULATION. The inferior radio-ulnar articulation is separated from the wrist joint by a triangular, interarticular fibro-cartilage, the base of which is attached to the lower margin of the semilunar cavity of the radius, and the apex to the pit between the styloid process and head of the ulna. This ar- ticulation is surrounded by a loose capsular ligament 6 connected witji the articular margins of the radius, ulna, and fibro-cartilage. 1 L. laterale internum; 1. brachio-cu- 4 L. interosseum;membranainterossea. bitale; 1. radiatum ; 1. triangulare. 5 L. teres; 1. obliquum; chorda trans- ' 2 L. laterale externum ; 1. brachio-ra- versalis. 6 Membrana capsularis sacciformis. 3 L. annulare ; 1. orbiculare. 10 146 THE SKELETON. The radius rotates inwardly upon the ulna and becomes obliquely crossed in front of it. The hand follows the motion of the radius, in the pendant condition of the upper extremity the palm becoming directed backward ; and this constitutes the movement of pronation. The reverse motion, by which the radius assumes a position parallel to the outer side of the ulna, and the palm of the hand is directed forward, is called that of supination. In these movements of the radius, its head rotates upon the humerus and the lesser sigmoid cavity of the ulna within the annular ligament, and its lower extremity rotates upon the head of the ulna. FlG 111 THE WRIST JOINT, OR RADIO-CARPAL ARTICULATION. The Wrist joint is formed above by the radius and triangular fibro- cartilage connecting it LIGAMENTS OF THE WRIST AND . ., , HAND, anterior view. 1, lower With the Ulna J and belOW part of the interosseous mem- by the Scaphoid, lunar, brane; 2, lower radio-ulnar ar- j -f> > ticulation inclosed byacapsu- &nd CUneitorm bonCS. It lar ligament; 3, fore part of the ig inclosed by a loOSC radio-carpal joint inclosed by . , , . . a capsular ligament; 4, exter- Ca P SUlar il S ament COn- nal lateral ligament of the nCCted with the COntigU- wrist; 5 internal lateral liga- margins Q f the ar . ment; 6, palmar portion of the capsular ligament of the ticulai* SUrfaCCS. It is carpus; 7, pisiform bone with strengthened by a strong its capsular ligament ; 8, pal- mar portion of the capsular rounded, internal lateral ligament connecting the car- Jjp-QTYie pus with the base of the meta- carpus; 9, capsular ligament StylOlu of the trapezial arid metacar- ^[^, pal bone of the thumb ; 10, pal- mar or anterior ligament of bone ; and a Strong CX- the metacarpo-phalangial ar- temal lateral ligament, 3 ticulation of the thumb; 11, external lateral ligament of extended between the Sty- the same joint; 12, palmar or 1 J(J proCCSS of the 1'adlUS anterior ligament of the cor- , , , . , , responding joint of the index &nd the SCapllOld bone, finger, represented as removed A Single SynOVial mem- in the other fingers; 13, lateral ligaments of the same articulation; ^ rane ]j ne t j ie ra( Ji . car . 14, transverse ligaments connecting the heads of the contiguous metacarpal bones; 15, 16, palmar or anterior ligaments and lateral pal articulation, and nei- ligaments of the phalangial articulations. t j ier CO mmUllicateS With the radio-ulnar articulation nor extends between that of the carpal bones. 1 Anterior and posterior radio-carpal 2 L. laterale internum; 1. laterale ul- ligaments ; 1. accessorium rectum et ob- nare ; funiculus ligaraentosus. liquum et rhomboideum ; membrana ar- 3 L. laterale externum ; 1. laterale ra- ticuli cubiti et carpi capsularis. diale. , 2 Connecting tllC & prOCCSS of the Q cuneiform THE SKELETON. 147 The movements of the wrist joint are flexion and extension, abduc- tion and adduction, and circurnduction. The turning of the hand de- pends on the rotation of the radius. THE INTERCARPAL AND CARPO-METACARPAL ARTICU- LATIONS. The pisiform bone forms a distinct joint with the cuneiform bone, sur- rounded by a strong capsular ligament lined with synovial membrane. The scaphoid, lunar, and cuneiform bones of the first row of the carpus are connected at their upper part by intervening interos'seous liga- ments. In the same manner the trapezoid, capitate, and unciform bones of the second row are connected at their middle, and this is likewise the case with the bases of the inner four metacarpal bones. All the carpal bones except the pisiform bone, and the bases of all the metacarpals, except that of the thumb, are connected with one another by short fibrous bands constituting the pal'mar and dor'sal ligaments. The association of these ligaments forms a sort of capsular ligament investing the carpus and base of the metacarpus. A single synovial membrane lines the intercarpal and carpo-metacarpal articulations. These joints possess but little mobility, except the one between the two rows of carpal bones, which has a hinge-like motion. The metacarpal bone of the thumb forms, with the trapezial bone, a freely movable joint surrounded with a capsular ligament. Each articu- lating surface is convex in one direction and concave in the other, and the two surfaces are applied in a crossing manner, allowing the meta- carpal bone to be moved backward or forward, inward or outward, thus rendering the thumb opposable to the other fingers. The heads of the inner four metacarpal bones are associated in front by thin and rather loose transverse ligaments, THE METACARPO-PHALANGIAL, AND PHALANGIAL ARTICU- LATIONS. The metacarpo-phalangial, and phalangial articulations, are con- nected by strong lateral ligaments, which descend from the sides of the bones above, obliquely forward to the sides of the bones below. The fore part of these articulations is protected by a thick, fibro-cartilaginous palmar ligament, 1 extended between the position of the lateral liga- ments. It is firmly attached to the margin of the bone below the joint, and but slightly to that above ; and it is grooved on its palmar aspect 1 Anterior ligament. 148 THE SKELETON. for the passage of the flexor tendons. The back part of these articula- tions is covered by the expanded extensor tendons, which act in this po- sition as ligaments. The spheroidal head of the metacarpal bones, and the single concavity of the bases of the first row of phalanges, permit the movements of flexion and extension, abduction and adduction. The phalangial articulations or finger joints possess only the move- ments of flexion and extension. THE LOWER EXTREMITY. The lower extremity extends from below the pelvis, with which it articulates by means of the head of the thigh bone. Each consists of a single bone to the thigh, one to the knee, two to the leg, and twenty- eight to the foot. THE FEMUR. The Fe'nmr, or thigh bone, 1 is the largest and longest bone of the skeleton, and extends from the hip bone downward, with an inward inclination, to the tibia. The shaft is cylindrical, with a prominent crest behind, called the as'per- ous ridge, (linea aspera.) Its front and sides are smooth, and occupied by the quadriceps extensor muscle. The asperous ridge, for the attachment of muscles, is acute at the middle, and is rough only at its upper part, which diverges in two divisions to the trochanters. Its lower part is less well developed, and diverges in two divisions to the condyles, in- closing a triangular surface forming the basis of the popliteal space. The upper extremity of the shaft terminates in two processes, called trochan'ters, 2 The greater trochan'ter is situated at the highest part of the shaft externally. It is convex and rugged on its outer surface, and presents an oblique ridge for the attachment of the middle gluteal muscle. Its inner surface, less extensive, exhibits a pit, the trochanter'ic fos'sa, 3 into which the small rotary muscles of the thigh are inserted. The smaller trochan'ter 4 is a rounded eminence situated at the posterior and inner side of the bone, and gives attachment to the tendon of the psoas and iliac muscles. In front and behind, the trochanters are conjoined by the intertro- chanter'ic ridges, of which the posterior is much the most prominent, 1 Os femoris ; meriura.' 3 Fossa trochanterica. 2 Trochanteres; rotatores. * Lineae trochantericse. THE SKELETON. 149 FIG. 112. and gives attachment to the quadrate femoral muscle. The anterior ridge is feebly developed, but is longer than the other. From the trochanters and their associating ridges the neck of the femur 1 projects upward and inward at an obtuse angle from the shaft. It is cylindrical, compressed from before back- ward, and joins the latter by a strong, expanded base. It supports a spherical head, 2 which is covered with cartilage, and articulates with the acetabulum. On the inner side of the head is a pit for the attachment of the round ligament of the hip joint. The lower extremity of the femur is the most expanded and massive portion of the bone. It terminates in two large eminences, the con'dyles, which are separated behind by a deep notch, the intercon'dyloid fos'sa. 3 The articular surfaces of the condyles are continu- ous in front by a pulley-like surface, the troch'lea, upon which the knee-cap moves. The internal con'dyle is the larger, but the external con'dyle projects most anteriorly. On the remote sides of the condyles is a tuberos'- ity 4 for the attachment of the lateral ligaments of the knee joint. Below the external tuberos- ity is a crescentic fossa, which gives origin to the tendon of the popliteal muscle. When the femur is placed vertically, the in- ternal condyle appears much longer than the external, and the summit of the greater tro- chanter rises nearly as high as the head of the bone. The natural position of the latter is oblique, so that the lower extremities of both thigh bones are brought nearly into contact, and the upper extremities are the most remote from each other. In this position the articulating surfaces of the condyles are on a level, and the summit of the greater trochanter is on the same line with the centre of the head. In the female the neck of the femur is longer and more rectangular FEMUR OF THE RIGHT SIDE, front view. 1, the shaft; 2, head; 3, neck; 4, great trochanter; 5, ante- rior inter-trochanteric ridge; 6, less- er trochanter; 7, external, and 8, internal condyles; 9, tuberosity for the external lateral ligament; 10, groove for the popliteal tendon; 11, tuberosity for the internal lat- eral ligament. 1 Cervix, or collura fernoris. 2 Caput femoris. 3 Fossa intercondyloidea ; f. poplitea. 4 Tuberositas condyli. 150 THE SKELETON. in its relation with the shaft than in the male, so that the thigh bones in the former sex are more oblique or more divergent above. One or two canals, for the principal medullary nutritious vessels, ascend at the inner side of the asperous ridge, in the vicinity of its middle. THE PATELLA. The Patel'la, or knee-cap, 1 viewed by some anatomists as the repre- sentative of the olecranon, by others as a sesa- moid bone of the tendon of the quadriceps ex- tensor muscle, is situated in front of the knee joint. It is a chestnut-shaped bone, with its apex downward and attached by a strong lig- ament to the tibia. Its base is thick, and has inserted into it the tendon of the quadriceps extensor. Its fore part is convex and rough ; PATELLA OF THE RIGHT SIDE, pos- and its back part presents a transversely oval terior view. 1, 2, articular faces articular sur f ace , elevated from each Side into for the trocnlea of the femur; 3, apex of the bone roughened for the a median ridge so as to correspond with the attachment of its ligament. trochlea of the femur, upon which it moves. The patella is composed of a mass of spongy substance enveloped in a thin layer of compact substance. THE BONES OF THE LEG. The bones of the leg consist of the tibia and fibula, placed side by side. The tibia joins the femur above, and, together with the fibula, joins the astragalus below. The former alone receives the pressure of the upper part of the body, and transmits it to the foot ; while the latter appears mainly of importance in extending the surface of the leg for muscular attachment. THE TIBIA. The TiVia, or shin bone, 2 situated at the fore and inner part of the leg* extends in a straight line from the thigh bone to the tarsus, and is the second largest and longest bone of the skeleton. Its shaft is a trilateral prismatic column, with sharp borders, and is most expanded toward the upper extremity. The inner surface, smooth and slightly rounded, is 1 Rotula; epigonis ; caucaloides; su- thyroides, or sesamoideum magnum; pergenualis; acromyle: mylacris; myle; olecranon mobile. mola; gamba; concha; oculus; orbis, 2 Cneme ; procnemium ; focile majus; orscutumgenu; 088cutiforme,disciforme, arundo, or canna major; canna domes- tica cruris. THE SKELETON. 151 FIG. 114. subcutaneous. The outer surface, occupied by muscles, is slightly grooved above, and is rounded below, where it inclines forward. The posterior surface is flat and covered with muscles, and at the upper part is marked by a feeble, oblique ridge, indicating the lower border of attachment of the popliteal muscle. The anterior border, called the crest or shin, 1 is waving in its course, and acute at the middle. The outer border gives attachment to the interosseous membrane ; the pos- terior border, less sharp than the others, gives attachment to muscles. The superior extremity expands into the head, which is the most massive portion of the bone, and appears as if it were pressed backward, so that its front is flattened and it overhangs the posterior sur- face of the shaft. Its prominent lateral por- tions constitute the con'dyles, 2 which have thick porous borders, and support a pair of smooth, oval surfaces, 3 invested with cartilage, for articulation with the condyles of the femur. The inner articular surface is the longer antero- posteriorly, and is slightly concave in this direction ; while the other is slightly convex. Both are elevated at the middle of their ap- proximate border upon a small pyramidal emi- nence, the spi'nous proc'ess, 4 the base of which is the centre of attachment for the semilunar cartilages and crucial ligaments. The articular surfaces are separated by a rough, depressed tract, which crosses the spinous process and expands on the fore and back part of the head. Below the back part of the external condyle is a small, smooth surface, covered with cartilage, for articulation with the head of the fibula. Below the head, in front, at the commence- ment of the crest, is a conspicuous eminence, the tuberos'ity, 5 into which the ligament of the patella is inserted. The lower extremity of the tibia is ex- panded, and at its termination is quadrate. In front it is smooth and convex, and bounded below by a prominent mar- TIBIA AND FIBULA OF THE LEFT LEG. 1, shaft of the tibia; 2, 3, con- dyles; 4, spinous process; 5, tuber- osity ; 6, crest or shin ; 7, lower ex- tremity of the bone ; 8, internal mallcolus; 9, shaft of the fibula: 10, its head ; 11, external mallef >- lua. 1 Crista ; spina. 2 Condyli ; tuberosities. 3 Condyli. 4 Acclivitas, or erninentia condyloidea. or intercondyloidea; spine. 5 Tuberositas tibiae ; tuberculum ; tu- bercle. 152 THE SKELETON. gin for the attachment of the capsular ligament of the ankle joint. Behind, it slopes to an obtuse border, for the same purpose as the latter, and its outer side is excavated and roughened for liganientous attach- ment with the fibula. Its inner part is prolonged into a strong promi- nence, the internal malle'olus or ankle. 1 The inner surface of this process is convex and subcutaneous ; and behind, is marked with a groove for the tendon of the posterior tibial muscle. At the bottom of the tibia is the tar 'sal articular surface, a quadri- lateral concavity, which at its inner side is prolonged downward on the malleolus. It is covered with cartilage, and joins the upper and inner side of the astragalus. The canal of the medullary nutritious vessels is situated at the upper third of the posterior surface of the shaft, and is directed downward. FIG. 115. THE FIBULA. The Fib'ula 2 is a long, slender bone, situated at the outer side of the tibia. Its upper extremity articulates beneath the back part of the head of the latter ; but, in descending, the bone gradually advances in position, so that its lower extremity is nearly as far forward as the internal mal- leolus, and extends rather lower than this. The shaft presents three irregular surfaces separated by prominent borders. The inner surface is divided by an oblique ridge, to which the interosseous membrane is attached. The outer surface is grooved above the middle ; at its upper part inclines forward, and at its lower part inclines backward. The posterior surface is con- vex ; its upper part inclining outward, its lower part in- ward. The upper extremity ex- pands into the head, 3 which is prominent at the sides for the attachment of ligaments and the tendon of the biceps flexor ; and supports at its inner part a small smooth surface for articulation with the external condyle of the tibia. TlBIA AND FIBULA OF THE RIGHT LEG, posterior view. 1, 2, articu- lar surfaces for the condyles of the femur separated by the spinous pro- cess; 3, the inner condyle of the tibia; 4, surface occupied by the popliteal muscle defined by the ob- lique line 5; 6, nutritious foramen ; 7, surface covered by the flexors of the toes; 8, internal malleolus; 9, grooves for tendons ; 10. shaft of the fibula; 11, its head; 12, subcuta- neous surface at the lower part of the bone; 13, external malleolus; 14, groove for tendons, 1 Inner ankle bone. 2 Os perone ; peroneum ; canna, or arundo minor ; sura ; fistula cruris ; cru- ris radius ; focile minus ; tibia minima ; spell, or splinter bone. 3 Capitulum. THE SKELETON. 153 The lower extremity, rather larger than the other, is prolonged, below its junction with the tibia, into the external malle'olus or ankle. 1 This is longer and more prominent than the internal one, and supports a smooth, triangular, articular facet, which joins the outer side of the astragalus and forms part of the ankle joint. Behind the articular sur- face is a fossa for the attachment of the external lateral ligament of the ankle joint, and above it is a convexity, which is conjoined with the tibia by means of a ligament. The fore part of the malleolus is convex and subcutaneous ; and its back part is marked by a groove for the tendons of the peroneal muscles. The canal for the medullary nutritious vessels is situated near the middle of the posterior surface of the shaft, and, like that of the tibia, is directed downward. BONES OF THE FOOT. The bones of the foot are situated at a right angle with those of the leg, and are subdivided into those of the tarsus, of which there are \ seven ; those of the metatarsus, of which there are five ; and those of ) the toes, of which there are sixteen. BONES OF THE TARSUS. The Tarsal bones, 2 or those composing the tarsus, seven in number, consist of the astragalus and calcaneum, the scaphoid, cuboid, and three cuneiform bones. The Astragalus, 3 or ankle bone, is the only one of the tarsus which articulates with those of the leg ; and is the highest and second in size of the former. Its posterior part, or body, is quadrate, and is received between the two malleoli. Its upper articular surface, for the tibia, is antero-posteriorly convex, transversely slightly concave, and is continu- ous at the sides with vertical articular surfaces for the malleoli. Be- neath the body, at its back and outer part, is a concave articular sur- face, which rests on the calcaneum. In advance of the body is the neck terminating in the head, which supports an anterior, convex, articular surface for the scaphoid bone, and an inferior articular surface for the calcaneum. The latter surface and that beneath the body are separated by a deep groove, corresponding with a similar one of the calcaneum, for an interosseous ligament. 1 Outer ankle bone. 3 Talus ; quatrio ; diabebos ; cavicula ; 2 Ossa tarsi; planta prinia ; rascetape- cavilla; tetroros ; astrion ; os balistse ; dis ; pedium ; caviculse pedis nodus. os tesserae ; sling bone ; huckle bone. 154 THE SKELETON. FIG. 116. The Calcan'eum, or heel bone, 1 is the largest one of the tarsus. It is placed beneath the astragalus, extends nearly as far forward, and posteriorly extends far beyond, where it forms the basis of the heel. It is irregularly oblong quadrate. At its upper part in front is a large, irregular fossa, containing two articular surfaces, for the as- tragalus, separated by a rough tract. 2 The larger articular surface is convex, and situated at the back of the fossa ; the other is narrow and concave, and rests on a lateral process 3 internally. In advance of the fossa is a ver- tical articular surface for junction with the cuboid bone. Posteriorly, the calcaneum terminates in a large, convex tuberosity, 4 the lower part of which gives attachment to the "tendon of Achilles." The upper surface of the tuberosity is saddle like, and cor- responds with the depression above each side of the heel. The bottom of the tuberosity bone; 5, 6, 7, internal, middle, and external cuneiform bones ; 8, cuboid bone; 9, metatarsal bones; 10, 11, phalanges of the great toe; 12, 13, 14, phalanges of the other toes. head; 3, calcaneum; 4, scaphoid attachment to the plantar fascia and mus- cles. In advance of the tubercles, the under surface of the bone forms an obtuse ridge. The outer surface of the calcaneum is vertical and rough. Its inner surface forms, with the lateral process, a concavity, 6 which transmits the tendons of the flexor muscles and the plantar vessels and nerves. The Scaph'oid bone, 7 situated at the inner side of the tarsus, is ovoid in outline, with a posterior concave articular surface for the head of the astragalus, and an anterior convex surface, divided into three facets, for junction with the cuneiform bones. Its upper and lower borders are rough ; and its inner part forms a tuberosity for the insertion of the posterior tibial muscle. The Cu/boid bone 8 is situated at the anterior outer part of the tarsus, 1 Os calcis ; calcaneus ; calcar pedis ; calcia ; ichnis ; pternium. 2 Sulcus calcanei. 3 Processus lateralis ; sustentaculum tali ; small apophysis. 4 Tuberositas calcanei ; talus ; calx ; heel. 5 Greater and lesser tuberosity. 6 Sinuosity. 7 Os scaphoides ; os scaphoideum ; os naviculare ; os cymbiforme ; boat-like bone. 8 Os cuboides ; os cubiforme ; os cu- boideum; os cyboides ; oscyrtoides; os grandinosum ; os tesserae ; os varium. THE SKELETON. 155 FIG. 117. and is the third in size of the tarsal bones. Its upper surface inclines outwardly, and is rough. Its under surface, also rough, presents a tu- berosity for the attachment of the calcaneo-cuboid ligament, and, in advance of this, a groove for the transmission of the tendon of the long peroneal muscle. Posteriorly it has a vertical articular facet for the calcaneum; and anteriorly, another, which is subdivided to join the outer two metatarsal bones. Its inner surface is rough, and near the middle has a small articular facet for the internal cuneiform bone. The three Cuneiform bones 1 are situated in a row in front of the sca- phoid bone, with which they articulate. As expressed by the name, they are wedge shaped. The internal cuneiform bone 2 is the largest, and has its base downward; the middle cuneiform bone 3 is the smallest, and it, with the external cuneiform bone, 4 have their base upward. The three bones together contribute to the dorsal convexity of the tarsus, and to its plantar concavity. Anteriorly they articulate with the inner three metatarsal bones, and the external one also articu- lates with the cuboid bone. All the tarsal bones are composed of masses of spongy substance with a com- paratively thin investment of compact substance, which presents many perfora- tions for the transmission of vessels. The tarsus forms one-half of the length of the foot, and is connected near its middle with the leg. Behind the bones of the latter, a small portion of the astragalus and about one-half the length of the calcaneum project, and in front of them project the head of the astragalus, a small portion of the calca- neum, and the five smaller tarsal bones. The portion of the tarsus in front of the ankle joint, or the instep, 5 is convex on its dorsal surface and concave on its plantar surface. On the SOLE OF THE LEFT FOOT. 1, concavity of the calcaneum ; 2, outer face of the same ; 3, groove for the tendon of the long flexor of the toes ; 4, head of the astragalus; 5, scaphoid bone; 6, its tuberosity ; 7,8,9, internal, middle, and external cuneiform bones ; 10, cuboid bone ; 11, its groove for the tendon of the long peroneal muscle ; 12, metatarsal bones ; 13, first row of pha- langes; 14, second row; 15, last row; 16, last phalanx of the great toe. 1 Ossa cuneiformia ; ossa, or ossicula chalcoidea. 2 Os cuneiforme internum, primum, or magnum. 3 Os cuneiforme medium, secundum, or minus. 4 Os cuneiforme externum, or tertium. 5 Collum pedis ; neck of the foot. 156 THE SKELETON. outer part of the tarsus, between the astragalus and calcaneum, is a large space or sinus, 1 which narrows into a canal, proceeding obliquely inward and backward to the inner side of the tarsus. Both sinus and canal are occupied by interosseous ligaments connecting the astragalus and cal- caneum. Back of the astragalus a groove is observable, leading toward another beneath the lateral process of the calcaneum, both of which accommodate the tendon of the long flexor of the great toe. The articulation of the astragalus and calcaneum with the other bones of the tarsus is so nearly in a direct line, that it affords a convenient position for disarticulation, when necessary, from injuries of the foot. BONES OF THE METATARSUS. The Metatar'sal bones, 2 or those composing the metatarsus, 3 corre- spond in number with the toes, which they join in front. They are enumerated from within outward, have the same general construction as the metacarpal bones, and are slightly bent in their length so as to con- tribute to the concavity of the sole of the foot. The shaft is trilateral ; one surface presenting downward, another out- ward, and the third inward and upward. The shaft of the outer four bones gradually narrows to its head ; that of the great toe is more uni- form in diameter. The posterior extremity, or base, is the most expanded part, is quad- rate, and varies in form with the different bones. The base of the first, at its lower part, has a tubercle for the insertion of the long peroneal tendon ; the bases of the succeeding three are wedge shaped, and by their lateral adaptation contribute to the convexity of the back and the concavity of the sole of the foot. The base of the last metatarsal is prolonged outward and backward into a tuberosity for the insertion of the short peroneal tendon. The bases of the outer four metatarsals ar- ticulate with one another by opposed smooth surfaces : those of the inner three metatarsals articulate with the cuneiform bones ; and those of the outer two with the cuboid bone. The anterior extremity, or head, is constructed like the correspond- ing part of the metacarpal bones, but is smaller, in proportion with the length of the bones, except in the case of that of the great toe. The first metatarsal bone is the shortest, but is twice as robust as the others ; the second and fifth metatarsals are the longest, and are nearly equal ; the third and fourth are next in length, and are also nearly equal. All the metatarsals lie parallel to one another, and they contribute in 1 Sinus tarsi. 2 Ossa metatarsi. 3 Metatarsium; metapedium ; prsecordium, solum, or vestigium pedis. THE SKELETON. 157 their union to the convexity of the back and the concavity of the sole of the foot. The interos'seous spaces are enumerated from within out- ward. BONES OF THE TOES. The Toes 1 are enumerated from within outward, as the first or great toe, 2 the second, third, fourth, and fifth or little toe. They diminish in length from first to last, and possess the same number of bones as the fingers. The phalanges, 3 or joints, of the toes have the same general form as those of the fingers, but are smaller, except those of the great toe, which are as long and of more robust proportions than those of the thumb. In the first row of phalanges, except in the great toe, the shaft resem- bles that of the corresponding bones of the fingers, but compressed later- ally so as to assume a more cylindroid form. In the second and third rows of phalanges of the outer two or three toes, the characteristic extremities are so nearly approached that the shaft is more or less obsolete. The second and third phalanges of the little toe are frequently co-ossified. The two ses'amoid bones of the great toe are like those of the thumb, and occupy a corresponding position in the sole of the foot. THE FOOT. The Foot is placed at a right angle with the leg, and rests upon the ground with the tuberosity of the calcaneum, the heads of the metatarsal bones, and the under parts of the phalanges. The heel pro- jects behind the leg at the outer part of the foot, of which it is the nar- rowest portion. From the fore part of the tarsus, or the instep, the foot in advance gradually expands in breadth and becomes thinner. The upper or dorsal surface, or back of the foot, is convex in its length and breadth ; and the under or plantar surface, or sole, in the same direction is concave. The arch formed by the foot is higher and more open on the inner side. When covered with soft parts, the heel, outer border of the foot, and the under part of the toes touch the ground ; the inner archway constituting the hollow of the foot. The feet of the two sides diverge from each other in front, in consequence of the rotary muscles of the thigh directing the limbs outwardly. The hinge-like joint of the ankle 1 Digiti pedis. 2 p Uex pedis ; hallux, or hallus. 3 Ossa, articuli, or internodia digitorum pedis. 158 THE SKELETON. allows flexion and extension of the foot. In the former movement the foot is bent forward ; in the latter the back of the foot approaches the same line as the front of the leg. The movement of the foot directing its sole inward and in a feebler degree outward, occurs between the astra- galus and the tarsal bones with which it articulates. The bones of the tarsus and metatarsus together exhibit but very little movement among themselves, with the exception just mentioned. The toes present a greater degree of extension upon the metatarsus than the fingers on the metacarpus, but their power of flexion is much more limited, and that of abduction and adduction are feeble. The phalanges of the toes have the same movements among themselves as those of the fingers, but are restricted from their comparatively feeble development. A continuance of extension of the toes flexes the foot ; the reverse action of the toes extends the foot. When the toes are covered with their soft parts, the second appears a little longer than the first, a feature which has not escaped the attention of artists, but the great toe of the skeleton is actually the longer. DEVELOPMENT OF THE BONES OF THE LOWER EXTREMITY. The femur begins to ossify about the middle of the second month of embryonic life, being earlier than the vertebral column. At birth its shaft is formed, and an ossific centre has appeared in the lower extremity as an epiphysis. Subsequently the head, the greater and the smaller trochanter successively ossify as epiphyses. The patella is formed from a single centre of ossification, appearing several years after birth. The shaft of the tibia commences ossification about the same time as that of the femur, and the shaft of the fibula begins the process a little later. In both bones, after birth, the extremities ossify as epiphyses. The astragalus and calcaneum begin to ossify before birth ; the other tarsal bones subsequently. An epiphysis is developed upon the tuber- osity of the calcaneum. The metatarsal and phalangial bones are ossi- fied in the same manner as the corresponding bones of the hand. ARTICULATIONS AND MOVEMENTS OF THE LOWER EXTREMITIES. The support of the trunk of the body requires that the articulations of the lower extremities should be more extensive, and stronger than those of the upper extremities, a condition which has been gained at the expense of comparative freedom in movement. The hip bones, THE SKELETON. 159 described as part of the trunk, but which correspond with the bones of the shoulder, are entirely immovable. FIG. 118. THE HIP JOINT. The Hip joint, 1 formed between the acetabulum and the head of the thigh bone, is the strongest articulation of the body, and the best instance of a ball-and-socket joint. Though admitting of movement in every direction, it is nevertheless much restricted in this respect in comparison with the shoulder joint. The acetabulum is deepened by a prismatic fibro-cartilaginous ring, the eot'yloid lig'ament, 2 at- tached around its margin. As the ligament passes over the cotyloid notch, this is converted into a foramen, which transmits articular ves- sels into the joint. From the pit on the head of the femur, a strong fibrous cord, the round lig'ament, 3 diverges inwardly to be at- tached to the margins of the cotyloid notch. The cap'sular lig'ament 4 of the hip joint is the strong- est one of the body. It is attached by its upper extrem- ity around the border Of the iliac ligament; 2, the greater sacro-sciatic ligament; 3, the acetabulum, inclosing the CO- lesser 8 ^ro-sciatic ligament; 4, the greater sacro-sciatic fora- f men; 5, the lesser sacro-sciatic ligament; 6, the cotyloid liga- tyloid ligament; aild by its ment surrounding the acetabulum; 7, the round ligament ; 8, lower extremitV is attached attacnmen t of the capsular ligament of the hip joint to the neck of the femur ; 9, obturator membrane. to the anterior mter-trocnan- teric ridge of the femur, and less strongly to the neck of the latter just above the posterior inter-trochanteric ridge. In front of the joint it is strengthened by a broad fibrous band, the accessory lig'ament, 5 which is extended between the anterior inferior spinous process of the ilium and the anterior inter-trochanteric ridge. The capsular ligament is surrounded portion of the pogterior gacr(> 1 Coxo- or ilio-femoral articulation. 2 Labrum cartilagineum. 3 Lig. teres ; interarticular ligament. 4 Membrana capsularis femoris. 6 Superior ligament; ilio-femoral liga- ment. 160 THE SKELETON. with large muscles, which contribute to the strength of the joint. Intern- ally it is lined with synovial membrane, which also invests the neck of the femur, and is reflected upon the round ligament. Even when all the muscles, together with the capsular ligament sur- rounding the hip joint, are cut away, it requires considerable force to remove the head of the femur from its socket, in consequence of the pressure of the atmosphere retaining it in position. FIG. 119. THE KNEE JOINT. The Knee joint is the largest and most complex of the articulations. It is hinge like and slightly rotary in its movements. It allows the leg to be almost doubled in flexion on the back of the thigh, but permits its exten- sion only to a straight line with the latter. When the leg is flexed the articulation of the knee permits it to rotate moderately on its axis from side to side, but not when in the extended condition. The condyles of the femur and tibia, with a pair of interposed fibro-cartilages, and the patella, form the basis of the joint; the contiguous surfaces of the bones being invested with cartilage. It is enveloped in a thin capsular ligament lined with an extensive synovial mem- brane, and is strengthened by strong cord- like ligaments and the contiguous ten- dons of muscles. Upon the condyles of the tibia rest the semilu'nar fi'bro-cartilages, 1 a pair of prismoid, C-like plates, with their ex- tremities attached in front and back of the spinous process. 2 Their exterior border is thick, and they slope off to a thin interior edge, by which arrangement they deepen the shallow ar- ticular surfaces of the tibia into suitable concavities for the play of the THE RIGHT KNEE JOINT, laid open from the front. 1, articular surface of the fe- mur; 2, 3, crucial ligaments; 4, inser- tion of one of these ligaments into the tibia; 5, attachment of the alar folds of the synovial membrane to the femur ; 6, 7, internal and external sernilunar fibro- cartilages; 8, ligament of the patella turned down, so as to exhibit the syno- vial bursa (9) beneath; 10, superior ti- bio-fibular articulation ; 11, interosseous membrane. 1 Fibro-cartilagines, or cartilagines semilunares, interarticulares, falcatse, lunatae, meniscoideae, or sigraoideae. 2 The attachments of these fibro-carti- lages constitute the ligamenta cartilagi- num serailunatarum. A connection of the two in front, the lig. transversum. THE SKELETON. 161 FIG. 120. condyles of the femur. The inner fibro-cartilage is adherent by its cir- cumference to the capsular and lateral ligaments ; the outer one is not so much adherent, and therefore glides more freely to and fro with the move- ments of the femur. Besides adapting the condyles of the tibia to those of the femur, the semilunar nbro-cartilages protect the condyles from attrition, act as elastic cushions to reduce the force of concussions, and prevent the atmosphere from pressing the capsular ligament between, the bones. From the sides of the intercondyloid fossa of the femur a pair of strong, fibrous cords, the cru/cial lig'a- ments, 1 cross each other and descend to be attached in front and behind the spinous process of the tibia. These ligaments re- strict the flexion and extension of the leg, and give firmness to the joint, especially when the limb is flexed. The cap'sular lig'ament 2 is a thin, capa- cious envelope, attached to the rough borders of the condyles of the femur and tibia, and the sides of the patella, and associated with the tendons of the various muscles attached in the vicinity of the articulation. It is so thin as to appear to be a mere continuation of the periosteum of the contiguous bones strengthened at particular points with pro- cesses from neighboring tendons. A pro- cess 3 of this kind, at the back of the joint, is derived from the tendon of the semi-mem- branous muscle, and is extended between the external condyle of the femur and the internal condyle of the tibia. Above the patella, the tendon of the quadriceps extensor occupies position and function of a strong ligament to the knee joint; below is the lig'ament of the patella, 4 a broad, thick, fibrous band, which is an extension of the tendon of the muscle just mentioned descending from the apex and front of the patella to the tuberosity of the tibia. Just above its insertion the ligament is separated from the head of the tibia by a synovial bursa, not communicating with the knee joint. FRONT VIEW OF THE RIGHT KNEE JOINT. 1, tendon of the quadriceps extensor muscle ; 2, patella ; 3, liga- ment of the patella, or tendinous in- sertion of the muscle just mentioned ; 4, capsular ligament; 5, 6, internal and external lateral ligaments; 7, superior tibio-fibular articulation. 1 L. cruciata. 2 Membrane capsularis genu. 3 Lig. posticum Winslowii ; 1. popli- teum ; posterior ligament. 4 Lig. patellae. 11 162 THE SKELETON. FIG. 121. The internal lateral ligament 1 of the knee joint is a long, broad, and strong band, extended between the tuberosity of the internal condyle of the femur and the upper part of the inner border of the tibia. The external lateral ligament 2 is a rounded cord, extended between the tuberosity of the external con- dyle of the femur and the head of the fibula. These ligaments sus- tain the firmness of the articulation, more especially in the extended con- dition of the leg. The synovial membrane of the knee joint lines the capsular liga- ment, and is reflected upon the semilunar nbro-cartilages and cru- cial ligaments. It is also reflected upon a mass of fat intervening be- tween the ligament of the patella and the front of the head of the tibia, and is extended along the sides of the joint as two crescentic appendages named the a'lar folds. 3 These unite and are prolonged in a conical, cord-like process, 4 ascending obliquely backward, to be .attached to the front margin of the intercondyloid fossa of the femur. Above the patella and its trochlea the synovial membrane is reflected as a pouch for several inches upward, between the tendon of the quadriceps extensor and the femur. In the flexion of the leg this pouch is drawn down to the edge of the trochlea of the femur ; and in extension is again drawn up by fleshy slips 5 of the quadriceps muscle. Behind the joint, the synovial membrane extends upward between the condyles of the femur and the tendinous heads of the origin of the gastrocnemius muscle. LONGITUDINAL SECTION OF THE LEFT KNEE JOINT. 1, femur; 2, tendon of the quadriceps extensor muscle; 3, patella; 4, ligament of the patella; 5, tibia ; 6, synovial bursa ; 7, cushion of fat occupy- ing the angular interval between the patella and head of the tibia; ****** reflections of the synovial membrane ; 8, pouch of this mem- brane extending upward between the tendon of the quadriceps extensor and the front of the femur ; 9, the outer alar fold of the synovial membrane; 10, connection of the alar folds with the femur; 11, crucial ligament; 12, back of the capsular liga- ment. 1 L. laterale internum. 2 L. laterale externum. 3 Ligamenta alaria ; 1. alare majus in- ternum et minus externum. 4 Mucus ligament; ligamentum mu- cosum. 5 Musculi subcrurales ; m. articulares genu. THE SKELETON. 163 FIG. 122. THE TIBIO-FIBULAR ARTICULATIONS. The fibula articulates immovably with the tibia. "he superior tib'io-fib'ular articulation, 1 between the head of the >r and the outer condyle of the kfct- er, has the opposed surfaces covered with cartilage. It is inclosed in a capsular liga- ment, the stronger portions of which consti- tute the anterior and posterior ligaments. The wide interval between the two bones of the leg is occupied by an interos'seous membrane, 2 composed of parallel fibres de- scending obliquely from the outer border of the tibia to the opposed border of the fibula. The membrane is perforated above for the passage of the anterior tibial vessels. It gradually narrows below, and between the inferior extremities of the bones consists of short, strong fibres 3 firmly connecting them together. The inferior tib'io-fib'ular articulation is strengthened by the anterior ligament, 4 which is an oblique band extending from the front of the tibia downward to the ex- ternal malleolus; and the posterior ligament, 5 which consists of two bands pursuing the same course behind the bones. POSTERIOR VIEW OF THE INFERIOR TIBIO-FIBULAR AND ANKLE JOINTS. 1, interosseous membrane; 2, 3, two fasciculi of the posterior tibio-fibular ligament; 4, iuternal lateral liga- ment of the ankle joint ; 5, 6, poste- rior and outer fasciculi of the exter- nal lateral ligament; 7, capsular ligament of the ankle joint; 8, cal- caueum. THE ANKLE JOINT. The Ankle joint 6 is formed by the transverse arch between the malleoli and the body of the astragalus. It is a simple hinge-like articulation, permitting flexion and extension. The joint is surrounded by a thin cap'sular lig'ament, connecting the contiguous borders of the articular surfaces of the bones, strengthened by lateral ligaments. 1 Pereneo-tibial articulation. 2 Membrana interossea ; septum longi- tudinale interosseum. 3 Inferior interosseous ligament. 4 L. tibio-fibulare anticum superius et inferius; 1. malleoli interni anticum. 5 L. tibio-fibulare posticum superius et inferius; the posterior and transverse ligaments ; 1. malleoli interni anticum. 6 Articulatio pedis ; articulatio talo- cruralis. 164 THE SKELETON. The external lateral ligament 1 consists of three strong fibrous bands diverging from the outer malleolus; one proceeding backward to the posterior border of the astragalus, a second descending to the outer part of the calcaneum, and the third passing forward to the anterior border of the astragalus. FIG. 123. FIG. 124. EXTERNAL VIEW OF THE RIGHT ANKLE JOINT. 1, INTERNAL VIEW OF THE ANKLE JOINT. 1, internal tibia; 2, external malleolus of the fibula ; 3, astra- malleolus of the tibia; 2, astragalus; 3, calca- galus ; 4, calcaneum ; 5, cuboid bone ; 6, 7, 8, three neum ; 4, scaphoid bone ; 5, internal cuneiform fasciculi of the external lateral ligament; 9, front bone; 6, internal lateral ligament; 7, capsular lig- of the capsular ligament. ament ; 8, Achilles' tendon. The internal lateral ligament 2 is a strong band diverging from the lower border of the inner malleolus to the corresponding side of the astragalus and the lateral process of the calcaneum. THE INTERTARSAL AND TARSO-METATARSAL ARTICULA- TIONS. ARTICULATIONS OP THE ASTRAGALUS, CALCANEUM, AND SCAPHOID BONE. The astragalus and calcaneum are conjoined by a thick interos'seous lig'ament, occupying the sinus formed by the contiguous grooves of those bones. The ligament separates two joints, of which the poste- rior is surrounded by a short, thin cap'sular lig'ament, lined with a synovial membrane. The other joint is continuous inferiorly with that between the head of the astragalus and the scaphoid bone ; both being enveloped in a common cap'sular lig'ament, and lined with a continuous synovial membrane. This articulation is strength- ened above by a broad fibrous band, the astrag'alo-scaph'oid lig'a- 1 L. laterale externum ; 1. fibulare tali posticum et anticum et 1. fibulare calca- nei; 1. malleoli extern! posticum, medium, et auticum ; 1. fibulae posticum, medium, et anticum. 2 L. laterale internum ; 1. deltoides ; 1. tibio-tarsium. THE SKELETON. 165 ment i 1 at its outer side by the external calcan'eo-scaph'oid ligament, 2 connecting the corresponding bones in the interval between the astraga- lus and cuboid bone. Below the articulation is the inferior calcan'eo- scaph'oid ligament, 3 which is a strong, broad band proceeding from the lateral process of the calcaneum, beneath the head of the astragalus, to the scaphoid bone. ARTICULATION OF THE CALCANEUM AND CUBOID BONE. The intervening articulation of the calcaneum and cuboid bone is sur- rounded by a short cap'sular lig'ament, strengthened above and below by a broad band of fibres constituting the superior and inferior calcan'- eo-cu/boid lig'ament. 4 LIGAMENTS OF THE SOLE OF THE FOOT. 1, calcaneum; 2, astraga- lus; 3, scaphoid bone ; 4, long plantar ligament; 5, inferior cal- caneo-cuboid ligament; 6, inferior calcanec-scaphoid ligament; 7, plantar ligaments between the cuneiform bones and base of the metatarsus ; 8, tendon of the long peroneal muscle passing through a groove of the cuboid bone above the long plantar ligament to be inserted into the first meta- tarsal bone; 9, capsular ligament between the latter and the inter- nal cuneiform bone; 10, plantar ligaments, having the same rela- tionship with the metatarso-pha- langial and phalangial articula- tions that the palmar ligaments have with the corresponding joints of the fingers ; 11, lateral ligaments; 12, transverse liga- ments; 13, lateral ligaments of the phalangial articulations. FIG. 125. ARTICULATION OF THE SCAPHOID, CUBOID, AND CUNEIFORM BONES TOGETHER AND WITH THE BASES OF THE META- TARSAL BONES. All the bones here mentioned, with the exception of the first metatar- sal, are joined with one an- other, on the back and sole of the foot, by fibrous bands associating those contiguous, and constituting the dor'sal and plan'tar lig'aments, 5 which together form a sort of capsular ligament. Interos'seous lig'aments, 6 consisting of short interven- ing fibres, conjoin the scaph- oid with the cuboid bone, the latter with the external cunei- form bone, the three cunei- form bones with one another, and the bases of the outer four metatarsal bones. The synovial membrane of the articulation of the scaphoid and cuneiform bones is prolonged to that 1 L. astragalo-scaphoideum. 2 L. calcaneo-scaphoideum externum, interosseum, or dorsale ; 1. calcaneo- naviculare interosseum. 3 L. calcaneo-scaphoideum inferius ; 1. calcaneo-naviculare plantare. 4 L. calcaneo-cuboideum superius et inferius, or dorsale et plantare, or breve. 5 L. dorsalia et plantaria. 6 L. interossea. 166 THE SKELETON. of the cuboid and external cuneiform bone, and also to the articulation between the outer two cuneiform and the second and third metatarsal bones. Another synovial membrane lines the joint of the cuboid and outer pair of metatarsal bones. The first metatarsal bone and internal cuneiform bone form a separate joint surrounded by a capsular ligament with a distinct synovial mem- brane. The Long Plan'tar lig'ament, 1 the most conspicuous of the ligaments of the foot, commences on the under surface of the calcaneum, and proceeds forward, gradually expanding, to be attached to the tuberosity of the cuboid bone and the bases of the last two metatarsal bones. It converts the groove of the cuboid bone into a canal, through which passes the tendon of the long peroneal muscle. METATARSO-PHALANGIAL AND PHALANGIAL ARTICULA- TIONS. The metatar'so-phalan'gial and phalan'gial articulations are con- structed exactly like the corresponding joints of the hand. 1 L. longum-plantae ; 1. calcaneo-cuboideum plantare ; inferior or long calcaneo- cuboid ligament. CHAPTER III. THE FIBROUS, CARTILAGINOUS, FIBRO-CARTILAG1NOUS, ELASTIC, AND ADIPOSE TISSUES. IN describing the articulations of the skeleton, many structures were mentioned, which enter into their composition, in addition to the bones. As these structures likewise enter into the constitution of many other parts of the body, it has appeared to us convenient to defer an examination of their nature until the present moment. Those to which we espe- cially refer are the fibrous, cartilaginous, fibro-cartilaginous, and elastic tissues. To these we might add the serous, adipose, and muscular tissues, but an account of the former and latter will be deferred to other oppor- tunities ; while the adipose tissue, which appears to be unessential to the constitution of any organ, may be conveniently described in the present chapter. FIBROUS TISSUE. Fi'brous tis'sue 1 is one of the most abundant and extensively diffused materials of structure of the body. It mainly composes the dermis or true skin; the superficial and deep fascia; the periosteum and perichon- drium ; nearly all the ligaments ; the sheaths of blood-vessels and nerves ; the tendons, aponeuroses, and sheaths of muscles ; the dura mater, sclero- tica, and the outer layer of the pericardium ; the capsules of the spleen, kidneys, testes and ovaries ; the submucous, subserous, and subglandular tissues ; and the general connective or areolar tissue of most organs of the body. Fibrous tissue is white, bluish white, or yellowish white, and more or less glistening. When dried it becomes hard, yellow, and transparent ; but assumes its former appearance on the imbibition of water. It is the strongest and most tenacious of all animal tissues, is very inex- tensible, but highly flexible. From these physical properties it is admi- rably adapted to the various purposes for which it is employed in the 1 White fibrous tissue. (167) 168 THE TISSUES. body, viz., the protection, sustaining, and connection of other tissues and organs. FIG. 127. FIG. 126. EXAMPLE OF FIBROCS TISSUE. Portion of one of the lateral ligaments of a phalangial articulation, exhibiting its composition of bundles of parallel filaments of fibrous tissue ; highly magnified. EXAMPLES OF FIBROUS TISSUE. 1, a small tendin- ous cord from the right ventricle of the heart. The upper extremity exhibits its division and expan- sion into the edge of the tricuspid valve. 2, a por- tion of the dura mater of the spinal cord. The great strength, tenacity, and durability of fibrous tissue have ren- dered it of important service in the arts. The so-called "cat-gut," fiddle strings, and the like, are the twisted fibrous structure of the small intes- tine of the sheep. All varieties of leather consist of the fibrous derm of the skins of animals, rendered less liable to the ordinary causes of decay by union with certain chemical substances, such as tannin. Parch- ment is likewise derived from the same source ; and the savage finds it invaluable as a bow-string. By boiling fibrous tissue it is resolved into gelatin ; and hence frag- ments of skin, tendons, and ligaments are the chief source of the glue of commerce. Fibrous tissue is mainly composed of exceedingly fine homogeneous filaments, measuring from the 3^3 to tne TDUOTJ f an i ncn * n diameter, collected into minute inextensible bundles, which may be associated into larger bundles, as in the formation of tendons and ligaments, or they may interlace with one another into more or less extensible membranes. The intervals of the bundles of filaments of fibrous tissue are occupied by a colorless homogeneous liquid resembling serum, but its exact nature has not been positively determined. THE TISSUES. 169 FIG. 128. All structures of fibrous tissue contain more or less intermingled elastic tissue in the char- acter of slender fusiform fibres, or as fine net- works. The elastic tis- sue is rendered evident, on treating portions of any of the fibrous struc- tures with acetic acid, beneath the microscope. By this process the fibrous tissue is ren- dered so transparent as to appear indistinct, while the fibres of the elastic tissue become sharply defined. In the formation of tendons, the primary bundles of fibrous tissue are closely associated parallel to one another, thus producing strong inexten- sible cords, admirably adapted to convey the muscular power to the bone or other part to be moved. Likewise in the construction of the band-like ligaments, intended to unite the bones in the strongest manner, the fibrous tissue is col- lected into parallel bundles, per- mitting free flexibility, but no stretching or extensibility. In the constitution of aponeu- roses, the deep fascia, and the dura mater, bundles of fibrous tis- sue are arranged parallel to one another in layers, and crossed by bundles which closely associate the former together. In most other fibrous structures, the filaments and bundles of fibrous tissue interlace with one another in such a manner as to permit of more or less extensibility. 1, PORTION OF CONNECTIVE TISSUE, from that which envelops the flexor tendons of the fingers as they pass beneath the annular ligament, treated with acetic acid. The pale, dotted portion is in- tended to represent the fibrous element fading away ; the blacker tortuous lines and nets represent the mixture of elastic tissue. 2, 3, simple tortuous fibres, and a net of elastic tissue, isolated from the preceding specimen. FIG. 129. FIBROUS TISSUE. 1, portion of tendon exhibiting its composition of prismatic bundles of fibrous tis- sue, the filaments all parallel to one another ; 2, a few bundles drawn from the others, exhibiting their union by delicate crossing filaments of con- nective tissue, (3) one of the varieties of fibrous tis- sue; 4, a single bundle, more highly magnified, with a portion (5) of the filaments fretted out. This property 170 THE TISSUES. is, however, entirely dependent on the arrangement alone of the fibrous tissue, as it is in all cases entirely inextensible in the direction of its fila- ments. The fact may be easily understood by referring to a familiar illustration : thus, while a handkerchief or other similar fabric is inexten- sible in the direction of its threads, it is quite extensible and contractile diagonally to the course of those threads, or in the bias direction, as it is usually termed. Simply by the arrangement then of the filaments of fibrous tissue, we find in the body structures composed of it exhibiting every degree of softness and extensibility, from the delicate, cottony connective tissue, to the unyielding tendon. Connective or are'olar tis'sue, 1 found almost everywhere in the body in the form of a moist, tough, white, downy substance, is composed of FIG. 130. FIG. 131. PORTION OF CONNECTIVE TISSUE, from the axilla, exhibiting its composition of bundles and filaments of fibrous tissue crossing in every direction. The rounded bodies represent a single row and a por- tion of a small group of fat cells. CROSSING BANDS OF FIBROUS TISSUE, from the ex- ternal, or fibrous coat of the facial artery. Inter- vals are left in the drawing to exhibit clearly that there are two layers of fibrous tissuo, of which the filaments cross one another in their spiral course around the vessels. interlacing bundles of fibrous tissue, and of all materials is the best adapted, from its combined strength, softness, and yielding character, to connect, sustain, and strengthen organs, while it permits a certain degree of mobility among them. Thus it tenaciously holds together the vessels, 1 Cellular tissue ; tela cellulosa, or cellularis; reticulated, filamentous, laminated, or porous tissue ; cellular, or reticular substance ; context us cellulosus ; ethmyphe, tela Hippocratis cribrosa. THE TISSUES. 171 nerves, muscles, bones, and skin, fills up intervals and forms soft beds of support for them, and yet allows them moderate freedom of movement. In like manner it holds together the muscular fibres, the nerve fibres, and the constituents of other tissues, and gives them strength without incon- veniently impeding their movements. Comprising as it does the submu- cous and subserous layers of the hollow viscera, while these derive from it their main strength, it yet permits their expansion. In the sheath of blood-vessels and muscular fasciculi, the filaments of fibrous tissue cross one another diagonally to the course of the former in a most beautiful manner, and while they give strength they allow movement in all directions. While the band-like ligaments, com- posed of parallel bundles of fibrous tissue, firmly unite the bones and are simply flexible, the capsular ligaments, composed of interlacing bundles of the same material, are moderately extensible. The tendon, composed of closely parallel bundles of fibrous tissue, does not stretch, but follows the contraction of the muscle whose swelling form is observed through the more yielding fasciae and skin. The fibrous tissues are furnished with comparatively few and small blood-vessels ; the large arteries and veins frequently observed in them, as for instance in the submucous tissues and the dura mater, being des- tined to supply the contiguous structures. The nerves are also few, and hence the sensibility of these tissues is of the feeblest character. The dermis would appear to be an exception in comparison with other fibrous structures, but the vessels and nerves in this case are rather intended for the functions of various accessory parts, as for example the papilla of touch and of the hairs, the glands, and the epidermis. Fibrous tissue, of all others, appears to be the most easily reproduced in cases where it has been destroyed. It forms the structural element of most cicatrices, false membranes, adhesions, etc. CARTILAGE AND FIBRO-CAETILAGE. Car'tilage or gristle 1 is a dense substance, of less hardness than bone, of a bluish-white or yellow color, with an opalescent or pearly appear- ance. It is elastic, flexible but inextensible, and, though of firm consist- ence, is less tough than fibrous tissue. Easily cut or sliced with the knife, in thin pieces it is translucent j*ttird to the naked eye appears homogeneous in structure. By drying it becomes very hard, yellow, and 1 Cartilage ; chondros. 172 THE TISSUES. FIG. 132. CARTILAGE; section through the thickness of the oval cartilage of the nose. 1, toward the exterior ; 2, toward the interior surface ; highly magnified. It exhibits groups of cartilage cells imbedded in a homogeneous or faintly granular matrix. transparent, but readily assumes its former condition through the imbibi- tion of water. From its physical properties cartilage is admirably adapted to con- tribute to the formation of the joints of the skeleton, and to give form and strength to other organs, with- out too great a degree of rigidity. It constitutes the articular carti- lages, the cartilages of the ribs, those of the larynx, except the epi- glottis, those of the trachea and its divisions, and those of the nose. In association with fibrous tissue it forms the fibro-cartilages, as the intervertebral disks, the fibro-car- tilages of the symphyses, the inter- articular fibro-cartilages, the epi- glottis, the cartilages of the ear and Eustachian tube, and those of the eyelids. The bones originate, for the most part, in the condition of cartilage, and to a much less degree in the form of fibrous tissue ; and their subse- quent development and growth are step by step preceded by a produc- tion of the latter tissues. The cartilages which ossify and form part of the skeleton are commonly termed temporary cartilages ; although the others, named in contradistinction permanent car'tilages, in many cases at a later period of life become ossified, or show more or less disposition to do so. Thus the cartilages of the larynx may become completely ossified, and the costal cartilages are liable to partial ossification. The articular cartilages, the cartilages of the nose, and the fibro-cartilages exhibit no tendency to ossification, at least under ordinary circum- stances. In structure, cartilage consists of a solid matrix with imbedded nucleated cells. The matrix is colorless and translucent, or resembles in appearance ground glass, or it is faintly amber colored. It is amorphous, indis- tinctly granular, or obscurely filamentous, passing into a distinctly fib- rous condition. The nucleated cells may be single, but are usually in compressed, elongated oval groups, which seem as if they had origin- ated through the division of simple cells, as they are seen in the earliest condition of cartilage. In the deeper part of the articular cartilages, and the more interior part of the others, the groups of cells are ar- ranged vertically to the direction of the free surfaces ; but, approaching the latter, they become more numerous and parallel to them. The car- THE TISSUES. 173 tilage cells are observable from single ones up to groups of twenty or more. They have more or less thickened walls, with faintly granular contents, usually a nucleus, and frequently one or more oil globules. FIG. 134. FIG. 133. VERTICAL SECTION OP ARTICULAR CARTILAGE, from the carpal surface of the radius. 1, 2.^3, articular cartilage; below this is a portion of the hone, 5, 6, 7. 1, exterior portion of the cartilage, exhibiting the groups of cells lying parallel to the slightly irregular free surface ; 2, 3, the cells arranged ver- tically in the deeper part of the cartilage ; 4, groups of cells obscured by osseous deposits ; 5, structure of the bone, exhibiting the concentric laminae, and lacuna?; 6, a vascular canal; 7, a marrow areola of the spongy substance of the bone. The specimen is highly magnified, but the depth of the articular cartilage is proportionately reduced, so as to ex- hibit the relation of all the parts without making too large a figure. SECTION OF COSTAL CAHTILAGE. The upper part is toward the exterior surface, where the groups of cells are arranged parallel to it; the lower part is toward the interior, where the groups are ar- ranged vertically to the free surfaces ; highly mag- nified. Fi'bro-car'tilage consists of a more or less dense fibrous matrix, with imbedded cartilage cells. Be- tween pure fibrous tissue and pure cartilage we may distinguish very various degrees of intermixture of the two elements in the constitution of the fibro-cartilages. Thus the cartilages of the eyelids, and the semilunar and other interarticular carti- lages, are almost entirely composed of fibrous tissue. This is likewise the case with the exterior of the intervertebral disks, but the more pulp-like central portion contains numerous mingled cartilage cells. In the cartilages of the ear and the epiglottis a more equal admixture of the two elements is observable, groups of cells being contained in the meshes of an intricate intertexture of fibres. Even in the costal carti- lages, classed with the pure cartilages, portions of the interior not un- frequently present a decidedly fibrous matrix, including the cell groups. 174 THE TISSUES. Fibro-cartilages combine the elasticity of cartilage with the tenacity of fibrous tissue, and are well adapted for the firmest union of bones, accompanied with a moderate degree of flexibility. FIG. 135. FIG. 136. SECTION OF COSTAL CARTILAGE, crossing the free surfaces, but tiiken from near the centre. To the left, which was toward the exterior surface, the groups are imbedded in a homogeneous matrix; toward the right, the matrix has assumed a decidedly fibrous character. Specimen from an adult of about forty years of age. By long boiling cartilage is resolved into chondrin, a substance resem- bling gelatin, but, unlike it, is precipitable by the mineral acids. The mine- ral salts of cartilage are like those of bone, and amount to about three and a half parts in the hundred. Fibro-cartilage by boiling is re- solvable, into gelatin. The articular cartilages consist of thin layers covering the artic- ular surfaces of bones in the con- struction of movable joints. They are entirely non-vascular, and de- void of nerves; but they derive nourishment from the blood-vessels in contact with their surface beneath or continuous with the bones. The other cartilages are invested with a fibrous membrane, named the peri- chon/drium, which serves as a means of attachment with contiguous parts, and as a nidus to the blood-vessels nourishing the cartilages. The comparatively thick costal cartilages are pervaded with vascular canals, continuous with those of the ribs, and contain nutrient vessels com- municating with those of the latter and of the perichondrium. Fibre- cartilages receive more vessels than the true cartilages, but the num- ber of them is very small. SECTION OF FIBRO-CARTILAGE FROM THE AURICLE OF THE EAR. The cells are seen imbedded in a fibrous matrix. 1, exterior surface, where the cells are parallel to it ; 2, toward the middle. Highly magnified. THE TISSUES. 175 FIG. 137. ELASTIC TISSUE. The Elas'tic tissue, 1 though widely distributed in the body, seldom forms masses of any important size. It composes the yellow ligaments of the ver- tebral arches ; is the chief component of the thyro-hyoid ligament, the vocal membrane, and the structure conjoining the rings of the trachea and bronchia ; and it enters largely, in association with muscular tissue, in the formation of the middle coat of the blood-vessels. In small quan- tity it is found mingled with most of the fibrous structures, as the der- mis, the superficial fasciae, etc. In its most striking condition of development it is observed composing the nuchal ligament of quadrupeds, especially the more bulky ones, as the elephant, elk, and the ox, in which, through its elasticity, it sustains the weight of the head, and thus economizes muscular power. In the same animals it also constitutes a strong layer in the abdominal wall, where it sustains the pressure of the contained viscera. Elastic tissue in its ordinary condition is dull yellow, opaque, tough, and coarsely fibrous. Yiewed by means of the microscope, it is found to be composed of re- ticulating fibres, the abruptly broken ends of which appear curled. The fibres vary exceed- ingly in diameter in different parts of the body. Those found in the subserous or sub- mucous tissues form nets of filaments almost as fine as those of fibrous tissue. Those of the yellow ligaments of the vertebrae measure about the goVo f an ^ ncn ^ n diameter. Fi- nally, in the middle coat of the blood-vessels the elastic tissue in part consists of wide reticu- lar bands, together having the appearance of a perforated membrane. 2 In the formation of ligaments and mem- branes, the bundles of elastic tissue composing ELASTIC TISSUE ' highly ma s nifled > from the yellow ligaments of the them are associated by areolar tissue, and the vertebra. The specimen is observed former also are invested with the same material to be composed of coarse anastomos- ing fibres. as the latter. Long boiling resolves elastic tissue into a brownish liquid, which smells like glue, but does not form a jelly on cooling. The structures composed of elastic tissue are furnished with few blood- vessels, the capillaries of which pursue the general course of the fibres 1 Yellow elastic tissue. 2 Perforated, or fenestrated membrane ; striated membrane. 176 THE TISSUES. of the former. The supply of nerves is small, and little is known in regard to them. FIG. 138. FIG. 139. ELASTIC TISSUE, from the middle coat of the pul- monary artery of the horse; highly magnified. ELASTIC TISSUE, from the middle coat of the ca- rotid artery of the horse; highly magnified. ADIPOSE TISSUE. Ad'ipose or fat tis'sue is remarkable as a physical element of the body, from the fact that it does not appear to be essential to the constitution of any organ. 'Its quantity depends much upon the condition of health, habits of life, and other circumstances of the individual ; in certain dis- eases, or from starvation, disappearing almost entirely ; in healthy per- sons frequently adding greatly to the bulk of the body, and sometimes accumulating to such an extent as in the condition itself to be viewed as a disease. It exists generally wherever connective tissue is found, occu- pying the areolae of the latter, and filling the interspaces of organs, thus contributing to the symmetry of form of the body. Examined microscopically, adipose tissue is observed to consist of masses of delicate, transparent vesicles, distended with a liquid, yellow- ish fat. From mutual pressure the fat vesicles are polyhedral, but when isolated are spherical and of variable diameter, but average the 7 J^ of an inch. They consist of nucleated cells, the nuclei of which are attached to the walls of the latter, and are rendered invisible by the presence of the contained oil. In emaciated or dropsical subjects these cells may often be detected with the nucleus distinctly visible, and with the cell contents consisting of a serous liquid and one or more drops of yellow oil. Adipose tissue forms a considerable and continuous layer 1 beneath the skin, lodged in the meshes of the dermis and in the adjacent connective tissue. In this position it is most abundant in the female, contributing 1 Panniculus adiposus. THE TISSUES. 177 mainly to her characteristic, rounded symmetry of form. It is especially thick beneath the skin of the breast, abdomen, and buttocks. In the palms of the hands and soles of the feet, it serves as an elastic cushion to relieve the influence of pressure, and is always present, even under the greatest ex- tent of emaciation. Mostly it is confined to the subcutaneous layer of the superficial fascia, and only when excessive does it pervade the deeper layer of the same fascia. The adipose tissue also occupies the inter- vals of muscles, the hollows of the temples and cheeks, and the interspaces of the important organs of the orbits. The disappearance of this material in disease gives rise to the sunken appearance of the eyes, the cheeks, and the temples. ADIPOSE TISSUE, WITH CONNECTIVE Adipose tissue also collects along the course TISSUE > from the 8U P erficial fascia of r . the abdomen; highly magnified. of the blood-vessels and nerves, especially those The groups of fat vesicles are ob- of the heart and intestines. It often accumu- served contained ** the meshes of connective tissue. lates in large quantity around the kidneys and the lower extremity of the rectum, and between the folds of the perito- neum ; according to its extent in these positions producing in a great measure the protuberant abdomen of fat persons. It likewise constitutes the marrow of the medullary cavities of bones, fills up intervals about the joints, and occupies the synovial folds ; but surrounding the articula- tions it is usually in less quantity than elsewhere subjacent to the skin. In the healthy condition, no adipose tissue exists in the subcutaneous connective tissue of the eyelids, and of the penis and scrotum. It also does not exist in the submucous connective tissue ; nor is it found in the interior of the cranium, the dura mater of the spinal cord, the eyeball, or the lungs. The blood-vessels of the adipose tissue form a capillary net, with polyhedral meshes, including the fat vesicles. Nerves are transmitted to important structures through adipose tissue, but appear to give it no branches. 12 FIG. 141. CHAPTER IV. THE MUSCULAR SYSTEM. THE Mus'cles 1 are the principal organs of motion in animals. They constitute the greater portion of the human body, and in an important degree contribute to the production of its outward form. They are numerous, of very different sizes, and of various shapes, dependent in some measure upon the position they occupy. They consist of a soft, red, fleshy part, named the belly, 2 usually attached, by means of ten'dons, between two or more points of the skeleton. The substance of the mus- cular belly, named flesh or mus'cle, is the active agent of motion, while the tendons are entirely passive, simply communi- eating the power of the former to the part to be moved. FIG. 142. TRANSVERSE SECTION or THE LOWER END OF THE ULNO-CARPAL FLEXOR, moderately magnified, a, section of tendon appearing as two crescents, composed of prismatic fasciculi of fibrous tissue; ft. a secondary fasciculus of crescentic shape, consisting of primary bundles of muscular fibres; c, a flattened cylindrical secondary fasciculus, consisting of primary bundles of muscular fibres; d, secondary and primary bundles in outline ; e, sheath of the mus- cle, composed of fibrous tissue. TRANSVERSE SECTION OF A MUSCULAR FASCICULUS, exhibiting its prismoid form, and its composition of pris- matic muscular fibres. From the biceps flexor of the arm. Highly mag- nified. The belly of a muscle is composed of an aggregation of peculiar, soft, red fibres, named mus'cular fi'bres. 3 These are collected into primary bundles, or fascic'uli, 4 which are associated into larger or secondary fascic'uli, and these again may unite in the formation of still coarser bundles, as those of the great gluteal muscle. The fibres and fasciculi 1 Musculi. Singular : musculus ; lacer- tus ; torus ; mys. 2 Venter, or medium musculi. (178) 3 Fleshy fibres. Sing.: fibrum muscu- lare ; fibrilla muscularis. 4 Lacerti musculorum. THE MUSCULAR SYSTEM. 179 FIG. 143. are held together and enveloped with delicate connective tissue, the fila- ments of which cross one another diagonally to the direction of the former, as represented in figure 143, so as to interfere in the least degree with muscular movement. The prismatic form of the fibres and fasciculi enables them to give the most com- pact condition to the muscles, and thus economize space. In some muscles the fasciculi run parallel to one another through- out the length of the former, as in the sartorius and gracilis muscles. In others, they converge from one attachment to the other, producing a triangular or ra'diated mus'cle, 1 as in the temporal and pectoral muscles. In some, the fasciculi converge toward both attachments, as in the biceps flexor of the arm. In others, the fasciculi converge from each side of a muscle to a median tendon, producing what is called a pen/niform mus'cle, 2 from its resemblance in arrangement to a feather, as in the rectus muscle of the thigh, or the dorsal interosseous muscles of the hand. When the fasciculi of a muscle proceed ob- liquely from one attachment to a tendon on the other side, a semi-pen/niform mus'cle is produced, 3 as in the case of the peroneal muscles of the leg. From their extent, muscles are often mentioned as long, short, and broad muscles; from their form, as triangular, quadrate, terete or rounded, fusiform, and ribbon-like muscles ; and from the direction of their fasciculi, as straight, oblique, and transverse muscles. The point of attachment of a muscle from which it ordinarily acts is called its origin, and the corresponding extremity of the muscle is named its head, The point of attachment which is to be moved is called the in- sertion. Generally, the origin is the point of attachment nearest the vert- ebral column. Functionally, the origin and insertion, if these be viewed as the fixed and moving points, will vary according to the circumstances in TWO PORTIONS OP A MUSCULAR FASCICULUS, from the trapezius muscle; highly magnified. 1, two por- tions of a muscular fasciculus, composed of pris- matic striated fibres terminating below, in rounded extremities, among the fibrous tissue of the com- mencing tendon ; 2, cut extremities of the fibres, showing their prismatic form; 3, delicate sheath composed of obliquely crossing filaments of fibrous tissue ; 4, the fibres of the commencing tendons. Partly a diagram. 1 M. radiatus. 2 M. penniformis ; m. pennatus. 3 M. semi-penniformis. 180 THE MUSCULAR SYSTEM. which the body is placed. Thus, the muscles emanating from the trunk and shoulders, which ordinarily raise the arms, by fixing the latter, may be made to raise the body, as instanced in the experiment of elevating the head to the level of a horizontal bar placed above it. The number of points of attachment of muscles varies, and thus the latter are said to arise by one, two or more heads, as the case may be. Prom the number of heads, the muscles are mentioned as single headed, biceps, triceps, and many headed. The number of insertions likewise vary, a muscle with a single head not unfrequently ending in a number of tendons of insertion, as in the common extensor of the fingers. The names of the muscles are derived from some prominent character, as the position, direction, form, attachments, number of heads, or physi- ological action. The ten'dons or sinews 1 vary in character, some consisting of the shortest attachment of the muscular belly to the points of origin and insertion, while some are spread out in broad membranous expansions, named aponeuro'ses, 2 and others form strong, flattened, cylindrical cords. They are bluish or yellowish white, longitudinally striated, and glisten- ing; and are very flexible but entirely inextensible. In their connection with the muscular bellies they usually commence in the interior as a wide expansion, or upon the exterior as an aponeurotic facing. From the belly, the tendons may continue with the same width to their origin and insertion, but frequently become gradually narrowed into flattened, cylin- dricalcords. As relates to the more intimate structure of the muscles, an examina- tion of both the muscular and tendinous tissue is required. FIG. 144. Two MUSCULAR FIBRES, from the lower end of the ulno-carpal flexor ; highly magnified. To the right of the figure, the muscular substance is observed to be gradually resolved 'among the fibrous tissue of the commencing tendon. The muscular fibres, viewed with the microscope, are found to be of variable diameter, though uniform in each case, and they average about the ^1 of an inch. They appear moderately translucent, pale 1 Leaders; thews. Sing.: tendo; tenon; pronervatio. 2 Sing. : expansio nervosa ; denervatio ; pronervatio. THE MUSCULAR SYSTEM. 181 reddish, faintly striated longitudinally, and distinctly and regularly stri- ated transversely, whence the name applied to them of striated muscu- lar fibres, 1 in contradistinction to those of the hollow viscera, which for the most part are unstriated. A further analysis of the muscular fibres proves each to consist of a bundle of numerous and exceedingly minute filaments, named muscular fi'brils, inclosed together in a delicate wall of structureless membrane called the myolem'ma. 2 The muscular fibrils are composed of highly refractive particles 3 of uniform size and arrangement, to which is due the regularly transverse striated appearance of the muscular fibres. FIG. 146. FIBRILS FROM A MUSCULAR FIBRE OF THE AXOLOTL, a batrachian reptile ; highly magnified, a, Bundle of fibrils; b, an isolated fibril. A MUSCULAR FIBRE OF A SALAMANDER, a batrachian reptile, which had been long kept in weak alcohol. 1, muscular substance ; 2, nuclei ; 3, muscular sub- stance split into disks ; 4, the myolemma. Occasionally the latter are broken in the direction of their transverse stria?, when they appear as if composed of a series of superimposed disks, as represented in figure 146. The muscular fasciculi, in approaching their tendinous connections, be- come pointed, from one muscular fibre after another ceasing in the ten- dinous structure. In many instances the muscular fibres terminate in rounded or bluntly-pointed extremities, but in other instances the fibrils of the fibres appear gradually to resolve themselves among the tendinous structure. 1 Striped muscular fibres. 2 Sarcolemma. 3 Myoline ; sarcous element, matter, or substance. 182 THE MUSCULAR SYSTEM. When treated with acetic acid the muscular fibres are rendered more translucent, and a number of elongated nuclei, imbedded among the fibrils, are brought into view. These nuclei remain from the organic cells, from which the muscular fibres were originally developed. Muscular fibres possess the property named contractility, which is excited ordinarily during life through impressions received from the ner- vous system, though a variety of stimuli, as mechanical irritation, chem- ical agencies, change of temperature, and electricity, are capable of call- ing it into action. By this property the muscles shorten or contract, and thus by approaching the two extremities move the insertion. When the contraction ceases, the muscles again become elongated, and the con- tractile power is lost only with the death of the muscular tissue. With the contraction there is a corresponding increase of bulk in the breadth and thickness of the muscle. When muscular fibres are observed con- tracting beneath the microscope, the transverse striae are observed to approach more closely, while the fibres increase their diameter. When muscles are inserted into soft organs, they usually have no ten- dinous attachment, but their fibres resolve themselves into the contiguous parts, as in the insertion of the muscles around the mouth. The tendons are composed of dense bundles of fibrous tissue, the fila- ments of which are associated with one another in a perfectly parallel manner. In the thicker tendons the finer bundles are collected into coarser prismatic fasciculi, associated by a looser texture of the same material, forming their connective tissue. From the parallel arrange- ment of the fibrous structure of the tendons they are rendered inexten- sible, which quality, together with their great strength and small size, admirably adapts them to communicate the power of the comparatively bulky muscular belly not only to distant parts, but also to very limited points of insertion. The muscles are invested with fibrous sheaths, continuous with those of the muscular fasciculi and with one another. Portions of these sheaths between muscles in many instances present a tendinous or apo- neurotic character, constituting the so-called internmscular partitions, from which the muscles in part frequently arise. The groups of muscles in different regions of the body are enveloped together in fibrous sheaths, named the fas'cise, as the brachial fascia, the femoral fascia, etc. These fasciae are usually denser or more aponeurotic in their character than the sheaths of the individual muscles. In many instances the latter partly arise from the fasciae, or are partly and even wholly inserted into them. To preserve the position of tendons in their course they are frequently confined in grooves, or upon narrow surfaces of the bones, by means of THE MUSCULAR SYSTEM. 183 appropriate ligaments, as in the passage of the extensor tendons through grooves at the carpal extremity of the radius, and the passage of the flexor tendons of the fingers beneath the annular ligament of the wrist and the vaginal ligaments of the phalanges. When muscles or their tendons pass over prominences of the bones, thin walled, serous pouches, named syno'vial bur'sae, 1 intervene, with the object of alleviating friction. Similar bursae are reflected upon ten- dons as they pass through grooves or beneath annular and vaginal liga- ments. In some instances these bursae are much divided or folded, as in the reflection of the synovial bursa upon the flexor tendons of the fingers as they pass beneath the annular ligament of the wrist. When muscles are accidentally torn, they are not restored by the re- production of muscular tissue, but the parts are reunited by means of ordinary fibrous tissue. The muscles are highly vascular, in accordance with their great activity. Their capillary blood-vessels generally pursue a course parallel to and between the muscular fibres, and frequently anastomose across the latter. The tendons are but slightly vascular. The lymphatic ves- sels are few in the muscles, and have not been detected in the tendons. Though possessing only a moderate degree of sensibility, the muscles are abundantly supplied with nerves, their office, however, being mainly to convey motor impressions. The terminal branches of the nerves anas- tomose with one another and form intricate plexuses among the muscular fibres. The tendons are almost devoid of nerves, and, at least in a con- dition of health, are entirely insensible. GENERAL REMARKS ON THE HEAD. The Head 2 is composed of the skull with its contents, covered with muscles and the skin. The cranial vault is covered with the occipito- frontal, temporal, and auricular muscles, and the scalp. The front of the cranium is the forehead, its back the occiput, and its sides the temples or tem/poral regions. The forehead 3 terminates below with the eyebrows and the intervening space, named glabel/la ; on each side is bounded by the temple, and above by the scalp. The occiput 4 extends between the position of the ears posteriorly, and is covered at its lower part by the muscles of the neck. The temple, 5 so called from the Latin tempus, time, because in this region white hairs first appear, is defined above by the course of the temporal ridge, below by the zygoma. 1 Bursse mucosse. 4 Occipitum ; regio occipitnlis ; inion. 2 Caput ; cephale ; poll. 5 Regio temporalis ; crotaphus. 3 Sinciput ; front ; irons : brow. 184 THE MUSCULAR SYSTEM. The Face, 1 formed by the forehead above, bounded by the base of the lower jaw below, and the ear on each side, presents to us in succession beneath the glabella : the root of the nose, which is its origin from the forehead ; the bridge or back of the nose ; 2 the column of the nose, 3 which separates the nostrils or anterior nares ; the labial groove* of the upper lip ; and the labio-mental groove, 5 between the lower lip and the chin. From the bridge slope off the sides of the nose, connected below with the dilated wings, which bound the nostrils externally. The fissure of the mouth is terminated on each side by the conjunction of the lips, named the angles of the mouth or oral angles, 6 The upper lip is denned on each side by the naso-labial furrow, 7 which becomes more marked with the advance of age. Below the eyebrows are the eyelids, separated by the pal'pebral fissure, the extremities of which are the angles or canthi of the eye, or of the orbit. The cheeks are bounded by the zygoma, the ear, the angle and base of the lower jaw, the chin, lips, and nose. The space in the vicinity of the ear extending to the angle of the jaw and the sterno-mastoid prominence of the neck, is the parotid region, The scalp 8 or skin of the vault of the cranium where covered with hair, is thick, dense, and inextensible ; and its deeper part is filled with hair follicles, sweat glands, and sebaceous glands, associated with adipose tissue. On the forehead and temples it is thinnest and most extensible. The hairs of the scalp diverge in whorls from a central point at the top of the head, called the crown or vertex, 9 The scalp tightly adheres by short connective tissue to the occipito-frontal muscles, and follows all their movements ; but the skin alone of the forehead is thrown into transverse wrinkles by the contraction of their frontal bel- lies. The skin of the eyebrows is thick and dense, and is moved with that of the forehead. The skin of the eyelids is thin, and the con- nective tissue attaching it to the orbicular muscle beneath is devoid of fat. In injuries about the entrance of the orbit, blood readily pervades this connective tissue, giving rise to what is commonly called "black eye." The skin of the nose is thin and movable above, but is thicker, more dense, and intimately connected with the subjacent part below, in which position it is filled with large sebaceous glands. The skin 1 Facies ; vultus ; prosopon. 5 Sulcus mento-labialis. 2 Dorsum nasi. 6 Commissures of the mouth. 3 Columna nasi. 7 Sulcus naso-labialis. 4 Philtrum ; amatorium ; amabile ; sul- 8 Capillitium. cus, or lacuna labii superioris. 9 Spondylus. THE MUSCULAR SYSTEM. 185 of the lips, where furnished with large hairs, is thick ; but at the borders is very thin and closely adherent to the orbicular muscle. The skin of the chin is thick, filled with hair follicles, sebaceous and sweat glands, and is most intimately blended with the muscles beneath. The skin of the cheeks is thin, and closely associated with a thick subcutaneous adipose layer involving several of the muscles ; and in the interval of the masseter and buccinator muscles, the cheek is occupied with a large mass of soft fat tissue. The skin at the back part of the cheek is like that of the chin, though less dense, and is not blended with the contiguous muscles. FASCIA OF THE HEAD. Fasciae readily separated from the contiguous parts as distinct layers, on the head are found only in the temporal region. In other positions they are represented by the thin and closely adherent investments of the muscles of the scalp and face, and by the subcutaneous adipose layer. The Superficial temporal fascia 1 is a thin but distinct layer of loose fibrous tissue beneath the skin of the temple. It is attached above to the aponeurosis of the occipito-frontal muscle, and is continuous with the thin layers of connective tissue investing the fleshy bellies of the latter and the palpebral orbicular muscle. It incloses the auricular muscles and the superficial temporal blood-vessels. The Deep temporal fascia 2 is a strong, bluish-white and shining fibrous membrane extended between the curved boundary of the tem- poral fossa and the zygoma. Its lower part is divided into two layers, between which is some loose areolar tissue and more or less fat. The inner surface of the fascia affords a point of origin to the temporal muscle. MUSCLES OF THE SCALP. The Occip'ito-front'al mus'cle 3 extends from the occiput to the fore- head, and consists of two fleshy bellies connected by an intermediate aponeurosis. The occipital belly, 4 shorter and narrower than the other, arises from the superior semicircular ridge of the occipital bone, and ascends in an inward direction to its aponeurosis. 1 Fascia temporalis superficial. 3 M. occipito frontalis; m. epicranius ; 2 Fascia temporalis profunda; f. tern- m. digastricus cranii. poralis ; temporal aponeurosis. 4 M. occipitalis. 186 THE MUSCULAR SYSTEM. The frontal belly, 1 paler than the former, arises from the internal angular FlG 147 process and superciliary ridge of the frontal bone, and ascends to its apo- neurosis. A prolongation from this belly, at the root of the nose to the nasal compressor mus- cle, is usually described as distinct, under the name of the nasal pyramidal muscle. 2 The occipito-frontal aponeurosis 3 is a thin sheet of tendinous fibres cover- ing the upper part of the head continuously from side to side. Between the occipital bellies of the two muscles it is attached to the occipital protuber- ance, and in the vicinity of the temporal ridge on each side is blended with the superficial temporal fascia. It is loosely at- tached to the periosteum beneath, but is closely ad- herent to the integument above, so that in the ac- tion of its muscular bellies the scalp is moved back- ward and forward on the cranium. MUSCLES OF THE HEAD AND NECK. 1, 2, occipito-frontal muscle : 1, its frontal belly; 2, its occipital belly; 3, nasal pyramidal mus- cle; 4, superior, and 5, posterior auricular muscles; 7, labio-nasal elevator; 8, elevator of the upper lip; 9, nasal compressor ; 10, 11, zygomatic muscles ; 12, masseter muscle ; 13, buccinator ; 14, de- pressor of the oral angle ; 15, oral orbicular muscle ; 16, elevator of the oral angle ; 17, 18, depressor of the lower lip ; T, sterno- mastoid* muscle; 20, trapezius; 21, posterior belly of the digastric and the sty lo-hyoid muscle ; 22, anterior belly of the former ; 23, loop of fibrous tissue attaching the tendon of the digastric mus- cle to the hyoid bone; 24, omo-hyoid muscle; 25, sterno-hyoid; 26, sterno-thyroid, seen to the outer side and behind the anterior belly of the omo-hyoid; 27, mylo-hyoid; 28, splenius; 29, elevator of the scapular angle; 30, 31, middle and anterior scalene mus- cles ; 32, clavicle. 1 M. frontalis. 2 M. pyramidalis nasi ; m. nasum dila- tans ; m. processus nasi ; fronto-nasal muscle. 3 Epicranial aponeurosis ; membrana epicrania ; galea capitis ; galea aponeu- rotica capitis ; g. tendinea Saritorini. THE MUSCULAR SYSTEM. 187 MUSCLES OF THE EYELIDS AND EYEBROWS. The Pal'pebral Orbic'ular muscle 1 forms a thin elliptical layer sur- rounding the entrance of the orbit, immediately beneath the skin. It arises from the internal angular process of the frontal bone, the nasal process of the superior maxillary bone, and the internal palpebral liga- ment. From this origin the muscle proceeds outwardly in the upper eye- lid and the eyebrow, and returns below the palpebral fissure to be inserted into the same points from which it started. The portion corresponding with the eyelids is thinner and paler than elsewhere, and has been described as distinct under the name of the ciliary muscle. 2 A fasci- culus or offset, springing from the back part of the lachrymal bone and passing upon the eyelids along the course of the lachrymal canals, was particularly described, by the late Professor Horner, under the name of the tar'sal ten/sor. 3 The palpebral orbicular muscle closes the eyelids and draws the skin in a radiating manner toward the inner angle. The ciliary portion is constantly engaged in the act of winking. The Pal'pebral Ele'vator muscle 4 is contained within the orbit. It arises above the optic foramen, and passes forward beneath the roof of the orbit ; expanding in its course, and terminating in a broad, thin ten- don, it is inserted into the edge of the superior palpebral cartilage. As indicated by the name, the muscle raises the upper eyelid. The Superciliary muscle 5 arises from the inner extremity of the super- ciliary ridge, and proceeds outwardly and a little upward to become blended with the palpebral orbicular and occipito-frontal muscles, between which and the bone it is situated. The muscles of the two sides throw the skin at the middle of the fore- head into vertical wrinkles, as in frowning. 1 M. orbicularis palpebrarum; m. o. 4 M. levator palpebrge superioris; pal- oculi ; m. pal. ciliaris ; m. palpebralis ; pebrse superioris primus ; apericus pal- m. naso-palpebralis ; m. maxillo-palpe- pebrarum rectus ; seclusor palpebrarum; bralis ; m. orbicularis latus ; palpebra- apertor oculi ; orbito-palpebral muscle, rum duo musculi ; sphincter, or constric- 5 M. superciliaris ; m. supercilii ; m. tor palpebrarum, or oculi. corrugator supercilii ; m. c. frontis ; m. 2 M. ciliaris. c. Coiterii ; m. cutaneo- or fronto-super- 3 M. tensor tarsi ; m. Horneri; m. sacci ciliaris; m. frontalis verus. lachrymalis. 188 THE MUSCULAR SYSTEM. MUSCLES OF THE EYEBALL. See the Account of the Eye. MUSCLES OF THE EAR. See the Account of the Ear. MUSCLES OF THE NOSE. The Na'sal Compressor 1 is a thin, triangular muscle arising from the fore part of the superior maxillary bone and diverging upon the side of the nose. On the back of the latter it terminates in a thin aponeurosis, which conjoins that of the opposite side, is attached to the tip of the nose, and is connected with a pair of fleshy slips 2 from the occipito-frontal muscles. The Na'sal Dila'tor 3 consists of short, indistinct muscular fibres, situ- ated between the cartilages of the wing of the nose and the skin, with which they are intimately blended. MUSCLES OF THE LIPS AND CHEEK. The O'ral Orbic'ular muscle 4 is an elliptical fasciculus of fibres sur- rounding the mouth, and blended with all the muscles which converge to it. At the angles of the mouth its fibres, except the most superficial ones, decussate with those of the buccinators, and with the elevators and depressors of the oral angles. This muscle is a sphincter, and antagonizes all the other muscles of the mouth. When closely contracted, it projects the lips as in the acts of kissing and sucking. The LaVio-na'sal el'evator 5 arises from the nasal process of the supe- 1 M. compressor naris ; m. transver- 4 M. orbicularis oris ; m. constrictor sails nasi ; m. triangularis nasi ; m. na- oris ; m. sphincter labiorum ; m. oscula- salis ; m. rinalus ; m. myrtiformis ; m. torius ; m. basiator ; m. labialis ; m. semi- constrictor naris ; in. dilatator alae nasi. or demi- orbicularis ; m. supra-semi-or- 2 Nasal pyramidal muscles. bicularis. 3 M. levator proprius alse nasi anterior 5 M. levator labii superioris alaeque et posterior ; m. dilatator naris ant. et nasi ; elevator of the upper lip and wing post. ; m. pinnse dilatator. of the nose ; m. incisiyus lateralis et pyramidalis. THE MUSCULAR SYSTEM. 189 rior maxillary bone, and as it descends separates into two fasciculi, of which one is inserted into the wing of the nose, while the other is pro- longed to the upper lip, where it is blended with the contiguous muscles. The La'bio-na'sal depress'or 1 is a small muscular slip situated just exterior to the mucous membrane of the upper lip at the side of the fraenum. It arises from the point of the incisive alveoli of the superior maxillary bone, and ascends to be inserted into the wing and column of the nose and become blended with the upper margin of the oral orbicular muscle. The El'evator of the Upper Lip 2 arises from the malar and superior maxillary bones just above the infra-orbital foramen, and descends to become blended with the contiguous muscles of the upper lip. The El'evator of the O'ral Angle 3 is partially concealed by the pre- ceding muscle. It arises from the superior maxillary bone below the infra-orbital foramen, and descends in a convergent manner to the angle of the mouth. Between it and the elevator of the upper lip are the infra-orbital nerve and artery. The Zygomat'ic muscles are two narrow fasciculi extending obliquely from the most prominent part of the cheek to the angle of the mouth. The Larger Zygomat'ic muscle, 4 external to the smaller one, arises from the zygomatic process of the malar bone, and, after reaching the angle of the mouth, becomes blended with the contiguous muscles. The Smaller Zygomat'ic muscle 5 is inconstant in size and exact position, and occasionally is absent. It arises from the malar bone, and terminates near the angle of the mouth by blending with the elevator of the upper lip. The zygomatic muscles elevate the angles of the mouth outwardly, as in smiling. The Depress'or of the Lower Lip, 6 a square muscle situated at the 1 M. depressor labii superioris alaeque abducens labiorum ; m. elevator labio- nasi ; depressor of the upper lip and of rum communis. the wing of the nose ; m. depressor alee 4 M. zygomaticus major ; m. distorter nasi ; m. myrtiformis. oris ; zygomato-labial muscle. 2 M. levator labii superioris ; m. in- 5 M. zygomaticus minor ; small zygo- cisivus. mato-labial muscle. 3 M. levator anguli oris; elevator of 6 M. depressor labii inferioris; m.quad- the angle of the mouth ; m. caninus ; m. ratis menti ; m. mento-labialis. 190 THE MUSCULAR SYSTEM. side of the chin, arises from the base of the lower jaw and ascends in- wardly to be inserted into the lower lip. The El'evator of the Lower Lip 1 is a small square muscle situated just exterior to the mucous membrane of the lower lip at the side of the frasnum. It arises from the front of the outer incisive and canine alveoli of the lower jaw, and descends inwardly to be inserted into the lower lip. The Depress'or of the O'ral Angle 2 is a triangular muscle, which arises from the base of the lower jaw at the side of the chin, and is inserted by its apex into the angle of the mouth, where it blends with the contiguous muscles. The Buccina'tor muscle 3 contributes to the formation of the cheek. It arises from the pterygo-rnaxillary ligament and from the alveolar border of both jaws as far forward as the first molar tooth. From these points the fibres proceed forward and converge to the angle of the mouth, where they cross one another and become confluent with the oral orbicu- lar muscle. Internally it is in contact with the mucous membrane of the mouth, and externally is closely invested with a thin fascia. Its back part is sepa- rated from the ramus of the lower jaw by means of a mass of fat, re- markable for its softness and slight attachment to the contiguous struct- ures. The disappearance of this fat in emaciation gives rise to the hollow cheek. Opposite the second molar tooth of the upper jaw the buccinator is perforated by the termination of the parotid duct. When the buccinators alone contract, they widen the mouth ; but if they contract in conjunction with the oral orbicular muscle, they press the cheeks close to the jaws ; or if the mouth is filled with air, this is com- pressed, as in the acts of blowing and whistling. The Pter'ygo-max'illary lig'ament is a fibrous band, extended be- tween the external pterygoid process of the sphenoid bone and the pos- terior end of the molar ridge of the lower jaw, serving as a common origin to the buccinator muscle and the superior constrictor of the pharynx. 1 M. levator labii inferior-is ; m. levator laris oris ; m. maxillo-labialis ; m. de- menti; m. incisivus inferior; m. penicil- pressor labiorum communis. latus ; mento-labial muscle. 3 M. retractor anguli oris ; m. bucco- 2 M. depressor anguli oris ; depressor alveolo-maxillaris ; m. alveolo-labialis ; of the angle of the mouth ; m. triangu- m. mansorius. THE MUSCULAR SYSTEM. 191 THE MUSCLES OF THE LOWER JAW, OR OF MASTICATION. The Mass'eter muscle, 1 thick and oblong square, is situated at the back of the cheek, and extended between the zygoma and angle of the lower jaw. It has a number of tendinous bands interspersed with its structure, and is separable into two portions, the fibres of which pursue a different course. The superficial and larger portion of the muscle arises tendinously from the upper maxillary bone and the lower margin of the malar bone, and descends backward to be in- FlG 143. serted into the lower half of the ramus and angle of the lower jaw. The deeper portion arises from the zygomatic process of the temporal bone, and descends a little forward to be inserted into the upper half of the ramus of the lower jaw. The External Ptery'goid muscle 2 is short, thick, and triangular, and occupies the upper part of the spheno-maxillary fossa. It arises from the under surface of the great wing and the outer surface of the external pterygoid process of the sphenoid bone, and converges to be inserted, by means of a short, thick tendon, into the depressed sur- face of the front of the neck of the lower jaw. Externally this muscle is crossed by the internal maxillary artery and the tendon of the temporal muscle ; and internally it is in contact with the internal pterygoid muscle and the inferior maxillary nerve. The Internal Pter'ygoid muscle 3 is square and thick, and is situated within the position of the ramus of the jaw. It arises from the ptery- 1 M. mandibularis ; m. zygomato-max- 3 M. pterygoideus interims, or major; illaris. m. masseter interims ; m. latens in ore ; 2 M. pterygoideus externus, or minor; m. pterygo-anguli-maxillaris ; m. ptery- m. pterygo-colli-maxillaris ; m. pterygo- go-maxillaris majus ; m. alaris, or ali- maxillaris minus; m. alaris, or aliformis formis major. minor. VIEW OF THE INTERIOR PART OF THE LEFT SIDE OF THE FACE. 1, condyle of the lower jaw ; 2, angle of the jaw ; 3, base ; 4, symphysis ; 5, sub-maxillary fossa; 6, attachment of the mylo-hyoid muscle to the corresponding ridge; 7, origin of the genio- hyoid muscles; 8, origin of the genio-glossal muscles; 9, masseter muscle; 10, internal ptery- goid muscle ; 11, external pterygoid muscle. 192 THE MUSCULAR SYSTEM. gold fossa, and descends outward and backward to be inserted into the inner surface of the ramus and angle of the lower jaw. The Tem/poral muscle 1 occupies the temporal fossa, and is covered by the temporal fascia. It arises from the entire surface of the former and from the upper part of the latter, and converges to an interior tendinous layer, which becomes a thick, flattened fasciculus, descending to be in- serted into the inner surface and anterior border of the coronoid process of the lower jaw. The temporal, masseter, and pterygoid muscles are the active agents in mastication. The movements produced are those of elevation of the lower jaw, together with a lateral, forward and backward motion. The elevation of the lower jaw, productive of firm 'pressure of the lower against the upper teeth, is the result of the contraction of the tem- poral muscles and the internal portions of the masseters. Depression of the lower jaw occurs by its weight alone, though aided by the digas- tric and other muscles extended between it and the hyoid bone, when this is fixed in its position. The grinding movement of the lower jaw is performed by the pterygoid, masseter, and temporal muscles. The external FIG. 149. VIEW OF THE TEMPORAL MUSCLE. The temporal fascia and zygoma removed. pterygoid muscles and the external portions of the masseter muscles draw the jaw forward ; the temporal muscles and internal portions of the masseters draw it back again ; and the internal pterygoid muscles, contracting alternately, draw the jaw to either side. 1 M. temporalis ; m. crotaphites ; m. arcadi-temporo-maxillaris ; m. temporo max- illaris. THE MUSCULAR SYSTEM. 1Q3 THE NECK. The Neck, 1 which forms the short cylindrical column connecting the head with the thorax, varies in length and thickness in different individ- uals of the same age and sex. Its bony axis is situated more posteriorly than anteriorly, in consequence of which the head is disposed to fall for- ward. The front of the neck, or the throat, 2 presents a prominence in the adult male, commonly called "Adam's apple." 3 This is produced by the larynx, which, from its less degree of development before puberty, and at all periods of life in the female, is not evident externally. The elevation on each sidq of the neck, descending from behind the position of the ear to the sternum, is produced by the sterno-mastoid muscles. The concavity between the latter just above the breast is the ju/gular fossa; 4 and the shallower depression outside of the muscle above the clavicle is the supra-clavic'ular fossa. 5 The skin of the neck is thin and movable, and is readily elevated into folds. The two conspicuous folds, observed in old people, descending from the sides of the chin toward the lower part of the neck, are pro- duced upon the anterior borders of the subcutaneous cervical muscles, which become extended through elevation of the lower jaw consequent on the loss of the teeth and their alveoli in both jaws. Beneath the muscles just mentioned is the cervical fascia, which incloses the sterno- mastoid muscles. The middle of the neck in front of the vertebra is occupied by the pharynx and oesophagus, the root of the tongue, the hyoid bone, the larynx and trachea, and the thyroid body. At the sides of these parts the principal cervical blood-vessels and nerves are situated, enveloped in the deep cervical fascia. MUSCLES AND FASCLE OF THE NECK. THE SUBCUTANEOUS CERVICAL MUSCLE. The Subcuta'neous Cer'vical muscle 6 is a broad, thin, and pale lam- ina arising in the connective tissue covering the upper part of the del- toid and pectoral muscles. Passing over the clavicle, it ascends the 1 Collum ; cervix ; trachelos ; anchen. 5 Fovea supra-clavicularis. -Guttur; jugulum. M. s. cervicis, or colli; m. platysm.-i 3 Pornum Adami; eminentia thyroid ea; myoides ; m. cutaneus ; in. latissimus nodus gutturis. colli; m. peaucier. 4 Fossa jngularis. 13 194 THE MUSCULAR SYSTEM. neck inwardly to the lower jaw, where its most anterior fibres join those of the opposite muscle, while others are inserted into the side of the chin, and become blended with the depressors of the lower lip and oral angle, and the most posterior ones terminate in the fascia investing the masseter muscle and parotid gland. A small offset 1 crosses the cheek transversely from over the masseter muscle to the vicinity of the angle of the mouth. This muscle will aid the depression of the lower jaw ; Jbut its main purpose appears to be to extend the skin of the neck between the cla- vicle and lower jaw, thus elevating it from the influence of exterior pres- sure upon the air-passages and blood-vessels. FIG. 150. THE CERVICAL FASCIA. Upon removing the subcutaneous cervical muscle, the Cer'vical fas'cia 2 is exposed to view. Its upper part forms a sheath for the parotid and submaxillary glands, which are separated from each other by a well- marked process of the fascia, called the sty'lo-max'illary lig'ament, 3 which extends from the styloid process of the temporal bone to the angle of the lower jaw, and inwardly to the sheath of the principal cervical blood-vessels. In advance of the parotid gland, the fascia invests the masseter muscle and adheres along the base of the lower jaw. At the lower part of the neck the fascia adheres along the upper bor- der of the sternum and clavicle, and is continuous in front of these bones with the thoracic fascia. Behind the neck, it is continuous with the layer inclosing the trapezius mus- cle ; and in proceeding forward it incloses the sterno-mastoid muscle, and the elevators and depressors of the hyoid bone and larynx. Processes of the fascia, continued inwardly, inclose the trachea and larynx, the oasophagus and pharynx ; form the sheath of the large cervical blood-vessels, and become continuous with the fibrous investment of the muscles in front of the cervical vertebras. INNER PART OF THE EAMUS OF THE LOWER JAW, right side. 1, temporal bone ; 2, lower jaw ; 3, capsular ligament of the articulation of the latter ; 4. spheno- maxillary ligament; 5, entrance of the inferior dental canal ; 6, stylo-maxillary ligament. 1 M. risorius Santorini. 2 Fascia cervicalis; fascia colli; fascia superficialis et profunda cervicis; super- ficial and deep or proper cervical fascia. 3 Ligamentum stylo-maxillare. THE MUSCULAR SYSTEM. 195 Another process, separating the pterygoid muscles, and extended from the spinous process of the sphenoid bone to the lower jaw at the inner border of the dental foramen, constitutes the sphe'no-max'illary lig'a- ment, 1 THE STERNO-MASTOID MUSCLE. ; The Ster'no-mas'toid FIG. 151. muscle 2 is the largest and most conspicuous of the muscles of the neck. It arises by a flat tendon from the upper fore part of the sternum, and ten- dinous and fleshy from the inner third of the clavicle. The two portions are sep- arated at their origin by an angular interval, but as the clavicular portion ascends nearly vertically, while the sternal portion inclines backward in its ascent, the two conjoin about the middle of the neck and form a single thick rounded belly, which proceeds to be inserted into the mastoid process and the superior semicircular line of the occipital bone. When the muscles of the two sides act together, the head is drawn downward; but when one alone contracts, the face is directed toward the opposite side. #*** UA& i& fe feu^ I DEPRESSORS OF THE HYOID BONE AND LARYNX. The Ster'no-hy'oid muscle 3 is a flat band arising from the inner sur- face of the upper part of the sternum and the contiguous portion of the FRONT VIEW OF THB MUSCLES OF THE NECK. 1, posterior, and 2, anterior belly of the digastric ; 3, its intermediate tendon at- tached to the hyoid bone and passing through the insertion of the Btylo-hyoid muscle, 4 ; 5, mylo-hyoid ; 6, genio-hyoid ; 7, genio- glossal muscle of the tongue ; 8, hyo-glossal ; 9, stylo-glossal ; 10, stylo-pharyngeal muscle ; 11, sterno-mastoid muscle ; 12, its ster- nal origin; 13, its clavicular origin; 14, sterno-hyoid ; 15, sterno- thyroid ; 16, thyro-hyoid ; 17, 18, omo-hyoid muscle ; 19, trape- zius ; 20, anterior scalene muscle ; 21, middle scalene muscle. 1 Erroneously described under the name of internal lateral ligament of the articu- lation of the lower jaw. 2 M. sterno-mastoideus ; m. sterno- cleido-mastoideus ; m. cleido-mastoideus; m. mastoideus ; m. metator capitis. 3 M. sterno-hyoideus ; m. sterno-clei- do-hyoideus ; m. hyoides primus. 196 THE MUSCULAR SYSTEM. clavicle. Ascending the neck inwardly, it is inserted into the lower bor- der of the body of the hyoid bone. The Ster'no-thy'roid muscle, 1 broader than the preceding, arises from the inner surface of the upper part of the sternum, and ascends the neck between the former muscle and the trachea, to be inserted into the oblique line at the side of the thyroid cartilage. The Thy'ro-hy'oid muscle, 2 apparently a continuation of the muscle just described, arises from the oblique line of the thyroid cartilage, and ascends to be inserted into the lower border of the hyoid bone. The O'mo-hy'oid muscle 3 consists of two fleshy bellies united by an intermediate tendon. It arises from the upper border of the scapula, in the vicinity of the coracoid foramen, crosses the neck in an oblique man- ner beneath the sterno-mastoid muscle, and is inserted into the lower margin of the body of the hyoid bone. The two bellies of the muscle in their course form an obtuse angle with each other, and this position is maintained by a connection of their tendon with the cervical fascia. Besides depressing the hyoid bone and larynx, the omo-hyoid muscles fix the median position of these parts in the neck. ELEVATORS OF THE HYOID BONE AND LARYNX. The Digas'tric muscle, 4 as indicated by the name, consists of two fleshy bellies which are united by an intermediate rounded tendon. The posterior belly arises from the digastric fossa of the temporal bone, and the anterior belly from the inner surface of the lower jaw near its sym- physis. Both descend to the side of the hyoid bone, where their inter- vening tendon passes through the insertion of the stylo-hyoid muscle, and is attached to the former by means of a fibrous band. A thin aponeu- rosis, continuous with the latter, is extended between the anterior bellies of the two muscles. . The Sty'lo-hy'oid muscle 5 lies in contact with the posterior belly of the preceding muscle. It arises from the middle of the styloid process of 1 M. sterno-thyroideus; m. bronchius. 4 M. digastricus; m. biventer; m. b. a M. thyro-hyoideus ; m. hyo-thyroi- maxillae ; m. deprimens maxillae biven- deus. ter ; m. bigaster. 3 M. omo-hyoideus : m. coraco-hyoi- 5 M. stylo hyoideus; m. stylo-hyoides deus; m. scnpula-liy< ideus; m. hyoidus major; m. stylo-ceratoides; in. stylo- quartus. cerato-byoideus. THE MUSCULAR SYSTEM. 197 the temporal bone, and descends to be inserted into the side of the body of the hyoid bone, where it is perforated by the tendon of the digastric muscle. The My'lo-hy'oid muscle 1 is a triangular layer, forming with its fellow of the opposite side the muscular floor of the mouth. It arises from the molar ridge of the lower jaw, from whence its fibres proceed obliquely inward to conjoin with those of the opposite muscle, in the median line, extending from the chin to the hyoid bone. The Geni'o-hy'oid muscle 2 is a slender band arising from the posterior mental tubercle, and descending in contact with the corresponding mus- cle of the other side, to be inserted into the body of the hyoid bone. It is situated between the inner part of the nfylo-hyoid and the genio- glossal muscle. MUSCLES OF THE TONGUE, PALATE, AND PHARYNX. See the account of these different organs. MUSCLES OF THE LARYNX. See the account of this organ. DEEP MUSCLES OF THE FRONT OF THE NECK. The Anterior Scalene' muscle 3 is deeply situated at the lower part of the side of the neck. It arises from the transverse processes of the third to the sixth cervical vertebra inclusively, and descends to be in- serted into the anterior part of the first rib. In front of the insertion of this muscle the subclavian vein passes over the first rib. The Middle Scalene' muscle 4 arises from all the cervical transverse processes, usually excepting the fif^t, and descends behind the preceding muscle to be inserted into the posterior half of the first rib. Between the anterior and middle scalene muscles the axillary plexus of nerves and the subclavian artery take their course. 1 M. mylo-hyoideus ; m. mylo-pharyn- 3 M. scalenus aniicus; m. s. prior; m. geus. costo trachelius. 2 M. genio-hyoideus ; m. mento-bicor- * M. scalenus medius ; m. s. secundus. neus. / 198 THE MUSCULAR SYSTEM. The Posterior Scalene' muscle, 1 small and thin, arises from the two or three lower cervical transverse processes, and descends to be inserted into the back part of the second FIG. 152. r ib. The scalene muscles act- ing from above elevate the ribs ; but acting from be- low they flex the neck. The Larger Straight muscle 2 arises by as many distinct tendinous heads, from the third to the sixth cervical transverse proc- esses inclusively, and as- cends inwardly to be in- serted into the basilar process of the occipital bone. The Smaller Straight muscle 3 -arises from the side of the atlas, and as- cends inwardly to be in- serted into the basilar process, beneath the last muscle. The two straight mus- cles are flexors of the head. DEEP MUSCLES OF THE FROXT OF THE NECK. 1, basilar process of the occipital bone; 2, mastoid process; 3, larger straight mus- cle; 4, smaller straight muscle; 5, lateral straight muscle; 6,7, long cervical muscles; 8, posterior scalene muscle; 9, anterior scalene muscle ; 10, middle scalene muscle; 11, 12, first and second ribs; 13, position at which the subclavian artery and axillary plexus of nerves emerge over the first rib, between the anterior and middle scalene muscles ; 14, third dorsal vertebra; 15, atlas; i6, 17, intertransverse muscles. The Long Cer'vical muscle 4 extends along the side of the neck, and is quite complex in its arrangement. It consists of two portions, of which one arises from the side of the bodies of the three upper dor- sal and the three lower cervical vertebrae, and ascends to be inserted by distinct tendons into the fourth and fj|ya cervical transverse processes, and partially tendinous and fleshy into the bodies of the second, third, and fourth cervical vertebrae. The remaining portion arises by distinct ten- 1 M. scalenus posticus ; m. s. tertius. 2 M. rectus capitis anticus major; m. r. c. internus major; m. r. c. anterior longus ; m. trachelo-basilaris ; larger an- terior straight muscle. 3 M. rectus capitis anticus minor ; m. r. c. internus minor; m. r. c. anterior brevis; m. trachleo-basilaris minus; m. rennuens ; m. annuens ; smaller anterior straight muscle. 4 M. longus colli ; m. pre-dorso-cervi- calis ; m. pre-dorso-atloideus. V THE MUSCULAR SYSTEM. 199 dons from the third, fourth, and fifth cervical transverse processes, and ascends to conjoin with the preceding portion and to be inserted in front of the atlas. This muscle bends the neck forward. TOPOGRAPHICAL SKETCH OF THE ANATOMY OF THE NECK. Upon removing the skin of the neck and the subcutaneous cervical muscle, the cervical fascia is exposed, with, the external jugular vein de- scending from behind the angle of the jaw to about the middle of the clavicle, where it dips inward to join the subclavian vein. Upon removing the superficial layer of the cervical fascia, the sterno-mastoid muscle is seen pursuing its course from the sternum to the mastoid process, and beneath it, crossing the neck in an opposite flfirection, is the omo-hyoid muscle. If the line of the latter be continued to 'the chin, the side of the neck will be divided by the two muscles into four triangles. The posterior cer'vical triangle is occupied with muscles, to be described in the account of the back. The anterior cer'vical triangle contains the root of the tongue, the hyoid bone, larynx and trachea, and, behind these, the pharynx and oeso- phagus. The larynx and trachea are covered by the depressor muscles of those organs ; and beneath them, on the trachea, is the thyroid gland. The lower part of this triangle corresponds with the depression above the sternum, called the ju/gular fossa. The inferior cer'vical triangle corresponds with the supra-clavic'ular fossa, The deeper layer of the cervical fascia being removed from it, a quantity of loose areolar tissue, containing the supra- clavicular lymphatic glands, is- exposed. Upon removing the latter, the triangle will be found to extend into a deep fossa between the clavicle and first rib, and con- tinuous outwardly with the axilla. The extent of the fossa varies with the position of the shoulder. If this is elevated and thrown back, the fossa is deepened and narrowed ; if depressed:- and thrown forward, the fossa is rendered shallower and broader, and its parts become more dis- tinctly visible. Crossing the loirar part of the triangle are the supra- scapular and transverse cervical blood-vessels. At the outer part of the triangle the scalene muscles are seen descending from the cervical verte- bra to the first rib. In front of the insertion of the anterior scalene muscle the subclavian vein passes over the first rib. Between the anterior and middle scalene muscles the subclavian artery and axillary plexus of nerves emerge in their course to the axilla. The superior cer'vical triangle corresponds with the submax'illary fossa, Its upper part contains the subrnaxillary gland, lodged in an oval 200 depression of the deeper layer of the cervical fascia, the outer portion of which is a partition separating it from the parotid gland, and corre- sponding with the sty'lo-max'illary ligament. If the deeper layer of the cervical fascia is removed, above the submaxillary gland, the muscu- lar floor of the mouth is seen, formed by the mylo-hyoid muscle; and below the gland are the stylo-hyoid and digastric muscles. At the outer border of the triangle is the external carotid artery, from which diverge forward, in succession from below, the superior thyroid, lingual, and facial arteries. Curving across the triangle below the digastric muscle is seen the hypo-glossal nerve, giving off a descending branch to the depressor muscles of the hyoid bone. Upon detaching the sterno-mastoid muscle, the great cervical vessels are observed inclosed within a sheath and ascending the neck from the position of the sterno-clavicular junction toward the angle of the jaw. The sheath being opened, is seen to contain the primitive carotid artery at the inner side, the internal jugular vein to the outer side, and the pneumogastric nerve between them. The primitive carotid artery divides opposite the upper border of the larynx into the external and internal carotids, the former of which ascends to penetrate the parotid gland; the latter takes a deeper course to reach the carotid canal of the temporal bone. Behind the great cervical vessels lies the sympathetic nerve, and to their outer side a chain of lymphatic glands. FKONT OF THE THORAX. The front of the Thorax or chest, usually called the breast or bosom, on each side extends to the shoulder, the armpit, and the back. Be- low the clavicle it is slightly depressed, forming there the infra-clavicu- lar fossa. In lean persons it exhibits the outlines of the sternum and ribs, in vigorously muscular men the outlines of the superficial muscles, and in fat persons hemispherical elevations corresponding with the mamma3. At the lower part of the sternum, over the position of the ensiform cartilage, is a depression, "the pit of the stomach." 1 From this the lower border of the thorax^Hopes off on each side downward and outward. The skin of the breast is thin, readily raised into folds on each side, but adheres more closely over the sternum. Beneath it, is a layer of fascia containing more or less fat, excepting over the position of the sternum. Beneath the fatty layer 2 is a thin layer of fascia invest- ing the muscles. 1 Scrobiculus cordis ; procardium; nnticnrd.ium. 2 Panniculus adiposus. THE MUSCULAR SYSTEM. 201 MUSCLES OF THE FRONT AND SIDES OF THE THORAX. The Great Pec'toral muscle 1 occupies the front of the upper part of the chest and axilla. It arises from the sternal two-thirds of the clavicle, the front of the sternum and the upper six costal cartilages, and FIG. 153. MUSCLES OF THE FRONT OF THE THORAX AND ABDOMEN. 1, great pectoral muscle; 2, deltoid muBcle; 3, latissiinus muscle; 4, great serrated muscle; 5, subclavian muscle ; 6, small pectoral muscle; 7, coraco- brachial muscle; 8, biceps flexor; 9, coracoid process of the scapula; 10, origin of the great serrated muscle; 11, intercostal muscles: 12, external oblique muscle of the abdomen; 13, its aponeurosis; 14, lower border of the latter, named Poupart's ligament ; 15, external abdominal ring, the lower extremity of the inguinal canal; 16, straight muscle of the abdomen; 17, pyramidal muscle; 18, internal oblique muscle ; 19, conjoined tendon of the internal oblique and transverse muscles ; 20, position of the inguinal canal below the arching edges of the preceding two muscles. from the aponeurosis of the external oblique muscle of the abdomen. Proceeding outwardly, its fleshy fasciculi converge to a broad tendon, 1 Greater pectoral muscle; m. pectoralis major; m. adductor brachii; m. sterno- humeralis; m. sterno-costo-clavi-humeralis; m. sterno-cleido-brachialis. 202 THE MUSCULAR SYSTEM. which is inserted into the anterior margin of the bicipital groove of the humerus. The clavicular portion of the muscle is separated from the other by an interval filled with connective tissue. The outer portion of the muscle, with its tendon, is doubled on itself so as to produce the thick anterior fold of the axilla, and the lower fleshy fasciculi by this arrange- ment .become inserted into the humerus higher than the upper ones. The Small Pec'toral muscle 1 lies beneath the preceding muscle, and arises by serrations from the third, fourth, and fifth ribs. Proceeding upward and outward, its fibres converge to a short tendon, which is inserted into the"" coracoid process of the scapula. The great pectoral muscle draws the arm downward and forward, in which movement it is aided by the small pectoral muscle drawing the shoulder in the same direction. If the bones of the shoulder and arm are fixed, the pectorals aid in respiration by elevating the ribs. The Sub-clav'ian muscle 2 arises by a short tendon from the first costal cartilage, and is inserted along the under surface of the clavicle. Exter- nally it is invested with a strong fascia, the cos'to-cor'acoid membrane, 3 which starts from the end of the coracoid process, and diverges upward and inward to be attached along the under margin of the clavicle and the anterior end of the first rib. The Great Ser'rated muscle 4 is a broad quadrate fleshy layer situated at the side of the thorax. It arises by angular serrations from the upper eight or nine ribs in advance of their middle, and proceeds backward to be inserted into the inner aspect of the base of the scapula. The five lower serrations alternate with as many points of origin of the external oblique muscle of the abdomen. Internally it is in contact with the ribs and intercostal muscles, externally it is subcutaneous, reach- ing upward into the axilla between the pectoral and latissimus muscles. It draws the scapula, and with it the whole shoulder, forward, or, if the latter is fixed, it may contribute to respiration by aiding the pectoral muscles in elevating the ribs, and thus increasing the capacity of the thorax. 1 Smaller pectoral muscle ; m. pecto - vicular fascia : bifid ligament ; liga- ralis minor ; m. serratus anticus minor ; mentum bicorne. m. costo-coracoideus. 4 Anterior great serrated muscle ; m. 3 M. subclavius, subclavicularis, or serratus magnus anticus ; m. s. major ; subclavianus ; m. costo-clavicularis. m. costo-scapularis ; m. costo-basi-scap- 3 Ligamentum costo-coracoideum ; cla- ularis. THE MUSCULAR SYSTEM. 203 THE BACK. The Back, 1 as the term is commonly used, applies to the posterior part of the trunk, but, in its most restricted sense, refers to the posterior part of the thorax. 2 A groove descends along the median line of the back, which is deepened in fat persons from the deposit of adipose tissue occurring on each side, while the skin tightly adheres to the summits of the spinous processes. On each side of the thorax, the scapula and its muscles produce a prominence, which is convex in stout individuals, but exhibits the outline of the scapula, with its projecting spine, in thin persons. The skin of the back is thicker and denser than in any other position of the body. It is attached to the parts beneath by long, extensible con- nective tissue, which allows it readily to be moved or raised into folds. The muscles of the back are invested with a thin layer of fascia, inde- pendently of the extensible areolar tissue just mentioned. They are divided into superficial and deep muscles ; the former being broad, and for the most part intended to move the upper extremities. The latter are comparatively long and narrow, occupy the gutters along the verte- bral column, and are intended to maintain the erect position of this and the head. SUPERFICIAL MUSCLES OF THE BACK. The Trape'zius muscle 3 arises from the superior curved line and pro- tuberance of the occipital bone, the nuchal ligament, and the summits of the spinous processes of the dorsal vertebrae. From this extensive ori- gin it converges, to be inserted into the outer third of the clavicle and into the upper margin of the acromion and spine of the scapula. Between the spinous processes, the muscles of the two sides conjoin by means of intervening tendinous fibres. The lower fibres of the muscle, in their ascent, as they approach the scapula, become tendinous, and glide upon the triangular surface at the commencement of its spine. The muscles of the two sides together have the outline of a trape- zium, whence their name. They fix the position of the shoulders, in the respiratory action of the pectoral and great serrated muscles. They also draw them upward, directly backward, or downward, according as their upper, middle, or lower fasciculi contract separately. If the 1 Dorsum ; tergum ; notos ; noton ; 3 M. trapezius ; m. cucullaris ; m. metaphrenon. mensalis ; m. dorso-supra-acromialis ; m. 2 Dorsum ; dorsal region. occipito-dorsi-acromialis. 204 THE MUSCULAR SYSTEM. shoulders are fixed, they may draw the head backward ; or, if one alone acts, it may draw the latter to one side. FIG. 154. MUSCLES OF THE BACK. 1, 2, trapezius; 3, acromion; 4, latissimus; 5, deltoid: G, infra-spiuou.-i. and to its outer side the terete muscles ; 7, external oblique muscle of the abdomen ; 8, middle glutoal ; 9, external gluteal muscle; 10, elevator of the scapular angle; 11, 12, rhomboid muscles; 13, 14, splenius ; 15, aponcu- rosis extending from the superior to the inferior serrated muscle, 16; 17, supra-spinous; IS, infra-spinous muscle; 19, lesser terete, and 20, greater terete muscle; 21, triceps extensor; 22, great serrated muscle; 23, internal oblique muscle of the abdomen. The Latis'simus muscle 1 occupies the lower part of the back, extend- ing upwardly along the side of the thorax to the back of the humerus. It arises by a thin aponeurosis from the spinous processes of the lower six dorsal vertebrae, and all of those of the lumbar vertebra and sacrum ; from the posterior third of the crest of the ilium, and from the lumbar fascia. Its broad, fleshy belly ascends outwardly, in its course receiving 1 M. latissimus dorsi; m. dorsi-lumbo-sacro-humeralis; m. lumbo-humeralis; m. scalptor ani; m. tersor ani; m. brachium movens quartus. . THE MUSCULAR SYSTEM. 205 fasciculi from the lower three ribs. It glides over the inferior angle of the scapula, from which it also usually receives a slip, and converges to a broad, tendinous band inserted into the posterior border of the bicip- ital groove of the humerus. Folding around the greater terete muscle, it forms the posterior boundary of the axilla ; and, like the great pec- toral muscle, it has its lowest fasciculi inserted highest into the humerus. A synovial bursa is interposed between the muscle and the inferior angle of the scapula, and another between its tendon and that of the greater terete muscle. The latissimus muscle draws the humerus downward and backward. In conjunction with the pectoral muscles, it is the chief agent in climb- ing and in walking with crutches. The Rhom/boid muscle 1 is situated beneath the trapezius muscle. It arises from the lower extremity of the nuchal ligament and the spinous processes of the upper four dorsal vertebra, and proceeds obliquely downward and outward to be inserted into the base of the scapula from its spine to its inferior angle. The muscle draws the scapula backward and upward. The fasciculus derived from the nuchal ligament is frequently more or less separated by a narrow interval from the lower portion of the muscle, leading to the usual division of the latter into the lesser and greater rhomboid muscles. 2 The Elevator of the Scap'ular angle 3 is situated at the side of the neck, and consists of a thick, fleshy bundle arising tendinously from the transverse processes of the upper four cervical vertebra, and descending to be inserted into the upper angle of the scapula. The Superior Ser'rated muscle 4 is situated beneath the rhomboid muscle. It arises by a thin aponeurosis from the lower part of the nu- chal ligament and the upper three dorsal spinous processes, and descends obliquely outward to be inserted, by angular serrations, into the upper border of the second, third, fourth, and fifth ribs, beyond their angle. A thin aponeurosis extends between this and the succeeding muscle, covering the extensors beneath. 1 M. rhomboideus ; m. cervici-dorso- gularis ; m. patientiae ; m. trachelo-scap- scapularis. ularis ; elevator muscle of the angle of 2 M. rhomboideus minor and major, or the scapula. superius and inferius. * M. serratus posticus superior; m. 3 M. levator scapulae; m. 1. anguli dorso-costalis ; m. cervici-dorso-costalis. scapulae; m. 1. proprius icapuloa ; m. an- 206 THE MUSCULAR SYSTEM. The Inferior Ser'rated muscle 1 is situated at the lower part of the back, beneath the latissinius muscle. It arises by a thin aponeurosis from the lower two dorsal and the upper three lumbar spinous processes, and ascends obliquely outward to be inserted by serrations into the lower border of the four inferior ribs. The two serrated muscles are antagonistic in their action. The supe- rior one aids in elevating the ribs, the inferior in depressing them, and thus both assist in respiration. DEEP MUSCLES OF THE BACK, OE EXTENSORS OF THE HEAD AND TRUNK. The extensor muscles, which maintain the erect position of the head and trunk, are situated at the back of the latter, and occupy the sides of the neck, the intervals between the angles of the ribs and spinous proc- esses of the vertebras, and the sides of the loins, extending into the angular intervals of the sacrum and hip bones. They lie beneath the trapezius, latissinius, rhomboid, and serrated muscles, and consist of numerous fleshy and tendinous fasciculi, which are more or less intimately connected, so that they may be described as com- paratively few or many distinct muscles. The Dor'sal Exten'sor 2 is a large muscle occupying the groove of the back at the side of the vertebral column. It is exceedingly complex in its arrangement, consisting of intermingled fleshy fasciculi and tendinous bands, and having many points of attachment to the vertebral column and ribs. Its lower portion is superficially composed of a strong apo- neurosis, from which many fleshy fasciculi have their origin. The muscle commences in a pointed manner upon the sacrum, is thickest in the loins, and gradually thins away on the thorax, from which, by accessory fasciculi, it is continued to the neck. It arises from the posterior surface of the sacrum, the posterior third of the crest of the ilium, and the spinous processes of the lumbar and lower two or three dorsal vertebrae, and in the vicinity of the last rib divides into two portions, named the longissimus and sacro-lumbar muscles. The Longis'simus muscle 3 is the internal and larger portion of the dorsal extensor. It is inserted into the transverse processes of the 1 M. serratus posticus inferior ; m. 3 M. longissimus dorsi ; m. semi-spi- lumbo-costalis; m. dorso-lumbo-costalis. natus; m. lumbo-dorso-trachelius ; in. 2 M. extensor dorsi, or trunci commu- extensor dorsi intcrnus. nis; m. erector spinse ; m. sacro-spinalis; m. lumbo-costalis; m. opistothenar. THE MUSCULAR SYSTEM. 207 lumbar and dorsal vertebrae, into the ends of the upper dorsal spinous processes, 1 into the ribs within the position of their angles ; and by accessory slips, derived from the upper dorsal transverse processes, is prolonged to the lower four or five cervical transverse processes. 2 The Sa'cro-lum/bar muscle, 3 in its ascent, receives accessory slips 4 from the upper border of the ribs, and is in- serted by a series of tendons into the angles of the ribs and into the four or five lower cer- vical transverse proc- esses. 5 EXTENSOR MUSCLES OF THE BACK. 1, 2, 3, 4, 5, 6, the dor- sal extensor muscle. 1, origin from the ilium, sacrum, lum- bar, and lower dorsal verte- brae ; 2, insertion into the ribs, named the sacro-lumbar mus- cle; 3, insertion, named the longissimus muscle ; 4, offset, named the dorsal spinal mus- cle ; 5, 6, prolongations to the neck, named the ascending and transverse cervical muscles ; 7, trachelo-mastoid muscle; 8, complex muscle; 9, prolonga- tion of the longissimus, named the transverse cervical muscle; 10, 11, semispinal muscle; 12, 13, smaller and larger straight muscles of the head ; 14, 15, su- perior and inferior oblique muscles ; 16, multifid-spinal muscle; 17, elevators of the ribs ; 18, inter-transverse mus- cles; 19, quadrate lumbar muscle. FIG. 155. The Sple'nius mus- cle 6 is situated at the back of the neck, beneath the trapezius muscle. ' It arises from the upper six dorsal spinous processes and the lower half of the nuchal ligament. Proceeding upward and outward, it divides into two portions, of which one 7 is inserted into the upper four cervical transverse processes, and the other 8 is inserted into the mastoid portion of the temporal bone and the con- tiguous part of the surface between the curved lines of the occipital bone. 1 M. spinalis dorsi. Usually described as distinct, ascending from the upper two lumbar and the three lower dorsal spinous processes, to the upper eight or nine dorsal spinous processes. 2 M. transversalis cervicis, orcolli; m. t. major colli, are names given to the portion prolonged to the neck. 3 M. sacro-lumbalis; m. sacro-costalis ; m. ilio-costalis; m. lumbo-costo-trache- lius ; m. extensor dorsi externus. * M. accessorii, or additamentum ad sacro-lumbalem. 5 M. cervicalis ascendens, or descend- ens Diemerbroeckii ; m. accessorius ad sacro-lumbalem ; m. transversalis colla- teralis colli, are names given to the por- tion prolonged into the neck. 6 Posterior mastoid muscle ; m. cervi- co-dorso-mastoideus. 7 M. splenius colli ; m. dorso-trachc- lius. 8 M. splenius capitis ; in. cervico-mas- toideus. 208 THE MUSCULAR SYSTEM. The Com'plex muscle, 1 partly concealed by the last, arises from the transverse processes of the upper four to six dorsal vertebrae and the transverse and articular processes of the lower four cervical vertebras, and ascends to be inserted into the inner part of the surface between the curved lines of the occipital bone. Its upper portion is partially inter- sected by a transverse tendinous structure ; and a large fasciculus of the muscle is divided into two bellies by an intermediate tendon. 2 The splenius and complex muscles of the two sides of the neck are important agents in maintaining the erect position of the head. The Tr ache lo-mas't old muscle, 3 situated between the upper end of the dorsal extensor and the complex muscle, is intimately connected with the former, and may with propriety be considered its prolongation to the head. It arises by narrow tendons from the roots of the transverse processes of the lower four cervical vertebrae, and ascends outwardly to be inserted into the mastoid process of the temporal bone beneath the sterno-mastoid and splenius muscles. The Semispi'nal muscle 4 consists of fleshy and tendinous fasciculi, obliquely extended between transverse and spinous processes in the back and neck, beneath the dorsal extensor and complex muscles. It arises from the dorsal transverse processes, except the one or two lower ones, and is inserted into the upper five dorsal spinous processes and the lower five of those of the neck. The upper and lower portions are sometimes separated by an interval, and these are usually described as distinct, with the names of semispinal muscle of the neck 5 and of the back. 6 The Mul'tifid spi'nal muscle,' partially concealed beneath the last, consists of numerous short, oblique fasciculi, extended from the trans- verse and articular processes to the contiguous spinous processes, from the sacrum to the axis. The fasciculi vary in length, some extending 3 M. coraplexus; ra. c. major; m. tra- 6 M. semispinalis dorsi, or externus : chelo-occipitalis ; m. dorso-trachelo-oc- m. transverso-spinalis dorsi ; m. semispi- cipitalis. natus dorsi. 2 This double-bellied fasciculus consti- ? M. multifidus spinrc : m. transveralis tutes the m. biventer cervicis. dorsi; m. transverso-spinalis; m. t. s. 3 M. trachelo-mastoideus ; m. complex- lumbarum dorsi et colli ; nv. spinales et us minor. transversales lumbarum; m. sacer; m. 4 M. semispinalis dorsi et colli. semispinalis internus et transverso-spi- 5 M. semispinalis colli, or cervicis; m. nalis colli pars interna ; m. lumbo-dorsi- spinalis, or transversalis colli, or cervi- spinalis ; lumbo-cervical portion of the cis; m. transverse- or articulo-spinalis spinal muscle; in part, the musculi ro- colli ; m. semispinatus colli. tatores spinae. THE MUSCULAR SYSTEM. 209 between two vertebrae, others between three, and a few between four, or even five. This and the preceding muscles are extensors of the vertebral column. The Inter-spi'nal muscles 1 consist of short, fleshy bundles, situated in pairs between the contiguous spinous processes of the vertebrae. They are best developed in the neck, and usually are obsolete in the dorsal region. The Inter-trans 'verse muscles 2 consist of short, fleshy bundles, occu- pying the intervals of the contiguous transverse processes. They are best developed in the neck, where they are double, are rudimental in the dorsal region, and are well marked in the loins. These and the preceding small muscles aid in the extension of the ver- tebral column. The Larger Straight muscle 3 arises tendinously from the spinous process of the axis, and ascends to be inserted into the inferior curved line of the occipital bone. The Smaller Straight muscle 4 arises from the rudimental spinous process of the atlas, and is inserted into the occipital bone below its inferior curved line. The Lateral Straight muscle 5 arises from the transverse process of the atlas, and is inserted into a ridge of the corresponding process of the occipital bone. The Superior Oblique muscle 6 arises from the extremity of the trans- verse process of the atlas, and ascends obliquely inward to be inserted into the outer part of the surface between the curved lines of the occip- ital bone. The Inferior Oblique muscle 7 arises from the spinous process of the 1 M. interspinales ; m. i. colli, dorsi et 5 M. rectus lateralis ; m. rectus capi- lumbarum. tis lateralis ; m. lateralis Fallopii ; m. 2 M. intertransversarii. transversalis anticus primus; m. trache- 3 M. rectus major; m. rectus capitis lo-atloido-basilaris ; m. atloido-subocci- posticus major; m. axoido-occipitalis ; pitalis. m. spini-axoido-occipitalis ; larger pos- 6 M. obliquus capitis superior, or mi- terior straight muscle. nor; m. atlo-, post-, or submastoideus; 4 M. rectus minor; m. r. c. p. minor; m. trachelo-atloido-occipitalis. m. atlo-occipitalis ; m. tuber-atloido-oc- 7 M. o. c. inferior, or major ; m. axo- cipitalis; smaller posterior straight mus- atloideus ; m. spini-axoido-tracheli-atloi- cle. deus. 14 210 THE MUSCULAR SYSTEM. axis, and passes obliquely outward and upward to be inserted into the extremity of the transverse process of the atlas. The straight and oblique muscles contribute to maintain the erect con- dition of the head. The inferior oblique and larger straight muscles rotate the latter, together with the atlas upon the axis. MUSCLES OF THE RIBS. The Intercostal muscles, of which there are eleven pairs on each side of the thorax, occupy the intervals of the ribs. They consist of two planes of short, fleshy and tendinous fibres, extended between the contiguous borders of the ribs and costal cartilages. The External Intercostal muscles 1 commence at the tubercles of the ribs, and, with their fibres directed obliquely downward and forward, advance to the costal cartilages, between which they terminate in a thin aponeurosis. The Internal Intercostal muscles 2 commence at the sternal ends of the costal cartilages, and, with their fibres directed obliquely downward and backward, crossing the course of those of the preceding muscles, proceed to the angles of the ribs, where they terminate in a thin aponeu- rosis, extending to the vertebra?. On the inner surface of the ribs, more or less frequently, a variable number of fasciculi of fibres of the internal intercostals extend over two or even three intercostal spaces. 3 Between the intercostal muscles the intercostal blood-vessels and nerves pursue their course. The internal intercostal muscles are in con- tact with the pleura ; the external ones with the pectoral and great ser- rated muscles. The Ster'no-cos'tal muscle, 4 variable in its extent and attachments, is situated within the front of the thorax. It arises by a thin aponeurosis from the inner surface of the lower two divisions of the sternum and the contiguous ends of the costal cartilages, whence its fibres diverge upward and outward, to be inserted by digitations into the costal cartilages from the fifth to the second inclusively. The Cos'tal El'evators 5 are twelve in number, on each side of the thorax, and lie beneath the extensor muscles of the back. They con- 1 M. intercostales externi. * M. sterno-costalis ; m. triangularis 2 M. intercostales interni ; m. inter- sterni ; m. pectoralis internus. pleuro-costales. 5 Elevator muscles of the ribs; m. le- 3 M. infracostales; m. subcostales. vatores costarum breviores et longiores ; m supra-costales. THE MUSCULAR SYSTEM. 211 sist of narrow bundles arising tendinously from the ends of the trans- verse processes of the last cervical and all the dorsal vertebrae, except the last one. Descending obliquely outward, their fibres diverge to be inserted into the contiguous ribs, between their tubercles and angles. The lower muscles of the series send an additional fasciculus to the second ribs below their origin. The intercostal muscles act together, and either raise or depress the ribs according as the first or last of the series of the latter becomes the more fixed point of action. Thus, if the scalene muscles draw up the first and second ribs, this will determine the intercostals to raise all the ribs. If, on the other hand, the quadrate lumbar muscles draw down the last ribs, then all the others will be depressed by the intercostals. The costal elevators, as expressed by their name, and the superior serrated muscles, raise the ribs. The sterno-costal and inferior serrated muscles depress the ribs. From the above, it will have been perceived that all the muscles men- tioned concur in promoting the function of respiration. THE ABDOMEN. The Abdo'men or belly 1 is that part of the trunk which is included between the thorax and pelvis. The large vacuity observed in the skeleton between the inferior mar- gin of the thorax and the superior border of the pelvis, is closed by the soft, extensible abdom/inal pari'etes or walls, composed of skin, the superficial fascia, six pairs of muscles, the transverse fascia, and the peritoneum. The abdominal parietes are longest anteriorly, and become gradually shortened as they approach the back part, named the loins or lumbar regions, 2 situated on each side of the vertebral column. In the upright position the abdominal walls are convex and protuberant, vary- ing in these respects according to the fatness of the individual. In the recumbent position they sink inwardly, and in very lean persons even the vertebral column may be felt through them! Inspiration increases their protuberance, and expiration their depression. In vigorous men, the outlines of the muscular bellies of the abdominal parietes are visible through the skin. In fat persons, usually including healthy women, these are obscured by the subcutaneous fat. Over the position of the end of the sternum is a depression called the pit of the 1 Venter; gaster; abdomen; alvus ; venter imus, or infimus ; epischion; hypo- gastrion; hypocrelium; hypoutrion ; hypochoilion; etron; nedys; neira; physce. * Lumbi; lendis; psoae; reins. 212 THE MUSCULAR SYSTEM. stomach, 1 which becomes more evident with an increase of fat. Near the centre of the abdomen, in front, is the umbilicus or navel, 2 which is a cicatrix remaining from the connection of the umbilical cord of the foetus. From the close adhesion of the skin to the umbilicus, its depth increases with the accumulation of fat around. The lower part of the abdominal walls is defined on each side by the prominence corresponding with the crest of the ilium and named the hip ; and in advance of this by the groin and prominence of the pubes. The groin or in'guinal region 3 corresponds with the crease descend- ing from the hip to the pubis and separating the abdomen from the front of the thigh. The skin of the abdomen is rather thin and moderately extensible ; in lean persons is readily elevated into folds, but not in fat persons. Its extensibility is not so great as might be supposed from the frequent occurrence of distention of the abdominal walls from the accumulation of fat, pregnancy, dropsy, or other causes. In such cases partial rup- tures of the dermis take place; and even after the distention is removed, the position of these ruptures is indicated by their cicatrix-like marks on the skin. SUPERFICIAL FASCIA OF THE ABDOMEN. The Superficial Fascia 4 is well developed, especially toward the lower part of the abdomen, where it is observed to consist of two distinct layers. It is continuous above with the superficial fascia of the thorax, and behind with that of the back. Its two layers, blended together, adhere along the median line of the abdomen, along the crest of the ilium, and Poupart's ligament, and become continuous with the super- ficial fascia of the thigh, that of the spermatic cord, and the penis. Where the two layers are separable, the subcutaneous one is found to be composed of loose areolar tissue containing more or less fat, which increases in descending toward the pubis. At the umbilicus it never contains fat, so that the fatter the individual the more depressed the umbilicus will appear. The deeper layer is thinner and more membran- ous in its character than the other, and is not disposed to the develop- ment of fat in its interstices. Between the two layers are contained the subcutaneous blood-vessels, among which, the superficial epigastric artery and vein are conspicuously observed ascending obliquely from the groin. 1 Scrobiculus cordis. 3 Inguen ; plica inguinalis ; bubo. 2 Umbilic ; umbo ; omphalos ; mesom- * Fascia superfacialis abdominis. phalium; radix, or medium ventris. THE MUSCULAR SYSTEM. 213 MUSCLES OF THE ABDOMEN. The front and lateral walls of the abdomen are composed of six pairs of muscles, of which three are broad muscles, and the others are long ones. The External Oblique muscle, 1 the stoutest of the three broad ab- dominal muscles, consists of a fleshy portion occupying the side of the abdomen, and a strong aponeurotic portion extending over the front of the latter. It arises by angular digitations from the outer surface of the lower eight ribs ; the digitations being received between similar processes of the origin of the great serrated and latissimus muscles. The fleshy fas- ciculi incline downward and inward, the lowest ones being inserted into the crest of the ilium, while the others terminate in an aponeurosis, which extends to the median line of the abdomen, from the sternum to the pubis, and conjoins with that of the opposite side. The upper three-fourths of the aponeurosis present the appearance of a broad band at the side of the median line of the abdomen ; and its lower fourth widens outward to the anterior superior spinous process of the ilium. Though mainly composed of fibres continuing in the direc- tion of the fleshy fasciculi, it nevertheless contains many crossing ones, apparently derived from the aponeurosis of the opposite muscle. In several positions the fibres by their separation leave small square inter- vals, through which blood-vessels reach the superficial fascia and integu- ment. The upper part of the aponeurosis is connected with the origin of the great pectoral muscle, and is attached to the third piece of the sternum. As the aponeurosis approaches the pubis its fibres diverge, leaving between them a triangular interval, the external abdom/inal ring, 2 which gives passage to the spermatic cord of the male, and the round ligament of the uterus of the female. The direction of the ring is obliquely downward and inward ; its base being formed by the body 3 of the pubis, and its sides or columns 4 by the diverging fibres of the aponeurosis. The inner or upper column is attached in front of the pubic symphysis, and interlaces with the corresponding insertion of the opposite muscle. The outer or lower column is formed by the inferior and somewhat thick- 1 M. obliquus abdominis externus, de- 2 Abdominal ring ; annulus abdorai- scendens, or major; m. costo-abdomi- nis, or inguinalis ; inguinal ring, nalis ; m. ilio-pubo-costo-abdominalis. 3 Crest of the pubis. 4 Pillars ; crura. 214 THE MUSCULAR SYSTEM. ened fibres of the aponeurosis, extended between the anterior superior spinous process of the ilium and the spine of the pubis, constituting the so-called Poupart's ligament 1 or femoral arch, 2 important in its relations with inguinal and femoral herniae FIG. 15H. MUSCLES OF THE FRONT OF THE TRUNK; on the left side are seen the superficial muscles, on the right the deeper ones. 1, great pectoral; 2, deltoid; 3, latissimus ; 4, great serrated; 5, subclavian ; 6, small pec- toral; 7, coraco-brachial; 8, biceps flexor muscle; 9, coracoid process; 10, great serrated muscle; 11, inter- costals; 12, external oblique; 13, its aponeurosis; 14, Poupart's ligament; 15, external abdominal ring; the figure rests upon the falciform process of the fascia of the thigh bounding the saphenous opening exter- nally; 16, straight muscle of the right side, exposed by removing the front of its sheath, which remains on the left side; 17, pyramidal muscle; 18, internal oblique; 19, conjoined tendon of the internal oblique and transverse muscles; 20, position of the inguinal canal below the arching edges of the muscles just named. Above the position of the external abdominal ring, transversely cross- ing fibres proceed from the line of Poupart's ligament toward the median line of the abdomen, apparently with the object of preventing a greater separation of the columns of the ring. From the edges of the latter, a Ligament of Fallopius. Crural, or inguinal arch. THE MUSCULAR SYSTEM. 215 thin layer of connective tissue 1 is prolonged upon the spermatic cord, or round ligament. Poupart's ligament in its course makes a curve with the convexity downward, and is somewhat inflected or directed inwardly. Below, it is continuous with the femoral fascia. At its insertion, a process of the same structure extends a short distance along the pectineal line of the pubis, and terminates in a crescentic margin, constituting the so-called Gimbernat's ligament, 2 important in its relations with femoral hernia. The Internal Oblique muscle 3 is placed beneath the last, and, like it, is fleshy at the side of the abdomen, and aponeurotic in front. It arises from the outer half of Poupart's ligament, the crest of the ilium, and the lumbar fascia. From this origin the fleshy fasciculi radiate forward, the more posterior ascending obliquely and becoming attached to the margin of the lower four costal cartilages contiguous to their internal intercostal muscles, while the others terminate in an apo- neurosis extending from the sternum to the pubis. At its upper extrem- ity the aponeurosis is attached to the end of the sternum and the seventh and eighth costal cartilages. For three-fourths of its extent it splits at the semilunar line into two laminaB, of which one proceeds in front of the straight muscle and identifies itself with the aponeurosis of the external oblique muscle, while the other proceeds behind the straight muscle, and in like manner identifies itself with the aponeurosis of the transverse muscle. The lower fourth of the aponeurosis passes without division in front of the straight muscle. The inferior fibres of the internal oblique muscle arch forward and downward over the course of the spermatic cord, or round ligament of the uterus, and, in conjunction with corresponding fibres of the trans- verse muscle, form the conjoined tendon, 4 which is inserted into the body and pectineal line of the pubis, within the position of the external ab- dominal ring, thus affording a protection against the escape of any por- tion of the bowels through this aperture. The Transverse muscle 5 lies beneath the preceding muscles, and like them presents the same relation of fleshy and aponeurotic portions. It arises from the outer half of Poupart's ligament, the crest of the ilium, the lumbar fascia, and the inner surface of the lower six costal 1 Intercolumnar fascia ; fascia sperma- m. ilio-lumbo-costo-abdominalis ; m. ac- tica. clivis. 2 Hey's ligament. * Superficies intercruralis. 3 M. obliquus abdotninus interims, as- 5 M. transversalis abdominis; m. lum- cendens, or minor; m. ilio-abdominalis ; bo-abdominalis. 216 THE MUSCULAR SYSTEM. FIG. 157. cartilages, where it indigitates with the origin of the diaphragm. The fleshy fasciculi, as indicated by the name of the muscle, proceed trans- versely forward and terminate in an aponeurosis, of which the upper three-fourths join the posterior lam- ina of the aponeurosis of the in- ternal oblique muscle, and with it proceed to the median line of the abdomen, while the lower fourth passes in front of the straight muscle, and, in conjunction with the corres- ponding portion of the aponeuroses of the other broad muscles, likewise proceeds to the median line of the abdomen. The inferior fibres of the trans- verse muscle, like those of the in- ternal oblique, arch forward and downward to the conjoined tendon. Internally this muscle is invested with a thin, fibrous membrane, the transverse fascia, 1 which attaches it to the peritoneum. VIEW OF THE LEFT SIDE OF THE ABDOMEN. 1, por- tion of the latissimus muscle ; 2, origin of the great serrated muscle ; 3, origin of the external oblique ; 4, external intercostals ; 5, internal intercostals ; 6, transverse muscle ; 7, its aponeurotic origin ; 8, its aponeurotie insertion ; 9, lower part of the internal oblique muscle ; 10, straight muscle of the right side; 11, position of the inguinal canal between the arched border of the internal oblique and trans- verse muscles and Poupart's ligament ; the figure rests on the transverse fascia ; 12, the gluteal mus- cles. The Straight muscle 2 is a broad, fleshy band, situated at the side of the median line of the abdomen, and extending from the pubis to the front of the thorax. It arises by a flat tendon from the symphysis and body of the pubis, expands gradually to the breadth of three or four inches, and ascends to be inserted in front of the fifth, sixth, and seventh costal cartilages. In its course it presents three or four short tendinous intersections, 3 which ex- tend through the breadth and thickness of the muscle, and adhere tightly to the aponeurosis covering the latter. These tendinous intersections appear to represent the abdominal ribs of lizards. The straight muscle is 'inclosed in a sheath, 4 formed by the aponeu- 1 Fascia transversalis. 2 M. rectus abdominis ; m. pubio-sternalis. 3 Inscriptiones tendinese. 4 Vagina musculi recti. THE MUSCULAR SYSTEM. 217 roses of the broad muscles, which is incomplete, however, at its lower fourth posteriorly, where the muscle is in contact with the transverse fascia. The deficiency in the sheath is more or less defined by a thin, lunated edge, 1 which is confluent with the transverse fascia extending toward the pubis. In consequence of the deficiency in the aponeurotic sheath of the straight muscle a space is left, recently described 2 as the preperitone'al cavity, 3 which accommodates the urinary bladder in a distended con- dition. The Pyram'idal muscle* is situated beneath the aponeuroses of the broad muscles upon the lower extremity of the straight muscle. It arises from the symphysis and body of the pubis, and ascends one-third the distance toward the umbilicus, to be inserted into the median line of the abdomen. This muscle sometimes exists only on one side, and not unfrequently it is altogether absent. At the median line of the abdomen, the aponeuroses of the three pairs of broad muscles are intimately associated with one another, the tendin- ous fibres of one side crossing and intersecting those of the opposite side. From its white appearance, rendered more conspicuous by the dark color of the straight muscle being seen through the aponeurosis on each side, it is named the linea alba. 5 This is wide above but narrow below, and separates the straight muscles. Near its middle the umbilicus ap- pears as a fibrous cicatrix. The aponeuroses of the broad muscles commence nearly in the same position, corresponding with the outer border of the straight muscles. This position also appears as a white line, in contrast with the fleshy bellies on each side, and is named, from its curving inwardly as it ap- proaches the pubis, the semilunar line. 6 Crossing from the semilunar to the median line, the tendinous intersec- tions of the straight muscle are seen through the aponeurosis investing the latter, and are named, from their course, the transverse lines. 7 One of these exists nearly opposite the lower end of the sternum, a second about half the distance from this to the umbilicus, a third nearly on a level with the latter, and usually an imperfect one half way between the umbilicus and pubis. They intimately adhere to the aponeurosis in front 1 Linea semicircularis ; linea Dou- * M. pyramidalis abdominis ; m. pu- glasii ; plica semilunaris Douglasii. bio-umbilicalis ; m. Fallopii ; m. succen- 2 Sitzungsberichte der K. Akad. der turiatus*; m. auxiliarius. Wissenschaften. Wien, 1858, page 259. * L. centralis ; 1. candidula. 3 Cavum prseperitoneale ; c. p. Retzii; 6 L. semilunaris. porta vesicae ; p. v. Retzii. * L. transversse. 218 THE MUSCULAR SYSTEM. of the straight muscle, and, in powerfully muscular men, together with the median and semilunar lines, indicate the position of the intervening fleshy bellies, even through the tegumentary covering of the abdomen. The Quad'rate Lum'bar muscle 1 is situated at the side of the lumbar vertebrae, and is inclosed in a sheath formed by the lumbar fascia. It arises tendinously from the crest of the ilium back of its middle, and ascends to be inserted into the last rib and the transverse processes of the lumbar vertebrae, except the last one. The muscles of the abdomen support and compress the viscera of its cavity. By depressing the ribs and elevating the abdominal viscera, they antagonize the action of the diaphragm, and thus become the prin- cipal muscles in expiration. They act also in the expulsion of the con- tents of the bowels and urinary bladder, in the birth of the child, in vomiting, etc. THE LUMBAR FASCIA. The Lum/bar fas'cia 2 consists of two fibrous layers inclosing the quadrate lumbar muscle, and forming part of the origin of the internal oblique, transverse, and latissimus muscles. The anterior layer is at- tached to the front of the roots of the transverse processes of the lumbar vertebrae, the crest of the ilium, and the last rib ; in which latter position its thickened margin constitutes the external arc'uate ligament. 3 The posterior layer, thicker and more aponeurotic than the other, is attached to the ends of the transverse processes of the lumbar vertebrae, the crest of the ilium, and the last rib. It separates the quadrate lumbar muscle from the dorsal extensor, and is joined at the outer border of the former by the anterior layer, in which position it gives origin to the muscles above mentioned. THE TRANSVERSE FASCIA OF THE ABDOMEN. The Transverse fascia 4 of the abdomen is a thin, fibrous membrane investing the inner surface of the transverse muscles, and attaching them to the peritoneum. It is strongest in the inguinal region, and in this position is important in its relations with hernia. It invests the straight muscle where its sheath is incomplete, and closely adheres to the lunated margin of the latter, as it does also to the body and pectineal line of the pubis, behind the tendon of the straight muscle and the conjoined tendon 1 M. quadratus lumborum, or dorsi ; 2 F. lumborum. m. lumbaris externus; m flectans par 3 L. arcuatura externum. lumborum; m. ilio-costalis ; m. ilio- 4 F. transversa; f. transversnlis ; f. lumbo-costalis. Coopcri; f. endogastrica. THE MUSCULAR SYSTEM. 219 of the internal oblique and transverse muscles. Traced upward, it becomes thinner, and is continuous with the fibrous attachment of the peritoneum to the diaphragm. Traced toward the loins, it becomes thinner and looser in texture. It tightly adheres to the crest of the ilium and Poupart's ligament, and from these positions is continuous with the iliac fascia. Half way between the anterior superior spinous process of the ilium and the symphysis of the pubis, just above Poupart's ligament, the trans- verse fascia is prolonged downward and inward as a sheath 1 to the sper- matic cord. The entrance of this prolongation, viewed as an orifice, is named the internal abdom'inal ring, the commencement of the inguinal canal. THE INGUINAL CANAL. The In'guinal canal 2 is the space in the lower part of the abdominal walls whicfh gives passage to the spermatic cord of the male, and the round ligament of the uterus in the female. It is narrower in the latter, in accordance with the smaller size of the round ligament than the spermatic cord. FIG. 158. VIEW OF THE INGUINAL CAXAL. 1, por- tion of the fleshy belly of the external ob- lique muscle; 2, its aponeurosis; 3, por- tion of the latter raised up, exposing the inguinal canal; 4, linea alba; 5, insertion of the aponeurosis of the external oblique into the body of the pubis; 6, its insertion into the spine of the pubis, named Pou- part's ligament; 7, division of the fibres of the aponeurosis crossed by transverse fibres; 8, external abdominal ring, the ter- mination of the inguinal canal ; 9, anterior superior spinous process, the origin of Poupart's ligament ; 10, arching lower bor- der of the internal oblique and transverse muscles; 11, conjoined tendon of the latter muscles ; 12, fibres of the cremaster muscle descending on the spermatic cord from the edges of the muscles just named ; 13, rests on the transverse fascia; to its right are the epigastric vessels crossing the course of the inguinal canal; 14, iliac portion of the femoral fascia ; 15, pubic portion ; 16, falciform proces's; 17, saphenous opening; 18, saphenous vein joining the femoral vein through the saphenous opening; 19, the femoral artery and vein exposed by raising the portion of fascia which forms the falciform process; 20, suspensory ligament of the penis. The canal is about an inch and a half long ; its upper extremity being the internal abdominal ring, 3 and its lower extremity the external 1 Infundibuliform fascia ; fascia sper- matica interna, or propria. 2 Canalis inguinalis ; spermatic canal. 3 Apertura interna; a. abdominalis. 220 THE MUSCULAR SYSTEM. abdom/inal ring. 1 In front it is bounded by the aponeurosis of the external oblique muscle, behind by the transverse fascia and conjoined tendon of the internal oblique and transverse muscles, above by the arching borders of the latter muscles, and below by Poupart's ligament. The middle of the inguinal canal is crossed behind by the epigastric blood-vessels, which pursue their course, involved in the structure of the transverse fascia, from the external iliac blood vessels, upward and in- ward toward the umbilicus. The interior surface of the abdominal wall, in the inguinal region, presents a slight fold of peritoneum pursuing the same course as the epi- gastric blood-vessels, and hence called the epigas'tric fold. 2 The fold divides the inguinal region into two shallow depressions named the internal and external in'gninal fossae. 3 The deeper part of the internal in'guinal fossa 4 corresponds with the position of the external abdominal ring, and is the point at which direct inguinal hernia occurs. The deeper part of the external hi/gninal fossa corresponds with the position of the internal abdominal ring, into which the peritoneum is sometimes prolonged, especially in the female, as a small funnel-like pit; 5 and at this point oblique inguinal hernia has its commencement. REMARKS ON INGUINAL HERNIA. The protrusion of any portion of the contents of the abdomen through an opening in its parietes is called a her'nia ; the varieties of which are named from the particular positions of their occurrence, and thus we have umbilical hernia, inguinal hernia, femoral hernia, and others. The pro- truding part pushes before it the membranous structures it meets in its passage, and these furnish coverings to the hernia. The peritoneum, which is the membrane first protruded, forms the so-called her'nial sac. An inguinal hernia may occur either from the internal or the external inguinal fossa. Most frequent from the latter position, it follows the course of the inguinal canal, and emerges at the external abdominal ring, anfl receives the name of oblique in'guinal her'nia, In this variety the hernial sac has for its coverings, in the order of their protrusion : first, a membrane, more or less distinct, formed by the association of the trans- verse and intercolumnar fascia, including the fibres of the cremaster muscle ; second, the superficial fascia ; and third, the skin. 1 Annulus inguinalis ; apertura externa. 4 Triangle of Hesselbach. 2 Plica epigastrica. 5 Canal of Nuck. 3 Foveae inguinales. THE MUSCULAR SYSTEM. 221 The protrusion of a hernia directly through the external abdominal ring occurs from the internal inguinal fossa, and receives the name of direct in/guinal hernia. 1 The coverings of the hernial sac in this variety, in the order of protrusion, are: first, a membranous investment, derived from the transverse fascia and the intercolumnar fascia, including some loose fibres of the conjoined tendon ; second, the superficial fascia ; and, third, the skin. If the protrusion occurs through a separation or interval of the fibres of the conjoined tendon, this structure would not contribute to form the first covering of the hernial sac. In consequence of the comparative narrowness of the inguinal canal and smallness of the abdominal rings, inguinal hernia is of rare' occur- rence in the female. In oblique inguinal hernia, the excretory duct of the testicle and ves- sels of the spermatic cord and the epigastric blood-vessels lie at the inner side of the neck of the hernia ; but in direct inguinal hernia, the sper- matic cord and epigastric vessels are at the outer side. THE DIAPHRAGM. The Di'aphragm 2 is a muscular partition separating the thorax and abdomen. Its under or abdominal surface is deeply vaulted, and is invested by the peritoneum ; its upper surface is convex, and is covered by the two pleura3 and the pericardium. Its centre rises to a level with the fifth costal cartilages ; and on the right side, apparently to accom- modate the liver, it rises higher than upon the left. The origin of the diaphragm is from the inferior margin of the thorax as constituted by the end of the sternum and the lower six ribs, from the arcuate ligaments, and from the bodies of the upper four lumbar verte- bra. From this extensive circle the fleshy fasciculi ascend and converge to a central tendon. The origin from the ribs is by fleshy serrations included between similar processes of the transverse muscles of the abdomen. The arc'uate ligaments 3 are thin and narrow fibrous arches, of which the inner one extends over the upper extremity of the psoas muscle from the body of the first lumbar vertebra to its transverse process ; the outer one forms the upper edge of the anterior layer of the lumbar fascia, 1 Internal inguinal hernia ; ventro-in- phrenes ; praecordia ; praecinctus ; suc- guinal hernia. Centura; muse, succinctus; septum 2 Diaphragma ; musculus phrenicus ; transversum ; respiratoriura ventris. midriff ; diaphraxis ; disseptum ; discre- 3 Ligamenta arcuata. torium ; hypozoma; perizoma; diazomo; 900 THE MUSCULAR SYSTEM. FIG. 159. extended from the transverse process of the first lumbar vertebra to the end of the last rib. The portions of the diaphragm proceeding from the lumbar vertebra? are named its crura. 1 The right crus is the larger, and arises tendinously from the bodies and in- tervening fibro-cartilages of the upper four lumbar vertebraB ; the left cms arises in the same manner from the upper three. The central tendon 2 of the diaphragm is a broad aponeurosis, composed of converging and inter- woven fibrous bands, and is entirely surrounded by the fleshy part of the muscle. It is usually de- TNFERIOR VIEW OF THE DIAPHRAGM. 1, 2, 3, the three lobes of the scribed as SOmewhlt heart central tendon, surrounded by the fleshy fasciculi derived from the inferior margin of the thorax, the crura, 4, 5, and the arcuate Shaped, With the notch di- ligaments, 6, 7 ; 8, aortic orifice; 9, oesophageal orifice ; 10, quad- rected backward Or more rate foramen ; 11, psoas muscle ; 12, quadrate lumbar muscle. correctly as trilobed, one lobe being directed forward, and one backward on each side. Three important orifices exist in the diaphragm for the passage of the aorta, oesophagus, and inferior cava. The aort'ic orifice 3 is formed between the crura of the diaphragm in front of the first lumbar vertebra. The tendons of origin of the crura meet behind the aorta, and conjoin in a narrow arch in front of it, so that the vessel is inclosed by fibrous structure and is not liable to constriction from the action of the fleshy portion of the muscle. Besides the aorta, the thoracic duct passes through the aortic orifice of the diaphragm. The cesophage'al orifice 4 is an elliptical opening, situated above and a little to the left of the aortic orifice, in the muscular structure of the diaphragm. In the ascent of the crura of the latter, their fleshy fasci- culi cross in front of the aortic orifice, and then, proceeding upward to 1 Pillars ; columns ; pars lumbalis. 2 Centrum tendineum, phrenicum, or nerveum; pars tendinea; tendo dia- phragmatis; speculum Helmontii ; cordi- form tendon; phrenic centre. 3 Hiatus aorticus; semicirculus ex- culptus. * (Esophageal aperture or foramen ; for. 03sophageum. THE MUSCULAR SYSTEM. 223 reach the central tendon, leave between them the cesophageal orifice. The fleshy constitution of the borders of this aperture adapts it to act the part of a sphincter muscle to the oesophagus. The remaining orifice, which transmits the ascending cava, is situated in the central tendon, to the right of its middle. Formed between the crossing fibrous bands of the tendon, it is somewhat square, with rounded angles, and hence is named the quad/rate foramen. 1 Besides the orifices described, the crura of the diaphragm are pierced by the great sympathetic nerves and azygos veins. The diaphragm is the most important of the respiratory muscles. In contracting it descends, and thus increases the capacity of the chest, and produces inspiration. The abdominal muscles are the chief antagonists to its action. It performs an important part in coughing, laughing, sneezing, yawning, sighing, crying, sobbing, hiccoughing, singing, vomit- ing, the voiding of the excrement, and the expulsion of the foetus. MUSCLES OF THE PERINEUM. See the article Perineum, after the account of the generative appa- ratus. THE UPPER EXTREMITY. The Tipper Extremity commences with the prominence of the shoulder, beneath which is the axil'la 2 or armpit, bounded in front and behind by thick borders, the ax'illary folds. The arm 3 is cylindrical, and terminates in the bend of the arm or elbow, which is bounded on each side by the prominences of the condyles, and behind by the prominence of the ole- cranon, the elbow. The forearm* is club shaped, and compressed from within outwardly. Its prominent inner portion above is produced by the flexor and pronator muscles ; its corresponding outer portion, by the extensor and supinator muscles. The back or dorsal surface of the hand is broad and convex, and presents no indication of the separation existing between the carpus and metacarpus. The palm or palmar sur- face exhibits the hollow of the hand, bounded above by the prominence of the carpus or wrist, and at the sides by the ball of the thumb 5 and little finger. 5 The wrist joint, or radio-carpal articulation, is indicated in front by transverse furrows of the skin. The metacarpo-phalangial articulations are indicated by the knuckles behind, and transverse furrows at the ante- 1 F. quadratum; f. venosum. 3 Brachium. 2 Assella; fovea axillaris; cordis * Antibrachium ; pars inferior brachii ; emunctorium; hypomin ; male; mas- cubitus. chalis. 5 Thenar and liypothenar eminences. 224 THE MUSCULAR SYSTEM. rior third of the palm. The phalangial articulations are likewise indi- cated by knuckles, and by transverse furrows of the skin before and behind. The fingers, as previously mentioned, are named in succession, the thumb, 1 the index or fore finger, 2 the middle, 3 the ring, 4 and the little fingers. 5 The skin of the upper extremity is moderately thick and dense exter- nally or posteriorly ; thin and extensible internally or anteriorly. It is readily movable to and fro on the parts beneath, except in the palm of the hand. FASCIAE OF THE UPPER EXTREMITY. The Superficial fascia of the upper extremity is a rather loose layer of areolar tissue connecting the skin with the deep fascia and with the various subcutaneous prominences and ridges of the bones. Its super- ficial portion contains more or less fat, the superficial venous trunks, and the cutaneous nerves in their course to the skin. Accumulation of fat involves the veins just mentioned, and, occupying the angular intervals of the different groups of muscles, gives the characteristic rounded form to the limbs of young children, well-developed women, and fat men. The deeper portion of the fascia is more membranous in character, and defines the fatty layer from the parts beneath. Upon the acromion and olecranon the superficial fascia is always devoid of fat; and in the latter position it contains an irregular synovial bursa, devoid of an epithelium. Approaching the wrist and hand, the fatty layer of the superficial fascia decreases, but is never absent from the palm of the hand, where it is intimately blended with the under surface of the skin. The Deep fascia 6 of the upper extremity is a continuation of the thin membrane investing the pectoral, trapezius, latissimus, and great serrated muscles. Adhering to the clavicle, acromion, and spine of the scapula, it gives the deltoid muscle a thin covering, and extends downward upon the arm. A portion invests the subscapular and terete muscles ; but stronger portions cover the supra- and infra-spinous muscles, adhering intimately to the borders of the fossae whence the muscles arise. It incloses the axilla by crossing from the pectoral to the latissimus muscle, and it is intimately associated with the sheath of the axillary and brachial vessels and nerves. It is thin upon the inner part of the arm, is thicker on the back part, and increases in strength as it approaches the elbow, 1 Pollex. * D. annularis. 2 Digitus indicis. 5 D. minimus. 3 D. medius. 6 Brachial and antebrachial fascia. THE MUSCULAR SYSTEM. 225 where it adheres to the olecranon, the condyles, and the condyloid ridges, the attachments to the latter constituting intermuscular parti- tions. It receives offsets from the tendons of insertion of the pectoral, latissimus, and triceps muscles, and also gives origin to some of the fleshy fasciculi of the latter. In the forearm the deep fascia has an aponeurotic appearance; is bluish white, and shining, and is composed of transverse fibres conjoined by others running longitudinally. From the tendon of the biceps it receives a conspicuous offset, which expands upon the muscles arising from the internal condyle, and separates the median basilic vein from the brachial vessels and median nerve. Extensions of the fascia inwardly l>etween the muscles constitute intermuscular partitions, which, together with the inner surface of the fascia afford origin to many of the fleshy fasciculi of the muscles. At the wrist, by strong accessions of transverse fibres, the deep fascia forms the annular ligaments, which serve to maintain the position of the flexor tendons in their course to the hand. The Anterior an'nular ligament 1 is a strong, thick, and wide band extended from the inner to the outer side of the front of the carpus, being attached by one extremity to the pisiform and unciform bones, by the other to the trapezial and scaphoid bones. With the concavity of the carpus it forms a canal for the passage of the flexor tendons and median nerve to the palm of the hand. The Posterior an'nular ligament, 2 less distinct and strong than the preceding, is a wide band of oblique fibres extended from the outer border of the lower end of the radius to the inner side of the ulna and the pisiform bone. As it crosses the radius and ulna, it tightly adheres to the parallel ridges at their lower ends, thus converting the intermediate grooves into canals, through which the extensor tendons pass to the back of the hand. The deep fascia on the back of the hand extends as a thin layer from the ligament just described to the fingers, and is intimately connected with the extensor tendons beneath. The palmar fascia 3 extends from the annular ligament, as a thin investment to the ball of the thumb and little finger. The middle portion is a strong, triangular aponeurosis, composed of fibres diverging from the annular ligament and connected by transverse fibres. Its apex partly receives the insertion of the tendon of the long palmar muscle ; its base divides into four processes, each of which subdivides upon the flexor tendons as these diverge to the fingers, 1 L. annulare, or transversum anterius ; 1. commune, or carpi volare. 2 L. annulare, or transversum posterius ; 1. commune, or carpi dorsale. 3 Aponeurosis palmaris. 15 226 THE MUSCULAR SYSTEM. FIG. 160. and the subdivisions are attached to the vaginal ligaments and those of the metacarpo-phalangial articulations. The Vag'inal ligaments 1 are fibrous sheaths, inclosing the flexor ten- dons, in front of the phalanges, with the lateral edges of which they are firmly attached. They are composed of transverse and obliquely cross- ing bands, thick and strong in front of the phalanges, but thin upon the articulations, so as not to impede the movement of the latter. The tendons of the flexor and extensor muscles, as they pass through the canals formed by the annular and vaginal ligaments, are invested with synovial sheaths. 2 MUSCLES OF THE SHOULDER. The Supra-spi'nous muscle 3 arises from the corresponding fossa of the scapula and from an in- vesting aponeurosis. Its fleshy fasciculi converge to a tendon which pro- ceeds beneath the acro- mion, adheres to the cap- sular ligament of the shoulder joint, and is in- serted into the upper part of the greater tuberosity of the humerus. The Infra-spi'nous MUSCLES ox THE BACK OF THE SCAFCLA. 1, supra-spinous muscle; lSCle 4 aris6S fr m the 2, infra-spinous muscle; 3, lesser terete muscle ; 4, greater terete Corresponding foSSa of the scapula and converges to a tendon, which, proceeding over the capsular ligament of the shoulder joint, is inserted into the middle part of the greater tuberosity of the humerus. The Lesser Te'rete muscle 5 arises from the upper part of the outer border of the scapula, and, in contact with the preceding muscle, fre- quently more or less conjoined with it, ascends to be inserted into the lower part of the greater tuberosity of the humerus. The Subscap'ular muscle 6 arises by broad fasciculi from the corre- 1 L. vaginalia ; vaginal and crucial ligaments. 2 Vaginae synoviales. 3 M. supra- spinatus ; m. supra-scapu- laris ; m. superscapularis superior. * M. infra-spinatus ; laris inferior. 6 M. teres minor. 6 M. subscapularis. m. superscapu- THE MUSCULAR SYSTEM. 227 FIG spending fossa of the scapula, and converges to a strong tendon, which passes in front of the shoulder joint, and is inserted into the lesser tu- berosity of the humerus. It lies upon the great ser- rated muscle, from which it is separated by a thin fascia 1 and some loose are- olar tissue extending from the axilla. Between its tendon and the neck of the scapula a synovial bursa is interposed. The subscapular muscle MUSCLES ON THE FROXT OF THE SCAPUH. 1, subscapular muscle: rotates the arm inwardly, 2 , greater terete muscle ; 3, upper part of the triceps extensor; 4. and the SUpra-SpinOUS, supra-spinous muscle. infra-spinous, and lesser terete muscles rotate it outwardly. The tendons of these four muscles, as they approach their insertion, partially surround the shoulder joint, form an intimate connection with its capsular liga- ment, and contribute very greatly to its strength. MUSCLES OF THE AKM. The Greater Te'rete muscle 2 forms part of the posterior fold of the axilla. It arises from the lower part of the inferior border and angle of the scapula, ascends beneath the latissimus muscle, and terminates in a broad tendon, which is inserted into the posterior bicipital ridge of the humerus, in contact with the ten- don of the latissimus. The long head of the triceps separates the greater from the lesser terete muscle. The greater terete muscle assists the latissimus in its action. FIG. 162. THE DELTOID MUSCLE. 1, its insertion; 2, its ori- gin from the clavicle; 3, origin from the spine and acromion of the scapula. The Del'toid muscle 3 forms the convex prominence of the shoulder. 1 Fascia subscapularis. 2 M. teres major; m. scapulo-humer- alis. 3 M. deltoideus ; m. deltiformis ; m. supra-acromio-humeralis; m. attollens humeri. 228 THE MUSCULAR SYSTEM. It arises, partially tendinous and fleshy, from the outer third of the clavicle, the acromion, and the lower margin of the spine of the scapula, and converges to be inserted, partially tendinous and fleshy, -into the roughness near the middle of the outer part of the humerus. The muscle has coarse, fleshy fasciculi, intermingled with tendinous fibres. The deltoid muscle is the elevator of the arm, and may raise the limb to a vertical position. It is also an efficient aid in drawing the arm backward or forward, and greatly contributes to the strength of the shoulder joint. FTG. 103. The Cor'aco-bra'chial muscle, 1 situated along the upper and inner part of the arm, arises tendinously, in common with the short head of the biceps muscle, from the coracoid process of the scapula, and pro- ceeds downward to be inserted about the middle of the inner side of the humerus. It is usually perforated by the external cutaneous nerve in its course to the outer part of the arm. The Bi'ceps Flex'or 2 is situated in front of the arm, extending from the scapula to the forearm. As the name indicates, it arises by two heads, of which the internal or short one is derived, in common with the preceding mus- cle, from the coracoid process of the scapula, The long head arises from the summit of the glenoid cavity, by a narrow tendon which passes through the upper part of the shoulder joint, insheathed by the synovial membrane, and de- scends along the bicipital groove of the humerus. The two heads conjoin and form a thick, fleshy belly, terminating in a strong tendon, which penetrates between the supinator and flexor muscles of the forearm, to be inserted into the back part of the tuberosity of the radius. Between the tendon of insertion and the fore part of the latter tuberosity, a synovial bursa is interposed ; and from the commence- ment of the same tendon an aponeurotic process of the forearm just below the internal condyle. MUSCLES OF THE FORE PART OF THE ARM. 1, coracoid process of the Hcapula: 2, coraco-clavicular liga- ment ; 3, coraco-acromial ligament : 4, subscapular muscle; 5, greater terete muscle; 6, coraco-brachial muscle; 7, biceps flexor; 8, its in- sertion into the tuberosity of the radius; 9, brachial muscle; 10, tri- ceps extensor. is given off to the fascia 1 M. coraco-brachialis, or humeralis ; m. perforatus, or m. p. Casserii. 2 M. biceps flexor cubiti ; m. biceps brachialis ; m. biceps interims ; m. coraco- radialis; m. scapulo-radialis; the biceps. THE MUSCULAR SYSTEM. 229 FIG. 164. The Bra'chial muscle 1 lies beneath the biceps muscle at the lower part of the arm, and covers the front of the elbow joint. It arises from the humerus each side of the insertion of the deltoid muscle and from the surface of the bone below, and converges to be inserted tendinously into the fore part of the coracoid process of the ulna. The coraco-brachial muscle draws the arm inwardly. If the hand is prone, the biceps supinates it by rotating the radius outwardly, and if the action of the muscle continues, the forearm is flexed. The brachial muscle is also a flexor of the forearm, and from its position greatly contributes to the strength of the elbow joint. The Tri'ceps Extensor 2 forms the whole of the fleshy mass on the posterior part of the arm, and, as the name implies, arises by three heads. The external head 3 arises from the humerus, below the greater tuberosity ; the short head 4 arises from the humerus, below the greater te- rete muscle ; and the long head 5 arises from the border of the scapula, below the glenoid cavity. The three heads conjoin in one fleshy belly, which in its descent receives a constant accession of fasciculi from the surface of the humerus, and terminates in a strong aponeur- otic band facing the muscle posteriorly and in- serted into the olecranon process of the ulna. Between the tendinous insertion and the top of ON THE BACK OF THE RIGHT ARM. i, the process, a synovia! bursa is introduced. Z^J&Jg* This mUSCle is the extensor Of the forearm. cle into the olecranon of the ulna; 5, radius ; 6, capsular ligament of The Ancone'us muscle 6 appears to be a con- the 8houlder joint ' tinuation of the triceps below the outer part of the elbow. It arises ViEAV OF THE TRICEPS EXTENSOR, 1 M. brachialis anticus ; m. b. inter- ims ; m. b. humero-cubitalis ; m. bra- chiaeus ; anterior brachial muscle. 2 M triceps extensor cubiti, or brachii; m. triceps brachialis. 3 Caput externum; anconsens exter- nus ; vastus externus ; short head of the biceps externus. 4 C. internum ; internal head; anc. in- ternus ; v. int. ; brachialis externus. 5 C. longum ; c. medius ; middle head; first head ; long head of the biceps ex- ternus; anconseus longus, or major. 6 M. anconaeus ; m. a. quartus, or mi- nor ; m. brevis cubiti ; m. cubitalis Rio- lani. 230 THE MUSCULAR SYSTEM. from the external condyle of the humerus, and is inserted into the trian- gular space at the upper and outer part of the ulna. It acts with the triceps, and was formerly described as a fourth head to this muscle. MUSCLES OF THE FRONT OF THE FOREARM. The Long Pal/mar muscle 1 lies between the radio- and ulno-carpal flexors. It arises from the internal condyle and intermuscular partitions, and forms a small belly terminating in a long tendon, which descends to be inserted into the annular ligament of the wrist and the palmar fascia. The Te'rete Pro'nator 2 is a small muscle extended obliquely across the upper part of the front of the forearm. It arises from the internal condyle of the humerus, and passes outward and downward to be inserted into a rough surface on the outer side of the radius. The Quad'rate Pro'nator 3 is a square muscle crossing the lower part of the forearm, beneath the flexor muscles. It arises from the front of the lower part of the ulna, and passes over the interosseous membrane to be inserted into the front of the radius. Superficially it is invested with a thin aponeurosis. The two pronator muscles, by rotating the radius inwardly upon the ulna, pronate the hand ; or, in other words, turn it with the palm down- ward. The Radio-carpal Flexor 4 lies in front of the forearm, extending obliquely from the inner condyle to the outer side of the metacarpus. It arises from the internal condyle and intermuscular partitions, and con- verges to a long, flat tendon, which, after passing through a fibrous canal at the outer part of the carpus, is inserted into the base of the second metacarpal bone. The Ulno-carpal Flexor 5 lies superficially on the ulnar side of the forearm. It arises from the internal condyle and the olecranon and by a strong aponeurosis from the upper part of the inner border of the ulna. Its belly terminates in a tendon, which is inserted into the pisiform bone and base of the last metacarpal bone. 1 M. palmaris longus ; m. ulnaris gra- pronator transversus ; m. quadratus ra- cilis ; latescentis chordae ; m. epitrochlo- dii ; m. cubito-radialis. carpi-palmaris. * M. flexor carpi-radialis; m. radialis 2 M. pronator radii teres; m. pronator internus ; m. palmaris magnus. rotundus ; m. p. obliquus; m. epitrochlo- 5 M. flexor carpi-ulnaris ; m. ulnaris radialis. internus ; m. cubitalis internus, or ante- 3 M. pronator radii quadratus ; m. rior. THE MUSCULAR SYSTEM. 231 Between the origin of this muscle from the humerus and the ulna, the ulnar nerve takes its course. FIG. 165. SUPERFICIAL MUSCLES OF THE FRONT OF THE FORE- ARM. 1, lower part of the biceps flexor ; 2, brachial muscle ; 3, lower part of the triceps extensor ; 4, terete pronator; 5, radio-carpal flexor; 6, long palmar muscle ; 7, superficial flexor of the fingers; 8, ulno-carpal flexor; 9, palmar fascia; 10, short palmar muscle ; 11, abductor of the thumb ; 12, short flexor of the thumb ; 13, long supinator ; 14, extensors of the thumb. The crossing and trans- verso bands on the fingers are the vaginal liga- ments inclosing the flexor tendons. FIG. 166. DEEP MUSCLES OP THE FRONT OF THE FOREARM. 1, internal lateral ligament of the elbow joint ; 2. capsular ligament of the same; 3, annular liga- ment inclosing the head of the radius; 4, deep flexor of the fingers ; 5, long flexor of the thumb ; 6, quadrate pronator; 7, adductor of the thumb; 8, 9, interosseous muscles. The Superficial Flexor of the Fingers 1 is situated in front of the forearm, between the preceding muscles. It arises from the internal con- dyle, the internal lateral ligament, the coronoid process of the ulna, and the radius below its tuberosity. The fleshy belly at the lower third of the forearm divides into four tendons, which proceed together beneath the annular ligament of the wrist, and diverge to be inserted into the base 1 M. flexor sublimus perforatus; m. f. digitorum sublimus, or perforatus. 232 THE MUSCULAR SYSTEM. of the second phalanges of the fingers. In front of the first phalanges the tendons are split, to give passage to the tendons of the deep flexor. Between the ulnar and radial origin of this muscle the median nerve pursues its course. FIG. 167. METACARPAL AND PHALANGIAL BONES OF THE FINGERS, WITH THEIR TENDONS AND LIGAMENTS. In the upper figure the flexor tendons are retained in position by the vaginal ligaments composed of transverse and obliquely crossing bands ; in the lower figure the flexor tendons are freed from the vaginal ligaments. 1, metacarpal bone ; 2, tendon of the superficial flexor ; 3, tendon of the deep flexor, passing through a perforation (*) of the former ; 4, tendon of the common extensor ; 5, a lumbrical muscle, arising from tlie deep flexor tendon and inserted into the extensor tendon; 6, an interosseous muscle, also inserted into the latter tendon. The Deep Flexor of the Fingers 1 is stronger than the preceding muscle, and is beneath it. It arises from the upper two-thirds of the front surface of the ulna and from the contiguous portion of the interosseous membrane, and likewise divides into four tendons. These, after passing through the annular ligament of the wrist, take their course through the perforations of the tendons of the superficial flexor, and are inserted into the base of the last phalanges. The Lum/brical muscles, 2 as implied by the name, are worm-like, fleshy fasciculi, four in number, situated in the palm of the hand. They arise from the radial side of the tendons of the deep flexor, and proceed to be inserted into the corresponding side of the tendinous expansions on the back of the fingers. The Long- Flexor of the Thumb, 3 situated at the outer side of the deep flexor of the fingers, arises from the front of the radius and the contiguous portion of the interosseous membrane. The fleshy belly terminates in a tendon, which passes beneath the annular ligament of the 1 M. flexor profundus perforans ; m. f. digitorum profundus, or perforans; m. f. tertii internodii digitorum; m. perforans manus. 2 M. lumbricales ; m. fidicinales. 3 M. flexor longus pollicis ; m. f. tertii internodii, or longissimus pollicis. THE MUSCULAK SYSTEM. 933 wrist, turns outwardly, and proceeds between the two portions of the short flexor to be inserted into the base of the last phalanx of the thumb. The tendons of the flexor muscles proceeding to the fingers are retained in their position by the vaginal ligaments. 1 In their passage beneath the latter they are attached to the front of the phalanges by narrow, accessory bands, 2 apparently serving to conduct nutritious vessels to the tendons. Synovial bursa? 3 lining the vaginal ligaments and fronts of the phalanges are thence reflected upon the flexor tendons and their accessory bands. MUSCLES OF THE BACK OF THE FOREARM. The Common Extensor of the Fingers* arises from the external con- dyle, contiguous intermuscular partitions, and the fascia of the forearm. Below the middle of the latter its fleshy belly separates into four ten- dons, which pass beneath the posterior annular ligament, and diverge to the fingers, upon the backs of which they expand. As they pass over the first phalanges they receive an addition of fibres at the sides from the lumbrical and interosseous muscles, and their middle portion is in- serted into the base of the second phalanges, while the lateral portions proceed onward and converge to be inserted together into the base of the last phalanges. On the back of the hand the inner three of the ten- dons are connected together by short, intervening bands, which associate their action much more than with the remaining tendon. The Long Supina'tor 5 lies on the radial side of the forearm, and ex- tends from near the middle of the humerus to the wrist. It arises from the external condyloid ridge below the insertion of the deltoid muscle, and converges to a long, flat tendon, which is inserted into the base of the styloid process of the radius. The Longer Radio-carpal Extensor 6 is partially covered by the pre- ceding muscle, and arises just below it from the same ridge. Its belly converges to a long, flat tendon, which descends along the radius, and is inserted into the base of the second metacarpal bone. The Shorter Kadio-carpal Extensor, 7 partially concealed by the last 1 Ligamenta vaginalia. 5 M. supinator longus; m. s. radii lon- 2 Vincula vasculosa ; v. accessoria ten- gus ; m. s. major; m. brachio-radialis. dinum; tenacula. 6 M. extensor carpi-radialis longior; 3 Vaginae synoviales. m. radialis externus longior, or primus. * M. extensor digitorum communis ; 7 M. extensor carpi-radialis brevior ; *m. digitorum tensor. m. radialis externus brevior, or secundus. 234 THE MUSCULAR SYSTEM. muscle, arises from the external condyle of the humerus, and is inserted by a flat tendon into the base of the third metacarpal bone. FIG. 168. MUSCLES OF THE BACK OF THE FOREARM. 1, biceps flexor ; 2, brachial muscle ; 3, triceps extensor ; 4, long supinator; 5, longer radio-carpal extensor; 6, shorter radio-carpal extensor; 7, insertion of the tendons of the last two muscles; 8, common exten- sor of the fingers; 9, extensor of the little finger; 10, ulno-carpal extensor; 11, short supinator; 12, ulno-carpal flexor ; 13, metacarpal and first phal- angial extensors of the thumb ; 14, second phalan- gial extensor of the thumb ; 15, posterior annular ligament. FIG. 169. DEEP MUSCLES ON THE BACK OF THE FOREARM. 1, humerus ; 2, olecranon ; 3, ulna ; 4, anconeus muscle ; 5, short supinator ; 6, metacarpal extensor of the thumb ; 7, first phalangial extensor ; 8, second phalangial extensor of the thumb; 9, extensor of the index finger ; 10, the dorsal interosseous muscle* between the metacarpal bones. The Ulno-carpal Extensor 1 lies at the ulnar side of the forearm, and arises from the external con- dyle, the upper part of the inner border of the ulna, and the fascia of the forearm. Its belly converges to a long, flat tendon, which descends to be inserted into the base of the last metacarpal bone. 1 M. extensor carpi-ulnaris ; m. ulnaris externus; m. cubitalis externus, or pos- terior. THE MUSCULAR SYSTEM. 235 The Extensor of the Little Finger 1 lies at the ulnar side of the com- mon extensor, with which it has its origin ; and its tendon, after passing through a separate canal of the annular ligament, conjoins the fourth tendon of the common extensor. The Short Supina'tor 2 is concealed by the long supinator and the radial extensors. It arises from the external condyle of the humerus, the external lateral ligament of the elbow joint, and the ulna, and winds obliquely outward and downward upon the radius, into the upper third of which it is inserted. The Metacarpal Extensor of the Thumb 3 crosses the forearm obliquely below the preceding muscle, and arises from the ulna, the interosseous membrane, and the radius. Its belly terminates in a tendon, which crosses those of the radio-carpal extensors, and, after passing through a groove in front of the styloid process of the radius, is inserted into the base of the metacarpal bone of the thumb. The First Phalan'gial Extensor of the Thumb 4 is a small muscle situ- ated below the preceding to its ulnar side, and has the same points of origin. Its fleshy belly terminates in a narrow tendon, which accompa- nies that of the preceding muscle, and is inserted into the base of the first phalanx of the thumb. The Second Phalan'gial Extensor of the Thumb 5 arises below the preceding muscle from the ulna and interosseous membrane. Its belly terminates in a tendon, which passes through a distinct canal of the an- nular ligament from that occupied by the tendons of the first phalangial and metacarpal extensors, and proceeds to be inserted into the base of the last phalanx of the thumb. The Extensor of the Index Finger 6 lies at the ulnar side of the pre- ceding muscle, and has the same points of origin. Its tendon of inser- tion passes through a groove of the radius, and conjoins the tendon of the common extensor to the index finger. 1 M. extensor minimi digiti, or m. e. pollicis primus; m. e. secundi internodii proprius m. d. ; m. auricularis. ossis pollicis. 2 M. supinator radii brevis, or minor ; & M. extensor secundi internodii polli- m. epicondylo-radialis. cis ; m. extensor longus, or major polli- 3 M. extensor ossis metacarpi pollicis ; cis ; m. e. pollicis secundus; m. e. tertii m. abductor longus pollicis ; m. e. primi internodii ossis pollicis. internodii ossis pollicis. 6 M. extensor indicis ; indicator; m. * M. extensor primi internodii pollicis; ext. proprius indicis ; m. e. p. primi di- m. extensor brevis, or minor pollicis ; m. e. giti. 236 THE MUSCULAR SYSTEM. MUSCLES OF THE HAND. FIG. 170. The Short Pal'mar muscle 1 is a thin layer of fleshy fibres situated beneath the skin at the inner side of the palm of the hand. It arises from the annular ligament and pal- mar fascia, and proceeds inwardly to be attached to the integument. MUSCLES OF THE PALMAR SURFACE OF THE HAND. 1, anterior annular ligament ; 2, origin and inser- tion of the abductor of the thumb ; its belly re- moved so as to expose 3, the metacarpal flexor ; 4, 5, two bellies of the short flexor; 6, adductor of the thumb; 7, lumbrical muscles; 8, tendons of the deep flexor of the fingers passing through the slits of the superficial tendons; 9, tendon of the long flexor of the thumb, passing from between the bellies of the short flexor; 10, abductor of the little finger; 11, short flexor of the little finger, with the edge of the adductor seen beneath; 12, pisiform bone ; 13, first interosseous muscle. MUSCLES OF THE BALL OF THE THUMB. The Abductor 2 is the most superficial and external of the muscles of the ball of the thumb. It arises from the annular ligament of the wrist, and is inserted into the base of the first phalanx of the thumb. The Metacarpal Flexor, 3 beneath the preceding, arises from the same source, and is inserted into the length of the metacarpal bone of the thumb. The Short Flexor 4 consists of two portions, between which lies the tendon of the long flexor of the thumb. It arises from the annular liga- ment and the second row of c >al bones, and is inserted tendinously into the base of the first phala of the thumb. Within its tendinous insertion the sesamoid bones are imbedded The Adductor 5 is a triangular muscle, arising from the length of the 1 M. palmaris brevis; caro quadrate; opponens pollicis; m. f. primi internodii m. carpaeus. 2 M. abductor pollicis; m. a. brevis pol- pollicis ; m. antithenar. * M. flexor brevis pollicis ; m. f. secundi licis; m. a. brevis alter p. ; m. scapho- internodii p.; m. f. primi et secundi i. p.; carpo-superphalangeus pollicis. 3 M. flexor ossis metacarpi pollicis ; m. m. thenar. 5 M. adductor pollicis ; m. metacarpo- phalangeus pollicis. THE MUSCULAR SYSTEM. 237 middle metacarpal bone, and converging to be inserted into the base of the first phalanx of the thumb. MUSCLES OF THE LITTLE FINGER. The Abductor 1 lies on the margin of the palm. It arises from the pisiform bone, and is inserted into the base of the first phalanx and ex- tensor tendon of the little finger. The Short Flexor 2 arises from the annular ligament of the wrist and the unciforrn bone, and is inserted into the base of the first phalanx of the little finger. It is not unfrequently inseparable from the preceding muscle. The Adductor 3 arises from the same points as the preceding muscle, and is inserted into the length of the metacarpal bone of the little finger. THE INTEROSSEOUS MUSCLES. The Interos'seous muscles 4 are seven in number, and, as implied by their name, are situated in the intervals of the metacarpal bones four on the back, and three on the palm of the hand. The Dorsal Interos'seous muscles, 5 four in number, arise from the contiguous sides of the metacarpal bones, and each forms a penniform belly, terminating in a tendon, which partially conjoins the extensor ten- dons on the back of the finger, and is partially inserted into the base of the first phalanx. The first of this series is inserted into the radial side of the index finger, and is an abductor; the succeeding two are inserted into the opposed sides of the middle finger, and act as an abductor and adductor ; and the last one is inserted into the ulnar side of the ring finger, and is an adductor. The Palmar Interos'seous muscles," three in number, arise from a single side of the metacarpal bones of t$e index, ring, and little fingers, and terminate in the same manner as 1'.:$' dorsal series. The first is on the ulnar side, and is an adductor, and the other two are on the radial side, and are abductors. 1 M. abductor minimi digiti ; m. exten- 3 M. adductor minimi digiti ; m. a. sor tertii internodii m. d.; m. carpo-pha- metacarpi m. d.; m. carpo-metacar- langeus m. d.; m. hypothenar minor peus m. d. metacarpeus. * M. interossei. 2 M. flexor brevis, or parvus minimi 5 M. i. externi ; m. i. bicipites. digiti. 6 M. i. interni. 238 THE MUSCULAR SYSTEM. THE LOWER EXTREMITIES. The Lower Extremities, which support and carry the other portions of the body, are accordingly larger and stronger, and provided with more powerful muscles than the upper extremities. At the back part of the hips are the buttocks or nates, 1 separated by the fissure of the anus, and from the thighs below by the sub-ischiatic grooves. The thigh. 2 is separated from the abdomen by the groin or inguinal region, and gradu- ally becomes narrowed to the knee. 3 Behind the latter is the space called the poplite'al region, or hollow of the knee, 4 bounded on each side by the "ham-strings." The condyles of the femur and tibia pro- duce the lateral prominences of the knee, the knee-cap producing the eminence in front. The calf 5 or thick mass of the leg 6 narrows down- ward to the "tendon of Achilles," which terminates at the heel. 7 The ankles correspond with the malleoli of the tibia and fibula. The skin of the buttock is thick, but becomes thin in the fissure of the anus. Upon the outer part of the thigh and leg it is thick, dense, and comparatively dull in sensibility ; becomes thinner, more extensible, and sensitive toward the inner part, and is everywhere quite movable. Upon the back of the foot the skin is thin and extensible ; but upon the sole, is thick, inextensible, and quite immovable. FASCIA OF THE LOWER EXTREMITY. The Superficial fascia of the lower extremity, as in other divisions of the body, is in most parts separable into two layers, of which the inner one is thin and membranous, the outer one loose in texture, and more or less filled with fat. Upon the buttock the superficial fascia is ordinarily occupied with a large quantity of fat. Upon the thigh and leg it also usually contains much fat, except over the great trochanter and the patella, in which positions synovial bursas are substituted. In the sole of the foot it is always occupied with fat, and is most intimately blended with the struc- ture of the skin. At the heel, and bend of the first and last metatarsal bones, it contains synovial bursa?. Between the fatty and membranous layers of the superficial fascia, the superficial veins and cutaneous nerves have their course. 1 Glutia; sedilia; clunes; podex ; pos- 4 Popliteal fossa; the hock; the hough; teriors ; bottom. the ham. 2 Femur ; crus ; merus. 5 Sura ; gastrocnemium. 8 Genu. 6 Crus; scelos; cneme. 7 Calx ; talus. THE MUSCULAR SYSTEM. 239 The fatty layer at the groin and hip is continuous with the correspond- ing layer of the superficial fascia of the abdomen. The deeper or mem- branous layer adheres to Poupart's ligament and the crest of the ilium. At the saphenous opening it is pierced by the cutaneous vessels of the contiguous regions, from which circumstance this perforated portion of the superficial fascia is called the criVriform fascia. 1 The Deep fascia of the lower extremity, like that of the upper ex- tremity, forms a complete envelope to the limb, sends partitions between the muscles, and gives sheaths to the great blood-vessels. It is called, from its relative positions, the femoral fascia, the crural fascia, and the fascia of the foot. The Fern/oral fas'cia or fas'cia la'ta, 2 is attached along the crest of the ilium, the back of the sacrum and coccyx, the border of the ischium and pubis and Poupart's ligament, with which it is continuous. Upon the great gluteal muscle it forms a thin investment; but in ad- vance of this, and extending in the same line the entire length of the outer part of the thigh, it is so thick and strong as to appear like an aponeurosis. This portion of the fascia is composed of longitudinal fibres strengthened by transverse ones ; gives partial origin to the middle gluteal muscle ; receives, over the position of the great trochanter, part of the insertion of the great gluteal muscle; and after insheathing its own peculiar tensor muscle, receives the insertion of this altogether. In passing from the outer to the inner part of the thigh, the femoral fascia becomes gradually thinner, and is mainly composed of transverse fibres. Between all the muscles it sends partitions, among the most important of which are the so-called external and internal intennuscular par- titions. 3 The former of these is a strong process separating the quadriceps extensor and the biceps flexor, and attaching itself to the asperous ridge from the insertion of the great gluteal muscle to the outer condyle of the femur. The other is a thinner partition separating the quadriceps extensor from the adductor muscles, and connecting itself with the aspe- rous ridge leading to the inner condyle. At the knee the fascia receives offsets from the extensor and flexor tendons, forms a general envelope 4 to the joint, and becomes continuous with the crural fascia. Below the groin, the femoral fascia is so important in its relations with the femoral blood-vessels and the subject of femoral hernia, that it re- quires special attention. The inner and outer portions of the fascia, 1 Fascia cribrosa. 3 Ligamentum intermusculare exter- 2 Fascia femoris ; fHata aponeurosis ; num et internum. f. aponeurotica femoris : vagina femoris; * Involucrum generale. crural, or femoral aponeurosis. 240 THE MUSCULAR SYSTEM. from the muscles they immediately invest, are conveniently named the pectineal and sartorial fascia. FIG. 171. VIEW OF THE INGUINAL CANAL. 1, por- tion of the fleshy belly of the external ob- lique muscle; 2, its aponeurosis; 3, por- tion of the latter raised up, exposing the inguinal canal; 4, linea alba; 5, insertion of the aponeurosis of the external oblique into the body of the pubis; 6, its insertion into the spine of the pubis, named Pou- part's ligament; 7, division of the fibres of the aponeurosis crossed by transverse fibres ; 8, external abdominal ring, the ter- mination of the inguinal canal : 9, anterior superior spinous process, the origin of Poupart's ligament ; 10, arching lower bor- der of the internal oblique and transverse muscles; 11, conjoined tendon of the latter muscles ; 12, fibres of the cremaster muscle descending on the spermatic cord from the edges of the muscles just named ; 13, rests on the transverse fascia; to its right are the epigastric vessels crossing the course of the inguinal canal; 14, iliac portion of the femoral fascia ; 15, pubic portion ; 16, falciform process; 17, saphenous opening: IS, saphenous vein joining the femoral vein through the saphenous opening; 19, the femoral artery and vein exposed by raising the portion of fascia which forms the falciform process ; 20, suspensory ligament of the penis. The pectine'al fas'cia 1 invests the corresponding muscle behind the femoral blood-vessels. It is attached along the body and pectineal line of the pubis, and at its outer border becomes continuous with the iliac fascia investing the psoas and iliac muscles, and with the posterior layer of the sartorial fascia. The sarto'rial fas'cia, 2 after including the corresponding muscle, in the groin is attached along Poupart's ligament and extends in front of the femoral blood-vessels. A couple of inches below the pubis, it be- comes continuous with the pectineal fascia, and between these two points includes an oval space named the saphe'nous opening, 3 from the long saphenous vein entering at this position to join the femoral vein. The outer part of the saphenous opening is defined by a lunated edge of the sartorial fascia, named the fal'ciform process, 4 the upper extremity 5 of 1 Pubic portion of the femoral fascia, or fascia lata ; fascia ischio-pubica. 2 Iliac portion of the femoral fascia, or fascia lata ; fascia ilio-pectinea. 3 Fossa ovalis ; inferior orifice of the crural canal. 4 Plica falciformis ; falciform expan- sion, or semilunate edge of the fascia lata. 5 Cornu superius ; upper horn ; Key's ligament ; femoral ligament. THE MUSCULAR SYSTEM. 241 which is continuous with Gimbernat's ligament; the lower extremity, 1 with the pectineal fascia. The inner part and bottom of the opening are formed by the latter fascia as it dips from within, outwardly, behind the femoral blood-vessels. The saphenous opening is occupied with a portion of the superficial fascia, called cribriform fascia, 2 from its being perforated by many small superficial vessels passing between the contiguous parts and the femoral vessels. The cribriform fascia is continuous with the falciform process, and careful manipulation is required to distinguish the lunated edge of the latter. When the fascia is removed, the falciform process is observed to overlie the femoral vessels ; its upper and lower extremities are usually well marked, while the middle portion is less defined. The Cru/ral fascia 3 or deep fascia of the leg, for the most part well marked and strong, adheres to the heads of the tibia and fibula, to the anterior and internal borders of the former bone, and to both malleoli. It receives offsets from the tendons of insertions of the sartorius, gra- cilis, semitendinous, and biceps muscles, and is mainly composed of transverse fibres. It is strongest in the outer part of the leg, where it gives partial origin to the heads of the muscles, and is continuous with their internmscular partitions. It is thinnest on the back of the leg, 4 where it consists of a layer investing the muscles of the calf, and another 5 separating the latter from the deeper muscles. In the vicinity of the ankle joint, the crural fascia receives an acces- sion of fibres, much increasing its strength, and constituting the annular ligaments, which bind down the tendons of the muscles as they turn for- ward from the leg to the foot. The anterior an'nular ligament 6 is a strong band extending obliquely in front of the ankle joint, from the inner malleolus to the anterior and outer part of the calcaneum. It consists of two layers, which inclose the tendons in several compartments as they cross the ankle joint. Thus the tendons of the long extensor of the toes occupy a compartment next to the fibula, that of the anterior tibial muscle occupies another next to the tibia, and the tendon of the extensor of the great toe an intermediate compartment. The anterior tibial blood-vessels and nerve are behind the ligament. A band of fibres, 7 above the ankle joint, extended be- tween the front of the tibia and the fibula, is sometimes described as a portion of the anterior annular ligament ; and another band crosses 1 Cornu inferius; lower horn. 5 Deep fascia of the leg; deep crural 2 F. cribriformis. % fascia. 3 Fascia cruralis. s Lig. annulare anterius; annular liga- * In this position called sural fascia ; ment of the tarsus. f. suralis. ? Lig. transversum. 16 242 THE MUSCULAR SYSTEM. the annular- ligament from the external malleolus to the inner side of the tarsus. 1 The internal an'nular ligament 2 is a band of loose fibres extending from the internal malleolus to the back of the astragalus and the inner side of the calcaneum. It converts the groove at the back of the inter- nal malleolus into a canal for the passage of the tendons of the posterior tibial and long flexor muscles ; and the grooves at the back of the astra- galus and beneath the calcaneum into a canal for the passage of the tendon of the long flexor of the great toe. Between these two canals the ligament transmits the posterior tibial vessels and nerves. A thin offset from the ligament extends superficially to the tendon of Achilles and the tuberosity of the calcaneum. The external an'nular ligament 3 is less marked than the preceding, and consists of a band of loose fibres starting from the external malleo- lus to be attached to the outer part of the calcaneum, and binding down the tendons of the peroneal muscles. As the tendons of the muscles pass in their course from the leg to the foot, beneath the annular ligaments, they are invested with synovial bursse. The fascia on the back of the foot is a thin extension from the ante- rior annular ligament. The plantar fascia 4 consists of three portions, as in the case of the palmar fascia. The inner and outer portion is thin, and invests the small muscles of the toes. The middle portion is strongest, and resembles the corresponding portion of the palmar fascia. It is composed of longitudinal, diverging fibres, strengthened with transverse ones, and forms a triangular investment to the short flexor of the toes, to which it gives partial origin. Its apex is attached to the tuberosity of the calcaneum, and its base divides into five processes, each of which subdivides to be inserted into the metaoarpo-phalangial and contiguous vaginal ligaments. At the sides it is continuous with the lateral portions of the fascia, and with intermuscular partitions dipping into the sole. The vag'inal ligaments which inclose the flexor tendons of the toes have the same arrangement as those of the fingers. SKETCH OF THE ANATOMY CONCERNED IN FEMORAL HERNIA. The position of the groin is defined by Poupart's ligament, 5 which is the line of continuity of the aponeurosis of the external oblique muscle 1 Forming with the annular ligament, turn externum ^ retinaculuin tendinum the lig. cruciatum. pereneorum. 2 Lig. annulare internum ; 1. lacinia- * Aponeurosis plantaris. turn internum. 5 Lig. Pouparti ; 1. Fallopii ; crural 3 Lig. annulare externum ; 1. lacinia- arch. THE MUSCULAR SYSTEM. 243 of the abdomen with the femoral fascia, extending from the anterior superior spinous process of the ilium to the spine of the pubis. Poupart's ligament constitutes the femoral arch., 1 the bottom of which is formed by the anterior border of the ilium and the horizontal ramus of the pubis. The inner part of the arch is formed by Gimbernat's liga- ment, 2 which is a triangular process from Poupart's ligament, extending a short distance outwardly along the pectineal line of the pubis. The femoral arch is occupied externally by the iliac and psoas muscles, with the anterior crural nerve situated in the angular interval of their conjunction. Internally it is occupied by the femoral artery, vein, and lymphatics, inclosed together within a sheath, and resting on the pec- tine'al fascia, 3 which invests the corresponding muscle. Below the inner part of Poupart's ligament is the oval space, named the saphe'nous opening, from its admitting the saphenous vein to join the femoral vein. The opening is defined externally by the lunated edge of the fal'ciform process 4 of the sarto'rial fascia. 5 The upper end 6 of this process is continuous with both Gimbernat's and Poupart's liga- ment, and its lower end is continuous with the pectineal fascia. The saphenous opening is occupied by the cribriform fascia, 7 a portion of the superficial fascia, so named from its perforated condition, aris- ing from the transmission of the superficial vessels of the neighboring parts. Behind the falciform process, from without inwardly, lie in succession the femoral artery, vein, and lymphatics, which together are inclosed in a sheath 8 closely connected with the contiguous fasciae. The femoral vessels included within their sheath may be viewed as occupying the tube of a membranous funnel whose expanded portion is formed by the trans- verse, iliac, and pelvic fascia of the abdomen and pelvis. Between the femoral vein and Gimbernat's ligament, within the sheath of the femoral vessels, is a small space named the fem'oral ring. 9 This is occupied with lymphatic vessels, and a gland enveloped in some loose connective tissue, 10 and is the position at which femoral hernia occurs. When the femoral ring is cleared of its contents, the end of the little finger may be introduced into it from the abdomen to the upper part of 1 Crural arch. 6 Key's ligament. 2 Lig. Gimbernati ; Key's ligament. 7 F. cribrosa. 3 Pubic portion of the fascia lata. 8 Femoral sheath ; vagina vasorum * Plica falciformis ; lunated edge of cruralium. the fascia lata. 9 Crural ring ; annulus cruralis. 5 Iliac portion of the fascia lata. 10 Septum crurale ; septum transver- sum ; crural septum. 244 THE MUSCULAR SYSTEM. the saphenous opening, a depth of about half an inch. 1 Its internal and anterior boundary 2 is the edge of Gimbernat's ligament continuous with the edge of the falciform process ; its outer boundary the femoral vein, and its posterior boundary the pubis and pectineal fascia. When the lower limb is extended and rotated with the toes directed outwardly, the falciform process and Gimbernat's ligament become tense, and the femoral ring is narrowed ; and when the limb is flexed and ro- tated with the toes directed inwardly, the same points become relaxed, and the ring is widened. 3 As the seat of constriction or strangulation of femoral hernia occurs within the circle of the femoral ring, the facts just mentioned afford important indications as to the mode of treatment. Besides the femoral vein, other blood-vessels in relation with the femo- ral ring are the epigastric artery and veins situated above it externally. When, as occasionally happens, the obturator artery is derived from the external iliac, as this is about to emerge from the femoral arch, it descends at the outer or sometimes at the inner side of the femoral ring. In femoral hernia, the hernial sac, consisting of a pouch of perito- neum containing a portion of the bowels, descends through the femoral ring within the sheath of the femoral blood-vessels. Arriving at the saphenous opening, and finding least resistance in front, it protrudes for- ward, and subsequently, as it increases, extends outwardly in the course of the groin. Such a hernia has for its coverings from without inwardly, the skin, the subjacent fatty layer of the superficial fascia, and lastly, a fibrous layer, 4 more or less distinct, and derived from the cribriform fascia and the sheath of the femoral blood-vessels. MUSCLES OF THE BUTTOCK. The Great Glu'teal muscle 5 is a thick, lozenge-shaped mass, composed of coarse fleshy fasciculi, and extending from the back of the pelvis to the upper and outer part of the thigh. It arises from the posterior fourth of the crest of the ilium, the posterior surface of the sacrum and 1 The depth of space has been named Gimbernat's ligament, a semispiral edge, the femoral canal, its upper orifice being which becomes more enrolled, and con- the femoral ring, its lower orifice the sequently includes a narrower space, saphenous opening. when the limb is rotated outwardly, and 2 Usually stated to be Poupart's liga- becomes partially unwound when the ment, but as the falciform process is con- limb is rotated inwardly. tinuous with both Gimbernat's and Pou- 4 Fascia propria of femoral hernia, part's ligament, the anterior boundary 5 M. glutseus magnus, major, maximus, may be considered as stated in the text. or extimus ; m. sacro-fernoralis ; m. ilio- 3 The falciform process forms, with sacro-femoralis. THE MUSCULAR SYSTEM. 245 j but the middle and small gluteal muscles may rotate them either inwardly \^or outwardly, according as their posterior or anterior fibres are brought coccyx, and from the greater sacro-ischiatic ligament. From this origin its fleshy fasciculi proceed outward and downward, and terminate in a thick aponeurosis, which is inserted into the femoral fascia over the greater trochanter of the femur, and into the rough surface extending from the latter process to the asperous ridge. The lower border of this muscle forms the fold of the buttock, and in the erect position of the body covers the tuberosity of the ischium, but glides from it in the sitting position. Between its tendon and the greater trochanter of the femur a large synovial bursa is interposed, and another is situated between the muscle and the tuberosity of the ischium. The Middle Glu'teal muscle, 1 covered at its fore part by a thick portion of the femoral fascia, and at its back part by the preceding muscle, arises from the dorsal sur- face of the ilium, between the crest of the latter and the superior curved line, and from the investing femoral fascia. Descending, its fasciculi converge to a short, thick tendon, which is inserted into the outer sur- face of the greater trochanter. Be- tween the upper part of the latter and the tendon, a synovial bursa is interposed. The Small Glu'teal muscle, 2 con- cealed by the preceding, arises from the dorsal surface of the ilium be- tween the superior and inferior curved lines, and converges to a tendon, which is inserted into the inner part of the summit of the greater trochanter. Between the latter and the tendon a synovial bursa is inter- posed. MUSCLES OF THE BUTTOCK. 1, ilium; 2, sacrum: 3. posterior sacro-iliac ligament; 4, tuberosity of the ischium ; 5, great sacro-ischiatic ligament; 6, small sacro-ischiatic ligament; 7, greater trochanter; 8, small gluteal muscle; 9, pyriform muscle; 10,12, geminous muscle, including between its two fasci- culi the termination, 11, of the internal obturator muscle; 13, quadrate femoral muscle; 14, upper part of the great adductor of the thigh; 15, exter- nal vastus muscle ; 16, biceps flexor ; 17, gracilis ; 18, semi-tendinous muscle. 1 M. glutams medius, or secundus ; m. ilio-trochanterius. 2 M. glutaeus minimus, minor, tcrtixis, or intimus; m. ilio-ischio-trochanterius. 246 THE MUSCULAR SYSTEM. The External Obtu'rator muscle 1 is situated exterior to the cavity of the pelvis, and arises from the borders of the obturator foramen and from the obturator membrane. Converging to a tendon, it passes behind the neck of the femur to be inserted into the trochanteric fossa. The Pyr'iform muscle 2 arises within the pelvis from the front surface of the second, third, and fourth divisions of the sacrum, and from the lower part of the sacro-iliac symphysis. Passing from the pelvis through the greater sacro-ischiatic foramen, it converges, to be inserted, by a round tendon, into the greater trochanter, beneath the small gluteal muscle. The Internal Obturator muscle 3 arises within the cavity of the pelvis from the border of the obturator foramen and from the obturator mem- brane. Converging to a tendon, it passes through the lesser sacro-ischi- atic foramen to be inserted into the trochanteric fossa. The lesser ischiatic notch, upon which the tendon plays in the action of the muscle, is faced with fibro-cartilage, and furnished with a synovial bursa to facilitate movement. The Gem'inous muscle 4 envelops the tendon of the preceding muscle, and consists of a pair of accessory fleshy fasciculi to it, usually described as two distinct muscles. 5 It arises from the spine and back part of the tuberosity of the ischium, and after including the tendon of the internal obturator muscle, is inserted in company with it into the trochanteric fossa. The Quadrate Fem'oral muscle 6 arises from the outer border of the tuberosity of the ischium, and proceeds outwardly to be inserted into the rough line descending from the greater trochanter. The gluteal muscles, accordingly as they act from their origin or inser- tion, are abductors of the thighs, or they fix the pelvis, and with it the trunk upon the lower extremities. They also rotate the thighs outwardly, 1 M. obturator, or obturatorius exter- * M. geminus, or gemellus ; m. gemini, nus ; m. sub-pubio-trochantereus exter- or gemelli ; marsupium carneum ; m. nus ; m. extra-pelvio-pubio-trochante- marsupialis ; m. ischio-spini-trochante- reus. reus ; m. canaliculatatus ; m. accessories 2 M. pyriformis ; m. pyramidalis ; m. obturatoris interni. p. femoris : m. iliacus externus ; m. 6 M. geminus, or gemellus superior sacro-trochantereus ; m. primus et supe- and inferior ; m. secundus et tertius rior quadrigeminus. quadrigeminus. 3 M. obturator, or obturatorius inter- 6 M. quadratus femoris ; m. tubei*-is- nus ; m. sub-pubio-trochantereus inter- chio-trochantereus ; m. ischio-subtro- nus ; m. marsupialis ; m. bursalis ; m. chantereus ; m. quartus quadrigeminus intro-pelvio-trochantereus. quadratus. THE MUSCULAR SYSTEM. 247 into action. The obturator, pyriform, geminous, and quadrate femoral muscles rotate the thighs outwardly. THE ILIAC FASCIA. The Il'iac fas'cia 1 invests the iliac and psoas muscles, and is a con- tinuation of the same fibrous membrane, constituting in other positions the transverse and pelvic fascia. It adheres to the lumbar fascia, the arcuate ligaments, the vertebral column, the crest of the ilium, Poupart's ligament, and the pubis. Together with the transverse and pelvic fascia it converges to become the sheath of the femoral blood-vessels. MUSCLES OF THE ILIAC KEGION AND LOIN. The Il'iac muscle 2 arises from the corresponding fossa of the ilium, and converges to the femoral arch, under which it passes to be inserted, in con- junction with the psoas muscle, into the smaller trochanter of the femur. The Pso'as muscle 3 arises from the sides of the bodies and transverse processes of the last dorsal and the lumbar vertebrae, and the interme- diate intervertebral disks. Descending from the loins along the brim of the pelvis, it passes under the femoral arch and terminates in a tendon, which, being joined by the preceding muscle, is inserted into the back part of the smaller trochanter. The 'upper extremity of the muscle has the internal arcuate ligament of the diaphragm extended across it. At the origin from the sides of the vertebrae, tendinous arches separate it from the lumbar arteries and veins and the anastomotic filaments of the sympathetic nerve. Between the tendon of insertion and the smaller trochanter, a synovial bursa is interposed. Occasionally, a Small Pso'as muscle* is situated in front of the for- mer. It arises from the sides of the bodies of the upper two lumbar ver- tebrae, and terminates in a thin tendon, which expands at the brim of the pelvis into the iliac fascia, and is connected with the ilio-pubic eminence. The iliac and psoas muscles, according to the fixation of their origin or insertion, bend either the trunk or the lower extremities forward. They also rotate the thighs outwardly, by drawing the smaller trochanter forward. In conjunction with the gluteal muscles they maintain the erect condition of the body. 1 Fascia iliaca. 3 Greater psoas muscle ; m. psoas ma- 2 M. iliacus ; internal iliac muscle; m. jor; m. lumbalis; m. praelumbo-trochan- iliacus internus ; m. ilio-trochantereus ; tereus ; part of the m. flexor femoris ; m. part of the m. flexor femoris ; m. femur femur moventium sextus. moventium septimus. * M. psoas parous ; m. prae-lumbo- pubius. 248 THE MUSCULAR SYSTEM. MUSCLES ON THE FRONT OF THE THIGH. FIG. 173. The Ten'sor of the Fern/oral Fas'cia 1 is a short, flat muscle, situated at the upper and outer part of the thigh, and inclosed in a sheath of the femoral fascia. It arises from the anterior superior spinous process of the ilium, between the sartorius and gluteal muscles, and descends in front of the greater trochanter, to terminate in the femoral fascia, * a short distance below the latter. The Sarto'rius muscle 2 arises tendinously from the anterior superior spinous process of the ilium, and in the form of a long fleshy band descends obliquely across the thigh to the inner side of the knee, where it terminates in a tendon, which expands to be inserted on the inner side of the tibia, just beiow its tuberosity. The tendon of insertion gives off a process to the crural fascia, and between it and the tendon of the succeeding muscle a synovial bursa is interposed. The sartorius flexes the leg upon the thigh, and if it continues its action the leg is drawn . across the opposite thigh. The Grrac'ilis muscle 3 arises by a thin apo- neurosis from the margin of the symphysis and descending ramus of the pubis. In the form of a long fleshy band it passes down on the in- ner part of the thigh, and terminates at the knee in a narrow tendon, which expands to be inserted beneath the sartorius tendon. Between its tendon and the tibia a synovial bursa is placed. The gracilis adducts the thigh, and assists the action of the preceding muscle. MUSCLES OF THE ILIAC REGION AND FRONT OF THE THIGH. 1, CFCSt of the ilium ; 2, anterior superior spinous process : 3, middle gluteal muscle ; 4, tensor of the femoral fascia; 5, sartorius; 6, rectus; 7, external vastus ; 8, internal vastus ; 9, inser- tion of the quadriceps extensor into the patella; 10, iliac muscle; 11, psoas muscle; 12, pectineal muscle; 13, long adductor ; 14, great adduc- tor; 15, gracilis muscle. 1 M. tensor vaginae femoris ; m. t. fas- ciae latse ; m. fasciae latse ; m. mernbra- nosus ; m. fascialis ; m. aponeurosis ; m. ilio-aponeurosi femoralis. 2 M. sartorius ; m. fascialis ; m. f. longus ; m. longissimus femoris ; m. cristo-tibialis ; m. ilio-prae-tibialis. 3 M. gracilis, or rectus internus, or interior; m. pubio-prae tibialie. THE MUSCULAR SYSTEM. 249 The Quad'riceps Exten'sor 1 occupies the whole front and sides of the thigh, and, as implied by its name, has four heads of origin, called the rectus, the external and internal vastus, and the cruralis. The Rec'tus 2 arises, by two short thick tendons, from the anterior infe- rior spinous process of the ilium and the summit of the acetabulum. Descending in front of the thigh, its fleshy fasciculi form a penniform belly ending in a stout, flat tendon, which is joined by the tendons of the other heads of the quadriceps, just above the knee. The remaining three heads, more intimately associated with one another than with the rectus, are sometimes described as a distinct muscle. 3 The External Vas'tus, 4 the largest portion of the quadriceps," arises by an aponeurosis from the base of the greater trochanter and from the outer border of the asperous ridge. The Internal Vas'tus 5 arises from the inner border of the asperous ridge ; and the Crura'lis 6 arises from the front of the femur, between the two preceding heads of the quad- riceps. The fleshy fasciculi of the internal and external vastus pro- ceed downward and forward, those of the cruralis proceed directly down- ward, and all together terminate in a broad tendon, which conjoins with that of the rectus to be inserted into the base, sides, and front of the patella. Yiewing the ligament of the patella as a continuation of the tendon of the quadriceps, this is then inserted into the tuberosity of the tibia. The quadriceps extends the leg upon the thigh. Some detached fas- ciculi 7 of the muscle descend from the lower part of the femur to the synovial capsule of the knee joint, and serve to retain this capsule in its proper position. The Pectine'al muscle 8 arises from the horizontal ramus of the pubis, between its spine and the ilio-pectineal eminence, and descends on the inner side of the femur to be inserted into the line leading from the smaller trochanter to the asperous ridge. The Long Adduc'tor, 9 situated on the same plane as the former muscle, arises tendinously from the front of the pubis, and descends 1 M. quadriceps extensor cruris. 6 M. vastus medius ; m. venter poste- 2 M. rectus femoris ; m. rectus, or gra- rior ; m. cruraeus. cilus anterior, or cruris ; m. ilio-rotuleus ; 7 M. subcrureus, or subcruralis ; m. anterior straight muscle. articulares genu. 3 M. triceps extensor cruris ; m. femo- 8 M. pectineus, or pectinalis ; m. pu- ralis, or cruralis ; m. trifemoro-rotuleus, bio-femoralis ; m. lividus. or tibio-rotuleus. M. adductor longus ; m. a. femoris * M. vastus, or venter externus. primus ; caput longum m. ad. tricipitis ; 5 M. vastus, or venter interims. m. ad. primus ; m. pubio-femoralis. 250 THE MUSCULAR SYSTEM. obliquely to be inserted into the middle third of the asperous ridge of the femur. The Short Adduc'tor, 1 concealed by the preceding two muscles, arises from the body and descending ramus of the pubis, and descends ob- liquely to be inserted into the upper third of the asperous ridge of the femur. The Great Adduc'tor 2 is a large, triangular muscle, forming a parti- tion between the front and back part of the thigh. It arises from the descending ramus of the pubis and the ramus and tuberosity of the ischium, and radiates outward and downward to be inserted tendinously into the whole length of the asperous ridge of the femur, extending also by a tendinous cord to the internal condyle. The lower third of the insertion of the great adductor is perforated for the passage of the femoral blood-vessels ; besides which there are several smaller openings in the tendinous insertion of this muscle for the transmission of the perforating arteries and their companion veins. The pectineal and adductor muscles bend the thigh on the pelvis, rotate it outwardly, and act as powerful adductors. MUSCLES ON THE BACK OF THE THIGH. The Bi'ceps Flex'or, 3 as expressed by the name, arises by two heads. The long head arises by a tendon, common to it and the semitendinous muscle, from the back part of the tuberosity of the ischium ; the short head arises from the lower two-thirds externally of the asperous ridge of the femur. The fleshy fasciculi terminate in an aponeurosis narrowing into a stout tendon, which is inserted into the head of the fibula. From the tendon of insertion proceed two processes, of which one is inserted into the head of the JilfTa, and the other is continuous with the crural fascia. v The Semiten'dinous muscle 4 arises, in common with the tendon of the long head of the biceps flexor, from the tuberosity of the ischium, and descends upon the inner back part of the thigh. Just below the middle of the latter its fleshy belly ends in a long tendon, which proceeds to be 1 M. adductor brevis; m. a. femoris culi adductoris tricipitis ; m. ischio-femo- secundus ; caput breve m. ad. tricipitis ; ralis. m. ad. secundus ; m. subpubio-femoralis. 3 M. biceps femoris, or flexor cruris ; 2 M. adductor magnus ; m. a. femoris m. ischio-femoro-peronealis. tertius et quartus; caput magnum mus- 4 M. semitendinosus ; m. ischio-praa- tibialis; m. seminervosus. THE MUSCULAR SYSTEM. 251 inserted into the inner side of the tibia below its tuberosity and beneath the insertion of the gracilis tendon FIG. 174. The semitendinous, gracilis, and sartorius muscles arise from remote and nearly equidistant points of the hip bone, and converge to be inserted into the same point of the tibia. Acting together, they cross the leg upon the opposite thigh. The Semimem'branous muscle, 1 situated on the inner side of the preceding muscle, arises from the back part of the tuberosity of the ischium by a broad tendon, which expands into an aponeurosis. From this a fleshy belly, composed of short fasciculi, proceeds to another aponeurosis narrowing into a cord- like tendon, which is inserted into the inner side of the head of the tibia. The tendon of insertion gives off processes to the back part of the capsular ligament of the knee joint and the fascia investing the popliteal muscle. The biceps flexor, semitendinous, and semimembranous muscles are all flexors of the leg upon the thigh. The tendon of insertion of the biceps is named the outer ham string ; the corresponding tendons of the semitendinous and semi- membranous muscles, the inner ham strings, The space included by the ham strings is the poplite'al region 2 or the ham. 1 M. semimembranosus ; m. ischio-poplito-tibialis. 2 Popliteal fossa; fossa genu; hock; hoff; garetum; ignys; suffrago; hollow of the knee. MCSCLES OF THE BACK OF THE RIGHT BUTTOCK AND THIGH. 1, middle gluteal muscle; 2, great gluteal muscle; 3, external vastus, covered by the femoral fascia; 4, long head of the biceps flexor; 5, its short head ; 6, semitendinous, and 7, semimembran- oxis muscles ; 8, gracilis muscle ; 9, inner border of the great adductor; 10, lower extremity of the sar- torius muscle; 11, popliteal space; 12, gastrocne- mius muscle. 252 THE MUSCULAR SYSTEM. MUSCLES OF THE FRONT AND OUTER PART OF THE LEG, AND UPPER PART OF THE FOOT. The Anterior Tib'ial muscle 1 arises from the upper two-thirds of the FlG 175 outer part of the tibia, from the in- terosseous membrane and the crural fascia. Its fleshy belly descends the leg and ends in a flat tendon, which passes beneath the annular ligament of the ankle to the inner side of the foot, where it is inserted into the internal cuneiform bone and the base of the metatarsal bone of the great toe. This muscle flexes the foot. The Long Exten'sor of the Toes 2 arises from the head of the tibia, the upper three-fourths of the length of the fibula, and from the interosseous membrane and crural fascia. Its fleshy fasciculi termin- ate in a tendon, which descends beneath the annular ligament of the ankle and divides into four tendons diverging to the four lesser toes, over the backs of which they expand in the manner of the ex- tensor tendons of the fingers. MUSCLES OF THE FRONT OF THE LEG AND BACK OP THE FOOT. 1, tendon of the rectus muscle of the thigh ; 2, subcutaneous inner surface of the tibia ; 3, anterior tibial muscle; 4, long extensor f the toes; 5, long extensor of the great toe; 6, anterior peroneal muscle ; 7, long peroneal muscle ; 8, short peroneal muscle ; 9, borders of the soleus ; 10, bor- der of the inner belly of the gastrocnemius ; 11, short flexor of the toes, beneath the tendons of the long flexor. This muscle aids the anterior tibial The Anterior Perone'al muscle 3 arises from the fibula, below the preceding, and ends in a tendon, which descends beneath the annu- lar ligament to be inserted into the base of the last metatarsal bone, in flexing the foot. 1 M. tibialis anticus ; m. flexor tarsi- tibialis; m. tibio-supertarseus ; m. tibio- supra-metatarseus ; m. hippicus ; m. ca- tenae. 2 M. extensor longus, or communis di- gitorum pedis ; m. cnemodactylgeus. 3 M. peroneus anticus, or tertius ; m. tarsi-fibularis ; m. pereneo-supra-meta- tarseus brevis ; m. nonus Vesalii. THE MUSCULAR SYSTEM. 253 The Extender of the Great Toe 1 lies between the anterior tibial and long extensor muscles. It arises from the lower two-thirds of the fibula and the interosseous membrane, and ends in a flat tendon, which descends beneath the annular ligament of the ankle and expands on the back of the great toe, being finally inserted into its last phalanx. The Short Extensor of the Toes 2 is situated on the back of the foot. It arises from the outer side of the calcaneum and the annular ligament of the ankle, and forms four fleshy bellies, each of which ends in a ten- don proceeding to join the extensor tendons of the great toe and the succeeding three toes. The Long Perone'al muscle, 3 situated at the outer part of the leg, arises from the upper two-thirds of the fibula, from the contiguous inter- muscular partitions and the crural fascia. Its fleshy belly ends in a long tendon, which descends through a groove at the back of the external ankle, then proceeds along another groove on the outer surface of the calcaneum, and turns beneath the sole of the foot. Entering the groove of the cuboid bone, it passes obliquely forward and inward to be inserted into the base of the first metatarsal bone. In the course of the tendon, it twice changes its direction; once at the lower end of the fibula, and again at the cuboid bone. In these positions it acquires a thickened fibro-eartilagmous character, and at the turn of the cuboid bone not unfrequently has a sesamoid bone devel- oped in it. The grooves behind the external ankle and the outer face of the calcaneum, through which the tendons pass, are converted by fibrous bands into canals lined with synovial bursas. The groove of the cuboid bone is converted into a canal by the long plantar ligament, and is likewise provided with a synovial bursa. The Short Perone'al muscle 4 arises from the lower half of the outer surface of the fibula, and the contiguous intermuscular partitions. Its fleshy belly terminates in a tendon, which descends, in company with that of the preceding muscle, behind the external ankle, and passes along the outer surface of the calcaneum to be inserted into the base of the last metatarsal bone. The long and short peroneal muscles extend the foot, and are the antagonists of the anterior peroneal and tibial muscles. 1 M. extensor proprius pollicis, or hal- or maximus ; m. pereneo-sub-tarseus ; lucis ; m. e. longus hallucis. m. extensor tarsi-fibularis longior. M. extensor brevis digitorum pedis ; 4 M. peroneus brevis, secundus, or 111. pedicus. medius ; m. semifibulaeus ; m. extensor 3 M. peroneus longus, primus, posticus, tarsi-fibularis brevior. 254 THE MUSCULAR SYSTEM. FIG. 176. MUSCLES ON THE BACK OF THE LEG. The Tri'ceps Su'ral muscle, 1 as expressed in the name, has three heads, the fleshy bellies of which form the calf of the leg. 2 Two of the bellies are superficial, and constitute the gastrocne- mius muscle, while the third is under cover of the former, and is named the soleus muscle. The Gastrocne'mius muscle 3 arises tendin- ously just above the condyles of the femur; and its two fleshy bellies descend in contact with each other to terminate in a strong apo- neurosis. The Sole'us muscle 4 arises from the head and half the length of the fibula, from the oblique line of the tibia just below the popliteal mus- cle, and from the inner border of the tibia for several inches below the latter. From this origin the fleshy fasciculi descend obliquely, and terminate in an aponeurosis facing the muscle posteriorly. The aponeuroses of the gastrocnemius and soleus muscles conjoin in the formation of the strongest cord-like ten- don of the body, named the tendon of Achilles, 5 which descends to be inserted into the lower part of the tuberosity of the calcaneum. Between the upper part of the tuberosity and the tendon a synovial bursa is interposed. The. triceps sural muscle by drawing on the calcaneum elevates the body upon the toes, as in walking. Dancing, jumping, or other active movements of the kind tend greatly to increase its size. SUPERFICIAL MUSCLES ON THE BACK OF THE RIGHT LEG. 1, bi- ceps flexor; 2, tendons of the Bemitendinous, semimembra- nous, gracilis, and sartorius muscles; 3, popliteal space; 4, gastrocnemius; 5, eoleus; 6, tendon of Achilles; 7, calca- neum ; 8, tendons of the long and short peroneal muscles passing behind the outer an- kle ; 9, tendons of the posterior tibial muscle and long flexor of the toes passing behind the inner ankle. 1 M. extensor pedis ; m. triceps surae ; m. surae, or suralis ; m. extensor tarsi magnus. 2 Sura ; gastrocnemium. 3 M. gastrocnemius externus ; m. ge- mellus surae ; m. gemellus externus and internus ; m. bi-femoro-calcaneus. 4 M. gastrocnemius internus ; m. tibio- calcaneus ; m. tibio-pereneo-calcaneus. 5 Tendo Achilles ; Achilles' tendon ; chorda, or funis Hippocratis ; corda magna ; nervus latus. THE MUSCULAR SYSTEM. 255 The Plantar muscle 1 arises from the femur just above the outer con- dyle, and from the contiguous portion of the capsular ligament of the knee joint. Its short, fleshy belly ends in a long, delicate tendon, which, after passing between the gastrocnemius and soleus muscles, descends at the inner margin of the tendon of Achilles to be inserted, in company with it, into the calcaneum. This muscle corresponds to the long palmar muscle of the forearm, but it is only in some of the lower animals tha^jts tendon joins the plan- tar aponeurosis. FIG. 177. The Poplite'al muscle 2 is situated immediately below the knee joint posteriorly, and is invested with a thin aponeurosis connected with the tendon of the semimembranous muscle. It arises by a tendon from the groove on the outer side of the external condyle of the femur, beneath the contiguous lateral ligament of the knee joint, and expands upon the triangular surface at the upper part of the tibia, into which it is inserted. The tendon of origin is attached to the external semilunar nbro-cartilage, and is invested by the synovial membrane of the knee joint. The popliteal muscle flexes the leg and rotates it inwardly. DEEP MUSCLES OF THE BACK OF THE LEG. 1, femur ; 2, posterior portion of the capsular ligament ; 3, tendon of the semimembranous muscle in- serted into the head of the tibia, and giving an offset to the capsular ligament; 4, 5, internal and exter- nal lateral ligaments; 6, popliteal muscle ; 7, long flexor of the toes ; 8, posterior tibial muscle; 9, long flexor of the great toe ; 10, 11, long and short peroneal muscles; 12, tendon of Achilles; 13, tendons of the long flexor of the toes, and the posterior tibial muscle, just before passing beneath the internal annu- lar ligament. The Long Flexor of the Toes, 3 situated under cover of the muscles of the calf, and below the popliteal muscle, arises from the tibia to within a short distance of its lower extremity. The fleshy fasciculi proceed obliquely to a tendon, which descends behind the inner ankle and turns beneath the concavity of the calcaneum into the sole of the foot. Receiving a process from the tendon of the long flexor of the 1 M. plantaris ; m. p. gracilis ; m. exten- sor tarsi minor ; m. gracilis surse ; m. tibi- alis gracilis ; m. femoro-calcaneus brevis. 2 M. poplitaeus ; m. sub-poplitaeus ; m. femoro-popliti-tibialis. 8 M. flexor longus digitorum ; m. f. 1. d. pedis profundus perforans ; m. flexor tertii internodii digitorum pedis ; m. pe- ronodactylius. 256 THE MUSCULAR SYSTEM. great toe, it then divides into four tendons, which proceed forward and pass through perforations in the tendons of the short flexor of the toes, finally to be inserted into the bases of the last phalanges of the four lesser toes. The Long Flexor of the Great Toe, 1 situated at the outer side of the preceding muscle, arises from the lower two-thirds of the fibula, and ends in a tendon which descends behind the inner ankle to the concavity of the calcaneum. Turning forward in the sole of the foot, after giving, off a process to the tendon of the long flexor of the toes, it proceeds to be inserted into the base of the last phalanx of the great toe. The Posterior Tib'ial muscle, 2 situated between the preceding pair of muscles, arises from the surface of the interosseous membrane and the contiguous borders of the tibia and fibula. Its fleshy fasciculi end in a tendon which descends through a groove behind the inner ankle, then proceeds beneath the calcaneum to be inserted into the scaphoid bone and the base of the first metatarsal bone. This muscle is an extensor of the foot. MUSCLES OF THE SOLE OF THE FOOT. The Short Flexor of the Toes 3 is covered by the middle portion of the plantar fascia, from which and the inner tubercle of the calcaneum. it has its origin. Proceeding forward, it terminates in four tendons, which, after being perforated for the passage of the tendons of the long flexor of the toes, are inserted into the bases of the second phalanges of the latter. The Accessory Flexor 4 arises from the concavity and under part of the calcaneum, and is inserted into the tendon of the long flexor of the great toes, to which, as the name indicates, it is an accessory head. The Lumbrical muscles 5 are four fleshy fasciculi like those of the hand. They arise from the tendons of the long flexor of the toes, and 1 M. flexor longus pollicis pedis ; m. perforates ; m. flexor secundi internodii f. 1. hallucis pedis. digitorum pedis. 2 M. tibialis posticus; m. nauticus; m. 4 M. flexor accessorius ; m. accessorius extensor tarsi-tibialis ; m. tibio-sub-tar- flexoris longi digitorura pedis ; massacar- seus. nea Jacobi Sylvii; caro quadrata Sylvii ; 3 M. flexor brevis digitorum pedis ; m. caro accessoria ; m. plantarus verus. f. b.d. p. perforatus ; m. f. sublimus d. p. 5 M. lumbricales pedis. THE MUSCULAR SYSTEM. 257 proceed to be inserted into the corresponding extensor tendons and the bases of the first phalanges of the toes. The Abduc'tor of the Great Toe, 1 the most superficial of the muscles on the inner side of the sole of the foot, arises from the calcaneum, the scaphoid and internal cuneiform bones, and the plantar fascia, and pro- ceeds forward to be inserted by a tendon into the base of the first phalanx of the great toe. FIG. 178. FIG. 179. MUSCLES OF THE SOLE OF THE FOOT. 1, calcaneum; 2, posterior extremity of the plantar fascia; 3, ab- ductor of the great toe; 4, abductor of the little toe ; 5, short flexor of the toes ; 6, tendon of the long flexor of the great toe; 7, insertion of the lumbrical muscles, which are seen to the right of the tendons of the short flexor of the toes. DEEP MUSCLES OF THE SOLE. 1, attachment of the plantar fascia and short flexor of the toes ; 2, ac- cessory flexor; 3, tendon of the long flexor of the toes; 4, tendon of the long flexor of the great toe; 5, two heads of the short flexor of the same ; 6, ad- ductor of the great toe; 7, flexor of the little toe; 8, transverse muscle ; 9, interosseous muscles ; 10, course of the tendon of the long peroneal muscle, seen through the long plantar ligament. The Short Flexor of the Great Toe 2 arises, as a pair of fleshy bellies, from the cuboid and outer two cuneiform bones, and proceeds forward to be inserted tendinously into the base of the first phalanx of the great toe. Between the two bellies of this muscle lies the tendon of the long flexor. The Adduc'tor of the Great Toe 3 arises from the cuboid bone and the 1 M. abductor pollicis pedis ; m. calco- sub-phalangeus pollicis. 2 M. flexor brevis pollicis, or hallucis pedis. 3 M. adductor pollicis, or hallucis pe- dis ; m. antithenar ; m. metatarso-sub- phalangeus pollicis. IT 258 THE MUSCULAR SYSTEM. bases of the third and fourth metatarsal bones, and is inserted tendinously into the base of the first phalanx of the great toe. The Transverse muscle 1 consists of several fasciculi arising from the heads of the second, third, and fourth metatarsal bones, and inserted tendinously into the base of the first phalanx of the great toe. The sesamoid bones are inclosed within the insertion of the muscles into the base of the first phalanx of the great toe, and move upon the head of the metatarsal bone during the action of those muscles. The Abduc'tor of the Little Toe 2 arises from the outer tubercle of the calcaneum, the plantar fascia, and the base of the last metatarsal bone, and proceeds forward to be inserted into the base of the first phalanx of the little toe. The Flexor of the Little Toe 3 arises from the long plantar ligament and the base of the last metatarsal bone, and proceeds to be inserted into the base of the first phalanx of the little toe. THE INTEKOSSEOUS MUSCLES OF THE FOOT. The Dorsal Interos'seous muscles occupy the metatarsal intervals, with which they correspond in number. They arise from the adjacent sides of the metatarsal bones, and are inserted tendinously into the extensor tendons and bases of the first phalanges of the middle three toes. The first dorsal interosseous muscle is inserted on the inner side of the second toe, and acts as an adductor ; while the others are inserted into the outer side of the second, third, and fourth toes, and act as abductors. The Plantar Interos'seous muscles, three in number, lie on the outer three metatarsal bones and arise from their inner side, from whence they proceed forward to be inserted into the extensor tendons and bases of the first phalanges of the corresponding toes, to which they act as adduc- tors. 1 M. transversalis, or transversus pe- 2 M. abductor minimi digiti pedis. dis ; m. scandularius ; m. metatarso-sub- 3 M. flexor minimi digiti pedis. phalangeus. CHAPTER Y. ANATOMICAL ELEMENTS OF SEROUS AND MUCOUS MEMBRANES, THE GLANDS, THE LUNGS, AND THE SKIN. FIG. 180. SEROUS and mucous membranes, glands, the lungs, and the skin pos- sess common anatomical elements, which hold the same relative position with one another. These elements are as follows : a cellular layer, a basement membrane, a fibrous layer, and blood-vessels, lymphatics, and nerves. The Cellular layer 1 occupies the free surface of the structures above mentioned, and is named epithelium, 2 except on the skin, where it is called epider'mis, It consists of from one to many layers of cells, of different forms in the Various StrUC- DIAGRAM EXHIBITING THE RELATIVE POSITION OF THE COMMON ANA . . , . , rp, . TOMICAL ELEMENTS OF SEROUS AND MUCOUS MEMBRANES, THE GLANDS LlCated. ineepi- THE LUNGSj ANJ) THE 8KIN 1? epithelium, secreting cells, or epi- thelium Of the UriniferOUS dermis, as the case may be, composed of nucleated cells, and occu- ,11 f fVi V' 1 Pying the free surface of the structure mentioned; 2, basement e ^ S layer, in this and other diagrams purposely represented much presents an example Of a thicker than natural, in comparison with the other layers; :j. Invpr of pplls thp fit> rous layer, in which the arteries and veins (4) terminate in a capillary net-work. serous membranes, from one to four layers ; the mucous membrane of the stomach, several layers in different stages of development; the mucous membrane of the mouth, many layers; and the epidermis, above all similar structures, presents the greatest number of layers of cells. From difference in form, and other peculiarities, the epithelium is 1 Implying its composition of organic cells, and not to be confounded with areolar or connective tissue, which, until within a comparatively short period, was called cellular tissue. 2 Epitelium ; endepidermis. (259) 260 EPITHELIUM. divided into the following varieties: squamous epithelium; pavement epithelium ; spheroidal, polyhedral, and irregular epithelium ; columnar epithelium ; and ciliated epithelium. The Squa'mous epithelium 1 consists of many layers of broad, thin scales, which are flattened cells, containing a nucleus and a few scattered coarse granules. This variety forms the epithelium of the mucous membrane of the mouth, lower part of the pharynx, oesophagus, vagina, vulva, entrance of the urethra, conjunctiva, and entrance of the nose. FIG. 181. Fia. 182. SQUAMOUS EPITHELIUM, consisting of nucleated PAVEMENT EPITHELIUM, from a serous membrane, cells transformed into broad scales. From the mu- highly magnified, and seen to consist of flat, six- cous membrane of the mouth, highly magnified. sided nucleated cells. The Pavement epithelium 2 consists of from one to four layers of flat nucleated cells, usually six-sided, and regularly arranged like the blocks of a pavement, whence the name. Such an epithelium forms the free surface of the serous membranes, including the synovial membranes and the lining membrane of the vascular system ; it likewise constitutes the epithelium of the uriniferous tubules, sweat glands, and air-cells of the lungs. The Spheroidal, polyhedral, and irregular epithelium are modifica- tions of the same form. The spheroidal epithelium constitutes the secreting cells of the salivary glands and pancreas, but they are more or less modified into the polyhedral form by mutual pressure. The secret- ing cells of the liver are polyhedral, but more or less irregular. The epithelium of the excretory duct of the kidney and of the bladder exhibits singularly irregular forms of cells. The Columnar epithelium 3 consists of a single layer of six-sided col- umnar cells, with a conical prolongation. The broad end of the cells is free, the sides are in contact, and the narrow end is imbedded in a pro- geny of developing cells. The columnar cells are more delicate than most other kinds, are provided with granular contents, and possess a large oval nucleus. Such an epithelium is found on the mucous mem- 1 Scaly, lamellar, tabular, flattened, 3 Cylinder, prismatic, conical, or tu- pavement, or tesselated epithelium. bular epithelium ; simple columnar epi- 2 Tesselated epithelium. thelium. EPITHELIUM. 261 brane of the stomach, small and large intestines ; in many glands, as the tubular glands of the intestines ; in the ducts of most glands ; in the gall-bladder ; and in the urethra. FIG. 183. FIG. 184. ; POLYHEDRAL EPITHELIUM, exemplified by secret- ing cells of the liver. The arrangement is ideal. 1, space occupied by a blood-vessel; 2, isolated cells. DIAGRAM OF A VERTICAL SECTION OF MUCOUS MEM- BRANE OF THE SMALL INTESTINES, highly magnified. 1, fibrous layer, in which the blood-vessels are dis- tributed; 2, basement membrane ; 3, young nucle- ated cells ; 4, layer of columnar cells ; 5, 6, cells in the act of being shed or thrown off; 7, free ends of the columnar cells, exhibiting their six-sided form ; 8, a single columnar cell, exhibiting its actual form at all parts The Cil'iated epithelium 1 dif- fers from the preceding, in the cells possessing at their free extremity a number of exceedingly fine filament- ous appendages, named, from their resemblance to the eyelashes, cij'ia. 2 These are processes of the cell wall of uniform size, and during life are endowed with the power of rapidly and incessantly moving backward and forward. This vibratory movement is always uniform and wave-like in a long series of cells, so that when seen over a surface of some extent, it reminds one of the movement of a field of grain under the influence of a gentle breeze. The vibration of the cilia produces currents in the liquids in contact with them, and thus conveys the liquids from one posi- tion to another. The cil'iary motion even continues for some time after the cells have been scraped from the membrane of which they form a part ; and the resistance of the liquid to the vibrating cilia of the de- tached cells causes these to move freely about, as if endowed with volun- tary power. A ciliated epithelium exists on the mucous membrane of the upper part of the nose and pharynx, the tympanum and Eustachian tube, the larynx, trachea, bronchi and their ramifications, and the cavity of the uterus and Fallopian tubes. The epidermis will be particularly described in the account of the skin. 1 Vibratile epithelium. 2 Vibratile cilia; vibrillse. 262 BASEMENT MEMBRANE. FIG. 185. DIAGRAM OF A VERTICAL SECTION OF THE BRONCHIAL MUCOUS MEM- BRAXE, highly magnified. 1, col- umnar ciliated epithelial cells; 2, cilia; 3, nuclei; 4, young cells; 5, basement membrane; 6, fibrous layer. works of elastic tissue. Basement membrane 1 is a thin, homogeneous layer, or one devoid of visible structure, supporting the cellular layer of the serous and mucous membranes, the skin, and other organs above mentioned ; and resolving itself beneath into the fibrous layer. In some instances it is very distinct and readily observed, as in the uriri- iferous tubules; in others it certainly exists, but is not so easily demonstrable as in the mucous membranes and skin ; and in some cases it is so difficult to detect, that in such positions by many its existence is denied, as in the liver. The fibrous layer, 2 situated beneath and supporting the basement membrane and epi- thelial layer, is composed of an intertexture of bundles of fibrous tissue mingled with fine net- This layer, for the most part, is absent in the liver, exists in very small quantity in the kidneys, is well developed in other glands, and in the serous and mucous membranes, and reaches its greatest extent in the formation of the dermis. The fibrous layer gives strength and stability to the other structures, and in it, or in a correspond- ing position if it is absent, the blood-vessels, lymphatics, and nerves are distributed, and never penetrate the basement membrane or epithelial layer. The blood-vessels form capillary nets, which have the closest meshes in the glands, mucous membranes, lungs, and skin. The lym- phatics are more numerous in these than any other structures. The nerv- ous supply is also abundant. Most or perhaps all the structures, whose elements have been described above, lose the superficial portion of their cellular layer from time to time, which is as constantly renewed. The process is not very evident in the cellular layer of glands, nor is it much more clear in the pave- ment epithelium of serous membranes and allied structures. The colum- nar epithelium, including its ciliated variety, exhibits strong evidences of the process, but it is most strikingly obvious in the squamous epithelium and the epidermis. In a vertical section of the mucous membrane of the mouth, the cells of the epithelium in contact with the basement membrane are observed to be comparatively soft, polyhedral from mutual pressure, and of uniform 1 Structureless, or amorphous membrane ; homogeneous layer ; membrana inter- media, or limitans ; primary or limitary membrane. 2 Membrana propria. SEROUS MEMBRANES. 263 diameters ; the layers of cells in succession increase in breadth at the ex- pense of their depth ; and the superficial cells form the broad thin scales char- acteristic of the squamous epithelium, of which G shreds or flakes are con- stantly being cast off while they are renewed from be- neath. j ,. -, ,. f DIAGRAM OP A SECTION OF THE MUCOUS MEMBRANE OF THE MOUTH, L highly magnified. 1, fibrous layer, in which the blood-vessels are the muCOUS membrane Of distributed; 2, basement layer; 3, young cells of the epithelium; the Small intestine, SeV- 4, older cells transformed into scales; 5, shred of epithelium cast off; 6, a single scale, seen on its broad surface; 7, a similar scale, eral layers of cells are seen in its thickness. observable, in the deeper part of the epithelium, in various stages of development, from the simple spheroidal form to the columnar cells, which always exist in a single layer at the free surface of the epithelium. How, or whether these columnar epithelial cells are shed, has not been positively determined. On several occasions, the author, in some examinations of the structure of the small intestine in the lower animals, has observed isolated columnar cells ap- parently crowded from their position by pressure laterally and beneath, as represented in figure 184. Perhaps from these instances we may not be wrong in suspecting that the older or effete cells are thus pushed one after another from their place by the more vigorous cells around and the developing ones beneath. SEROUS MEMBRANES. The Serous membranes, 1 named from the character of the liquid bathing their free surface, line cavities of the body having no exterior communication, and are therefore closed sacs. They serve to lubricate organs which move upon one another, and in many instances form folds, which retain the organs in their position, and from this circumstance, in some cases are named ligaments, as in the case of the suspensory liga- ment of the liver. The serous membranes are as follows : 1. The two pleurae lining the sides of the thorax and investing the lungs. 2. The pericardium surrounding the heart. 3. The peritoneum lining the cavity of the abdomen and reflected upon its viscera. 1 Membrause serosae. 264 SEROUS MEMBRANES. 4. The vaginal tunic of each testicle. 5. The arachnoid membrane of the brain and spinal cord. 6. The lining membrane of the ventricles of the brain. 7. The synovial membranes of the joints. 8. The synovial bursa3. 9. The lining membrane of the vascular system. \ JX). The lining membrane of the labyrinth. In the relation of the serous membranes to the contiguous parts, one portion is applied upon the interior surface of the cavity it lines, and another portion is reflected upon the organ or organs contained within the cavity. The former is named its parietal or lining portion ; the latter, its reflected or vis'ceral portion, From this arrangement, the organs are not contained within the cavity of the serous sacs, but are excluded by the membrane being reflected over them. The outer surface of the serous membrane is attached to the neighbor- ing parts by connective tissue, named from its position sub-serous tissue ; the inner surface is free, smooth, shining, and moistened with a serous liquid elaborated by the membrane itself. The free surfaces of the parietal and reflected portions of the serous membrane come into contact, so that the organs easily and smoothly move upon one another, and against the walls of the cavity containing them ; the movement being facilitated by the liquid lubri- cating the surfaces. The liquid of the serous cavities resembles the serum of the blood in appearance and FIG. 187. only attached portion of the organ, all others being free ; 3, side of the thorax; 4, diaphragm; 5, parietal pleura; 6, pulmonary or reflected pleura ; 7, cavity of the pleura. DIAGRAM EXHIBITING THE RELA- TION OP A SEROUS MEMBRANE, THE PLEURA, TO THE ORGAN IT INVESTS AND THE CAVITY IT LINES. 1 , lung ; ... , , . 2, root of the lung, which is the composition, but in some instances is more viscid, as in the case of that of the synovial membranes. The sub-serous connective tissue usually at- taches the serous membranes closely to the adjacent parts. In the case of the arachnoid membrane attached to the pia mater, it consists of scattered bands, the sub-arach/noid tissue, with the intervals occupied by a liquid like that contained within the cavity of the arachnoid membrane. When serous membranes invest the interior surface of fibrous mem- branes, as in the case of the arachnoid and dura mater, and the serous and fibrous pericardium, the two together are often named fibro-serous membranes. The serous membranes are thin, transparent, and colorless, moderately SEROUS MEMBRANES. 265 strong, extensible and elastic. In structure they consist of one or more layers of pavement epithelium composed of six-sided cells ; a thin base- ment membrane, and a layer of fibrous tissue with mingled elastic fibres. The blood-vessels are comparatively few, and form capillary nets, with wide meshes, in the fibrous layer. Numerous lymphatics and fine plexuses of nerves also pervade the latter, though the serous membranes are quite devoid of sensibility in a condition of health. The liquid of serous membranes consists of water, with from one to six percentage of albumen, chloride of sodium, and phosphate of soda and lime. Syno'vial membranes 1 line the interior of the joints, but do not cover the articular cartilages. Their lubricating liquid, named syno'via, 2 is more viscid than the liquid of other serous membranes. At the margin of the articulations the membrane frequently forms one or more folds containing fat, and named synovial fringes. 3 These are yellow or red- dish yellow, more vascular than other portions of the synovial membrane, and apparently more active in the production of synovia. Syno'vial bur'sae 4 occur where muscles or tendons move upon bones, fibro -cartilages, or ligaments, or frequently upon one another. In many positions they appear as simple, flattened spheroidal sacs, tightly adhe- rent by one side to the moving organ, and by the other side to the part against which the organ moves. Instances of this kind are seen in the bursa beneath the deltoid muscle, and that between the insertion of the biceps flexor tendon and the tuberosity of the radius. When tendons move through grooves of bones, or beneath annular or vaginal ligaments, the synovial bursa 5 lines the groove or canal and is thence reflected upon the tendons. In the vicinity of joints the bursae often communicate with their cavity. In positions in which a number of tendons move upon one another, as in the case of the flexor tendons in the vicinity of the wrist, a highly extensible, fibro-elastic membrane 6 is folded around and among them, which appears to have the same function as the synovial bursaB, but presents no trace of an epithelium. Beneath the skin also in certain positions, as between that of the elbow and the olecranon, or that of the knee and the patella, pouches 7 exist, apparently of the nature of 1 Capsulae synoviales. 4 Bursae mucosae ; b. m. vesiculares ; 2 Mucilago ; humor, unguentum, smeg- b. or capsulae synoviales ; sacci mucosi ; ma, axungia, gluten, or humidum nativum synovial crypts or follicles; blennocys- articulorum; hydrarthrus; arthrohydrine. tides ; vesicrc unguinosre tendinum. 3 Synovial glands of Havers ; Haver- 5 Vaginas synoviales or mucilaginosae. sian glands; glandulae articulares; syno- 6 Bursae mucosae tendinosae. vial fimbriae ; plicae synoviales, adiposse, B. m. subcutanese. or vasculosae ; ligamenta mucosa. 266 MUCOUS MEMBRANES. synovial bursaa. These have a ragged-looking internal surface devoid of an epithelium. MUCOUS MEMBRANES. Mucous membranes, though possessing common physical or anatomical elements, like the serous membranes, differ in most other respects. They line internal cavities and passages communicating with the exterior, together with various receptacles and glandular ducts opening on the surfaces of the former. They never form completely closed sacs, as the serous membranes, and are all continuous with one another and the skin. Habitually exposed to the contact of materials foreign to their structure, such as food, air, dust, the secretions and excretions of glands, their free surface is bathed with a viscous liquid named mucus, which is usually more consistent than the liquid of serous membranes. Mucous membrane lines the cavity of the nose and its communicating sinuses, the front of the eye and the lachrymo-nasal duct, the tympanum, mastoid sinuses and Eustachian tube, the mouth, pharynx, oesophagus, stomach, and intestines, the larynx, trachea, bronchi and their ramifica- tions, the salivary, pancreatic, and bile ducts, and the gall-bladder, the pelvis of the kidneys, ureters, urinary bladder and urethra, the semi- nal ducts and vesicles, the vagina, uterus, and Fallopian tubes, and the ducts of the mammary glands. From their isolation, all these mu- cous membranes together are divided into three groups, generally desig- nated as the gastro-pulmonary, genito-urinary, and mammary mucous membranes. At the edges of the eyelids, nostrils, mouth, anus, vulva, urethra, and orifices of the milk ducts, the mucous membranes become continuous structures with the skin. All the mucous membranes possess a free surface formed of an epithe- lium resting on a basement membrane, beneath which is a fibrous layer adhering to the contiguous parts by connective tissue, named from its position the submucous tissue. 1 In the hollow viscera the latter forms an abundant and distensible layer, permitting considerable enlargement of the visceral cavities, as in the case of the stomach and urinary blad- der. In contraction of organs lined with mucous membrane this be- comes rugose, or thrown into folds, which are effaced on distention. These folds, however, should not be confounded with others of a perma- nent character existing in some of the mucous membranes, as for instance, the val'vulae conniven'tes of the small intestine. The mucous membranes are less transparent in general than the serous 1 Textus cellularis submucosus ; tunica cellularis ; fibrous coat ; cellular coat. THE GLANDULAR SYSTEM. 267 membranes ; are more vascular, and are also well supplied with lym- phatics and nerves. They vary from a white, grayish white and pale pink, to dark red, the shade or depth of redness depending mainly on the amount of blood supplied. Excitation heightens their color, and contact with the air favors their permanent redness. Nearly all mucous membranes are abundantly supplied with minute glands imbedded in their fibrous layer or the contiguous submucous tissue, and opening on their free surface. The epithelium of mucous membranes presents most of the varieties of cells which have been described. Those provided with a columnar epithelium are usually softer and more moist than the others. The base- ment membrane and fibrous layers of structure are sufficiently evident in all mucous membranes. Mucus, the material elaborated by the mucous membranes, and appa- rently by many of their glands, is a clear, colorless, transparent, viscid liquid, frequently rendered more or less turbid by cast-off epithelial cells, and isolated nuclear bodies, commonly called mucous corpuscles. It is composed of water, the peculiar organic principle mucosin, and alkaline salts. THE GLANDULAR SYSTEM. The name of Gland has been indiscriminately applied to almost every rounded, massive organ, if it was only supposed to elaborate certain liquid materials from the blood. Thus the liver, which produces the bile, the thyroid body whose office is unknown, the rounded masses situ- ated in the course of the lymphatics, and the pituitary body, a portion of the brain, have all been and yet continue to be called glands. In this confusion of parts with one general name, it is our object at present only to describe those which are commonly distinguished as the true glands. These may be defined to be organs which elaborate from the blood liquid matters poured forth by one or more ducts or orifices open- ing on the surface of the mucous membranes or skin. The material elaborated by a gland is called a secretion, and the same name is given to the act of elaboration. If the secretion is to be rejected from the body as useless, it is also called an excretion. The term secretion is likewise applied to mucus and serum, and to the elaboration of these by their appropriate membranes. In general, the glands may be described as consisting of a tube or series of tubes of basement membrane lined with nucleated cells, and in- vested externally with a fibrous layer in which are distributed the blood- vessels from which the glands elaborate their secretions. The difference 268 THE GLANDULAR SYSTEM. in the complexity and extent of glands depends mainly on the difference in number, length, and arrangement of the tubes. FIG. 188. FIG. 189. SIMPLE GLAND DILATED INTO A POUCH. References as in the preceding figure. DIAGRAM OF TWO SIMPLE TUBULAR GLANDS. The dotted line 1 indicates the glandular epithelium or secreting cells; the thicker continuous line 2, is the basement membrane, and the shaded portion of the figure 3 represents the fibrous tissue in which the blood-vessels are distributed which sup- ply the glands. The simplest form of a gland consists of a short, straight tube, closed at one end, and opening at the other upon the surface of a mucous membrane, as instanced in the tubular glands of the small intestines. The complexity is slightly increased if the tube is dilated into a purse-like pouch, as in the simple sebaceous glands of the skin. If the simple tube or pouch is divided at bottom into two or more similar parts, the complexity is increased according to the number of the latter, as seen in tlie gastric glands, and compound sebaceous glands of the skin. The glandular tube may be rendered complex by becoming more or less elongated and convoluted, as in the case of the sweat glands. If FIG. 190. FIG. 191. FIG. 192. Fig. 190. GLANDS RENDERED SLIGHTLY COMPLEX BY DIVISION AT BOTTOM. References as in figure 188. Fig. 191. INCREASE OF COMPLEXITY OF GLANDS by the addition of similar parts. References as before. Fig. 192. A TUBULAR GLAND rendered complex by becoming elongated and convoluted. Same references. the tube divide and subdivide, and the ultimate branches become elon- gated and convoluted, the gland is rendered complex according to the extent of branching and convolution, as exemplified by the kidneys and testicles. If the glandular tube divide and subdivide, and the terminal branches THE GLANDULAR SYSTEM. 269 dilate into vesicles, a complex arrangement is produced resembling in appearance a bunch of grapes, as represented in the construction of the salivary glands. If, on the other hand, the branching tubes form a net- work, a complex arrangement results such as is seen in the construction of the liver. FIG, 193. FIG. 194. FIG. 195. Fig. 193. GLAND OF COMPLEX FORM; the tubes branching and the terminal ones convoluted and dilated at the extremities. 1, main tube or duct ; 2, branches; 3, convoluted portions dilated at the extremities. Fig. 194. GLAND OF COMPLEX FORM, whose arrangement resembles that of a bunch of grapes. 1, duct; 2, branches ending in vesicles; 3, branch of another lobule. Fig. 195. GLAND OF COMPLEX CHARACTER in which the tubes anastomose, and thus form a net-work 1, duct; 2, net-work of tubes. The glands may be classified according to their structural arrangement, though it should be fairly understood that the different forms are not separated by trenchant characters, but pass by gradations into one another. The principal forms are as follows: the tubular, racemose, convoluted, and reticular glands. The Tubular glands consist of simple, straight or slightly tortuous tubes closed at one end, and opening at the other on the surface of a mucous membrane. They are usually short, of uniform diameter through- out, or slightly dilated toward the closed extremity ; or in the latter po- sition they may divide into several tubular offsets or prolongations. They are imbedded in the fibrous layer of mucous membranes, and in most instances are provided with a columnar epithelium, besides the basement membrane and fibrous coat. Such are the tubular glands of the large and small intestine, the gastric glands, and the tubular glands of the nose and uterus. The Follic'ular glands, intermediate to the former and the succeeding variety, and passing insensibly from one into the other, are composed of one or more purse-like pouches lined with a spheroidal epithelium. When the pouches are numerous, they are usually collected into small groups or lobules opening into a common canal or duct, which conveys 270 THE GLANDULAR SYSTEM. the secretion to the surface of the skin or mucous membrane. To this variety belong the sebaceous glands of the skin, the follicular glands of the root of the tongue, soft palate and pharynx, and the tonsils. The Rac'emose glands are named from their structure resembling in arrangement the appearance of a raceme or cluster of grapes. In the construction of such glands, a tube divides and subdivides, and the smallest branches communicate with vesicular dilatations lined with spheroidal secreting cells, rendered polyhedral from mutual pressure. Groups of vesicles and their associating tubes, which may be compared with the small clusters of a bunch of grapes, are named lobules, In the construction of a large racemose gland, the latter are associated in still larger portions, a number of which together may form the largest divi- sions or lobes of the gland. The simplest racemose glands present a striking resemblance to a bunch of grapes, but the more compound FIG. 196. glands, or those consisting of a number of lobules and lobes, are modified in form from mutual pressure. The commencing vesicles are polyhedral, the lobules and lobes are pyramidal, and the whole are associated, by in- tervening connective tissue, into a more or less solid mass. The tubes or ducts, which collect the secretion from the commencing vesicles, th A RACEMOSE GLAND. 1, duct; 2, lobules composed of the terminal a principal duct, or sometimes several, issuing n P enn g On S0me membrane. The duct or ducts of the racemose glands have fibrous walls lined with mucous membrane, usually provided with a columnar epithelium. A few of the principal ducts in addition are furnished with unstriated muscular fibres. To the racemose glands belong the pancreas, the salivary glands, the lachrymal gland, the labial, buccal, palatine, lingual, pharyngeal, oeso- phageal, and duodenal glands, the tracheal and bronchial glands, the vaginal, prostatic, and urethra! glands. The Convoluted glands are composed of simple or branching tubes, which, at their commencement, are enrolled upon themselves or convoluted into masses. The simplest forms are the sweat glands ; the compound forms are the kidneys and testicles. The only gland exhibiting a reticular arrangement in its intimate structure is the liver. This organ is divided on the surface into several lobes, and these are composed of an aggregation of small and closely UNSTRIATED MUSCULAR TISSUE. 271 adherent polyhedral lobules or acini. Independently of the blood-ves- sels, the acini consist of a net-work of polyhedral glandular cells ; but whether they occupy the interior of tubes of basement membrane, as in other glands, is still a point which remains undetermined to the satisfac- tion of most anatomists. Ducts proceeding from the acini, as in other secretory organs, converge to trunks composed of fibrous walls, with a lining of mucous membrane. The glands are most richly furnished with blood-vessels, which form capillary nets around or among the glandular tubes. They likewise pos- sess numerous lymphatics, and are also supplied with nerves. UNSTRIATED MUSCULAR TISSUE. Most of the hollow viscera, including the vascular system and a few other parts, are provided with muscular layers of a different structure FIG. 197. UNSTRIATED MUSCULAR FIBRE. 1, from the small intestine; 2, from the middle coat of an artery; 3, from a vein. from that already described, and named, in contradistinction, the unstri- ated muscular tissue. 1 The unstriated muscular fibres of the latter consist of fusiform, rounded, or slightly prismoid columns or bands, varying considerably in the proportions of length and breadth in the different organs. They range from tne fa to the T \j of a line in length, are faintly yellowish or colorless, homogeneous, or indistinctly granu- lar, and present no trace of transverse striation. They consist of single, elongated cells, pointed at the extremities, and always provided with a central, oblong oval nucleus. The unstriated muscular fibres are usually associated into fasciculi, and these are arranged into layers or membranes, having a yellowish- brown appearance. These muscular layers are abundantly supplied with blood-vessels and nerves, which have the same general arrangement as in the striated muscles. The unstriated muscular tissue is excited to contraction usually through reflex impressions, but may also be excited by the direct impression of most of the stimuli operating on the striated muscles, except the will. 1 Unstriped, or non-striated muscular tissue or fibres ; smooth muscles, or mus- cular fibres ; organic muscular tissue or fibres ; muscular tissue of organic life. 272 UNSTRIATED MUSCULAR TISSUE. Unstriated muscular tissue constitutes the muscular coat of the stomach, small and large intestine, and the muscular fibres noticed in the mucous membrane of these organs. A thin layer is also found on the gall-bladder and in certain glandular ducts. It forms the muscular coat of the urinary bladder, the walls of the uterus, and a layer to the Fal- lopian tubes, vagina, and urethra. In association with elastic tissue, it composes the middle coat of the blood-vessels and lymphatics, and fur- ther constitutes the muscular structure of the trachea, bronchi and their ramifications. Finally, it forms the dartos layer of the scrotum, and is found in other parts of the skin, especially in the walls of the odoriferous glands of the axillae. CHAPTER YL THE ALIMENTARY APPARATUS. THE Alimentary apparatus consists of the aliment'ary canal, 1 to- gether with a number of accessory organs. The former comprises two divisions, of which one is constituted by the mouth and the organs of deglutition, consisting of the pharynx and resophagus; the other, by the digestive organs, 2 contained within the abdomen, and composed of the stomach and the small and large intestines. The accessory organs are those of mastica'tion, consisting of the teeth, jaws, and appropriate muscles, and the tongue, salivary glands, pancreas, and the liver. THE MOUTH. The Mouth 3 is the space included between the lips in front, the pharynx behind, and the cheeks at the sides. Above, it is bounded by the roof or palate, inclosed by the upper teeth and alveolar arch ; below, is its floor, upon which rests the tongue, included within the lower teeth and alveolar arch. The closed jaws and teeth divide the mouth into two portions : the narrow interval 4 between the lips, cheeks, and the jaws, and the larger cavity within the latter, containing the tongue. The cavity of the mouth, 5 except on the teeth, is everywhere invested with a highly vascular mucous membrane, provided with a squamous epi- thelium. It is also furnished with conical papilla?, for the most part minute and concealed beneath the epithelium, except at the margins of the gums, and more especially on the upper surface of the tongue, where they become conspicuous as the chief organs of taste. The Gums 6 consist of reflections of the oral mucous membrane upon the alveolar arches. They closely adhere to the periosteum beneath, and form circular doublings or collars around the necks of the teeth, with which they are intimately connected. 1 Canalis, tubus, or ductus alimenta- 3 Os ; stoma; cavum oris. rius, ciliarius, digestivus, or intestine- * Vestibulum oris. rum ; digestive canal ; intestinal canal ; 5 Cavum, or spatium oris. primoe vise. 6 Gingivse ; carnicula ; ula. 2 Organon digestionis. 18 (273) 274 THE ALIMENTARY APPARATUS. The Lips 1 are separated by the oral fissure, 2 the extremities of which constitute the oral angles or commissures. 3 Besides the exterior skin, with its subjacent connective tissue and fat, the lips are composed of vari- ous muscles converging to and surrounding the oral fissure, together with FIG. 198. VERTICAL SECTION OF THE FACE AND NECK, THROUGH THE MEDIAN LINE ANTERO-POSTERIORLY, EXPOSING TO VIEW THE NOSE, MOUTH, PHARYNX, AND LARYNX. 1, oval cartilage of the left nostril ; 2, triangular cartilage; 3, line of separation between the two; 4, prolongation of the oval cartilage along the column of the nose; 5, superior meatus of the nose; 6, middle meatus; 7, inferior meatus; 8, sphenoidal sinus; 9, posterior part of the left nasal cavity, communicating with the pharynx; 10, orifice of the Eustachian tube; 11, upper extremity of the pharynx ; 12, soft palate, ending below in the uvula ; 13, interval of the mouth between the lips and jaws; 14, roof of the mouth, or hard palate; 15, communication of the cavity of the mouth with the interval between the jaws and cheek; 16, tongue; 17, fibrous partition in the median line of the latter; 18, genio-glossal muscle; 19, genio-hyoid muscle; 20, mylo-hyoid muscle; 21, anterior half arch of the palate; 22, posterior half arch of the palate; 23, tonsil; 24, 25, floor of the fauces; 26, 27, pharynx; 28 cavity of the larynx; 29, ventricle of the 1 larynx; 30, epiglottis; 31, hyoid bone; 32, 33, thyroid cartilage; 34, tbyro-hyoid membrane; 35, 36, cricoid cartilage; 37, vocal membrane. 1 Sing.: labium; pi.: labia; labrum, cheilos; upper and under lip; anochei- los and catacheilos. 2 Rima, apertura, orificium, or hiatus oris; os; peristonrium. 3 Angles, or commissures of the mouth or of the lips; commissura labiorium ; prostomin. THE ALIMENTARY APPARATUS. 275 the lining mucous membrane and a number of glands. The orbicular muscle borders the oral fissure or orifice of the mouth, and is covered by thin skin, gradually passing into mucous membrane. Between the lips and jaws, in the median line, the mucous membrane forms doublings, named the superior and the inferior labial free 'num. 1 The Cheeks 2 have a composition similar to the lips, and their princi- pal muscle is the buccinator. At their back part they include the ramus of the lower jaw and its muscles, and also, usually between these and the buccinator muscle, a mass of soft adipose tissue. Beneath the mucous membrane of the lips and cheeks there are numer- ous small, rounded, pinkish racemose glands, opening by their ducts into the mouth, and named from their position the labial 3 and buccal glands. 4 Though they are supposed to secrete mucus, their office has not been satisfactorily determined. The Palate, or roof of the mouth, 5 comprises two parts, called the hard and soft palate. The Hard palate 6 is deeply vaulted, and is lined with a smooth mu- cous membrane, except at its fore part, where it is roughened by trans- verse ridges. It is divided by a faintly-marked median line, 7 ending in a small prominence, corresponding with the position of the incisive fora- men. Its osseous basis is formed by the palate plates of the superior maxillary and palate bones, to which the mucous membrane adheres by a dense layer of fibrous tissue, containing numerous small racemose glands, named from their position the palatine glands. 8 The Soft palate 9 is composed of a doubling of mucous membrane, in- closing a fibro-muscular layer, together with many small racemose and follicular glands. It projects as a freely movable partition obliquely downward and backward from the hard palate, between the mouth and posterior nasal orifices. The U'vula 10 is the small, tongue-like appendage projecting from the 1 Fraenum, or frsenulum labii superi- velum palatinum, pendulum, or staphyli- oris et inferioris. num ; velum palati, or pendulum palati ; 2 Genae ; malae. pendulum, or claustrum palati ; pendu- 3 Glandulse labiales. lous veil of the palate. * Glandulae buccales. Uva; uvigena; uvigera; staphyle; 5 Palatum ; fossa palatina ; uraniscos ; columella, or columna oris ; sublingua : hyperoa. tintinnabulum ; gargarlon ; gurgulis ; in- 6 Palatum durum, or stabile. terseptum ; processus, or cartilage uvi- 7 Raphe. fer; pinnaculum fornicis gutturalis; hi- 8 Glandulse palatinse. mas; plestrum; pap of the throat; the 9 Palatum molle, mobile, or pendulum; palate. 276 THE ALIMENTARY APPARATUS. middle of the soft palate, and consists of a pair of muscles inclosed in a pouch of mucous membrane. The Half arches of the Palate are two crescentic folds of mucous membrane, inclosing muscular fasciculi, and diverging from the base of the uvula, on each side of the palate, outward and downward, one to the side of the tongue, the other to the side of the pharynx. The anterior pair inclose the palato-glossal muscles, and together constitute the anterior palatine arch j 1 the posterior pair inclose the palato-pharyngeal muscles, and constitute together the posterior palatine arch, 2 The Fau/ces 3 are the straits or passage leading from the mouth to the pharynx, and correspond with the space included between the palatine arches. The Ton'sils 4 are two glandular organs, about the size and shape of an almond kernel, situated one on each side of the fauces, inclosed in the triangular recess between the half arches of the palate. They are in contact externally with the superior constrictor muscles of the pha- rynx, and move with the contraction of these muscles. Their surface toward the fauces presents a coarsely reticular appearance, due to a number of large orifices communicating with pouches, in the bottom of which the orifices of smaller pouches are visible. They are large com- pound follicular glands of peculiar constitution. Simple follic'ular glands of the same character as the tonsils occupy the floor of the fauces or the root of the tongue, the palate, and the pha- rynx. These are distinguished as rounded prominences of the mucous membrane, with an orifice communicating with the mouth or pharynx. They consist of a purse or bottle-like inflection of the mucous mem- brane, and contain in their thick walls of submucous tissue a number of spheroidal capsules or vesicles resembling in composition the solitary glands of the intestines. The tonsils differ from the simple follicular glands only in their compound form, or, in other words, they consist of an aggregation of such bodies as constitute the glands just named. The recesses of the tonsils and simple follicular glands ordinarily appear to elaborate mucus, which lubricates the fauces in the passage of food. Under the influence of cold, these glandular organs are very sus- 1 Arcus palatinus anticus; a. palato- 4 Sing.: tonsilla ; amygdala; paristh- glossus. mia ; tola ; spongos ; antias ; amphibran- 2 Arcus palatinus posticus ; a. palato- chium ; glandula colli ; almond of the pharyngeus. throat or of the ear. 3 Isthmus of the fauces ; i. faucium ; claustrum gutturis. THE ALIMENTARY APPARATUS. 277 ceptible to inflammation condition their recesses tallow-like matter, which of small, rounded balls. These, when crushed, ex- hale a heavy, disagreeable odor, indicating a source of foul breath, independ- ent of the more ordinary one. The material exam- ined beneath the micro- scope exhibits nothing but squamous epithelial cells, together with some oil globules, and minute, par- asitic, filamentous plants. and chronic enlargement. In the unhealthy frequently become filled with a dirty-white is from time to time expectorated in the form FIG. 199. SECTION OF A FOLLICULAR GLAND FROM THE ROOT OF THE TONGUE. a, epithelium ; 6, papillfe imbedded in the latter ; c, outer part of the thick wall of the gland composed of connective tissue; d, mouth of the gland ; e, its cavity ; /, epithelium lining the lat- ter; g, vesicular bodies resembling the solitary glands of the intestines. Highly magnified. MUSCLES OF THE PALATE AND FAUCES. The Eleva'tor of the Palate 1 is a thin, flat muscle, which arises from the end of the petrous portion of the temporal bone and the contiguous FIG 200. POSTERIOR VIEW OF THE MUSCLES OF THE PALATE AND FAUCES. 1, elevator of the palate, on the left side its origin only remaining; 2, tensor of the palate, winding around the hook of the internal pterygoid process and ending in the soft palate; 3, uvular muscles; 4, Eustachian tube; 5, origin of the palato- pharyngeal and palato-glossal muscles ; 6, part of the origin of the superior constrictor of the pharynx ; 7, external pterygoid muscle. 1 M. levator palati mollis; m. salpingo-staphylinus ; m. s.-s. interims ; m. petro- salpingo-staphylinus ; m. pterygo-staphylinus externus; m. spheno-staphylinus; m. spheno-palatinus ; m. peristaphylinus internus superior ; m. petro-staphylinus. 278 THE ALIMENTARY APPARATUS. portion of the Eustachian tube, and descends at the side of the posterior nasal orifice to expand in the structure of the soft palate. The Ten/sor of the Palate 1 is a narrow muscle arising from the fossa, at the root of the internal pterygoid process, and from the contiguous portion of the Eustachian tube. Descending at the inner side of the pterygoid fossa, it terminates in a tendon which winds around the hook of the internal pterygoid process, and expands into a thin aponeurosis within the soft palate. The TTvular muscle 2 is a fleshy fasciculus arising from the palate spine of the palate bone, and descending in company with its fellow into the uvula. The Pal'ato-glos'sal muscle 3 is situated within the anterior half arch of the palate, extending from the side of the soft palate to the tongue. The Floor of the mouth, included within the lower jaw, is formed by the skin, the mylo- and genio-hyoid muscles, and the mucous membrane reflected from the gum to the under part of the tongue. THE SALIYAEY GLANDS. Opening into the cavity of the mouth there are three pairs of salivary glands, named the parotid, submaxillary and sublingual glands. The Parot'id gland,* the largest of the salivary glands, occupies a po- sition in front of the external ear, reaching a short distance over the masseter muscle. It extends as high as the zygoma, as far down as the angle of the lower jaw, and dips inwardly between the ramus of the latter and the mastoid process to the position of the styloid process and muscles. Passing through its length, we find the external carotid artery and accompanying vein, and, diverging through it in an opposite direc- tion, the facial nerve. The parotid is a large compound racemose gland, consisting of numer- ous polyhedral lobes, closely moulded upon the surfaces with which the gland comes into contact. The lobes are subdivided into lobules, the 1 M. tensor palati mollis ; m. circum- 2 Azygos muscle of the uvula ; m. flexus palati; m. salpingo-staphylinus ; azygos uvulae; m. palato-staphylinus; m. petro-salpingo-staphylinus; m. ptery- m. staphylinus ; m. epistaphylinus; m. go-staphylinus ; m. spheno-salpingo- staphylinus medius. staphylinus; m. peristaphylinus exter- 3 M. palato-glossus : m. constrictor nus or inferior ; m staphylinus externus ; isthmii faucium; m. glosso-staphylinus; m. palato-salpingeus ; m. spheno-pterygo- m. glosso-palatinus. palatinus ; m. tubse novse. * Glandula parotidea; g. adaures; pa- rotis ; animellae ; lacticinia. THE ALIMENTARY APPARATUS. 279 whole being connected together by dense areolar tissue, continuous ex- ternally with that enveloping the gland and adhering to the contiguous parts. The Parot/id duct, 1 about the diameter of a crow-quill, and two inches in length, passes forward from the gland across the masseter muscle, a short distance below the zygoma, and opens into the mouth by perforat- ing the buccinator. Its orifice, somewhat contracted, is indicated by a small prominence opposite the position of the second upper large molar tooth. Usually a detached portion of the gland, named the accessory parotid, 2 rests on the masseter muscle, and communicates by its duct with the main one. The Submax'illary gland, 3 about a third the size of the preceding, and separated from it by a strong process of the. deep cervical fascia, is situated just within and below the base of the lower jaw. It is beneath the mylo-hyoid muscle ; is included below in the curve of the digastric muscle, and externally is covered by the subcutaneous cervical muscle and skin. Its structure is like that of the parotid gland, but its lobes are coarser, its connective tissue much less in quantity, and its attach- ment to the contiguous parts comparatively feeble. The Submax'illary duct, 4 about two inches in length, passes backward, turns over the posterior edge of the mylo-hyoid muscle, and is then di- rected forward between this and the hyo-glossal muscle to the side of the lingual fraenum, where it terminates at the summit of a small promi- nence. 5 An accessory portion of the gland follows the duct a short distance and communicates with it. The Sublin'gual gland, 6 the smallest of the salivary glands, is narrow oblong in shape, and rests on the floor of the mouth, projecting into its cavity as a conspicuous ridge beneath the side of the tongue. It ex- tends from the position of the lingual fraenum to the submaxillary gland, and is in contact with the duct of the latter. The sublingual gland has the same structure as the other salivary glands ; but its lobules are less closely associated. It communicates with the cavity of the mouth by about half a dozen small ducts, 7 which 1 Duct of Steno; ductus Stenonianus: 4 Duct of Wharton; ductus Whartoni- d. salivalis superior. anus ; d. salivalis inferior. . 2 Glandula socia parotidis ; accessory 5 Caruncula sublingualis. gland of the parotid: g. parotis acces- 6 Glandula sublingualis; in part, the soria. glands of Rivinus. 3 Glandula submaxillaris ; g. angula- 7 Ductus Rivini ; d. Waltheriani. ris; g. maxillaris; hypognathaden ; hy- posialaden. 280 THE ALIMENTARY APPARATUS. open upon the ridge indicating its position. Frequently several of the ducts unite into a single one, 1 terminating near to, or in conjunction with, the submaxillary duct. The secretion of the salivary glands, the sali'va, 2 is a colorless liquid of slightly alkaline reaction. It is rendered more or less viscid by the mixture of mucus, and contains a few epithelial scales and so-called mucous corpuscles or free nuclei. The parotid gland is supplied with arteries from the external carotid, the submaxillary gland from the facial, and the sublingual gland from the sublingual artery. The veins terminate in those accompanying the corresponding arteries. The nerves are derived from the contiguous vascular plexuses of the sympathetic, in conjunction with filaments of the trifacial nerve. THE TONGUE. The Tongue 3 is a muscular organ invested with mucous membrane, 4 and ordinarily, when at rest, occupies a position within the arch of the lower jaw. From its freedom of movement it aids in the process of mastication and deglutition, and contributes to articulation in speech ; from the papillae of its surface it constitutes the organ of taste. The posterior part of the tongue attached to the hyoid bone is named its root or base, 5 and that which is attached along the middle to the floor of the mouth is the body. The tip, 6 sides, 7 and upper surface 8 are free, and invested with mucous membrane, which, from beneath the tongue, is reflected to the lower gum. Between the root of the tongue and the epiglottis, the mucous mem- brane forms three folds, named the glos'so-epiglot'tic frae'na ; 9 and be- neath the tip of the tongue a median fold passes to the gum, and is called the lin'gual frae'num. 10 The mucous membrane of the under part of the tongue is thin and translucent, and permits the blood-vessels, especially the ranine veins, and a number of small racemose glands, distinctly to be seen through it. Beneath the tip it forms a slightly elevated median line or raphe' which is continuous with the lingual frsenum. 1 Ductus Bartholini. 6 Dental extremity ; point. 2 Sputum; sputamentum; ptyalon; 7 Margins, rfialon ; spit ; spittle. 8 Dorsum. 3 Lingua ; glossa ; glotta. 9 Glosso-epiglottic ligaments ; frama, 4 Periglottis : membrana, or tunica or frsenula epiglotidis ; ligamenta mem- vaginalis ; involucrum ; cutis ; epider- branacea ; velamenta linguae. mis ; crusta villosae. 10 Frgenum, frcenulum, or vinculum 5 Radix ; hyoid extremity. linguse ; glossodesmus ; filetum. THE ALIMENTARY APPARATUS. 281 The upper surface or back of the tongue 1 is marked along the middle by a slight furrow, 2 which corresponds in position with a thin fibrous par- tition, 3 dividing the organ into symmetrical halves. FIG. 201. VIEW OF THE UPPER SURFACE OF THE TONGUE. 1, 2, V-like row of the circumvallate papilla?; 3, capitate papillae; 4, 5, conical papillae; 6, 0, floor of the fauces, with numerous simple follicular glands; 7, tonsils; 8, summit of the epiglottis; 9, the middle glosso-epiglottic fraenum, with depressions on each side bounded externally by the lateral fraena. Upon the anterior two-thirds of the upper surface of the tongue, the mucous membrane adheres most intimately to the muscular structure beneath, and is especially remarkable from its being densely beset with 1 Dorsum. 2 Linea mediana ; raphe. 3 Septum linguae ; cartilage linguae ; c. mediana ; lingual nbro-cartilage. 282 THE ALIMENTARY APPARATUS. small processes, named, from their function, the papillae of taste. 1 The principal of these are of a composite character, and present three varie- ties, called the circumvallate, capitate, and conical papillae. The Circumval'late papil'lae, 2 the largest of the varieties, and about a dozen in number, form a Y-like row, defining the papillary layer at the posterior third of the tongue. They have the form of an inverted cone, surrounded by an annular, wall-like elevation, whence their name. The Cap'itate papillae, 3 the second in size, and more numerous than the preceding, are conspicuous as small, red eminences, scattered over the surface of the tongue, but are especially numerous at and near the tip. They are rounded at the free extremity, and narrower at the basis of attachment. The Conical papil'lae/ smaller and much more numerous than the others, are crowded in the intervals between them, but are arranged in rows diverging from the median line of the tongue. All the papillae of taste, as described above, and the intervals between them, are covered with numerous minute, simple papil'lae 5 of a conical form. From those surmounting the conical papillae, the squamous epi- thelium rises in hair-like appendages, which give to these papillae a pencil- or brush-like arrangement, admirably adapted to the imbibition of liquids to be tasted. To these hair-like processes is due the velvety character of the surface of the tongue ; and it is upon them also that the so-called furred condition of the latter depends. The papillae of taste are processes of the mucous membrane of the tongue, richly supplied FIG. 202. w ith blood-vessels. The modes of termination of the nerves within these organs has not yet been ^&ss55z-&*&*&&e&*. satisfactorily determined, DIAGRAM OP THE PAPILLA OF THE TONGUE, moderately magnified. ^Ut the prevalent Opinion 1, capitate papillae ; 2, conical papillae ; 3, epithelium ; 4, the same jg that they end HI loops structure forming bunches of hair-like processes; 5, connective ., . , . tigsue in the simple papillae. The capillary blood-ves- sels distinctly appear within the latter in the form of loops communicat- ing with the vascular trunks at their base. 1 Papillae gustatoriae. 3 P. capitatae; p. fungiformes; p. cla- 2 P. circumvallatae; p. vallatae; p. max- vatse ; p. mediae; p. semilenticulares. imae; p. truncatae ; p. calyciformes ; p. 4 P conicae ; p minimae ; p pyrami- mucosae : p. lenticulares. dales : p. villosae ; p. conicae et filiformes. 5 P. filiformes ; filla ; villi linguae. THE ALIMENTARY APPARATUS. 283 Back of the position of the circumvallate papillae, corresponding with the floor of the fauces, the tongue is provided with numerous glands, named the lingual glands. 1 These are of two kinds : racemose glands, probably secreting mucus ; and follicular glands, which have the peculiar FIG. 203. PAPILLA OF THE TONGUE, highly magnified. 1, conical papillae; 2, capitate papilla; 3, simple papillae, occupying the intervals of the compound papillae ; 4, epithelium ascending from the conical papillae in hair-like processes; 5, isolated epithelial scales from the latter. constitution of the tonsils, the follicular glands of the palate and pha- rynx. A group of the lingual glands usually opens into a small pouch 2 just behind the middle circumvallate papilla. As previously indicated, a number of racemose glands also exist beneath the tongue ; and others likewise are found imbedded in the muscular structure of its sides. MUSCLES OF THE TONGUE. The muscles of the tongue form the great bulk of the organ. For the most part they are inserted into the fibrous layer of its investing mucous membrane, and, as they approach the latter, their fasciculi form an intricate intertexture, associated with many bundles of transverse, 3 longitudinal, 4 and vertical muscular fibres. 5 Mingled with these fibres there is a quantity of adipose tissue, which in some measure appears to take the ordinary position of connective tissue. 1 Glanduloe linguales. 2 Foramen coecum : f. Morgagni. 3 Musculus transversus linguae ; mus- culi transversales. 4 M. longitudinalis superior; m. chon- droglossus; m. superncialis linguae ; mus- culi longitudinales. 5 Musculi verticales. 284 THE ALIMENTARY APPARATUS. FIG. 204. The Hyo-glos'sal muscle 1 is a quadrilateral plane of fibres arising from the great horn and body of the hyoid bone, ^ j_ ,/ and ascending to expand ^ r jgjjpp .^ ^ e g .^ e ^ ^ e tongue, between the stylo-glossal and lingual muscles. The Geni'o-gios'sal muscle 2 is a thick, fan- shaped layer of fibres, arising tendinously from the posterior mental tu- bercle, and radiating back- ward and upward to be inserted into the tongue from its tip to its attach- ment to the hyoid bone. It is separated from the muscle of the opposite side by a thin partition of fibrous tissue. SIDE VIEW OF THE MUSCLES OF THE TONGUE. 1, 2, StylO-glOSSal muscle; 3, lingual muscle; 4, upper part of the tongue; 5,6, hyo- glossal muscle; 7, genio-glossal muscle; 8, stylo-pharyngeal muscle ; 9, genio-hyoid muscle ; 10, 11, median line of the mylo- hyoid muscles. The Lin/gual muscle 3 is a narrow fasciculus of fibres, situated between the insertion of the hyo-glossal and genio-glossal muscles, and extending from the hyoid bone to the tip of the tongue. The Sty'lo-glos'sal muscle 4 arises from the extremity of the styloid process of the temporal bone and from the stylo-maxillary ligament, and descends to expand in the side of the tongue externally to the hyo-glossal muscle. The genio-glossal muscles, when the mouth is open, will protrude the tongue, and the hyo-glossal and lingual muscles will retract it again. The anterior portion of the genio-glossal muscles when alone contract- ing will draw down the tip of the tongue. The stylo-glossal muscles draw the sides of the tongue upward and backward. The arteries of the tongue are derived from the lingual branches of 1 M. hyo-glossus ; m. basio glossus, ce- rato-glossus, et chondro-glossus; m. hy- oideo-glossus; m. hyo-chondro-glossus ; m. hypsilo-glossus. 2 M. genio-glossus; m. genio-hyo-glos- sus; m. meso-glossus ; m. nonus linguae. 3 M. lingualis ; m. basio-glossus ; m. glossianus ; m. longitudinalis inferior. 4 M. stylo-glossus. THE ALIMENTARY APPARATUS. 285 the external carotids. The principal veins are the ranine, which usually join the facial vein on each side of the head. The nerves are the lingual branch of the inferior maxillary, the lingual branches of the glosso-pharyn- geal, and the hypoglossal nerve. The former two supply the mucous membrane and papilla of taste ; the latter supplies the muscular struc- ture. THE TEETH. Teeth 1 have so close a relationship with the nature of the food and the habits of animals, that they present to the zoologist most important distinctive characters in classification. Three different substances gen- erally enter into their constitution : cement, a material resembling bone ; dentine, a harder material forming the ivory of the tooth ; and enamel, not only the hardest material of teeth, but the hardest of all organic substances. In the grinding teeth of herbivorous animals, as the horse, ox, and elephant, the three substances alternate with one another in such a manner that, as the teeth are worn, an uneven triturating surface is always preserved. In carnivorous and omnivorous animals, as the cat, dog, and hog, the body of the teeth is composed of dentine, while the crown or exposed part is capped with enamel, and the roots are covered with a thin film of cement. The teeth are properly appendages of the mucous membrane of the alimentary canal, and are developed from it. They are inserted into a portion of the skeleton so as to give them a firmly-fixed position. In birds and turtles we find their place on the jaws occupied by a corneous bill, which, like nails and hairs, is an appendage of the skin. In grami- nivorous birds, as the common fowl, pebbles swallowed with the food are a substitute for teeth. The gizzard, which is a powerfully muscular stomach with a thick epidermis-like lining, triturates the hard food through the aid of the pebbles. Man and almost all other mammals, in the course of life, are provided with two sets of teeth, of which the first are the temporary or milk teeth; the second, the permanent teeth. Reptiles and fishes are pro- vided with numerous sets, which succeed one another through life. The teeth are divided into four kinds, named inci'sors, canines', pre- mo'lars or bicus'pids, and molars. The protruding portion of the teeth is named the crown or body; 2 the portion inserted into the alveoli or sockets of the jaws, is the fang 1 Sing.: dens; odous ; pl.:dentes; odontes ; mordices. 2 Corona. 286 THE ALIMENTARY APPARATUS. or root; 1 and the slightly constricted portion clasped by the gums, is the neck, 2 The crown varies in form in the different kinds of teeth. The fang gradually tapers to its extremity, and is firmly attached to the sides of the alveolus, in which it is inserted, by fibrous tissue continuous with the periosteum of the jaws and the submucous tissue of the gums. At the neck of the tooth a slight accumulation of this tissue constitutes the dental ligament. The teeth have in their interior a small hollow called the pulp cavity, 3 which has the general form of the teeth, and contains a soft, highly sen- sitive, and vascular structure named the pulp. 4 This receives its blood- vessels and nerves through a narrow canal 5 opening at the extremity of the fangs. The teeth in each jaw form an unbroken arch, which is rarely the case in any of the inferior animals. The upper arch is larger than the lower one, and projects slightly beyond it. This difference is mainly due to the obliquity fqrward of the upper front teeth, while the corresponding ones below are vertical, and those behind slightly inclined inward. When the jaws are shut, the upper incisors inclose those below, while the suc- ceeding upper teeth alternate with those below ; the triturating surfaces of the molars being in contact. CHARACTERS OF THE PERMANENT TEETH. The Permanent teeth 6 are thirty-two in number, sixteen in each jaw, or eight on each side of each jaw, as follows : two incisors, one canine, two premolars, and three molars. Occasionally there is a diminution or an increase in the number. When there are supernumerary teeth, they are usually small, and provided with a single fang. The Inci'sors, 7 eight in number, are the four front teeth of each jaw, and are so named from their being adapted to cutting or biting the food. Their crown is wedge-shaped or chisel-like, being convex in front, beveled behind, and triangular at the sides. The cutting edge at first is narrow, and provided with three small tubercles, but these are soon obliterated from use, and the edge gradually widens. The fang is long, conical, and compressed at the sides. 1 Radix. 6 Second teeth; last teeth; dentes per- 2 Cervix ; collum. manentes ; d. serotini. 3 Cavitas pulpae; cavum dentis; an- 7 Incisive teeth: dentes incisivi, or trum dentale. incisores; d. primores; d. tomici, raso- 4 Pulpa ; blastema dentis. sores, gelasini, ctenes, or dichasteres. 5 Canalis radicis, or dentalis. THE ALIMENTARY APPARATUS. 287 The upper incisors are larger than the lower ones, and of the former the central incisors 1 are the larger, while the lateral ones are the larger in the case of the lower incisors. The upper incisors are directed down- ward and forward, while the lower ones occupy a vertical position. FIG. 205. UPPER AND LOWER PERMANENT TEETH, EXTERIOR VIEW. 1, first incisors ; 2, canines ; 3, first premo- lars ; 4, middle molars. LATERAL VIEW of the same teeth, as in the pre- ceding figure. The Canine' teeth, 2 four in number, are larger than the incisors, and succeed them in position, one on each side above and below. Their crown is blunt, conical, beveled behind, and becomes more blunt from attrition. Their fang is conical, compressed at the sides, and longer than in any of the other teeth. It is also marked laterally by a slight furrow, as if indicating a disposition to divide into two. The upper canines, commonly called eye teeth, are larger and longer than the lower ones, which are commonly known as the stomach teeth. In carnivorous animals the canine teeth are remarkable for their length and strength, and are admirably adapted to seizing, retaining, and tearing living prey. From their conspicuous character in the canine or dog tribe they have received their name. The Premo'lars, or bicus'pid teeth, 3 eight in number, succeed the ca- 1 Butter teeth. 2 Cuspid teeth ; dentes cuspidati ; ca- nini; angulares, or laniarii; d. columel- lares ; oculares, or mordentes ; cynodon- tes ; pug teeth. 3 Small molars; dentes bicuspidati; d. buccales. 288 THE ALIMENTARY APPARATUS. nines in position, two on each side above and below. Their crown is cubical with rounded borders, prominently convex externally and in- ternally, and less so or flattened at the sides. The triturating surface has a prominent border elevated before and behind into a pair of tuber- cles, of which the outer one is the larger and higher. The fang is coni- cal, much flattened, and deeply grooved at the sides, indicating a dispo- sition to divide. The upper premolars are larger than the lower ones, and their fang is usually more or less divided into two, especially that of the second upper premolar. The Mo'lars, 1 twelve in number, are next in succession to the premo- lars, three on each side above and below. They are commonly known as grinders or jaw teeth; and have a large, cuboidal crown, with low, rounded sides and borders, but are generally least convex laterally, or are even flattened in this position. In the upper molars the grinding surface is rhomboidal, with a prominent border, elevated at the four angles into as many tubercles. In the lower molars, the grinding surface is nearly oblong square, with a prominent border elevated into five tubercles. The lower molars have a pair of conical fangs placed side by side, and much compressed and deeply grooved laterally. The upper molars have three conical fangs, two external and one internal ; the latter being the larger and grooved, as if disposed to divide. The molars slightly decrease in size from first to last, and the lower ones are larger than the upper ones. The last of the series, from its comparatively late appearance in life, is named the wisdom tooth. 2 It is liable to considerable variation in size and form, more especially in the case of the upper one. Its fangs are usually more or less confluent into a single cone. CHARACTERS OF THE TEMPORARY TEETH. The Temporary or milk teeth 3 are twenty in number, ten in each jaw, or five on each side of each jaw, as follows : two incisors, one canine, and two molars. The incisors and canines correspond in number with those of the per- manent set, which they also resemble in form ; but they are smaller, and the crowns are broader in proportion to their length. 1 Denies molares ; large molars; true 2 Dens sapientiae ; d. serotinus; d. so- molars; denies multicuspidati; d. maxil- phroreticus; d. sophronista; wit tooth; lares, clavales, or gomphii ; molse ; my- last tooth. lodontes ; mylacri ; momisci ; cheek 3 Dentes lactei ; d. caduci ; d. tempo- teeth ; axle teeth ; wall teeth ; log teeth ; rarii ; deciduous teeth ; primary, or grinding teeth. shedding teeth. THE ALIMENTARY APPARATUS. 289 No premolars belong to the temporary set of teeth. The molars are eight in number, succeeding the canines in position, two on each side above and below. FIG. 207. 1 345 FIG. 208. TEMPORARY TEETH OF ONE SIDE. 1, 2, upper and lower incisors; 3, upper and lower canine; 4, 5, upper and lower molars; 6, 7, triturating surface of the lower molars; 8, 9, triturating surface of the upper molars. STRUCTURE OF THE TEETH. On splitting a tooth longitudinally, the exposed surface exhibits, besides the pulp cavity, three different sub- stances. The greater portion of the tooth appears to be composed of a yellowish-white substance, which is called dent'ine; the crown is capped with a harder and whiter layer, named the enam/el; and a thin, translucent investment to the fang is the cement'. The Dent'ine, or ivory, 1 forms the principal bulk of the tooth, giving to it the general shape, and containing the pulp cavity. It is yellowish-white, and has the appearance of dense bone, which it further resembles in chemical composition. It consists of about twenty-eight parts of bone cartilage and seventy-two parts of earthy matters ; mostly phosphate of lime, with a little carbonate of lime. In thin section, beneath the microscope, the VERTICAL SECTION OF A MOLAR TOOTH. moderately magnified. 1, enamel, the lines of which indicate the arrange- ment of its columns; 2, dentine, the lines indicating the course of its tu- bules; 3, thin lamina of the dentine forming the wall of the pulp cavity, the dots indicating the orifices of the dentinal tubules ; 4, cement. 1 Ebur ; substantia ossea, or eburnea ; tooth bone ; proper tooth substance ; osseous substance. 19 290 THE ALIMENTARY APPARATUS. dentine is found to be composed of a translucent, amorphous substance, pervaded with a multitude of fine canals, possessing distinct walls from the intervening material. The canals, named dent/inal tu/bules, 1 commence with open orifices at the surface of the pulp cavity, and radiate from thence to the periphery of the tooth. They have a general parallel and gently waving or undulating course. As they proceed outwardly, they divide into several principal branches, pursuing the same general parallel course FIG. 209. Fro. 210. Fig. 209. VERTICAL SECTION OF THE FANG OF A CANINE TOOTH, exhibiting the structure of the dentine and cement. 1, inner extremities of the dentinal tubules ; 2, outer extremities of the tubules, terminating in interspaces at the boundary of the dentine; 3, cement; 4 lacunoe like those of bone. Highly magnified. Fig. 210. SECTION OF DENTINE, cutting across the direction of its tubules, very much magnified. The tubules are seen to have thick walls, distinct from the intervening material. to one another. They also gradually become narrower, and give off in- numerable, fine, divergent branches, which anastomose with one another. The walls of the tubules are nearly as thick as their calibre, which, in the fresh tooth, is filled with a colorless liquid, replaced by air in dried specimens. In consequence of the latter condition, the dried microscopic sections of teeth, when viewed by transmitted light, appear pervaded by black lines ; while by reflected light, the same lines appear silvery white. FIG. 211. FIG. 212. THREE ENAMEL COLUMNS, highly magnified ; ex- hibiting the six-sided prismatic and waving charac- ter. SECTION OF ENAMEL, highly magnified, at right angles to the course of its columns; exhibiting the six-sided character of the latter. The Enam'el 2 is the glistening-white or bluish-white substance invest- ing the crowns of the teeth. It is thickest on the triturating surface, and gradually diminishes toward the neck, where it terminates by a 1 Canaliculi dentium. 2 Substantia vitrea ; s. adamantina ; s. filamentosa; cortex; c. striata; crusta adamantina ; nitor dentium. THE ALIMENTARY APPARATUS. 291 sharply defined edge. As previously mentioned, enamel is not only the hardest of all the dental structures, but it is the hardest of all organized substances. In chemical composition it consists of only five parts of bone cartilage, with ninety-five parts of earthy matters, mostly phosphate of lime. Viewed with the microscope, enamel is found to consist of solid, hexa- hedral columns, resting with one extremity on the dentine of the crown, and with the other extremity free. The columns are not straight, but undulating in their course ; and at the sides they present a faint, trans- versely striated appearance. The arrangement of the enamel columns is the most favorable that could have been adopted to prevent their detachment and rapid abrasion ; though this arrangement, together with the great deficiency of bone car- tilage, renders the enamel brittle, and, under extremes of temperature, *to which it is often subjected in the use of hot and cold food, it is liable to crack. The exterior surface of the unworn enamel, when treated with hydro- chloric acid, so as to remove its calcareous salts, separates in the form of a thin, homogeneous membrane, 1 which, though it is intimately blended with the exterior ends of the enamel columns, appears to be an inde- pendent structure. The Cement' 2 is a very thin layer of osseous substance investing the fangs of the teeth, commencing at the neck, and gradually becoming thicker to the extremities of the fangs. In the latter position, in the teeth of old persons, it frequently becomes much increased in thickness, and sometimes forms a nodular mass. Like true bone, the cement con- tains branching lacunae, but vascular canals pervade it only when it becomes much thickened. The teeth, like the epithelium of a mucous membrane, are entirely non- vascular, and their fluids are obtained by imbibition from the dental pulp and the periosteum of the fangs. The Dent/al pulp 3 is a soft, translucent, reddish-white substance, filling the pulp cavity of the teeth. It is composed of an exterior layer of nu- cleated cells, with an interior mass of indistinctly defined areolar tissue, mingled with many nuclei, and containing an abundant colorless liquid. Highly sentient and vascular, its nerves and blood-vessels, entering the fine aperture at the ends of the fangs, are derived from the dental nerves of the trifacial, and the dental arteries of the internal maxillary artery. 1 Nasmyth's membrane ; cuticle of the crusta petrosa ; cortical substance ; sub- enamel ; skin of the teeth. stantia ostoidea. 2 Cementum ; crusta ostoides radicis ; 3 Pulpa dentis. 292 THE ALIMENTARY APPARATUS. DEVELOPMENT OF THE TEETH. The temporary teeth commence their development from the sixth to the tenthXonth of embryonic life, originating in a corresponding num- ber of papillae from the bottom of the dental groove, 1 which is a semi- circular inflection of the mucous membrane at the margin of the gums. Processes 2 from the dental groove gradually inclose the papillae in sepa- rate compartments, which contract in the course of the fourth month, and include the papillae in distinct cavities, named the dental sacs. The FIG. 213. DIAGRAM OF THE MODE OF DEVELOPMENT OF THE TEETH, a, section across the dental groove ; fc. papilla developed in the latter; c, the groove deepened and processes forming which ultimately close it; rf, the groove becoming closed ; e, dental sac containing a dental pulp, which is the rudiment of the crown of a temporary incisor ; the cavity above is reserved for a permanent incisor ; /, the crown of the temporary incisor fully formed, and the reserved cavity for the permanent tooth moving backward ; g, fang of the temporary incisor produced, and origin of the dental papilla of the future permanent tooth; h, erup- tion of the temporary incisor, and the alveoli produced for both teeth ; t, the temporary incisor occupy- ing its functional position, and the crown of the permanent incisor developed. papillae, now called dental pulps, gradually assume the form and size of the crowns of the future teeth, and are defined by a delicate basement membrane. 3 The enlarging dental sacs, closely applied to the included pulps, also undergo a change in structure ; and they are supplied with blood-vessels from the dental arteries as well as from those of the gums. From the fifth to the eighth month of foetal life the dental pulps com- mence transformation into dentine by the deposit of calcareous salts. This transformation begins at the summit of the pulps and proceeds toward their base, and from without inwardly. 1 Primitive dental groove. Opercula. Membrana praeformativa. THE ALIMENTARY APPARATUS. 293 While this process is going on, the thick internal layer of the dental sacs, named the enamel organ, 1 undergoes transformation into enamel, from within outwardly. The crown of the tooth being produced, the dental pulp now grows in length, and as it gradually develops the shape of the future fang, it is transformed into dentine, from without inwardly, and from the base toward the end of the fang. The lengthening of the fang occasions the eruption or so-called cut- ting of the teeth, 2 in which process the latter burst their sacs and pro- trude from the gums. The eruption of the temporary teeth. 3 occurs after birth, during the period between six months and two and a half years ; usually in the following order, the lower teeth generally taking precedence of the upper ones : The central incisors from the sixth to the eighth month ; The lateral incisors from the seventh to the ninth month ; The first molars from the twelfth to the fourteenth month ; The canines from the sixteenth to the twentieth month ; The last molars from the twentieth to the thirtieth month. During the fourth and fifth months of foetal life, in the progress of development of the dental sacs of the temporary teeth, a corresponding number of cavities 4 are developed in the dental groove 5 over them. These reserved cavities subsequently become the dental sacs of perma- nent teeth ; those of the upper jaw receding behind and above the po- sition of the temporary teeth ; those of the lower jaw receding behind and below the temporary teeth. The dental sacs just indicated are finally inclosed in osseous cavities of the jaws, communicating by canals 6 with the margin of the latter. The canals contain a narrow pedicle, 7 which is the closed and elongated neck of the dental sacs continuous with the gum behind the corresponding temporary teeth. The three permanent molar teeth on each side, above and below, origi- nate in succession from the posterior extremity of the dental groove. The permanent teeth are developed from their dental sacs and pulps in the same manner exactly as the temporary teeth. Calcification com- mences in the different ones from a period prior to birth up to the twelfth year subsequently. At six years, when the temporary teeth are usually still preserved, the 1 Organon adamantinse. * Cavities of reserve. 2 Teething ; dentition ; odontophyia. 5 Secondary dental groove 3 First dentition ; odontia dentionis lactantium. 6 Itinera dentium. 7 Gubernaculum dentis. 294 THE ALIMENTARY APPARATUS. jaws contain besides, the crowns of all the permanent teeth except the last molars or wisdom teeth. The subsequent development of the fangs of the permanent teeth causes a gradual advancement of their crowns toward the gums. Those which come into contact with and press against the temporary teeth excite a gradual absorption of the fangs of the latter Continuing to advance, the permanent teeth detach the loosened crowns of the temporary set, and protrude from the gums in their place. The eruption of the permanent teeth 1 and the shedding of the tempo- rary set commences between the fifth and seventh years after birth. The first permanent molars usually protrude before any of the temporary teeth are shed, and it is perhaps partly due to this circumstance that these teeth are usually the first to undergo decay. The course of eruption of the permanent teeth is commonly as follows, the lower ones preceding the upper : The first molars from the fifth to the seventh year ; The central incisors from the sixth to the eighth year ; The lateral incisors from the seventh to the ninth year ; The first premolars from the eighth to the tenth year ; The second premolars from the tenth to the twelfth year ; The canines from the eleventh to the twelfth year ; The second molars from the twelfth to the fourteenth year ; The last molars or wisdom teeth from the seventeenth to the twenty- second year. THE PHAEYNX. The Pha'rynx 2 or throat is the funnel-like cavity occupying the gut- tural region of the skull, and extending from its base down to a level with the fifth cervical vertebra, where it terminates in the oesophagus. Behind it is the vertebral column, and on each side the great blood-ves- sels and nerves of the neck. Communicating with it in front, in succes- sion from above downward, are the nasal fossae, the mouth, and the larynx ; and opening into it on each side of the nasal fossa3 is the Eu- stachian tube. Its upper extremity is attached to the basilar process of the occipital bone ; and on each side it is attached in succession to the petrous portion of the temporal bone, the internal pterygoid process, the pterygo-maxillary ligament, the back part of the molar ridge of the lower jaw, the root of the tongue, the hyoid bone, and the larynx. With the surrounding parts it is connected by areolar tissue. 1 Second dentition; odontia dentionis puerilis; dedentition. 2 Pharus; pharyngethros; fauces; gula; isthmos; laemos; ingluvies ; gurges; os posterum ; principium guise ; communis aeris et nutrimentorum via. THE ALIMENTARY APPARATUS. 295 The walls of the pharynx are musculo-membranous. Exteriorly it is provided with a thin, fibrous investment, which at its attachment to the base of the skull assumes a stronger and more aponeurotic character. Within this structure succeeds a moderately thick, muscular layer, sepa- rable into five pairs of distinct muscles, presently to be described. The lining mucous membrane of the pharynx is soft and red, and is con- nected with the muscular layer by a strong submucous tissue containing many glands. As low down as the floor of the nose the mucous mem- brane is furnished with a columnar ciliated epithelium, but in the lower portion of the pharynx it resembles that of the mouth, being furnished with minute papillae imbedded in a squamous epithelium. The pharyn'geal glands are of the racemose and follicular kind ; the latter variety being simple and compound, having the peculiar constitu- tion of the tonsils and follicular glands of the palate and tongue. The blood-vessels of the pharynx are derived from the pharyngeal, inferior palatine, and thyroid arteries. The nerves are supplied from the glosso-pharyngeal, pneumo-gastric, and sympathetic system. MUSCLES OF THE PHARYNX. The Pal'ato-pharyn'g'eal muscle 1 originates in the soft palate, and descends within the posterior half arch of the palate to be inserted, in conjunction with the succeeding muscle, into the side of the pharynx and the upper part of the thyroid cartilage. The Sty'lo-pharyn'geal muscle 2 arises from near the root of the sty- loid process of the temporal bone, and descends between the superior and middle constrictors of the pharynx, to expand upon the mucous membrane of the latter, and partially to be inserted into the upper part of the thyroid cartilage. The Superior Constric'tor of the Pharynx 3 is a thin, quadrilateral muscle arising from the pterygo-maxillary ligament and the lower half of the internal pterygoid process. Proceeding backward, it conjoins the muscle of the opposite side, and is prolonged to be attached to the ba- silar process of the occipital bone. 1 M.palato-pharyngeus; m. pharyngo- 3 M. constrictor pharyngeus superior; staphylinus; m. staphylino-pharyngeus; m. cephalo-pharyngeus; m. glosso pha- m. thyro pharyngo-staphylinus; m. hy- ryngeus ; m. mylo-pharyngeus ; m. pte- pero pharyngeus in part. rygo-pharyngeus ; m. pterygo-syndcsmo- 2 M. stylo-pharyngeus; m. stylo-thy- staphili-pharyngeus. ro-pharyngeus. 296 THE ALIMENTARY APPARATUS. The Middle Constric'tor of the Pharynx 1 is a fan-shaped muscle, arising from the great and small horns of the hyoid bone, from whence it radiates to conjoin the muscle of the opposite side in the posterior median line of the pharynx. The lower fibres of the muscle are concealed by the inferior constrictor ; the middle ones are nearly horizontal ; and the upper ones overlap the superior constrictor. FIG. 214. FIG. 215 Fig. 214. POSTERIOR VIEW OF THE MUSCLES OF THE PHARYNX. 1, vertical section, transversely, of the base of the skull, just in advance of the cervical vertebras; 2, 3, posterior border and angle of the lower jaw ; 4, internal pterygoid muscle; 5, styloid process giving attachment to 6, the stylo-pharyngeal mus- cle ; 7, larynx ; 8, inferior constrictor of the pharynx ; 9, middle constrictor ; 10, superior constrictor. Fig. 215. SIDE VIEW OF THE MUSCLES OF THE PHARYNX. 1, trachea; 2, cricoid cartilage; 3, vocal membrane; 6, hyoid bone; 7, stylo-hyoid ligament; 8, oesophagus; 9, inferior constrictor of the pharynx; 10, middle constrictor; 11, superior constrictor; 12, portion of the stylo-pharyngeal muscle observed pass- ing into the interval between the superior and middle constrictors; 13, upper extremity of the pharynx; 14, pterygo-maxillary ligament; 15, buccinator muscle; 16, oral orbicular muscle; 17, mylo-hyoid muscle. The Inferior Constrictor of the Pharynx 2 arises from the upper one or two rings of the trachea, the side of the cricoid cartilage, and an oblique line of the thyroid cartilage. From this origin it curves back- ward, expanding in its course, and conjoins the muscle of the opposite side in the posterior median line of the pharynx. The inferior fibres of the muscle are horizontal, and inclose the com- mencement of the oesophagus ; and the upper fibres ascend, gradually 1 M. constrictor pharyngeus medius ; 2 M. constrictor pharyngeus inferior ; m. hyo-pharyngeus ; m. cerato-pharyn- m. lai-yngo pharyngeus ; m. thyro- et geus ; m. chondro-pharyngeus ; m. syn- crico-pharyngeus ; m. crico-thyro-pha- desmo-pharyngeus ; m. hyo-glosso-basi- ryngeus. pharyngeus. THE ALIMENTARY APPARATUS. 297 increasing in obliquity, and overlap the lower part of the middle con- strictor. The muscles of the soft palate, fauces, and pharynx, together with those of the tongue and the elevators of the hyoid bone and larynx, are concerned in the action of deglutition, or swallowing. The genio-glossal muscles, drawing the tongue forward and upward, press the food against the hard palate, and from thence into the fauces. The stylo-glossal muscles now contract, narrowing the entrance of the fauces ; and the stylo-glossal muscles draw the tongue backward and up- ward. The soft palate is drawn upward and backward, and made tense by the action of its elevators and tensors. At the same time, the palato- pharyngeal muscles cause the posterior half arches of the palate to ap- proach each other, leaving only a small interval, which is closed by the uvula, and thus the communication of the pharynx with the nasal cavi- ties is cut off. The pharynx and larynx are drawn up by the stylo- pharyngeal, stylo-hyoid, digastric, genio-hyoid, and mylo-hyoid muscles, through which action the former cavity is widened, and the latter is closed by pressure against the epiglottis. The food received into the pharynx is passed downward into the oesophagus by the action of its constrictors, 1 after which the parts resume their ordinary position. THE (ESOPHAGUS. The Oesoph'agus or gullet 2 is a musculo-membranous tube descending from the pharynx in a slightly flexuose course through the neck and pos- terior mediastinal cavity to the stomach. It commences on a level with the fifth cervical vertebra and the cricoid cartilage of the larynx, pro- ceeds downward in contact with the vertebral column, and opposite the ninth dorsal vertebra passes through the cesophageal orifice of the diaphragm. In the neck, the trachea is in front, and the primitive ca- rotid artery on each side of it ; in the thorax, the pericardium is in front, the descending aorta to its left, and the azygos vein to its right. ^ The oesophagus is about nine inches long, and rather less than an inch in diameter. It is narrowest at its commencement, gradually widens in its descent, but is slightly constricted as it passes through the diaphragm, after which it quickly expands into the stomach. In the state of rest it is flattened from before backward ; but when distended, is cylindroid in shape. 1 Musculus sphincter gulae. 2 Gula; fistula cibalis; f. ventriculi; infundibulum ventriculi ; via stomachi et ventris; gluttus. 298 THE ALIMENTARY APPARATUS. The oesophagus is provided externally with a thin, fibrous investment, inclosing the oesophageal plexus of nerves, and adhering to the contigu- ous parts. Succeeding this investment is the muscular coat, 1 which is about three-fourths of a line thick, and composed of two layers. The external layer consists of longitudinal fibres, which originate in three fasciculi from the cricoid cartilage and inferior constrictors of the pharynx, and surround the oesophagus uniformly to the stomach. The internal layer, thinner than the other, consists of transverse or circular fibres, continuous with the inferior constrictors of the pharynx, and ex- tending to the stomach. In the upper part of the oesophagus the muscular coat is exclusively composed of striated fibres, but in its descent unstriated fibres become mingled with the latter, and finally predominate. The mucous membrane lining the oesophagus is much paler than in the pharynx or mouth, though it has the same structure, being provided with minute papilla and a squamous epithelium which completely conceals the latter When the oesophagus is at rest, the mucous membrane is thrown into slight longitudinal folds, which disappear in the distended condition of the organ. Beneath the mucous membrane is a moderately thick layer of sub -mucous tissue, connecting it to the muscular coat, and con- taining some small, scattered, racemose glands, named from their position the cesophage'al glands. 2 The blood-vessels of the oesophagus are derived from the inferior thy- roid and cesophageal arteries. The nerves are supplied by the pneumo- gastrics and the sympathetics. THE CAVITY OF THE ABDOMEN. The Cavity of the Abdomen, or of the belly, 3 the most extensive space of the body, is occupied by the greater portion of the alimentary and uro-genital apparatus. It is lined with an extensive serous membrane, the peritoneum, which, from its relationship with the many viscera it inves^j. is very complex in its arrangement. The viscera of the abdominal cavity leave no unoccupied vacuity or space filled with air; they follow the movements of the muscular walls of the abdomen ; and the enlargement or decrease of any one results in the displacement of those around. In consequence of the great extent of the abdomen, and the frequent necessity of referring to the relative position of the organs which occupy the different parts of its cavity, it is artificially divided into regions, 1 Tunica vaginalis guise. 2 Glandulse oesophageales. 3 Cavura abdominis. THE ALIMENTARY APPARATUS. 299 FIG. 216. indicated by lines drawn on the abdominal walls. Transverse lines en- circling the body, one at the lower margin of the thorax, the other at the hips or crest of the ilium on each side, divide the abdomen into three zones. A vertical plane, ascending on each side from the anterior in- ferior spinous process of the ilium, will divide each zone into three parts, and in this manner nine re- gions will be defined. Of the middle regions, ..the upper one is the epi- gas'tric region; 1 the suc- ceeding one, the umbilic- al region ; 2 and the lowest, the hypogas'tric region, 3 Of the lateral regions, the upper pair are the right and left hypochondriac regions ; 4 those succeed- ing, the lum'bar regions ; 5 and the lowest, the il'iac regions. 6 The different organs oc- cupying these regions are as follows : The stomach occupies the left hypochondriac, epigastric, and a small part of the right hypo- chondriac regions. In a CAVITY OP THE ABDOMEN LAID OPEN, WITH THE VISCERA RETAINED IN THEIR RELATIVE POSITION. The straight lines indicate the regions of the abdomen, a, epigastric region ; b, hypochondriac regions ; c, umbilical region ; d, lumbar regions ; e, hypogastric region ; /, iliac regions. 1, flaps of the abdominal wall turned aside; 2,3, left and right lobes of the liver; 4, fundus of the gall-bladder; 5, round ligament of the liver; 6, part of the suspensory ligament of the liver; 1, 8, stomach; 9, commencement of the duodenum; 10, spleen; 11, great omentum ; 12, small intestine; 13, caecum; 14, vermiform appendix; 15, ascending colon; 16, transverse colon; 17, descending colon ; 18, sigmoid flexure ; 19, epiploic appendages; 20, ridges indicating the course of the remains of the urachus and umbilical arteries ; 21, diaphragm. distended condition, with the small intestine empty, it encroaches on the umbilical region. The small intestine forms a convoluted mass, occupying the umbilical region and the contiguous borders of the surrounding regions. When 1 Regio epigastrica ; r. cardiaca ; r. stomachica ; epigastrium. 2 R. umbilicalis ; r. mesogastrica ; r. gastrica ; mesogastrium. 8 R. hypogastrica ; r. pubis ; hypogas- trium ; rumen ; venter parvus, or imus. 4 Regiones hypochondriacae ; r. sub- cartilaginese ; hypochondria. 5 R. lumbares, or lumbales ; lumbi ; lendis ; psoae ; loins ; flanks ; reins ; la- para. 6 R. iliacse ; inania ; flanks. 300 THE ALIMENTARY APPARATUS. the viscera of the pelvis are empty, a portion of the small intestine descends into that cavity. The large intestine, commencing in the right iliac region, ascends through the corresponding lumbar into the right hypochondriac region. Thence crossing through the boundary of the epigastric and umbilical regions to the left hypochondriac region, it descends through the suc- ceeding lumbar and iliac regions, and enters the pelvis at its back part. The liver occupies the right hypochondriac region, and extends across the epigastric into the left hypochondriac region. The spleen is situated deeply in the left hypochondriac region. The pancreas extends from one hypochondriac region to the other, through the deep part of the epigastric region. The kidneys occupy the deep parts of the lumbar regions or loins. , The urinary bladder occupies the pelvic cavity, but when distended rises into the hypogastric region. THE PERITONEUM. The Peritone'um, 1 the most extensive of all serous membranes, lines the walls of the abdomen, and from them is reflected upon the viscera. Like all serous membranes, it forms a completely closed sac, except that in the female the Fallopian tubes communicate with its cavity. The viscera are not included within the latter, but are, as it were, thrust for- ward from the back part of the abdomen, and inclosed by inflections of the peritoneum projecting into its own cavity. It is to these numerous inflections inclosing the viscera that the peritoneum owes the complexity of its arrangement. That portion of the membrane investing the viscera is named the vis'ceral peritone'um, 2 and that lining the abdominal walls is the parie'tal peritoneum ; 3 and both portions on the interior of the peritoneal cavity are in close contact with each other. Their opposed surfaces are smooth and shining, and are bathed with a serous liquid, which give the organs they invest a slippery feeling, and adapts them favorably to move on one another. The attached surface of the perito- adheres closely to the contiguous parts by thin, connective tissue.* merous doublings or folds, 5 associated by connective tissue, often 1 Peritonaeum ; membrana abdominis ; subperitoneal membrane; retro perito- velamentum abdominale ; tunica praeten- neal membrane. sa ; operimentum praetensum ; pagos ; 5 Omenta ; epiploones, ligaments, and syphar; zepach. mesenteries. Sing.: omentum ; epiploon; 2 P. viscerale, or intestinale. rete ; reticulum ; dertron ; gangamum ; 3 P. parietale. zirbus; operimentum intestinorum ; sac- 4 Textus cellulosus subperitonealis, or cus epiploicus ; sagena ; caul, subserosus ; lamina externa peritonei ; THE ALIMENTARY APPARATUS. 301 containing much fat, inclose and sustain the position of the viscera, and likewise include the blood-vessels, lymphatics, and nerves passing to and from the latter. In tracing the reflections of the peritoneum from the abdominal walls, and from one organ to another, in any direction, its complete continuity will be discovered. Thus the peritoneum, in ascending from the front and sides of the abdominal parietes, invests the diaphragm, and is thence reflected to the liver, producing three folds, named the suspensory and lateral ligaments of the liver. After inclosing the liver, it is reflected as a doubling, the gas'tro-hepat'ic omen'tum, from the transverse fis- sure of the liver to the small curv- ature of the stomach. Envelop- ing the latter, the peritoneum then passes from its great curvature, and makes a quadruple fold, named the great omen'tum. This is suspend- ed as a broad, apron-like process in front of the intestines, and has its posterior division above, inclos- ing the transverse colon. Passing thence to the back of the abdomen, the doubling named the transverse mesoco'lon is produced. Of the two layers of this doubling, the upper one proceeds to the back of the liver, there forming the posterior part of its lateral ligaments. The other layer of the transverse meso- colon descends, and, passing off lat- erally, incloses the colon on each side and forms the ascending and descending mesoco'lon. The peri- toneum, from the intervening por- tions of the mesocolon reflected forward from the vertebral column to the small intestine, forms the extensive fold named the mes'en- tery. From the root of the latter the peritoneum descends to the rectum, and, binding this to the posterior part of the pelvis, forms the mesorec'tum. The peritoneum is then re- flected from the rectum to the bladder, or in the female to the uterus, and DIAGRAM OF THE REFLECTIONS OF THE PERITONEUM IN A VERTICAL SECTION OF THE ABDOMEN, the peritO- neum represented by the thick, black line. 1, up- per segment of the sacrum ; 2, first lumbar verte- bra ; 3, dorsal vertebrae ; 4, diaphragm ; 5, liver ; 6, stomach; 7, transverse colon; 8, small intestine; 9, duodenum; 10, pancreas; 11, rectum; 12, vagina and uterus; 13, urinary bladder; 14, pubis; 15, greater cavity of the peritoneum ; 16, le 17, section of a lateral ligament of the gastro-hepatic omentum : the arrow communication, at the right border of the latter, of the great and lesser cavities of the peritoneum ; 19, great omentum ; 20, transverse mesocolon ; 21, me- sentery; 22, recto-uterine pouch; 23, vesico-uterine pouch; 24, portion of peritoneum lining the ante- rior wall of the abdomen. 302 THE ALIMENTARY APPARATUS. thence to the bladder, and from this it ascends to the anterior wall of the abdomen. In figure 217, representing the course of the reflections of the peri- toneum, it would appear as if the latter formed a small cavity 1 behind the stomach, distinct from the greater peritoneal cavity. This is, how- ever, not the case, as the two communicate by an aperture, named the foramen of Winslow, 2 behind the right border of the gastro-hepatic omentum. A finger passed through this opening, and downward between the stomach and colon, gains access to the space between the two divisions of the great omentum, or if in the new-born child a blow-pipe be intro- duced at the aperture, the great omentum may be inflated, and then appears as a large and delicate sacculated vesicle. The experiment sub- sequently fails, as the omentum, in the progress of life, becomes per- forated. The folds of the peritoneum, from their importance, may now be sep- arately considered. The Suspensory ligament of the liver 3 is a falciform doubling of the peritoneum, extending from the median line of the diaphragm to the upper surface of the liver, between its anterior notch and its posterior border, where it becomes continuous with the lateral ligaments. Its anterior extremity is extended from the liver to the umbilicus, and in- closes the obliterated umbilical vein. The Right and Left lateral ligaments 4 of the liver are the peritoneal attachments of the posterior border of the liver to the diaphragm. The former is very short, and though of two layers, these are remote from each other, except at the right border of the liver. The other is longer, and suspends the left lobe of the liver loosely. The Suspen'sory ligament of the spleen 5 is a doubling of peritoneum passing from the diaphragm to the upper part of the spleen ; and it is continuous with the left lateral ligament of the liver. The Gas'tro-hepat'ic omen'tum 6 is a thin doubling of the peritoneum, d between the transverse fissure of the liver and the small cnrva- the stomach. Its loft border is short, and incloses the cardiac orifice. Its right border is long, bounds the foramen of Winslow, and incloses the common biliary duct, the portal vein, and the hepatic artery. 1 Bursa omentalis; saccus retro-ven- 5 L. phrenico-lienale; phrenico-splenic tricularis ; sac of the omentum. ligament. 2 F. Winslovii ; hiatus of Winslow. 6 Lesser omentum ; omentum minus, 3 Ligamentum suspensorium hepatis ; or gastro-hepaticum ; gastro-hepatic epi- broad ligament ; 1. triangulare. ploon ; membrana macilentior ; small 4 L. lateralia hepatis. epiploon. THE ALIMENTARY APPARATUS. 303 The Gas'tro-splen'ic omen'tum 1 is a doubling of peritoneum passing from the cul-de-sac of the stomach to the hilus of the spleen, and con- tains the splenic blood-vessels. The Great omen/turn, or gas'tro-col'ic omen/turn, 2 is a quadruple doubling of peritoneum suspended from the great curvature of the stomach and transverse colon downward in front of the small intestine, nearly to the pelvis. It is a broad, thin, apron-like process, with its four layers inseparably united in the adult. It frequeii^ presents a perforated, lace-like appearance, crossed with reticular lines of fat, inc(P eating the course of long, narrow vessels, which are branches of the gastro-epiploic arteries and veins. In fat persons it contains a large accumulation of fat. Not unfrequently it is found tucked up above the small intestine. The Mes'entery 3 is a large doubling of the peritoneum, which is re- flected from the front of the vertebral column over the small intestine. Its root is about six inches wide, and extends obliquely from the left side of the second lumbar vertebra to the right iliac region. From the ver- tebral column the mesentery extends about four inches to its intestinal border, which corresponds in length with that of the small intestine it involves. Between the layers of the mesentery there are contained, besides areolar tissue and fat, the superior mesenteric blood-vessels and their accompanying plexus of nerves, the lacteals, and numerous lym- phatic glands. I The Mesoco'lon 4 is the portion of peritoneum which binds the colon to the back part of the abdomen. The transverse mesoco'lon 5 is a wide doubling, the layers of which, in front, after inclosing the transverse colon, become continuous with the posterior layer of the great omentum; while behind they diverge over the position of the pancreas and duode- num. The ascending 6 and descending mesoco'lon 7 is for the most part so short, that its two layers do not come into contact behind the corre- sponding portions of the intestine, which, in consequence, are closely bound to the posterior wall of the abdomen. In the left iliac region, 1 Omentum gastro-lienale ; o. gastro- num ; membrana pinguis intestinorum ; splenicum; gastro-splenic epiploon; g. s. medius intestinum ; lactes ; epichordis. ligament. 4 Mesenterium crassum. 2 Omentum majus; o. gastro-colicum ; 5 Mesocolon transversum. great, or gastro-colic epiploon ; rete 6 Right lumbar mesocolon ; right liga- ijus; peritonaeum duplicatum; zirbus ment of the colon; colic omentum, or lipinus. epiploon ; third omentum, or epiploon. 3 Mesenterium ; mesarseum ; media- 7 Left lumbar mesocolon and iliac mes- ocolon ; left ligament of the colon. 304 THE ALIMENTARY APPARATUS. however, it becomes so broad as to suspend the colon in a sigmoid flexure. The Meso-rec'tum is an extension of the descending mesocolon, con- necting the upper part of the rectum closely to the sacrum. The Rec'to-ves'ical folds, 1 as expressed by the name, are two duplica- tures of peritoneum which extend between the sides of the rectum and bladder. They include between them a pouch of peritoneum, named the rec'to-ve^frcal pouch, which extends downward between the rectum Jld bldJddfcr, "nearly to the position of the prostate gland. When the bladder and rectum are empty, the recto-vesical folds form together a crescentic line, and a portion of the small intestine occupies the recto- vesical pouch. In the female, the pouch just mentioned is divided, by the presence of the uterus and vagina, into two portions, which are named, from their position, the rec'to-u'terine and ves'ico-u/terine pouches, The former is the deeper, extending downward between the rectum and the upper part of the vagina while the other extends between the body of the uterus and the bladder. Instead of the recto-vesical folds, their place in the female is substituted by the rec'to-u'terine 2 and ves'ico-u'terine folds. 3 The Broad ligaments of the uterus are two folds of peritoneum pass- ing from the sides of the uterus to those of the pelvis. They inclose the ovaries and the Fallopian tubes. From the summit and sides of the bladder a slight fold 4 of peritoneum ascends to the umbilicus, and incloses the obliterated urachus and um- bilical arteries of the foetus. Likewise a pair of slight folds 5 ascend to the umbilicus, over the position of the epigastric blood-vessels. The latter folds cross the course of the inguinal region, and divide it into two shallow fossae, called, from their relative position, the internal and external in'guinal fossae. 6 The former corresponds in position with the external abdominal ring, the latter with the internal abdominal ring ; and here the peritoneum often presents a short, conical pouch, which was^bnce continuous with the vaginal tunic of the testicle. In the female, the pouch just mentioned is sometimes lengthened into a blind sac 7 accompanying the round ligament of the uterus a short distance into the inguinal canal. 1 Posterior false ligaments of the mentum suspensorium vesicte ; superior bladder j plicae semilunares. false ligament of the bladder. * Posterior ligaments of the uterus; 5 Plicae vesico-umbilicales laterales; plicae semilunares. plicae epigastricae. 3 Anterior ligaments of the uterus. 6 Fovea inguinalis interna et externa. 4 Plica vesico-umbilicalis media; liga- 7 Canal of Nuck. THE ALIMENTARY APPARATUS. 305 FIG. 218. THE STOMACH. The Stom'ach 1 is a large musculo-membranous pouch, situated within the abdomen, and extending from the oesophagus to the small intestine. It is the most capacious portion of the alimentary canal, and is a re- ceptacle in which the food is sub- mitted to the chemical action of liquids elaborated in its walls. It occupies the left hypochondriac re- gion extending through the epigas- tric into a small part of the right hypochondriac region. Above it is the diaphragm and liver; below, the transverse colon ; in front, the abdominal wall ; behind, the pan- creas ; to the right the liver, and to the left the spleen. In shape it is conical, curved upwardly on itself, and is extended obliquely from left to right. The different parts of the stom- ach, to which we usually refer in speaking of the organ, are its greater and lesser extremities, its greater and lesser curvatures, its anterior and posterior surfaces, and its cardiac and pyloric orifices. The greater extremity of the stomach is to the |et, and commu- nicates with the oesophagus by the car'diac orifice; 2 the lesser ex- tremity, also named pylor'ic extremity, 3 is to the left, and communi- cates with the small intestine by the pylor'ic orifice.* The greater extremity of the stomach projects several inches to the left of the oesophagus, and in this position is named the fundus. 5 The terminal portion of the lesser extremity, for about two inches of its THE STOMACH AND INTESTINES. 1, stomach ; 2, duodenum; 3, small intestine; 4, termination of the ileum ; 5, crccum ; 6. vermiform appendix ; 7, ascending colon; 8, transverse colon; 9, descend* ing colon; 10, sigmoid flexure of the colon; 11. rectum ; 12, spleen. 1 Stomachus; ventriculus; gaster; anocoelia; nedys; gluttupatens ; maw. 2 Cardia; oesophageal orifice; upper, or left orifice; os ventriculi; ostium oesophageum. 3 Pars pylorica. 4 Pylorus ; intestinal orifice , lowegr, or right orifice; ostium duodenale. 5 Cul-de-sac; great tuberosity. 20 306 THE ALIMENTARY APPARATUS. length, is slightly constricted from the rest, and is named the pyloric antrum. 1 The lesser curvature 2 of the stomach is directed upward and back- ward, and has attached the smaller omentum ; the greater curvature 3 is directed forward and downward, and has attached the anterior division of the great omentum. The anterior surface of the stomach presents forward and upward ; the posterior surface looks downward and backward, and is in contact with the diaphragm, pancreas, duodenum, and left kidney. The capacity of the stomach varies with the degree of distention, but ordinarily it will contain from one to two quarts, and measures from nine to twelve inches long, and from four to five inches in diameter where most capacious. The walls of the stomach are composed of four coats, named from their character serous, muscular, fibrous, and mucous, all of which adhere intimately together by means of connective tissue. The serous coat 4 is the most external, and is derived from the perito- neum. It is a thin, transparent membrane closely investing the stomach, except along the curvatures, where it leaves a narrow interval occupied by the trunks of the blood-vessels, lymphatics, and nerves of the organ. The muscular coat 5 is composed of three layers of pale-red, unstriated muscular fibres, pursuing different directions. The external layer con- sists of longitudinal fibres continuous with those of the oesophagus, from which they radiate on the stomach. They are most numerous along the curvatures, especially the lesser one, and are thinly scattered on the an- terior and posterior surfaces. The middle layer, more uniform and important than the former, consists of circular fibres. Commencing thinly at the fundus, they gradually accumulate toward the pyloric ex- tremity, and at the pyloric orifice form a thick fasciculus named the pylor'ic sphinc'ter. 6 The internal layer consists of oblique fibres, con- tinuous with the circular fibres of the oesophagus. They form a wide band embracing the cardiac orifice on the left, and spreading obliquely downward and to the right on the anterior and posterior surfaces of the stomach. The fibrous coat 7 is a thick, submucous tissue, forming an extensible layer upon which the strength of the stomach mainly depends. 1 Antrum pylori, or pyloricum; lesser * Tunica serosa. cul-de-sac; lesser tuberosity. 5 Tunica musculosa; stratum muscu- 2 Curvatura superior; superior, or dia- lare. phragmatic margin. 6 Sphincter pylori. 3 Curvatura inferior; inferior, or colic 7 Tunica fibrosa; t. nervosa, or nervea. margin. THE ALIMENTARY APPARATUS. 307 The mucous coat 1 or lining membrane of the stomach is soft and pulpy to the touch, and is of a pale-pinkish ash color. Under excitement it becomes more reddened, as during digestion ; and in inflammation it assumes a deep-red hue. It is thin at the fundus, and gradually thickens FIG. 219. FIG. 220. WRINKLED OR RUGOUS SURFACE OF THE MUCOUS MEMBRANE OF THE STOMACH. 1, wrinkles, or superficial folds ; 2, mammillated surface. toward the pyloric extremity, where it is from three-fourths of a line to one line in thickness. In the latter position, ordinarily, it presents nu- merous contorted reticular ridges or wrinkles, 2 the larger of which are longitudinal, and gradu- ally fade away toward the fundus of the stomach. These ridges multiply and increase in size with the s'lJ^^^^Wpi" SW. ft , / >'*.V 4 : *^*'^f^3HP5P^?f^5lB^1 r --*'v 1 'c3-f-!> < ;, ^ ' 5^"* <'**-*,V^* .>' extent ot contraction of the organ, and decrease or even disappear with its distention. At the pyloric orifice a thick, circular fold, or sometimes a pair of cres- centic folds, acts the part of a valve, and hence is named the pylor'ic valve. 3 It contains the thick mus- cular fasciculus constituting the pyloric sphincter. 1 Tunica mucosa; erusta villosa ventriculi ; gastro-mycoderis. 2 Rugae ; plicae. s Valvula pylori. MAMMILLA OF THE MUCOUS MEMBRANE OF THE STOMACH, moder- ately magnified, exhibiting the orifices of the gastric glands. 308 THE ALIMENTARY APPARATUS. The free surface of the gastric mucous membrane exhibits a feebly mammillated appearance, well represented in figure 219; and it is everywhere minutely punctured by the orifices of glands. It is pro- vided with a columnar epithelium, which commences at the cardiac orifice and subsequently continues throughout the remainder of the ali- mentary canal. The gastric glands 1 are tubular, and closely set upright in the thick- ness of the mucous membrane. They are generally simple, nearly straight or slightly tortuous, and gradually increase in length from the cardiac toward the pyloric orifice, to which circumstance is due the dif- ference in thickness of the mucous membrane in the same direction. Some of the glands, both in the vicinity of the cardiac and pyloric orifices, FIG. 222. SMALL PORTION OF THE MUCOUS MEMBRANE OF THE STOMACH, WITH THE IMBEDDED GASTRIC GLANDS. 1, the glands ; 2, orifices of the glands ; 3, epithelium of the mucous membrane; moderately magnified. are compound, consisting of a main tube dividing at bottom in from two to four branches. Many of the gastric tubular glands are lined throughout with a columnar epithelium, not differ- ing from that of the mucous mem- brane of the stomach. Most of them, 2 however, are provided in their deeper part with comparatively large, rounded or polyhedral cells, 3 which gradually merge toward the orifices of the glands info columnar epithelial cells. Besides the tubular glands, the^ stomach contains at its pyloric end a few minute racemose glands ; and not unfrequently in the same position there may be detected a few small, rounded, whitish bodies, resembling the solitary glands of the intestines. A GASTRIC GLAND, highly magnified. 1, large nucleated cells at the bottom of the gland, gradu- ally merging 2 into the columnar cells 3, at the upper part of the gland. 1 Gastric follicles; glandulae gastricae. Peptic glands. 3 Peptic cells. THE ALIMENTARY APPARATUS. The stomach is very vascular, the blood-vessels reaching it along the line of attachment of its omenta. The gastro-epiploic arteries together form an arch along the greater curvature ; the coronary and pyloric arteries form a second along the lesser curvature, and the short gastric arteries reach the fundus. The branches from these vessels diverge to the surfaces of the stomach, and form together, between its coats, a vas- cular net, from which the capillary nets of the serous, muscular, and mucous coats originate. The veins correspond with the arteries and pursue the same course. The lymphatics are likewise numerous ; their trunks also running along the curvatures. The nerves are derived from the terminal portion of the pneumogastric and the solar plexus of the sympathetic nerves. The liquid elaborated by the glandular structure of the mucous mem- brane is named the gastric juice. 1 Free from foreign matters derived from the food, it is a clear, colorless liquid, rendered slightly viscid from the mixture of mucus, and has a decidedly sour taste. It consists of water holding in solution a peculiar nitrogenized principle named pep- sin, 2 free chlorohydric and lactic acids, and a number of chloride and phosphatic salts. Its operation consists mainly in the solution of albu- minoid substances, such as flesh, cheese, eggs, and the gluten of vege- tables. THE SMALL INTESTINE. The Small intes'tine 3 is a cylindrical and much convoluted tube, occu- pying the umbilical region and continuous borders of the surrounding regions, and suspended by the mesentery from the vertebral column. It measures about twenty-five feet in length, and from one to one and three- quarters of an inch in diameter ; becomes slightly narrower in its de- scent ; and terminates by joining the large intestine. It is divided into three portions : the duodenum, jejunum, and ileum, and although there is no distinct separation between these, each presents some pecu- liarity of character. The Duode'num, 4 as expressed by the name, is about twelve fingers'- breadth in* length, and it is the widest portion of the small intestine. Commencing at the pyloric orifice, it ascends to the right and backward, until it reaches the neck of the gall-bladder. It then abruptly turns 1 Succus gastriciis ; menstruum, or 3 Intestinum tenue ; i. gracile ; intes- fermentum ventriculi ; gastric acid. tines ; small gut ; guts ; enteron. 2 Gasterase; chymosin; the digestive 4 Ventriculus succenturiatus; dodeca- principle. dactylon ; portonarium ; appendix, pro- cessus, or ecphysis ventriculi. 310 THE ALIMENTARY APPARATUS. downward in front of the right kidney, makes another turn to the right side, opposite the second lumbar vertebra, and terminates in the jejunum. The ascending portion of the duodenum has the liver and gall-bladder in front and above it, and after death is usually found stained, with bile exuding from the latter. The descending portion has attached to it, on the left, the head of the pancreas ; and into its lower part the duct of the latter, together with the common biliary duct, opens. The trans- verse portion is behind the transverse mesocolon, and is attached by areolar tissue to the crura of the diaphragm and vessels in front of the vertebral column. Along its upper border is the pancreas, and the su- perior mesenteric blood-vessels cross from beneath the latter over its termination. The Jeju'num 1 and Il'eum 2 are the remaining portions of the small intestine, and though they pass insensibly into each other, the former is viewed as consisting of two-fifths, the latter of three -fifths of the length of the tube. The jejunum is wider than the ileum, feels thicker between the fingers from the more folded condition of its mucous mem- brane, and is further generally characterized by the absence of agminated glands. The ileum terminates in the right iliac region, by joining the large intestine nearly at a right angle. Like the stomach, the small intestine has four distinct coats composing its walls : serous, muscular, fibrous, and mucous. The external or serous coat, derived from the peritoneum, adheres closely around the intestine, leaving only a narrow space along the attachment of the mesentery for the passage of vessels and nerves. The duodenum is invested with peritoneum only at its extremities ; the de- scending and transverse portions, for the most part, being destitute of a serous covering. The muscular coat is composed of two layers of pale-red, unstriated fibres. The external layer consists of thinly-scattered, longitudinal fibres ; the internal layer, thicker and quite distinct, consists of circular fibres. The fibrous coat, less thick than that of the stomach, is nevertheless a strong, extensible layer. The mucous coat, or lining membrane of the small intestine, is thinner and redder than that of the stomach, and, like it, possesses a columnar epithelium. It is thrown into numerous, transverse, crescentic folds or doublings, named val'vulse connivences. 3 These are widest and most abundant in the upper part of the small intestine, where they 1 Nestis. 2 Ileon ; intestinum circumvolutum. 3 V. c. Kerkringii ; plicse conniventes ; Kerkringian valves. THE ALIMENTARY APPARATUS. 311 FIG. 223. even overlap at the edges. In descending, they gradually diminish in number and width ; and in the ileum they become indistinct, and finally disappear. These folds are permanent, and not due to con- traction of the intestinal wall. They increase the extent of ab- sorbing and secreting surface, and further retard the passage of the food. The mucous membrane of the small intestine, including its valvula3 conniventes, is everywhere pro- vided with minute elevations, named vil'li. 1 These give to the surface a velvety appearance, which may be favorably observed, by examining a por- tion of intestine, after it is cleansed from mucus, beneath water. In the Fio. 224. SMALL PORTION OP THE MUCOUS MEMBRANE FROM THE UPPER PART OF THE JEJUNUM, moderately mag- nified. 1, villi. resembling valvulae conniventes in miniature; 2. tubular glands ; their orifices, 3, open- ing on the free surface of the mucous membrane ; 4, fibrous tissue. PORTION OF THE MUCOUS MEMBRANE FROM THE ILEUM, moderately magnified, exhibiting the villi on its free surface, and between them the orifices of the tubular glands. 1, portion of an agminated gland ; 2, a solitary gland ; 3, fibrous tissue. upper part of the small intestine the villi appear as fine, serpentine folds, frequently interrupted in their course, and often conjoined in a reticular manner. Descending the intestine, the fold-like villi become more fre- quently interrupted or broken, and finally, in the ileum, they appear as flattened, conical, or tongue-like processes. The villi are from one-fourth to one-third of a line high, and in struc- ture are processes of the intestinal mucous membrane. Provided with the columnar epithelium, they contain on their interior a capillary net of vessels, in the form of the villi. They likewise contain the commence- ment of those lymphatics called lacteals, but the manner in which these originate has not been satisfactorily determined. According to one 1 Villi intestinales; fiocculi. 312 THE ALIMENTARY APPARATUS. view, they commence as one or two caecal branches for each villus ; and according to a second view, they commence in a reteform plexus. In function, the villi are most efficient organs in the absorption of the nutri- tive matter of the food. Four kinds of glands are found in the mucous membrane of the small intestine : the duodVnal, tubular, solitary, and ag'minated glands. FIG. 225. DIAGRAM OF THE STRUCTURE OF THE MUCOUS MEMBRANE OF THE ILEUM, highly magnified. 1, epithelium forming the free surface of the mucous membrane ; 2, basement membrane; 3, fibrous layer ; 4, villi cov- ered with epithelium; 5, a villus deprived of one-half of its epithelium, and exhibiting through its base- ment layer the blood-vessels ; 6, a villus partially deprived of its epithelium ; 7, villi totally deprived of their epithelium, but retaining their basement membrane; 8, tubular glands imbedded in the fibrous layer of the mucous membrane ; 9, orifices of the tubular glands opening on the free surface of the mu- cous membrane between the villi; 10, section of a tubular gland, with its epithelial lining; 11, tubular glands stripped of the latter, but retaining their basement membrane ; 12, one of the glands in section, without its epithelium ; 13, capillaries surrounding the orifices of the tubular glands; 14, an artery; 15, a vein ; 16, lymphatics or lacteals ; 17, commencement of the latter within the villi ; 18, capillary blood- vessels of the villi. The Duode'nal glands 1 (Brunner's) are small, racemose glands, occu- pying the submucous tissue, and opening into the duodenum. They are most numerous at the commencement of the latter, where they form a nearly continuous layer ; gradually diminishing in number and size, they disappear altogether approaching its termination. The Tubular glands 2 are the most numerous of those of the small in- testine, and are found throughout its whole tract. They are situated 1 Glands of Brunner ; glandulge Brunneri ; second pancreas. 2 Glands, or follicles of Lieberkiilm ; glandulse, or cryptte Lieberkuhnianse ; cryptao THE ALIMENTARY APPARATUS. upright in the thickness of the mucous membrane, and open in the inter- vals of the villi, to which spaces they give a perforated appearance. They are simple, straight glands, provided with a columnar epithelium ; and secrete a clear liquid, called the intestinal juice. 1 Fio. 226. FIG. 227. PORTION OF THE DUODENUM, viewed from without, natural size. 1, thickness of the duodenum; 2,3, longitudinal and transverse layers of fibres of the muscular coat; 4, fibrous coat; 5, exterior of the mucous membrane, with the duodenal glands im- bedded. A VERTICAL SECTION OP THE DUODENUM, highly magnified. 1, a fold-like villus; 2, epithelium of the mucous membrane ; 3, orifices of the tubular glands, 4; 5, orifice of a duodenal racemose gland, 6; 7, two vesicles of the latter, more highly magni- fied, exhibiting the epithelial cells lining their in- ternal surface. The Solitary glands 2 are minute, whitish, oval or rounded bodies scattered singly throughout the small intestine. They are closed vesicles imbedded in the submucous tissue. In structure, they consist of an ex- terior fibrous capsule, containing rounded, nucleated cells, free nuclei, and granules ; and fine vessels penetrate into their interior. Their func- tion is unknown The Ag'minated glands 3 (Peyer's) consist of vesicular bodies like those just described, arranged in elliptical patches. Ordinarily there are from fifteen to thirty of these patches, from half an inch to two inches in length, and about half an inch in breadth. Usually occupying the ileum, they are always situated opposite the attachment of the mesen- tery, with their length parallel to that of the intestine For the most part, the largest patches are the lowest in the ileum, and in ascending 1 Succus entericus. 2 Glandulae solitaries ; incorrectly Brun- ner's glands ; solitary follicles. 3 Peyer's glands ; glandulse Peyeri, or Peyerianse ; g. socise Peyeri ; g. agmina- tae ; g. mucosaa coagminatae ; g. muci- parae racematim congest-ae ; g. intesti- nales plexiformes ; g. plexus intestinales; g. int. spuriae ; g. in agmen congregatse ; corpuscula glandularium similia ; ente- radenes ; aggregate or aggregated glands ; patches of Peyer; Peyer's plaques; ag- minse Peyeri. 314 THE ALIMENTARY APPARATUS. they become more distant, smaller, and more circular. When found in the jejunum, they are few in number, and small in size. Upon the inner surface of the intestine the agminated glands appear depressed below FIG. 228. PORTION OF THE ILEUM, viewed from without ; the Berous and muscular coats removed over the posi- tion of an agminated gland. 1, exterior surface of the ileurn ; 2, cut edge of the serous and muscular coats ; 3, exterior surface of the mucous membrane ; 4, an agminated gland ; 5, valvulas conniventes. PORTION OF THE MUCOUS MEMBRANE FROM THE UP- PER PART OF THE ILEUM, exhibiting very well the appearance presented to the naked eye when the specimen is floated in water. 1, 2, 3, 4, an agmi- nated gland; 5, valvulae conniventes, becoming much contorted over the gland; the short lines everywhere covering the surface of the mucous membrane, including the valvulae and the gland, represent villi ; 6, 7, solitary glands. the general level of the mucous membrane ; but they give rise to a slight prominence externally. The valvulae conniventes, in approaching them, are usually interrupted, or if they pass upon them are reduced in size, and much contorted. Their function is unknown; and they are remarkable for the changes they undergo in certain diseases, as, for instance, typhoid fever. The arteries of the small intestine are numerous, and are derived from the pancreatico-duodenal, pyloric, and superior mesenteric arteries. Diverging from the mesentery upon the intestine, in the intervals of its coats they form vascular nets, from which are derived the three capillary nets of the mucous, muscular, and serous layers. The veins accompany the arteries. The lymphatics are numerous, and are derived from the three sources supplied by the arteries. The nerves are furnished by the solar plexus of the sympathetic system. THE ALIMENTARY APPARATUS. 315 THE LAKGE INTESTINE. The Large intestine 1 is a cylindrical tube, strikingly differing from the small intestine in its greater capacity and sacculated appearance. It is about five feet in length, nearly encircles the abdomen in its course from the small intestine to the anus, and is retained in position by the mesocolon. Commencing in the right iliac region, it ascends in front of the right kidney to the under part of the liver, then crosses through the upper boundary of the umbilical region to the left hypochondriac region. Descending from the latter, in front of the left kidney to the left iliac region, it here forms an S-like convolution, and then dipping into the pelvis, passes down in front of the sacrum to terminate at the anus. It is divisible into three portions : the caecum, colon, and rectum. The Cae'cum or head of the colon 2 is the most capacious portion of the large intestine, and consists of a large pouch occupying the right iliac region below the termination of the ileum. It is retained in po- sition by a fold of the peritoneum reflected in front, and by an attach- ment of loose connective tissue to the iliac fossa ; though sometimes the peritoneum produces a doubling behind which renders the caecum less fixed than ordinarily. The cascum is about two and a half inches in length and breadth, and toward its bottom curves inwardly and backward, and is abruptly re- duced into a worm-like prolongation, named the verm'iform appen'dix. 3 This is four or five inches long, as thick as a goose-quill, and is usually somewhat coiled, in which condition it is retained by a fold of peri- toneum. Its calibre is narrow, and its comparatively thick wall has the same structure as other portions of the large intestine. It is viewed as the rudiment of the much-elongated caecum of lower mammals. The Co'lon 4 is the second and longest division of the large intestine, and extends from the caecum to the rectum. In the different parts of its course it is called the ascending, transverse, and descending colon, and the sigmoid flexure, It is most capacious at its commencement, 1 Intestinum crassum; megalocoelia. formis; processus, or tubus vermicula- 2 Caecum; caput coli; monocolon; mo- ris; appendix caeci; additamentum coli; nomacum; typhloenterum : typhloteron - ecphyas: digital appendix; vermiform, monocolon; initium intestini crassi ; sac- or vermicular process. cus intestini crassi, or coli; prima cella 4 Colum; intestinum crassum et ple- coli; initium extuberans coli; the blind num; i. majus; i. grande; i. laxum; i. g ut - cellulatum ; colon caecum ; monenterum ; 3 Appendix, or appendicula vermi- physce. 316 THE ALIMENTARY APPARATUS. where it is about two and a half inches in diameter, and gradually diminishes to its termination, where it is an inch less in breadth. Tt exhibits three ranges of saccules or pouches, 1 alternating with as many eguidistant longitudinal bands 2 proceeding from the base of the vermi- form appendix. The constrictions between the saccules appear on the interior of the colon as crescentic doublings 3 of its walls. The ascending colon 4 occupies the right side of the abdomen, attached to its posterior wall by loose connective tissue, and further retained in position by the peritoneum passing over the sides and in front of the intestine. Behind, it is in relation with the quadrate lumbar muscle and kidney ; in front with the small intestine. The transverse colon 5 passes obliquely across the abdomen at the upper boundary of the umbilical region. It is closely attached to the back part of both hypochondriac regions, and arches forward toward its middle, where it is loosely suspended by the transverse mesocolon. Above it are the liver and the stomach ; below, the small intestine ; and descend- ing from its outer border is the posterior fold of the great omentum. The descending colon 6 occupies the left side of the abdomen, to the back part of which it is closely attached by connective tissue, and by the peritoneum passing over its sides and front. Its upper part is in contact with the spleen ; behind it are the left kidney and quadrate lumbar muscle ; and in front is the small intestine. The sigmoid flexure of the colon 7 is an S-like convolution of the in- testine attached by a wide fold of peritoneum to the left iliac fossa. It is the narrowest and least sacculated portion of the colon ; and termi- nates opposite the left sacro-iliac symphysis in the rectum. The Il'eo-col'ic valve. The ileum opens into the left side of the colon just above the caecum, the orifice being provided with a pair of semi- lunar folds, which constitute the ileo-colic valve. 8 The folds are trans- verse, and project from the borders of the aperture toward each other into the colon. The free edges of the folds are concave, and their con- tiguous extremities coalesce and are prolonged a short distance as a narrow doubling on the interior surface of the colon. The aperture 1 Cellulse, haustra, or loculamenta coli. 6 Colon descendens ; c. sinistrum ; left 2 Taeniae Valsalvae ; tseniae, or fasciae lumbar colon. ligamentosse coli; ligamenta coli. 7 Flexura sigrnoidea; f. S romanum; 3 Plicae sigmoideae. iliac colon. 4 Colon ascendens; c. dextrum; right 8 Ileo-caecal valve; valve of Bauhin, lumbar colon. of Tulpius, of Fallopius, or of Varolius; 5 Colon transversum; transverse arch valvula ilei; v. coli; v. cooci; opercu- of the colon. lum ilei ; sphincter ilei. THE ALIMENTARY APPARATUS. 317 FIG. 230. separating the folds is elliptical; but when closed, the free edges of the valve come into contact so as to prevent the return of matters from the large into the small intestine. The third division of the large intestine, the rectum, possesses so many peculiarities that its descrip- tion is reserved for a special section of our chapter. The caecum and colon, like the small intestine, have four coats holding the same relationship with one another. The serous coat, derived from the peritoneum, closely invests the colon except at the back part of the caecum, and of the ascending and descending colon. Along its course, it exhibits a series of ir- regular, pendulous pouches con- taining fat, and named the epip r - loic appendages, 1 The muscular coat is composed of two layers of pale-red, unstriated fibres. The external longitudinal fibres, after forming a uniform layer to the vermiform appendix, are collected into three separate bands, which proceed equidistant from one another along the course of the caecum and colon. These bands are much shorter than the intestine would be if deprived of them, and serve to maintain its sacculated condition. The internal muscular fibres are circular, and form a continuous layer to the caecum and colon, dipping into the constrictions between their saccules, and into the folds of the ileo-colic valve. The fibrous coat is like that of the small intestine. The mucous membrane is soft, smooth, and of a pale-pinkish ash color. It is without villi or other doublings than those produced by the constrictions separating the saccules. Its free surface everywhere ex- hibits a finely-punctured or sieve-like appearance, with here and there small whitish spots. It is provided with a columnar epithelium and two THE CJECUM LAID OPEN, TO EXPOSE THE ILEO-C.ECAI, VALVE, a, Termination of the ileum ; 6, slit-like orifice between the two folds of the ileo-cfecal valve ; c, caecum; d, vermiform appendix; e, ascending colon. 1 Appendices, or appendiculae epiploicse, or pinguedinosaB ; appendices coli adi- posse; suplementa epiploica; nmbriae carnosse; omentula. 318 THE ALIMENTARY APPARATUS. FIG. 231. kinds of glands, tubular 1 and solitary glands, 2 which are like those of the small intestine. The former are closely set together in the thickness of the mucous membrane, and give to its free surface the punctured appearance ; the latter are indi- cated by the scattered whitish spots. The blood-vessels of the caecum and colon are branches of the mesenteric arteries and veins. The lymphatics communicate with SECTION OF THE MUCOUS MEMBRANE . - L OF THE COLON, i, free surface exhib- glands lying in the course of the former ves- iting the orifices of the tubular gelg The nerves are derived from the mesen- glands 2; 3, fibrous tissue; moder- ately magnified. teric plexuses of the sympathetic system. THE KECTUM. The Rec'tum, 3 the terminal portion of the large intestine, proceeds from the sigmoid flexure of the colon, opposite the left sacro-iliac sym- physis, and descends along the middle of the sacrum and coccyx, to end at the anus. It follows the curvatures of the bones just mentioned, and from the point of the coccyx turns backward and downward. It is not sacculated like the colon, though' it usually exhibits three constrictions, corresponding with crescentic folds on its interior. It is from six to eight inches long, and when distended is club-shaped, being narrow above and expanded just before it contracts to the anus. In front of it, in the male, are the urinary bladder, seminal vesicles, and prostate gland ; in the female, the uterus and vagina. The a'nus 4 is a dilatable aperture, situated about an inch from the end of the coccyx. It is encircled by a sphincter muscle, covered below by thin, dark-colored skin, gradually merging into the mucous membrane of the rectum. In the condition of rest, this skin is puckered or folded; but in the act of defecation the folds are expanded, and the mucous membrane at the verge of the anus is everted. The upper part of the rectum is invested by the peritoneum, which attaches it to the sacrum by a doubling named the mes'o-rec'tum. Subsequently the peritoneum extends down the sides, and finally only on the front of the rectum, and is thence reflected to the bladder of the 1 Glands or follicles of Lieberkuhn. 2 Solitary follicles; glandulae simplices majores. 3 Intestinum rectum ; longanon ; ar- chos ; cysaros ; princeps ; enthyenteron ; apenthysmenos. 4 Podex ; archos ; sedes ; culus ; proc- tos; molyne; dactylics; cathedra; cyr- ceon ; cysaros ; cysthos ; aphedra ; he- dra ; the seat, fundament, or body. THE ALIMENTARY APPARATUS. 319 male, or the vagina and uterus of the female. The lower part of the rectum is destitute of a peritoneal investment, and is attached to the contiguous structures by areolar tissue, usually accompanied with much adipose tissue. In the male, the portion of the rectum unprovided with peritoneum is in contact in front with the base of the bladder, the seminal vesicles, and the prostate gland ; in the female, it is in contact in the same position with the vagina. The muscular coat of the rectum is much thicker than elsewhere in the large intestine. Its external longitudinal fibres, continuous with the longitudinal bands of the colon, form a continuous and well-marked layer. The circular fibres likewise form a continuous layer, and gradu- ally increase in descending upon the rectum, and finally accumulate in a thick fasciculus, named the internal sphincter of the a'nus. 1 Between the two sphincters of the anus the longitudinal muscular fibres of the rectum terminate, except a few, which turn around the lower border of the internal sphincter and ascend a short distance between it and the mucous membrane. In the same position the rectum is embraced from each side by the insertion of the anal elevator muscles. The fibrous coat of the rectum is thicker than in other portions of the large intestine, and is strong and extensible. The mucous membrane of the rectum has the same structure as that of the colon, but is more vascular, and becomes bright red at the lower extremity. It exhibits many irregular wrinkles, which are obliterated on distention of the bowel. Approaching the anus, it is thrown into con- vergent longitudinal folds, named the columns of the rec'tum, 2 which are often continuous below, so as to form small recesses between them, called the pouches of the a'nus. 3 Corresponding in position with the three constrictions usually observed on the exterior of the rectum, its mucous membrane is provided with as many wide, crescentic folds, which may act the part of a valvular appa- ratus. The arteries of the rectum are the haemorrhoidal branches of the infe- rior mesenteric, internal iliac, and internal pudic arteries. The veins are numerous, and at the lower part of the rectum form an intricate net-work, named the haemorrhoi'dal plexus, which returns its blood through the inferior mesenteric and internal iliac veins. Enlargement of the veins of the haBmorrhoidal plexus at the verge of the anus constitute hemor- rhoids or piles. The lymphatics of the rectum proceed to the sacral and 1 Musculus sphincter ani interims, or superius. 2 Columnae cameos Morgagni. a gi nus Morgagni; lacunae. 320 THE ALIMENTARY APPARATUS. lumbar glands. The nerves are numerous, and are derived from the hypogastric plexus of the sympathetic system and the contiguous spinal nerves. The muscles of the anus will be more particularly described in the account of the perineum. THE PANCREAS. The Pan/creas 1 is a long, flat gland, situated behind the stomach, opposite the first lumbar vertebra. It extends from the descending por- tion of the duodenum in the right hypochondriac region, along the trans- verse portion of the duodenum through the epigastric region, and reaches the spleen in the left hypochondriac region. It closely adheres to the duodenum, and is loosely attached behind by connective tissue to the crura of the diaphragm, aorta, inferior cava, and superior mesenteric vessels. The latter are included in a groove of the gland, and some- times in a complete canal. In front, the pancreas is connected with the ascending layer of the transverse mesocolon ; and its upper border is grooved to accommodate the splenic blood-vessels. The pancreas is pinkish white, and is less consistent and of looser texture than the salivary glands, which it resembles in composition. It is from six to eight inches long, is largest at the right extremity, named its head, 2 and gradually narrows toward the left extremity, named its tail. 3 Its average depth is about one and a half inches; its thickness about half an inch ; and it weighs between two and three ounces. The head of the pancreas adheres closely to the inner side of the de- scending portion of the duodenum, and is frequently partially divided from the body of the gland, when it is named the lesser pan'creas. 4 In structure the pancreas is a racemose gland, and consists of many polyhedral lobes and lobules loosely associated by connective tissue. The pancreat'ic duct 5 usually possesses two principal branches, of which the longer and larger proceeds transversely through the body of the gland from left to right, and is joined near its termination by the smaller branch 6 derived from the head of the pancreas. Upon emerging from the pancreas, the duct penetrates the wall of the duodenum, opening into it near to or in conjunction with the common biliary duct, about four inches from the stomach. 1 Sweetbread; pancratium; pancrene; 3 Cauda. callicreas; lactes; totum carnosum; 4 Pancreas minus; pancreas of Asseli. pulvinar ventriculi ; glandula salivalis 5 Ductus pancreaticus ; d. Wirsungi- abdominis. anus ; canal, or duct of Wirsung. 2 Caput pancreatis. 6 Ductus Santorini. THE ALIMENTARY APPARATUS. 321 The arteries of the pancreas are derived from the pancreatico-duo- denal and splenic arteries. The veins join the splenic and superior mes- enteric veins. Its lymphatics communicate with the lumbar glands, and its nerves are branches from the solar plexus of the sympathetic system. The pancreatic juice 1 is a clear, colorless, slightly viscid liquid, with a distinctly alkaline reaction. It contains a peculiar nitrogenized prin- ciple, named pancreatin, and is an important emulsifying agent of the fatty materials of the food. THE LITER The Liver 2 is the largest true glandular organ of the body. It occu- pies the greater part of the right hypochondriac region, and extends through the epigastric into a small portion of the left hypochon- driac region. It is half ovoidal in shape, with its long diameter trans- verse, its convex surface accurately applied to the diaphragm, and its nearly flat or slightly concave surface in contact with the stomach, duo- denum, colon, and right kidney. In front, it is in relation with the ensi- form and costal cartilages, and behind, with the crura of the diaphragm, aorta, and inferior cava. It is suspended from the diaphragm by reflec- tions of the peritoneum named the suspensory, the right and left lat- eral ligaments, and by a further attachment of connective tissue at its posterior border. The right portion of the liver is much larger than the left, and is thicker, more fixed in position, and extends lowest in the abdomen as well as highest in the thorax. The posterior and right borders are thick and rounded ; the anterior and left borders are thin and acute, and the most movable parts of the organ. The liver is of firm, solid texture, smooth on the surface, and of a reddish-brown color. It often has more or less of a yellowish hue, ap- parently dependent on the presence of fat in the hepatic substance, and sometimes exhibits superficial livid bluish or purplish patches and borders. It weighs between three and four pounds, and measures ten to twelve inches from right to left, about six inches from back to front, and about three inches at its thickest part. In the female it is usually about a fifth less in weight and size. The suspensory ligament, extending from the median line of the dia- phragm to the upper surface of the liver, together with the longitudinal fissure pursuing the same direction on the under surface, divide the organ into two unequal parts, named the right and left lobes. 1 Succus, or liquor pancreaticus. 2 Hepar; jecur; jecinus. 21 322 THE ALIMENTARY APPARATUS. The right lobe of the liver, 1 four or five times the size of the left, is square in outline, and is closely adherent at its posterior border, by con- nective tissue, to the diaphragm, between the widely-separated reflections of the right lateral ligament. Its upper surface is convex ; its lower surface is in contact with the right kidney, the pyloric extremity of the stomach, and the colon. At the fore part of its inferior surface the gall- bladder reposes in a fossa ; 2 and to the left and back of this it presents two small subdivisions named the quadrate and caudate lobes. FIG. 232. 3 INFERIOR SURFACE OF THE LIVER. 1, right lobe; 2, left lobe; 3, posterior margin; 4, anterior margin; 5, quadrate lobe; 6, caudate lobe; 7, isthmus, or caudate process, connecting the latter with the right lobe; 8, 9, longitudinal fissure; 10, transverse fissure; 11, portal vein; 12, hepatic artery; 13, common biliary duct formed by the union of the hepatic and cystic ducts; 14, gall-bladder; 15, inferior cava; 16, hepatic veins ; 17, round ligament ; 18, anterior part of the suspensory ligament. The left lobe of the liver 3 is comparatively thin, trilateral in outline, and movably suspended by the left lateral ligament. Its lower surface is in contact with the anterior part of the stomach, and behind, it is in relation with the cardiac orifice of this organ. Besides the suspensory ligament and longitudinal fissure, the right and left lobes are separated at the anterior and posterior borders of the liver by notches. The anterior notch is acute, and continuous below with the longitudinal fissure ; the posterior notch is broad and concave, and ac- commodates the vertebral column and the great blood-vessels in front of it. The inferior cava occupies a deeper portion of the posterior notch, excavated in the right lobe of the liver ; and sometimes the hepatic sub- stance extends around the vein so as to inclose it in a complete tube. 1 Lobus dexter; large, or colic lobe. 2 Fossa longitudinalis dextra. 3 Lobus sinister. THE ALIMENTARY APPARATUS. 323 Above the posterior notch, the two layers of the suspensory ligament diverge 1 and become continuous with the anterior reflections of the lat- eral ligaments, leaving a triangular interval at which the liver is attached to the diaphragm by connective tissue. The Longitudinal fissure 2 is a deep groove on the under part of the liver extending between the anterior and posterior notches, and separat- ing the right and left lobes. Its fore part 3 is frequently crossed by a bridge 4 of hepatic substance, and it contains a fibrous cord named the round ligament, 5 which is the obliterated umbilical vein of foatal life. Its back part 6 also contains a fibrous cord, which is the obliterated due- tus venosus of the foetus. The Transverse fissure 7 is a deep groove passing at a right angle from the longitudinal fissure, between the quadrate and caudate lobes, to ter- minate on the under part of the right lobe. This fissure is the position at which the blood-vessels and nerves enter the liver, and the lymphatics and excretory duct emerge. The Quadrate lobe of the liver 8 is a square portion of hepatic sub- stance situated between the gall-bladder on the right and the longitudi- nal fissure on the left, and extending from the anterior border of the organ back to the transverse fissure. The Caudate lobe 9 is a small blunt pyramidal mass of hepatic sub- stance behind the transverse fissure, extending to the posterior notch of the liver, and having to its left the longitudinal fissure, and to its right the groove for the inferior cava. A short isthmus or caudate process 10 associates it, in front of the latter vessel, with the under surface of the right lobe. 1 This divergence is usually and incor- jecoris ; manus hepatis, or jecoris ; prin- rectly described as if it were a distinct cipal fissure ; fissure or fossa of the structure, under the name of the coro- portal vein ; portal fissure or fossa. nary ligament ; 1. coronarium. a Lobulus quadratus ; 1. anonymous ; 2 Great, or horizontal fissure, furrow, 1. accessorius anterior quadratus ; ante- orsulcus; fossa umbilicalis ; sulcus an- rior portal eminence; auriga anony- tero-posterior jecoris; sulcus sinister, or mous. umbilicalis jecoris. 9 Lobulus Spigelii ; the Spigelian lobe; 3 Fossa longitudinalis sinistra. lobulus porticus papillatus; tuberculum 4 Pons, or isthmus hepatis. papillare ; posterior portal eminence ; 5 Ligamentum teres. Small5 duodenal, or pancreatic lobe. 6 Fossa ductus venosi. 10 Lobulus caudatus ; lobus, or proces- ' Sulcus transversus; fossa transversa; 8US cau datus ; tuberculum caudatum. sinus portarum ; porta ; p. hepatis, or 324 THE ALIMENTARY APPARATUS. The liver derives its blood from two different sources, in this respect being quite peculiar among the organs of the body. It is supplied with red blood by a proportionately small vessel, the hepatic artery, and is provided with dark blood by a larger vessel, the portal vein, The two vessels together enter the transverse fissure of the liver, the artery in front of the vein, and both divide into two branches, which pass to the right and left lobes, and ramify through them in a divergent manner from below upward, and toward the borders of the organ. The bile ducts, 1 originating in the hepatic substance, converge in the course of the vessels just mentioned, and emerge into the transverse fissure of the liver ; a branch from the right and another from the left lobe conjoining to form the trunk of the hepat'ic duct. Numerous lymphatics, and nerves from the pneumogastrics and sym- pathetics, pursue the same course as the above-mentioned blood-vessels and ducts, the whole together being enveloped by connective tissue. 2 The hepatic veins collect the blood from the substance of the liver and return it to the general circulation. Commencing at the periphery of the organ, they emerge from before backward, and terminate, at the posterior notch of the liver, in two principal trunks which join the infe- rior cava. The relative position of the hepatic veins with the other vessels of the liver bears a resemblance to a prostrate tree whose boughs and branches are entangled among those of a clump of upright trees. STRUCTURE OF THE LIVER. The liver is closely invested with a serous coat derived from the peri- toneum, which everywhere covers it except along the posterior border, in the intervals of the suspensory and lateral ligaments, and at the bot- tom of its fissures. The subserous connective tissue 3 is feebly developed, but a stronger and distinct extension of the same structure invests those portions of the liver which are destitute of peritoneum. In the trans- verse fissure the investing connective tissue of the liver is continuous with that enveloping the vessels and ducts. The material composing the liver, and named the hepat'ic substance, 4 has a reddish-brown color tinged with yellow, and has a finely and uni- formly mottled aspect, which is much more evident in some of the infe- 1 Biliary ducts ; pori biliarii ; ductus biliarii. 2 Capsule of Glisson ; c. communis Glissoni ; vagina portse ; v. Glissoni. 3 Tunica propria. 4 Parenchyma hepatis ; parenchyma of the liver. THE ALIMENTARY APPARATUS. 325 rior animals than in man, as for instance in the hog. It is readily torn, and in this condition presents a coarsely granular appearance. The coarse granules corresponding with the distinct spots seen on the surface of the liver are polyhedral, from half a line to one line in diameter, and are named the lob'ules of the liver. 1 FIG. 233. FIG. 234. Fig. 233. PORTION OF THE LIVER OF THE HOG, exhibiting the lobular structure and the section of a he- patic vein, somewhat magnified, a, Large branch of the hepatic vein ; the orifices belong to other branches; ft, branches exhibiting through their thin walls the outlines of the lobules; the dots in the centre of the latter are orifices of the veins commencing within the lobules. Fig. 234. PORTION OF THE LIVER OF THE HO, exhibiting the lobular structure. The large vessel is a branch of the portal vein, the outlines of the lobules being seen through its transparent wall. The ori- fices, large and small, seen in the portal vein, are fine branches sent between the lobules. The two vessels lying to the left of the portal vein are branches of the hepatic artery and duct. In tracing the relation of the hepatic lobules with the blood-vessels and ducts of the liver, it is found that an extreme branch 2 of the hepatic veins commences in the axis of every lobule, and emerges at its base to join a larger branch. 3 This arrangement of the hepatic lobules and veins resembles the attachment of leaves by their midribs and stems to the branches of a tree. The portal vein, hepatic artery, and hepatic duct, associated together by connective tissue, 4 ramify through appro- priate canals 5 of the hepatic substance, pursuing the same general course 1 Acini. 2 Intra-lobular vein ; vena centralis. 3 Sub-lobular vein. 4 Capsule of Glisson. 5 Portal canals. 326 THE ALIMENTARY APPARATUS. FIG. 235. in relation with the branches of the hepatic veins which has been indi- cated in the account of the arrangement of their trunks. Finally, the portal vein, hepatic artery, and the bile ducts ramify in the interspaces 1 of the lobules, forming plexuses, 2 and associating the latter together. In the human liver, these interven- ing vessels are the chief connection of the lobules with one another; but in some of the lower animals, as for instance the hog, they are accompanied with a much greater quantity of connective tissue, which renders the outlines of the lobules more defined. Between the terminal branches 3 of the portal vein and hepatic ar- tery, occupying the intervals 4 of the lobules and the commencing branches 5 of the hepatic veins in the axis of the latter, intricate ca- pillary vascular nets 6 intervene. Thus the blood which enters the liver by the portal vein and hepatic artery pursues its course until it arrives in the intervals of the lob- ules, when it meanders through the capillary nets to the commencement of the hepatic veins in the interior of the lobules. The meshes or interspaces of the capillary vascular nets are occupied by the proper secreting substance of the liver, constituting the hepatic cells. 7 These are irregularly polyhedral, from the ^oo to tne TZHJO f an inch in diameter, with soft granular contents, some minute oil glob- ules, and a nucleus. Generally, two hepatic cells are about equal to the diameter of the meshes they occupy, though frequently a single cell is observed extending across the interval. From the description given, it may be readily comprehended that the hepatic lobules are composed of capillary vascular nets, intercalated SECTION OF SEVERAL LOBULES OF THE LIVER OF THE BABBIT, the vessels injected, and the preparation magnified. The intricate capillary net-works are formed from the portal veins between the lobules, and the hepatic veins within them. 1 Interlobular spaces. 2 Interlobular veins, arteries, and ducts. 3 Interlobular veins and arteries. 4 Interlobular spaces. 5 Intralobular veins. 6 Lobular plexuses. 7 Liver cells; hepatic corpuscles. THE ALIMENTARY APPARATUS. 327 FIG. 236. with hepatic cell-nets, as represented in the diagram, figure 237. So far, anatomists concur in their observations on the structure of the liver ; but in regard to the exact relationship of the hepatic cell-nets with the bile ducts 1 there exists much conflict of opinion. According to one view, the hepatic cell-nets are solid, and the bile ducts originate at the bound- aries of the lobules. In a second view, intercellular passages of the hepatic cell-nets communicate with the commencement of the bile ducts in the interspaces of the lobules. According to a third view, a third net, composed of very fine tubes of basement membrane, is intercal- lated with the capillary vascular, and hepatic cell nets, and joins the bile ducts in the interspaces of the lobules. Finally, in a fourth view, as in other true glands, the hepatic cells are considered as lining tubes of basement membrane, from which the bile ducts originate in the intervals of the lobules. POLYHEDRAL EPITHELIUM, exemplified by secret- ing cells of the liver. The arrangement is ideal. 1, space occupied by a blood-vessel; 2, isolated cells. FIG. 237. Fig. 237. DIAGRAM REPRESENTING THE SECTION OF A LOBULE OF THE LIVER, exhibiting the relative position of the hepatic cell-nets with the vascular nets. 1, section of a hepatic vein in the centre of a lobule ; 2, branch of the portal vein at the cir- cumference of the lobule ; 3, capillary net formed between the portal and hepatic veins ; 4, branch of the hepatic artery ; 5, hepatic cell-net in the inte- rior of the lobule ; 6, a bile duct at the boundary of the latter. Fio. 238. Fig. 238. DIAGRAM REPRESENTING A TRANSVERSE SECTION OF ONE OF THE CORDS OF THE HEPATIC CELL- NET, showing how a few cells may form a hollow tube. 1, large cell ; viewed from this side the tubes would appear to be the breadth of a single cell ; 2, two cells the diameter of the tube; 3, passage-way for the bile. 1 Interlobular ducts ; pori biliarii. 328 THE ALIMENTARY APPARATUS. BILIARY DUCTS AND GALL-BLADDER. The Hepat'ic duct, 1 commencing by two branches in the transverse fissure of the liver, descends within the right border of the gastro- hepatic omentum, in advance of the portal vein and to the right of the hepatic artery. It is about two inches in length, and terminates, by joining with the cyst'ic duct from the gall-bladder, to form the common bil'iary duct, The Gall-bladder, 2 the receptacle of the bile, is a pyriform sac, par- tially lodged in a fossa on the under part anteriorly of the right lobe of the liver. Its fundus or base projects beyond the anterior border of the latter, in the vicinity of the tenth costal cartilage ; and its body or main portion extends in a backward direction. Its neck forms an S-like con- volution, and terminates at the transverse fissure by becoming the cyst'ic duct, The gall-bladder is attached in its fossa of the hepatic substance by connective tissue, and its free part, including the fundus, is covered by the peritoneum. Independent of the latter membrane, its wall is pro- vided with a strong layer of fibrous tissue, and a thin, diffuse stratum of pale unstriated muscular fibres. Its lining mucous membrane, stained yellow from the bile, is uniformly covered with fine reticular folds, and has a columnar epithelium. The gall-bladder is supplied with blood, by the cystic artery, a branch of the hepatic. Its veins terminate in the portal vein. The Cyst'ic duct 3 is about an inch in length, and descends to the left to join the hepatic duct at an acute angle. Its lining membrane is thrown into a series of oblique folds, forming a sort of spiral valve, 4 which retards the flow of the bile. The Common bil'iary duct, 5 formed by the conjunction of the hepatic and cystic ducts, is about three inches long, and of the diameter of a large goose-quill. Continuing along the right border of the gastro- hepatic omentum, it pursues its course behind and to the inner side of the descending portion of the duodenum, and terminates in the latter, about four inches from the stomach. Its lower portion is involved in the head of the pancreas, and then perforates the wall of the duodenum 1 Ductus hepaticus. 4 Valvulus spiralis Heisteri. 2 Vesicula bills ; v. or folliculus fellis ; 5 Ductus communis clioledochus ; d. vesica fellea ; v. biliaria ; cystis fellea ; choledochus ; d. hepato-cysticus ; chole- cholecystis. dochus ; common bile duct. 3 Ductus cysticus ; meatus cysticus. THE ALIMENTARY APPARATUS. 329 obliquely. Its orifice is narrowed, and opens at the summit of a slight papillary eminence. The common biliary, cystic, and hepatic duct and its branches have the same structure. They have a strong fibrous coat, with a few unstri- ated muscular fibres, and a lining mucous membrane. The latter is pro- vided with many minute racemose glands ; and it has a columnar epithe- lium, except in the small bile ducts, where the epithelium assumes the tesselated form. The secretion of the liver, named the bile, 1 as obtained from the human gall-bladder, is a thin, glairy, dark, yellowish-brown liquid, of bitter taste, and nearly neutral in reaction when fresh. It is exceed- ingly complex in chemical composition; and though an abundant se- cretion, and a very constant one in animals, its uses have not yet been satisfactorily determined. THE SPLEEN. The Spleen 2 is a half-ovoidal body, deeply situated in the left hypo- chondriac region. It is of comparatively soft consistence, and of a livid, purplish color. Its long diameter is vertical, with the larger extremity upward and attached to the diaphragm by a doubling of peritoneum, the suspensory ligament. Its external convex surface is directed toward the left side, and is in contact with the diaphragm opposite the three or four lower ribs. Its internal surface, slightly depressed in front and behind and elevated toward the middle, is directed to the right side, and applied to the fundus of the stomach, to which it adheres by the gastro- splenic omentum. Its posterior border is thick and rounded, and rests against the contiguous kidney and the diaphragm ; its anterior border is thinner, and at the lower part usually exhibits one or two notches or clefts. Along the middle of the internal surface of the spleen, usually indi- cated by a slight groove named the hilus, 3 the splenic vessels and nerves pass to and from the organ. The spleen is very variable in size, even in the condition of health, and is liable to great changes in this respect in certain diseases. Ordin- arily it is four or five inches long, three or four broad, and from one to one and a half thick ; and weighs about six ounces. The spleen is provided with two coats, of which the outer is serous, 1 Bills ; cholos ; fel ; the gall. 2 Lien ; splen ; hepar sinistrum ; h. adulterinum ; fomes ventriculi ; milt. 3 Porta lienis. 330 THE ALIMENTARY APPARATUS. and the inner one fibre-elastic. The serous coat derived from the peri- toneum is thin, transparent, smooth, and tightly adherent to the contigu- ous structure beneath. The fibro-elastic coat 1 is a moderately strong, extensible layer, com- posed of interlacing bundles of fibrous tissue mingled with fibres of elastic tissue. At the hilus it becomes continuous with a similar investment to the splenic blood-vessels as they ramify through the organ. The spleen is easily torn ; its lacerated surface presenting a deep red- dish-black, or brown, pulpy appearance, resembling coagulated blood or dark currant-jelly. This dark substance, named the splenic pulp, 2 may be scraped from the torn surface, or it may be removed from portions of the spleen by maceration or repeated washings, leaving a spongy mass, composed of the splenic blood-vessels, associated with numerous bundles of fibro-elastic tissue. These bundles, named trabec'ulae, spring from the interior surface of the fibro-elastic coat of the spleen, and form an intricate net- work or sponge-like arrangement which supports the splenic blood-vessels and contains within its meshes the splenic pulp. The pulp of the spleen, examined with the microscope, is found to consist of the following elements : 1, numerous blood-corpuscles, for the most part unchanged, but many apparently exhibiting various condi- tions of disintegration ; 2, finely granular matter, partly colorless, but mostly of various shades of red passing into brown ; 3, numerous iso- lated nuclear bodies ; 4, colorless nucleated cells ; 5, a few cells contain- ing blood-corpuscles apparently in a state of disintegration ; and 6, occasionally red acicular crystals, derived from the decomposition of blood-corpuscles. The arrangement of these different elements of the splenic pulp, in their relationship with one another and with the blood-vessels, has not yet been determined in a satisfactory manner. Adhering to the sides of the smallest arteries of the spleen, and im- bedded in the pulp, there exist certain small, rounded, whitish bodies, named splenic corpuscles. 3 These are variable in number and size, usually measure about one-sixth of a line in diameter, and resemble, in composition, the solitary glands of the intestines. In proportion to its size, the spleen is the most vascular organ of the body. The splenic artery divides into a half dozen or more branches, which diverge along the hilus and enter the spleen. Spreading through the organ in numerous ramifications, those of the different principal branches, not anastomosing, they finally break up into a multitude of 1 Tunica propria ; t. albuginea. 2 Pulpa lienis. 3 Corpuscles of Malphighi ; Malphighian bodies. THE ALIMENTARY APPARATUS. 331 pencil-like bundles of delicate vessels, which terminate in the capillaries of the splenic pulp. The veins return in the course of the arteries, with which they correspond in number, but are larger. The lymphatics are few in comparison with those of the other abdominal viscera. The nerves are derived from the solar plexus of the sympathetic system. The function of the spleen, though the subject of numerous and laborious investigations, yet remains unknown. It has been supposed that the spleen acts as a reservoir or diverticulum to the blood during the state of rest of the digestive organs, and during those conditions in which the blood retires from the surface toward the interior of the body. It has also been looked upon as being the position in which the blood-corpuscles, after having fulfilled their function in the economy, undergo dissolution, yielding their chemical elements to the circulating liquor sanguinis. Further, it has been supposed to be the organ in which the blood-corpuscles have their origin. CHAPTER YIL THE VASCULAE SYSTEM. THE Vas'cular system consists of the heart, blood-vessels, lymphatics, and their contained liquids, the blood and lymph. The heart is a power- ful muscular organ, and is the chief agent in the circulation of the blood. The blood-vessels consist of branching tubes, named arteries and veins, and an intermediate set of tubes, called capillaries. The lymphatics consist of vessels and peculiar bodies, named lymphatic glands. GENERAL CHARACTERS OF THE ARTERIES. The Ar'teries 1 are cylindrical, membranous tubes, which commence in two great trunks, the aorta and pulmonary artery. They undergo divi- sion as in the branching of a tree, and distribute the blood throughout the body, terminating in the capillaries. Their branches mostly come off at acute angles, are commonly of uniform diameter in each case, but successively diminish after and in consequence of division ; and in this manner gradually merge into the capillary system. As a general rule, the combined area of the branches is greater than that of the vessel from which they emanate, and hence the collective capacity of the arterial system increases with its distribution. This arrangement facilitates the circulation ; for the increasing capacity of the vessels in their course compensates for the retarding influence of friction. Arteries have comparatively thick walls, and even when emptied, as is usually the case after death, they for the most part maintain their open calibre. Generally they pursue a straight course, but are often curved, and are sometimes tortuous, especially in positions liable to frequent change of volume, or of expansion and contraction ; as in the lips, the urinary bladder, the uterus, etc. The larger arteries are generally deeply situ- ated, and frequently pursue their course along the bones, where they are protected from undue extension. In the limbs they occupy the sides of 1 Sing. : arteria ; pi. : arterije. (332) THE VASCULAR SYSTEM. 333 flexion, where they are less exposed to a variety of accidents than if situated on the sides of extension. Arteries, in their course of distribution, form intercommunications, named anastomo'ses, 1 which become more frequent as the vessels diminish in size. Even in many large vessels anastomoses are numerous, where it is important that the blood should be incessantly supplied to organs, as in the case of the arteries of the brain ; or where the vessels are constantly exposed to the liability of pressure, as in the arteries of the hand and foot, those around the joints, and those of the abdominal viscera. The arteries are highly elastic, being extensible and retractile both in length and breadth. During life, from their being provided with mus- cular tissue, they are also contractile. The walls of the arteries are composed of three coats, which vary in vessels of different sizes. FIG. 239. TRANSVERSE SECTION OF THE VTALLS OF THE AORTA, treated with acetic acid, and magnified. 1, internal coat : a, epithelium and basement membrane ; b, c, layers of elastic tissue. 2, middle coat : d, layers of elastic tissue ; e, muscular and connective tissue. 3, external coat, composed of fibrous tissue and fine nets of elastic tissue. The external coat 2 is comparatively thin in the largest arterial trunks ; increases to half the thickness of the walls in the medium-sized arteries ; becomes relatively thicker in the smaller branches ; but finally disappears in those which merge into the capillaries. It is mainly com- posed of fibrous tissue, the bundles and filaments of which pursue a spiral direction, crossing one another from opposite sides of the vessel. Its exterior portion is of looser texture, and adheres to the surrounding parts ; its interior portion is intimately blended with the middle coat. It contains fine nets of elastic tissue, which are most abundant toward the interior. To this coat the arteries chiefly owe their tenacity. 1 Interosculations ; inosculations ; reuniones vasorum ; exanastomoses ; concursi. 2 Tunica adventitia ; t. externa ; t. cellularis ; vagina cellularis. 334 THE VASCULAR SYSTEM. The middle coat 1 forms the principal thickness of the walls of the largest arterial trunks, gradually diminishes in their branches, and finally disappears. In the largest arteries it is of a yellowish color, and is mainly composed of elastic tissue, with a small proportion of unstriated muscular tissue and some connective tissue. In the medium-sized and smaller arteries it is of a reddish hue, and chiefly consists of muscular tissue, with a small proportion of elastic and connective tissue. In the smallest arteries the middle coat consists alone of muscular tissue. FIG. 240. FIG. 241. i ELASTIC TISSUE FROM THE MIDDLE COAT OF THE POPLITEAL ARTERY, highly magnified. The dark reticnlar lines indicate a narrow net of elastic tis- sue ; the other part of the figure represents a layer of perforated membrane, which is a variety of the same tissue. UNSTRIATED MUSCULAR FIBRES FROM THE MIDDLE COAT OF THE ARTERIES, highly magnified. 1, from the popliteal artery : a, without, and 6, treated with acetic acid ; 2, from a branch of the anterior tibial artery : a, pointing to the centre in all the figures, indicates the nucleus. The elastic and muscular tissues are arranged in layers varying in number according to the thickness of the coat, and their fibres pursue a circular course around the vessels. The muscular fibres are fusiform, with elongated oval nuclei. The elastic tissue exhibits all varieties of form, from fine nets to broad-banded ones, constituting the so-called perforated or fenes'trated membranes, To the middle coat arteries owe their contractility, most of their elasticity, and much of their strength ; though it is of such a brittle character that the application of a ligature cuts or breaks it through. The internal coat 2 of the arteries is the thinnest, most transparent, and elastic. It is composed of a lining epithelium, a basement membrane, T. media ; t. elastlca. 2 Tunica intima ; t. glabra ; endangium. THE VASCULAR SYSTEM. 335 and layers of elastic tissue. The epithelium consists of a single layer of elongated, lozenze-shaped cells, which are narrowest in the smallest arteries. The basement membrane is homogeneous and elastic, and is the last structure of the arteries becoming continuous with the capillaries. The elastic tissue consists of fibres, nets, and the so-called perforated membranes, pursuing a longitudinal direction, and intimately associated with the middle coat. The larger arteries have their walls furnished with nutrient vessels, which are derived from small neighboring arteries, and not from the trunks they supply. The nutrient vessels form a net-work of capillaries, from which veins arise to empty into the contiguous larger venous branches. The arteries are accompanied by many nerves, chiefly from the sympathetic system, but to what extent their walls are supplied by them has not been satisfactorily determined. The elasticity of the arteries allows them to dilate as each impulse of the heart sends an additional supply of blood to their circulating current. The dilatation moves rapidly onward in a wave-like manner, and insen- sibly decreases until it is entirely lost in the smallest arteries. It is followed by contraction of the arterial walls upon their contents, both in consequence of their elasticity and the excitation of their muscular structure. The alternation of dilatation and contraction of the arteries constitutes pulsation or the pulse. 1 GENERAL CHARACTER OF THE VEINS. The Veins 2 are branching tubes like the arteries, but are generally larger, more numerous, and consequently more capacious. They com- mence in the capillary vessels, gradually converge in a reverse course mostly along side of the arteries, and, with one exception, terminate in the heart by seven trunks. Four of the latter are the pulmonary veins ; the two largest ones are the superior and inferior cava, and the smallest is the coronary vein, derived from the walls of the heart itself. The ex- ception is the portal vein, which derives its branches from the bowels, and is distributed through the liver. The larger veins consist of a superficial and deep series; the former unassociated with arteries, and running immediately beneath the skin, the latter usually accompanying the arteries, and thence named com- panion veins. 3 The arterial trunks and their large branches generally 1 Pulsus ; pulsatio ; ictus, or incursus arteriarum. 2 Sing. : vena ; pi. : venae ; phlebs. 3 Venae satellites ; v. comites ; v. concomites. 336 THE VASCULAR SYSTEM. have one companion vein ; but the medium-sized and smaller arteries usually possess a pair, arranged one on each side of the artery. Anastomoses between veins of comparatively large size are much more frequent than among corresponding arteries ; and in some positions they form coarse, intricate nets, named venous plexuses, The veins have much thinner, but relatively stronger, walls than the arteries, and, after death, according to the quantity of their remaining contents, are found collapsed. Many of the larger ones are provided with valves, which are so arranged as to prevent the reflux of blood. The valves are usually in pairs, opposite each other, and consist of crescentic doublings of the lining membrane of the veins, strength- ened with some intervening fibro- elastic tissue. The convex border of the valves is attached ; the con- cave border is free, and directed from the periphery of the body toward the heart. Behind each valve the vein is dilated into a pouch or sinus, which prevents the adherence of the valve to the side of the vein when the blood pursues its proper course. If the vein is compressed, the blood driven back enters the sinus and presses the valve inward, so as to meet the opposite one in the middle of the channel, and thus close it. The pulmonary veins throughout possess no valves, and this also is the case with the superior and inferior cava, the portal vein and its branches, the hepatic, renal, uterine, and spinal veins, and most of those of the head and neck. They are more abundant in the veins of the lower than in those of the upper extremities. In certain membranes and some other organs, channels exist lined with an extension of the internal coat of the blood-vessels, and serving the function of veins. These channels are usually termed venous sinuses, as the sinuses of the dura mater, those of the bones, and of the uterus. The walls of the veins, as in the arteries, are composed of three coats, having the same general character. The external coat is the thickest, and gradually increases in this respect from the smallest to the largest veins. As in the arteries, it con- sists of fibrous tissue, with longitudinal nets of elastic tissue. In the DIAGRAMS EXHIBITING THE ARRANGEMENT OF THE VALVES OF VEINS. A, vein laid open, showing the valves in pairs ; B, longitudinal section of a vein, indicating the mode in which the valves, by appo- sition of their free edges, close its calibre. The di- lated condition of the walls behind the valves is also seen. C, vein distended, showing how the sinuses behind the valves become dilated. THE VASCULAR SYSTEM. 337 larger veins of the abdominal cavity it is also provided with tmstriated muscular tissue, the lamina of which pursue a longitudinal direction. The middle coat is best developed in the medium-sized veins, and dis- appears altogether in the smallest ones. As in the arteries, it consists of unstriated muscular, elastic, and connective tissue, the elements of which usually pursue a circular direction, though laminae of the elastic tissue also have a longitudinal direction. In the largest veins the middle coat contains a large proportion of connective tissue, and is sparingly provided with muscular tissue. The internal coat, like that of the arteries, consists of a lining epithe- lium, an elastic basement membrane, and longitudinal laminae of elastic tissue, which, however, do not form fenestrated membranes. The walls of the veins are furnished with nutritive vessels. A few nerves have been traced only in the larger veins. Both arteries and veins are insensible to painful impressions in a condition of health. The acute pain often evinced in the ligation of an artery is due to the inclu- sion of accompanying nerves. THE CAPILLARIES. The Capillaries 1 are minute blood-vessels usually arranged in the form of nets among the proper tissue elements of the organs of the body. They communicate with the termination of the arteries and the commencement of the veins, but are otherwise closed, or never commu- nicate by open orifices with the structures in which they are distributed. The proper tissue elements are in all cases exterior to the capillary ves- sels, or occupy the meshes of the capillary nets ; and they obtain their nutritive material simply by imbibition through the walls of the capil- laries. In any special structure the capillaries are remarkable for the general uniformity of their size, but in the different structures of the body they range from the ^Jy to the yj^ of a line in diameter. The smallest ad- mit the passage of blood corpuscles, though but a short time has elapsed since the opinion universally prevailed that in all structures of the body capillaries 2 existed which only transmitted the liquor sanguinis. In structure the capillaries consist of tubes of transparent, elastic, structureless membrane with scattered oval nuclei. There is no lining epithelium, but only the single layer of membrane just described, which 1 Vasa capillaria ; micrangia ; trichangia. 2 Vasa serosa. 22 338 THE VASCULAR SYSTEM. FIG. 243. is continuous with the basement layer of the internal coat of the arteries and veins. The form of the capillary nets is in a measure dependent upon the ar- rangement of the proper elements of the tissues they supply. Thus, in the lungs, the nets accommo- date themselves to the form of the air-cells ; in the muscles, they have elongated meshes, most of the vessels pursuing the course of the muscu- lar fibres, and being con- nected by short ones crossing the latter, etc. In many instances, es- pecially within papillary eminences, the capillaries form loops, as in the pa- pillae of taste and of touch. The greater the vital activity of an organ, the more dense or close is the capillary net ; or, in other A SMALL ARTERY gradually passing into the structure of the ca- words the greater is its pillary vessels. 1, artery with transverse muscular fibres : a, struc- , _ ' . tureless membrane ; 6, nuclei of transverse muscular fibres ; c, nu- degree 01 VaSCUlanty. 1 he clei of structureless membrane; 2, 3, 4, capillaries composed of capillary net Or pleXUS is structureless membrane (a) with scattered nuclei (d). -, , . , , 1 . , closest in the lungs, the glands, especially the liver and kidneys, the skin and mucous membranes, the muscles, and the gray nerve substance. In the fibrous tissues and the bones the nets have wide meshes, and, of course, comparatively few vessels. THE BLOOD. The Blood 1 constitutes the circulating contents of the heart, arteries, capillaries, and veins. It is a highly complex liquid, furnishing nutritive material to all the tissues of the body. It is somewhat viscid, and heavier than water its specific gravity being about 1055. When fresh, it appears to the naked eye perfectly homogeneous, and of a more or Sanguis ; cruor ; haema ; lapis animalis. THE VASCULAR SYSTEM. 339 FIG. 244. less deep-red hue. It has an alkaline reaction, a saline taste, and a feeble peculiar odor. Its color varies in different vessels, and according to its degree of accumulation. A thin stratum always appears light red, and the color is deepened by an increase in the thickness of the stratum. In the pulmonary veins, the renal veins, the aorta and its branches, it appears bright red ; in the superior and inferior cavae and their branches generally, in the portal veins and the pulmonary arteries, it resembles in color the pulp of the black-heart cherry, or is of a deep- maroon hue. The amount of blood in the adult varies with the bulk and organic activity of the individual, but may be stated to be about equal in weight to one-tenth of the body. When the blood is examined by means of the microscope, spread in a thin layer on a plate of glass, or while circulating in the capillaries, it is observed to consist of a color- less liquid, named the liquor sang'- uinis, and a multitude of minute circular bodies called blood cor'- puseles. 1 These are of two kinds, red and colorless corpuscles, of which the former very greatly pre- dominate and give to the blood its color. The red blood cor'puscles 2 are so exceedingly small and numerous that a single drop of blood a couple of lines in diameter con- tains about 100,000,000 of them. They are biconcave disks with rounded borders, resembling in shape the familiar article of food commonly known as the water cracker. They vary in diameter, but average about the 3 J3 of a line in breadth, with about a fourth of that thickness. They are elastic, and appear homogeneous, presenting no trace of gran- ular contents or nucleus. Isolated, they appear of a yellowish hue, and it is only by their accumulation that they give rise to the decided red color of the blood. Through evaporation of the containing liquid, as exposed upon the slip of glass on which the blood corpuscles are observed, they assume a 1 Blood globules, or vesicles; globuli, vesiculse, sphaerulae, corpuscula, folliculi, cellulge, particulae, or granula sanguinis. 2 Blood disks RED BLOOD CORPUSCLES, highly magnified. 1, cor puscles seen on their broad surface; 2, seen on their edge ; 3, rolls of corpuscles, indicating the manner in which they are frequently observed to arrange themselves. The remaining figures more highly magnified : 4, corpuscle seen on its broad surface ; 5, seen on its edge ; 6, a series of corpuscles ; 7, a corpuscle in section, indicating its biconcave dis- coidal form. 340 THE VASCULAR SYSTEM. tuberculated and irregular stellated appearance. In water they swell up, become paler and spherical, and finally burst, exuding a faintly-colored liquid, and leaving a structureless membrane of extreme tenuity behind. When viewed in any quantity on a glass slide beneath the microscope, the blood corpuscles are frequently observed with a disposition to ar- range themselves into piles or columns, a tendency which becomes more marked in the blood of inflammation. The size, form, and constitution of the red blood corpuscles vary in different animals. In all mammals except the camel tribe, they are cir- cular, and have the same constitution as in man, but are generally smaller. In the elephant they are larger, though there is no general relationship between the size of the corpuscles and that of the animal ; thus, they are larger in the rat than in the horse, and are smallest in the musk deer. In the camel tribe, birds, reptiles, and fishes, they are elliptical, and are provided with a nucleus. In the batrachian reptiles they are larger than in any other animals ; thus, in frogs they measure the ^ of a line long ; in salamanders, -$ ; and in the proteus, ^ of a line. The colorless blood corpuscles 1 are comparatively few in number not more than one to several hundred of the red corpuscles. They are larger than the latter, and measure about the 2 ?^ of a line in diameter, are spherical, and have faintly granular contents and a nucleus. Most of the colorless corpuscles are derived from the lymph, which, as will hereafter be seen, pours into the blood-vessels ; but some of them also appear to originate in the spleen. According to the observations of T. W. Jones, their nuclei finally become red blood corpuscles. The liquor sang'uinis, 2 or blood liquor, is a pale, amber-colored liquid which holds the blood corpuscles in suspension. It is remarkable for its tendency to coagulate or assume the solid condition upon removal from the circulating current, which change depends on its holding fibrin in solution. It is highly important as being the nutritive liquid which is imbibed from the capillaries by all the tissues of the body. When blood is removed from the circulation it ordinarily coagulates or solidifies in a few moments. The coag'ulum or clot 3 then slowly con- tracts, and expresses from the mass a clear amber-colored liquid, called the serum, in which the remainder of the clot floats. The se'rum 4 is the liquor sanguinis deprived of its fibrin, which in 1 White globules ; leucocytes ; lymph 3 Crassamentum ; c r u o r ; insula ; corpuscles. thrombus; placenta sanguinis, or cru- 2 Plasma ; coagulable lymph ; plastic oris ; hepar sanguinis. lymph ; hsematoplasma ; mucago ; mu- 4 Ichor sanguinis ; haemydor. cilage ; intercellular fluid. THE VASCULAR SYSTEM. 341 coagulation entangles the blood corpuscles and thus forms the clot. The relation of the different constituents of liquid and coagulated blood may be understood by reference to the following plan : {Corpuscles \ pint ) Liquor sanguinis... { _;;;;;;;; ' j Coagulated blood. The coagulated fibrin of the blood, examined with the microscope, ex- hibits a fibrillated appearance, thus apparently indicating that the ready coagulation of this material is a step toward organization, or the pro- duction of definite form in a living body. The blood of the hepatic veins, and that which escapes from the torn vessels of the uterine mucous membrane during the menstrual period, ordinarily does not coagulate, thus indicating the absence of fibrin. The composition of the blood varies in the quantity of its chemical ingredients not only in different sexes, ages, individuals, and conditions of health, but also in different parts of the body. A thousand parts of blood by evaporation are found to contain on an average about 790 parts of water and 210 parts of solid materials. The same quantity of blood consists of about 513 parts of blood cor- puscles and 41*7 parts of liquor sanguinis. The chemical constituents of these, according to recent analyses, appear to be as follows : 513 parts of blood corpuscles contain : f Water 350 Globulin with Iron 151 Haematin with Iron 8 Chloride of potassium ; phosphates of potasssa, soda, lime, and magnesia ; soda, and sul- phate of potassa 4 f Water 440 Albumen 40 487 parts of liquor sanguinis J Fibrin , 3 contain : I Chloride of sodium and potassium ; phosphates of soda, lime, and magnesia ; soda, and sul- phate of potassa 4 THE HEART. The Heart, 1 the great central power of the circulation of the blood, is situated within the cavity of the thorax, inclosed by a fibro-serous sac, the pericardium. It lies between the lungs, resting upon the dia- phragm, and encroaches more on the left than on the right side. Its shape is conical, and its position oblique. It is everywhere free or un- 1 Cor ; cardia. 342 THE VASCULAR SYSTEM. attached except at the base, by which it is suspended, through means of the blood-vessels emanating therefrom, to the front of the vertebral column. FIG. 245 FIG. 246. Fig. 245. FRONT VIEW OF THE HEART, a, base of the ventricles; b, apex; c, auricular appendage of the right auricle; d, superior cava; e, longitudinal groove separating the ventricles; /, aorta; k, pulmonary artery; I, right ventricle ; m, right auricle ; n, left auricle; o, its auricular appendage; the second letter o below indicates the left ventricle. Fig. 246. POSTERIOR OR LOWER SURFACE OF THE HEART, b, apex of the heart ; c, the four pulmonary veins ; d, left auricular appendage ; e. termination of coronary vein into the right auricle ; /, aorta ; k, right and left pulmonary arteries ; I, right ventricle ; m, right auricle ; n, left auricle; o, left ventricle ; r, orifice of the inferior cava. The base of the heart is directed upward, backward, and to the right, and reaches from about the fourth to the eighth dorsal vertebra. The apex or point 1 is directed downward, forward, and to the left, and is opposite the sixth costal cartilage. The anterior surface is convex, and directed upward and forward ; the posterior surface is flattened, and in contact with the diaphragm. Of the two sides or borders the left one' 2 is the more obtuse, and is directed obliquely upward ; the right one 3 is the longer, and is directed obliquely downward. The heart is a hollow muscular organ with a membranous investment and lining. It is brown in color, marked with white membranous streaks or patches, often rendered yellow from the presence of adipose tissue. Its average weight is about ten ounces ; its length about five inches, and its breadth about three and a half inches. Its surface exhibits a longi- tudinal and a transverse groove 4 which indicate a division of the organ into four parts, named auricles and ventricles. 1 Mucro. 2 Margo obtusus. 3 Margo acutus. 4 Sulcus longitudinalis, and circularis, or coronalis. THE VASCULAR SYSTEM. 343 The Au'ricles 1 are thin-walled cavities forming the basal portion of the heart, and are so called from their fore part being prolonged into an auricular or ear-like appendage. They are separated by a partition, 2 and are connected with the great venous trunks the cavae and pulmo- nary veins, through which they receive the blood from all parts of the body. They communicate with the ventricles, each by a large aperture, the auric'ulo-ventric'ular orifice, 3 which is furnished with a remarkable mechanism of valves, allowing the transmission of the blood from the auricles into the ventricles, but preventing it in a reverse course. The Ventricles 4 are thick-walled cavities, forming the more massive portion of the heart toward the apex. They are separated by a parti- tion, 5 and are connected with the great arterial trunks the pulmonary artery and aorta by which they send the blood to all parts of the body. Another remarkable arrangement of valves at the mouths 6 of the vessels just named prevents the reflux of the blood into the ventricles. The Right Au'ricle 7 consists of an oblong portion, the si'nus, 8 with a triangular, somewhat indented auric'ular appendage, 9 which projects forward to the outer side of the origin of the aorta. Its walls are thin and translucent, but are more thickened at the fore and outer part, and in the auricular appendage, by means of isolated fleshy fasciculi named pectinate muscles. 10 When these are present, the interior surface of the auricle is rendered uneven by their prominence, but elsewhere it is smooth. Into the back part of the right auricle the superior and inferior cavae open with a direction forward, and thus produce between them an obtuse angle, 11 which is slightly prominent on the interior of the auricle/ The orifices of the two veins are unprotected by valves, but from the direc- tion of the two vessels their currents of blood are not opposed, but cross each other as they enter the auricle. On the interior surface of the right auricle, corresponding with the partition separating it from the left auricle, there exists a shallow oval fossa 12 or depression, surrounded by a prominent border. 13 The fossa 1 Atria ; sinus ; cor venosum ; cor 8 Sinus dexter cordis ; sinus, or saccus membranosum ; cavitates innominatse. venarum cavarum ; sinus venosus. 2 Septum atriorum. Auricula cordis dextra. SQstium atrio-ventriculare ; o. ven- 10 Musculi pectinati; trabeculae car- triculi venosum ; ostium venosum. nese. 4 Ventriculi ; cor arteriosum ; cor mus- n Tuberculum Loweri. culosum ; specus cordis. 12 Fossa, or fovea ovalis. 5 Septum ventriculorum. 13 Annulus ovalis ; limbus foraminis 6 Ostia arteriosa. ovalis ; isthmus Vieussenii. * Atrium dextrum; a. anterius ; a. ve- narum cavarum. 344 THE VASCULAR SYSTEM. indicates the position during foetal life of an orifice, named the oval fora- men, 1 by which the two auricles communicate. The thin, translucent bottom of the fossa, in the foetus, forms a valve 2 which prevents a reflux of blood through the oval foramen. Not unfrequently the up- per part of the fossa is found to have an oblique slit remaining as part of the free communication of the auricles in foetal life. Anterior to birth, a crescentic, membranous fold, named the Eusta'- chian valve, 3 extends from the right of the orifice of the inferior cava, along its anterior border to the oval foramen, and serves to direct the current of blood from that vessel through the foramen. In the adult, the remains of this valve, usually more or less perforated in a reticular manner, are still observable. Between the left extremity of the Eustachian valve and the auriculo- ventricular orifice is situated the aperture 4 , of the coronary vein, pro- tected by a crescentic valve. 5 A number of apertures 6 of small veins are also to be detected at various points of the interior surface of the right auricle. The right auric'ulo-ventric'ular orifice 7 is placed in advance and to the left of that of the inferior cava. It is oval, about an inch in diameter, and has a smooth, slightly prominent border, 8 giving attachment to the tricuspid valve. The Left Auricle 9 has a cuboidal sinus 10 and an elongated, indented auricular appendage, projecting forward to the left of the origin of the pulmonary artery. Its walls are thicker, and not so translucent as in the right auricle. The interior surface is smooth, except within the auricular appendage, 11 which is provided with pectinate muscles. At the back part of the left auricle the four pulmonary veins open, two on each side ; and their orifices are unprotected by valves. At the lower fore part of the cavity is situated the left auriculo-ventricular orifice, 12 which is constructed like that in the right side of the heart. The Eight Ven'tricle 13 is pyramidal, with its base upward and back- 1 Foramen ovale; f. Botale; f. of Bo- cordis venosus; circulus callosus Hal- tal. leri. 2 Valvula foraminis ovalis. 9 Atrium sinistrum. 3 Valvula Eustachii ; valvula forami- 10 Sinus sinister cordis ; s. pulmonalis; nis ovalis anterior. s., or saccus venarum pulmonalium ; s. 4 Orificium venae magnae coronariae. arteriosus ; atrium cordis sinistrum. 5 Valvula Thebesii. n Auricula cordis sinistra. 6 Foramina Thebesii. 12 Ostium venosum sinistrum. 7 Ostium atrio-ventriculare dextrum ; 13 Ventriculus dexter ; v. anterior ; v. ostium venosum dextrum. pulmonalis ; v. primus ; cor venosum ; 8 Annulus fibro-cartilagineus ; tendo cor pulmonale. THE VASCULAR SYSTEM. 345 FIG. 247. ward, and joined to the corresponding auricle; its apex is downward and forward, and does not quite reach the point of the heart. It occupies more of the front surface of the heart than the left ventricle ; and its walls, much thinner than in the latter, are about the fourth of an inch in thickness. The left wall, which forms the partition 1 between the ventricles, bulges into its cavity, so that this ap- pears crescentic in a trans- verse section. The interior surface of the right ventricle is ren- dered exceedingly uneven by numerous projecting, rounded, fleshy fasciculi, named the carneous col- umns. 2 These are of va- rious sizes, and pursue VIEW OF THE HEART, WITH THE ANTERIOR PORTIONS OF THE VEN- TRICLES REMOVED. 1, interior of the right ventricle, exhibiting its carneous columns ; 2, left ventricle ; 3, right auricle ; 4, left auricle; 5, aorta ; 6, 7, the two divisions of the mitral valve ; 8, posterior part of the ventricle ; 9, papillary muscles attached by tendinous cords to the mitral valve ; 10, tricuspid valve ; 11, pulmonary ar- tery laid open ; 12, one'of the semilunar valves ; the other two are seen in section on each side of the former ; 13, sinus or dilatation of the artery behind one of the semilunar valves. different directions springing from one part of the walls, sinking into another, and producing an intricate interlace- ment. Some of them, larger than the others, and named from their shape pap'illary muscles, 3 project from the ven- tricular wall and end in narrow tendinous cords, which are inserted into the free borders of the tricuspid valve. The right auric'ulo-ventric'ular orifice 4 opens into the ventricle at the lower back part of its base. From its boundary projects a broad membranous fold, irregularly divided into three parts, and named, from this circumstance, the tricus'pid valve. 5 The free borders and 1 Septum ventriculorum. 2 Columnse carneae ; trabeculae carneae; columnse, trabeculae, trabes, funes, fasci- culi teretes, lacerti, or lacertuli cordis. 3 Musculi papillares. 4 Ostium atrio-ventriculare dextrum. 5 Valvula tricuspidalis ; valvulae tri- cuspides ; v. trisulcae ; v. trigloclrines. 346 THE VASCULAR SYSTEM. contiguous under surface of the valve are attached by numerous tendin- ous cords, 1 as above indicated, to the papillary muscles, and also to inter- vening points of the interior surface of the ventricle. When the valve is open, the divisions project into the cavity of the ventricle in contact with its sides. In structure, both the tricuspid valve and tendinous cords consist of doublings of the lining membrane of the heart, strengthened by included fibrous tissue. From the anterior angle of the base of the right ventricle, the pul- monary artery has its origin. The orifice 2 of this vessel is provided with three semilunar valves, and the interior surface of the ventricle con- ducting to it is smooth, so that no impediment is presented to the cur- rent of blood in its passage to the artery. The semilunar valves 3 of the pulmonary artery, as expressed in the name, are three crescentic membranous doublings arranged in a circle. Their convex border is attached around the boundary of the orifice of the artery, and their free border is directed into the latter. Behind each valve the artery is dilated into a shallow pouch or sinus, 4 which prevents the valve, when open, from adhering to the side of the artery, and allows the blood in its reflux to get behind the valve and press it down, so as to meet the others and thus close the orifice. The semilunar valves are doublings of the vascular lining membrane, strengthened by included fibrous tissue. The latter forms a nodule 5 at the middle of the free border of the valves, which serves as a common central point of contact when they are closed. Between the nodule and the ends of each valve, just within the position of the free border, there exists a pair of thin lunated spaces, 6 arising from a deficiency of the fibrous basis of the valve. When the valves are shut, these spaces are applied by their opposed surfaces to one another, and completely prevent the entrance of blood into the ventricle ; while the force of the reflux is sustained by the stronger portions of the valves. The Left Ven'tricle 7 is conical, with its base connected to the corre- sponding auricle, and its apex forming the point of the heart. It is longer, and contributes more to the posterior surface of the heart than 1 Chordae tendineae. Arantii, or Morgagni; corpusculum 2 Ostium arteriosum dextrum. sesamoideum. 3 Valvulae semilunares ; v. sigmoidese ; 6 Lunulae. processus sigmoides. 7 Ventriculus sinister ; v. aorticus ; v. 4 Sinus of Valsalva ; sinus pulmonalis. posterior ; v. secundus ; cor arteriosum; 5 Corpusculus, globulus, or nodulus c. aorticum. THE VASCULAR SYSTEM. 347 the right ventricle. Its walls are three times as thick as those of the latter, and its transverse section is circular. Its interior surface is fur- nished with more numerous and stronger carneous columns, which further have a more complex arrangement ; and its two or three pap'- illary muscles are also more robust. The left auric'ulo-ventric'ular orifice, 1 placed at the back part of the right ventricle, is provided with a pair of membranous folds, constituting the mi'tral valve. 2 This has the same mechanism and purposes as the tricuspid valve, but is stronger. In advance and to the right of the orifice just indicated, is the origin of the aorta, which is provided with semilunar valves, identical in character with those of the pulmonary artery, and differ only in being stronger. STRUCTURE OF THE HEART. As previously mentioned, the heart is muscular, with an exterior in- vestment of serous membrane derived from the pericardium, and with its cavities lined by the endocar'dium. This is a thin, translucent membrane, continuous with that of the blood-vessels. Doublings of the endocardium, thickened with intervening fibrous tis- sue, constitute the various valves of the interior of the heart and the vascular orifices communicating therewith. In structure the endocar- dium consists of an epithelium and a fibro-elastic layer. The epithe- lium is composed of a layer of elongated, flattened, polygonal, pave- ment-like cells. The fibro-elastic layer adheres closely to the muscular structure beneath, and appears to be defined next the epithelium by an exceedingly delicate basement membrane. At the auriculo-ventricular orifices, and those of the pulmonary artery and aorta, the fibro-elastic tissue forms a slightly prominent ring, 3 which gives attachment to the valves, and affords a point 4 of departure for 'most of the muscular fibres of the heart. The muscular structure of the heart is composed of transversely striated fibres, which exhibit the peculiarity of anastomosing, or of being connected by means of numerous short oblique offsets, as rep- resented in figure 248. The muscular fibres are much smaller than those of the voluntary muscles, and are not collected into bundles as in 1 Ostium atrio-ventriculare sinistrum ; s Tendo cordis venosus et coronarius ; ostiurn venosum sinistrum. annulus fibro-cartilagineus ; circulus cal- 2 Valvula mitralis ; v. bicuspidalis ; losus Halleri. valvuloe initrales; v. bicuspidatae ; v. 4 Punctum fixum. episcopales. 348 THE VASCULAR SYSTEM. the latter, but are closely approximated with comparatively little inter- vening connective tissue. The arrangement of the muscular fibres of the heart is exceedingly complex. In the auricles a thin layer of transverse muscular fibres encircles both together. Beneath this layer is another, thicker in the left than the right auricle, consist- ing of loop-like fibres crossing the direction of the former, and at- STRIATED MUSCULAR TISSUE OF THE HEART, highly tached by their ends to the fibrous rings of the auriculo-ventricular orifices. Other muscular fibres are arranged in circles around the origin of the great veins and the auricular appendages. In the ventricles, some of the muscular fibres are common to both, while others belong exclusively to each the left one possessing many more than the right one. Most of the muscular fibres may be traced from the fibrous rings of the auriculo-ventricular orifices, and those of the pul- monary artery and aorta. Those seen on the fore part of the heart pursue a course downward, from right to left ; while those on the back of the heart take a more longitudinal course in the opposite direction. At the apex of the heart they penetrate in a whorl to the interior of the ventricles, where they terminate in the carneous columns, some of them forming the papillary muscles, and others ascending to the point from which they started, thus describing in their course a twisted loop like the Greek letter . The arteries supplying the structure of the heart are the right and left coronary. The course of their trunks will be given hereafter. Their branches are numerous, and the capillaries in which they termi- nate generally pursue a course parallel to the direction of the mus- cular fibres, as in other muscular structures. Most of the returning blood is emptied directly into the right auricle by the great coronary vein, and the remainder is returned to the same cavity by a number of minute veins. The lymphatics are numerous, the principal ones following the direc- tion of the coronary veins along the grooves of the heart. Those of the right and front of the heart for the most part join the anterior mam- mary lymphatic glands ; those of the left and back of the heart join the bronchial glands. The nerves of the heart are numerous but small, and are derived from the cardiac plexuses of the pneumo-gastric, spinal, and great sympa- thetic nerves. THE VASCULAR SYSTEM. 349 THE PERICARDIUM. The Pericar'dium 1 is the fibro-serous sac inclosing the heart, and is attached by connective tissue to the pleura of each side, and the tendin- ous centre of the diaphragm below. It has the form of the heart, a bluish-white color, and consists of two layers. The exterior fibrous layer 2 is a strong inextensible membrane com- posed of interlacing bundles of fibrous tissue, generally pursuing a lon- gitudinal course. It embraces the origin of the great blood-vessels at the base of the heart, and becomes continuous with their external tunic. The internal serous layer 3 of the pericardium has the general ar- rangement and constitution of serous membranes generally. One por- tion closely invests the heart and the commencement of the great blood- vessels at its base, from which it is reflected on the interior of the fibrous layer of the pericardium. The cavity of the pericardium presents smooth, opposed surfaces, bathed with a serous fluid, the pericardial liquor, 4 which facilitates the movements of the heart. MECHANISM OF ACTION OF THE HEART. The heart, by alternate contraction 5 and dilatation, 6 is the motive power in the circulation of the blood, though there are also several other means which facilitate the latter. The motive power of the heart resides in its muscular walls, which, in the different cavities, correspond in strength with the distance to which the blood is to be sent. Thus, as the auricles transmit the blood only into the adjacent cavities, they possess thin walls, while those of the right ventricle, which sends the blood to the lungs, are thick and those of the left ventricle are thickest, because this por- tion of the heart transmits the blood to the remotest parts of the body. The pectinate muscles and carneous columns are accessory powers to the general walls, but are always so situated as not to interfere by their 1 Pericardion; capsule, or sac of the * Liquor pericardii; aqua, humor, heart ; peribole ; membrana cor circum- lympha, or urina pericardii ; hydrocar- flexa ; involucrum, area, arcula, capsa, dia. capsula, camera, indumentum, pannicu- 5 Systole ; systalsis, contractio, con- lus, membrana, theca, saccus, sacculus, strictio, augustatio, submissio, or mica- scrotum, vagina, vesica, thalamus rega- tio cordis. lis, bursa, or amphiesma cordis. Diastole ; relaxatio, or remissio cor- 2 Fibrous pericardium. dis ; motus cordis diastalticus. 3 Serous pericardium. 350 THE VASCULAR SYSTEM. projection with the course of the currents of blood passing through the heart. Thus the spaces between the two cavaa and the four pulmonary veins are smooth, as are, likewise, the approaches to the auriculo-ventricular orifices, the pulmonary artery, and aorta. The uniform direction of the circulation of the blood is maintained by the admirable mechanism of valves situated in the heart, at the origin of the great arterial trunks, and in the veins. The auricles dilate and receive the blood simultaneously 1 the right one through the two cavae and the coronary vein, the left one through the four pulmonary veins. The auricles then contract together, and transmit the blood through the auriculo-ventricular orifices into the ven- tricles. These becoming distended now contract 2 the right one sending dark blood through the pulmonary artery to the lungs, the left one sending bright red blood through the aorta to the body generally. In the contraction of the ventricles the auriculo-ventricular orifices are closed by the tricuspid and mitral valves, which are pressed with their edges together by the reflux of blood, and are kept stretched by the tendinous cords, just as the sail of a boat is kept stretched against the wind by the sheet line. While the ventricles contract the auricles are refilling. 3 The blood forced by the ventricles into the pulmonary artery and aorta pushes onward the column of blood which already fills these vessels, and likewise causes their expansion. The arteries subsequently react or contract upon their contents, and thus continue the onward impulse of the current of blood, while its re- flux closes the semilunar valves and prevents regurgitation into the ven- tricles. This alternate expansion and contraction of the arteries con- stitutes their pulsation, or the pulse. The number of dilatations and contractions of the auricles and ventricles corresponds with the pulsations of the arteries in the healthy adult amounting to from sixty to eighty in the minute. The action of the heart gives rise to an impulse which may be felt on the left side of the thorax below the nipple, opposite the interspace of the fifth and sixth costal cartilages. In the circulation of the blood from the heart to the lungs and body generally, and then back again, it performs two circles. The smaller of these, named the lesser or pulmonary circulation, is from the right ven- tricle through the pulmonary artery to the lungs, and back again by the pulmonary veins to the left auricle. The larger circle, named the greater 1 Synchronous action of the auricles. 3 Isochronous action of the ventricles 2 Synchronous action of the ventricles. and auricles. THE VASCULAR SYSTEM. 351 or systemic circulation, is from the left ventricle through the aorta to all parts of the body, and thence back by the two cavae to the right auricle. Following the course of the blood in succession, and starting from the right auricle, this receives the dark blood of the body through the supe- rior and inferior cava. Contracting, the right auricle sends the blood into the corresponding ventricle, which in turn sends it through the pul- monary artery to the lungs. Here acquiring a bright-red hue, the blood returns through the four pulmonary veins to the left auricle, which then transmits it to the left ventricle, to be propelled through the aorta to all parts of the body, from whence it regains the heart by the two cavae. THE ARTERIES. The Ar'teries consist of two great trunks and their branches. One of these trunks is the aorta, by whose branches blood is conveyed to all parts of the body for the nutrition of the organs ; the other is the pul- monary artery, which distributes the blood through the lungs to be aerated. THE AORTA. The Aor'ta 1 is the main trunk of the arterial system supplying blood to the body. It springs from the left ventricle of the heart, ascends and arches obliquely from the right to the left of the vertebral column, upon which it then descends to the fourth lumbar vertebra, and there divides into the common iliac arteries. The first portion of its course is named the arch of the aorta ; and the descending portion 2 is named, from the cavities through which it passes, the thoracic and abdominal aorta. THE ARCH OF THE AORTA. The Arch of the Aorta 3 ascends from the heart with a slight incli- nation toward the right side, curves obliquely backward to the left side over the right pulmonary artery and left bronchus, and descends to the left side of the third dorsal vertebra, where it becomes the thoracic aorta. Its commencement is concealed by the root of the pulmonary artery and right auricular appendage, and when exposed is observed to present a bulbous appearance, 4 due to the dilatations 5 behind the semilunar valves. 1 Arteria magna ; a. maxima ; a. eras- 4 Bulbus aortae. sa ; haemal axis. 5 Sinuses of Valsalva ; lesser sinuses 2 Aorta descendens. of Valsalva. 3 Arcus aortse. 352 THE VASCULAR SYSTEM. FIG. 249. The ascending portion 1 of the arch is in relation behind with the right pulmonary artery and veins, to the right with the superior cava, and to monary artery. The transverse portion of the arch rests in the bi- furcation of the pulmonary artery ; is in relation above with the left innominate vein, behind with the division of the trachea, and in front with the upper part of the sternum. The descending portion of the arch is in relation with the oesophagus and thoracic duct to the right, and with the root of the left lung to the left and in front. Frequently the right portion of the aortic arch exhibits a conspicu- ous dilatation, 2 resembling an in- cipient aneurism,; but which is a natural condition, though not a constant one. From the summit of the arch of the aorta spring forth the large vessels which supply the head and upper extremities, and much reduce the diameter of the descending por- tion of the arch. The branches given in succession from the arch of the aorta are as follow : The right coronary artery. The left coronary artery. The innominate artery. The right common carotid artery. The right subclavian artery. The left common carotid artery. The left subclavian artery. The coronary arteries arise from the aorta, just above the position of the semilunar valves, and supply the walls of the heart. The other THE AORTA. 1, arch of the aorta; 2, thoracic aorta; 3, abdominal aorta; 4, innominate artery; 5, right common carotid ; 6, right subclavian ; 7, left common carotid ; 8, left subclavian ; 9, bron- chial artery, a small branch of the aorta ; 10, reso- phageal arteries; 11, intercostal arteries of the right side ; 12, of the left side; 13, phrenic arteries; 14, coaliac axis; 15, coronary artery; 16, splenic artery ; 17, hepatic artery; 18, superior mesenteric artery ; 19, supra-renal arteries ; 20, spermatic ar- teries ; 21, inferior mesenteric artery ; 22, lumbar arteries ; 23, common iliac arteries ; 24, middle sa- cral artery, a, aortic orifice of the diaphragm ; 6, articulation of the head of the ribs ; c, anterior scalene muscle. 1 Aorta ascendens. 2 Sinus of Valsalva ; greater sinus of Valsalva. THE VASCULAR SYSTEM. 353 three branches spring from the summit of the arch in close succession, and are the large vessels which supply the head and upper extremities. I THE CORONARY ARTERIES. m The Right Cor'onary artery 1 arises from the aorta just above its right semilunar valve, and winds along the groove between the right auricle and ventricle, until it reaches the posterior median groove of the ventri- cles, along which it proceeds to the apex of the heart, and anastomoses with the left coronary artery. It supplies the right side of the heart and the posterior portion of the left ventricle. The Left Cor'onary artery 2 arises from the left side of the aorta and passes forward between the pulmonary artery and the left auricular ap- pendage, and divides into two branches. One of these descends the anterior median groove of the ventricles to the apex of the heart, where it anastomoses with the right coronary artery. The other branch winds along the groove between the left auricle and ventricle to the back of the heart, where it anastomoses with the right coronary artery. THE INNOMINATE ARTERY. The Innom/inate artery 3 is the first of the three large vessels spring- ing from the summit of the arch of the aorta, and corresponds with the other two in supplying branches to one-half of the head and neck, and one upper extremity. It is about an inch and a half in length ; ascends obliquely toward the right side, in front of the trachea and behind the left innominate vein, and divides into the right subclavian and right common carotid arteries opposite the right sterno-clavicular articula- tion. As an occasional variation, the innominate artery gives off the left common carotid artery ; more frequently it is represented by its ordinary divisions springing directly from the aorta, as in the case of the corre- sponding arteries of the left side. 1 Arteria coronaria dextra. 2 A. coronaria sinistra. 3 A. innominata; a. annonyma; a. brachio-cephalica; truncus brachio-cephalicus ; right subclavian artery. 354 THE VASCULAR SYSTEM. THE COMMON CAROTID ARTERY. The Right Common Carot'id artery 1 is one of the divisions of the innominate artery, and ascends the neck to the upper border of the larynx, where it divides into the external and internal carotid arteries. The Left Common Carot'id artery 2 is derived from the arch of the aorta next in succession to the innominate artery. It is longer, deeper, and more vertical in its ascent than the former, and divides in the same position and manner. FIG. 250. LEFT COMMON CAROTID DIVIDING INTO THE EXTERNAL AND INTERNAL CAROTID ARTERIES. 1, common carotid artery; 2, internal carotid; 3, external carotid; 4, superior thyroid; 5, lingual; 6, pharyngeal artery; 7, facial; 8, inferior palatine and tonsillar arteries; 9, submaxillary ; 10, submental ; 11, occipital ; 12, posterior auricular ; 13, parotid branches ; 14, internal maxillary ; 15, temporal artery ; 16, subclavian artery ; 17, axillary; 18, vertebral artery ; 19, thyroid axis; 20, inferior thyroid giving off the ascending cervical; 21, transverse cervical; 2J, supra-scapular; 23, internal mammary artery. The Common Carot'id arteries, 3 in ascending the neck, rest upon the muscles in front of the cervical vertebrae. At their inner side the tra- chea, larynx, and oesophagus are situated; at their outer side is the 1 A. carotis communis dextra; a. c. primitiva dextra. 2 A. c. c. sinistra ; a. c. p. sinistra. 3 Primitive carotid arteries ; a. caro- tides ; a. caroticae ; a. capitales ; a. ce- phalic 93 ; a. jugulares ; a. soporales ; a. somniferse ; a. lethargicse ; a; apoplecti- cse. THE VASCULAR SYSTEM. 355 internal jugular vein, which is inclosed in the same sheath, with the pneumogastric nerve interposed. Behind them is the great sympathetic nerve ; and in front they are crossed by the omo-hyoid muscle, and cov- ered by the sterno-mastoid muscle. They give off no branches until they reach the upper margin of the larynx, where they divide into the external and internal carotid arteries. THE EXTERNAL CAROTID ARTERY. The External Carot'id artery 1 on each side supplies all the parts of the head, with the exception of the brain and the contents of the orbits. Commencing opposite the upper border of the larynx, it ascends nearly vertically to the space between the neck of the lower jaw and the auditory meatus, where it divides into the temporal and internal maxillary arteries. It lies in front and to the inner side of the internal carotid artery, close to the pharynx. In the first part of its course it is covered only by the cervical fascia, subcutaneous cervical muscle, and skin; then is crossed by the stylo-hyoid and digastric muscles and the hypoglossal nerve ; and afterwards passes through the substance of the parotid gland, in which it is crossed by the facial nerve. The branches given off by the external carotid artery are as follow : 1. Superior thyroid artery. 2. Lingual artery. 3. Pharyngeal artery. 4. Facial artery. 5. Occipital artery. 6. Posterior auricular artery. 7. Muscular branches. 8. Parotid branches. 9. Temporal artery. 10. Internal maxillary artery. 1. The Superior Thy'roid artery 2 comes off from the front of the ex- ternal carotid, just above its commencement, and descends obliquely for- ward and inward, to the thyroid body, in which it is mainly distributed ; anastomosing with the other arteries of that organ. In its course it is crossed by the omo-hyoid muscle, and gives off the following named branches : a. Hyoid Branch. b. Muscular branches. c. Laryngeal artery. 1 A. carotis externa ; a. carotis facialis ; a. pericephalica. 2 A. thyroidea superior ; a. laryngea superior ; a. gutteralis superior. 356 THE VASCULAR SYSTEM. a. The Hy'oid branch 1 is a small vessel running along the side of the hyoid bone, and supplying the contiguous parts. It is frequently a branch of the lingual artery. b. The Muscular branches 2 are distributed to the sterno-raastoid muscle and the depressors and elevators of the hyoid bone and larynx. c. The Larynge'al artery 3 pierces the thyro-hyoid membrane, and supplies the small muscles and mucous membrane of the larynx. 2. The Lin'gual artery, 4 larger than the preceding branch of the carotid, comes off next to it, on a line with the side of the hyoid bone. After advancing just above the great horn of the latter, it ascends between the hyo-glossal muscle and the middle constrictor of the pharynx, to the under part of the tongue, along which it proceeds to the tip. Its branches are as follow : a. Dorsal lingual artery. b. Sublingual artery. c. Kanine artery. a. The Dorsal lin'gual artery, 5 frequently represented by several small branches, supplies the root of the tongue. b. The Sublin'gual artery 6 passes between the mylo-hyoid muscle and the sublingual gland, and supplies both with branches. c. The Ran'ine artery 7 is the continuation forward of the lingual, between the hyo-glossal t and genio-glossal muscles, to the tip of the tongue. It has a tortuous course ; and at the side of the iraenum of the tongue is covered only by the mucous membrane. 3. The Pharynge'al artery 8 is a long, narrow vessel, derived from the inner side of the external carotid artery, nearly on a level with the pre- ceding branch. It lies concealed in the ordinary view of the vessels, and ascends deeply in the neck, on the surface of the pharynx, to the base of the skull. In its course it supplies branches to the pharynx, 9 soft palate, and tonsils, the muscles in front of the cervical vertebrse, and the nerves which pass through the jugular foramen. It also gives small branches 10 to the dura mater through the jugular and lacerated foramina. 1 Ramus hyoideus. 7 A. ranina ; a. profunda linguae. * R. musculares. 8 A. pharyngea ; a. pharyngea ascen- 3 R. laryngea; r. 1. superior. dens, or inferior. 4 A. lingualis. 9 Rami pharyngei. 5 A. dorsalis linguae. 10 A. meningeae posteriores 6 A. sublingualis. THE VASCULAR SYSTEM. 357 THE EXTERNAL CAROTID ARTERY AND ITS BRANCHES. 1, right common carotid ; 2, internal carotid ; 3, ex- ternal carotid; 4, superior thyroid; 5, lingual; 6, facial; 7, submental ; 8, inferior coronary; 9, superior coronary; 10, muscular branches ; 11, lateral nasal artery; 12, angular artery; 13, occipital artery ; 14, descending cervical; 15, muscular branch; 16, posterior auricular artery; 17, parotid branches; 18, in- ternal maxillary; 19, temporal; 20, transverse facial; 21, anterior auricular; 22, supra-orbital; 23, middle temporal ; 24, anterior temporal ; 25, posterior temporal artery. 4. The Fa'cial artery 1 comes from the external carotid just above the lingual, and is about the same size as this. It passes upward and forward through the submaxillary gland, curves over the base of the lower jaw in advance of the insertion of the masseter muscle, and ascends upon the face in a tortuous manner to the angle of the mouth, and thence to the inner angle of the eye. Below the jaw it passes beneath the stylo-hyoid and digastric muscles ; at the base of the jaw is only covered by the skin and subcutaneous cervical muscle ; and at the angle of the mouth is beneath the depressor of the oral angle and the zygomatic muscles. Its principal branches are as follow : a. Inferior palatine artery. b. Tonsillar artery. c. Submaxillary branches. d. Submental artery. 1 A. facialis; a. maxillaris externa; a. labialis; a. angularis; a. palato-labialis. 358 THE VASCULAR SYSTEM. e. Inferior coronary artery. /. Superior coronary artery. g. Muscular branches. h. Lateral nasal artery. i. Angular artery. a. The Inferior pal'atine artery 1 ascends at the side of the pharynx, and gives branches to the internal pterygoid muscle, the styloid muscles, the tonsil, Eustachian tube, and muscles and mucous membrane of the soft palate. It is sometimes a branch of the pharyngeal artery. 6. The Ton'sillar artery 2 ascends at the side of the pharynx to the fauces and tonsil. c. The Submax'illary branches 3 are small vessels which supply the submaxillary gland. d. The Submen'tal artery, 4 larger than any of the preceding branches, passes forward between the digastric and mylo-hyoid muscles, and winds over the chin to anastomose with the inferior coronary artery. In its course it supplies the contiguous muscles, the submaxillary gland, and the chin. e. The Inferior cor'onary artery 5 is derived from the facial as it ap- proaches the angle of the mouth. Passing forward and upward, beneath the depressor of the oral angle, it enters the orbicular muscle of the lower lip, and pursues a tortuous course to join its fellow of the opposite side. f. The Superior cor'onary artery 6 comes from the facial at the angle of the mouth, and pursues a tortuous course in the upper lip to join the corresponding vessel of the other side. Besides supplying the lip, it gives a branch to the partition of the nose. 7 g. The Muscular branches 8 are small and variable vessels supplying the depressor of the oral angle, the masseter, buccinator, zygomatic, and other muscles. h. The Lateral na'sal artery, 9 frequently represented by several smaller branches, passes inward, and supplies the side of the nose. i. The Angular artery, 10 the termination of the facial, inosculates with branches of the ophthalmic artery. 1 A. palatina inferior, or ascendens; a. 6 A. coronaria superior; a. labialis su- pharyngo-palatina. perior. 2 A. tonsillaris. " A. septi narium. 3 Kami submaxillares ; r. glandulares. 8 Kami musculares ; r. buccales, mas- 4 A. submentalis. seterici, etc. 5 A. coronaria inferior ; a. labialis in- 9 A. nasalis lateralis, or externa and ra- ferior. mi pinnales and dorsales nasi. 10 A. angularis. THE VASCULAR SYSTEM. 359 5. The Occip'ital artery 1 springs from the back part of the external carotid, about as high as the former branch, and passes backward beneath the muscles attached to the mastoid process of the temporal bone. Pursuing its course between the splenius and complex muscles, at the back of the neck, it pierces the cranial attachment of the trapezius muscle, and ascends beneath the skin of the occipital region, where it divides into many branches, which anastomose with the posterior auric- ular and temporal arteries. In its course it gives off the following branches : a. Muscular branches. &. Descending cervical artery. c. Meningeal branch. a. The Muscular branches 2 go to the sterno-mastoid, digastric, and other muscles. b. The Descending cer'vical artery 3 passes down the back of the neck, and divides into branches which supply the complex, splenius, and other muscles. c. The Menin'geal branch 4 is a small vessel ascending through the jugular foramen to be distributed to the dura mater. 6. The Posterior Auric'ular artery 5 is a small vessel which comes off' from the external carotid a short distance above the former branch. It ascends between the lower part of the parotid gland and the mastoid process to the side of the head behind the ear, where it divides into branches supplying the latter, and anastomosing with the occipital artery. In its course it gives off a small but important branch, as follows NT a. The Sty'lo-mastoid artery, 6 which enters the foramen of that name, and ascends to supply the tympanum and its contents, and the mastoid sinuses. 7. The Muscular branches 7 of the external carotid, irregular in size and disposition, supply the sterno-mastoid, masseter, and pterygoid muscles. 8. The Parot'id branches 8 are small vessels given to the parotid gland in the course of the carotid artery through it. 1 A. occipitalis. * A. meningea ; a. m. posterior externa ; 2 Rami musculares ; r. cervicales ; r. ramus meningeus. sterno-mastoideus, etc. 5 A. auricularis posterior. 3 A. cervicalis descendens; a. cervicalis 6 A. stylo-mastoidea. superior profunda and superficialis ; a. 7 Rami musculares ; ramus sterno-mas- princeps cervicis. toideus, massetericus, etc. 8 R. parotidei. 360 THE VASCULAR SYSTEM. 9. The Tem'poral artery, 1 the apparent continuation of the external carotid, ascends through the parotid gland in front of the ear to the temple, where it is situated between the skin and temporal fascia. A short distance above the zygoma it divides into two branches, which ramify on the side of the head immediately beneath the integument. The branches of the temporal artery, including the terminal ones, are as follow : a. Transverse facial artery. b. Anterior auricular arteries. c. Supra-orbital artery. d. Middle temporal artery. e. Anterior temporal artery. /. Posterior temporal artery. a. The Transverse fa'cial artery 2 aris.es from the temporal, while it is involved in the parotid gland, and passes across the masseter muscle, between the zygoma and parotid duct, to the upper part of the cheek. It supplies the parotid gland, masseter, palpebral orbicular, and other muscles, and anastomoses with branches of the ophthalmic and facial arteries. It is often represented by several smaller branches. b. The Anterior auric'ular arteries 3 are several small vessels dis- tributed to the front of the ear and the auditory meatus. c. The Supra-orVital artery 4 arises above the zygoma and ascends to the supra-orbital margin, where it anastomoses with branches of the ophthalmic and anterior temporal arteries. d. The Middle tem'poral artery 5 perforates the temporal fascia, just above the zygoma, and is distributed to the temporal muscle. e. The Anterior tem'poral artery, 6 one of the terminal branches of the temporal, curves forward and upward upon the temple and forehead, and divides into numerous branches, supplying the scalp and contiguous muscles, and anastomosing with branches of the ophthalmic and posterior temporal arteries. /. The Posterior tem'poral artery, 7 larger than the former, turns upward and backward at the side of the head, and divides into numerous branches, anastomosing with the anterior temporal, posterior auricular, and occipital arteries. 1 A. temporalis; a. crotaphitica. 5 A. temporalis media. a A. transversa faciei. 6 A. temporalis anterior ; a. t. superfi- 3 A. auriculares anteriores ; a. auricu- cialis anterior ; a t. frontalis ; a. t. in- lares anteriores inferiores, and a. auricu- terna. laris anterior superior. 7 A. temporalis posterior; a. t. superfi- 4 A. supra-orbitalis ; a. supra-orbitalis cialis posterior ; a. t. occipitalis ; a. t. ex- externa ; a. zygomatico-orbitalis. terna. , THE VASCULAR SYSTEM. 361 10. The Internal Max'illary artery, 1 the larger division of the exter- nal carotid, passes behind the neck of the jaw, horizontally forward be- tween the pterygoid muscles. If then ascends a short distance, and again turns forward and inward to the upper part of the pterygo-maxil- lary fossa, where it divides into two terminal branches the descending palatine and the spheno-palatine arteries. Including the latter, the internal maxillary gives off the following branches : a. Tympanic artery. b. Great meningeal artery. c. Small meningeal artery. d. Inferior maxillary artery. e. Muscular branches. /. Superior maxillary artery. g. Infra-orbital artery. 7i. Descending palatine artery. i. Spheno-palatine artery. a. The Tym'panic artery, 2 a small vessel given from the internal maxillary near its origin, ascends behind the maxillary articulation and passes through the glenoid fissure to be distributed to the tympanum. b. The Great menin'geal artery 3 comes from the internal maxillary, a short distance from the preceding, and ascends to the spinous foramen of the sphenoid bone, through which it enters the middle cerebral fossa of the cranial cavity. It here curves forward and outward between the dura mater and the temporal bone, and divides into two branches, which ascend and ramify between the membrane just mentioned and the parietal bone. It produces the arborescent channels on the interior surface of the latter, and supplies both the dura mater and the cranial vault. In its course it gives branches to the elevator and tensor muscles of the palate, and to the semilunar ganglion of the trifacial nerve. c. The Small meningeal artery, 4 frequently a branch of the preced- ing, enters the cranium through the oval foramen, and supplies the dura mater of the middle cerebral fossa. d. The Inferior max'illary artery 5 comes from the internal maxillary nearly opposite the meningeals, and descends, in company with the infe- rior dental nerve, to enter the dental canal of the lower jaw. In its 1 A. raaxillaris interna : a. gutturo- a. m. spinosa ; a. spinosa ; a. spheno- maxillaris. spinosa ; a. durae matris media maxima. 2 A. tympanica. 4 A. meningea parva. 3 A. meningea magna ; a. m. media ; 5 A. maxillaris inferior ; a. dentalis, or alveolaris inferior. 362 THE VASCULAR SYSTEM. passage through this canal it gives off the fine dental arteries 1 to the teeth, and finally emerges at the mental foramen to terminate in the chin, 2 where it anastomoses with the submental and inferior coronary arteries. Before entering the dental canal it gives off a branch 3 which runs along the mo- lar ridge and supplies the gum and the mylo-hyoid muscle. e. The Muscular branches, 4 given off be- tween the pterygoid mus- cles, usually consist of two 5 to the latter, two 6 to the temporal muscle, one 7 to the masseter, and one 8 to the buccinator. /. The Superior max'- illary artery 9 is given off from the internal maxil- lary as it escapes from be- tween the pterygoid mus- cles. It descends upon the tuberosity of the max- illary bone, and gives off branches to the gum, and the posterior dental ar- teries which enter small foramina of the bone to supply the maxillary sinus and the molar teeth. g. The Infra-orVital artery 10 arises near the preceding, and enters the infra-orbital canal, along which it runs to the face. In its course through the canal it gives off the anterior dental arteries to the front teeth, and small branches to the inferior straight and oblique muscles of the orbit. INTERNAL MAXILLARY ARTERY. 1, right common carotid ; 2, in- ternal carotid ; 3, external carotid ; 4, superior thyroid ; 5, lin- gual; 6, facial; 7, occipital; 8, posterior auricular; 9, parotid branch; 10, temporal artery; 11, internal maxillary; 12, tym- panic ; 13, the great and small meningeal arteries from a common branch ; 14, inferior dental artery ; 15, muscular branches ; 16, superior maxillary artery giving off the posterior dental arteries ; 17, 18, infra-orbital artery. 1 A. dentales ; rami alveolares. 2 A. mentalis. 3 A. mylohyoidea. 4 Rami musculares. 5 A. pterygoidese. 6 A. temporales profundge ; a. tempo- rails profunda posterior and anterior. 7 A. masseterica. 8 A. buccinatoria ; a. buccalis. 9 A. maxillaris superior ; a. supra- maxillaris ; a. dentalis ; a. alveolaris su- perior. 10 A. infra-orbitalis. THE VASCULAR SYSTEM. On the face it gives branches to the lower eyelid and upper lip, and anastomoses with branches of the facial and ophthalmic arteries. h. The Descending pal'atine artery, 1 one of the terminal branches of the internal maxillary, descends through the posterior palatine canal and is distributed to the soft and hard palate. One 2 of its branches reaches the front of the hard palate, and anastomoses, through the ante- rior palatine foramen, with the arteries of the nose. Another branch, 3 near the origin of the artery, turns back through the pterygoid canal and reaches the top of the pharynx. i. The Spheno-pal/atine artery, 4 the second division of the internal maxillary, passes into the cavity of the nose through the spheno-pala- tine foramen, and, after sending a small branch 5 backward through the pterygo-palatine canal to the upper part of the pharynx, divides into two branches. One 6 of these is distributed to the lateral wall and floor of the nose, and to the maxillary sinus. The other branch 7 descends upon the partition of the nose to which it is distributed, anastomosing, through the anterior palatine foramen, with a branch of the descending palatine artery. THE INTERNAL CAROTID ARTERY. The Internal Carot'id artery, 8 the second division of the common carotid artery, destined to supply the brain and contents of the orbit, ascends in a nearly straight line to the carotid canal of the tem- poral bone. Winding through this canal, it enters the cranial cavity above the lacerated foramen, and proceeds forward along the side of the body of the sphenoid bone to the anterior clinoid process, where it turns upward to the fissure separating the anterior and middle lobes of the brain, and divides into the anterior and middle cerebral arteries. In the neck the internal carotid gives off no branches, and rests against the muscles in front of the cervical vertebra. To its inner side is the pharynx ; in front of it the external carotid artery ; and externally and behind are the internal jugular vein and the last four cerebral nerves. At the side of the body of the sphenoid bone, it is inclosed in the lower wall of the cavernous sinus, and at the anterior clinoid process pierces the dura mater to reach the brain. 1 A. palatina descendens ; a. palatina 5 A. pharyngea suprema, or descen- superior; a. pterygo-palatina. dens. 2 A. palatina anterior. 6 A. nasalis posterior externa, or late- 3 A. Vidiana. ralis. 4 A. spheno-palatina ; a. nasalis pos- * A. septi narium posterior. terior. 8 ^ carotis interna ; a. carotis cere- bralis ; a. cerebralis ; a. encephalica. 364 THE VASCULAR SYSTEM. The branches of the internal carotid artery are as follow : 1. Ophthalmic artery. 2. Posterior communicating artery. 3. Choroid artery. 4. Anterior cerebral artery. 5. Middle cerebral artery. 1. The Ophthal'mic artery 1 springs from the internal carotid, within the position of the anterior clinoid process, immediately after it pierces FIG. 253. ARTERIES OF THE INTERIOR OF THE CRAMUM. 1, internal carotid arteries; 2, ophthalmic artery; 3, pos- terior communicating arteries; 4, anterior cerebral arteries; 5, anterior communicating artery; 6, mid- dle cerebral arteries ; 7, lachrymal ; 8, short ciliary arteries piercing the back part of the eyeball ; 9, cen- tral retinal piercing the optic nerve to reach the interior of the eyeball; 10, muscular artery; 11, frontal and nasal artery; 12, vertebral arteries ; 13, posterior meningeal artery; 14, posterior spinal artery; 15, anterior spinal arteries conjoining in a single one ; 16, inferior cerebellar arteries, 17 basilar artery formed by the union of the vertebrals; 18, internal auditory; 19, superior cerebellar; 20, posterior cerebral arteries. the dura mater, and passes through the optic foramen beneath and to the outer side of the optic nerve. Within the orbit it pursues a tortuous course above the optic nerve and along the inner wall, and di- vides into two terminal branches the frontal and nasal. The branches of the ophthalmic artery, including the latter, are as follow : 1 A. ophthalmica a. orbitalis. THE VASCULAR SYSTEM. 365 a. Lachrymal artery. 6. Central retinal artery. c. Long ciliary arteries. d. Short ciliary arteries. e. Muscular arteries. /. Supra-orbital artery. g. Posterior ethmoidal artery. h. Anterior ethmoidal artery. i. Palpebral arteries. j. Frontal artery. k. Nasal artery. a. The Lach'rymal artery 1 passes along the outer part of the orbit to the lachrymal gland, in which it is mainly distributed. Some of its branches supply several of the contiguous muscles ; others pass through the foramina of the malar bone to anastomose with branches of the facial and internal maxillary arteries ; some pierce the sclerotic tunic as ciliary arteries, and, finally, others 2 pass from the outer canthus of the eye to the eyelids. b. The Central ret'inal artery 3 penetrates the optic nerve, and through it enters the eyeball to ramify in the inner layer of the retina. In the foetus a branch of it passes through the axis of the vitreous humor to reach the capsule of the crystalline lens. c. The Long cil'iary arteries, 4 two in number, pierce the back of the eyeball and run forward, one on each side, between the choroid and scle- rotic coat, to the iris, in which they are distributed. d. The Short cil'iary arteries, 5 three or four in number, pierce the back of the sclerotic coat, and are distributed to the choroid. e. The Muscular arteries 6 are given off to all the muscles of the eye- ball. From these arise the anterior ciliary arteries, 7 which consist of from five to ten minute branches penetrating the front of the sclerotic coat to be distributed to the iris. /. The Supra-orb'ital artery 8 passes along the roof of the orbit, and through the supra-orbital foramen, to the skin and muscles of the eye- brow and forehead. g. The Posterior ethmoid'al artery 9 enters the corresponding fora- men, and is distributed to the posterior ethmoidal sinuses and the dura mater. 1 A. lachrymalis. 5 ^. ciliares posticae breves ; a. uveales. 2 A. palpebralis externa superior and 6 A. musculares. inferior. 7 A. ciliares anteriores. 3 A. centralis retinae ; a. c. Zinnii. 8 A. supra-orbitalis ; a. superciliaris. * A. ciliares posticaj longae ; a. iridis. 9 A. ethmoidalis posterior. 366 THE VASCULAR SYSTEM. h. The Anterior ethmoid'al artery 1 enters the corresponding foramen, and gives off a menin'geal branch 2 to the dura mater, and the anterior nasal artery, 3 which enters the nose, through the most anterior of the foramina of the cribriform plate, to be distributed to the front part of the nose and the anterior ethmoidal and frontal sinuses. 1. The Pal'pebral arteries 4 come from the ophthalmic at the inner canthus, and are distributed one to each eyelid. j. The Front'al artery, 5 one of the terminal branches of the ophthal- mic, passes from the orbit at the inner canthus and ascends upon the forehead beneath the muscles, to which and the skin it is distributed. k. The Na'sal artery, 6 the remaining branch of the ophthalmic, passes from the orbit above the internal palpebral ligament, and descends upon the bridge of the nose, where it anastomoses with the angular artery. 2. The Posterior Communicating "artery 7 is a small branch of the internal carotid proceeding backward at the side of the infundibulum to join the posterior cerebral artery. 3. The Cho'roid artery, 8 the smallest branch of the internal carotid, ascends on the outer side of the cerebral crus, and enters the descending horn of the lateral ventricle to be distributed to the choroid plexus. 4. The Anterior Cer'ebral artery, 9 a terminal branch of the internal carotid, ascends the longitudinal fissure of the cerebrum, across which it is connected with the corresponding artery of the other side, by a trunk not more than a line or two long, called the anterior communicating artery. 10 It then turns over the front of the corpus callosum, and runs backward between this and the cerebral hemisphere, in its course giving off numerous branches, and anastomosing with the posterior cerebral artery. 5. The Middle Cer'ebral artery, 11 the remaining branch of the internal carotid, ascends the fissure separating the anterior and middle cerebral lobes, and divides into branches which supply the latter. 1 A. ethmoidalis anterior. 6 A. nasalis ; a. dorsalis nasi. 2 A. meningea anterior. 7 A. communicans posterior ; a. c. 3 A. nasalis anterior. Willisii. 4 A. palpebrales ; a. palpebralis inter- s A. choroidea. na superior et inferior. These form with 9 A. cerebri anterior ; a. corporis cal- the palpebral branches of the lachrymal losi. artery the arcus tarseus superior and in- 10 A. communicans anterior. ferior. n A. cerebri media; a. c. transversa; a. 5 A. frontalis ; a. supra- orbitalis. fossae Sylvii ; a. Sylviana. THE VASCULAR SYSTEM. 367 THE SUBCLAVIAN ARTERIES. The Right Subcla'vian artery 1 springs from the innominate artery, and curves outwardly to the interval of the anterior and middle scalene muscles, between which it passes over the first rib and assumes the name of axillary artery. It commences opposite the right sterno-clavicular articulation ; and is in relation in front with the union of the internal jugular and subclavian veins, and is crossed in the same position by the pneumogastric nerve. Behind and above it are the brachial plexus and the great sympathetic nerve. The Left Subcla'vian artery 2 is the third vessel arising in succession from the summit of the aortic arch. In consequence of its direct origin from the latter, it is longer than the right subclavian, and is also more deeply situated. It ascends vertically to a distance equal with the length of the innominate artery, and then pursues a similar course to the right subclavian. Its ascending portion is in relation with the left common carotid and the trachea on its right ; and it has the pneumogastric nerve in front. In the rare cases in which the innominate artery is represented by its ordinary divisions, the right subclavian commonly springs from the arch of the aorta after all the other branches, and reaches its usual destina- tion by passing to the right side between the oesophagus and the cervi- cal vertebrae. No branches are given off by the ascending portion of the left subcla- vian artery, but in the subsequent part of its course, as in the case of the right subclavian, the following arise : 1. Vertebral artery. 2. Thyroid axis. 4-3. Inferior thyroid artery. 4. Supra-scapular artery. 5. Transverse cervical artery. 6. Ascending cervical artery. 7. Internal mammary artery. 8. Superior intercostal artery. 1. The Vertebral artery, 3 the largest branch of the subclavian, passes behind the common carotid artery, and enters the foramen in the transverse process of the sixth cervical , vertebra. Ascending through 1 A. subclavia dextra. 2 A. subclavia sinistra. 3 A. vertebralis ; posterior cerebral artery. 368 THE VASCULAR SYSTEM. the foramina of the other transverse processes, it winds backward around the upper articular process of the atlas, perforates the dura mater, and enters the cranium through the occipital foramen. It then proceeds up- ward and forward, turns around the side of the medulla oblongata, and converges to join its fellow at the lower border of the pons, forming by this conjunction the basilar artery. Occasionally the vertebral artery arises directly from the arch of the aorta, especially the left one. The branches of the vertebral artery are as follow : a. Muscular branches. b. Spinal branches. c. Posterior meningeal artery. d. Posterior spinal artery. e. Anterior spinal artery. /. Inferior cerebellar arteries. a. The Muscular branches, 1 derived from the vertebral artery in the neck, are small vessels which supply the muscles attached to the cervical transverse processes, 6. The Spinal branches, 2 also derived from the vertebral artery in the neck, are small vessels which pass through the neighboring intervertebral foramina to supply the spinal cord and its membranes. c. The Posterior menin'geal artery 3 is given off between the atlas and occipital foramen, and passes through the latter to the dura mater of the cerebellar fossa. d. The Posterior spi'nal artery, 4 the first branch of the vertebral within the cranium, descends on the posterior surface of the spinal cord, anastomosing in its course with the spinal branches derived from the vertebral artery in the neck. e. The Inferior cerebellar arteries, 5 usually two in number, wind around the upper part of the medulla oblongata to the under surface of the cerebellum, to which they are distributed. /. The Anterior spi'nal artery, 6 the last branch of the vertebral, unites with its fellow of the opposite side in front of the medulla oblongata, and the common vessel thus formed descends in a tortuous manner in front of the spinal cord, to which it is distributed. The Bas'ilar artery, 7 formed by the union of the two vertebrals, rests 1 Rami musculares. posterior and anterior ; inferior cerebel- 2 Rami spinales. lous arteries. 3 A. meiringea posterior. 6 A. spinalis anterior ; ant. median ar- 4 A. spinalis posterior ; posterior me- tery. dian artery. 7 A. basilaris ; a. cervicalis ; a. meso- 6 A. cerebelli inferiores; a. c. inferior cephalica. THE VASCULAR SYSTEM. 369 in the median furrow of the pons, to which it gives small branches, besides sending off the following in pairs : a. Internal auditory arteries. b. Superior cerebellar arteries. y? c. Posterior uaMfcw44r arteries. a. The Internal aud'itory artery 1 is a small vessel which accompa- nies the auditory nerve in the corresponding meatus, and is distributed, in company with the nerve, to the labyrinth. b. The Superior cerebel/lar artery 2 passes outwardly at the fore part of the pons to the upper surface of the cerebellum, to which it is dis- tributed. c. The Posterior cer'ebral artery 3 results from the division of the basilar artery. Diverging from its fellow of the opposite side, it receives the posterior communicating artery from the internal carotid, and winds around the cerebral crus outward and backward to the under part of the posterior lobe of the cerebrum. In this position it divides into many branches, supplying the latter and anastomosing with the other cerebral arteries. In the early part of its course, the posterior cerebral artery sends a small branch 4 beneath the back part of the corpus callosum to the inter- posed velum of the pia mater and the choroid plexus. The union of the anterior cerebral arteries by the anterior communi- cating artery, and the union of the internal carotids with the posterior cerebrals by the posterior communicating artery, produce together an ar- terial circle at the base of the brain, around the position of the pituitary fossa. This remarkable series of anastomoses, known as the circle of Willis, 5 associates the circulating currents of the internal carotid and vertebral arteries in such a manner that if any one of these vessels becomes obstructed, those remaining are still able to convey blood to all parts of the brain. 2. The Thy'roid axis 6 is a short, thick vessel springing from the fore part of the subclavian artery near the anterior scalene muscle. Imme- diately after its origin it divides into the inferior thyroid, supra-scapular, transverse cervical, and ascending cervical arteries. Occasionally another 1 A. auditiva interna. * A. choroidea posterior. 2 A. cerebelli superior ; superior cere- 5 Circulus arteriosus Willisii ; arterial bellous artery. hexagon. 3 A. cerebri posterior ; a. profunda ce- 6 Truncus thyro-cervicalis ; a. thyroi- rebri ; a. cerebri inferior. dea inferior 24 370 THE VASCULAR SYSTEM. branch comes from the axis ; and any of the branches indicated may arise independently from the subclavian artery. 3. The Inferior Thy'roid artery 1 ascends obliquely behind the com- mon carotid to the lower part of the thyroid body, to which it is distrib- uted, anastomosing freely with the superior thyroid. It likewise gives small branches to the trachea, larynx, and oesophagus. 4. The Supra-scap'ular artery 2 passes outwardly behind the clavicle and between the sterno-mastoid and scalene muscles to the upper border of the scapula, over which it turns to the supra-spinous fossa. In this it lies close to the bone, and is chiefly spent on the supra-spinous muscle. In its course it gives a small branch 3 to the subcutaneous surface of the acromion ; and a larger branch descends behind the neck of the scapula to the infra-spinous muscle. Occasionally the supra-scapular comes directly from the subclavian artery, or from some of its other branches ; and sometimes it arises from the axillary artery. 5. The Transverse Cer'vical artery 4 passes outwardly above and par- allel to the preceding, and crosses the scalene muscles and brachial plexus of nerves beneath the trapezius muscle to the upper angle of the scapula. Occasionally it is a branch directly of the subclavian artery ; and it divides into the following branches : a. Superior cervical artery. b. Posterior scapular artery. a. The Superficial cer'vical artery, 5 often a branch of the ascending cervical, passes upwardly beneath the outer border of the trapezius muscle, and supplies this, the elevator of the scapular angle, the sterno- mastoid muscle, the contiguous lymphatic glands, and the skin. 6. The Posterior scap'ular artery 6 descends along the base of the scapula under the rhomboid muscle, and supplies this, the great serrated, and latissimus muscles, and anastomoses with the supra- and subscapular arteries. 1 A. thyroidea inferior ; ramus thy- 4 A. transversa cervicis, or colli ; a. reoideae thyroideus. cervico-scapularis. 2 A. supra-scapularis ; a. transversa 5 A. superficialis cervicis ; a. cervicalis scapulae ; ramus transversus scapularis. posterior. 3 Ramus acromialis ; r. supra-acromi- 6 A. scapularis posterioris ; a. dorsalis alis. scapulae. THE VASCULAR SYSTEM. 371 6. The Ascending Cer'vical artery, 1 a small vessel derived from the thyroid axis, or the inferior thyroid artery, or less frequently from one of the other branches of the subclavian, passes up the neck in front of the origin of the scalene muscles, to which, and other contiguous muscles, and the lymphatic glands, it is distributed. Y. The Internal Mam'mary artery 2 is given from the subclavian, op- posite the thyroid axis. It descends behind the clavicle and costal car- tilages, a short distance from the sternum, and near the lower end of the latter divides into the musculo-phrenic and superior epigastric arteries. The branches derived from this vessel in its course, together with the terminal ones, are as follow : a. Mediastinal arteries. b. Superior phrenic arteries. c. Perforating arteries. d. Anterior intercostal arteries. e. Musculo-phrenic artery. /. Superior epigastric artery. a. The Medias'tinal arteries 3 are minute branches supplying the parts of the anterior mediastinal space, including the thymus gland, bronchus, pericardium, pleura, sterno-costal muscle, and sternum. b. The Superior phrenic artery* is a thread-like vessel descending in company with the phrenic nerve to the diaphragm. c. The Perforating arteries 5 consist of five or six small vessels per- forating the corresponding upper intercostal spaces near the sternum, to supply the origin of the great pectoral muscle and the contiguous skin. In the female, the intermediate three or four vessels are larger than in the male, and contribute to supply the mammary gland. During lacta- tion they increase in size. d. The Anterior intercostal arteries, 6 usually two in each intercostal space, arise together from the mammary, or separately, or in common with the perforating arteries. Proceeding outwardly in the upper five or six intercostal spaces, they anastomose with the aortic intercostal arteries, and supply the intercostal and pectoral muscles, the mammary gland, and the skin. 1 A. cervicalis ascendens ; a. c. ante- chialis anterior, pericardiacae, et ster- rior : a. dorsalis suprema ; ramus thy- nales. roideae ascendens. * A. phrenica superior ; a. pericardia- 2 A. mammaria interna ; a. sternalis ; co-phrenica. a. substernalis ; a. thoracica interna. 5 A. perforantes et mammarise exter- 3 A. mediastinicee ; a. thymicee, bron- nse ; mammary arteries. 6 A. intercostales anteriores. 372 THE VASCULAR SYSTEM. e. The Mus'culo-phren'ic artery, 1 the outer of the terminal pair of branches of the mammary artery, inclines downward and outward behind the costal cartilages of the lower ribs to the last intercostal space. In its course it gives branches to the lower five intercostal spaces and to the attachments of the diaphragm and abdominal muscles. /. The Superior epigastric artery 2 continues in the direction of the mammary artery to the abdominal parietes back of the straight muscle, to which it is mainly distributed, anastomosing also with the epigastric branch of the external iliac artery, and with others supplying the abdom- inal walls. 8. The Superior Intercos'tal artery 3 arises from the back part of the subclavian, descends in front of the neck of the first rib, and divides into two branches, which supply the first pair of intercostal spaces. 9. The Profound Cer'vical artery, 4 frequently originating in common with the preceding vessel, penetrates beneath the transverse process of the last cervical vertebra to the back of the neck, where it ascends between the transverse and spinous processes to supply the contiguous muscles. THE AXILLARY ARTERY. The Ax'illary artery 5 is the continuation of the subclavian from the outer border of the first rib to the lower margin of the axilla, after which it assumes the name of brachial artery. In its course through the armpit it rests on the great serrated, subscapular, latissimus, and greater terete muscles, and is under cover of the pectoral muscles. In front of it is the axillary vein ; and the brachial plexus at first is behind, and after- wards surrounds it. The most important deviation from the ordinary arrangement of the axillary artery consists in its giving off a large branch, which corresponds with the radial artery of the forearm, or less frequently with the ulnar artery, or rarely with the interosseous artery. In some instances the large branch is the common source of several or all of the smaller ones, commonly derived separately from the axillary and brachial arteries. Besides several small and inconstant twigs 6 to the contiguous muscles 1 A. musculo-phrenica. posterior ; a. trans versalis colli ; a. tra- 2 A. epigastrica superior. chelo-cervicalis. 3 A. intercostalis superior, or supre- 5 A. axillaris. ma ; a. i. subclavia. 6 Muscular branches and axillary tho- 4 A. profunda cervicis ; a. cervicalis racic artery ; a. thoracica axillaris, or alaris ; a. ultima thoracicarum. THE VASCULAR SYSTEM. 373 FIG. 254. and lymphatic glands of the armpit, the axillary artery usually gives off in succession the following branches : 1. Superior thoracic artery. 2. Acromial thoracic artery. 3. Long thoracic artery. 4. Subscapular artery. 5. Anterior circumflex artery. 6. Posterior circumflex artery. 1. The Superior Thorac'ic artery, 1 sometimes substituted by two branches, and frequently arising in common with the succeeding artery, passes between the sub- clavian and small pectoral muscles to supply the lat- ter, the great pectoral muscle, and the mammary gland. 2. The Acro'mial Tho- rac'ic artery 2 ascends to the space above the small pectoral muscle, and di- vides into branches, which supply the pectoral and deltoid muscles, the shoul- der joint, and the subcu- taneous surface of the acromion. In the latter VIEW OF THE AXILLARY ARTERY, portions of the pectoral and del- toid muscles removed. 1, axillary artery ; 2, superior thoracic ; 3, acromial thoracic; 4, long thoracic; 5, subscapular; 6, anterior position it anastomoses circumflex ; 7, posterior circumflex; 8, brachial artery ; 9, superior with branches of the su- profound artery " pra-scapular artery, forming together a fine vascular net. 3 3. The Long Thorac'ic artery 4 descends along the small pectoral muscle, and is distributed to the mammary gland, both pectoral, and the great serrated muscles. 1 A. thoracica superior; a. t. externa superior ; first thoracic artery. 2 A. thoracica acromialis ; a. t. hume- ralis ; a. acromialis ; external scapular, or third thoracic artery. 3 Rete acromiale. 4 A. thoracica longa ; a. t. inferior ; a. t. externa inferior; a. mammaria exter- na ; second thoracic artery. \ 374 THE VASCULAR SYSTEM. 4. The Subscap'ular artery, 1 the largest branch of the axillary, de- scends along the outer border of the scapula, and is distributed to the subscapular, great serrated, greater terete, and latissimus muscles. In its course it gives off a large branch, as. follows : a. The Dorsal scap'ular artery. 2 This passes between the greater terete and subscapular muscles around the outer border of the scapula to the infra-spinous fossa, to the muscle of which it is distributed, and anastomoses with the supra- and posterior scapular arteries. 5. The Anterior Circum'flex artery 3 is a small branch winding for- ward and outward around the humerus below its tuberosities, supplying the shoulder joint and inosculating with the succeeding artery. 6. The Posterior Circum/flex artery, 4 much larger than the preceding, turns backward between the triceps extensor and the humerus to the deltoid muscle, which it supplies, also giving branches to the shoulder joint, and anastomosing with the anterior circumflex, the supra-scapular, and acromial thoracic arteries. THE BEACHIAL ARTERY. The Bra'chial artery, 5 the continuation of the axillary, extends from the outer border of the axilla along the inner side of the arm. It com- mences opposite the tendons of insertion of the latissimus and greater terete muscles, and, about a finger's-breadth below the bend of the elbow joint, divides into the radial and ulnar arteries. In its course it lies on the coraco-brachial, triceps extensor, and brachial muscles. The median nerve is at first on its outer side, and then crosses in front to its inner side. The ulnar nerve is in the latter position, but gradually diverges in approaching the elbow. The brachial artery is accompanied by two companion veins, which lie in close contact with it; and the basilic vein is placed over it. In nearly its whole length it is only covered by the brachial fascia and skin, and in an operation may readily be exposed without cutting the neighboring muscles. In front of the elbow joint it dips between the terete pronator and long supinator, and is covered by the offset from the tendon of the biceps flexor to the fascia of the forearm. 1 A. subscapularis ; a. scapularis infe- 3 A. circumflexa anterior; a. articula- rior; a. s. communis ; a. s. interims ; a. ris anterior. thoracica axillaris, or alaris. 4 A. circumflexa posterior; a. articu- 2 A. dorsalis scapulae ; a. circumflexa laris posterior. scapulae. 5 A. brachialis ; a. humeralis. THE VASCULAR SYSTEM. 375 FIG. 255. As an important variation from the ordinary arrangement of the brachial artery, it may divide into its two principal branches in any posi- tion along the arm. The number of branches of the brachial artery and the order of their succession is variable, but usually they will be found to ac- cord with the following series : 1. Superior profound artery. 2. Inferior profound artery. 3. Medullary artery. 4. Muscular arteries. 5. Anastomotic artery. 6. Radial artery. 7. Ulnar artery. 1. The Superior Profound ar- tery, 1 the largest branch of the brachial except its ultimate divi- sions, accompanies the musculo- spiral nerve between the triceps extensor and the humerus to the outer part of the arm, where it de- scends between the long supinator and brachial muscle to the elbow. In its course it supplies the coraco- brachial, triceps extensor, brachial, and long supinator muscles, and at the elbow anastomoses with the radial, interosseous and ulnar re- current, the inferior profound, and anastomotic arteries. 18 < VIEW OF THE AXILLARY AND BRACHIAL ARTERY. portions of the pectoral and deltoid muscles re- moved. 1, axillary artery ; 2, brachial artery ; 3, superior thoracic artery ; 4, acromial thoracic ; 5, long thoracic ; 6, subscapular ; 7, anterior circum- flex; 8, posterior circumflex; 9, superior profound, the first branch of the brachial artery ; 10, inferior profound ; 11, anastomotic ; 12, radial ; 13, ulnar : 14, interosseous; 15, recurrent radial; 16, recurrent ulnar artery. 2. The Inferior Profound ar- tery, 2 a small vessel from near the middle of the brachial, descends along the inner side of the triceps ex- tensor, in company with the ulnar nerve, to the interval of the internal condyle and olecranon. It supplies the brachial muscle, and anastomoses with the ulnar recurrent and anastomotic arteries. 1 A. profunda superior ; a. p. major humeri ; a. p. brachii ; a. collateralis magna ; a. c. externa ; a. spiralis ; great muscular artery of the arm. 2 A. profunda inferior; a. p. minor : a. collateralis prima; a. c. superior: large communicating ulnar artery ; pro- funda-ulnar artery. 376 THE VASCULAR SYSTEM. 3. The Med'ullary artery, 1 a small vessel from near the middle of the brachial, or from one of its other branches, proceeds through the medul- lary foramen of the humerus to the marrow, which it supplies. 4. The Muscular arteries 2 consist of several small branches to the coraco-brachial, biceps flexor, triceps extensor, and brachial muscles. 5. The Anastomot'ic artery, 3 from the lower part of the brachial, descends to the internal condyle, and there anastomoses with the ulnar recurrent and profound arteries. The anastomotic and profound branches of the brachial artery form, with the recurrent branches of the radial, ulnar, and interosseous arteries, a fine vascular net, 4 which envelops and supplies the elbow joint and the spongy extremities of the bones. THE EADIAL ARTERY. The Ra'dial artery, 5 the smaller of the ultimate divisions of the bra- chial, from its direction appears as if it were a continuation of the latter. It proceeds along the outer side of the front of the forearm, between the long supinator and radio-carpal flexor to the lower end of the radius. It then turns around the outer side of the wrist beneath the extensor tendons of the thumb, to the back of the carpus, where, reaching the interval of the first pair of metacarpal bones, it penetrates to the palm of the hand, and ends in the deep palmar arch. In the early part of its course it rests on the tendon of the biceps flexor and the insertion of the round pronator, and is overlapped by the fleshy part of the long supinator. Subsequently it rests on the long flexor of the thumb, the quadrate pronator, and the radius, and is covered alone by the fascia and skin. Near the wrist, during life, this artery is found very convenient, to determine the condition of the circu- lation as indicated by the pulse. It is accompanied by a pair of com- panion veins, and part of the way by the radial nerve. In those cases in which the radial artery is derived from the brachial above its ordinary source, it passes along the inner side of the latter, and then crosses to its outer side. Reaching the elbow, it usually pierces the brachial fascia, and proceeds between it and the skin down the outer 1 A. nutritia humeri. cus magnus ; a. collateralis interims ; a. ' l Kami musculares. c. ulnaris secunda ; a. c. u. inferior. 3 A. anastomotica ; ramus anastomoti- 4 Rete articulare cubiti. 5 A. radialis ; a. externa cubiti. THE VASCULAR SYSTEM. 377 FIG. 256. side of the forearm ; or, less frequently, from the position of the elbow it pursues the ordinary course. The branches of the radial artery are as follow : 1. Radial recurrent artery. 2. Muscular branches. 3. Anterior carpal artery. 4. Yolar artery. 5. Posterior carpal artery. 6. Metacarpal artery. 7. Principal artery of the thumb. 8. Radial index artery. 9. Deep palmar arch. 1. The Ra'dial Recur/rent artery, 1 derived from near the commencement of the radial, ascends between the long and short supinators to the external condyle. It supplies the con- tiguous parts of the supinator and extensor muscles, and anastomoses with the superior profound artery. 2. The Muscular branches are small vessels given to the neighboring muscles in the course of the radial artery. 3. The Anterior Car'pal artery 2 is a small branch from the lower part of the radial, de- scending to the front of the radio-carpal artic- ulation, where it forms an anastomosis 3 with a similar branch from the ulnar artery, and sup- plies the wrist joint. ARTERIES OF THE FOREARM. 2, brachial artery ; 3, anastomotic ar- tery ; 4, radial artery ; 5, ulnar ar- tery ; 6, recurrent ulnar ; 7, inter- osseous ; 8, anterior carpal ; 9, su- perficial volar; 10, anterior carpal 4. The Volar artery/ very variable in its branch of the uinar ; ii, superficial size and arrangement, is usually a small vessel derived from the radial just before it turns to the back of the carpus. Descending in front of the ball of the thumb, it supplies the small muscles of the latter, and contributes to form the superficial palmar arch. palmar arch ; 12, principal artery of the thumb ; 13, radial index ar- tery; 14, digital arteries; 15, re- current branches. 1 A. recurrens radialis ; recurrent ar- tery of the epicondyle. 2 A. carpea anterior ; a. c. volaris ; a. radio-carpalis ; a. transversa- carpi ante- rior. 3 Anterior carpal arch ; rete carpi volare. 4 A superficialis volse : superficial vo- lar artery ; ramus volaris ; a. radio-pal- maris ; external superficial artery of the palm. 378 THE VASCULAR SYSTEM. 5. The Posterior Car'pal artery 1 is a small branch from the posterior portion of the radial, which crosses the back of the carpus beneath the extensor tendons, to join with a similar branch of the ulnar artery. From this conjunction 2 twigs supply the wrist joint ; and branches 3 pro- ceed to the outer three metacarpal interspaces, each dividing into a pair,* which descend along the contiguous sides of the backs of the fingers. 6. The Metacar'pal artery 5 is a small vessel descending upon the first metacarpal interspace, and dividing into three branches, 6 which pro- ceed along the sides of the thumb and the approximate side of the index finger. 7. The Principal artery of the Thumb 7 is derived from the radial just after it reaches the palm of the hand. It descends along the first metacarpal bone, and divides into two digital arteries, 8 which proceed along the opposite sides of the thumb to its extremity. 8. The Ra'dial Index artery 9 arises close to the preceding and descends along the radial border of the index finger to its extremity. 9. The Deep Pal'mar Arch 10 is formed by the conjunction of the termi- nating portion of the radial with the communicating artery from the ulnar. It lies transversely across the upper part of the metacarpus, beneath the flexor tendons, and gives off the following branches : a. Recurrent branches. b. Perforating branches. c. Interosseous arteries. a. The Recurrent branches 11 ascend and anastomose with the anterior carpal arteries. b. The Perforating branches 12 pass through the upper part of the in- terosseous spaces and join the branches of the posterior carpal arteries. c. The Interos'seous arteries 13 supply the corresponding muscles, and anastomose with the digital branches of the superficial palmar arch. 1 A. carpse posterior ; a. c. dorsalis ; a. 8 A. volaris pollicis radialis and ulna- transversa carpi-dorsalis ; a. dorsalis ris. carpi-radialis. 9 A. radialis indicis ; a. volaris indicis 2 Posterior carpal arch ; rete carpi radialis. dorsale ; r. carpeum posterius. 10 Arcus palmaris profundus ; a. vola- 3 A. interossese dorsales. ris profundus ; profound, or radial pal- 4 A. digitales dorsales. mar arch. 5 A. interossese dorsalis prima. n Kami recurrentes ; r. retrogradi. 6 A. dorsalis pollicis et indicis ; a. dor- 12 Kami interossei perforantes ; r. per- salis pcllicis radialis et ulnaris, et indi- forantes superiores. cis radialis. 13 A. interossese volares. 7 A. princeps pollicis ; a. magna polli- cis ; a. pollicaris. THE VASCULAR SYSTEM. 379 THE ULNAE ARTERY. The TJl'nar artery, 1 the second division of the brachial, turns inwardly beneath the muscles springing from the internal condyle, and descends on the inner side of the forearm between the ulno-carpal and superficial flexor of the fingers to the wrist. Passing over the anterior annular liga- ment at the side of the pisiform bone to the palm of the hand, it termin- ates in the formation of the superficial palmar arch. In the early part of its course it rests on the insertion of the brachial muscle, and afterwards on the deep flexor of the fingers. It is accompanied by two companion veins, and in the greater part of its course by the ulnar nerve. In those anomalous instances in which the ulnar artery comes from the brachial above its ordinary position, as it approaches the elbow it in- clines inwardly, and passes over the heads of the flexor muscles instead of beneath them, and then pursues the usual course down the forearm. The branches given from the ulnar artery are as follow : 1. Ulnar recurrent artery. 2. Common interosseous artery. 3. Muscular branches. 4. Posterior carpal artery. 5. Anterior carpal artery. 6. Communicating artery. 7. Superficial palmar arch. 1. The Ulnar Recurrent artery, 2 frequently substituted by a pair of branches, comes from the ulnar just below the elbow, and ascends beneath the muscles arising from the internal condyle. It supplies the heads of the flexor muscles, and anastomoses with the inferior profound, anasto- motic, and other arteries about the elbow joint. 2. The Common Interos'seous artery 3 comes from the ulnar near the tuberosity of the radius, and shortly afterwards divides into the anterior and posterior interosseous arteries. Occasionally the common interosse- ous artery is a branch of the brachial ; and when the ulnar artery de- rives its origin above the usual position, the common interosseous and radial arteries appear as the terminal divisions of the brachial. a. The Anterior interos'seous artery* descends in front of the inter- 1 A. ulnaris; cubital artery; a. cubi- 3 A. interossea communis ; a interos- talis. sea antibrachii communis ; a. interossea. 2 A. recurrens ulnaris ; a. r. u. ante- 4 A. interossea anterior, or interna. rior and posterior ; a. r epitrochleae ; a. r. cubitalis anterior and posterior. 380 THE VASCULAR SYSTEM. osseous membrane as far as the quadrate pronator, when it pierces the former and passes to the back of the wrist, where it anastomoses witli the posterior carpal arteries. In its course it gives branches to the neighboring muscles. 6. The Posterior interos'seous artery 1 passes to the back of the fore- arm through the opening at the upper part of the interosseous membrane, and descends beneath the common extensor of the fingers to the wrist, supplying in its course the contiguous muscles, and anastomosing with the anterior interosseous and posterior carpal arteries. At its upper part it gives off the Interosseous recurrent artery, 2 which ascends be- neath the short supinator and anconeus muscles to the interval of the olecranon and external condyle, and anastomoses with the superior pro- found and radial recurrent arteries. 3. The Muscular branches of the ulnar artery are small vessels given to the neighboring muscles. 4. The Posterior Car'pal artery, 3 of variable size, comes from the lower part of the ulnar artery and turns beneath the tendon of the ulno- carpal flexor to the back of the wrist. It sends a metacarpal branch to the inner side of the hand and little finger, and terminates by joining the corresponding branch of the radial artery. 5. The Anterior Car'pal artery, 4 smaller than the preceding, passes outwardly to the front of the wrist, where it joins the anterior carpal branch of the radial artery. 6. The Communicating artery 5 is derived from the ulnar just after passing the- pisiform bone, and dips between the short flexor and abduc- tor of the little finger to contribute in the formation of the deep palmar arch. T. The Superficial Palmar arch, 6 the terminating portion of the ulnar artery, curves internally in the palm of the hand, upon the flexor tendons and beneath the palmar fascia, and joins the volar artery of the radial. The branches given from the arch are four digitals. 7 1 A. interossea posterior, or externa; 5 A. communicans ; a. cubitalis manus a. perforans suprema. profunda. 2 A. interossea recurrens ; a. recurrens 6 Arcus palmaris superficialis ; arcus olecranea ; a. r. radialis posterior. volaris sublimis ; a. v. superficialis ; ra- 3 A. carpea posterior; ramus dorsalis. mus volaris superficialis. * A. carpea anterior. 7 A. digitales volares ; a. d. communes. THE VASCULAR SYSTEM. 381 FIG. 257. The first Digital artery runs along the ulnar side of the hand and little finger to its extremity. The remaining Dig'ital arteries descend along the metacarpal inter- spaces, except the first, to the roots of the fingers, where each divides into two branches 1 which run along the contiguous sides of the fingers to their tips. The arteries of the hand exhibit frequent varia- tions in their arrange- ment. In some instances the contribution of the ul- nar artery to the super- ficial arch is much reduced, and that from the radial artery is in a correspond- ing degree increased. In other instances the con- tributions of both are re- duced, even to a want of continuity in the super- ficial arch, and each supplies its own side of the hand ; or the deep arch is larger, and then appears mainly to supply the hand and fingers. ARTERIES OP THE HAND; PALMAR SURFACE. 1, radial artery; 2, ulnar ; 3, communicating branch with the deep palmar arch ; 4, superficial palmar arch; 5, superficial volar artery; 6, digital ar- teries of the thumb; 7, radial index artery; 8, digital artery to the little finger; 9, common digital arteries; 10, digitals to the fingers. THOEACIC AORTA. The Thorac'ic Aor'ta 2 commences with the termination of the arch of the aorta on the left side of the third dorsal vetrebra. Descending on the left of the vertebral column, in the lower part of its course it gradu- ally inclines toward the median line, which 'it nearly reaches opposite the last dorsal vertebra, arid there passes through the aortic orifice of the diaphragm to assume the name of abdominal aorta. It is situated in the posterior mediastinal space behind the pericardium and the root of the left lung. . It is in relation on the right with the oesophagus, azygos vein, and thoracic duct ; on the left with the corresponding pleura and lung. 1 Collateral digital arteries. 2 Aorta thoracicus. 382 THE VASCULAR SYSTEM. J The branches of the thoracic aorta are all of small size, and come off in succession, as follow : 1. Pericardiac arteries. 2. Bronchial arteries. 3. (Esophageal arteries. 4. Mediastinal arteries. 5. Intercostal arteries. 1. The Pericar'diac arteries 1 consist of a few fine vessels rami- fying on the contiguous portion of the pericardium. 2. The Bron'chial arteries, 2 two or three in number, occasionally originating in one trunk, apply themselves to the bronchi and ac- company them in their ramification through the lungs. Sometimes the right bronchial artery is derived from the corresponding third inter- costal artery. 3. The Oesophage'al arteries, 3 four or five in number, supply the oesophagus. 4. The Medias'tinal arteries 4 consist of a number of fine ves- sels distributed on the neighboring pleurae and lymphatic glands. 5. The Intercostal arteries, 5 of which there are ten on each side, including the one below the last rib, come off from the back of the aorta opposite the vertebral bodies. Those of the left side are shorter than the right ones in consequence of the position of the aorta on the left of the median line. They pass THE AORTA. 1, arch of the aorta; 2, thoracic aorta; 3, abdominal aorta; 4, innominate artery : 5, right common carotid ; 6, right subclavian ; 7, left common carotid ; 8, left subclavian ; 9, bron- chial artery, a small branch of the aorta ; 10, ceso- phageal arteries; 11, intercostal arteries of the right side ; 12, of the left side; 13, phrenic arteries ; 14, cceliac axis; 15, coronary artery; 16, splenic artery ; 17, hepatic artery; 18, superior mesenteric artery ; 19, supra-renal arteries ; 20, spermatic ar- teries ; 21, inferior mesenteric artery ; 22, lumbar arteries ; 23, common iliac arteries ; 24, middle sa- cral artery, a, aortic orifice of the diaphragm ; 6, articulation of the head of the ribs ; c, anterior scalene muscle. 1 A. pericardiacae ; a. pericardiacae posteriores. 2 A. bronchiales ; a. b. posteriores. 3 A. cesophageae. 4 A. mediastinicae. 5 A. intercostales ; a. i. inferiores, or aorticae. THE VASCULAR SYSTEM. 383 from their origin upward and outward to the commencement of the inter- costal spaces, and divide into an anterior and a dorsal branch. a. The anterior branch 1 passes outwardly beneath the pleura, enters between the two intercostal muscles, and then runs along the lower bor- der of the uppermost rib. In its course it gives branches to the inter- costal, pectoral, and great serrated muscles ; a moderate-sized one which descends and runs along the border of the rib below ; and others which anastomose with the anterior intercostal branches of the internal mam- mary artery, and the thoracic branches of the axillary artery. The lower three of the anterior branches extend into the abdominal muscles, where they anastomose with the epigastric arteries. In the female, the anterior branches from the third to the sixth give off considerable twigs 2 to supply the mammary gland. b. The dorsal branch 3 of the intercostals, after transmitting a branch 4 through the intervertebral foramina to the contents of the spinal canal, passes backward between the transverse processes of the vertebrae, and is distributed to the muscles of the back. ABDOMINAL AOETA. The Abdom'inal Aor'ta 5 commences in the termination of the thoracic aorta as it emerges through the aortic orifice of the diaphragm opposite the last dorsal vertebra. Descending in front of the vertebral column with a slight inclination to the left side, opposite the fourth lumbar ver- tebra it divides into the two common iliac arteries. In front it is in relation with the liver, splenic vein, pancreas, duodenum, left renal vein and peritoneum ; and to its right is the inferior cava, with the right crus of the diaphragm, commencement of the thoracic duct and azygos vein interposed above. The branches of the abdominal aorta are numerous, and many of them of large size. Four of them are symmetrical and median in their origin ; the others are in pairs. The symmetrical branches are as follow : Coeliac axis. Superior mesenteric artery. Inferior mesenteric artery. Middle sacral artery. The branches in pairs are as follow : 1 Ramus anterior, or intercostalis. 4 R. spinalis ; r. vertebralis. 2 Rami mamraarii extern!. 5 Aorta abdominalis ; abdominal por- 3 R. dorsalis ; r. posterior. tion of the descending aorta. 384 THE VASCULAR SYSTEM. Phrenic arteries. Supra-renal arteries. Renal arteries. Spermatic arteries. Lumbar arteries. THE COELIAC AXIS. The Cce'liac axis 1 is a short, thick trunk, projecting forward from the commencement of the abdominal aorta. It is in relation below with the pancreas, and with the semilunar ganglion on each side. It divides into three diverging branches as follow : 1. Coronary artery. 2. Hepatic artery. 3. Splenic artery. FIG. 259. DISTRIBUTION OF THE CCELIAC ARTERY. 1, liver turned upward, and showing its lower surface ; 2, trans- verse fissure; 3, gall-bladder; 4, stomach; 5, oesophagus; 6, 7, 8, duodenum; 9, pancreas; 10, spleen; 11, aorta; 12, cceliac artery; 13, coronary artery; 14, hepatic artery; 15, pyloric artery; 16, gastro-duodenal artery; 17, right gastro-epiploic artery; 18, pancreatico-duodenal artery; 19, hepatic artery dividing into the right and left branches for the liver; 20, splenic artery; its course indicated behind the stomach by dotted lines; 21, left gastro-epiploic artery; 22, pancreatic branch; 23, gastric branches; 24, superior mesenteric artery, emerging from between the pancreas and duodenum. 1. The Cor'onary artery, 2 the smallest of the divisions of the coeliac axis, turns upward and to the left side toward the cardiac orifice of the 1 A. cceliaca; tripus Halleri; a. epis-togastricus. 2 A. coronaria; a. c. ventriculi; a. c. v. sinistra; a. gastrica major; a. g. sinistra superior; a. stomogastrica. THE VASCULAR SYSTEM. 385 stomach, and then runs along its lesser curvature. Situated between the layers of the lesser oraentum, it divides into numerous branches, which supply the lower part of the oesophagus 1 and both sides of the stomach, 2 and anastomose with all the other arteries of the latter. 2. The Hepat'ic artery, 3 the second in size from the cceliac axis, in- clines upwardly within the right border of the lesser omentum, and divides into two branches which enter the transverse fissure of the liver. Behind it is the portal vein, and to its right the bile duct. Its branches, including the terminal pair, are as follow : a. Pyloric artery. 6. Gastro-duodenal artery. c. Pancreatico-duodenal artery. d. Right gastro-epiploic artery. e. Right branch. /. Cystic artery. g. Left branch. a. The Pylor'ic artery 4 is a small branch which turns downward and runs along the lesser curvature of the stomach from right to left, anasto- mosing with the coronary artery. 6, The Gas'tro-duode'nal artery, 5 a large branch, descends behind the pylorus, and divides into the following two vessels : c. The Pancreat'ico-duode'nal artery 6 passes between the head of the pancreas and the duodenum, and supplies both with branches. 7 d. The Right gas'tro-epip'loic artery 8 runs along the greater curva- ture of the stomach from right to left, and terminates by conjunction with the left gastro-epiploic. It gives many branches 9 to both surfaces of the stomach which anastomose with those from the lesser curvature, and it also sends long thread-like vessels 10 downward to the great omentum. e. The Right branch 11 of the hepatic artery enters the right side of the transverse fissure of the liver, and divides into two or three branches, which penetrate into the right lobe of the liver. /. The Cys'tic artery, 12 a branch of the preceding, turns forward to supply the gall-bladder. 1 Kami oesophagei inferiores. ~ Kami pancreatic! dextri and r. duode- 2 Kami cardiac! and gastric!. nales. 3 A. hepatica. 8 A. gastro-epiploica dextra ; a. coro- 4 A. pylorica ; a. p. superior ; a. coro- naria dextra inferior ; a. c. ventriculi, naria dextra ; a. c. ventriculi ; a. gas- or gastrica dextra inferior. trica dextra superior. 9 R am i ga strici. 5 A. gastro-duodenalis. 10 R am i epiploici. 6 A. pancreatico-duodenalis. 11 A. hepatica dextra. 12 A. cystica. 25 386 THE VASCULAR SYSTEM. g. The Left branch 1 of the hepatic artery, smaller than the other, enters the left of the transverse fissure to be distributed to the corre- sponding lobe of the liver. 3. The Splen'ic artery, 2 the largest branch of the coaliac axis, passes toward the left side in a tortuous manner along the upper border of the pancreas to the hilus of the spleen. Its branches are as follow : a. Pancreatic arteries. 6. Left gastro-epiploic artery. c. Short gastric arteries. d. Splenic branches. a. The Pancreatic arteries, 3 variable in size and number, are given from the splenic in its course along the pancreas. b. The Left gas'tro-epip'loic artery 4 runs from left to right along the greater curvature of the stomach, and terminates by joining the right gastro-epiploic, like which it is also distributed. c. The Short gas'tric arteries, 5 three to six in number, are directed from the termination of the splenic artery, or some of its branches, to the fundus of the stomach, where they anastomose with the other arteries of that organ. d. The Splen'ic branches, 6 five or more in number, diverge from the parent vessel and enter the hilus of the spleen. THE SUPERIOR MESENTERIC ARTERY. The Superior Mes'enteric artery, 7 a large vessel, springs from the front of the aorta just below the coeliac axis, and supplies the small in- testine and the right portion of the large intestine. It descends behind the pancreas and in front of the duodenum, and then proceeds within the mesentery in a curved line, at first downward and to the left, and then toward the right iliac region, where it inosculates with its own ileo- colic branch. The superior mesenteric artery gives off the following branches : 1. Duodenal artery. 2. Jejunal and ileal arteries. 3. Ileo-colic artery. 4. Right colic artery. 5. Middle colic artery. 1 A. hepatica sinistra. 5 A. gastricse breves; vasa brevia. 2 A. splenica ; a. lienalis. 6 Kami splenic! ; r. lienales. H A. pancreaticse. 7 A. mesenterica superior; a. mesara- 4 A. gastro-epiploica sinistra; a. co- ica sup. ronaria sinistra inferior; a. c. ventriculi, or gastrica sinistra inferior. THE VASCULAR SYSTEM. 387 1. The Duode'nal artery 1 turns back along the course of the duode- num, and gives branches 260 both to it and the pan- creas. 2. The Jeju/nal and Il'eal arteries, 2 fifteen or more in number, diverge from the convexity of the parent vessel, and supply almost the whole length of the small intestine. In their course within the mesentery they divide, and the contiguous branches conjoin so as to form a series of arches. From these spring forth a greater number of branch- es, which subdivide, and, in the manner just indi- cated, form a second se- ries of arches, and from these again a third series is formed. Each series of arches becomes succes- sively more numerous and smaller, and from the last series originate a multitude of intestinal branches which diverge upon the sides of the jejunum and ileum, where they freely anastomose with one another. 3. 4, 5. The Il'eo-colic, 3 Right Colic, 4 and Middle Colic arteries 5 arise in succession from the right side or concavity of the superior mes- enteric artery. Each divides into two branches, of which those contigu- ous, together with the termination of the parent vessel and the upper branch of the left colic artery, conjoin so as to form four large arches. Upon these, in the manner indicated in the account of the preceding arteries, a more numerous and smaller row of arches is formed, from DISTRIBUTION OF THE SUPERIOR MESENTERIC ARTERY. 1, superior mesenteric artery; 2, jejunal and ileal arteries; 3, ileo-colic ar- tery; 4, right colic; 5, middle colic artery; 6, duodenal artery, a, small intestine turned to the left ; b, large intestine ; c, pan- creas. 1 A. duodenalis inferior; a. pancrea- tico-duodenalis inferior. 2 A. jejunales et ileae; a. intestinales ; vasa intestini tenuis. 3 A. ileo-colica; a. colica dextra infe- rior ; a. csecalis. 4 A. colica dextra ; a. c. d. media ; a. media anastomotica. 5 A. colica media: a. colica dextra su- perior; a. mesocolica. 388 THE VASCULAR SYSTEM. which emanate many branches to supply the termination of the ilium, the caecum, and the ascending and transverse colon. THE INFERIOR MESENTERIC ARTERY. The Inferior Mes'enteric artery 1 springs from the front of the aorta about two inches below the superior mesenteric, and is destined to sup- FIG. 261. ply ^ e descending colon and the rectum. It de- scends toward the left iliac region and gives off the following branches : 1. Left colic artery. 2. Sigmoid artery. 3. Superior haemorrhoidal artery. 1. The Left Col'ic ar- tery, 2 directed to the left side, divides into two branches, of which one joins the middle colic ar- tery, and the other joins the sigmoid artery, thus contributing to form a pair of arches. Upon these a series of irregular and smaller arches is formed, from which branches proceed to the descending colon. DISTRIBUTION OF THE INFERIOR MESENTERIC ARTERY. 1, aorta ; 2, inferior mesenteric artery ; 3, left colic artery ; 4, sigmoid artery ; 5, superior hsemorrhoidal artery; 6, superior mesenteric artery; 7, middle colic artery anastomosing with the left and the right (8) colic arteries ; 9, branches to the small intestine ; 10, left renal artery, a, small intestine turned to the right side ; b, large intestine ; c, pan- creas. 2. The Sig'moid ar- tery 3 sometimes originat- ing in common with the former, and sometimes represented by two branches, inosculates with the left colic and superior haemorrhoidal arteries, thus producing arches from which branches proceed to the sig- moid flexure of the colon. 3. The Superior haemorrhoidal artery,* the terminal portion of the 1 A. mesenterica, or mesaraica inferior. s A. colica sinistra inferior; a. c. s. 2 A. colica sinistra ; a. c. s. superior ; parva. a. c. sinistra magna and media. * A. hsemorrhoidalis superior, or in- terna. THE VASCULAR SYSTEM. 389 inferior mesenteric, after anastomosing with the former, descends behind the rectum and divides into two branches, distributed on the sides of the latter, and anastomosing with the middle and inferior hemorrhoidal arteries. THE MIDDLE SACRAL ARTERY. The Middle Sac'ral artery 1 is a small vessel descending from behind the bifurcation of the aorta along the middle of the sacrum and coccyx. It is really a rudimental termination of the aorta, and appears as a gradual prolongation of the latter in whales, snakes, and other animals in which hinder extremities do not exist or are feebly developed in com- parison with the tail. In its course it gives off branches which anasto- mose with the lateral sacral arteries. ARTERIES IN PAIRS FROM THE ABDOMINAL AORTA. The Phren'ic arteries 2 are two small vessels arising from the sides of the abdominal aorta near the co3liac axis, or from the latter itself. Di- verging on the crura of the diaphragm, the right one passes behind and to the outer side of the inferior cava, while the left one proceeds in like manner in relation with the O3sophagus, and both divide into branches supplying the diaphragm, anastomosing with the phrenic branches of the internal mammary and the terminations of the intercostals. In their course they give small branches 3 to the supra-renal bodies. The Liim/bar arteries 4 correspond very nearly with the intercostals in their manner of origin, direction, and distribution. There are four pairs of them, and they cross the bodies of the lumbar vertebra beneath the origin of the crura of the diaphragm and the psoas muscles, to the inter- spaces of the transverse processes, where they divide into an anterior and a posterior branch. The anterior branch 5 passes outwardly behind the quadrate lumbar muscle, ramifies in the broad abdominal muscles, and anastomoses with the epigastric arteries. The posterior branch, 6 after giving off a spinal branch, 7 through the intervertebral foramina, to the spinal cord and membranes, is distributed to the muscles and skin of the back. 1 A. sacralis media; a. s. anterior; 4 A. lumbares, a. lumbales. median artery of the sacrum. 5 Ramus lumbaris, or abdominalis. 2 A. phrenicse : a. p. inferiores, or mag- 6 Ramus dorsalis. nse ; a. diaphragmatic^. 7 R. spinalis. 3 A supra-renales superiores. 390 THE VASCULAR SYSTEM. The Supra-re'nal arteries 1 are two small vessels coming from the aorta on a level with the superior mesenteric artery, and proceed out- ward to be distributed to the supra-renal bodies. The Re'nal arteries 2 are two large vessels coming from the sides of the aorta, a short distance below the position of the superior mesenteric artery. The right one is usually a little lower than the left one, and is longer in consequence of the position of the aorta on the left side of the vertebral column. Passing directly outward and backward in front of the crura of the diaphragm, they divide into four or five branches, which enter the sinus of the kidney and are distributed through the organ. They also give small branches to the supra-renal body, 3 the kid- jiey fat, 4 and the pelvis and ureter. Th,e Sperma'tic arteries 5 are long, slender vessels which spring one from each side of the front of the aorta, a short distance below the renal arteries. Each descends outwardly upon the psoas muscle, in company with the ureter, but leaves the latter at the brim of the pelvis, and pro- ceeds to the internal abdominal ring, where it becomes one of the con- stituents of the spermatic cord, and descends to be distributed to the testicle. It gives fine twigs to the ureter ; near the testicle, becomes quite tortuous, and gives branches to the vaginal tunic of the organ. The Ova'rian arteries 6 of the female correspond with those just de- scribed of the male. They have the same origin, and, likewise, the same course as the spermatic arteries to the brim of the pelvis, after which they proceed in a tortuous manner between the folds of the broad liga- ment to the ovary, the Fallopian tube, and the uterus. THE COMMON ILIAC AETERIES. The Common Il'iac arteries 7 are the terminal branches of the abdom- inal aorta, and are given off opposite the body of the fourth lumbar vertebra, slightly to the left of the median line. The two vessels diverge on the sides of the fifth lumbar vertebra; and just above the sacro-iliac symphysis each divides into the internal and external iliac arteries. 1 A. supra-renales ; a. s. mediae, or 6 A. spermaticse ; a. s. internae ; a. norticae ; a. capsulares ; a. atrabilariae. prneparantes ; a. testiculares. * A. renales; a. emulgentes. c A. ovariana; a. spermatica. 3 A. supra-renales inferiores. t A. iliacae communes ; a. i. primitive; 4 A. adiposae. primitive or primary iliac arteries ; a. pelvicrurales. THE VASCULAR SYSTEM. 391 The common iliacs are about two inches in length, and are covered by the peritoneum and intestines. The right one crosses over both common iliac veins as these converge to the inferior cava. FIG. 262. VlW OF THE LEFT SIDE OF THE PELVIS, THE BLADDER, UTERUS, VAGINA, AND RECTUM, turned downward SO as to exhibit the distribution of the internal iliac artery. 1, aorta; 2, right common iliac artery; 3, left common iliac; 4, middle sacral; 5, external iliac; 6, circumflex iliac; 7, epigastric ; 8, internal iliac; 9, ilio-lumbar; 10, lateral sacral arteries; 11, gluteal artery passing from the pelvis, above the pyriform muscle, at the upper part of the great sacro-sciatic foramen ; 12, superior vesical artery ; the branch cut off is extended into the remains of the umbilical artery; 13, obturator artery; 14, inferior vesical artery giving off the uterine artery to the vagina and uterus ; 15, middle hasmorrhoidal artery ; 16, internal pu- dic artery, seen emerging from and again entering the pelvis ; 17, ischiatic artery, a, iliac muscle ; b, psoas muscle ; c, symphysis of the pubis ; d, sacrum ; e, pyriforrn muscle ; /, internal obturator muscle ; g, sacro-sciatic ligaments ; h, rectum ; i, uterus and vagina ; j, Fallopian tube ; k, bladder. THE INTERNAL ILIAC ARTERY. The Internal Il'iac artery 1 is a short, stout vessel which descends from the common iliac into the pelvis, the contents of which, the but- 1 A. iliaca interim ; a. i. posterior; a. hypogastrica ; a. pelvica. 392 THE VASCULAR SYSTEM. tocks, and the generative apparatus it supplies. It extends in front of the sacro-iliac symphysis toward the great sacro-sciatic foramen, and di- vides into two portions, which usually give off branches in the following order: From the posterior division : 1. Ilio-lumbar artery. 2. Lateral sacral arteries. 3. Obturator artery. 4. Gluteal artery. From the anterior division : 5. Vesical arteries. 6. Internal pudic artery. 7. Ischiatic artery. In addition, in the female there come off from the anterior division the uterine and vaginal arteries. 1. The Il'io-lum'bar artery 1 passes outward beneath the psoas muscle, and divides into two branches. Of these, one 2 ascends and sup- plies the psoas and quadrate-lumbar muscles, and anastomoses with the lumbar arteries ; the other 3 crosses the iliac fossa to the crest of the ilium and supplies the iliac muscles, and anastomoses with the circumflex iliac artery. 2. The Lateral Sac'ral arteries, 4 usually two, sometimes arising in common, descend in front of the sacral plexus of nerves, anastomose with the middle sacral artery, and supply the pyriform, coccygeal, and anal elevator muscles. Branches derived from these arteries enter the sacral foramina and supply the contained nerves and membranes, and in part pass out at the posterior foramina to terminate in the neighboring muscles and skin. 3. The Obtura'tor artery, 5 often a branch of the anterior division of the internal iliac, passes forward along the side of the pelvis to the ob- turator foramen, through which it emerges and divides into two branches. Of these, the internal branch 6 is distributed to the adductor, pectineal, and gracilis muscles, and anastomoses with the internal circumflex artery. The external branch 7 is distributed to the obturator, quadrate femoral, 1 A. ilio-lumbaris ; a. ilia parva. 5 A. obturatoria ; a. sub-pubio-femo- 2 Ramus ascendens ; r. lumbaris. ralis. 3 R. transversalis ; r. iliacus. 6 Ramus interims ; r. anterior. 4 A. sacrales laterales. 7 R. externus ; r. posterior. THE VASCULAR SYSTEM. 393 and geminous muscles, to the hip joint, and to the heads of the flexors attached to the tuberosity of the ischium. Within the pelvis the obtura- tor artery gives small branches to the iliac, internal obturator, and anal elevator muscles. Frequently the obturator artery arises, in common with the epigastric, from the termination of the external iliac artery, in which cases it de- scends behind the pubis to the obturator foramen, from whence it pursues the ordinary course. 4. The Glu'teal artery, 1 the continuation of the posterior division of the internal iliac, turns out of the pelvis at the upper part of the great sacro-sciatic foramen, and divides into two branches. The superficial branch runs backward between the middle and great gluteal muscles, which it supplies, together with the skin of the gluteal and sacral regions. The deep branch passes forward between the middle and small gluteal muscles, diverging into many branches, 2 which supply the latter and anastomose with the ischiatic and circumflex arteries. 5. The Ves'ical arteries 3 are generally two in number. The superior ves'ical artery 4 extends through the remains of the umbilical artery of the foBtus to the side of the urinary bladder, to which it is distributed. In its course it gives the deferent artery to the spermatic duct, and a branch to the ureter. The inferior ves'ical artery 3 proceeds to the lower part of the bladder, and also supplies the prostate gland and seminal vesicles. 6. The Internal Pu'dic artery, 6 one of the terminal branches of the anterior division of the internal iliac, descends to the lower part of the great sacro-sciatic foramen, and thence passes from the pelvis. Winding around the spine of the ischium, it again enters the pelvis through the small sacro-sciatic foramen, ascends along the inner side of the rami of the ischium and pubis, and divides into the cavernous and dorsal arteries of the penis. Its branches, including the terminal ones, are as follow : a. Middle haemorrhoidal artery. b. Inferior haemorrhoidal artery. c. Perineal artery. d. Bulbo-urethral artery. e. Cavernous artery. /. Dorsal artery of the penis, or clitoris. 1 A. glutaea ; a. g. superior ; a. iliaca 5 A. v. inferior. posterior. 6 A. pudica interna ; a. pudica ; a. pu- 2 Deep superior and inferior branches. denda ; a. p. interna ; a. p. communis ; a. 3 A. vesicse ; a. vesicales. p. circumflexa ; a. hsemorrhoidea exter- 4 A. v. superior. na. 394 THE VASCULAR SYSTEM. FIG. 263. a. The Middle hsemorrhoid'al artery 1 proceeds from the pudic before it issues from the pelvis, and supplies the lower part of the rectum, the fundus of the bladder, and the prostate gland. It anastomoses with the su- perior and inferior hae- morrhoidal arteries. Sometimes it comes di- rectly from the internal iliac, or it may come off in common with the infe- rior vesical artery. b. The Inferior hsemor- rhoid'al artery 2 is a small branch which comes from the pudic after it re-enters the pelvis, and is dis- tributed to the parts about the anus. c. ThePerine'al artery 3 becomes superficial by piercing the deep perineal 7, perineal branch to the scrotum and skin of the penis ; 8, bulbo- f agc j a an( J j g distributed urethra! artery; 9, cavernous artery; 10, dorsal artery of the penis, a, tuberosity of the ischium; 6, greater sacro-sciatic lig- to the perineum and back ament; c, sphincter of the anus; d, perineal fascia, which is re- p a rt of the SCrotum * OT moved on the opposite side so as to expose the anal elevator muscle; . e, ischio-cavernous muscle; /, bulbo-urethral muscle. labia. 5 A branch Crossing the perineum on the trans- verse perineal muscle, and important in its surgical relations, is named the transverse perineal artery. 6 d. The Bul'bo-ure'thral artery, 7 derived from the pudic just before its division, or from one of its terminal branches, passes transversely inward, and pierces the triangular ligament to reach the bulb of the spongy body, which it penetrates to supply the erectile tissue. e. The Cav'ernous artery, 8 a terminal branch of the pudic, runs a VIEW OF THE PERINEUM, EXHIBITING THE DISTRIBUTION OF THE IN- TERNAL PUDIC ARTERY. 1, the internal pudic issuing from the pel- vis at the lower part of the great sacro-sciatic foramen ; 2, the same vessel after it has returned into the pelvis through the small sacro-sciatic foramen ; 3, inferior haemorrhoidal artery ; 4, 5, super- ficial perineal branches to the perineum ; 6, transverse perineal ; 1 A. hsemorrhoidalis media. 2 A. haemorrhoidalis inferior; a. h. ex- terna. 3 A. perinei ; a. superficialis perinei. 4 A. scrotales posteriores et a. septi. 5 A. labiales posteriores. 6 A. transversa perinei. 7 Artery of the bulb ; bulbar artery ; a. bulbosa; a. bulbo-urethralis. 8 A. cavernosa ; a. profunda penis. THE VASCULAR SYSTEM. 395 short distance between the ramus of the ischium and the cms of the cav- ernous body, and enters this to supply its erectile tissue. /. The Dorsal artery of the penis, 1 or clitoris, 2 the second terminal division of the pudic, ascends between the pubis and cavernous body to the back of the latter, along which it proceeds to the glans. It supplies the fibrous investment of the cavernous body, the glans, and the skin, and anastomoses with branches of the bulbo-urethral and cavernous arteries. 7. The Ischiat'ic artery, 3 the remaining branch of the anterior divi- sion of the internal iliac, passes from the pelvis in company with the pudic artery and great sciatic nerve, at the lower part of the great sacro-sciatic foramen. Descending in the interval of the tuberosity of the ischium and the great trochanter, covered by the great gluteal muscle, it gives branches to the latter, the small rotators upon which it rests, the skin about the coccyx, 4 the sciatic nerve, 5 and hip joint, and it anastomoses with the gluteal and circumflex arteries. 8. The U'terine artery, 6 a branch of the anterior division of the in- ternal iliac, sometimes arising in common with the superior vesical artery, passes within the broad ligament and ascends in ,a tortuous man- ner to the side of the uterus. It also gives branches to the vagina, Fal- lopian tube, round ligament, and ovary, and anastomoses with the ovarian artery. 9. The Vag'inal artery, 7 a branch of the anterior division of the internal iliac, sometimes arising in common with the uterine, inferior vesical, or middle heemorrhoidal artery, supplies the walls of the vagina and the contiguous parts of the rectum and urinary bladder. THE EXTERNAL ILIAC ARTERY. The External Il'iac artery, 8 the second division of the common iliac, runs along the brim of the pelvis, resting against the psoas muscle, to the femoral arch, beneath which it passes out to assume the name of femoral artery. The corresponding iliac vein at first is behind it, and afterwards to its inner side. It gives off no branches of importance until it is about passing under the femoral arch, when it sends off the epigastric and circumflex iliac arteries. 1 A. dorsalis penis. 5 Comes nervis ischiadici. '* A. d. clitoridis. fi A. uterina; a. u. hypogastrica. 3 A. ischiadica ; a glutaea inferior ; a. 7 A. vaginalis. sciatica; a femoro-poplitea. A. iliaca externa; a. i. anterior; cru- 4 A. coccygeeo. ral artery ; a. cruralis; a. c. iliaca. 396 THE VASCULAR SYSTEM. 1. The Epigastric artery 1 springs from the fore part of the external iliac, and ascends obliquely inward, between the peritoneum and trans- verse fascia, to the straight muscle of the abdomen. Piercing the sheath of this muscle, and ascending behind it, the artery mainly supplies the latter, and anastomoses with the termination of the mammary artery. In its course it crosses the inguinal canal and gives a branch 2 to the spermatic cord. Subsequently it gives branches to the broad abdominal muscles, which anastomose' with the lumbar and circumflex iliac arteries. 2. The Circumflex Il'iac artery, 3 smaller than the preceding, runs outward from the external iliac, behind Poupart's ligament, to the crest of the ilium. Proceeding along the latter, it gives branches to the iliac and abdominal muscles, and anastomoses with the ilio-lumbar, lumbar, and epigastric arteries. THE FEMORAL ARTERY. The Fern/oral artery, 4 the continuation of the external iliac, proceeds from the femoral arch, downward and inward, in the groove of the thigh, between the extensor and adductor muscles. Becoming gradually deeper in its descent, at about the commencement of the lower third of the thigh it pierces the insertion of the great adductor muscle, and assumes the name of popliteal artery. It passes through the middle of a tri- angular space, whose base is formed by Poupart's ligament, the outer side by the sartorius muscle, and the inner side by the border of the adductor muscles. A line extended from the middle of the groin to the inner side of the knee-cap would nearly indicate its course. In succes- sion, it rests on the pectineal, long adductor, and great adductor muscles. At the femoral arch the corresponding vein lies at its inner side, but gradually assumes a position behind as it approaches the perforation of the great adductor. At the upper third of the thigh it is covered by the skin and fascia ; lower down, in addition, by the sartorius muscle. The branches of the femoral artery are as follow : 1. External pudic arteries. 2. Superficial epigastric artery. 3. Superficial circumflex iliac artery. 4. Profound femoral artery. 5. Muscular branches. 6. Anastomotic artery. 1. The External Pu'dic arteries 5 are two or three small vessels 1 A. epigastrica; a. e. inferior; a e. i. 4 A. femoralis; a. cruralis ; a. pelvi- interna. cruralis. 2 A. spermatlca externa. 5 A. pudendae externse; a. pudenda ex- 3 A. circumflexa iliaca. terna superior et inferior; a. scrotales et labiales anteriores. THE VASCULAR SYSTEM. 897 from the commencement of the femoral artery, which pass through the pectineal and cribriform fasciae FJG 264 to the region of the pubis, where * they are distributed to the skin of the penis and scrotum, or, in the female, to the mons veneris and labia. 2. The Superficial Epigas'tric artery 1 arises a little below the femoral arch, perforates the falci- form process, and ascends in the superficial fascia of the abdomen toward the umbilicus. 3. The Superficial Circumflex il'iac artery, 2 often a branch of the preceding, follows the course of Poupart's ligament to the ilium, dividing into branches which pierce the fascia and supply the groin 3 and integument. ARTERIES OF THE FRONT OF THE THIGH. 1, femoral artery ; 2, popliteal artery ; 3, posterior tibial ar- tery ; 4, superficial epigastric artery ; 5, superficial circumflex iliac; 6, external pudics; 7, profound femoral artery ; 8, 9, external and internal circum- flex arteries; 10, perforating arteries; 11, muscular branches ; 12, anastomotic artery ; 13, 14, internal articular arteries ; 15, small branch from the epi- gastric ; 16, dorsal arteries of the penis, a, rectus muscle ; b, internal vastus ; c, d, e, adductor mus- cles ; /, semi-tendinous muscle ; g, sartorius muscle. 4. The Profound Fern/oral ar- tery* comes from the outer back part of the femoral, an inch or two below Poupart's ligament, and is nearly as large as the continu- ation of the parent trunk. It de- scends behind the latter, proceeds between the short and long adductors, and thence upon the great ad- ductor, which is perforated by its terminal branches. In its course it is distributed through the following-named branches : 1 A. epigastrica superficialis ; a. abdo- externa; ramus iliacus of the sup. epi- minalis subcutanea ; a. ad cutem abdo- gastric. 3 A. inguinales. femoralis minis. 2 A. circumflexa ilii superficialis or 4 A. profunda femoris ; profunda. 398 THE VASCULAR SYSTEM. a. Internal circumflex artery. 6. External circumflex artery, c. Perforating arteries. a. The Internal cir'cumflex artery 1 comes from the commencement of the profound femoral, and turns backward between the psoas and pectineal muscles, above the lesser trochanter, to the posterior part of the neck of the femur. In its course it gives branches to the iliac, psoas, pectineal, gracilis, and external obturator muscles, 2 the heads of the ad- ductors, and the hip joint. 3 In terminating it divides into two branches, of which one* ascends to supply the small rotators and the lower part of the great gluteal muscle, anastomosing with the ischiatic and gluteal arteries ; while the other branch 5 descends and supplies the quadrate femoral muscle and the heads of the great adductor and flexors of the thigh. b. The External circumflex artery, 6 larger than the preceding, and arising a little lower, passes outward between the iliac and rectus muscles and divides into a series of ascending and descending branches. The former supply the tensor of the femoral fascia, the sartorius, rectus, small and middle gluteal, and external vastus muscles ; the latter supply the quadriceps extensor and the skin on the outer part of the thigh. c. The Perforating arteries, 7 three or four in number, are successive divisions of the profound femoral artery which pierce the insertion of the adductors to reach the back of the thigh, where they are resolved in branches supplying the great gluteal, adductor, and flexor muscles, and anastomosing with the ischiatic and circumflex arteries and with one another. The medullary nutritious arteries of the femur 8 are branches of the perforating arteries. 5. The Muscular branches 9 of the femoral artery are small vessels given off in the course of the latter to the sartorius, gracilis, extensor, and adductor muscles. 6. The Anastomot r ic artery 10 is a slender vessel springing from the femoral as this is about to pass through the perforation of the great 1 A. circumflexa interna; a. c. femoris 7 A. perforantes; a. perfovans prima, interna, or posterior. secunda, et tertia. 2 Ramus superficialis. 8 A. nutritise ; a. nutritia femoris su- 3 A. articularis ; a. acetabuli. perior et inferior, or magna. * Ramus trochantericus. 9 Rami musculares. 5 R. descendens. 10 A. anastomotica magna; ramus mus- 6 A. circumflexa externa; a. c. femoris culo-articularis and a. articularis genii externa, or anterior. superficialis, or a. a. g. s. superior inter- na or prima. THE VASCULAR SYSTEM. 399 adductor. Descending upon the tendon of the latter and giving it branches, it also supplies the internal vastus, sartorius, and gracilis muscles, and terminates at the knee by anastomosing with all the other contiguous arteries. THE POPLITEAL ARTERY. ARTERIES OF THE BACK OF THE THIGH. 1, gluteal artery; 2, 3, its superficial and deep branch; 4, in- ternal pudic artery; 5, ischiatic artery; 6, branch of the external circumflex ; 7, 8, terminal branches of the perforating arteries; 9, popliteal artery; 10, 11, superior internal and external articular ar- teries ; 12, 13, inferior internal and external artic- ular arteries; 14, middle articular artery ; 15, gas- trocnemial branches, a, origin and insertion of the great gluteal muscle; b, origin of the middle glu- teal muscle; c, small gluteal muscle; d, great tro- chanter; e, pyriform muscle; /, sacro-aciatic lig- aments ; g, internal obturator muscle ; h, quadrate femoral muscle ; i, sciatic nerve ; j, tuberosity of the ischium ; A-, external vastus muscle ; I, great adductor; TO, short head of the biceps; , long head; o, p, semi-membranous and semi-tendinous muscles ; q, gracilis ; r, gastrocnemius. The Poplite'al artery 1 is the name assumed by the femoral after its passage through the tendon of the great adductor at the lower third of the thigh. It extends along the back of the lat- ter, behind the middle of the knee joint, to the lower border of the popliteal muscle, where it divides into the anterior and posterior tibial arteries. Occupying the deep- est part of the popliteal space, it rests in succession against the fe- mur, the capsular ligament of the knee j oint, and the popliteal muscle. In contact with it posteriorly is the corresponding vein ; between which and the skin is the posterior tibial nerve. The branches of the popli- teal artery, including the terminal ones, are as follow : FIG. 265. //r ' 1 A. poplitea; popliteal portion of the crural artery. 400 THE VASCULAR SYSTEM. 1. Articular arteries. 2. Muscular branches. 3. Anterior tibial artery. 4. Posterior tibial artery. 1. The Artic'ular arteries 1 are five small vessels which spring from the popliteal artery and supply the knee joint and its contiguous struc- tures. The superior articular arteries 2 wind around the femur, one above each condyle, to the front of the knee joint. Of the inferior articular arteries, 3 one turns around the external semilunar cartilage, while the other takes its course below the internal condyle of the tibia ; both reaching the front of the knee. These four vessels, together with the anastomotic and recurrent tibial arteries, produce an intricate vas- cular net, 4 enveloping the front and sides of the knee. The middle articular artery 3 penetrates the back of the capsular ligament and sup- plies the crucial ligaments and synovial folds of the knee joint. 2. The Muscular branches of the popliteal artery consist of two or three from its upper part to the flexor and vast! muscles, and one or two 6 from its lower part to the gastrocnemius muscle and skin of the calf. THE ANTERIOR TIBIAL ARTERY. The Anterior TiVial artery, 7 the smaller of the terminal divisions of the popliteal, passes through the opening at the upper part of the inter- osseous membrane, and descends in front of this to the instep, where it assumes the name of dorsal pedal artery. It is accompanied by two companion veins and the anterior tibial nerve ; at first lies between the long extensor of the toes and the anterior tibial muscle, and afterwards between the latter and the extensor of the great toe. At the ankle it is crossed by the tendon of the muscle last named, and is covered by the annular ligament. Its branches are as follow: 1. Recurrent tibial artery. 2. Muscular branches. 3. External malleolar artery. 4. Internal malleolar artery. 1 A. articulares ; a. a. genu superiores, 6 A. art. genu media ; a. a. genu azy- inferiores, et media. gos. 2 A. articularis superior interna et ex- 6 A. surales ; a. gemellse ; a. surales terna ; a. a. genu sup. int. secunda or profundae et superficialis ; gastrocnemial profunda and a. a. g. s. externa. or sural arteries. 3 A. art. inferior interna et externa. 7 A. tibialis antica. * Rete articulare genu. THE VASCULAR SYSTEM. 401 FIG. 266. 1. The Recurrent Tib'ial artery 1 ascends beneath the origin of the anterior tibial muscle to the front of the knee, and is there distributed, anastomosing with the articu- lar arteries. 2. The Muscular branches are numerous small vessels to the contiguous muscles. 3. The External Malle'olar artery 2 passes out- wardly at the lower part of the leg, beneath the extensor tendons, and ramifies on the external ankle, supplying the neighboring structures, and anastomosing with the peroneal and tarsal arteries. 4. The Internal Mal- le'olar artery, 3 small- er than the 'preceding, tibial; 3 > dorsal P edal ; *. 5, external and internal malleolar arteries; 6, ARTERIES OF THE FRONT OF THE LEG. 1, anterior tibial artery; 2, recurrent passes beneath the ten- don of the anterior tibial muscle and rami- fies over the internal ankle, anastomosing with branches of the posterior tibial and tarsal arteries. metatarsal artery ; 7, dorsal artery of the great toe ; 8, terminal branches of the articular arteries, a, tibia; b, anterior tibial muscle; c, extensor of the great toe ; d, long extensor of the toes : the short extensor occupies the back of the foot; e, peroneal muscles : on each side of the leg the bellies of the gastrocnemius are visi- ble. THE DORSAL PEDAL ARTERY. The Dorsal Pe'dal artery, 4 the continuation of the anterior tibial, extends from the bend of the ankle over the instep to the commencement of the first interosseous space, where it dips to the sole of the foot to contribute in the formation of the plantar arch. Its branches are as follow : 1. Tarsal arteries. 2. Metatarsal artery. 3. Dorsal artery of the great toe. 1. The Tar 'sal arteries 5 consist of several small branches to the inner 1 A. tibialis recurrens. - A. malleolaris externa. 3 A. malleolaris interna. 4 A. dorsalis pedis. 5 A. tarseae; a. t. internae and externee. 26 402 THE VASCULAR SYSTEM. side of the tarsus, and a large branch which crosses the latter beneath the short extensor of the toes and supplies the outer part of the tarsus. FIG. 267. 2. The Metatar'sal artery 1 crosses the base of the metatarsus and supplies the outer part of the foot, anastomosing with the tarsal and external plantar arteries. In its course it gives off branches 2 to the outer three metatarsal spaces, which subse- quently subdivide 3 to supply the contiguous sides of the outer four toes and the outer side of the little toe. 3. The Dorsal artery of the great toe 4 runs forward on the first interosseous space, and sup- plies the inner and outer sides of the great toe and the adjoining side of the second toe. 5 THE POSTERIOR TIBIAL ARTERY. ARTERIES OF THE BACK OF THE LEG. 1, popliteal artery; 2, 2, superior in- ternal and external articular arteries; ial artery, 6 the remain- 3, 3, inferior internal and external . d i vision O f the pop . articular arteries; 4, middle articular artery ; 5, gastrocnemial arteries ; 6, peroneal artery; 7, posterior peroneal branch; 8, posterior tibial artery ; 9, calcanean branches, a, popliteal mus- cle ; b, c, origin of the gastrocnemius ; fa e ] e ~ curv es arOUlld d, peroneal muscles ; e, long flexor of the great toe; /, long flexor of the toes ; that between the two latter is the posterior tibial muscle. The Posterior Tib'- liteal, and appearing as a continuation of it, descends the back of the inner ankle to the concavity of the calca- neum, and divides into the two plantar arteries. It is accompanied by two veins and the posterior tibial nerve, and is situated behind the tibia, with the posterior tibial and long flexor muscle of the toes interposed. Its upper part is covered by the muscles of the calf, but be- hind the inner ankle is covered only by the skin and fascia. Its branches are as follow : 1 A. metatarsea. L> A. interosseae. 3 A. digitales dorsales ; dorsal collat- eral digital branches. * A. dorsalis liallucis or pollicis pedis ; a. interossea dorsalis prima. 5 A. digitales dorsales; dorsal collat- eral digital branches. 6 A. tibialis postica. THE VASCULAR SYSTEM. 403 1. Peroneal artery. 2. Muscular branches. 3. Medullary nutritious artery. 4. Calcanean arteries. 5. Internal plantar artery. 6. External plantar artery. 1. The Perone'al artery 1 arises an inch or two below the commence- ment of the posterior tibial, and turns outward to descend along the back of the fibula. In the first part of its course it rests on the posterior tibial muscle, covered by the soleus ; subsequently lies on the interos- seous membrane close to the fibula, and is covered by the long flexor of the great toe. It gives branches to the contiguous muscles, and finally divides into the anterior and posterior peroneal arteries. a. The Anterior perone r al artery 2 pierces the interosseous membrane at the lower part of the leg, and is distributed . in front of the outer ankle, anastomosing with the external malleolar and tarsal arteries. b. The Posterior perone'al artery 3 descends along the -back of the outer ankle to the side of the calcaneum, distributing branches to the heel* and parts about the external ankle. 5 By a short transverse branch 6 it anastomoses with the posterior tibial artery ; and by other and smaller branches it inosculates with the external malleolar, tarsal, and external plantar arteries. 2. The Muscular branches of the posterior tibial artery consist of about a dozen small vessels sent to the contiguous muscles. 3. The Med'ullary Nutritious artery 7 enters the corresponding fora- men, at the upper part of the tibia, to supply the marrow. 4. The Calca'nean arteries 8 are two or three branches from the lower part of the posterior tibial artery, passing inward to be distributed to the heel, the tarsus, and the heads of the muscles of the sole of the foot. 5. The Internal Plant'ar artery, 9 one of the terminal divisions of the posterior tibial, runs along the inner side of the sole of the foot above the abductor of the great toe. In its course it gives deep branches to the tarsus, and superficial ones to the contiguous muscles and skin, and ends by anastomosing with the digital arteries of the great toe. 1 A. peronea ; a. fibularis. 6 R. anastomoticus transversus. 2 A. peronea antica ; a. p. perforans. 7 A. nutritia tibiae ; nutritious artery. 3 A. p. postica. 8 Rami calcanei interni. 4 Rami calcanei externi. A. plantaris interna. 5 R. malleolares externi postici. 404 THE VASCULAR SYSTEM. 6, The External Plant'ar artery, 1 larger than the preceding, inclines outward and forward to the base of the last metatarsal bone, and then curves inwardly to form, in conjunction with the termination of the dorsal pedal artery, the plan- tar arch. In its course it lies be- tween the short flexor of the toes and the accessory flexor, and sub- sequently between the latter and the short flexor of the little toe. To these and other muscles, and the skin on the inner side of the foot, it gives branches, as well as a dig- ital branch 2 to the outer side of the little toe. The Plant'ar arch, 3 formed by the union of the external plantar and dorsal pedal arteries, lies against the interosseous muscles at the base of the metatarsus, cov- ered by the flexor muscles and ten- dons. Besides giving branches to the contiguous muscles and articu- lations, it sends off the perforating and digital arteries. a. The Perforating arteries 4 are small vessels which penetrate between the bases of the metatarsal bones to anastomose with the interosseous branches of the metatarsal artery. b. The Digital arteries, 5 four in number, advance in the corre- sponding spaces to the clefts of the toes, and there divide into digital branches 6 which run along the contiguous sides of the latter. The first digital artery 7 also gives a digital branch 8 to the inner side of the great toe. ARTERIES OF THE SOLE OF THE FOOT. 1, posterior tibial artery dividing into 2 the internal, and 3 the external plantar arteries; 4, branch to the inner side of the foot ; 5, branch to the great toe; 6, plan- tar arch; 7, perforating arteries; 8, common digi- tals ; 9, digitals to the contiguous sides of the toes ; 10, calcanean branches of the peroneal and poste- rior tibial arteries. 1 A. plantaris externa. a A. digitalis plantaris externa. 3 Arcus plantaris. * A. perforantes. 5 A. interosseae. 6 A. digitales pedis plantares; plantar collateral digital branches. 7 A. magna pollicis. 8 A. digitalis plantaris interna. THE VASCULAR SYSTEM. 495 THE PULMONARY ARTERY. The Pul'monary artery, one of the main trunks of the arterial system, conveys dark blood from the heart to the lungs. It is a short, wide ves- sel springing from the anterior part of the base of the right ventricle, and curves for about two inches upward, backward, and to the left side. Its origin conceals that of the aorta, but higher it crosses to the left side ,of the latter vessel, in front of the left auricle, and finally divides be- neath the arch of the aorta into two branches the right and left pulmo- nary arteries. At its bifurcation it is connected to the under side of the aortic arch by a short fibrous cord, which is the remains of a vessel of foetal life named the ductus arteriosus. The Right Pulmonary artery, longer than the left, passes nearly transversely outward behind the ascending aorta and superior cava to the root of the right lung, of which it forms a part. The Left Pulmonary artery passes transversely in front of the de- scending aorta into the root of the left lung. THE VEINS. The Veins comprise eight trunks, with their branches, as follow : The Cor'onary vein, which, with its branches, collects blood from the walls of the heart and conveys it to the right auricle. The Superior and Inferior Cava, by whose branches blood is collected from most all parts of the body, and is then conveyed to the right auri- cle of the heart. The Port'al vein, which originates by many branches from the stom- ach, intestines, spleen, and pancreas, and is distributed by another series of branches through the liver. The four Pul'monary veins which convey the aerated blood from the lungs to the left auricle of the heart. THE CORONARY YEIN. The Cor'onary vein 1 commences at the apex of the heart, ascends in the groove between the ventricles in front, and then winds around the left auriculo-ventricular groove to the back of the heart, where it term- inates in the right auricle. In its course it receives car'diac branches 1 Vena coronaria; v. c. magna; v. cordis magna; great cardiac vein; coronary sinus of the heart. 406 THE VASCULAR SYSTEM. from both ventricles, and from the left auricle. Its orifice is protected by a valve. 1 The Posterior Car'diac vein 2 commences at the apex of the heart, and ascends between the ventricles posteriorly to terminate in the coro- nary vein. In its course it receives cardiac branches from J^th ven- tricles. The Anterior Car'diac vein, 3 frequently represented by a pair of veins, runs from the front of the heart along the right auriculo- ventricu- lar groove to terminate posteriorly in the coronary vein. In its course it receives cardiac branches from the right auricle and ventricle. Be- sides these several small cardiac veins 4 ascend from the right ventricle to open separately into the right auricle. THE SUPERIOR CAVA. The Superior Cava 5 is the great venous trunk which derives its branches from the head, neck, upper extremities, and walls of the tho- rax. . It is placed to the right of the aortic arch in front of the root of the right lung, and commences behind the first costal cartilage of the right side by the conjunction of the two innominate veins. In its descent it receives the azygos vein, and terminates at the upper back part of the right auricle of the heart. It is less voluminous than the arch of the aorta, and is destitute of valves. THE INNOMINATE VEINS. The Innominate veins 6 commence one on each side, behind the sterno-clavicular articulation, by the union of the internal jugular and subclavian veins. The Right innom'inate vein 7 descends in front of the corresponding artery ; the Left innominate vein, 8 much longer than the other, crosses in front of the arteries springing from the summit of the aortic arch to the right side, where it joins its fellow to form the superior cava. The innominate veins are destitute of valves, and, besides the branches 1 Valvula Thebesii; v. Guiffartiana; 5 Vena cava superior; v. c. descendens; v. venae magnae. v. c. thoracica ; v. hepatites. 2 V. cordis media ; middle cardiac 6 Venae innominatae ; v. anonymae ; v. vein. brachio-cephalicae. 3 V. cordis parva ; small, or anterior 7 V. innominata dextra. cardiac vein. 8 V. innominata sinistra ; v. transversa; 4 V. cordis minimae ; smallest cardiac the transverse vein, veins. THE VASCULAR SYSTEM. 407 which conjoin in their formation, they receive the internal mammary, vertebral, and inferior thyroid veins, and usually the left superior intercos{J| vein. The Internal Mam/mary veins, 1 a pair of companions to the corre- sponding artery, receive branches in accordance with the distribution of the latter, and finally unite to terminate in the innominate vein ; though frequently the left one joins the superior cava. The Vertebral vein 2 is. a small vessel occupying the foramina of the transverse processes of the cer- vical vertebrae in company with the vertebral artery. It commences from branches on the occiput, re- ceives others in its course down the neck from the neighboring muscles and spinal sinuses, and terminates in the innominate or subclavian vein. The Inferior Thy'roid vein, 3 formed by numerous branches in the thyroid gland, also receives others from the pharynx, larynx, oesophagus, and trachea, and ter- minates in the innominate vein. Sometimes the veins of the two sides conjoin in a single vessel 4 de- scending in front of the trachea to end in the middle of the left in- nominate vein. VEINS OF THE THORAX AND ABDOMEN. 1, inferior cava; 2, right, 3 left renal veins; 4, superior cava; 5, right. 6 left innominate veins; 7, internal veins; 8, external jugular veins ; 9, subclavian vein ; 10, azygos vein ; 11 inferior, 12 superior hemiazygos veins. 1 V. mammarise internee. 2 V. vertebralis. 3 V. thyroidea inferior. 4 V. thyroidea ima: v. t. impar; v. t. axygos. 408 THE VASCULAR SYSTEM. YEINS OF THE HEAD AND NECK. The two Ju'gular veins 1 are the principal ones of the head and neck, and are situated at the side of the latter. The internal jugular vein FIG. 270. VEINS OF THE HEAD AND NECK. 1, frontal vein ; 2, nasal vein ; 3, 4, labial veins ; 5, facial vein ; 6, lingual vein; 7, internal jugular vein; 8, 9, posterior and anterior temporal veins; 10, transverse facial vein ; 11, internal maxillary vein ; 12, posterior auricular vein ; 13, external jugular vein; 14 posterior, 15 anterior jugular veins, a, external carotid artery; b, sterno-mastoid muscle; c, trapezius; d, pectoral muscle; e, deltoid muscle. corresponds with the deep veins which accompany the large arteries of the limbs. It receives the blood from the interior of the cranium and 1 V- jugulares; v. soporales; v. apoplecticae ; v. sphagitides. THE VASCULAR SYSTEM. 409 orbit usually the greater part of that of the exterior of the cranium, and generally most of that of the face and neck. The external jugular vein corresponds with the large superficial veins of the limbs, and re- ceives a portion of the blood from the exterior of the cranium, and usually f^m the face and neck. All the veins of the head and neck, except the jugulars, are destitute of valves. THE INTERNAL JUGULAR VEIN. The Internal Ju'gular vein 1 commences in a bulb-like dilatation 2 at the jugular foramen of the cranium, and there receives the blood of the sinuses of the dura mater. It descends the neck at the outer side of the internal and common carotid arteries, and finally conjoins with the subclavian to form the innominate vein. In its course down the neck it generally receives the facial, lingual, pharyngeal, superior thyroid, and occipital veins, and sometimes the tempero-maxillary vein in whole or part. The internal jugular vein varies in size reciprocally with that of the opposite side, and with the size of the external jugular vein. More frequently that of the right side is the larger. Further, it often varies in the number of branches which conjoin to form it on the two sides of the neck. Its lower part is frequently more or less dilated, and at the termination is provided with a pair of valves. SINUSES OF THE DURA MATER. The Si'nuses of the Dura Mater 3 are venous channels formed between the layers of the latter membrane and lined with a continuation of the ordinary lining membrane of blood-vessels. They receive the veins of the brain and its membranes, those of the bones of the cranium, and those of the orbit ; and the blood obtained from all these sources they convey to the internal jugular veins. They are destitute of valves, and do not accompany corresponding arteries. The Lateral Sinus, 4 on each side of the cranial cavity, is the main channel to which all the other sinuses converge. It commences at the internal occipital protuberance, in the so-called confluence of the 1 V. jugularis interna; v j.magna; v. 3 Sinus durae matris; fistulae, cavita- j. cerebralis; v. cephalica; v. apoplec- tes, ventriculi, tubuli, sanguiductus, or tica. receptacula durae matris. 2 Bulbus venae jugularis ; gulf or si- 4 S. lateralis ; s. transversus ; s. ten- nus of the jugular vein. torii posterior; s. t. sigmoidus; s. mag- nus. 410 THE VASCULAR SYSTEM. sinuses, 1 which is produced by the union of the superior longitudinal, straight, and posterior occipital sinuses. Proceeding outwardly along the groove of the trans- verse limb of the occip- ital cross, it tlmn curves downward and inward in the groove of the mas- toid portion of the tem- poral bone, and termin- ates at the jugular foram- en by joining the jugular vein. The Superior Longi- tudinal sinus, 2 a single channel for the two sides of the cranial cavity, com- mences at the bottom of the frontal crest, and pro- ceeds backward along the convex border of the cere- bral falx to the confluence of the sinuses. It is tri- lateral, increases in size from before backward, and gives rise to the shal- low groove along the me- dian line of the cranial vault. It receives the superior and median ce- rebral veins. The Inferior Longitu- dinal sinus 3 is a single small vessel which runs along the concave border of the cerebral falx, and terminates posteriorly in the straight sinus. The Straight sinus, 4 single for the two sides of the cranium, is situ- ated along the conjunction of the cerebral falx with the tentorium, and SINUSES AT THE BASE OF THE CRANIUM, with the right orbit ex- posed, a, eyeball; Coptic nerve; c, occipital foramen ; d,e,f, anterior, middle, and posterior cranial fossae. 1, confluence of the sinuses from which the lateral sinus on each side passes off to terminate at the jugular foramen; 2, ophthalmic vein; 3, cavern- ous sinus; 4, circular sinus surrounding the pituitary fossae ; 5, anterior occipital sinus; 6, 7, superior and inferior petrosal sin- uses; 8, posterior occipital sinus; 9, commencement of the in- ternal jugular vein. 1 Confluens sinuum ; torcular Hero- phili; wine-press of Herophilus; fourth sinus. 2 Sinus longitudinalis superior ; s. fal- ciformis; s. f. superior; s. triangularis; s. medianus. 3 S. longitudinalis inferior ; s. falci- formis; s. f. inferior; s. minor; vena falcis cerebri. 4 S. rectus; s. quartus; s. tentorii; s. perpendicularis ; s obliquus ; s. choroi- deus. THE VASCULAR SYSTEM. 411 terminates in the confluence of the sinuses. It is trilateral at its com- mencement receives the preceding sinus and the ventricular veins, and in its course receives veins from the neighboring FIG. 272. parts of the cerebrum and cerebellum. The Cav'ernous sinus 1 is situated at the side of the pituitary fossa, and is short but capacious. Its cavity is crossed by fibrous bands or offsets of the dura mater, from whence the sinus derives its name. A more re- markable peculiarity con- sists in its walls inclosing the ophthalmic, pathetic, oculo-motor, and abdu- cent nerves, and the in- ternal carotid artery, which, however, are sep- arated from its cavity by the lining membrane. Its fore part receives the ophthalmic vein, and its back part communicates with the petrosal sinuses. The Circular sinus 2 surrounds the pituitary body, and communicates on each side with the cavernous sinus. The Superior Petro'sal sinus 3 is a narrow channel which extends from the cavernous sinus, along the border of the tentorium attached to the edge of the petrous portion of the temporal bone, to the lateral sinus. The Inferior Petro'sal sinus 4 extends from the cavernous sinus along the lower border posteriorly of the petrous portion of the temporal bone to join the termination of the lateral sinus. The Anterior Occip'ital sinus, 5 sometimes represented by a pair of VERTICAL SECTION OF THE SKULL, exhibiting the sinuses of the dura mater. 1, superior longitudinal sinus ; 2, termination of the superior cerebral veins; 3, inferior longitudinal sinus; 4, internal cerebral veins; 5, straight sinus; 6, 7, superior and inferior petrosal sinuses of the right side; 8, right lateral sinus; 9, commencement of the left lateral sinus; 10, internal jugular vein, a, cerebral falx ; b, tentorium ; c, cerebellar fossa ; d, partition of the nose ; e, frontal sinus; /, sphenoidal sinus. 1 S. cavernosus ; receptaculum. 2 S. circularis; s. c. Ridleyi; s coro- narius; s. ellipticus. 3 S. petrosus superior ; s. tentorii late- ralis. 4 S. p. inferior. 6 S. occipitalis anterior ; s. basilaris ; transversus. 412 THE VASCULAR SYSTEM. sinuses, is a transverse channel of communication between the inferior petrosal sinuses, across the basilar process of the occipital bone. The Posterior Occip'ital sinus, 1 frequently represented by a pair of sinuses, commences in small veins at the sides of the occipital foramen, and ascends along the convex border of the cerebellar falx to terminate in the confluence of the sinuses. VEINS OF THE BRAIN. The veins which emanate from the substance of the brain form an in- tricate net-work in the pia mater, and collect into large branches which generally follow the course of the fissures on the surface of the brain to the nearest sinuses of the dura mater. The Superior Cer'ebral veins 2 ascend from the outer surface of the cerebral hemispheres, and terminate in the superior longitudinal sinus. They pierce the dura mater obliquely and open forward into the sinus. The Median Cer'ebral veins 3 ascend from the sides of the longitudinal fissure to the superior longitudinal sinus. The Inferior Cer'ebral veins 4 open into the nearest sinuses : those from the fore part of the cerebrum into the cavernous sinuses, those from the back part into the lateral and straight sinuses, and those intermediate into the superior petrosal sinuses. The Internal Cer'ebral veins, 5 two in number, pass backward along the middle of the choroid membrane of the third ventricle, and, united in a short trunk, 6 or separately, terminate in the commencement of the straight sinus. They derive branches from the choroid plexuses, striate bodies/ thalami, fornix, and cerebral crura. The Superior Cerebel'lar veins 8 terminate in the straight sinus. The Inferior Cerebel'lar veins, 9 together with branches from the pous and medulla oblongata, end in the inferior petrosal, posterior occipital, and lateral sinuses. 1 S. occipitalis; s. o. posterior. e y. magna Galeni. 2 V. cerebrales superiores. 7 Vena choroidea et corporis striati. 3 V. c. medianae. 8 y. cerebelli superiores. 4 V. c. inferiores. 9 y. cerebelli inferiores. 3 V. cerebri internae ; v. c. magnae ; Y. Galeni; v. choroidese. THE VASCULAR SYSTEM. 413 THE DIPLOIC AND MENINGEAL YEINS. The Dip'loic veins 1 ramify in the spongy structure of the bones of the cranium, and communicate with the neighboring veins of the scalp, orbit, and dura mater, or with the sinuses of the latter membrane. The Menin/geal veins, 2 of which two accompany each corresponding artery, continue in the course of the arteries or terminate in the sinuses of the dura mater. The Great menin'geal veins 3 either terminate in the internal maxillary vein or in the cavernous sinus. THE OPHTHALMIC VEIN. The Ophthalmic vein, 4 possessing the same general arrangement as the corresponding artery, commences at the internal canthus of the eye, where it anastomoses with the facial vein. Passing back along the inner part of the orbit, it emerges at the sphenoidal foramen to end in the cavernous sinus. THE EXTERNAL JUGULAR VEIN. The External JVgular vein, 5 much smaller than the internal jugular, is formed by the union in whole or part of the tempero -maxillary with the posterior auricular vein, or it may be a continuation of the latter alone or in union with the facial vein. It descends from the vicinity of the angle of the jaw, crossing the sterno-mastoid muscle under cover of the subcutaneous cervical muscle, and terminates behind the middle of the clavicle by joining the sub- clavian vein. It usually possesses a valve about the middle of its course, and another at its termination. Besides its branches of origin, it gen- erally receives the following : The Anterior jugular vein, 6 from the front of the neck. The Posterior jugular vein, 7 from the back of the neck. The Supra-scap'ular vein, 8 pursuing the direction of the correspond- ing artery. The Transverse cer'vical vein, 9 likewise a companion of the corre- sponding artery. 1 V. diploeticae. e y. jugularis anterior; v. j. mediana ' l V. meningeae. colli ; v. cutanea colli anterior. 3 V. m. magnae ; v. m. mediae. 7 V. jugularis posterior. 4 V. ophthalmica. s y. supra-scapularis. 5 V. jugularis externa; v. cutanea colli V. transversa cervicis. posterior ; v. trachelo-subcutanea. 414 THE VASCULAR SYSTEM. THE FACIAL VEIN. The Fa'cial vein 1 pursues the general course of the facial artery, but is less tortuous, and is more posteriorly situated. It commences at the in- ternal canthus of the eye, under the name of the Angular vein, 2 which is usually visible during life through the skin. In this position it anasto- moses with the ophthalmic vein, and commonly receives the Frontal vein. 3 The latter communicates with the temporal veins, and descends near the middle of the forehead to the root of the nose, across which it frequently anastomoses with the opposite vein ; and it often terminates in the oph- thalmic vein. Near the angle of the jaw the facial vein most frequently ends in the internal jugular, and sometimes joins the tempero-maxillary vein to empty with it into the external jugular, or it may terminate in the latter alone. In its course it generally receives the following branches : The Supra-orb'ital vein, 4 which runs along the superciliary ridge and receives the superior pal/pebral veins 5 from the upper eyelid. The Na'sal veins, 6 from the side of the nose. The Inferior pal'pebral veins, 7 from the under eyelid. The Masseter/ic and Buc'cal veins, 8 from the cheek. The Labial veins, 9 from the lips. The Submen'tal vein, 10 from the vicinity of the chin. The Submax'illary veins, 11 from the corresponding gland. The Pal'atine vein, 12 from the soft palate and tonsil. THE TEMPORAL VEIN. The Tem'poral vein 13 and its branches have the same general course as the corresponding arteries, but are less tortuous. The anterior temporal vein 14 anastomoses with the frontal vein ; the posterior temporal 15 with the occipital vein. The common temporal penetrates the parotid gland, and at the neck of the lower jaw usually unites with the internal maxil- 1 V. facialis; v. f. anterior, or interna; 8 V. massetericae et buccales. v. palato-labialis. 9 V. labiales. 2 V. angularis. 10 V. submentalis. 3 V. frontalis ; v. preparata. n V. submaxillares. 4 V. supra-orbitalis. 12 V. palatina. 5 V. palpebrales superiores. 13 V. temporalis ; v. facialis posterior ; 6 V. nasalis dorsalis et lateralis, pin- v. f externa ; v. carotis externa. nalis, or alaris. u V. temporalis superficialis anterior. 7 V. palpebrales inferiores. 15 V. t. s. posterior. THE VASCULAR SYSTEM. 415 lary vein to form the tempero-maxillary vein. In its course it receives the following branches : The Artic'ular veins, 1 from a plexus 2 behind the articulation of the lower jaw. The Anterior auric'ular veins, 3 from the front of the auricle or ear. The Middle temporal vein, 4 following the course of the artery of the same name. The Transverse fa'cial vein, 5 likewise following the corresponding artery. The Parot'id veins, 6 from the parotid gland. THE INTERNAL MAXILLARY YEIN. The Internal Max'illary vein 7 springs from a plexus which is situated between the pterygoid muscles, in contact with the maxillary artery, and receives the veins which accompany the latter. It is a short vessel which passes behind the neck of the lower jaw, and joins the temporal vein within the parotid gland, or it is represented by a pair of vessels, both joining the temporal vein, or one may join the latter and the other may descend to near the angle of the jaw, to end in the internal jugular vein. THE TEMPERO-MAXILLARY YEIN. The Tem/pero-max'illary vein, 8 formed by the conjunction of the temporal with the whole or part of the internal maxillary vein, descends, in company with the external carotid artery, through the parotid gland, and joins with the posterior auricular vein to form the external jugular vein. Sometimes it divides, partly to contribute in the formation of the latter, and partly to join with the facial vein to empty into the internal jugular vein ; and not unfrequently it entirely joins with the facial vein to terminate in the internal jugular. THE POSTERIOR AURICULAR YEIN. The Posterior Auric'ular vein, 9 pursuing the course of the corre- sponding artery, joins with the tempero-maxillary vein, in whole or part, 1 V. articulares. e y parotidese. 2 Plexus articularis posterior. t y. maxillaris interna ; deep branch 3 V. auriculares anteriores et v. auri- of the posterior facial vein. cularis profunda. s y, tempero maxillaris ; v. facialis 4 V. temporalis media or profunda. posterior. 5 V. transversa facei. V. jyiricularis posterior. 41G THE VASCULAR SYSTEM. to form the external jugular vein ; or, in those cases in which the former terminates in conjunction with the facial in the internal jugular vein, it is the sole origin of the external jugular. THE OCCIPITAL VEIN. The Occip'ital vein 1 follows the general course of the corresponding artery, and usually terminates in the internal jugular vein, but sometimes in the external jugular. A communication between it and the lateral sinus is established by means of the mastoid vein, which passes through a foramen of the temporal bone. THE VEINS OF THE TONGUE. The Dorsal Lin'gual vein 2 receives its branches from the upper part of the tongue, the tonsils, and epiglottis, and pursues the course of the lingual nerve, to end in the facial, pharyngeal, or either jugular vein. The Ranine vein 3 commences under the tip of the tongue, where it is visible through the mucous membrane, and passes back in the course of the hypoglossal nerve to terminate in the facial or either jugular vein. THE PHARYNGEAL VEIN. The Pharynge'al vein 4 is derived from a plexus on the sides and back of the pharynx, and descends to terminate on a level with the hyoid bone in the internal jugular vein. THE SUPERIOR THYROID VEINS. The Superior Thy'roid veins, 5 usually two in number, are derived from the upper part and side of the thyroid gland, and from the larynx and trachea, and terminate in the internal jugular vein, or occasionally in the lingual or facial vein. THE VEINS OF THE UPPER EXTREMITIES. The veins of the upper extremities consist of a deep and a superficial series, of which the former follow the arteries, while the latter pursue an independent course beneath the skin, but finally terminate in the main 1 V. occipitalis. 5 V. thyroidea superiores ; v. thyroidea 2 V. dorsalis linguae. superior et media et v. laryngea et v. 3 V. ranina. pharyngea inferior. 4 V. pharyngea. THE VASCULAR SYSTEM. 417 trunk of the deep veins. The two series have frequent anastomotic communications, and are provided with many valves, which are more numerous in the deep veins. THE SUBCLAYIAN VEIN. The Subcla'vian vein 1 is the continuation of the axillary vein, and usually receives at its commencement the external jugular vein. As it passes over the first rib it is separated from the subclavian artery by the insertion of the anterior scalene muscle. It is destitute of valves, and by conjunction with the internal jugular forms the innominate vein. THE DEEP VEINS OF THE UPPER EXTREMITY. The Deep Veins of the upper extremity closely follow the arteries, every one of these except the axillary artery possessing a pair o,f com- panion veins which anastomose with each other by occasional transverse offsets crossing the vessel they accompany. Of the two Bra'chial veins, the internal one is the larger, and usually- just above the middle of the arm it receives the basilic vein, which be- longs to the superficial set. In the axilla the two brachial veins unite to form the Ax'illary vein, and as this passes beneath the clavicle it re- ceives the cephalic vein of the superficial set, and finally becomes the subclavian vein. THE SUPERFICIAL VEINS OF THE UPPER EXTREMITY. The Superficial veins of the upper extremity are generally larger than the deep ones, and are not the companions of arteries. Through numerous anastomoses they form a net-work enveloping the limb beneath the skin. In fat persons they are inclosed in the adipose layer of the superficial fascia, but in thin persons, and under ordinary circumstances, are for the most part visible through the integument. They have fre- quent anastomotic communication with the deep veins, and finally term- inate in the main trunks of the latter. The TJl'nar cuta'neous veins, 2 usually two in number, occupy the front and back of the forearm. The posterior ulnar cutaneous vein 3 com- mences from the outer portion of the back of the hand, ascends along the ulnar border of the back of the forearm, communicating in its course with anastomotic branches of the radial cutaneous vein, and at the bend of the elbow assumes the name of basilic vein. The anterior ulnar 1 V. subclavia. 2 V. ulnares cutaneae ; v. ulnaris cutanea ; v. basilica. 3 V. ulnaris cutanea posterior ; v. salvatella. 27 418 THE VASCULAR SYSTEM. FIG. 273. cutaneous vein 1 commences in front of the wrist, ascends along the fore- arm, anastomosing in its course with the preceding, and either terminates by joining the posterior ulnar cuta- neous vein or the median vein. SUPERFICIAL VEINS OF THE UPPER EXTREMITY. 1, median vein; 2, 3, radial cutaneous veins; 4, 5, ul- nar cutaneous veins; 6, median-cephalic vein; 7, median-basilic vein ; 8, anastomosis with the deep veins; 9, cephalic vein ; 10, its further course seen through the brachial fascia; 11, 12, basilic vein. The Basil'ic vein 2 ascends from the posterior ulnar cutaneous vein along the inner border of the bi- ceps muscle, and perforates the brachial fascia, to join above the middle of the arm one of the bra- chial veins. The Radial cuta'neous veins commences from the radial side of the back of the hand, ascends along the outer border of the forearm, re- ceiving in its course many branches from the front and back of the latter, and at the bend of the elbow assumes the name of cephalic vein. Sometimes there are two radial cutaneous veins which either con- join near the bend of the elbow, or the anterior one joins the median vein. The Cephal'ic vein, 4 ascending from the former along the outer border of the biceps muscle, and then in the groove between the deltoid and great pectoral muscles, dips inwardly below the clavicle and terminates in the axillary vein. 1 V. ulnaris cutanea anterior. 2 V. basilica; v. cutanea cubitalis; cubiti interior. 3 V. radialis cutanea ; v. cephalica. * V. cephalica ; v. cutanea radialis r. capitis. THE VASCULAR SYSTEM. 419 The Me'dian veins 1 occupy the front of the forearm in the interval of the ulnar'and radial cutaneous veins, with which they freely anastomose. They are very variable in number, arrangement, and method of termina- tion. Frequently they collect into a parent stem 2 which forks at the bend of the arm one division, named the median-cephalic vein, 3 pro- ceeds obliquely upward and outward to join the cephalic vein, while the other, named the median-basiFic vein, 4 passes upward and inward to join the basilic vein. At other times the median vein or veins term- inate in an oblique vessel proceeding across the bend of the arm upward and inward from the radial cutaneous vein to the basilic vein. The middle of the oblique vessel or the angle of the forked median vein anas- tomoses at the bend of the arm with the brachial veins. The median-basilic vein or the inner portion of the oblique vessel is larger than the median-cephalic vein, and is usually chosen in the opera- tion of bleeding from the arm. It crosses the brachial artery, from which it is only separated by the offset from the tendon of the biceps muscle to the brachial fascia. Important branches of the internal cuta- neous nerve pass above and below it. THE AZYGOS VEIN. The Az'ygos vein 5 commences on the right side of the vertebral col- umn, in an anastomotic communication with the lumbar veins, the renal vein, or the inferior cava. Passing from the abdomen through the aortic orifice of the diaphragm, or through a distinct aperture in the right crus of the latter, it ascends on the dorsal vertebra and arches forward over the root of the right lung to terminate in the superior cava. To its ptgbfc are situated the thoracic duct, the aorta, and the oesophagus, and in its course it receives the following branches : The Right intercostal veins, Sometimes the upper two or three con- join in a trunk, which opens into the right innominate vein. The Oesophageal veins. The Right bronchial vein. The Hemi-az'ygos veins, of which there are two situated on the left side of the vertebral column. The inferior hemi-az'ygos vein 6 arises in the same manner as the azygos vein, and like it enters the thorax, when it ascends to about the middle of the dorsal vertebrae, and then 1 V. medianae ; v. mediana. 5 V. azygos ; v. azyga ; v. sine pari ; 2 V. mediana communis. v. pari careus ; v. prelombo-thoracica. 3 V. mediana cephalica. 6 v. hemi- azygos; v. hemi-azyga; v. 4 V. mediana basilica. azygos sinistra, or parva. 420 THE VASCULAR SYSTEM. crosses the column beneath the aorta to join the azygos vein. It re- ceives in its course the lower five or six left intercostal veins, The supe- rior hemi-az'ygos vein 1 is formed by the union of the upper left in- tercostal veins which do not join the former. It terminates in the left innominate, the inferior herni- azygos, or the azygos vein. THE INFERIOR CAY A. The Inferior cava, 2 the ascend- ing trunk of the venous system, collects the blood from the inferior extremities, pelvis, and abdomen. It commences by the confluence of the common iliac veins at the side of the fourth lumbar vertebra, as- cends upon the vertebral column to the right of the aorta, and passes through the quadrate foramen of the diaphragm to terminate in the right auricle of the heart. It is larger than the aorta or the supe- rior cava, and is possessed of no valves. Exclusive of the common iliac veins, in its course it receives a number of branches. BRANCHES OF THE INFERIOR CAYA. The Middle sacral vein 3 follows the course of the corresponding VEINS OF THE THORAX AND ABDOMEN, i, inferior artery, and opens into the com- cava; 2, right, 3 left renal veins; 4, superior cava; , . . 5, right 6 left innominate veins; 7, internal veins; mencement of the inferior Cava. 8, external jugular veins; 9, subclavian vein; 10, Sometimes it terminates in the left azygos vein; 11 inferior, 12 superior hemiazygos common iliac vein. i V. hemi-azygos superior ; superior intercostal vein; v. semi- or demi-azygos. 2 Cava inferior ; vena cava inferior, ascendens, or abdominalis ; v. hepatites. 3 V. sacralis media. THE VASCULAR SYSTEM. 421 The Lumbar veins 1 are three or four in number on each side, and follow the like-named arteries. They anastomose with one another, and with the common iliac, azygos, and hemi-azygos veins, thus forming a plexus. 2 The Spermatic veins 3 derive their blood from the testicles. Each originates in the spermatic plexus, 4 and follows the corresponding artery the right one to terminate in the inferior cava, the left one in the left renal vein. The Ova'rian veins, 5 of the female, originate in the ovarian plexus contained in the broad ligament, and follow the same course as the pre- ceding veins. The Re'nal veins 6 are short, capacious trunks, formed by the converg- ence of several branches emerging from the sinus of the kidneys. They are nearly transverse in their direction, and the left one is the longer, and crosses in front of the aorta to reach its destination. The Supra-renal veins 7 consist of several branches from the supra- renal bodies terminating in the inferior cava, the renal veins, and those succeeding. The Phren'ic veins 8 consist of two companions for each correspond- ing artery, and terminate in the inferior cava just below the following. The Hepat'ic veins 9 are two or three trunks which emerge from the posterior notch of the liver, and immediately terminate in the inferior cava, just as it enters the quadrate foramen of the diaphragm. THE PORTAL VEIN. The Portal vein 10 is a short, capacious trunk, about three inches in length, derived from the convergence of the veins of the stomach, the small and large intestines, the spleen, and the pancreas. It commences by the conjunction of the splenic and superior mesenteric veins behind the pancreas, and ascends in the right border of the lesser omentum to the transverse fissure of the liver, where it 11 divides into two principal branches, 1 V. lumbares. 8 V. phrenicse ; v. p. inferiores ; v. dia- 2 Plexus lumbaris et v. lumbaris ad- phragmaticae. scendens. 9 V. hepaticae ; v. cavae hepaticae ; v. 3 V. spermaticae ; v. s. internae. supra-hepaticae. 4 Plexus spermaticus ; p. pampinifor- 10 V. portalis, porta, portae, portarum, mis. or ad portas ; v. lactea ; v. arterialis ; v. 5 V. ovariae. ostiaria ; v. magna; manus jecoris or 6 V. renales; v. emulgentes. hepatis; ramalis vena; janitrix; portal 7 V. supra-renales ; v. capsulares ; v. system ; abdominal venous system ; sys- atrabiliariae. tern of the vena porta. 11 Sinus venae portarum. 422 THE VASCULAR SYSTEM. which diverge right and left to be distributed throughout the organ. The blood thus conveyed Fl 275 to the liver, together with that of the hepatic artery, is returned to the general system by means of the hepatic veins. The Splenic vein 1 is derived from branches cor- responding with those of the splenic artery, and pursues the same course as this until it joins the portal vein. The Superior mes'en- teric vein 2 pursues the same course as the like- named artery, and joins with the preceding vein to form the portal vein. The Cor'onary vein 3 of the stomach terminates either in the splenic vein or the portal vein. The Right Gastro- epip'loic vein 4 joins the superior mesenteric vein or the portal vein. The Cystic vein, 5 from the gall-bladder, joins the latter vessel. The Inferior Mes'enteric vein, 6 pursuing the course of the corre- sponding artery, terminates in the splenic or the superior mesenteric vein. The portal vein and its branches are destitute of valves. THE PORTAL SYSTEM OF VEixs. a, portal vein ; 6, splenic vein ; c, right gastro-epiploic vein; d, inferior mesenteric vein; e. supe- rior mesenteric vein ; f, trunk of the superior mesenteric artery. 1, liver ; 2, stomach ; 3, spleen ; 4, pancreas ; 5, duodenum ; 6, as- cending colon : the transverse colon is removed ; 7, small intestine ; 8, descending colon. 1 V. splenica ; v. lienalis. 2 V. mesenterica superior ; v. mesen- terica; v. m. magna. 3 V. coronaria ; v. gastrica superior. * V. gastro-epiploica dextra ; v. gastri- ca dextra inferior. 5 V. cystica. 6 V. mesenterica inferior ; v. m. minor ; v. colica sinistra. THE VASCULAR SYSTEM. 423 THE VEINS OF THE VERTEBRAL COLUMN. The Dorsi-spinal plexus 1 is a net-work of veins embracing the verte- bral arches and their processes posteriorly. It receives the veins from the muscles of the back, and communicates by frequent anastomoses with the intra-spinal plexus, the vertebral, intercostal, lumbar, and sacral veins, and the superficial veins of the back. The Intra-spinal plexus 2 is an intricate net-work of veins, situated within the spinal canal, between the dura mater and the vertebras. It is composed of four longitudinal veins, two in front and two behind, ex- tending the entire length of the spinal canal, and frequently communi- cating with one another by transverse veins. The anterior longitudinal veins 3 occupy the sides of the vertebral bodies and present a festooned appearance from their curving round the abutments of the vertebral arches. Opposite the vertebral bodies they are associated by transverse veins, which pass beneath the vertebral ligament and receive the diploic veins 4 from the interior of the vertebra. The posterior longitudinal veins, 5 smaller than the anterior, occupy the sides of the vertebral arches, and conjoin by transverse branches crossing the latter, and like- wise join the anterior longitudinal veins by lateral branches. The com- plexity of the intra-spinal plexus is increased by frequent division and reunion of both the longitudinal and transverse veins as they pursue their course. The intra-spinal plexus receives veins 6 from the spinal cord and its membranes, and communicates through the intervertebral foramina with the vertebral, intercostal, lumbar, and sacral veins, and with the occipital sinuses of the cranium. THE COMMON ILIAC VEINS. The Common Il'iac veins 7 are formed by the confluence of the inter- nal and external iliac veins opposite the sacro-iliac articulation. Con- 1 Venae dorsi-spinales ; plexus spinalis rieures, Breschet ; sinus columnae verte- posterior ; p. spinales extern! posteriores; bralis. plexus rachidian extern! posterieur, 4 Venae basi-vertebrales ; v. basis ver- Breschet. tebrarum. 2 Plexus spinalis internus ; p. spinales 5 V. longitudinales posteriores ; plexus interni ; p. s. i. anteriores et posteriores ; spinales interni posteriores ; posterior veines intra-rachidiennes fr. ; meningo- spinal veins ; veines longitudinales ra- rachidian veins. chidiennes posterieures, Breschet. 3 V. longitudinales anteriores ; sinus 6 Medulli-spinal veins ; v. medulli- longitudinales ; plexus longitudinales spinales. anteriores; great spinal veins; grandes 7 V. iliacae communes; v. i. primitivae. veines rachidieunes longitudinales ante- 424 THE VASCULAR SYSTEM. verging, they ascend and pass beneath the right common iliac artery, and to the right of the median line, on the last lumbar vertebra, unite to form the inferior cava. The right vein is shorter and more vertical in its ascent than the left ; and is at first behind the corresponding artery, and then gets to its outer side. The left vein is situated at the lower part of the inner side of its accompanying artery. Both are destitute of valves. THE INTERNAL ILIAC Y^IN. The Internal Il'iac vein 1 corresponds in its arrangement with the dis- tribution of the like-named artery, posteriorly to which it is situated, ascending on a line with the sacro-iliac articulation to terminate in the common iliac vein. It receives the double companion veins of the glu- teal, ilio-lumbar, lateral sacral, obturator, and ischiatic arteries, which generally conjoin with each other shortly before terminating in the main trunk. The ilio-lumbar veins anastomose with the lateral sacral and lumbar veins, and frequently terminate in the common iliac vein. The lateral sacral veins form with the middle ones a plexus, 2 which communicates with the haemorrhoidal plexus. The veins of the rectum, bladder, and organs of generation are ex- ceedingly numerous and large, and in several positions form very intri- cate and capacious plexuses. The Haemorrlioid'al plexus 3 embraces the rectum, and is especially well developed at the lower part of the latter, where it is the frequent seat of varicose enlargements, constituting haemorrhoids or piles. It communicates with the sacral and prostatic plexuses ; and veins 4 proceed from it to the inferior mesenteric vein, the internal iliac veins, and the pudic veins. The Prostat'ic plexus 5 is an intricate and capacious net-work of veins, embracing the membranous portion of the urethra, the neck of the bladder, the prostate body, and the seminal vesicles. It communicates freely with the vesical plexus, joins the ha3morrhoidal plexus, and termi- nates in the internal iliac and pudic veins. The U'tero-vag'inal plexus 6 corresponds in the female with the pre- ceding, and embraces the vagina and uterus. It communicates with the 1 V. iliaca interna ; v. hypogastrica. 5 P. prostaticus ; p. pudendalis ; part 2 Plexus sacralis. of vesico-prostatic plexus. 3 P. hsemorrhoidalis. 6 P. utero-vaginalis ; p. uterinus et p. * V. hsemorrhoidales sup. med. et inf. ; vaginalis. v. h. internae et externae. THE VASCULAR SYSTEM. 425 ovarian and the pudic veins, and, by means of the so-called uterine veins, 1 joins the internal iliac veins. During pregnancy, the veins of the uterine plexus become exceedingly enlarged, forming capacious sinuses, 2 but they do not pursue a tortuous course like the arteries. The Ves'ical plexus 3 embraces the bladder, but is especially well de- veloped at the fundus of the latter, where it joins the prostatic or vaginal plexus. From it proceed several vesical veins to terminate in the inter- nal iliac veins. The Pu'dic vein 4 pursues the course of the corresponding artery, and is formed of branches which accompany the deep arteries of the penis and those of the perineum. It communicates with the prostatic and hsemorrhoidal plexuses, and terminates in the internal iliac vein. It has a corresponding origin, in the female, from the clitoris and perineum, and communicates with the vaginal plexus. Larger veins than those which follow the deep arteries of the penis emerge from its erectile tissue to pursue a different course. Those from- the spongy body issue at the base of the glans and converge to form the Dorsal vein of the penis, 5 which runs along the dorsal groove of the organ beneath the arch of the pubis. After perforating the triangular ligament, it divides into two branches, which terminate in the prostatic plexus. The veins from the cavernous bodies emerge at the lower groove and turn round their outer side to join the dorsal vein. The Dorsal vein of the clitoris 6 has a corresponding origin and course as the preceding, and terminates in like manner in the vaginal plexus. THE EXTERNAL ILIAC VEINS. The External Il'iac vein 7 collects the blood from the lower extremity, and is the continuation of the femoral vein. Commencing beneath Pou- part's ligament at the inner side of the corresponding artery, it ascends behind the latter to join with the internal iliac in the formation of the common iliac vein. At its commencement it receives the double com- panion veins of the circumflex iliac and epigastric arteries. 1 V. uterinse. 4 V. pudica. a Uterine sinuses. 5 y. dorsalis penis. 3 P. vesicalis ; part of vesico-prostatic 6 V. dorsalis clitoridis. plexus. < V. iliaca externa. 426 THE VASCULAR SYSTEM. THE DEEP VEINS OF THE LOWER EXTREMITY. The Deep veins of the lower extremity pursue the exact course of the corresponding arteries ; every one of these, excepting the popliteal artery and its continuation the femoral having two companions which anastomose with each other across the vessel they accompany. The Poplite'al vein, 1 formed by the conjunction of the companion veins of the anterior and posterior tibial arteries, is situated behind the corresponding artery, and passes in company with it through the perfo- ration of the great adductor muscle to assume the name of femoral vein. The Fem'oral vein 2 at first lies behind its accompanying artery, but gradually inclines to the inner side during its ascent, and at Poupart's ligament assumes the name of external iliac vein. THE SUPERFICIAL VEINS OF THE LOWER EXTREMITY. The Superficial veins of the lower extremity have the general plexi- form arrangement, relation of position to the skin, and other characters indicated in the account of those of the upper extremity. Two princi- pal trunks, the saphenous veins, collect the blood of the superficial veins and empty it into the main trunk of the deep veins. The Short saphe'nous vein 3 proceeds from branches along the outer part of the back of the foot, passes behind the outer ankle, ascends the back of the leg, and dips between the heads of the gastrocnemius mus- cle to terminate in the popliteal vein. It collects the blood of the super- ficial veins of the outer part of the foot, and the outer and back part of the leg, and anastomoses freely with branches joining the succeeding vein. The Long saphe'nous vein, 4 more capacious than the other, springs from branches on the back and inner side of the foot. Passing in front of the inner ankle, it ascends along the tibia to the knee, where it inclines backward, and then ascends upon the thigh to the saphenous opening. Through this it dips to terminate in the femoral vein. It re- ceives the veins from the inner side of the foot, the greater number of those of the leg, all those of the thigh, the external pudic veins, and many of those of the abdomen. 1 V. poplitea. 4 V. s. longa; v. saphena interim; v. 2 V. femoralis ; v. cruralis. s. magna ; v. tibio-malleolaris ; great 3 V. saphena parva ; v. s. externa ; v. saphena vein ; internal saphenous vein, pereneo-malleolaris ; lesser saphena vein ; external saphenous vein. FIG. 276. THE VASCULAR SYSTEM. FIG. 277. 427 Fig. 276. SUPERFICIAL VEINS OF THE BACK OF THE LEG. 1, short saphenous vein ; 2, position at which it terminates in the popliteal vein; 3, long saphenous vein. Fig. 277. SUPERFICIAL VEINS OF THE INNER PART OF THE LOWER EXTREMITY. 1, long Saphe- notis vein ; 2, its termination at the saphenous opening into the femoral vein. 428 THE VASCULAR SYSTEM. THE PULMONAEY YEINS. The Pulmonary veins are four short venous trunks, of which two emerge from each lung and convey bright-red blood to the heart. The Right Pulmonary veins, longer than those of the left side, pass from the root of the right lung, below the corresponding pulmonary artery, behind the superior cava, the right auricle and the aorta, to term- inate in the left auricle. The Left Pulmonary veins pass from the left lung in front of the de- scending aorta, and likewise terminate in the left auricle. THE LYMPHATIC SYSTEM. The Lymphat'ic System 1 consists of vessels, gland-like bodies, and a contained liquid. The former are named lymphatic vessels or lym- phatics ; the gland-like bodies are called lymphatic glands, or, together with the vessels, are also named lymphatics. The contained liquid of both vessels and glands is the lymph. The intestinal lymphatics are more commonly known as the lacteals, and their contained liquid as the chyle. Lymphatic vessels 2 exist in mammals, birds, reptiles, and fishes, but are absent in the lower classes of animals. They are found in most tis- sues and organs which receive blood, but have not been detected in the substance of the brain and spinal cord, in the eyeball and labyrinth, nor the placenta and its membranes. The lymphatics are accessory to the sanguiferous system. From the various tissues and organs they collect a liquid which is apparently a transuded portion of the liquor sanguinis unappropriated by the tissues. In addition, they collect nutritive material derived from the food in the intestines. The liquids thus obtained are conveyed from smaller to larger vessels, traversing in their course the lymphatic glands, until finally they collect into two great trunks, the thoracic duct and the right lymphatic duct, which empty the lymph into the veins. The lymphatics consist of a deep and superficial set, the former follow- ing the course of the deeply-seated blood-vessels, and the latter running beneath the skin and the membranous envelopes of the organs in which they exist. The principal lymphatic vessels are more numerous than the arteries and veins, but are very much finer. They are long, thread-like, trans- 1 Absorbent system. 2 Absorbent vessels, or absorbents ; vasa lymphatica ; venae lymphatics ; vasa resorbentia; v. hydragoga; ductus serosi ; lymphae-ductus ; lymphangia; hydrangia. THE VASCULAR SYSTEM. 429 FIG. 278. parent tubes, of difficult detection unless some colored substance is in- jected into them. They are remarkable also for their great number of valves, which are constructed like those of the veins, and prevent a retro- grade course of the lymph. The valves are arranged in pairs at short distances apart, and the vessels behind them are dilated so that they pre- sent a beaded appearance when distended. The mode in which the lymphatics commence has been imperfectly ascertained in consequence of the extreme tenuity and transparency of the vessels and the impossibility of in- jecting colored liquids in a direction opposed to the opening of the many valves which occupy the larger branches. For the most part they appear to originate in close capillary nets, intercalated with the sanguifer- ous capillaries, but having no com- munication with them. In the villi of the intestines the capillary lym- phatics apparently commence as single club-like tubes with the ex- tremity closed. The lymphatic ca- pillaries are even larger than the sanguiferous capillaries, and like them are destitute of valves. Nearly all the principal lym- phatic vessels, in their course to the great trunks, pass through lym- phatic glands which occupy convenient positions in the various recesses and cavities of the body. As they approach near to the glands, they divide and subdivide before entering the latter, and in emerging at the opposite side many branches converge to form larger vessels. Those which enter are named afferent vessels, 1 and those which emerge are the efferent vessels, 2 and are fewer and larger than the former. In structure the lymphatic vessels resemble the- blood-vessels, more especially the veins. According to Kolliker, their external coat con- tains longitudinal bundles of muscular fibres. The Lymphatic glands 3 are moderately hard, pinkish bodies, varying in size from that of a hemp-seed to that of an almond, and are mostly LYMPHATIC CAPILLARY NET-WORK OF THE SKIN OP THE EAR. 1 Vasa afferentia ; v. inferentia. 2 Vasa efferentia. 3 Lymphatic ganglions ; conglobate, or globate glands ; glandulae lymphatic ; g. conglobatae. 430 THE VASCULAR SYSTEM. compressed spheroidal or ovoidal. They are generally situated along the course of the larger blood-vessels, and exist in considerable numbers within the thorax and abdomen, but likewise are found in the neck, the axilla, groin, bend of the elbow, and the popliteal space. The structure of the lymphatic glands has not yet been positively demonstrated. According to recent investigations, they appear to con- sist of a multitude of vesicles or pouches which communicate with one another, with the termination of the afferent vessels, and with the com- mencement of the efferent vessels. The vesicles occupy the interspaces of a stroma of connective tissue abundantly supplied with blood-vessels. In constitution the vesicles resemble those which form the solitary and agminated glands, and are suspected to be the source of the lymph cor- puscles. Lymph 1 possesses nearly the same physical and chemical properties as liquor sanguinis. After passing through the lymphatic glands it is found to have acquired numerous bodies, named lymph corpuscles. 2 These are faintly granular nucleated cells like the colorless corpuscles of the blood. They are also identical in character with the nucleated cells of the vesicular structure in the lymphatic glands, and are hence inferred to be derived from the latter. A few corpuscles of the same kind have been noticed in the intestinal lymphatic vessels before reaching the mes- enteric glands, and are suspected of originating in the solitary and agmi- nated glands. From the researches of Wharton Jones, published more than a dozen years ago, the lymph corpuscles ultimately undergo solution, and leave their nuclei transformed into blood disks. Though these researches ap- pear to be but little noticed, the opinion gains ground that the lymph corpuscles constantly poured into the blood are the source of its red corpuscles. Chyle 3 is the lymph of the intestinal canal modified by admixture of the absorbed nutritive liquid of the food. From the presence of innu- merable fat particles, it is commonly of a milk-white color, whence the name of lacteals, 4 given to the lymphatic vessels which convey it to the thoracic duct. THE TRUNKS OF THE LYMPHATIC SYSTEM. The lymphatic system has two main trunks, of which one is compara- tively long and large, and is named the thoracic duct, while the other is quite small, and is called the right lymphatic duct. iLympha; white blood. 4 Vasa chylifera ; chyliferous vessels; 2 Lymph globules ; white corpuscles. vasa lactea. 3 Chylus ; succus nutritius. THE VASCULAR SYSTEM. 431 THE THORACIC DUCT. VIEW OP THE GREAT LYMPHATIC TRUNKS. 1, 2, thoracic duct; 3, its termination at the angle of conjunction of the left internal jugular and sub- clavian veins; 4, the right lymphatic duct; 5, lymphatics of the thigh; 6, iliac lymphatics; 7, lumbar lymphatics ; 8, intercostal lymphatics, a, superior cava; b, left innominate vein; c, right in- nominate vein ; d, aorta; e, inferior cava; /, psoas muscle ; g, origin of the diaphragm. The Thorac'ic duct 1 commences in front of the second lumbar ver- tebra, between the aorta and infe- rior cava, through the union of the two lumbar lymphatic trunks with the intestinal lymphatic trunk ; the former being derived from the lym- phatics of the pelvis and lower ex- tremities, the latter from the vis- ceral lymphatics. The intestinal lymphatic trunk alone, or in conjunction with one or both of the lumbar lymphatic trunks, usually forms an oblong di- latation, called the Receptacle of the Chyle. 2 This dilatation is of variable size, but generally meas- ures from one to two inches in length, by the fourth of an inch in width After its origin, the thoracic duct passes through the aortic ori- fice of the diaphragm, and ascends in front of the vertebral column, between the aorta and azygos vein, and behind the oesophagus. From FIG. 279. 1 Ductus thoracicus; d. t. posterior; d. lymphaticus sinister ; d. rorifer ; d. ver- tebralis ; d. chyli ; d. chyliferus ; d. lac- teus ; d. Pecquetianus ; vena alba thora- cis Eustachii ; distributoria lactea thora- cica ; galaxia ; duct of Pecquet ; aliment- ary duct. 2 Receptaculum chyli ; r. Pecqueti ; cisterna Pecqueti ; c. chyli ; c. lumbaris ; sacculus lacteus, chyliferus, or rorifer; diversorium, stagnum, vesicula, or am- pulla chyli; utriculus lacteus; alveus ampullosus; chylocistis; chylodochium ; latices lactei ; reservoir of the chyle, or of Pecquet. 432 THE VASCULAR SYSTEM. the position of the fourth dorsal vertebra it inclines to the left side, passes behind the arch of the aorta, and ascends between the oesophagus and left subclavian artery, as high as the last vertebra of the neck. It then curves forward, outward, and downward, and terminates in the angle of union of the left subclavian and internal jugular veins, its orifice being protected by a pair of valves, which prevent the entrance of venous blood. At its commencement the thoracic duct is about the diameter of a goose-quill, but narrows in its ascent to about the middle of its course, when it widens again sometimes becoming in a marked degree dilated. It is not straight, but slightly tortuous ; and occasionally subdivides, again to reunite. It is provided with valves, more especially in the upper part of its course, but fewer than in lymphatic vessels generally. It receives all the lymphatics of the body below the diaphragm, those of the left side of the thorax, head, and neck, and those of the left upper extremity. THE RIGHT LYMPHATIC DUCT. The Right lymphatic duct 1 is about half an inch in length, and about a line in width ; and terminates, in a corresponding manner with the thoracic duct, on the right side of the body. It receives the lym- phatics of the right side of the head, neck, and thorax, and those of the right upper extremity. LYMPHATICS OF THE HEAD AND NECK. The lymphatic vessels of the head and neck from particular localities terminate in groups of glands, from which efferent vessels proceed to the next group of glands below, and so on until a few trunks are formed which terminate at the bottom of the neck in the thoracic duct and the right lymphatic duct. LYMPHATICS OF THE CRANIAL CAVITY. No lymphatic vessels have been detected in the brain, though they are numerous in the pia mater, in which they pursue the course of the prin- cipal veins, and emerge from the cranium through foramina giving pas- sage to arteries and veins. 1 Ductus lymphaticus dexter ; d. thoracicus dexter ; d. t. minor ; truncus lym- phaticus dexter. THE VASCULAR SYSTEM. 433 LYMPHATICS OP THE EXTERIOR OP THE CRANIUM. The occip'ital lymphatic vessels are derived from the back of the head, and terminate in the occip'ital and posterior auric'ular glands. 1 Of these there are four or five small ones situated in the Vicinity of the mastoid process on the sterno-mastoid and trapezius muscles. FIG. 280. LYMPHATICS OF THE HEAD AND NECK. 1, facial lymphatics; 2, temporal lymphatics; 3, posterior auric- ular and occipital lymphatics; 4, cervical lymphatics; 5, the right lymphatic duct; 6, internal jugular vein ; 7, sub lavian vein. The temporal lymphatic vessels are derived from the side of the 1 Glandulee occipitales, or cervicales, and g. auriculares posteriores, or subauricu- lares, or mastoideae. 28 t 434 THE VASCULAR SYSTEM. head, and terminate in the anterior auricular glands, 1 of which there are two or three situated on the parotid gland in front of the ear. LYMPHATICS OF THE FACE. The superficial fa'cial lymphat'ic vessels, derived from the forehead, eyelids, nose, lips, cheek, and chin, terminate in the submax'illary lym- phatic glands. 2 Of these there are six or more, situated upon the sub- maxillary salivary gland, from which they also receive lymphatic vessels. The deep fa'cial lymphat'ic vessels are derived from the temporal fossa, the orbit, the cavity of the nose, the palate, the side of the mouth, the upper part of the pharynx, the ear, and the cranial cavity. They terminate in from five to ten internal maxillary glands, 3 situated at the side of the pharynx, within the position of the parotid gland and the ramus of the lower jaw. The lingual lymphat'ic vessels follow the direction of the lingual arteries and veins, and traverse three or four glands 4 in their course. LYMPHATICS OF THE NECK. The superficial cer'vical lymphatic vessels, from the front and back of the neck, together with the efferent vessels of the occipital and poste- rior auricular lymphatic glands, and part of those from the anterior auricular and submaxillary lymphatic glands, terminate in the superficial cer'vical glands. 5 Of these there are five or six small ones situated at the upper part of the neck on the sterno-mastoid muscle, or at its poste- rior border. The deep cer'vical lymphatics 6 consist of a chain of twenty or more glands 7 pursuing the general course of the internal jugular vein and carotid artery. They communicate with the axillary lymphatics, and in their course receive efferent vessels from the anterior auricular and sub- maxillary lymphatic glands, those of the internal maxillary, lingual, and superficial cervical lymphatic glands, and the lymphatic vessels of the larynx, pharynx, thyroid gland, trachea, oesophagus, and muscles of the neck. The efferent vessels of the deep cervical lymphatic glands unite in the ju'gular lymphatic trunk, 8 which terminates on the corresponding side in the thoracic duct, or the right lymphatic duct. 1 G. auriculares anteriores ; g. faciales 5 G. cervicales superficiales ; plexus superficial ; g. zygomaticae. jugularis externus. 2 G. submaxillares. 6 Plexus jugularis internus. 3 G. maxillares internae ; g. faciales 7 G. c. profundse ; g. c. p. superiores profundae. and inferiores, or supra-claviculares. * G. linguales. 8 Truncus 1. jugularis. THE VASCULAR SYSTEM. 435 LYMPHATICS OF THE UPPER EXTREMITIES, AND OF THE EXTERIOR OF THE THORAX. The lymphatics of the upper extremity consist of a superficial and deep series, which pursue the general direction of the corresponding arterial and venous trunks. The principal superficial lymphatic vessels in ascending the upper extremity are directed to its inner side, most of them pursuing the course of the brachial and cephalic veins. In front of the internal condyle a few of them traverse a lymphatic gland; 1 and nearly all converge to enter the lower lymphatic glands of the axilla. Some of them accompanying the cephalic vein, together with, others from the shoulder, join the axillary lymphatic glands below the clavicle, or communicate with those of the neck. The deep lymphatic vessels of the upper extremity, following the direction of the arteries and their companion veins, after traversing three or more lymphatic glands 2 in the vicinity of the elbow, terminate in the axillary lymphatic glands. The superficial lymphatic vessels of the thorax commence beneath the skin of the upper part of the abdomen and breast. The deep vessels are derived from the mammary gland and the pectoral and neighboring muscles. Most of these lymphatics pass outward and upward to the axillary lymphatic glands, and a few of them terminate in the glands below the clavicle. The axillary glands, 3 which receive the lymphatic vessels of the upper extremity and exterior of the thorax, number from eight to a dozen, and are enveloped in the loose areolar tissue and fatty matter of the armpit. They extend from the lower part of the latter to the clavicle, and com- municate with the deep cervical lymphatic glands. Their efferent vessels, following the direction of the subclavian vein, unite in the subcla'vian lymphatic trunk,* which terminates in the thoracic duct, or the right lymphatic duct. LYMPHATICS OF THE CAVITY OF THE THORAX. The intercos'tal lymphatic vessels pursue the course of the corre- sponding veins, and are derived from the sides of the thorax and abdomen, the diaphragm, pleura, muscles of the back, and spinal canal. 1 G. cubitalis superficialis. G. axillares and g. infra-claviculares. 2 G. cubitales profundae and g. hume- * Truncus lymphaticus subclavius. rales. 436 THE VASCULAR SYSTEM. In the vicinity of the heads of the ribs they traverse fifteen or more intercostal glands, 1 the efferent vessels of which terminate for the most part in the thoracic duct. Between the intercostal lymphatic glands of the two sides, and com- municating with them, there are about a dozen posterior medias'tinal glands, 2 which receive lymphatic vessels from the diaphragm, pericardium, and oesophagus. Some of the efferent vessels of these glands terminate in the thoracic duct, while others join the bronchial lymphatic glands. The anterior medias'tinal lymphatic vessels 3 are derived from the front wall of the abdomen, the upper surface of the liver through the suspensory ligament, the front wall of the thorax, the diaphragm, pericar- dium, heart, and thymus gland. They traverse about twenty anterior medias'tinal glands, 4 situated in the course of the internal mammary blood-vessels, on the pericardium, and in front of the great blood-vessels emanating from the base of the heart. Their efferent vessels terminate in the thoracic and the right lymphatic ducts. The pulmonary lymphatic vessels consist of a superficial and deep series. The former arise from an intricate net-work beneath the pul- monary pleura, and are directed toward the root of the lung, where they meet the deep vessels. These pursue the ramifications of the pulmonary blood-vessels and bronchi, traversing in the terminal portion of their course a number of small pulmonary glands. 5 At the bifurcation of the trachea, on the bronchi, and at the root of the lungs, there are twenty or more bron'chial glands, 6 which receive the lymphatic vessels of the lungs and of the bronchi, and some of those of the trachea, oesophagus, and heart. These glands are comparatively large ; in infancy have the same color and consistence as those of other parts of the body, but in the pro- gress of life gradually assume a gray and finally a black color, arising from a deposit of fine particles of pigmentary matter. They also fre- quently become the seat of calcareous or tubercular deposits. Their efferent vessels on the left side terminate in the thoracic duct, but on the right side unite to form the broncho-medias'tinal trunk, 7 which ascends behind the innominate vein to join the right lymphatic duct. 1 G. intercostales. 5 G. pulmonicae. 2 G. mediastinae posteriores. 6 G. bronchiales and tracheales ; g. Ve- 3 Internal mammary lymphatic vessels. salianae. 4 G. mediastinae anteriores and g. ster- ' Truncus broncho-mediastinus. nales. THE VASCULAR SYSTEM. 437 LYMPHATICS OF THE LOWER EXTREMITIES AND OF THE PELVIS. The superficial lymphatic vessels originating on the back of the foot ascend in the course of the long saphenous vein to terminate in the superficial inguinal glands. Those originating from the sole of the foot accompany the short saphenous vein and partly join the former series ; while others terminate in the popliteal glands. The deep lymphatic vessels follow the course of the corresponding blood-vessels, traverse from two to four poplite'al glands 1 in their course, and finally join the deep inguinal glands. The superficial in'guinal glands, 2 from 'six to a dozen in number, are situated in the saphenous opening of the crural fascia and extend out- wardly in the groin. Besides receiving the superficial lymphatic vessels ascending from the lower extremity, they receive the superficial lym- phatic vessels of the lower part of the abdomen, the loins, and the but- tocks, and those of the integument of the penis and scrotum, or of the clitoris and labia in the female. The deep in'guinal glands, 3 of which there are two or three, are situ- ated upon the femoral blood-vessels. They receive the deep lymphatics of the lower extremity, and communicate with the superficial glands. The efferent vessels of the inguinal glands ascend beneath the femoral arch and enter a chain of six or more external iliac glands. 4 These are situated in the course of the corresponding blood-vessels, and further re- ceive lymphatic vessels from the front and side of the abdomen intern- ally. The lymphatic vessels of the perineum, of the penis or the clitoris, of the back portion of the scrotum or labia, of the bladder, of the prostate gland and seminal vesicles, or the vagina and uterus, of the muscles of the buttocks, and of the rectum, converge to a dozen or more internal il'iac glands. 5 These are situated at the side of the pelvis, about the corresponding blood-vessels, and communicate with the glands of the op- posite side in front of the sacrum, and with the external iliac glands. 1 G. poplitese. 5 G. iliacse internae, or hypogastricae, 2 G. inguinales superficiales. and g. sacrales ; plexus hypogastricus 3 G. inguinales profundce. and sacralis. 4 G. iliacae externse ; plexus iliacus externus. 438 THE VASCULAR SYSTEM. LYMPHATICS OF THE CAVITY OF THE ABDOMEN. The efferent vessels of the external and internal iliac glands become the afferent vessels of the lumbar glands. 1 Of these there are about twenty-five situated on each side of the vertebral column and great blood-vessels, upon the origin of the diaphragm, and upon the psoas and quadrate lumbar muscles. The glands of the opposite sides freely com- municate; and besides the vessels mentioned, they receive lymphatic vessels from the loins, the kidney and ureter, the supra-renal body, and the testicle or the ovary. The efferent vessels of the lumbar glands, on each side of the abdomen, conjoin to form the lumbar lymphatic trunk, 2 frequently represented by several smaller ones, terminating in the thoracic duct or the receptacle of the chyle. The lymphatic vessels of the stomach pursue the direction of its blood-vessels, traversing in their course a number of small glands. 3 Those from the lesser curvature and the right side of the greater curva- ture terminate in the mesenteric glands ; those from the left extremity join the splenic lymphatics. The lymphatic vessels of the small intestine are usually called the lac'teals, 4 from the fact of their conveying the chyle, which gives them the appearance of being filled with milk. From the intestine they pro- ceed between the layers of the mesentery, traversing in their course one hundred and thirty or more mesenteric glands. 5 These are irregularly arranged in three rows, of which the first contains the smallest glands but the greatest number, and the last the fewest and largest. Their efferent vessels terminate in the cceliac glands. The lymphatic vessels of the large intestine traverse about thirty mesocol'ic glands, 6 and terminate for the most part in the superior me- senteric glands ; those from the greater portion of the descending colon terminating in the left lumbar glands. The lymphatic vessels of the spleen and pancreas follow the direction of the splenic vein, traversing in their course a number of small glands, 7 and terminate in the cceliac glands. The lymphatic vessels of the upper surface of the liver, as before mentioned, for the most part ascend through the suspensory ligament to 1 G. lumbares ; plexus lumbaris. 4 Vasalactea; v. chylifera; chyliferous ' 2 Truncus lymphaticus lumbaris. vessels. 3 G. gastro-epiploicae superiores and 6 G. mesenteries or meseraicae inferiores. 6 G. mesocolicse. 7 G. splenico-pancreaticao. THE VASCULAR SYSTEM. 439 join the anterior mediastinal glands. Those of the lower surface and the deep vessels emerging from the transverse fissure of the liver, after traversing a few small glands, 1 associate with the lymphatics of the lesser curvature of the stomach, and terminate in the mesenteric glands. The cce'liac glands, 2 from fifteen to twenty in number, are situated behind the duodenum and pancreas, upon the aorta, the coeliac and superior mesenteric arteries, and the portal vein, and are intimately asso- ciated with the lumbar glands on each side. Their efferent vessels con- join to form the intestinal lymphatic trunk, 3 frequently represented by two or more smaller ones, terminating in the receptacle of the chyle. 1 G. hepaticse. 2 G. coeliacse; plexus coeliacus. 3 Truncus lymphaticus intestinalis, or abdominalis. CHAPTER VIII. THE VOCAL AND RESPIRATORY APPARATUS. THE LARYNX. THE Lar'ynx, 1 the organ of the voice, is situated at the top of the trachea, below the root of the tongue and the hyoid bone. At the period of puberty it becomes much larger in the male than the female, and in the former produces the conspicuous prominence in the middle of the neck, commonly known as " Adam's apple." 2 It is bounded behind by the pharynx, with which it communicates above, and it opens below into the trachea. In composition the larynx consists of a frame-work of cartilages con- nected by ligaments, provided with appropriate muscles, blood-vessels, and nerves, and lined with mucous membrane. CARTILAGES OF THE LARYNX. The Cartilages of the larynx consist of three symmetrical pieces, named the thyroid, cricoid, and epiglottic cartilages, and a pair called the arytenoid cartilages. The Thy'roid cartilage, 3 the largest of those of the larynx, is situated at the upper fore part of the latter, and consists of two lateral wing-like plates conjoined in front and diverging behind. In the male, after pu- berty, the line of union of the two plates forms an acute prominence above, and gradually recedes and becomes more obtuse below. In the female and young male it is less prominent above, and more uniformly rounded or obtuse. Each half of the thyroid cartilage is a quadrilateral plate, with the inner and outer surfaces sloping, and the borders rounded. The outer surface presents an oblique ridge for the attachment of muscles. The 1 Pars prima asperse arteriae ; caput, 2 Nodus gutturis ; promenentia laryn- operculum, initium, finis superior, or g ls - terminus superior asperse arterise. 3 Adami morsus os ; scutum ; cartila- go-scutiformis ; c. clypealis ; c. peltalis. (440) THE VOCAL AND RESPIRATORY APPARATUS. 441 FIG. 281. posterior angles are prolonged into blunt processes, named the horns, 1 of which the superior are the longer. The borders are sigmoid in their course; the upper one being so to the greatest degree, and meeting that of the opposite side in a deep notch in front of the thyroid cartilage. The Cri'coid cartilage, 2 situated below the former, and connected with the first ring of the trachea, in shape resembles a seal-ring. It is narrow in front, and gradually deepens poste- riorly. Its lower border, somewhat waving in its course, is horizontal. The upper border ascends from the front, and at the back part is provided with a pair of convex, oval promi- nences, which articulate with the arytenoid car- tilages. On each side externally of the cricoid carti- lage there is a slightly prominent circular facet for articulation with the inferior horns of the thyroid cartilage. The posterior surface is divided by a slight vertical ridge giving attach- ment to the oesophagus; and on each side of this ridge is a broad, shallow depression, accom- modating the posterior crico-arytenoid muscle. CARTILAGES OF THE LARYNX, front view. 1, thyroid cartilage; 2, its The Epiglottis 3 is a somewhat spoon-shaped plate of fibro-cartilage invested with mucous membrane, projecting above the aperture of the larynx, which is closed against it in the act of swallowing. In the ordinary condition of rest the cricoid cartilage ; e, its anterior it occupies an oblique position behind the body ^^^ ! 7 ' the tw aryte " of the hyoid bone, with its free extremity bent toward the root of the tongue. Its outline is ovoid, with the broader extremity free, and the narrower extremity prolonged and attached by a band of fibro-elastic tissue to the thyroid cartilage within the entering angle of its two halves. The free borders of the epiglottis are thin and slightly everted. The surface directed forward or toward the mouth is convex, and that toward the aperture of the larynx is concave. The Aryt'enoid. cartilages, 4 smaller than the others, are situated on 1 Cornua ; cornu longum, or superius and c. breve, or inferius ; greater and lesser cornu. 2 Cartilage cricoideus ; c. annularis ; c. cymbalaris; c. innominata. 3 Epiglottic cartilage ; operculum la- ryngis ; lingua exigua ; sublinguum ; lingula fistulse ; lingula ; superligula. 4 Cartilagines arytenoides; c. guttu- rales; c. triquetrse; c. pyramidales; gut- turnia. 442 THE VOCAL AND RESPIRATORY APPARATUS. the summit of the cricoid cartilage posteriorly. They are three sided, pyramidal, and curved. Their base is concave, and articulates with a corresponding prominence of the cricoid cartilage. Their apex is bent backward, and is surmounted with a nodule of cartilage 1 attached by means of a ligament. The posterior surface is concave, and accommo- dates the arytenoid muscles ; the anterior surface is convex, and has attached the thyro-arytenoid muscle ; and the inner surface is opposed to that of the opposite cartilage, leaving an intervening notch lined with mucous membrane. Of the three angles of the base of the arytenoid cartilages, the outer one 2 gives attachment to the crico-arytenoid muscles, and the anterior 3 is prolonged and gives attachment to the vocal membrane. A small piece of cartilage 4 frequently exists extending from the aryt- enoid cartilages upward into the aryteno-epiglottic folds. The cartilages of the larynx, as they are commonly named, are com- posed of true cartilage, except the epiglottis, which is fibro-cartilaginous. They are all invested with a perichondrium, and with the advance of life the true cartilages are strongly disposed to ossify. When the epi- glottis is stripped of its membranous investment, it is seen to present a corroded aspect arising from the existence of numerous irregular pits for the accommodation of small racemose glands. ARTICULATIONS AND LIGAMENTS OF THE LARYNX. The Thyro-hyoid membrane 5 is a rather loose fibre-elastic structure connecting the upper border of the thyroid cartilage with the inner sur- face of the hyoid bone. It is thickest and most dense in front, and is thin at the sides. The Thyro-hyoid ligaments 6 are cylindrical, fibro-elastic cords, join- ing the superior horns of the thyroid cartilage with the ends of the great horns of the hyoid bone. At their middle they usually contain -an im- bedded nodule of cartilage, 7 which is sometimes ossified. The Crico-thyroid articulation is formed on each side of the larynx, between the inferior horn of the thyroid cartilage and the side of the cricoid cartilage. It is lined with a synovial membrane, and surrounded 1 Corniculum laryngis; tuberculated, 4 Cuneiform cartilage; cartilage of or supra-arytenoid cartilage ; cartilage Wrisberg. of Santorini ; capitulum Santorini. 5 Middle thyro-hyoid ligament. 2 Processus muscularis. 6 Lateral thyro-hyoid ligaments. 3 Processus vocalis. 7 Cartilage tritlcea. THE VOCAL AND RESPIRATORY APPARATUS. 443 FIG. 282. by a capsular ligament. This joint permits a movement of the thyroid cartilage downward and forward, and in the reverse direction. The Crico-aryt'enoid articulation is a ball-and-socket joint, formed on each side of the larynx between the hollow base of the arytenoid car- tilage and a corresponding convexity of the cricoid cartilage. It is lined with synovial membrane, and surrounded by a capsular ligament. The joint allows movement of the arytenoid cartilage in all directions. The Thyro-epiglottic ligament 1 is a fibro-elastic band attaching the narrow extremity of the epiglottis to the upper part of the entering angle of the thyroid cartilage. The Vocal membrane, 2 composed of elastic tissue, springs from the front and sides of the upper border of the cricoid cartilage, and extends upward to the bases of the aryte- noid cartil-ages and the lower part of the entering angle of the thy- roid cartilage. Its inferior-portion is strongest, and is visible in the interval of the cricoid and thyroid cartilages at the front of the larynx. Its lateral portions are thin, and are separated from the sides of the thyroid cartilage by the interven- ing thyro -arytenoid muscles. Its upper margins, somewhat thickened, extend between the entering angle of the thyroid cartilage and the anterior prominent angle of the base of the arytenoid cartilages. These margins correspond in po- sition with the lower edge of the ventricles of the larynx, and are almost universally described as the "vocal cords," 3 which, as peculiar or separate organs, do not exist. MUSCLES OF THE LARYNX. The muscles of the larynx, except the arytenoid muscle, are in pairs, situated on each side of the larynx. 1 Lig. thyro-epiglotticum. 3 Chordae vocales; c. v. verse: c. Fer- 2 Membrana vocalis; phonetic mem- reinii ; superior thyro-arytenoid liga- brane; crico-thyroid membrane, or liga- ments; inferior ligaments of the larynx ; ment ; conoid, or pyramidal ligament. lips of the glottis. VIEW OF THE VOCAL MEMBRANE. 1, left half of the thyroid cartilage ; 2, right half turned forward aiid partly cut away; 3, cricoid cartilage; 4, arytenoid cartilages; 5, right half of the vocal membrane; 6, upper border of the left half; 7, arytenoid muscle. The upper borders of the vocal membrane, extended between the arytenoid cartilages and the thyroid, constitute the so-called " true vocal cords." 444 THE VOCAL AND RESPIRATORY APPARATUS. The Crico-thyroid muscle 1 arises from the front and side of the cri- coid cartilage, and ascends outward and backward to be inserted into the lower border of the thyroid cartilage. It draws the latter down- ward and forward, the centre of motion being the articulation between the inferior horn of the thyroid and the side of the cricoid cartilage. The result of the movement is to render the vocal membrane tense. FIG. 283. The Posterior Crico-aryt'enoid muscle 2 arises from the broad depres- sion at the side, posteri- orly of the cricoid carti- lage, and converges up- ^ \ ward and outward to be .inserted into the external angle of the base of the arytenoid cartilage. It rotates the latter on its base outward and back- ward, rendering the vocal membrane tense, and widening the glottis. The Lateral Crico- aryt'enoid muscle, 3 smaller than the preced- ing, is situated under cover of the side of the thyroid cartilage. It arises from the upper border, laterally of the two laminae of the aryteno-epiglottic fold separated so as to ex- cricoid Cartilage, and passes upward and back- ward to be inserted into the external angle of the base of the arytenoid car- tilage. It rotates the latter on its base outward and forward, relaxing the vocal membrane and widening the glottis. The Thyro-aryt'enoid muscle, 4 situated immediately above the pre- MUSCLES OF THE LARYNX. 1, right half of the thyroid cartilage, turned forward; 2, superior horns; 3, inferior horn marked by the crico-thyroid articulation ; 4, the other portion of the latter on the side of the cricoid cartilage ; 5, arytenoid cartilages, sur- mounted by nodules of the same substance; 6, epiglottis; 7, the pose the muscles ; 8, lower part of the vocal membrane ; 9, crico- thyroid muscle ; 10, posterior cricq-ary tenoid muscle ; 11, lateral crico-arytenoid ; 12, thyro-arytenoid ; 13,*thyro-epiglottic muscu- lar fibres ; 14, aryteno-epiglottic muscular fibres ; 15, arytenoid muscle. 1 M. crico-thyroideus; anterior dilator of the larynx. 2 M. crico-arytsenoideusposticus; pos- terior dilator of the larynx, 3 M. crico-arytomoideus lateralis. * M. thyro-arytenoidceus. THE VOCAL AND RESPIRATORY APPARATUS. 445 ceding, arises from the inner surface of the thyroid cartilage at its enter- ing angle, and from the contiguous portion of the vocal membrane, and passes backward to be inserted into the outer surface and base of the arytenoid cartilage. It draws the latter forward, and relaxes the vocal membrane. The Aryt/enoid muscle 1 consists of several transverse and obliquely crossing fasciculi, passing between the posterior concave faces of the arytenoid cartilages. It draws the latter together, and thus narrows the glottis. Besides the preceding well-characterized muscles, there exist some thin fleshy fasciculi which are not constant in extent or arrangement. Some of these diverge from the entering angle of the thyroid cartilage to the sides of the epiglottis, 2 while others pass from the latter to the sides of the arytenoid cartilages. 3 THE CAYITY OF THE LARYNX. The lining mucous membrane of the larynx is continuous with that of the pharynx and trachea. Extending from the root of the tongue to the epiglottis, it forms the three glosso-epiglot'tic folds. 4 Reflected from the sides of the epiglottis to the summits of the arytenoid cartilages, it forms the aryt'eno-epiglot'tic folds. 5 Dipping into a notch between the summits of the arytenoid cartilages, it extends from the front of these into the cavity of the larynx, and behind them into the pharynx toward the commencement of the oesophagus. The aperture of the larynx, 6 communicating with the pharynx, is tri- angular and oblique. Its base or wider portion above is formed by the epiglottis, its sides by the aryteno-epiglottic folds, and its apex or nar- row extremity by the notch separating the summits of the arytenoid cartilages. Descending from the aperture into the cavity of the larynx, the mu- cous membrane is reflected at each side, outward and upward, forming a pair of pouches named the ventricles of the larynx. 7 These are half 1 M. arytaenoideus ; m. arytaenoidei 5 Ligamenta epiglottideo-arytoenoidea. transversi and obliqui. 6 Superior aperture of the larynx ; 2 M. thyro-epiglottideus. aditus laryngis. 3 M. aryteno-epiglottideus ; compres- Ventriculi laryngis ; sacculi laryn- sor sacculi laryngis; m. ary-epiglotti- gis ; sinuses of the larynx; laryngeal dseus pouches; ventriculi Morgagni, or Ga- 4 Glosso-epiglottic freena ; ligamenta leni. glosso-epiglottica. 44(5 THE VOCAL AND RESPIRATORY APPARATUS. oval recesses communicating with the cavity of the larynx by a trans- verse elliptical orifice. The lower edge of the latter corresponds with FIG. 284 VERTICAL SECTION or THE FACE AND NECK, THROUGH THE MEDIAN LINE ANTERO-POSTERIORLY, EXPOSING TO VIEW THE NOSE, MOUTH, PHARYNX, AND LARYNX. 1, oval cartilage of the left nostril; 2, triangular cartilage; 3, line of separation between the two; 4, prolongation of the oval cartilage along the column of the nose; 5, superior meatus of the nose; 6, middle meatus; 7, inferior meatus; 8, sphenoidal sinus; 9, posterior part of the left nasal cavity, communicating with the pharynx; 10, orifice of the Eustachian tube; 11, upper extremity of the pharynx; 12, soft palate, ending below in the uvula; 13, interval of the mouth between the lips and jaws; 14, roof of. the mouth, or hard palate; 15, communication of the cavity of the mouth with the interval between the jaws and cheek ; 16, tongue ; 17, fibrous partition in the median line of the latter; 18, genio-glossal muscle; 19, genio-hyoid muscle; 20, mylo-hyoid muscle; 21, anterior half arch of the palate; 22, posterior half arch of the palate; 23, tonsil; 24, 25, floor of the fauces; 26, 27, pharynx; 28, cavity of the larynx; 29, ventricle of the larynx; 30, epiglottis; 31, hyoid bone; 32, 33, thyroid cartilage; 34, thyro-hyoid membrane; 35, 36, cricoid cartilage; 37, vocal membrane. the upper border of the vocal membrane, or with what are commonly termed, on the two sides together of the larynx, the vocal cords. 1 The upper edge of the orifice of the ventricles is rendered slightly prominent 1 Chordae vocales; c. v verae; ligamenta glottidis verae; 1. thyro-arytenoideoe in- feriora ; inferior, or true vocal cords ; lips of the glottis ; chordae Ferreinii. THE VOCAL AND RESPIRATORY APPARATUS 447 by an accumulation of the subjacent connective tissue, usually called, on the two sides of the larynx, the false vocal cords. 1 From the ventricles of the larynx, the mucous membrane extends downward, lining the vocal membrane and the cricoid cartilage, and be- coming continuous with that of the trachea. The cavity of the larynx gradually narrows from its aperture down- ward to the space between the inferior edges of the orifices of the laryn- geal ventricles. The narrowest portion of this space, named the glottis, 2 forms an isosceles triangle, of which the apex is at the entering angle of the thyroid cartilage ; the sides correspond with the edges of the vocal membrane, and the base is in relation with the arytenoid cartilages. Below the glottis the cavity of the larynx gradually widens and assumes the circular form of the interior of the cricoid cartilage. The mucous membrane of the larynx is soft, thin, and pale red. It adheres tightly to the epiglottis, the vocal membrane, and the interior of the cricoid cartilage, but in other positions is more loosely attached to the parts beneath by an abundant connective tissue. It is provided with numerous small racemose glands, and its epithelium is of the ciliated columnar form. Between the lower part of the epiglottis and the root of the tongue there is an abundant deposit of connective, elastic, and adipose tissue, and a similar deposit, with many racemose glands, is situated beneath the mucous membrane in front of the arytenoid cartilages. The arteries of the larynx are derived from the superior and inferior thyroid. The veins are branches of the thyroid veins. The lymphatics enter the cervical glands. The nerves are derived from the laryngeal branches of the pneumogastric and the sympathetic nerves. THE ORGANS OF RESPIRATION. The respiratory apparatus consists of the trachea and lungs, together with the thorax and appropriate muscles. The latter have already been described, and it now remains to examine the former. THE TRACHEA. The Tra'chea or Windpipe, 3 the main air-passage of the lungs, is a cylindrical tube descending the neck in front of the oesophagus into the Chordae vocales spurioe ; ligamenta 3 Aspera arteria; fistula pulmonalis, glottidis spuriae; 1. thyro-arytenoidese or spiritualis ; canna; syrinx; weasand; superiora ; superior, or false vocal cords. throttle ; bronchus. 2 Glottis vera ; rima glottidis ; fissure of the glottis ; true glottis ; ligula. 448 THE VOCAL AND KESPIRATORY APPARATUS. thorax. Commencing at the larynx opposite the fifth cervical vertebra, it terminates by dividing into the two bronchi opposite the third dorsal vertebra. Its length is about four inches ; its breadth, less in the female than the male, is from three-fourths to one inch. In the neck it is bounded on each side by the great blood-vessels ; and in the thorax is just behind the upper part of the sternum. FIG. 285. A. FRONT OF THE LARYNX, TRACHEA, AND BRONCHI. 1, hyoid bone ; 2, thyro-hyoid membrane ; 3, thy- roid cartilage; 4, lower part of the vocal membrane; 5, cricoid cartilage; 6, trachea ; 7, 8, two cartilag- inous rings ; 9, intervening fibro-elastic membrane connecting the rings ; 10, 11. right and left bronchi dividing into the bronchial tubes. B. BACK OF THE LARYNX, TRACHEA, AND BRONCHI. 1, aperture of the larynx ; 2, 3, spaces between the sides of the thyroid cartilage, and the cricoid and arytenoid lined with mucous membrane extending downward to the oesophagus ; 4, membranous space at the back of the trachea ; 5, muscular fibres passing across the space and exposed by removing a fibrous layer containing the tracheal glands ; 6, outer surface of the mucous membrane within the muscular layer; 7, 8, ends of the cartilaginous rings. The Bron'chi 1 diverge from the trachea to the lungs, behind the great blood-vessels emanating from the base of the heart. The right bron/- chus, 2 about an inch in length, passes nearly at a right angle to the root of the corresponding lung, on a level with the fourth dorsal vertebra, Bronchia ; bronchiae ; cannulae pulmonum. 2 Bronchus dexter. THE VOCAL AND RESPIRATORY APPARATUS. 449 and behind the right pulmonary artery. The left bron'chus, 1 narrower than the right, but about twice its length, passes downward and out- ward beneath the arch of the aorta to the root of the corresponding lung, on a level with the fifth dorsal vertebra and behind the left pulmo- nary artery. The trachea and bronchi are composed of a series of cartilaginous rings connected by a fibro-elastic membrane, and lined with mucous membrane.- The cartilaginous rings 2 encircle the trachea and bronchi, but are im- perfect at their posterior third. They are flat on their outer surface and convex on their inner surface, and therefore appear more prominent in the latter position. A strong fibro-elastic membrane connects their ad- jacent edges, and in a thinned condition extends over them. The poste- rior interval of the cartilaginous rings is occupied by a loose fibrous membrane and an internal layer of pale, unstriated muscular fibres having a transverse direction. The last of the cartilaginous rings of the trachea is modified in form so as to accommodate itself to the two first rings of the bronchi; its lower margin being prolonged in front to a median point, which is bent backward. The mucous membrane of the trachea and bronchi is pinkish white, and smooth, except that there are some fine longitudinal ridges at their posterior or membranous part, produced by reticular bundles of sub- mucous elastic tissue, which conspicuously occupy this position. The epithelium is of the ciliated columnar form ; the vibrating movement of the cilia during life being directed upward. The trachea and bronchi are provided with numerous minute racemose glands 3 which open upon the surface of the mucous membrane. The largest of these are imbedded in the posterior fibrous membrane ; and their terminal orifices are distinctly visible as numerous fine punctures on the free surface of the contiguous mucous membrane. Smaller glands occupy the intervals of the rings, and likewise distinctly exhibit their terminal orifices on the adjacent mucous membrane. The trachea and bronchi are supplied by the inferior thyroid and bronchial arteries ; their veins terminate in the thyroid and bronchial veins ; and their nerves are derived from the pneumogastric and sympa- thetic nerves. 1 Bronchus sinister. s Tracheal and bronchial glands ; glan- 2 Annuli cartilaginei ; segmenta card- dulse muciparae tracheales et bron- laginea ; orbes cartilaginosi. chiales. 29 450 THE VOCAL AND RESPIRATORY APPARATUS. THE LUNGS. The Lungs 1 occupy the cavity of the thorax on each side, separated by the heart and great blood-vessels. They accurately fill the spaces which contain them in the constantly changing capacity of the chest during res- piration. They are free or unattached everywhere except at their root, and are closely invested with a serous membrane, the pleura. FIG. 286. THE TRACHEA, LUNGS, AND HEART. 1, larynx ; 2, crico-thyroid muscle; 3, trachea; 4, 5, 6, upper, middle, and lower lotes of the right lung ; 7, 8, upper and lower lobes of the left lung ; the anterior part of both lungs is drawn aside by hooks so as to expose to view 9, the heart contained within its pericardium; 10, anterior mediastinal space, the line on each side indicating the position at which the pleuraa are reflected from the pericardium to the front wall of the thorax; 11, left subclavian artery; 12, left common carotid ; 13, right common carotid; 14, right subclavian; 15, left innominate vein; 16, right innominate vein ; 17, 18, left subclavian and internal jugular veins; 19,20, right internal jugular and subclavian veins; 21, root of the lung. The root 2 of each lung is situated near its middle internally, and consists of the corresponding bronchus, pulmonary artery and veins, the bronchial blood-vessels, nerves, and lymphatics, surrounded by a ipulmones; pulmo dexter and sinister ; pneumones; pjeumones; lights; spira- menta animae ; flabella et ventilabra cordis ; ergasteriones spiritu. 2 Radix, or pedunculus pulmonis. THE VOCAL AND RESPIRATORY APPARATUS. 451 reflection of the pleura. The root of the right lung is behind the su- perior cava, and has the azygos vein arching over it as this communi- cates with the former vessel. The root of the left lung lies partly beneath the arch and partly in front of the descending portion of the aorta. In the root of the right lung the bronchus is highest, the pulmonary artery is next, and the pulmonary veins are lowest. In the root of the left lung the pulmonary artery is highest, and then follows the bronchus, succeeded by the veins. Before entering a depression at the root of the lungs, named the hilus, 1 the bronchi subdivide : the right into three branches, the left into two, in correspondence with the number of lobes of each lung. The pulmo nary blood-vessels also commence subdivision before entering the lungs. Each lung is conical, with a broad, concave base resting on the dia- phragm ; a rounded apex extending above the level of the first rib into the neck; an outer convex surface ; and an inner concave surface directed toward the heart. The posterior border is long, thick, and convex, and occupies the side of the vertebral column ; the anterior border is thin and sharp, and folds around the heart included within its pericardium. The margin of the base is acute, and outwardly occupies the narrow angular interval between the origin of the diaphragm and the inferior border of the thorax. The lungs vary in weight and capacity according to many conditions, such as age, sex, size of the individual, state of health, and habit of ex- ercise. In the adult their approximate weight is about two and a half pounds, and their total capacity about three hundred cubic inches. Their long diameter is the greatest, and is deepest posteriorly. The right lung is shorter than the left, but wider, and of somewhat greater bulk. Each lung is divided by a fissure, commencing a short distance below the apex posteriorly and descending obliquely forward to the base ante- riorly. The right lung is further divided by a fissure proceeding from the first obliquely forward to its anterior margin. Thus the right lung has three lobes, 2 of which the middle one is the smallest and the lowest one is the largest ; the left lung has two lobes, 2 of which the lower is the larger. Between the lobes of the left lung in front there exists a large angular notch, corresponding with the position at which the im- pulse of the heart is felt against the walls of the chest during life. In infancy the lungs are of a pale-rose color; but as life advances they assume a pinkish-gray or more or less leaden hue, variegated with spots and streaks of a dark-slate or bluish-black color. This change is 1 Porta pulmonis. 2 Lobi, or aloe pulmonum. 452 THE VOCAL AND RESPIRATORY APPARATUS. due to the gradual deposition in the structure of the lungs of minute granules of a black pigmentary matter. The surface of the lungs is smooth and shining, and distinctly marked with polyhedral outlines, indicating a lobular constitution in these organs. The lungs are highly elastic, so that if the cavities containing them are opened, they collapse to about one-third of their previous bulk ; and they may again be readily inflated by artificial means. Their substance is of a sponge-like consistence, readily floats in water, and imparts a crackling sensation when compressed between the fingers. In the foetus before birth, or before respiration has taken place, they are heavier than water and sink in that fluid. A similar condition is observed in certain diseases, in which from congestion or effusion the lungs become more or less consolidated. On cutting a healthy lung and compressing it, a red- dish, frothy liquid exudes, consisting of mucus mingled with blood and air bubbles. The lungs are composed of numerous small, polyhedral primary lob- ules, 1 which unite into larger secondary lob- ules of the same general form. The latter give rise to the polyhedral markings on the surface of the lungs, and close inspection will lead to the discovery of the outlines of the primary lobules composing them. Both the primary and secondary lobules are associated by means of connective tissue ; 2 they are most distinctly observed in the young, but become less evident in advancing life. Every primary lobule of a lung represents in its structure the entire organ, and consists of a bronchial tube opening into an air-passage which communicates with a multitude of air-cells. FIG. 287. DIAGRAM OF TWO PRIMARY LOBULES OF THE LUXGS, magnified. 1, bron- chial tube ; 2, a pair of primary lobules connected by fibro-elastic tissue ; 3, intercellular air-passages; 4, air-cells ; 5, branches of the pul- monary artery and vein. The Air-cells, 3 the ultimate recesses of the lungs reached by the air in respiration, are rounded polyhedral sacs. They approach an average of about the one-tenth of a line in diameter, but vary much in size, being larger near the surface than in the deeper part of the lungs. They fur- ther increase in size with the advance of age ; and they become much enlarged in asthmatic persons. They communicate with a common, somewhat ramifying, inter-cellular air-passage, which ends in a bronchial 1 Lobuli, or insulse pulmonales. 2 Interlobular connective, or areolar tissue. 3 Cellulee, or vesiculee aerse ; cellulae terminales and parietales ; alveolae pul- monales; spiramina, or cellulae pulmo- num. THE VOCAL AND RESPIRATORY APPARATUS. 453 tube emanating from a primary lobule. They are connected together by an intervening fibro-elastic tissue, to which the elasticity of the lungs is mainly due; and they are composed of a basement membrane with a lining squamous epithelium. Exteriorly they are surrounded by fine nets of capillary blood-vessels, which intervene between the terminal branches of the pulmonary arteries and the commencing ones of the pul- monary veins. The Bron/chial tubes, 1 formed from the subdivision of the two bron- chi, ramify throughout the lungs without anastomosing, and finally end in the primary lobules, where they communicate with the intercellular air-passages. They have the same structure as the trachea and bronchi, except that their cartilages are subdivided into several pieces distributed around the tube instead of forming C-like rings; and their muscular fibres form a continuous layer. At the division of the bronchial tubes the cartilages assume a crescentic shape, and are so placed as to maintain the orifices of the tubes open. As the bronchial tubes become smaller, the cartilaginous element of structure decreases, and finally disappears, when they consist alone of fibro-elastic membrane with muscular fibres and a lining mucous membrane. The Pulmonary artery, specially devoted to the conveyance of dark blood from the heart to the lungs, ramifies in company with the bronchi and terminates in the capillary vascular nets inclosing the air-cells. The Pul'monary veins originate in the capillary nets just mentioned, and pursue the course of the bronchial tubes until they emerge from the lungs, when they convey the aerated, scarlet blood to the heart. The Bron/chial arteries, which are small vessels compared with the preceding, come off from the aorta, and follow the ramifications of the bronchial tubes, the tissues of which they chiefly supply. The Bron/chial veins, returning most of the blood of the correspond- ing arteries, terminate in the azygos vein on the right, and the superior hemiazygos vein on the left side. The lymphatics of the lungs are numerous. The superficial ones con- verge toward the root ; the deep ones follow the course of the bronchial tubes; and both enter numerous lymphatic glands situated about the bronchi and bifurcation of the trachea. These bronchial glands in early life do not differ in appearance from those elsewhere, but in the advance of age they assume a darker color than the lungs, and not unfrequently are found to contain calcareous deposits. The nerves of the lungs are derived from the pneumogastric with 1 Bronchi; syringes, or canales aeriferi. 454 THE VOCAL AND RESPIRATORY APPARATUS. branches of the sympathetic. These nerves form the anterior and pos- terior pulmonary plexuses, of which the latter is the larger, and both follow the course of the bronchi and pulmonary blood-vessels in their ramifications. THE PLEURA. The Pleu'ra 1 is a serous membrane which lines the sides of the cavity of the thorax, and is thence reflected from the root over the correspond- ing lung. It closely adheres to the subjacent structures, and in its differ- ent positions receives the names of costal, diaphragmatic, 2 medias'tinal, and pulmonary pleura. From the root of the lung a fold of the mem- brane extends downward to the diaphragm, and is called the pulmonary ligament. 3 The cavity of the pleura is bathed with a thin serous secre- tion which lubricates the surface of the lungs, and thus facilitates their movements during respiration. By the approximation of the two pleura? in the median line, they form the mediasti'num, 4 or partition of the thorax, which contains the heart included within its pericardium. The intervals between the two pleura? in front of, behind, above, and that occupied by the heart, are named from their relative position the anterior, posterior, superior, and middle mediastinal cavities. Above the middle of the sternum, for a short distance, the two pleuraa come into contact and are associated by connective tissue. The Anterior medias'tinal cavity 5 is bounded in front by the sternum, on each side by the pleura, and is occupied by some loose areolar tissue. The Posterior medias'tinal cavity 6 is bounded behind by the verte- bral column, on each side by the pleura, and in front by the pericardium. It contains the aorta, the azygos and hemiazygos veins, the thoracic duct, the oesophagus, and the pneumogastric and splanchnic nerves. The Superior medias'tinal cavity 7 is bounded on each side by the apex of the pleura, behind by the vertebral column, and in front by the 1 Pleurum; pleuroma; membrana diaphratton ; intersepimentum thoracis; pleuritica succingens ; m. p. costas sue- hymen diaphratton ; diribitorium. cingens; m. costalis, or subcostalis ; hy- 5 Anterior mediastinum ; cavum medi- popleurios. astini anterius ; mediastinum pectorale. 2 Phrenic. 6 Posterior mediastinum ; m. dorsale ; 3 Ligamentum pulmonale. cavum mediastini posterius. 4 Medianum; mesodne; mesotoechium ; 7 Superior mediastinum; cavum medi- septum, or dissipimentum thoracis ; astini superius. membrana thoracem intersepiens ; m. JHW THE VOCAL AND RESPIRATORY APPARATUS. 455 sternum. It contains the bifurcation of the trachea, the oasophagus, and great blood-vessels connected with the base of the heart. The Middle medias'tinal cavity 1 is occupied by the heart within its pericardium. THE THYROID BODY. The Thy'roid body 2 is a moderately soft, reddish organ, of unknown function, embracing the front and sides of the upper extremity of the trachea, and extending to the sides of the larynx. It consists of a pair of lateral lobes united at their lower part by a transverse isthmus. Its outer surface is convex, and its inner surface in contact with the trachea and larynx is concave. It adheres to the adjacent parts by connective tissue, and is covered by the sterno-hyoid, sterno-thyroid, and omo-hyoid muscles, and is in relation at its posterior borders with the great blood- vessels of the neck. The lateral lobes 3 are oblong oval, thicker below than above, and usually of unequal length. They commonly measure about two inches long, and extend from the sixth cartilaginous ring of the trachea to the lower part of the thyroid carti- lage. From the isthmus associating the lobes, a process 4 of the body fre- quently extends upward to the hyoid bone, to which it is attached by a fibrous band, occasionally con- taining some muscular fibres. 5 The weight of the thy- roid body is ordinarily from one to two ounces, but is larger in the fe- male. It is very liable to enlargement, especially in the latter sex, con- stituting the affection called goitre. The thyroid body is a highly vascular organ, invested with a thin, fib- FIG. 288. PORTION OF THE THYROID BODY IN SECTION, highly magnified, a. fibrous stroma; b, vesicles; c, the epithelium and liquid contents. 1 Middle mediastinum ; cavum medi- astini medius. 2 Corpus thyreoideum ; glandula thy- reoidea ; ganglion vasculosum. 3 Cornua lateralia. 4 Cornu medium ; processus pyramid- alis. 5 Levator glandulse thyreoideae. 456 THE VOCAL AND RESPIRATORY APPARATUS. rous membrane, 1 and composed of a fibrous stroma, in the meshes of which a multitude of minute, closed vesicles are imbedded. The vesicles- consist of a basement membrane 3 lined with an epithelium consisting of a single layer of nucleated cells ; and they are filled with a viscid amber- colored liquid. The arteries and veins of the thyroid body are branches of the superior and inferior thyroids. The lymphatics are numerous, and communicate with the cervical glands. The nerves are derived from the pneumogastric and great sympathetic. THE THYMUS BODY. The Thy'mus body 4 is a temporary organ of unknown function, which increases in size from the embryonic period up to two years a/ter birth, and subsequently dwindles away. It occupies the upper part of the FIG. 289. FIG. 290. ONE LOBE OF THE THYMUS BODY, WITH ITS CAVITY LAID OPEN, AND EXHIBITING THE LOBULAH RECESSES. The lower extremity of the figure exhibits the out- lines of the lobules. SECTION OF A LOBULE OF THE THYMUS BODY, magni- fied, a, fibrous investment of the lobule ; 6, acini penetrated by blood-vessels ; c, the lobular recess. anterior mediastinal cavity behind the sternum, and extends into the neck, frequently to the thyroid gland. It rests upon the pericardium, aorta, left innominate vein, and the trachea. It is a flat triangular body 1 Tunica propria. 2 Gland vesicles. 3 Membrana propria. 4 Corpus thymicum ; thymus gland : glandula thymus ; thymus ; corpus in- comprehensibile; the sweetbread. THE VOCAL AND RESPIRATORY APPARATUS. 457 consisting of a pair of lateral and usually unequal lobes. It is of a pinkish cream color, and varies in size and weight, not only according to age, but also in different individuals of the same age. At birth it is commonly about two inches long, one and a half inches wide at the lower part, and two or three lines thick, and its weight is about half an ounce. The thymus body is provided with a thin investing fibrous membrane, and is composed of numerous compressed angular lobules, associated by connective tissue, which give it the aspect of a racemose gland. Each lateral lobe commonly exhibits an interior cavity 1 of variable extent, communicating with recesses in the lobules. Further than this, the structure of the thymus body has not been satisfactorily determined. The thick walls of the lobular recesses appear to consist of acini 2 or coarse granules, comparable to the vesicles of the thyroid body or those of racemose- glands. The acini are composed of free nuclei and nu- cleated cells, and are penetrated by blood-vessels. The recesses of the lobules and the cavities of the lobes are filled with a thick milk- like liquid, mingled with numerous nuclei and nucleated cells. The arteries 3 of the thymus body are derived from the internal mam- mary, pericardiac, and inferior thyroid arteries. The veins empty into the left innominate vein. The lymphatic vessels terminate in the inter- nal mammary lymphatics. The nerves are derived from the pneumogas- trics and great sympathetics. 1 Reservoir of the thymus. 2 Incorrectly called cells, or vesicles. 3 Thymic arteries. CHAPTER IX. THE URINARY ORGANS. THE urinary organs consist of the kidneys, which secrete the urine ; the ureters or excretory ducts of the former ; the bladder, a receptacle for the urine ; and the urethra, the canal through which the latter liquid is discharged. THE KIDNEYS. The Kidneys 1 are two glandular organs, deeply situated in the lumbar regions, lying one on each side of the vertebral column ; the right a little higher than the left. They are opposite the upper two or three lumbar and the last dorsal vertebra, inclining toward each other above, and are maintained in this position by their vessels, together with a quantity of loose areolar tissue usually containing much fat. 2 Their anterior surface is more convex than the posterior, and their upper ex- tremity is larger than the lower, and has attached to it the supra-renal body. The right kidney in front is in contact with the liver, the descending portion of the duodenum, and the ascending colon ; the left with the spleen, pancreas, stomach, and descending colon. The kidneys are smooth, dark red, compressed oval bodies with a notch on the inner side ; the form being so characteristic that similar shaped bodies are commonly called kidney-shaped or reniform. They vary in size, but ordinarily measure about four inches in length, two inches in breadth, and one inch in thickness, and weigh about four ounces. The notch on the inner side of the kidneys is named the hilus, 3 and communicates with an interior cavity, the sinus, at which the vessels, nerves, and excretory duct of the organs have their entrance and exit. Besides the general envelope of areolar tissue and fat, the kidneys are furnished with a special fibrous coat. 4 This is a thin, moderately firm, 1 Renes. Singular : ren ; nephros ; 3 Porta renis. protmesis. 4 Tunica propria ; capsula fibrosa. 2 Tunica, or capsula adiposa. (458) THE URINARY ORGANS. 459 FIG. 291. uniform layer of fibrous tissue adhering slightly to the glandular struc- ture beneath. It extends from the hilus into the sinus, and at the bot- tom of this cavity becomes continuous with the fibrous investment of the vessels and duct of the organs. Upon dividing a kidney in its breadth longitudinally, the cut surface is observed apparently to consist of two substances : an exterior more granular looking portion, named from its relative position the cortical sub- stance, 1 and an interior striated portion, called the med'ullary sub- stance, 2 The latter is arranged into conical masses, the renal pyra- mids, 3 the bases of which are enveloped in the cor- tical substance, 4 while the free summits, named renal papillae, 5 project into the sinus of the kidney. The renal pyramids 3 vary in size and number there usually being from ten to fifteen and some- times a pair of them are confluent. They are ar- ranged in three irregular series, with their bases directed exteriorly and their summits converging toward the sinus of the kidney. Together with the enveloping cortical substance at their base, they correspond with so many lobules which are attached by connective tissue in the foetus, but subsequently become in- dissolubly blended. In many of the lower animals the lobules remain permanently and distinctly separated ; and not unfrequently the surface of the adult human kidney presents more or less distinct traces of the original lobular isolation. LONGITUDINAL SECTION OF A KIDNEY. 1, cortical substance; 2, re- nal pyramid ; 3, renal papillae ; 4, pelvis ; 5, ureter ; 6, renal ar- tery; 7, renal vein; 8, branches of the latter vessels in the sinus of the kidney. 1 Substantia corticalis vasculosa, glan- dulosa, or glomerulosa ; glandular, se- cerning, or vascular substance. 2 Substantia medullaris, tubulosa, fibrosa, or radiata ; uriniferous, or co- noidal substance. 3 Pyramids of Malpighi. 4 The cortical substance projecting be- tween the bases of the renal pyramids forms the columnae, or septa Bertini. 5 Papillas, or mammillae renales. 460 THE URINARY ORGANS. FIG. 292. The substance 1 of the kidney is mainly composed of secretory tubes, named urin/iferous tubules, 2 and blood-vessels, associated with com- paratively little connective tissue. The terminal orifices of the urinifer- ous tubules may be observed, to the number of several hundred, at the summit of each renal papilla. Tracing the tubules from their terminal orifices backward, they are found to pursue a nearly straight but slightly divergent course in the renal pyra- mids, dividing repeatedly at acute angles, and diminishing in size. Approaching the bases of the pyra- mids, they assume a slightly tor- tuous course, subsequently become much convoluted, and finally cease in the cortical substance, each in a pouch-like dilatation, inclosing a renal glom'erule (Malpighian cor- puscle.) The straight course of the urin- iferous tubules in the renal pyra- mids, and their subsequent convo- luted course, give rise to the differ- ence of appearance in the renal substance distinguished as the me- dullary and cortical portions. The uriniferous tubules are composed of a delicate wall of basement mem- brane lined with a pavement epi- thelium, and at their pouch-like extremity the wall is inflected upon the inclosed renal glomerule. The kidneys are very vascular, and obtain their blood through the renal arteries, which are large in proportion with the organs they supply. Approaching the hilus of a kidney, the renal artery divides into several branches, which subdivide, enter the sinus, and penetrate DIAGRAM OF THE STRUCTURE OF THE KIDNEYS. 1, two uriniferous tubules of the cortical substance lined with a pavement epithelium; 2, dilatation of a tubule inclosing a renal glomerule ; 3, branch of the renal artery ending in vessels which enter the glomerules as seen at 4, 5 ; 6, knot of blood-vessels freed from its investment; 7, veins emerging from the vascular knots ; 8, plexus formed by the latter veins among the uriniferous tubules, from which plexus originate the branches of the renal vein. 1 Secreting parenchyma. 2 Tubuli uriniferi ; uriniferous canals. Those of the medullary substance are named tubuli recti, or Belliniani, or ducts of Bellini. The bundles formed by the divisions of these tubes are called the pyramides Ferreinii. The urinifer- ous tubules of the cortical substance are the tubuli contorti, corticales, or Ferre- inii. THE URINARY ORGANS. 461 the renal substance between the renal papillae. Ramifying through the cortical substance, they finally terminate by forming most remarkable plexuses, named the renal glom/erules. 1 Each glomerule is a spheroidal knot of about T Jo of an inch in diameter, consisting of an intricate and close convolution of capillary vessels, inclosed by the pouch-like dilata- tion of a uriniferous tubule. From each glomerule there emerges an efferent vessel, which, together with others, forms a capillary net-work between and along the course of the uriniferous tubules. From this capillary net-work the renal veins originate and converge from the ex- terior surface of the kidney toward the base of the renal pyramids ; then pursue the course of the arteries and emerge into the sinus of the kidney, from which they make their exit in a single trunk. The excretory duct of the kidney, called the ure'ter, appears at the hilus as a compressed funnel-shaped pouch, named the pelvis. 2 Within the sinus, the wide mouth of the pelvis divides into two or three por- tions, which subdivide into several smaller funnels, or cal'yces. 3 Into each cal'yx one or two renal papillae project, so that the urine dribbling from the orifices of the uriniferous tubules is received by the calyces, conveyed to the pelvis, and thence runs down the ureter. The cal'yces, pelvis, and ure'ter have the same structure, consisting of an exterior fibrous layer, a succeeding stratum of unstriated muscular fibres, and a lining mucous membrane. The fibrous layer of the calyces at the base of the renal papilla becomes continuous with the fibrous investment of the sinus of the kidney. The muscular layer thins away from the pelvis, and ceases at the base of the renal papillae, while the mucous membrane is reflected upon the latter and becomes continuous with the uriniferous tubules at their orifices. In the hilus and sinus of the kidney, the pelvis is posterior to the position of the renal blood-vessels. The renal vein is in advance of the corresponding artery at the hilus, but within the sinus their branches intermingle. The nerves of the kidney are derived from the renal plexus of the sympathetic system ; the lymphatics communicate with the lumbar glands. The Ure'ter 4 is a cylindrical tube from each kidney, which conveys the 1 Glomeruli renales ; corpuscula Mai- 3 Infundibula ; calyces renales minores pighii ; corpora Malpighiana; Malpi- et majores; canales, or cylindri mem- ghian bodies or corpurcles ; glandules, branacei renum ; tubuli pelvis renum ; glomerules, or acini of Malpighi. fistulae ureterum renum. 2 Pelvis renalis; sinus, venter, or 4 Ductus urinse ; vas urinarium; ura- alvus renum. na : canalis nerveus fistulosus renum ; vena alba renum. 462 THE URINARY ORGANS. urine to a common receptacle, the bladder. It measures from fifteen to eighteen inches long, and is about the diameter of a goose-quill. De- scending obliquely inward, it enters the pelvic cavity and curves forward and downward to the fundus of the bladder, into which it opens. In its course it lies behind the peritoneum, loosely attached to contiguous parts by areolar tissue, and is crossed in front by the spermatic vessels. First resting on the psoas muscle, it then crosses the iliac blood-vessels, and is afterwards included by the recto-vesical or recto-uterine fold of the peritoneum, according to the sex. Approaching the bladder, in the male it crosses to the outer side of the spermatic duct, in the female runs along the side of the neck of the uterus, and terminates, after penetrat- ing the wall of the bladder obliquely, about one and a half inches be- hind the orifice of the urethra, and about the same distance from its fellow. The fibrous coat of the ureter is strong, and pinkish white in color. The muscular coat, consisting of pale, unstriated, longitudinal and trans- verse fibres, slightly thickens in its descent. The mucous membrane is without glands, and is provided with an epithelium whose cells exhibit a remarkable variety in form and size. The arteries of the pelvis and ureter are small branches derived from the renal, spermatic, and vesical arteries. The nerves are derived from the sympathetic system. The ll'rine, secreted by the kidneys and accumulated in the bladder, is a transparent, amber-colored liquid, highly complex in its chemical com- position. Its most characteristic constituent is a peculiar nitrogenized principle called u'rea. THE URINARY BLADDER. The U'rinary Bladder 1 is a musculo-membranous sac which serves as a reservoir to the urine as it is excreted by the kidneys. Its size and form vary with its condition of distention or collapse. When empty, it lies in the pelvic cavity, appearing as a flattened, triangular body, with the apex extending upward behind the pubic symphysis. When moder- ately distended, it assumes a rounded form, and still occupies the pelvic cavity ; but when completely filled, it becomes ovoidal, and its summit ex- tends above the pubes into the pre-peritoneal space of the hypogastric region. Its long diameter is directed from the latter downward and backward toward the anus ; but from its summit to its termination in the urethra its axis is somewhat curved. 1 Vesica urinaria; bladder; urocystis; cystis. THE URINARY ORGANS. 463 In the female the bladder approaches a more spheroidal form than in the male, and in both sexes its capacity is about equal to one pint. The upper extremity or summit 1 of the bladder is connected with a fibrous cord ascending behind the linea alba to the umbilicus. This cord is an obliterated tube, the urachus, which in the embryo extends between the bladder and a pouch, named the allantois, situated exteriorly to the abdomen. The base or fundus 2 of the bladder is the widest part of the organ, and is in contact, in the male, with the lower end of the rectum ; in the female, with the vagina. The portion of the bladder intervening to the fundus and summit is the body, and is more convex in front than behind. In advance of the fundus, the bladder is narrowed in a funnel-like manner, and is named the neck. 3 In the male this is nearly horizontal, the fundus extending slightly below its level; but in the female the neck descends obliquely forward and is the lowest part of the organ. The bladder is maintained in position by reflections of the peritoneum and recto-vesical fascia, by connective tissue attaching its front and fun- dus to the contiguous organs, by the obliterated umbilical arteries and urachus, and by the neck becoming continuous with the urethra. The recto-vesical fascia passing from the back of the pubis to the prostate gland and neck of the bladder forms two small processes, named the anterior ligaments of the bladder. A continuation of these to the sides of the fundus, reflected from the inner surface of the anal elevator muscles, constitutes the lateral ligaments of the bladder, The so-called false ligaments of the bladder are folds of peritoneum produced in its reflection upon this viscus. The recto'vesical folds 4 pass from the sides of the rectum to the sides of the bladder ; or instead of them, in the female, the utero-vesical folds pass from the sides of the uterus to the sides of the bladder. These folds contain the ureters, ves- sels and nerves of the bladder, and the commencement of the obliterated umbilical arteries. A slight fold is also produced by the subsequent course of the latter together with the urachus, toward the umbilicus. The peritoneum is reflected from the rectum or uterus to the back, the sides, and the summit of the bladder, and thence to the sides of the pel- vis 5 and the anterior parietes of the abdomen. Where destitute of peri- toneum, the bladder is invested with a thin, feeble layer of fibrous tissue, 1 Superior fundus. 5 The reflections to the side of the pel- 2 Inferior fundus ; bas-fond. vis constitute the lateral false ligaments 3 Cervix. of the bladder. 4 Plicae semilunares. 464 THE URINARY ORGANS. constituting a portion of the recto-vesical fascia and continuous with the subserous connection of the former. When the bladder becomes dis- tended, its summit elevates the peritoneum from the abdominal wall in the hypogastric region, so that the organ, in an operation, may be reached above the pubis without interfering with the latter membrane. Succeeding the peritoneum and vesical fascia, the bladder possesses a strong muscular coat, consisting of reddish-brown unstriated fibres which are collected into various sized fasciculi conjoining in a reticular manner, and are arranged in two different directions. The external longitudinal fibres diverge from the neck and anterior ligaments of the bladder, and again converge to its summit about the attachment of the urachus. The internal circular fibres are less numerous than the former, are transverse and oblique ; and at the neck of the bladder accumulate in a dense bundle, constituting the vesical sphincter, 1 Succeeding the muscular coat, and adhering closely to it, the bladder is provided with a moderately thick, strong, and extensible layer of fibrous tissue mingled with elastic fibres. The lining mucous membrane of the bladder is smooth, pale rose red, and closely adherent to the fibrous layer beneath. It has an epithelium, like that of the ureters and pelves of the kidneys, consisting of several layers of cells, of which the deeper ones are columnar, and the superficial ones larger and tessellated. In the neck of the bladder it is also pro- vided with a few minute racemose glands. In the empty condition of the bladder its mucous membrane is thrown into wrinkles, which disappear as the organ undergoes distention. Some- times it presents reticular ridges corresponding with the arrangement of the fasciculi of the muscular coat ; a condition usually due to inordi- nate action of the latter arising from obstruction to the emission of the urine. At the bottom of the bladder, extending from the neck toward the fundus, a slightly elevated triangular space is observable, named the vesical triangle. 2 The apex of this constitutes the vesical uvula, 3 a small, rounded elevation projecting into the orifice of communication of the bladder with the urethra. The basal angles of the vesical triangle are formed by the orifices of the ureters, which appear as oblique slits the one-eighth of an inch long. The muscular structure 4 beneath the mucous membrane of the vesical triangle is thick, and often presents fasciculi 5 diverging from the vesical uvula to the orifices of the ureters. 1 Musculus sphincter vesicse. 3 Uvula vesicee. 2 Trigonum vesicse ; t. Lieutaudi ; cor- 4 Muscle of the vesical triangle, pus trigonum. 5 Muscles of the ureters. THE URINARY ORGANS. THE URETHRA. The TJre'thra 1 in the male serves as a passage for the urine and the spermatic liquid. As its anatomical relations may be best understood after describing the penis, an account of it is reserved for the chapter on the organs of generation. The Ure'thra of the female serves alone for the passage of the urine. In consequence of the divided condition of the spongy body of the cli- toris it does not extend through this organ, as the male urethra does through the spongy body of the penis ; and it therefore corresponds only with the prostatic and membranous portions of the urethra of the male. It is about an inch and a half long and three or four lines wide, though it is capable of greater distention. From the bladder it curves down- ward and forward beneath the pubic arch, and terminates at the middle of the base of the vestibule just above the orifice of the vagina. It lies imbedded in the anterior wall of the latter canal, and pierces the trian- gular ligament, its external orifice 2 being indicated by a slight papillary eminence about an inch behind the. glans of the clitoris or twice that distance from the anterior commissure of the vulva. The lining mucous membrane of the urethra is longitudinally folded, reddish, and provided with minute racemose glands. 3 Its epithelium is squamous toward the external orifice, and assumes the character of that of the bladder toward its inner orifice. Exterior to the mucous mem- brane is a layer of fibrous tissue containing many blood-vessels, especially veins forming a plexus. The urethra is also furnished with a layer of unstriated muscular fibres mingled with elastic and fibrous tissue. THE SUPRA-RENAL BODIES. The Supra-re'nal bodies 4 are a pair of flattened triangular organs, situated one upon the upper extremity of each kidney, and inclined in- wardly toward the vertebral column. Their upper border is thin and convex ; their lower border or base is thick and concave, and is attached by long, loose areolar tissue to the corresponding kidney. Their poste- rior surface, moderately convex, rests against the crura of the diaphragm ; their anterior surface, more flat, on the right side is in contact with the liver, on the left side with the pancreas and spleen. The surfaces present 1 Meatus, or ductus urinarius. glandulee supra-renales ; capsulge atra- 2 Meatus urinarius ; urethral orifice. biliariae, renales, or supra-renales ; re- 3 Glands of Littre. nal glands, or capsules ; renes succentu- 4 Supra-renal capsules, or glands; riati; nephridi. 30 466 THE URINARY ORGANS. vascular furrows, the largest of which at the base is distinguished as the hilus. The supra-renal bodies are brownish yellow in color, of moderately firm consistence, and vary in size in different individuals, and slightly on the two sides. Generally they are about one and a half inches in breadth and height, and about one-fourth of an inch thick. Besides a quantity of loose areolar tissue, often mingled with fat, connecting them with contiguous parts, they have a thin but strong fibrous coat. When a section is made across the supra-renal bodies, they are found to be composed of an external layer, named the cortical substance, and an internal softer material, the medullary substance. FIG. 293. FIG. 294. SECTION OF THE CORTICAL SUBSTANCE OF A SUPRA- RENAL BODY, highly magnified, a, stroma of fibrous tissue; 6, oblong oval receptacles occupied by groups of cells. CELLS FROM THE SUPRA-RKNAL BODY, highly mag- nified, a, nucleated cells from the cortical sub- stance; 6, c, d, cells from the same containing fat; e, cells from the medullary substance. The cor'tical layer 1 is yellow in color, of moderately firm consistence, and is striated, or presents a columnar appearance at right angles to the surfaces of the layer. Examined with the aid of the microscope, it ex- hibits oblong receptacles occupying a fibrous stroma continuous with the fibrous coat of the body. These receptacles have their long diameter vertical to the surface of the cortical substance, and are filled with fine granular matter, nuclei, oil globules, and pigment granules. According to Kolliker, all of these elements are the contents of groups of cells oc- cupying the receptacles of the cortical stroma. The med'ullary substance 2 is a dark-brown, pulpy matter, so easily broken that the cavity frequently observed in its interior is usually viewed as being an accidental laceration. It consists of a fine stroma of areolar tissue continuous with that of the cortical substance, and con- taining in. its meshes fine. granular matter, pigment granules, oil globules, and nucleated cells somewhat resembling those of the nerve centres. 1 Substantia corticalis ; cortex. 2 Substantia medullaris. THE URINARY ORGANS. 467 The blood-vessels of the supra-renal bodies are numerous. Each is supplied by the supra-renal artery from the aorta, together with branches from the contiguous phrenic and renal arteries. Upon entering the organ the arteries ramify through its fibrous stroma, and terminate in capillaries surrounding the receptacles of granular and cell contents. The veins emanating from the organ usually form a single trunk, which terminates on the right in the inferior cava, on the left in the correspond- ing renal vein. Few lymphatics have been noticed. The nerves are chiefly derived from the solar and renal plexuses of the sympathetic system, and are so numerous as to have given rise to the impression that the supra-renal bodies may have some important function in connection with the nervous system, otherwise the use of these organs remains totally unknown. CHAPTER X. THE GENERATIVE APPARATUS. THE MALE ORGANS OF GENERATION. THE organs of generation of the male consist of the testicles and penis, together with certain accessories. THE TESTICLES. The Testicles 1 are two glandular bodies which secrete the spermatic liquid, and are suspended within the scrotum, one on each side, by the spermatic cords. The Scro'tum 2 is the pendant pouch below the pubes, containing the testicles. The skin of the scrotum is thin, darker than elsewhere, and more or less wrinkled. It is marked in the median line by a slight ridge, the raphe, which is continued forward on the under part of the penis, and backward to the anus, and is an indication of original separa- tion of the two halves of the scrotum in the embryo. From the surface of the skin project scattered crisp hairs, whose roots are surrounded by groups of sebaceous glands, appearing as whitish eminences on the scrotum. The inner portion of the skin of the scrotum is composed of pale-red, unstriated muscular fibres, constituting the dar'tos. 3 This structure fades away at the borders of the scrotum into the neighboring superficial fascia. In the median line, mixed with fibrous tissue, it forms the scro'- tal partition, 4 which divides the scrotum into two recesses lodging the testicles. Upon the presence of the dartos depends the contractility of the 1 Testiculi ; testes ; sing. : testiculus ; lis ; folliculus genitalis ; the purse ; the testis; t. virilis; orchis; didymus ; po- cods; the bags. mum amoris ; hernia ; pi. : gemini ; 3 Tunica dartos ; t. muscularis ; t. ru- stones, bicunda scroti; membrana carnosa ; 2 Scortum ; scorium ; oschus ; marsu- marsupium musculosum. pium ; bursula; bursa testium ; b. viri- 4 Septum scroti. (468) THE GENERATIVE APPARATUS. 469 scrotum ; and ordinarily, under the influence of cold, it is observed to throw the skin on each side of the raphe into transverse, corrugated wrinkles ; but from the impression of warmth it becomes relaxed and the scrotum elongates. The Spermat'ic cord 1 consists of the excretory duct, blood-vessels, lymphatics, nerves, and cremaster muscle of each testicle. From the in- ternal abdominal ring it pursues its course through the inguinal canal and external abdominal ring downward to the back part of the testicle. The constituents of the spermatic cord and the testicle are enveloped in an abundance of areolar tissue, the spermatic fascia, 2 which ifc con- tinuous at the abdomen with the superficial and transverse fasciae. In- volved between the layers of the spermatic fascia are the thin, scattered fasciculi of the cremas'ter muscle. 3 This arises within the inguinal canal, from Poupart's ligament and the spine of the pubis, and descends along the spermatic cord to end in loops upon the testicle. It is com- posed of striated fibres, and acts in raising the testicles; in some indi- viduals being under the control of the will. Succeeding the spermatic fascia, the testicle is inclosed in a serous membrane, the vag'inal tunic. 4 This, after investing the organ and ad- hering closely to it, is reflected from its back part so as to form a sac, the cavity of which contains a serous liquid secreted by the vaginal tunic. The outer part of the latter is loosely attached to the spermatic fascia, except at the lower part of the testicle, where a broad band of areolar tissue connects it more firmly with the bottom of the scrotum. This band is the remains of the gubernac'ulum of the testicle, 5 a struc- ture of foetal life, apparently intended to determine the future position of the organ with which it is attached. The Testicles, connected with the spermatic cords, hang obliquely, their upper extremity being directed forward and outward ; and the left one usually is lower than the right one. They are oval, laterally com- pressed, measure about an inch and a half long, and weigh each about three-fourths of an ounce. Each testicle consists of an anterior oval body, properly named the testis, and a posterior elongated portion clasping the former, and called 1 Funiculus spermaticus ; testicular rium testis; elevator testiculi; tunica cord ; corpus varicosum. erythroides. 2 Spermatic fascia in part ; tunica va- 4 Tunica vaginalis ; t. v. propria ; t. ginalis communis testis. adnata testis and t. v. reflexa. 3 Musculus cremastericus testis, or 5 Gubernaculum testis ; g. Hunteri ; testicondus ; suspendiculum ; suspense- ligamentum suspensorium testis. 470 THE GENERATIVE APPARATUS. the epidid'ymis, 1 The upper extremity of this, named the head, 2 is the larger, and closely adheres to the contiguous part of the testis ; its lower extremity, or tail, 3 loosely adheres to the latter, and turns upward on itself to become the spermatic duct. The portion of the epididymis between its head and tail is the body, and is separated from the testis by an interval into which the vaginal tunic is reflected. FIG. 295. TESTICLE, WITH THE VAGINAL TUNIC LAID OPEN. 1, lower part of the spermatic cord ; 2, body of the testicle ; 3, body, and 4, tail, of the epididymis ; 5, reflected portion of the vaginal tunic. TRANSVERSE SECTION OF THE TESTICLE, a, sper- matic fascia; b, reflected portion of the vaginal tunic ; c, cavity of the latter ; d, investing portion of the same membrane ; e, albugineous tunic ; /, vaginal and albugineous tunics of the epididymis ; g, its interior tubular structure ; h, mediastinum ; i, branches of the spermatic artery ; k, spermatic vein ; I, spermatic duct ; m, artery of the latter ; n, lobules of the testis ; o, septula separating the latter. The testis is invested with a dense, white membrane, the albugin/eous tunic, 4 which is composed of interlacing bundles of fibrous tissue, and serves by its strength to protect the soft glandular structure within. At the upper part of the testis it is continuous with a thinner investment of the same kind on the epididymis ; and at the back part forms a process named the mediastinum. 5 This projects into the glandular substance of the testis so as to produce an incomplete vertical partition, and from it diverge numerous fibrous bands, named sep'tula, 6 which are inserted into the inner surface of the albugineous tunic, and serve to sustain the deli- cate secretory structure of the organ. 1 Didymis ; parastata ; testiculus ac- cessorius ; caput testis ; corpus varico- sum testis ; supergeminalis. ' 2 Globus major; caput. 3 Globus minor ; cauda. 4 Tunica albuginea ; peritestis ; dura mater testis ; membrana capsularis tes- tis ; albuginea testis ; perididymis. 5 M. testis; corpus Highmori, or Highmorianum ; meatus seminarius. 6 Septula testis. THE GENERATIVE APPARATUS. 471 FIG. 297. Upon the inner surface of the albugineous tunic, mediastinum, and septula is spread a delicate vascular tunic, 1 formed by the spermatic blood-vessels, which pass to and from the testis through the mediastinum. The vascular tunic holds the same relation to the secretory substance of the testicle that the pia mater does to the brain ; that is to say, it is the point of departure and termination of the capillary blood-vessels of the organ. The Glandular structure of the testis is a soft, reddish-yellow, in- elastic mass, divided into several hundred pyramidal or conoidal lobules, 2 which converge toward the medi- astinum. Each lobule con- sists of from one to three seminiferous tubules, 3 occasionally branching and exceedingly convo- luted. At the narrow extremity of the lobules the tubules end in straight tubes, 4 which enter the mediastinum and form to- 6 gether within its length a reteform plexus, 5 From the upper part of this plexus about a dozen ef- ferent canals 6 emerge and pass out of the testis to the head of the epididy- mis. Within the latter TESTICLE , DEPRIVED OF ITS TUNICS< a , body of the testicle, or the the efferent Canals become testis; b, lobules; c, position at which they end in the straight convoluted into a series tubes; d : retefo ; rm plexus ; e ' efferent canals;/ ' 8permatic cone8 ' g, epididymis ; n, commencement of spermatic duct; i, a spermatic of Spermatic COneS. 7 cone unattached to the testis ; m, n, branches of the spermatic ar- These Successively end in tery ' ' deferent ar *ery; p, anastomosis between the two latter a single, coarse, and much convoluted tube forming the body and tail of the epididymis, which finally terminates in the straight spermatic duct, 1 Tunica vasculosa. 2 Lobuli testis. 3 Tubuli or canaliculi seminiferi; sem- inal tubes or canaliculi ; vasa seminalia ; vascula serpentina. 4 Vasa, or ductuli recti. 5 Plexus reteformis ; rete vasculosum testis ; r. v. Halleri. 6 Vasa efferentia. 7 Coni vasculosi; c. v. Halleri. 472 THE GENERATIVE APPARATUS. Usually there is a spermatic cone joining the epididymis below the others, which has no connection with the testis. 1 The seminiferous tubules are about one-tenth of a line in diameter, and are composed of a basement IG ' " ' membrane strengthened with a deli- cate layer of fibrous tissue, and lined with soft, polyhedral secret- ing cells. These, which are named sperm cells, elaborate the spermat'- ic or sem/inal liquid, the peculiar secretion of the testicles. The contents of the cells, besides the nucleus, consist of finely granular matter, which subsequently assumes the form of bundles of filamentary bodies, named spermatozo'ids. The PORTION OF A SEMINIFEROUS TUBULE, highly mag- nified, a, fibrous coat; 6, basement membrane ;c, Cells are Constantly Cast off aild spermatic cells. burgt> whUe otherg are success ively developed. The canal of the epididymis, besides an external layer of fibrous tis- sue, is provided with unstriated muscular fibres ; and its lining membrane has a columnar epithelium. The Spermatic duct, or vas deferens, 2 is the excretory duct of the testicle. It is a cylindrical tube, about a foot and a half in length and from a line to a line and a half in diameter. From the tail of the epi- didymis it ascends along the inner side of the latter and forms one of the constituents of the spermatic cord, in which it lies behind the blood- vessels, and is readily distinguished by its wire-like feel. Having passed through the inguinal canal, it leaves the spermatic vessels at the internal abdominal ring and descends into the pelvis. Reaching the side of .the bladder, it curves backward and downward beneath the fundus, and passes forward in a convergent manner to form, in conjunction with the duct of the seminal vesicle, the ejaculatory duct. The walls of the spermatic duct are exceedingly thick, and its calibre is about equal to the size of an ordinary bristle. For the greater part of its length the duct is straight, but beneath the bladder it becomes enlarged, tortuous, and more or less sacculated. In this latter position its walls are thinner and its capacity greater than elsewhere ; but ap- proaching its termination it again becomes narrower. 1 Vasculum, or vas aberrans ; v. a. Halleri. 2 Canalis, or ductus deferens ; vibrator. THE GENERATIVE APPARATUS. 473 The structure of the vas deferens is the same as that of the epididy- mis; consisting of an external fibrous coat, an unstriated muscular layer, and a lining mucous membrane. The latter is thrown into fine longitudinal folds ; and in the terminal, sacculated portion of the tube, exhibits fine reticular folds. The testicle receives blood from the spermatic artery. The spermatic duct is supplied by the deferent artery, 1 a long, thread-like vessel derived from the superior vesical artery. After giving branches to the epididymis, the remainder of the spermatic artery penetrates the testis through the mediastinum, and ramifies in the vascular tunic. The sper- matic veins, emerging from the back of the testicle as they ascend the spermatic cord, form an intricate anastomosis, named the pampin/iform plexus. 2 The lymphatics of the testicle are numerous and large, and communicate with the lumbar ganglia. The nerves are derived from the spermatic plexus of the sympathetic. THE SEMINAL YESICLES AND EJACULATORY DUCTS. FIG. 299. The Sem/inal vesicles 3 are two compressed, ovoidal bodies, closely adhering to the under surface of the fundus of the bladder. They are quite near each other behind the prostate gland, but diverge poste- riorly so as to include a triangular space. They are separated from the rectum only by the thin recto - vesical fascia ; and to their innei 1 side lies the terminal sacculated portion of the spermatic ducts. They vary in size, but usually are about two inches long and half an inch wide. Their posterior ex- tremity is obtuse ; and their ante- rior extremity narrows into a short duct, which joins with the corre- sponding spermatic duct, at a very acute angle, to form the ejaculatory duct. The seminal vesicles consist each of a coarse tube closed at the pos- terior extremity, and convoluted into a mass. When unraveled, the 1 A. vasis deferentis Cooperi. 3 Vesiculae, or capsulae seminales ; v. 2 Corpus pampiniforme. spermaticae ; conceptacula seminaria ; gonecystides. POSTERIOR VIEW OF THE FUNDUS OF THE BLADDER 1, peritoneum extending as far down as the trans- verse line; 2, ureters; 3, spermatic ducts; 4, semi- nal vesicle of the left side ; 5, right seminal vesicle dissected so as to show its tubular character ; 6, duct of the seminal vesicle, joining the spermatic duct to form 7, the ejaculatory duct ; 8, prostate gland ; 9, membranous portion of the urethra. 474 THE GENERATIVE APPARATUS. FIG. 300. tube is found to be three or four inches long, the diameter of an ordi- nary goose-quill, and provided with a few simple and branching co3cal appendages. In structure, they are like the sacculated terminal portion of the spermatic ducts, except that their wall is thinner. The Ejac'ulatory ducts 1 are formed by the conjunction, on each side, of the corresponding spermatic duct with that of the seminal vesicle. They are nearly an inch long, and converge to the prostate gland, through which they pass side by side to terminate at the border of the orifice of the utricle communicating with the urethra. They have thin walls, gradually become narrower in their course, and end each in a slit-like aperture. The seminal vesicle and ejaculatory ducts receive blood through branches of the inferior vesical and middle haemorrhoidal arteries. Their nerves are derived from the hypogastric plexus of the sympa- thetics. The testicles secrete the spermatic liquid, which accumulates in the sacculated terminal portions of the spermatic ducts, and in the sem- inal vesicles. The latter, however, not only serve as reservoirs to the spermatic liquid, but likewise secrete a fluid which serves to dilute the more viscid secretion of the testi-. cles. The ejaculated spermatic liquid or se- men 2 is a whitish, viscid matter, mainly con- sisting of a colorless liquid containing im- mense numbers of minute bodies named sperm- atozo'ids. 3 These are the essential constituent of the spermatic liquid of animals that upon which its fecundating power depends. They vary in form and size in different animals, and are endowed with inherent power of movement. In man they are about the --An of an inch long, SPERMATOZOIDS. 1, magnified 350 . , . . _ . , , .., , diameters; 2, magnified 800 diame- and COUSlSt Of an OVOldal head, With a.long, ters; a, viewed on the narrower filamentary appendage or tail, which vibrates side; b, on the broader side. . ,, . ,. mi . -, with wonderful rapidity. The spermatozoids are not properly independent animals, as was once generally supposed, but simply particles of the structure of an animal ; a constituent portion of the contents of the spermatic cells of the testicles. In the case of 1 Ductus, or canales ejaculatorii ; common seminal ducts. 2 Sperma; sperm; seminal fluid; seed; semen virile, masculinum, or genitale. 3 Spermatozoa ; spermatic filaments. \ THE GENERATIVE APPARATUS. 475 ciliated epithelial cells we have more complex particles of an animal structure, also endowed with movement, and although ordinarily fixed, when artificially detached, they move in liquids in the same manner as the spermatozoids. The quivering of a detached fragment of muscle is no indication of its being an independent animal ! THE PENIS. The Penis 1 is composed of three columnar bodies invested by skin and filled with a peculiar, vascular, sponge-like structure, upon the dis- tention or emptying of which the erection or collapse of the organ de- pends. The attachment of the penis to the pubic arch and symphysis is named its root ; the free extremity is its glans or head ; and the inter- mediate portion is the body. The surface of the latter, directed forward in a collapsed state of the organ, but backward in its erect condition, is named the dorsum or back. The Glans 2 is a blunt cone with an expanding base, named the corona, 3 beneath which is the constriction, named the cervix or neck. 4 The sum- mit 5 of the glans presents a vertical slit-like orifice, 6 which is the termin- ation of the urethra. The skin of the penis is thin, and adheres to the organ by a loose superficial fascia allowing much freedom of movement. At the free ex- tremity of the penis it forms a loose cup-like fold, named the pre'puce, 7 after which it is reflected on the cervix and upon the glans. To the latter it firmly adheres ; and from below the urinary meatus it extends in a median fold, named the prepu/tial fraenum. 8 In front of the pubis the skin invests a thick accumulation of fat, and is abundantly provided with crisp hairs, projecting from among whitish groups of sebaceous glands. On the body of the penis the skin is always free from fat, and is provided with scattered crisp hairs, which diminish and finally disappear anteriorly. It also presents many whitish groups of sebaceous glands, which are especially congregated about the roots of the hairs, and on the under part of the penis. 1 Membrum virile ; phallus; mentula; 4 Collum; sulcus retro-glandularis. priapus; veretrum; virga; coles; verpes; 5 Apex glandis. nervus; cauda; the yard; the male or- 6 Meatus urinarius; orificium urethra?, gan, etc. T Praeputium ; foreskin. 2 Balanus ; caput penis. 8 Frsenurn, or frsenulum prseputii. 3 Corona glandis. 476 THE GENERATIVE APPARATUS. At the free border of the prepuce, the skin, as it folds inwardly, as- sumes more the character of a mucous membrane, becoming softer, thinner, and more moist, and it is destitute of perspiratory glands and hairs. At the cervix and corona, it is abundantly furnished with seba- ceous follicles, named the prepu'tial glands. 1 The secretion of these, together with the desquamated epidermal cells of the cervix, constitute the smegma, 2 a white caseous substance, readily decomposing, and emit- ting a strong odor. Upon the glans, the skin becomes most vascular and sensitive, and is devoid of glands. The superficial fascia of the penis is continuous with that of the ab- domen and perineum, and with the dartos of the scrotum, and is always free from fat. From the lower part of the linea alba, and the front of the pubes, a fibro-elastic fasciculus, named the suspensory ligament, 3 descends to the root of the penis and becomes continuous with its super- ficial fascia. The Cav'ernous bodies 4 are two long fusiform columns, whose poste- rior extremities, named crura, spring from the inner border of the rami of the ischia and pubes. Converging, the crura join each other in the median line, after which the cavernous bodies lie side by side, intimately associated, until they terminate in a common conical extremity, which is capped by the glans. The crura have a firm tendinous attachment to the pubic arch, and each crus is somewhat swollen 5 before it conjoins with the other. A slight groove between the cavernous bodies on the dorsum of the penis is occupied by the dorsal blood-vessels, and a deeper groove below accommodates the spongy body. The cavernous bodies have a strong exterior wall, consisting of a dense, tendon-like, fibrous membrane. Where they conjoin, the latter forms an intervening vertical partition, which is complete and is thickest posteriorly ; but anteriorly its fasciculi are separated by clefts, which give the partition a comb-like arrangement ; hence the name of pectini- form septum. 6 From this septum bands diverge to the interior surface of the cavernous walls, besides which other bands pass in all directions through the interior of the cavernous bodies. The bands, composed of fibro-elastic tissue, are named trabec'ulae, and these, together with blood-vessels occupying their intervals, form a soft, red, spongy sub- stance, the erec'tile tissue 7 of the cavernous bodies. 1 Glandulae prae put i ales ; g. odoriferae 4 Corpora cavernosa ; c. nervosa ; c. praeputii ; g. o. Tysoni ; g. Tysonianae ; nerveo-spongiosa ; corpus carvernosum. g. sebaceae glandis ; g. coronse penis. 5 Bulb of the cavernous body. 2 Sebum praeputiale. 6 Septum pectiniforme ; s. penis. 3 Ligamentum suspensorium penis. 7 Textus, or tela erectilis. THE GENERATIVE APPARATUS. 477 FIG. 301. The Spongy body 1 commences in front of the triangular ligament of the pubis, below the crura of the cavernous bodies, in an enlargement named the bulb, 2 From this it extends along the groove below the cavernous bodies, cylindroid in form but slightly narrowing, and at the anterior extremity of the latter ex- pands into the glans. The base of the bulb is divided by a median groove, and is in contact with the triangular ligament. The base of the glans is excavated, and fits upon the conical termination of the cavernous bodies. The urethra enters the spongy body above and in advance of the base of its bulb, and then traverses the entire length of the former to terminate at the summit of the glans. The spongy body is provided with an exterior fibrous wall and an in- terior erectile tissue, like the cavernous bodies ; but the former is much thinner and the latter more delicate than in these. FIG. 302. TRANSVERSE SECTION OF THE PENIS, a, cavernous bodies : the vertical line in the middle is the pec- tiniform septum ; those diverging from it are the trabeculae ; the intervening spaces are occupied by erectile tissue ; b, spongy body ; c, urethra. VERTICAL SECTION OF THE PENIS AND BLADDER. 1, pubic symphysis ; 2, triangular ligament ; 3, abdom- inal muscles; 4, crus of the right cavernous body; 5, pectiniform septum ; 6, glans; 7, spongy body ; 8, its bulb; 9, bladder; 10, its summit; 11, its fundus; 12, its neck; 13, prostatic portion of the urethra; 14, membranous portion; 15, spongy portion; 16, navicular fossa; 17, prostate gland; 18, suburethral gland; 19, right seminal vesicle; 20, spermatic duct; 21, ejaculatory duct; 22, urachus; 23, peritoneum; 24, its recto-vesical fold. The cavernous bodies are supplied with blood by the cavernous arteries, together with a few small branches from the dorsal arteries of 1 Corpus spongiosum ; c. s. urethrae ; c. cavernosum urethrae ; substantia spon- giosa urethrae. 2 Bulbus urethrae. 478 THE GENERATIVE APPARATUS. the internal pudics. The cavernous arteries enter the crura of the cav- ernous bodies and advance near the pectiniform septum, ramifying in their course. The spongy body is mainly supplied by the bulbo- urethral arteries, which penetrate the bulb. The arteries of both the cavernous and spongy bodies terminate finally in the interspaces of the erectile tissue. According to Miiller and other excellent authorities, many of the ar- terial branches, especially at the root of the penis, form short convolu- tions, the hel'icine arteries, which occupy intervals of the erectile tissue and become distended in erection. According to Kolliker, the extremi- ties of the helicine arteries terminate in much finer vessels, which subse- quently open into interspaces of the erectile tissue. From the latter generally, which hold the position of ordinary capillaries, but which are lined with an epithelium like that of the larger blood-vessels, the veins of the penis may be said to originate. Those of the cavernous bodies partly pass out between these and the spongy body, and wind around the sides of the penis to join the dorsal veins. Short ones penetrate the cavernous walls and immediately join the latter ; but most of the cavern- ous veins pass from the crura and join the prostatic plexus. The veins from the spongy body mainly converge from the base of the glans around the cervix to form the commencement of the dorsal veins ; a few join the latter in their course from the sides of the spongy body ; and others pass back from the bulb to join the prostatic plexus. The lymphatics of the penis are numerous; those from beneath the skin, commencing at the glans, communicate with the inguinal glands ; and those from the interior of the cavernous and spongy bodies pass beneath the pubic arch to join the lymphatic plexus around the prostate gland and fundus of the bladder. The nerves of the penis are also numerous, and are derived from the pudics and the hypogastric plexus of the sympathetics. THE URETHRA OF THE MALE. The TTre'thra, 1 a canal common to the emission of urine and of semen, extends from the neck of the bladder to the summit of the glans penis. It is from seven to ten inches in length, and comprises three divisions : the prostatic, membranous, and spongy portions. The Prostat'ic portion of the Ure'thra 2 proceeds from the neck of the bladder through the upper part of the prostate gland, whence its 1 Meatus, ductus, or canalis urinarius; fistula urinaria; iter urinarium. 2 Pars prostatica urethree. THE GENERATIVE APPARATUS. 479 FIG. 303. name. It is barrel shaped, from one to one and a half inches in length, and is not only the widest, but the most dilatable portion of the canal. At the bottom it presents a longitudinal ridge, named the ure'thral crest, 1 in the front of which is a small pouch, viewed as analogous with the uterus of the female, and named the "u'tricle. 2 This extends between the urethral crest and prostate gland, a depth of from one- fourth to one-half an inch, and has the orifices of the ejaculatory ducts opening into it on each side of its communication with the urethra. The Membranous portion of the ure'thra, 3 continuous from the former, passes out of the pelvic cavity, traversing the triangular liga- ment about an inch beneath the symphysis of the pubes. It is about three-fourths of an inch long, and extends from the apex of the pros- tate gland to the spongy body of the penis, above and in advance of the base of the bulb. It is cylindrical, curved, with the convexity downward, and is the least dilatable portion of the urethra. Besides its lining membrane, it has an exterior layer of unstriated muscular fibres, a thin layer of erectile tissue continuous with that of the spongy body, and a fibrous investment continuous with the triangular liga- ment. The Spongy portion of the ure'thra, 4 the most variable in its length and direction, in- . latter open; d, spongy portion of eludes the remainder of the canal, extending the urethra within the bulb, e; /, from the membranous portion through the in- crura of the cavernous bodies, ITS CONTENTS. 1, the right pubis sawed through ; 2, sacrum ; 3, blad- der; 4, its summit; 5, its fundus; 6, right ureter; 7, neck of the bladder; 8, attachment of the pelvic fascia; 9, prostate gland; 10, membranous portion of the urethra; 11, triangular ligament; 12, subure- thral gland between the two layers of the latter; 13, 14. spongy body; 15, right cavernous body; 16, sig- moid flexure of colon; 17, recto-vesical fold of peritoneum; 18, rectum, with its muscular coat seen; 19, right seminal vesicle ; 20, spermatic duct; 21, pelvic fascia descending to the rectum ; 22, anal elevator muscle; 23, anal sphincter; 24, union of the superficial perineal fascia with the triangular ligament or deep fascia; 25, peritoneum passing from the summit of the bladder to the anti-rior abdominal wall. When the viscera of the pelvis above mentioned are emptied, a por- tion of the small intestine descends into the peritoneal pouches between them. The sides of the cavity of the pelvis are occupied by the pyriform, internal obturator, and anal elevator muscles, the internal iliac blood- vessels and lymphatics, and the sacral plexus of nerves. 496 THE GENERATIVE APPARATUS. THE PERINEUM. FIG. 313. In its most restricted sense, the term perme'um 1 is applied to the space between the anus and scrotum in the male ; between the anus and vul- va in the female. In a broader view of the anat- omy of the perineum, it is usual to describe all the soft parts at the out- let of the pelvis, so that in this relationship the boundaries of the perine- um are the arch of the pubes, tuberosities of the ischia, the sacro - sciatic ligaments, and the coc- cyx. The skin of the peri- neum is thin, dark color- ed, abundantly supplied with sebaceous and per- spiratory glands, and is marked in the middle by VIEW OF THE PERINEUM; the superficial fascia removed from the left side of the figure, a, transverse perineal muscle proceeding from the tuberosity of the ischium to the perineal centre; 6, greater sacro-sciatic ligament; c, anal sphincter; d, anal elevator; e, ischio- cavernous muscle; /, bulbo-urethi al muscle inclosing the bulb of the spongy body. 1, 2, internal pudic artery; 3, inferior hsemorrhoidal artery ; 4, 5, 6, 7, superficial perineal branches ; 8, bulbo-urethral artery ; 9, cavernous artery ; 10, dorsal artery of the penis. a slightly elevated called the raphe. 2 line THE PELYIC AND PERINEAL FASCIA. The Pelvic fascia 3 is attached to the brim of the pelvis, and is there continuous with the transverse and iliac fasciae. Posteriorly it descends upon the sacrum and pyriform muscles of the two sides, giving them an investment. It is also continuous with the fibrous sheaths of the in- ternal iliac vessels and sacral plexuses of nerves. Behind the pubes it descends and attaches itself by two short, narrow processes 4 to the sides 1 Perinaeum ; interfoemineum ; inter- foramineum ; regio perinaei ; foemen ; perin ; mesomerion ; mesocelon : gres- sura; amphiplex ; plichos ; cochone; tauros; anterior and posterior perineum. 2 Tramis. 3 Fascia pelvis ; f. hypogastrica. 4 The anterior and lateral true liga- ment of the bladder; ligamentum pubo- prostaticum medium et laterale, in the male ; 1. pubo-vesicale medium et later- ale, in the female. THE GENERATIVE APPARATUS. 497 of the prostate gland and neck of the bladder. At the sides of the pelvis it descends on the obturator muscle, and forms a narrow tendin- ous arch, 1 which curves from the pubis downward and backward to the spine of the ischium. From the tendinous arch emanate the recto-vesi- cal and ischio-rectal fasciae, and between these originates the anal ele- vator muscle. The recto-vesical fascia 2 is an extension of the pelvic fascia descend- ing on the inner surface of the anal elevator muscle to the prostate gland, neck and fundus of the bladder, and side of the rectum in the male; to the bladder, vagina, and rectum in the female. From the point of contact of the recto-vesical fascia with the organs just named it becomes continuous with their fibrous investments. The ischio-rectal fascia lines the corresponding space throughout. Starting from the tendinous arch of the pelvic fascia, one lamina invests the outer surface of the anal elevator, and becomes continuous with the bottom of the deep perineal fascia and the thin connective tissue of the anal sphincter ; another lamina 3 descends on the lower part of the inter- nal obturator muscle, and attaches itself to the tuberosity of the ischium. The Superficial perine'al fascia consists of a subcutaneous adipose layer, and a deeper membranous layer. The former is continuous with the same structure of the buttocks and thighs, and, in the female, of the labia. Approaching the scrotum it gradually merges into the deeper membranous layer, and posteriorly it dwindles into the thin connective tissue of the anal sphincter. On each side of the latter it is continuous with a mass of areolar and adipose tissue occupying the ischio-rectal fossa a depression several inches in depth between the ischium and rectum. The membranous layer of the superficial fascia is thin and moderately strong. It is connected with the rami of the pubes and ischia, and with the tuberosities of the latter ; invests the ischio-cavernous and bulbo- urethral muscles, and is continuous with the fascia of the spongy and cav- ernous bodies. Posteriorly, after investing the transverse perineal mus- cle, it becomes continuous with the bottom of the deep perineal fascia, the connective tissue of the anal sphincter, and the ischio-rectal fascia. The Deep perine'al fascia, or triangular ligament, 4 is a strong mem- brane extended across the arch of the pubis. It is pierced by the mem- 1 Arcus tendineus ; ischio-pubic arch, 3 Obturator fascia, or band. * Fascia perinsei profunda ; ligamen- J Fascia recto-vesicalis ; diaphragma tuna Camperi ; 1. triangulare urethrae ; pelvis ; visceral layer of the pelvic fas- 1. infra-pubianum ; perineal ligament, cia ; vesical fascia. 498 THE GENERATIVE APPARATUS. branous portion of the urethra ; and this receives from it an investment which is continuous with the fascia of the prostate gland. It further incloses the suburethral glands ; and externally is continuous with the fascia of the spongy body. In the female it is pierced by the extremity of the urethra, and is continuous with the fascia of the vagina. Its lower border is continuous with the superficial perineal fascia. MUSCLES OF THE PEEINEUM. The Ischio-cav'emous muscle 1 arises tendinously from the inner part of the tuberosity and ramus of the ischium, and from the commencement of the crus of the cavernous body of the penis. Its fleshy fibres form a thin layer covering the under part of the crus, and proceed to term- inate in the fibrous investment of the cavernous body. In the female the muscle 2 has similar relations with the clitoris. The action of the muscle is usually considered as aiding to maintain the erect condition of the penis through compression of the commence- ment of the cavernous body. Under ordinary circumstances it would appear to retract or draw down the organ. The Bulbo-ure'thral muscle 3 is single, or rather consists of two muscles united by a median tendinous line, beneath the bulb of the spongy body. Its fleshy fibres arise from the perineal centre and from the line just men- tioned, and proceed obliquely outward and forward, inclosing the bulb of the spongy body, and terminate in the fibrous structure on the back of the latter. A loop of the most anterior of the fibres passes around the cavernous bodies and dorsal vein of the penis, so that this vessel is compressed in the contraction of the muscle. By compression of the bulb of the spongy body and the dorsal vein the bulbo-urethral muscle contributes to maintain the erect condition of the penis. Voluntarily it acts in expelling the last portion of urine, and involuntarily in the emission of spermatic liquid. The Vag'inal Constric'tor 4 is the representative of the foregoing muscle in the female ; the corresponding halves of the bulbo-urethral muscle being separated in the median tendinous line of origin so as to inclose the semi-bulbs of the spongy body and embrace the orifice of the 1 Musculus ischio-cavernosus ; m. 8 M. bulbo-urethralis ; m. accelerator erector, director, or sustentator penis; urinse; m. ejaculator seminis; m. bulbo- m. ischio-urethralis. cavernosus ; m. bulbo-syndesmo caver- 2 M. erector, sustentator, or superior nosus. rotundus clitoridis ; m. ischio-clitoridis, * M. constrictor, or constrictores va- or ischio-sub-clitoridis. ginae, or vulvae ; sphincter vaginae ; m. lati et plani inferiores clitoridis. THE GENERATIVE APPARATUS'. 499 vagina. A slip of the muscle 1 likewise passes around the body of the clitoris and its dorsal vein. The Transverse perine'al muscle 2 arises from the inner part of the ramus of the ischium, and proceeds to the perineal centre. Frequently one or two offsets 3 are situated in advance, and somewhat higher than the main portion of the muscle. The Anal Sphincter 4 is an elliptical ring of fleshy fibres inclosing the anus. Its posterior extremity is attached to the subcutaneous tissue at the end of the coccyx, and its anterior extremity blends with the other muscles connected with the perineal centre. The Anal Elevator 5 is a broad, thin plane of muscular fibres situated within the cavity of the pelvis. It arises from the inner surface of the body and descending ramus of the pubis, the tendinous arch of the pel- vic fascia, and the spine of the ischium. Descending from this wide origin, it converges to be inserted into the end of the coccyx, the side of the anus, the neck of the bladder, and the prostate gland. In the female, instead of the latter, it is attached to the vagina. This muscle raises the whole perineum, in which action it is aided by the transverse perineal muscle. Anterior offsets have been described as special muscles of the urethra. 6 The Coccyge'al muscle 7 is a posterior offset of the preceding muscle. It arises from the spine of the ischium and the lesser sacro-sciatic liga- ment, and passes with this to be inserted into the side of the coccyx. THE MAMMAE. The Mammae or breasts, 8 the milk-secreting organs of the female, exist only in a rudimental condition in the male. Their presence is characteristic of the highest order of animals, which are thence named 1 M. attrahens clitoridis. ani ; m. sedem attolens. In part m. ad- 2 M. transversus perinei ; m. perinaeus ductor, levator, or compressor prostatae. superficialis, or posterior ; m. ischio-pe- 6 M. compressor urethras ; m. c., or rimieus ; m. levator ani parvus. constrictor isthmi urethras ; m. constric- 3 M. transversus perinei alter ; m. pe- tor urethra membranaceae ; m. pubio- rinaeus profundus, or anterior. urethrales ; transverse compressor mus- 4 Sphincter of the anus ; m. sphincter cle ; Guthrie's muscles ; Wilson's mus- ani ; m. s. a. externus, or cutaneus ; m. cles. constrictor ani ; m. orbicularis recti ; m. 7 M. coccygeus ; m. ischio-coccygeus ; coccygio-ani; m. aspidiscus. m. levator, or triangularis coccygis. 5 Elevator of the anus ; m. levater ani; 8 Sing. : masthus ; mastus ; ruma ; m. 1. a. magnus, or interims ; m. latus uber. . Birch M.&. Carbon, Pb. 500 THE GENERATIVE APPARATUS. mammals or mammalia. In most of these they are attached to the parietes of the abdomen, but in apes and man they occupy the front of the thorax. When fully developed in the human female, the mammse form a pair of hemispherical prominences slightly divergent from each other and surmounted by a conical eminence, the nipple. They are separated by a groove in front of the sternum, and extend outwardly nearly to the axilla. Their base rests against the great pectoral muscle, extending from about the third to the seventh rib. The Nipple 1 is of a roseate or brownish hue, and is surrounded by an areola of skin of the same color. Both enlarge and become darker in pregnancy, and the change to some degree is permanent. The skin of the nipple is smooth in the virgin, but after pregnancy becomes more or less wrinkled. It is thin, and furnished with numerous sensitive papilla ; is highly vascular, and, under excitement, capable of erection. At its summit are situated the mouths of the milk ducts, of which there are fifteen or twenty. The skin of the areola is thin, and exhibits scattered, whitish, pimple- like eminences, 2 which are sebaceous glands. These enlarge during suckling, and secrete a peculiar fatty substance which protects the parts from the liability to excoriation. Beneath the skin of the mammae there is a variable amount of adipose tissue, upon the extent of which the size and form of the breasts greatly depend. It is divided into lobular masses by laminae of fibrous tissue extended between the skin and the mammary gland. In thin persons this adipose tissue is absent, and its position is occupied by an abundance of areolar tissue. The Mam/mary gland 3 is circular, with its external surface convex and prolonged to the nipple. Its internal surface is flattened, and ad- heres to the pectoral muscle by connective tissue, which may become much elongated during pregnancy, from the increasing weight of the mammae, unless they are supported by artificial means. From such an elongation of the connection of the mammae they hang purse-like from the front of the thorax, with the nipples directed downward. The mammary gland is of firm consistence, and of a pinkish-white color. It is a racemose gland, composed of from fifteen to twenty lobes closely associated by connective tissue. The lobes are subdivided into lobules, and these consist of the ultimate vesicular structure observed in 1 Teat ; titty ; dug : pap ; mammilla ; papilla. 2 Tubercles of the areola. 3 Glandula lactifera. THE GENERATIVE APPARATUS. 501 other racemose glands, but the whole are so closely united as to appear homogeneous. Under the active state, however, the lobular constitution becomes more evident. From each lobe proceeds a lactiferous duct 1 toward the summit of the nipple, where it terminates by a small orifice, and thus the number of orifices in the latter position correspond with the number of lobes and ducts of the gland. Beneath the areola, the ducts FIG. 314. SEVERAL SMALL LOBULES OF THE MAMMARY GLAND OF A PREGNANT WOMAN, highly magnified. become enlarged, especially during lactation, forming the so-called lac- tiferous sinuses. 2 These are comparatively small in the human female, but in some of the lower animals, as in the cow, they form large reser- voirs for the milk. FIG. 315. DIAGRAM, EXHIBITING THE COURSE OP A LACTIFEROUS DUCT. 1, summit of the nipple; 2, course of ihe ducts through the latter; 3, a lactiferous sinus; 4, origin of the ducts toward the periphery of the gland. The arteries of the mammary gland are the long thoracic, together with other branches of the axillary, and of the internal mammary and 1 Galactophorous ducts; ductus galactophorus. 2 Galactophorous sinuses ; sinus lactei. 502 THE GENERATIVE APPARATUS. intercostal arteries. The veins correspond with the arteries. The nerves are derived from the intercostals. Milk, 1 the secretion of the mammary glands, consists of a colorless liquid, the milk plasma, holding in Fia. 316. suspension innumerable fat-like ** corpuscles, named the milk globules. HP The milk plasma consists of "?o o *4g^ water having in solution casein, c , ^P' lactin or milk-sugar, and salts. CORPUSCLES OBSERVED IN MILK, a, milk globules; The milk globules are of no 6, c, d, colostrum corpuscles in various stages. Definite S1Z6, and Consist of minute Highly magnified. ' . drops of fat apparently inclosed in a thin film of coagulated casein. To them is due the opaque-white color of milk, which constitutes a sort of an emulsion. The souring of milk depends on the conversion of its sugar into lactic acid, which separates the casein from the milk globules, and coagulates it, together with that of the milk plasma, into a finely granular mass, while the oil accumulates as cream. In the inactive state of the mammary glands they secrete only a very small quantity of viscid mucus. The formation of milk occurs through the elaboration of its constitu- ents within the secreting cells of the ultimate gland vesicles, which cells successively advance into the lactiferous ducts and there burst, yielding up their contents in the form of milk. At the commencement of lactation, the liquid first discharged from the mamma3 has a thin, yellowish aspect, and is called colos'trum, This is the result of the first step in the production of milk. Its main pecu- liarity consists in its containing many of the milk-producing cells in an entire state, which are named colos'tmm corpuscles, 1 Lac ; humor lacteus ; latex niveus. CHAPTER XL THE NERVOUS SYSTEM. THE Nervous system 1 is subdivided into the cer'ebro-spinal and sym- pathetic systems. The former consists of the cer'ebro-spinal axis, 2 or the brain and spinal cord, and the nerves 3 distributed thence throughout the body ; the latter is composed of an intricate arrangement of nerves and ganglia, intercommunicating with the cerebro-spinal system, and mainly distributed upon the viscera of the great cavities. Ganglia are likewise found upon most of the cerebro-spinal nerves, several of which, however, are by some anatomists described as belonging to the sympa- thetic system. GENERAL CHARACTERS AND STRUCTURE OF THE CEREBRO- SPINAL AXIS. The Cer'ebro-spinal axis, or the brain, with its prolongation the spinal cord, is a large mass of matter of peculiar anatomical and chem- ical constitution. It is of about the consistency of newly-pressed cheese, and is readily crushed between the fingers. Its substance, together with that of the nerves and the ganglia situated on their course, constitute the nerve tissue. The cerebro-spinal axis is subdivided into the cerebrum and cere- bellum, which form the greater part of the nervous mass, and the pons, medulla oblongata, and spinal cord. The cerebrum and cerebellum are composed, on their exterior, of a reddish or brownish-gray material, named the gray substance ; on their interior, of a milk-white material, called the white substance, which in- cludes a number of nuclei, laminae, and streaks of the gray substance. The pons, medulla oblongata, and spinal cord are composed, exteriorly, of the white substance, and contain gray substance interiorly. The two kinds of nerve substance, in an unaltered condition, to the eye 1 Systema nervosum. 2 S. n. centrale ; neural axis ; cranio-spinal axis. 3 S. n. periphericum. (503) 504 THE NERVOUS SYSTEM. FIG. 317. appear perfectly homogeneous, but when hardened by the action of alco- hol or other means, the white substance readily tears into fibrils, having a determinate direction in every position ; while the gray matter assumes a more granular aspect. The chemical composition of the nerve substance of the cerebro-spinal axis approximates the following : Water 80 Albuminous matter ......... 7 Peculiar fatty matters in association with phosphorus . . 7 Osmazome .......... 1 Phosphates of potassa, lime, and magnesia, chloride of sodium, and sulphur 5 100 The White substance 1 of the brain and spinal cord is of compara- tively simple anatomical constitution. Under ordinary circumstances, when examined beneath the micro- scope, it appears to be composed of transparent beaded filaments 2 of various sizes. The larger filaments, and the bead-like dilatations of the smaller ones, exhibit a double out- line or contour, as if they were hollow and filled with a transparent homogeneous substance. The fila- ments are soft, and with the slight- est violence are broken up into fragments, which partially exude their contents and assume* a multi- tude of irregular forms, as repre- sented in figure 317. Careful in- vestigation shows that the filaments are tubular, and are like those composing the nerves, whence they are named nerve fibres. 3 These, in the unaltered condition, are separately of uniform diameter, arid exhibit a range in different ones of from the T Q J to the ^ of a line in diameter, and in most instances are provided with one, PORTION OF GRAY SUBSTANCE, FROM THE EXTERIOR OF THE CERE- BELLUM. 1, two nerve cells with bi- polar prolongations; 2, granular matter ; 3, nuclear bodies ; 4, nerve fibres. 1 Coat, sheath, or tunic of nerve fibres ; limitary membrane ; primitive sheath ; vagina interna. 2 Neurine ; contentum nervosum ; c. fibrarum nervosarum. 3 White substance of Schwann ; nerve medulla ; n. pulp. 4 Cylinder axis ; central fibre ; primi- tive band ; axis band ; fibra primitiva fibrse nervosae ; fascia primitiva. 5 Substantia grisea; s. cinerea; s. cor- ticalis ; the cineritious substance. Also the varieties : substantia ferruginea, flava, ochracea, nigra, coerulea, violac- ca, spongiosa, and gelatinosa; vesicular neurine. 6 Ganglion globules ; nerve globules, cells, corpuscles, or vesicles ; corpus- cula nervea ; c. nervosa centralia ; glo- buli nervosi nucleati ; g. explementorii ; g. nucleati centrales. 506 THE NERVOUS SYSTEM. two, or more processes, from which they are called unipolar, bipolar, and multipolar cells, They have a delicate wall and soft granular contents, with or without pigmentary matter, upon which the color of the gray sub- stance is partly due. They generally possess a single large, spherical nucleus ; but some of the smaller cells in the central portion 1 of the gray substance of the spinal cord have several nuclei, FIG. 319. LARGE NERVE CELLS FROM THE ANTERIOR HORNS OF THE GRAY SUBSTANCE OF THE SPINAL CORD, highly magnified. The processes of the nerve cells are from one to twenty or more, and start from any part of their periphery. They appear as hollow prolongations, with the ordinary cell contents, or are filled with homogeneous substance, or partly with both. The relation of these processes to contiguous structures has not been definitely settled. Many appear to conjoin with those of other cells, thus forming commissures ; some become continu- ous with the axis fibre of nerve fibres, but in the smallest cells they appear to end without being connected with other parts. They are often of considerable length, simple or branched, and usually continue some distance, especially in the larger cells, before becoming attenuated ; which they, however, do not do at all when they join nerve fibres. 1 Substantia grisea centralis ; gray central nucleus of the cord. THE NERVOUS SYSTEM. 507 | The larger nerve cells, generally acknowledged as being the most important element of the gray substance, are abundant in the anterior horns of the gray matter of the spinal cord, the base of the pos- terior horns, the surface of the fourth ventricle, the gray matter of the medulla oblongata and pons, the dentate body of the cerebellum, the deeper part of the outer layer of the cortical gray substance of the latter, and in the gray matter of the cerebrum. The smaller cells are most numerous in the central portion, and extremities of the posterior horns, of the gray substance of the spinal cord, in the outer layer of the corti- cal gray substance of the cerebellum, and throughout the cortical layer of the cerebrum. The nuclei of the gray substance of the cerebro-spinal axis are more numerous than the nerve cells, and are everywhere abundant, but especially in the deeper layer of the cortical gray substance of the cerebrum and cerebellum. They are mostly smaller than those contained within the nerve cells, but also reach the size of those belonging to the latter. They have finely granular contents and a nucleolus. The granular matter of the gray substance forms a kind of matrix in which the elements above described are imbedded. It is exceedingly fine and soft, resembling that contained within the nerve cells. It is everywhere abundant, but in the superficial portion of the cortical gray substance of the cerebrum and cerebellum is especially large in quantity. The nerve fibres of the gray substance have the same constitution as, and are continuous with, those of the white substance, but are much attenuated, so as generally not to be more than half the diameter of the latter. They form half the bulk of the gray substance of the spinal cord and a large portion of the deeper layer of the cortical gray sub- stance of the cerebrum and cerebellum. The brain and spinal cord are among the most vascular of organs, and their capillary blood-vessels are the finest in the body. These ves- sels are most numerous in the gray substance, everywhere form an intri- cate net-work, and are supplied from the vessels of the pia mater, to which they again return the blood. GENERAL CHARACTERS AND STRUCTURE OF THE CEREBRO- SPINAL NERYES. The Cer'ebro-spinal nerves are connected in pairs with the brain and spinal cord by their larger extremity, and are thence distributed through- out the body. They are white or cream colored, mostly flattened cylin- 508 THE NERVOUS SYSTEM. drical cords, branching in their course at acute angles, and disseminated in fine filaments in the various organs and tissues. With few exceptions they anastomose with one another a short distance after their origin, forming plexuses ; but subsequently anastomoses in the larger branches of most nerves are comparatively unfrequent. Many of the nerves pur- sue the same general course as the principal blood-vessels ; and usually the nerves, blood-vessels, and lymphatics of an organ are observed asso- ciated together with connective and some adipose tissue. The nerves are composed of bundles of nerve fibres, the larger ones, like the muscles, being composed of primary and secondary bundles, which are associated with an abundance of connective, mingled with TRANSVERSE SECTION OF THE SMALL SCIATIC NERVE, magnified fifteen diameters, a, general sheath of the nerve ; b, sheath of the secondary bundles ; c, the primary bundles of nerve fibres. From the calf. some elastic tissue, which constitute their sheath. 1 The sheath of the primary bundles is delicate, trans- parent, and assumes the character of structureless membrane 2 with scattered nuclei. The larger the nerve, the greater is its number of bundles of nerve fibres ; and the branching of a nerve is the sending off of such bundles, and finally of the individual nerve fibres. The anastomosis of nerves consists of an interchange of bundles of nerve fibres. In the course of a nerve trunk the primary bundles frequently subdivide and anastomose ; but in all cases the nerve fibres retain their continuity. The nerve fibres 3 of the nerves have the same constitution as those of the white substance of the brain and spinal cord, but are generally MODE OF ANASTOMOSIS AND BRANCHING OF NERVES. 1, 2, two fasciculi of nerve fibres ; 3, a branch of three fibres; 4, branch of two fibres; 5, 6, branches of single fibres ; 7, anastomosis between two nerves. 1 Neurilemma ; neurymen ; perineu- rion ; tunica, membrana, involucrum, vagina, capsula, fistula, tubulus, or in- dumentum nervorum. 2 Perineurium. 3 Ultimate or primitive nerve fibres ; nerve tubes, or tubules ; fibres nervocse ; tubuli nervei ; fila nervea ; tubular nerve fibres. THE NERVOUS SYSTEM. 509 much larger. In every case they continue undivided, and of nearly uniform diameter from their origin to their destination. The difference in strength of the nerves and white substance of the cerebro -spinal axis depends on the association of connective tissue with the former, and its absence in the latter. For the same reason, a house-fly or other insect, with its complex mus- cular and nervous system, its diges- tive and vascular apparatus, is readily crushed between the fingers ; while the more bulky vertebrate animal is protected from the same easy destruction by what might be called its skeleton of bone, gristle, and fibrous tissue. The nerves are duller, less glisten- ing and dense than tendons, with which the unaccustomed eye is apt to confound them. The transverse striation exhibited by their primary bundles depends on the slightly wavy or undulant course of the nerve fibres, and is found to disappear on stretching the nerves. The nerves are abundantly supplied with blood-vessels, which form a capillary net- work, with elongated meshes, among the bundles of nerve fibres. STRUCTURE OF NERVE FIBRES, partly ideal. 1, a nerve fibre represented in the fresh condition, ex- hibiting in succession its neurilemmft, medullary sheath, and axis fibre; 2, 3, 4, 5, exhibit the same constituents ; the medullary sheath indicated, as it appears shortly after death, by heavy outlines; the axis fibre represented as dotted. In 4, 5, the axis fibre is seen projecting from the cut ends of the nerve fibres. In 4, the medullary sheath is seen exuding in drops through a rupture of the neurilemma. ORIGIN AND TERMINATION OF THE CEREBRO-SPINAL NERVES. The extremity of the cerebro-spinal nerves connected with the brain and spinal cord is called their origin or root, while the peripheral ex- tremity is named their termination. These terms are employed inde- pendently of their functional significance, as most nerves are composed of fibres, of which different ones transmit impressions in opposite direc- tions, and therefore the extremities would more properly be designated their central and peripheral connections. A nerve is said to originate by a single root when its bundles of fibres emanate from one spot or along the same line of the cerebro-spinal axis ; and it is said to arise by two or more roots, when its bundles of fibres 510 THE NERVOUS SYSTEM. form a corresponding number of series emanating from different points of the cerebro-spinal axis. The fibres composing the roots of the nerves are traceable into the substance of the brain and spinal cord, within which they are con- tinuous with nerve fibres of the white substance, or become connected with the neighboring gray substance. This interior connection of the nerves is called their deep or real origin, while their exterior connection with the cerebro-spinal axis is named their superficial or apparent origin. To ascertain the real origin of the nerves is among the most difficult subjects of anatomical investigation, and our knowledge in this respect is very imperfect. From their superficial origin the bundles of fibres of the roots of the nerves become invested with a delicate sheath of connective tissue, con- tinuous with the pia mater. If the bundles of nerve fibres are separated as they emerge from the cerebro-spinal axis they converge together, and the roots of the nerves perforate the dura mater, to pass through foramina of the cranium and vertebral column. In the course of the roots of the nerves to the dura mater, the arachnoid membrane is reflected around them. Externally to the dura mater, the nerves become invested with a strong sheath of connective tissue, which is continuous with the latter membrane, and much increases the size of the nerves. Approaching their termination in the different organs, the nerves form frequent anastomoses ; but, as in the case of the trunks and larger branches of the nerves, these anastomoses consist alone of an inter- change of nerve fibres. The mode in which the latter end in the various tissues, for the most part remains an unsettled question. Until within a short period it was asserted, and the view generally adopted, that the nerves terminated in loops : that is to say, pairs of nerve fibres finally conjoined in an arching or sling-like manner. Recent observations are not confirmatory of such a conclusion. In the muscles, the nerve fibres sent off separately subdivide, and finally lose their medullary sheath, the axis fibre alone ending among the muscular fibres. In some instances, the nerves terminate in peculiar capsular bodies, of which three varieties have been detected. The most remarkable of the nerve capsular bodies are the so-called Pacin'ian corpuscles, 1 attached in greatest number along the digital nerves of the fingers and toes, and occasionally on other nerves. These corpuscles are oval, pyriform, or reniform, from half a line to a line long, of a pearly lustre, and consist of a series of capsules or concen- 1 Pacinian bodies; corpuscles of Vater; Valerian corpuscles; Vater-Pacini'schen Korperchen; papillae nervese. THE NERVOUS SYSTEM. 511 The outer capsules FIG. 323. trie layers of fibrous tissue with scattered nuclei, are separated more widely than the inner ones, and the interspaces, as well as the central cavity of the corpuscle, are filled with a color- less liquid. Each corpuscle is attached to the nerves by a pedicle of fibrous tissue, through which extends a single nerve fibre. The latter, after penetrating the series of capsules, term- inates by sending its axis fibre into the cen- tral cavity of the corpuscle, at the top of which it ends by a simple or divided extremity. The second variety of nerve capsular bodies are the so-called tactile corpuscles. 1 These are oval bodies found in many of the papillae of touch of the fingers and palms of the hands, and the toes and soles of the feet. They average the ^ of a line long, and consist of a single capsule of structureless membrane with transverse nuclei. They are filled with a finely-granular matter, and have entering into them usually two, but sometimes one, or even three or four, nerve fibres. 7 digital nerve; 4, several nerve The third variety 2 of the nerve capsular fibres; 5, the fibrous sheath; 6, bodies are transparent, spherical corpuscles of about the ^ of a line in diameter, discovered in the conjunctiva of the eyeball, the mucous Pacinian cor P uscles atta < hed > of PACINIAN CORPUSCLES, from the digital nerve of the finger of a new-born child. 1, much magni- fied corpuscle, which was reniform ; 2, the pedicle; 3, portion of the nerve fibre to the corpuscle; 7, axis fibre of the nerve fibre; 8, portion of a digital nerve with the natural size. membrane of the root of the tongue and soft palate, and the skin of the glans penis and clitoridis. They are filled with a soft, transparent, homogeneous substance, and have entering into them one or two branches of a nerve fibre. GENERAL CHARACTER AND STRUCTURE OF THE SYMPA- THETIC NERVES. The nerves of the sympathetic system are mostly reddish gray 3 or grayish white, 3 a few of the larger trunks being white, as in the case of the cerebro-spinal nerves. They are generally much smaller than the 1 Corpusculatactus; tactile corpuscles of Wagner, or of Meissner ; Wagner- Meissner'schen Tastkorperchen! ; axile bodies ; touch corpuscles. 2 Corpuscles of Krause ; Krause'schen Endkolben. 3 Nervi molles ; n. grisei ; fasciculi nervosi molles. 512 THE NERVOUS SYSTEM. latter, and are associated with many ganglia, from which the sympathetic has likewise been called the gan'glion'ic system of nerves. In their course to the organs they supply, they usually follow the blood-vessels, upon which they form exceedingly intricate plexuses. The sympathetic nerves are composed of nerve fibres, like those of the cerebro-spinal system in association with others of peculiar charac- ter, called gray fibres. 1 The white nerve fibres are generally much finer than those of the cerebro-spinal nerves, are most numerous in the white trunks of the sympathetic system, and are compar- atively few in the reddish- gray nerves. The gray fibres 1 are far more numerous than the white ones in the red- dish-gray and grayish- white sympathetic nerves. They exist in the form of ELEMENTS OF THE SYMPATHETIC SYSTEM. A, portion of a nerve bands, averaging the gj^ highly magnified : a, nerve fibres ; b, gray fibres with nuclei. B, Q f ft jj ne j n Breadth In three nerve cells from a ganglion. structure they appear faintly granular, indistinctly striated or homogeneous, and are provided with elongated oval nuclei. Whether the gray fibres are a peculiar ele- ment of the nervous structure, or whether they are to be viewed as a variety of connective tissue, is a much-disputed question. GENERAL CHARACTER AND STRUCTURE OF THE GANGLIA. The Gan'glia, or gan'glions, 2 are rounded bodies situated in the course of many of the nerves. Thus, several belong to the trifacial, glosso-pharyngeal, and pneumogastric nerves ; one exists on the pos- terior root of each spinal nerve ; and a numerous series are found on the sympathetic nerves. They are mostly elliptical or spheroidal, but present many varieties of form. The ganglia are viewed as sources of nerve power, and hence, like the brain and spinal cord, are frequently called nerve centres. The term is likewise often applied to the collections of gray substance of the cerebro- spinal axis. 1 Fibres of Remak ; gelatinous fibres. 2 Ganglia nervorum ; nervous gan- glions ; ganglia, gangliones, nodi, noduli, or tubercula nodosa nervorum ; tumores, or plexus ganglioformes ; diverticula spirituum animalium; ganglia of in- crease; formative ganglia. THE NERVOUS SYSTEM. 513 FIG. 325. The ganglia are reddish gray or grayish white, and of firm consistence. They appear like knots or swellings in the course of the nerves, and are furnished with a tightly-adherent membrane continuous with the sheath of the latter. In structure they consist of a mass of nerve cells- imbedded in a stroma of connective tissue, and are traversed by nerve fibres associated with gray fibres. The nerve cells of the ganglia resemble those of the gray sub- stance of the cerebro-spinal axis, but are more uniformly of large size, ranging from about the y^oo to the -gju of an inch. They are globular or oval, and generally unipolar or bipolar, though both apolar and multipolar cells also appear to exist. The processes of the nerve cells are continuous with the nerve fibres passing to and from the ganglion. In the ganglia of the cerebro- spinal nerves, the cells are generally larger than in those of the sympa- thetic system. The nerve fibres partly traverse the ganglia without forming any at- tachment to the cells, while others are continuous with them. The gray fibres of the ganglia are like those of the sympathetic nerves, and are especially abundant in the sympathetic ganglia, in which they occupy the position of a stroma to the nerve cells. The stroma of the cerebro-spinal nerves appears as a homogeneous or feebly striated connective tissue furnished with nuclei, and on isolated nerve cells looks like an especial investment to them. Like other nerve centres, the ganglia are abundantly furnished with capillary blood-vessels. NERVE CELLS FROM THE SEMILUNAR GANGLION OF THE TRIGEMINAL NERVE OF A CAT, highly magnified. 1, nerve cell exhibiting the origin of a nerve fibre : a, sheath of the cell and nerve fibre with nuclei ; 6, the nerve cell within ; c, the nerve fibre within its sheath : 2, cell with the origin of a nerve fibre de- prived of its sheath; 3, nerve cell without sheath or nerve fibre. THE CEREBRO-SPINAL AXIS, OR BRAIN AND SPINAL CORD. The Cer'ebro-spinal axis consists of the brain, which occupies the cavity of the cranium, and the spinal cord, which is a prolongation of the former extending downward into the vertebral canal. Besides the 33 514 THE NERVOUS SYSTEM. skull and vertebral column, the cerebro -spinal axis is further enveloped in three membranes, the dura mater, arachnoid, and pia mater. From it originate the cerebro-spinal nerves, or the cer'ebral nerves and the spinal nerves. It is symmetrical, the two halves being in contact, and united along the median line by commissures of nerve substance. The term com'missure, 1 frequently employed in anatomy, generally im- plies the union of symmetrical parts. In the nervous system it applies to the conjunction of two parts of the brain or spinal cord ; the union of two nerves in the median line of the body, to nerves between two or more ganglia ; and to the fibres uniting nerve cells. THE BRAIN. The Brain, 2 the seat of the intellect, the will, the sensations, and the emotions, is the great nervous mass which, with its enveloping mem- branes, completely fills the cavity of the cranium. The size and weight of the brain varies with the race, sex, age, and individual. It is largest in the white race ; and, all other circumstances being equal, such as race, sex, age, size of body, and health, its bulk bears a general relationship with the development of intellect. Its weight in the adult white male averages near fifty ounces avoir- dupois ; in the female, forty-five ounces. In its relation with the weight of the body, the difference between the two sexes is very little. In relation with the size of the body at birth, the brain bears the propor- tion of one to twenty ; in the adult, of one to thirty-five. The human brain is larger than in any other animal except the species of elephants and whales ; but in relation with the size of the nerves given off from its base, it is larger than in any animal without exception. In relation with the size of the body, the brain is larger in some small mammals and birds than in man, as for instance, in the little monkey Oustiti, the field mouse, and the canary bird. In the infant the brain is of a soft, pulpy consistence, but gradually assumes the firmness, in the adult, of newly-pressed cheese. Its specific gravity is about equal to or a very little greater than water. It is for the most part of a reddish-ash color on the exterior, and is generally ovoid in form, with the broader extremity posterior. Its upper part is uniformly convex, but its lower part, called the base, is uneven. It exhibits four well-marked divisions of unequal size, named the cere- brum, cerebellum, pons, and medulla oblongata. 1 Commissura. 2 Encephalon ; cerebrum. THE NERVOUS SYSTEM. 515 THE CEREBRUM. The Cerebrum 1 forms about six-sevenths of the mass of the brain, and extends the whole length and breadth of its upper part. It is half ovoid, with the narrow extremity forward, the convex side upward, the base downward, and the broadest part opposite the parietal protuber- ances. A deep cleft, the great longitudinal fissure, 2 extends the entire length of the upper part of the cerebrum, and the whole depth of its fore and back part. It accommodates the cerebral falx, and along its upper boundary the superior longitudinal sinus. The lateral halves of the cerebrum are named its hemispheres. 3 These form vertical planes next the longitudinal fissure, have their outer sur- face convex, and their under part forming the three pairs of cer'ebral lobes. The anterior lobes 4 of the cerebrum occupy the anterior fossae of the base of the cranium, and therefore rest above the position of the orbits. The middle lobes 5 occupy the middle fossae of the cranial cavity, and are the deepest portions of the cerebrum. They are separated from the anterior lobes by the Syl'vian fissure, 6 which curves outwardly, and receives the small wings of the sphenoid bone. The posterior lobes 7 have no dividing line from those in advance, and are constituted by the portions of the cerebrum resting upon the tento- rium, or situated above the cerebellum. In the upper view of the brain they completely conceal the latter, and their under surface is somewhat hollowed, to accommodate the prominent upper part of the cerebellum. The cerebral hemispheres have their surface everywhere thrown into winding eminences called convolutions, 8 separated by deep fissures, 9 which receive processes of the pia mater. 1 Cerebrum magnum ; encephalon ; the 6 Lobi medii ; 1. descendentes. brain ; the great brain. <> Fissura, or fossa Sylvii ; fissura an- 2 Superior longitudinal sinus ; fissura, terior ; f. a. inferior et externa ; f. infe- or scissura cerebri longitudinalis ; f. c. 1. rior ; f. transversa. superior, inferior, et horizontalis poste- 7 Lobi posteriores. The middle and rior; interlobular fissure. posterior together named lobi poste- 3 Hemisphaeria cerebri; h. c. et pars riores; 1. majores; 1. temporo-occipitales. media cerebri. Cerebral circonvolutions ; gyri ; pro- 4 Lobi anteriores ; 1. minores. cessus enteroidei cerebri. 9 Sulci ; anfractuosities. 516 THE NERVOUS SYSTEM. The Convolutions of the cerebrum are nearly of uniform diameter, and are rounded at the borders of the fissures separating them, but are rather flattened at the summit. Their course is, however, not symmetrical on the two hemispheres, nor are they alike in two individuals, though there is sufficient correspondence in their position and general direction to permit of their being identified. One 1 of the most characteristic of these convolutions arches over the corpus callosum on each side ; another, 2 less well marked, borders the great longitudinal fissure ; and a third 3 borders the Sylvian fissure, and incloses a small group of convolutions* concealed within the latter. The exterior of the cerebrum is composed of gray substance called, from its position, cortical, 5 while the interior consists of white substance named, in contradistinction, medullary. 6 In a horizontal section of the cerebral hemispheres, they exhibit a central oval surface 7 of white sub- stance spotted with minute red points arising from the division of blood- vessels. The circumference of the plane of white substance is observed to form many processes corresponding with the divided convolutions. These processes are further noticed to be everywhere inclosed by the cortical gray matter, which forms a layer of uniform thickness, and fol- lows the course of all the convolutions and fissures of the cerebral hemi- spheres. In a section of the hemispheres, on a level with the corpus callosum, this appears as a bridge of white substance associating the oval centres 8 of the same material of the cerebrum. In a view of the base of the brain, the posterior lobes of the cerebrum are concealed by the cerebellum. In advance of this are the medulla oblongata and pons, and in front of the latter, along the median part of the cerebrum, the following are observed in succession : the cerebral crura, the mammillary eminences, the infundibulum, the pituitary body, the optic nerves and commissure, and the olfactory nerves. The Crura of the cer'ebrum 9 are two large cylindroid bodies diverg- 1 Great convolution of the corpus callo- 6 Tubular, or fibrous substance; me- sum ; internal convolution of the hemi- dulla cerebri. spheres ; gyrus fornicatus ; processus 7 Centrum semi-ovale ; c. ovale Vieus- cristatus. senii ; c. ovale minus ; lesser oval centre 2 Great convolution of the circumfer- of Vicq-d'Azyr. ence of the hemispheres; marginal con- 8 Greater oval centre; centrum ovale volution of the longitudinal fissure. Vieussenii. 3 Convolution of the Sylvian fissure. 9 Crura cerebri ; pedunculi cerebri ; 4 Island of Reil ; insula ; i. Reilii ; processus medullares cerebri ; caudex gyri operti. cerebri ; crura anteriora medulloe ob- 5 Cineritious, or vesicular substance. longatae ; peduncles of the brain ; cere- bral peduncles. THE NERVOUS SYSTEM. 517 ing from the fore part of the pons into the cerebral hemispheres, at the inner side of their middle lobes. They are longitudinally striated, and composed, on the exterior, of white substance. On the interior they con- tain a collection of gray substance, 1 which appears as a crescentoid layer in a transverse section through them. FIG. 326. BASE OF THE BRAIN. 1, anterior lobes of the cerebrum; 2, middle lobes; 3, posterior lobes; 4. 5, ante- rior and posterior extremities of the great longitudinal fissure; 5, Sylvian fissure; 7. anterior perforated space; H, iufundibulum; 9, mammillary eminences; 10, posterior perforated space; 11, crura of the cere- brum; 12, pons; 13, medulla oblongata; 14, pyramidal bodies; 14*, decussation of the pyramids; 15, oli- vary body ; 16, restiform body ; 17, hemispheres of the cerebellum ; 18, vermiform process at the bottom of the fissure separating the latter ; 19, crus of the cerebellum ; 20, pneumogastric lobule of the cerebel- lum; 21. fissure which accommodates the olfactory nerve, 22; 23, bulb of the olfactory nerve; 24, optic commissure; 25, oculo-motor nerve; 26, pathetic nerve; 27, trifacial nerve; 2% abducent nerve; 29, facial nerve; 30, auditory nerve ; 31, glosso-pharyngeal nerve; 32, pneumogastric nerve; 33, accessory nerve ; 34, hypoglossal nerve. The interval 2 separating the crura at its fore part includes the mam- millary eminences and the infundibulum. At its posterior angle it forms a deep pit, which is separated from the third ventricle by some mingled 1 Locus niger; substantia nigra ; stratum nigrum. 2 Interpeduncular space. 518 THE NERVOUS SYSTEM. gray and white substance perforated by a number of small blood-vessels, and hence named the posterior perforated space. 1 The Mam'millary eminences 2 are two small, white, spherical bodies, in contact with each qther, immediately in advance of the space just mentioned. They are connected above with the anterior crura of the fornix, and contain some gray substance. 3 The Infundib'ulum,* as expressed by the name, is a funnel-shaped body included between the manimillary eminences behind, and the optic commissure in front. It is composed of gray substance, is hollow, and forms part of the bottom of the third ventricle. Its broad base 5 narrows to a tubular process, which is directed obliquely downward and forward, and is closed at the extremity. The Pitu/itary body 6 occupies the corresponding fossa of the sphe- noid bone, and is connected with the end of the infundibulum. It is reddish gray, of firm consistence, and presents an anterior transversely reniform lobe, and a smaller posterior rounded one. Its structure con- sists of a stroma of connective tissue, with many capillary blood-vessels mingled with granular matter, nuclei, and nucleated cells. The Optic com'missure, 7 situated in front of the infundibulum, is formed by the conjunction of the optic tracts converging from the outer side of the cerebral crura. It and its connections will be more particularly de- scribed in the account of the optic nerves. Between the optic commissure and the roots of the olfactory nerves, 1 Substantia perforata postrema, pos- * Funnel ; funnel of the middle ven- terior, or media ; basis ventriculi tertii ; tricle ; pelvis, choana, cyathus, concha, antrum ; pons Tarini. scyphus, lacuna, aquaeductus, embolum, 2 Eminentiae mammillares, candican- labrum, concavitatis conchularis, or pro- tes, glandulosee, papillares, or medulla- cessus orbicularis cerebri; tubercirfe- res ; bulbi fornicis ; bulbs of the fornix ; reum cum infundibulo. b. priorum crurum fornicis ; globuli 5 Tuber cinereum ; substantia perfo- medullares; g. albi; corpora alba, mam- rata media posterior. millaria, albicantia, or glandularia ; pro- 6 Glandula pituitaria, pituitosa, or tuberantiae crurum medullae oblongatae ; basilaris ; hypophysis, appendix, or ap- p. glandulosae ; p. orbiculares ; tuber- pendicula cerebri ; caput rosae ; colato- cula mammillaria, hemispherica, or pisi- rium ; labrum ; lacuna ; infusorium ; formia; prominently albicantes ; glan- concha; pelvis; p. colatoria; sentina en- dulae sub-infundibulo ; g. candicantes ; cephali. processus glandules: protensiones gran- 7 Chiasma opticum; chiasm of the op- dulares ; testiculi cerebri ; mammae mu- tic nerves ; chiasma nervorum optico- liebres. rum. 3 Nucleus griseus. THE NERVOUS SYSTEM. 519 FIG. 327. on each side, are the anterior perforated spaces, 1 so called from their presenting numerous small apertures for vessels which penetrate to the interior of the cerebrum. On pressing apart the cerebral hemispheres, .at the bottom of the great longitudinal fissure, a convex white body, the corpus callosum, is observed to connect the former, and extend for several inches along the latter. The Corpus callo'sum, 2 or great cer'ebral com'- missure, in a section of the brain on a level with it, appears as a bridge of white substance, about three inches long and three-fourths of an inch wide, uniting the central white masses of the cere- bral hemispheres. It reaches farther forward than backward, and is narrower anteriorly. Its upper surface 3 arches in the length, and is trans- versely striated, 4 but ex- hibits on each side of the median line 5 a narrow tract of longitudinal stria?. 6 Its anterior and posterior borders are thick and rounded, and are separated by fissures from the contiguous gray substance of the cere- bral hemispheres. In a vertical section of the brain, along the great longitudinal fissure, TRANSVERSE SECTION OF THE HEMISPHERES OF THE CEREBRUM ON A LEVEL WITH THE CORPUS CALLOSUM. 1, white substance of the hemispheres, dotted with divided capillary vessels ; 2, gray sub- stance on the convoluted exterior; 3, corpus callosum, with the direction of its fibres indicated by transverse striae; 4, longitud'- nal median stria? ; 5, anterior and posterior portions of the great longitudinal fissure. 1 Substantia perforata anterior; s. cribrosa anterior ; lamina cribrosa cere- bri ; substantia perforata antica media, et partes laterales substantiae perforates anticse. 2 Commissura magna, or maxima cere- bri ; trabs cerebri ; t. medularis ; co- pula alba, or magna cerebri : great com- missure of the brain ; mesolobe. 3 Facies, or superficies superior, or libera. 4 Strise, or chordae transversales Wil- lisii. 5 Raphe" ; r. externa ; linea, or chorda longitudinalis. 6 Striae longitudinales Lancisii, in- ternse, or liberae ; nerves of Lancisi. 520 THE NERVOUS SYSTEM. the corpus callosum is observed to be a thick layer of white substance passing beneath an arching convolution of each cerebral hemisphere. Its anterior part 1 appears doubled on itself producing a thick fold, the FIG. 328. SECTION OF THE BRAIN ALONG THE GP.EVT LONGITUDINAL FISSURE. 1, medulla oblongata; 2, pons; 3, crus of the cerebrum; 4, arborescent appearance in section of the fundamental portion of the cerebellum; 5, left hemisphere of the cerebellum; 6, inner surface of the left hemisphere of the cerebrum; 7, corpus rallosum; 8. pellucid septum; 9, fornix; 10, anterior crus of the fornix descending to join the correspond- ing mammillary eminence; 11, fissure through which the interposed vellum 12 is introduced into the third ventricle; 13, pineal gland; 14, its peduncle; 15, rests on the thalamus within the third ventricle; 16, posterior commissure of the latter; 17, middle commissure; 18, anterior commissure; 19, foramen of communication between the third and lateral ventricles ; 20, optic nerve; 21, pituitary body ; 22. infun- dibulum; 23, mammillary eminence; 24, oculo-motor nerve; 25, posterior perforated space; 26, fourth ventricle; 27, valve of the brain; 28, quadrigeminal body; 29, entrance from the third to the fourth ven- tricle ; 30, 31, 32, anterior, middle, aud posterior lobes of the cerebrum. under portion 2 of which becomes continuous with a thin lamina 3 curving downward to the optic commissure, and closing the front of the third ventricle. The posterior part* is seen to reach the base of the cerebrum, just above the position of the quadrigeminal body and the most promi- nent portion of the cerebellum. In structure the corpus callosum consists of a thick stratum of nerve fibres diverging through the white substance of the cerebral hemispheres to their cortical gray substance. 1 Genu corporis callosi. 3 Lamina genu ; lamina cinerea et pe- 2 Rostrum corporis callosi; apex dunculi corporis callosi. genu. 4 Splenium, or tuber corporis callosi. THE NERVOUS SYSTEM. 521 FORNIX. Continuous with the back part of the corpus callosum, and arching forward beneath nearly to its anterior part, is a thin layer of white sub- stance, the fornix. 1 Viewed from above or below it is triangular. Its upper surface along the middle is continuous with the corpus callosum and pellucid septum, and on each side forms part of the floor of the lateral ventricles. Its lower vaulted surface 2 is longitudinally and trans- versely striated, and forms the roof of the third ventricle. The apex of the fornix divides into two portions, its anterior crura, 3 which descend with a slight divergence to the mammillary eminences. The basal angles are prolonged, as its posterior crura, 4 into the middle horns of the lateral ventricles, and become continuous with the fimbri- ated body. PELLUCID SEPTUM. The interval between the corpus callosum and fornix, in the median line of the brain, is occupied by the pellucid septum, 5 a thin partition of nerve substance separating the lateral ventricles. It includes a nar- row cavity or fissure, the fifth ventricle, 6 which is closed at all points, and is lined with a delicate serous membrane. The pellucid septum is composed of gray substance on its exterior surface, and of white substance on the surface next the fifth ventricle. LATERAL VENTRICLES. Beneath the corpus callosum on each side is a cavity with prolonga- tions extending into the three lobes of the cerebral hemispheres. The cavities are the lateral ventricles; 7 the prolongations are named the horns. 8 1 Fornix cerebri, trilateralis, or tri- 5 Septum pellucidum, or lucidum ; cuspidalis ; arcus medullaris ; camera; diaphragma cerebri; d. ventriculorum cornix ; corpus psalloides ; c. camera- lateralium ; speculum ; corpus specu- tum ; trigonum cerebrale ; testudo ; com- lare ; mediastinum ; septum medium ; s. munionis cerebris. tenue ; tympanum ; septum medullare 2 Lyra ; psalterium ; corpus psalloi- triangulare. deum; lamina medullaris ; 1. triangularis; 6 Ventriculus quintus ; ventriculus, membrana medullaris inter crura poste- camera, or sinus septi pellucidi ; inci- riora fornicis. sura septi ; cavitas Vieussenii, Sylvii, 3 Crura or cornua anteriora fornicis ; Duncani, prima, or quinta. cornua fornicis ; columnae fornicis ; an- 7 Ventriculi laterales ; v. anteriores ; terior pillars or pillar; crus, or columna v. magni; v. majores; v. priores; v. su- fornicis. periores ; v. tricornes ; sinus anteriores. 4 Crura posteriora fornicis ; crura for- 8 Cornua; c. laterales ; partes late- nicis ; posterior pillars. rales. 522 THE NERVOUS SYSTEM. Each lateral ventricle has for its FIG. 329. TRANSVERSE SECTION OF THE CEREBRAL HEMI- SPHERES, THE CORPUS CALLOSUM REMOVED, AND THE LATERAL VENTRICLES EXPOSED. 1, white substance of the interior of the cerebral hemispheres; 2, gray substance of the exterior convoluted surface ; 3, 4, anterior and posterior extremities of the cor- pus callosum; 5, anterior horn of the left lateral ventricle ; 6, middle or descending horn ; 7, poste- rior horn; 8, striated body; 9, pellucid septum; 10, fifth ventricle; 11, fomix; 12, posterior crus of the fornix; 13, attachment of the fornix to the under part of the corpus callosum ; 14, hippocam- pus; 15, fimbriated body; 16, ergot; 17, semicir- cular line; 18, choroid plexus; 19, edge of the thalamus. roof 1 the corpus callosum, its floor the fornix, its inner wall the pellu- cid septum, and its outer wall the striated body. The anterior horn 2 of the lat- eral ventricle, less conspicuous than the others, is simply the ex- tension of the cavity around the anterior extremity of the striated body. The middle horn 3 curves down- ward into the middle cerebral lobe. From the inner part of its floor projects a thick convex ridge, in- dented at its lower end,* and named the hippocam/pus, 5 The upper border of the ridge is provided with a white band, named the fim- briated body, 6 which is continuous with the posterior crus of the for- nix. The hippocampus is composed of white substance 7 on the sur- face, of gray substance within, and the latter appears superficially as a dentated band 8 on the inner or concave side of the hippocam- pus. The posterior horn 9 curves in- wardly as it passes into the pos- 1 Tegumentum cellse lateralis; t. ven- triculi lateralis. 2 Cornu anterius. 3 Cornu medium, inferius, descendens, magnum, or laterale ; sinus inferior hip- pocampi ; s. cornu Ammonis ; ventricu- lus inferior hippocampi ; v. bombycinus. 4 Digiti cornu Ammonis ; colliculi fissi interni ; uncus ; pes hippocampi. 5 Hippocampus major; pes hippocam- pi; p. h. major; cornu Ammonis; c. arietis ; vermis, or appendix bombyci- nus; bombyx; processus cerebri late- ralis ; protuberantia cylindroides ; pes hippopotami major. 6 Fimbria, or tsenia hippocampi; lira- bus, or corpus fimbriatum ; c. f. Sylvii. 7 Lamina medullaris superficialis cor- nu Ammonis. 8 Fascia dentata ; margo denticulatus Tarini. 9 Cornu posterius ; cavitas digitalis ; c. ancyroidea ; diverticulum. THE NERVOUS SYSTEM. 523 terior cerebral lobe. From its inner side projects a white, spur-like ridge, named the ergot. 1 The lateral ventricles communicate with each other and with the third ventricle by a foramen 2 beneath the anterior crura of the fornix. In all other positions they are closed, and are lined throughout with a delicate serous membrane. CORPORA STRIATA, OR STRIATED BODIES. Projecting into each lateral ventricle from the outer wall is a half- pyriform prominence, named, from its appearance in section, the cor'pus stria'tum, or striated body, 3 Its larger portion 4 is anterior, and its narrower portion 5 curves backward to the outer side of the thalamus. Some depth from the ventricular surface it is composed of gray substance, 6 beneath which is a layer of white substance, 7 succeeded by a lenticular nucleus 8 of gray substance. The latter is penetrated by the diverging fibres of the cerebral crus, giving to it in section a striated appearance. Below the fore part of the lenticular nucleus is a smaller accumulation of gray substance, 9 and to its outer side is another collection. 10 On the floor of each lateral ventricle is a remarkable vascular append- age of the pia mater, named the choroid plexus, This extends from the foramen beneath the anterior crura of the fornix along the side of the latter, and descends to the bottom of the middle horn of the lateral ventricle. It is continuous beneath the fornix with the interposed velum of the pia mater, and is separated from the cavity of the lateral ventricle by its lining membrane. THIRD VENTRICLE. Beneath the fornix is the third ventricle 11 of the brain. This is a narrow triangular cavity, with its apex forward and its base correspond- ing with the fissure between the posterior border of the corpus callosum 1 Hippocampus minor ; calcar ; c. rum ethmoidalium ; apices crurum me- avis ; unguis ; u. avis ; u. Halleri ; ocrea; dullae oblongatae. pes hippocampi minor ; eminentia minor 4 Caput. digitata; e. unciformis ; ocrea; collicu- 5 Cauda. lus. 6 Nucleus caudatus ; n. intraventricu- 2 Foramen of Monro ; f. Monroi ; f. laris. anterius ; vulva. ? Capsula medullaris nuclei lentifor- 3 PI. : corpora striata; eminentise stria- mis ; capsula externa. tae; e. pyriformes; e. similes coxis hu- 8 Nucleus lentiformis; n. extraven- mani ; e. lenticulares ; prominentiae len- tricularis. tiformes ; apices medullse oblongatae ; 9 Nucleus amygdalae. processus anteriores medullae oblonga- 10 Claustrum ; nucleus tseniseformis. tae ; ganglia magna superiora cerebri ; n Ventriculus tertius ; v. medius cere- g. cerebralia anteriora ; colliculi nervo- bri. 524 THE NERVOUS SYSTEM. and the quadrigeminal body. Its fore part is closed by the anterior descending portion of the corpus callosum. Its floor is formed in suc- cession from before backward by the optic commissure, infundibulum, 1 mammillary eminences, posterior perforated space, and cerebral crura. Behind the latter and beneath the quadrigeminal body it communicates 2 with the fourth ventricle by a narrow passage, 3 the sides of which are coated with gray substance. 4 As previously mentioned, beneath the anterior crura of the fornix it opens on each side into the lateral ven- tricles. At the fissure, 5 between the posterior border of the corpus callosum and the cerebellum, a process of pia mater, the interposed velum, 6 is introduced along the under surface of the fornix, which forms the vaulted roof of the third ventricle. THALAMI. The outer walls of the third ventricle are formed by a large, oval prominence, the thal'amus, 7 which is supported on the inner side of the diverging cerebral crus. Its ventricular surface, for the most part, is composed of white substance, 8 but on the inner side exhibits some gray substance. Its interior is composed of mingled white and gray sub- stance. 9 In front and to the outer side the thalamus is separated from the stri- ated body by a narrow semicircular band 10 of white substance. The anterior and posterior more prominent portions of the thalamus are named its tubercles. 11 Beneath the posterior tubercle are two convex white eminences, the genic'ulate bodies, 12 which give partial origin to the optic tracts. 1 Aditus ad infundibulum. nse cerebri ; corpora striata superna pos- 2 Aditus ad aquaeductum Sylvii ; in- teriora ; c. s. posteriora interna ; colli- troitus. culi nervorum opticorum ; capita, or 3 Iter etertio adquartum ventriculum; crura medullse oblongatae; juga crurum aquaeductus Sylvii; fistula sacra; ven- medullarium ; secundum par tuberculo- triculus subter nates et testes ; transi- rum ; secunda sectio crurum medulla - tus ad ventriculum quartum; aquae rium. emissorium ; canalis medianus ; incile, 8 Stratum zonale. or canalis tuberculorum ; c. corporum 9 Nuclei cinerei. quadrigeminorum. 10 Toenia semicircularis ; t. terminalis; 4 Subsfantia feruginea superior. lamina cornea ; centrum geminum semi- 5 Transverse fissure of the cerebrum. circulare ; stria cornea. In part : acies, 6 Velum interpositum ; tela choroidea. flabellum, and penicillus. 7 Optic thalamus ; pi. : thalami nervo- u Tuberculum superius anterius and rum opticorum ; ganglia magna inferiora t. s. posterius, or pulvinar. cerebri ; g. cerebri media ; g. c. postica ; li Corpus geniculatum internum and protuberantiae striatse ; eminentiae mag- c g. externum ; corpora geniculata. THE NERVOUS SYSTEM. 525 QUADRIGEMINAL BODY. At the back part of the third ventricle is situated a quadrate, white mass, divided on its upper surface by a crucial gutter 1 into four emi- FIG. 330. STRIATED BODIES, THALAMI, QUADRIGEMIXAL BODY, AXD CEREBELLUM. 1, quadrigeminal body; 2, valve of the brain ; 3, superior peduncle of the cerebellum; 4, superior portion of the middle peduncle; 5, supe- rior portion of the crus of the cerebrum; 6, posterior tubercle of the thalamus; 7, anterior tubercle; 8, fundamental portion of the cerebellum ; 9, process of gray substance Besting on the valve of the brain ; 10, posterior commissure of the third ventricle; 11, middle commissure; 12, anterior commissure; 13, pineal gland turned forward; 14, its peduncle; 15, thalaimis ; 16, hemispheres of the cerebellum; 17, dentated body; 18, semicircular line; 19, vein of the striated body; 20, anterior crura of the fornix; 21, striated body; 22, fifth ventricle between the layers of the pellucid septum. nences, from \whence it derives the name of quadrigem'inal body or bodies. 2 It extends obliquely from the thalami toward the cerebellum, with which it is connected by the superior peduncles. At the sides it is 1 Sulcus longitudinalis et s. transver- sus corporum qTiadrigeminorum. 2 Corpora, or tubercula quadrigemina; c. bigemina ; c. anteriores ; protuberan- tiae ; processus natiformes et testiformes; tubercula ; t. anteriora et posteriora ; prominent ias ; p. orbiculares ; p. ence- phalali ; nates et testes ; prominentise, eminently, or corpora superiores et in- feriores, majores et minores, or nati- formes et testiformes ; pons Sylvii. 526 THE NERVOUS SYSTEM. attached to the thalami and geniculate bodies ; and by means of a band 1 of white substance joins the back part of the pons between the crura of the cerebrum and cerebellum. Between it and the posterior border of the corpus callosum is the fissure through which the interposed velum of the pia mater is introduced along the roof of the third ventricle. Beneath it is the entrance from the latter to the fourth ventricle. PINEAL GLAND. Upon the anterior pair of eminences of the quadrigeminal body there reposes a small cone of gray substance, named the pine'al gland. 2 It is remarkable for containing a quantity of sand-like grains, 3 having nearly the same composition as bone earth. From the front of the pineal gland a pair of narrow tracts of white matter, named its pedun'cles, 4 diverge, like the prongs of a fork, to the inner sides of the thalami. COMMISSURES OF THE THIRD VENTRICLE. The anterior com'missure 5 appears as a small transverse cylinder of white substance at the front part of the third ventricle, between the anterior crura of the fornix and the descending portion of the corpus callosum. It is a cord of white nerve fibres extending through the lower part of the striated bodies into the cerebral hemispheres. The middle commissure 6 is a rounded isthmus of gray substance con- necting the thalami across the centre of the third ventricle. The posterior commissure 7 is a thin lamina of white substance ex- tended between the back part of the thalami, and connecting the quadri- geminal body with the pineal gland. THE CEREBELLUM. The Cerebellum 8 forms about one-eighth of the bulk of the brain, and occupies the posterior fossae of the cranial cavity, beneath the ten- 1 Lemniscus ; fillet ; laqueus ; fascicu- * Pedunculi conarii ; striae, or taeniee lus triangularis lateralis ; ribbon of medullares ; habenula ; reins. Reil. 5 Commissura anterior. 2 Glandula pinealis; conarium; pinus; 6 Commissura media ; c. mollis ; chor- penis ; cerebral epiphysis ; corpus co- dae Willisii ; unio thalamoruni nervorum noides; c. turbinatum; turbo cerebri; opticorum. virga. 7 Commissura posterior. 3 Cerebral sand; acervulus cerebri; 8 Cerebrum parvum ; c. posterius ; ap- concrementa pinealia; sabulous matter; pendix ad cerebrum ; encranion; epen- brain sand ; pineal sand ; sabulum co- cranis ; parencephalum ; encephalium ; narii ; lapilli glandulae pinealis. micrencephalum ; encephalus opistliius ; little brain ; after brain. THE NERVOUS SYSTEM. 527 torium, which separates it from the posterior lobes of the cerebrum. Like the latter, it consists of two lateral portions, named hemispheres, 1 which are separated behind and below by a wide, deep groove, named the valley. 2 The hemispheres are associated by an intermediate or fundamental portion, 3 which is not distinctly evident above, but appears at the bottom of the valley as a thick, worm-like ridge, whence it received the name of the verm'iform process. 4 The superior cerebellar surface 5 is moderately convex, is most prom- inent at its anterior portion, 6 and inclines from the median line of union 7 of the hemispheres to their lateral border. The lower and outer sur- faces 8 are prominently convex. The exterior of the cerebellum presents the same gray color as that of the cerebrum, and is divided by numerous fissures 9 into nearly par- allel laminae, 10 having a general transverse direction. When the constitution of the hemispheres is examined, it is found that each consists of an interior prismoid trunk 11 of white substance, from the sides of which emanate about a dozen broad, thin, divergent laminge of the same material. These divide into a second series of thinner laminae, which in many cases subdivide. Around the laminar divisions of white substance the cortical gray substance of the cerebellum is folded, the intervals of the folds corresponding with fissures of the cerebellar surface. In consequence of this arrangement, a vertical sec- tion of the hemispheres exhibits an arborescent appearance, 12 while a transverse section simply presents a broad surface of the medullary white substance bordered by gray substance. The fundamental portion of the cerebellum exhibits the same arrange- ment of structure as the hemispheres, and differs only in accordance with the comparative size of the part. At the anterior extremity of the valley, the hemispheres form a pair of rounded eminences, including between them a more prominent por- 1 Hemisphseria cerebelli ; pontes late- 6 Culmen ; monticulus. rales. * Monticulus ; superior vermiform pro- 2 Vallis ; vallecula ; scissura cerebelli cess ; vermis superior ; protuberantia longitudinalis. vermiformis superior. 3 Ambitus vermis ; vermiform pro- 8 Superficies cerebelli inferior, cess. 9 ulci. 4 Inferior vermiform process ; the 10 Gyri ; convolutions ; circonvolutions. worm; vermis inferior; protuberantia n Stratum medullare ; meditullium la- vermiformis; pyramid of Malacarne; terale. pyramid, uvula, and nodulus. 12 Arbor vitae. 5 Superficies cerebelli superior. 528 THE NERVOUS SYSTEM. tion of the vermiform process, which together, from their resemblance in relative position, have been named tonsils 1 and uvula, Above the tonsils anteriorly, and separated from them by a fissure 2 proceeding from the cerebellar crura outwardly, each hemisphere presents the pneu- mogas'tric lobule, 3 so named from its vicinity to the corresponding nerve. DENTATED BODY. Within the trunk of white substance of each hemisphere of the cere- bellum there is a plicated pouch-like layer 4 of gray substance. In sec- tion this appears as an indented nucleus of white substance 5 bordered by gray substance, whence its name of the dentated body. 6 The gray layer is open at its upper and inner part, in which position the nerve fibres of the white substance gain admission to its interior surface. CRURA OF THE CEREBELLUM. At the base of the brain, the pons extends laterally as a pair of cylindroid processes of white substance, diverging posteriorly, and enter- ing the hemispheres of the cerebellum. These processes are the crura, or middle pedun/cles of the cerebellum. 7 They are longitudinally striated, and consist of large bundles of nerve fibres proceeding from the pons to the white substance of the cerebellar hemispheres. Behind the crura are situated the superior and inferior peduncles of the cerebellum. The Superior pedun'cles 8 are two flattened, cylindrical, white bands, ascending obliquely in a converging manner from the interior white sub- stance of the hemispheres of the cerebellum to the quadrigeminal body. The triangular interval of these peduncles, and the fundamental portion of the cerebellum, is closed by a thin lamina of white matter, incorrectly 1 Tonsillae ; amygdalae ; lobi medullae ciliare ; g. cerebelli ; substantia rhom- oblongatae ; lobi intern! cerebelli. boidea. 2 Sulcus horizontals ; s. perpendicu- 7 Crura cerebelli ; c. c. ad pontem; c. laris ; s. magnus cerebelli. media ; c. lateralia ; c. posteriora ; bra- 3 Lobulinervi-pneumogastrici; appen- chia pontis. dices lobulares anteriores ; flocculi; sub- 8 Anterior peduncles; crura, or bra- peduncular lobes. chia cerebelli ad corpora quadrigemina ; 4 Fascia dentata cinerea, or fimbriata. crura superiora ; c. anteriora ; c. ad- 5 Medulla centralis, or ciliaris. scendentia ; commissura cerebelli et 6 Corpus dentatum, denticulatum, cerebri; brachia conjunctoria, or copu- rhomboideum, ciliare, or mixtum; nu- lativa; processus cerebelli ad testes; cleus dentatus, rhomboidalis, lenticula- processus ad testes ; columnae valvulas tus, fimbriatus, or centralis ; ganglion Vieussenii ; oblique intercerebral com- missures. THE NERVOUS SYSTEM. 529 named the valve of the brain. 1 This so-called valve is attached at all its borders, and is situated over the fourth ventricle. Upon its upper surface a tongue-like process 2 of gray substance, transversely ridged, is extended from the cerebellum. The Inferior peduncles of the cerebellum, 3 smaller than the others, are two narrow, white bands, which proceed from the interior of the hemispheres, and descend to become continuous with the restiform bodies of the medulla oblongata. THE PONS. The Pons 4 is a quadrate white body, situated back of the middle of the base of the cerebrum, and in advance of the cerebellum. It rests on the upper part of the basilar process of the occipital bone, and the de- clivity of the sphenoid bone. Its under surface is convex and trans- versely striated, 5 and its anterior and posterior borders are rounded. Along the median line of the under surface it presents a shallow groove, 6 which accommodates the basilar artery, and also exhibits small perfora- tions transmitting branches of the latter. The superficial- or lower portion of the pons is composed of transverse nerve fibres, which at the sides diverge as the crura or middle peduncles of the cerebellum. The association of the hemispheres of the cerebellum through its middle peduncles is the origin of the name pons, signifying a bridge, though the term is extended in its application to the deeper parts, or those within the superficial portions of the structure. The latter, which constitutes a transverse commissure conjoining the hemispheres of the cerebellum, depends on these for its existence ; and therefore in birds, in which the cerebellar hemispheres do not exist, the transverse commis- sural portion of the pons is absent. 1 Valvula cerebelli ; v. Vieusseriii ; v. 4 Pons Varolii ; p. cerebelli ; nodus Willisiana ; v. cerebri ; v. magna cere- encephali ; n. cerebri ; protuberantia bri; velum medullare anterius; v.Vieus- annularis ; p. a. Willisii ; p. basilaris; senii; v. interjectum cerebelli; v. apo- annular protuberance; processus, emi- physi vermiformi obtentum; lacunar nentia, or prominentia annularis ; tuber ventriculi quarti superior. annulare ; corpus annulare ; commissura 2 Lingula; linguetta laminosa. hemisphseriorum cerebelli; c. cerebelli; 3 Pedunculi cerebelli sensu strictiori; mesocephalon; Varoli's bridge; cerebral crura cerebelli ad medullam oblongatam ; protuberance. c. c. ad medullam spinalem ; crura infe- ^ Sulci transversi ; s. obliqui ; s. mi- riora ; c. posteriora. nores pontis. 6 Sulcus basilaris. 34 530 THE NERVOUS SYSTEM. From the front of the pons, the crura of the cerebrum appear to emerge, and this is found actually to be the case on removal of the superficial portion of the pons ; for within this, longitudinal fasciculi of fibres, intermingled with gray matter, extend from the medulla oblongata upward to become continuous with the cerebral crura. THE MEDULLA OBLONGATA. The Medulla oblonga'ta 1 is the smallest of the four divisions of the brain, and is a white, pyriform body, situated in front of the cerebellum, and extending from the pons to the spinal cord, with which it is con- tinuous. It is a little over an inch in length, and rests in the groove of the basilar process of the occipital bone. It is divided into two lateral portions by an anterior and a posterior median fissure, continuous below with the corresponding fissures of the spinal cord. The medulla oblongata is further divided on each side into the pyram- idal, olivary, and restiform bodies, and the posterior pyramids. The Pyram'idal bodies 2 appear on each side of the anterior median fissure as a club-shaped, white mass, continuous below with the anterior and lateral columns of the spinal cord. Their upper and thicker ex- tremity is rounded, and is connected with the pons. At the lower part of the median fissure portions of the white sub- stance of the pyramidal bodies cross from side to side, producing the decussation of the pyramids. 3 In structure the pyramidal bodies are three-sided prismatic bundles of nerve fibres, ascending from the anterior and lateral columns of the spinal cord to the pons. The inner fibres ascend from the lateral columns of- the cord, and cross to the opposite side, thus producing the decussa- tion above mentioned ; the lateral fibres ascend from the anterior col- umns of the spinal cord of the same side. The Ol'ivary bodies 4 appear as oval, white prominences to the outer side of the pyramidal bodies. They are composed of white substajice, and contain a plicated, pouch-like layer of gray substance. In section 1 Bulbusrachidicus; caudex encephali s Decussatio pyramidum; decussation communis; medulla respiratoria ; ob- of Mistichelli. long medulla ; cerebrum elongatum ; 4 Corpora olivaria ; eminentiee oliva- centrum vitale. res ; e. ovales ; e. o. laterales ; olivse ; 2 Corpora pyramidalia; c. p. anteri- corpora ovata, or semiovalia; funiculi, ora ; c. p. interna ; eminentise pyramid- or fasciculi ovales. ales ; e. oblongae ; e. medianae internes. THE NERVOUS SYSTEM. 531 the latter gives the central mass of the olivary bodies the appearance of an indented oval nucleus, whence its name of the dentated body. An additional small accumulation of gray substance within the olivary bodies, distinct from the former, is named the accessory olivary nucleus. The white substance of the olivary bodies is continuous with that of the anterior columns of the spinal cord, and forms a fasciculus, which may be traced through the pons to the crura of the cerebrum and the quadrigeminal body. The Res'tiform bodies, 1 situated to the outer side, posteriorly, of the olivary bodies, ascend from the spinal cord in a divergent manner, and become continuous with the inferior peduncles of the cerebellum. They are composed of white substance continuous with that of the spinal cord, and contain some gray substance 2 continuous with the posterior horns of the latter'. The Posterior pyramids 3 are situated behind the preceding bodies, on each side of the posterior median fissure, and diverge at the sides of the fourth ventricle. They consist of two narrow fasciculi of white sub- stance, continuous with the posterior median columns of the spinal cord, and appear to merge in the inferior peduncles of the cerebellum. At the sides of the medulla oblongata, below the olivary bodies, or even crossing their lower part, there usually exist some arching fibres connecting the pyramidal and restiform bodies, and named arciform fibres. 4 Other fibres also pass transversely from before backward, within the median fissures of the medulla oblongata, and are named septal fibres. FOURTH VENTRICLE. The triangular space included between the medulla oblongata and pons in front, and the cerebellum behind, is called the fourth ventricle. 5 1 Corpora restiformia ; pyramides 3 Fasciculi graciles. laterales ; fasciculi, or funiculi pyra- 4 Fibrae transversae arciformes ; stra- midales; fasciculi laterales et cuneati; turn zonale medullse oblongatae ; pontl- corpora pyramidalia posteriora; pro- culus. cessus a cerebelli ad medullam oblonga- 5 Ventriculus quartus ; v. Arantii ; v. turn; peduncles of the medulla oblongata; calami- scriptorii ; v. rhomboidalis ; v. inferior peduncles of the cerebellum. cerebelli ; ventricle of the cerebellum. 2 Nucleus, or corpus cinereus ; par- tially the tubercula cinerea of Rolando. 532 THE NERVOUS SYSTEM. It communicates, by a narrow passage 1 ascending beneath the quadri- geminal body, with the third ventricle, and is lined with a delicate serous membrane, continuous with that of the latter cavity, and opening below into the subarachnoid space of the spinal cord. The posterior sloping roof of the fourth ventricle is formed by the superior peduncles of the cerebellum, and the intervening "valve" of the brain. Its sides, posteriorly, are formed by the inferior peduncles of the cerebellum. The anterior part, or floor of the fourth ventricle, 2 is formed by the back of the medulla oblongata and pons. It is lozenge shaped in out- line, and is bounded laterally above by the superior peduncles of the cerebellum ; below by the inferior peduncles, the restiform bodies, and posterior pyramids. The sides of the floor incline to the posterior me- dian fissure, 3 which is continuous below with that of the spinal cord, and becomes obsolete above. The surface of the floor is rendered uneven by several slight convex eminences, 4 and is invested with a layer of gray substance 5 continuous with that of the spinal cord. On each side it is crossed by a series of transverse white lines 6 which are connected with the origin of the audit- ory nerves. At the lower angle 7 of the floor is a small pit, 8 which is the upper ex- tremity of a canal 9 existing during foetal life along the centre of the spinal cord. The lower portion of the fourth ventricle is closed by the arachnoid membrane, but, as previously indicated, it communicates with the sub- arachnoid space of the spinal cord. 1 Meat us conjunctorius ventriculi nentise cuneiformes cinereae ; alas cine- quarti ettertiimedii; aquseductus Sylvii; reae, or folia cinerea lanceolata. iter e tertio ad quartam ventriculam. 5 Comprising the substantia cinerea 2 Sinus, fovea, fossa, or cavitas rhom- ochracea ; locus cinereus, or cceruleus, boidalis ; scrobs, or fovea ventriculi or substantia ferruginea ; and the fasci- quarti; area, or semicanalis medullae olae cinereae. oblongatae. 6 Striae, toaniae, or fibrae medullares, 3 Sulcus, or fissura longitudinalis ; s. or acusticae; fasciculi et fibrillge filiforines or f. medius fossas rhomboidalis. nervi acustici. 4 These comprise 1, the eminentiae 7 Calamus scriptorius. teretes, semiteretes, perpendiculares, or 8 Ventriculus Arantii. longitudinales ; funiculi, or fasciculi te- 9 Canalis medullae spinalis. retes, or the corpora teretia; 2, the emi- THE NERVOUS SYSTEM. 533 THE SPINAL CORD. The Spinal cord, 1 the centre of excito-motor impulses, with its mem- branes, occupies the vertebral canal. It is continuous with the medulla oblongata, and extends from the occipital foramen to the lower part of the first lumbar vertebra. In the embryo the spinal cord corresponds in length with the verte- bral column, but subsequent to the third month the latter grows more rapidly than the former, so that at birth the cord extends only as far as the third lumbar vertebra. The length of the spinal cord of the adult is from fifteen to eighteen inches, and its weight about an ounce and a half avoirdupois. In gen- eral form it is cylindrical, compressed from before backward, and it varies in diameter in different positions. In the region of the neck it presents the cervical enlargement 2 extending from about the third cervical to the first dorsal vertebra. Below this position it is of nearly uniform diameter, until it forms the lumbar enlargement, 3 which is opposite the last dorsal vertebra, and subsequently it tapers to a conical point. 4 The cervical and lumbar enlargements correspond with the large nerves connected with these portions of the spinal cord. Where other nerves emanate from the latter, it exhibits slight enlargements, which give to the sides of the cord a somewhat undulating appearance. Exteriorly the spinal cord is composed of white nerve substance ; in- teriorly, of gray substance the former being the more abundant, espe- cially in the cervical region. In front and behind, the spinal cord is divided by fissures into lateral symmetrical halves. The anterior median fissure 5 penetrates about one-third the thickness of the cord, but becomes deeper toward its lower extremity. The white substance at its bottom associating the two sides of the cord is named the anterior or white commissure. 6 The posterior median fissure, 7 narrower, and for the most part deeper than the anterior, becomes shallower toward its lower end. 1 Medulla spinalis : spinal marrow ; 3 Intumescentia lumbaris, or cruralis. corda spinalis; medulla dorsalis; m. * Conus medullaris ; c. terminalis me- spinae ; caudex dorsalis ; funiculus spi- dullae spinalis. nalis ; cerebrum longum, or oblongum ; 5 Fissura longitudinalis anterior, or nucha ; myelus ; myelon ; notomyelus ; mediana. rhacites ; rhachetrum ; processus rachi- 6 Commissura anterior. dianus; funis argenteus; sacra fistula; 7 Fissura longitudinalis posterior; sul- vertebral marrow. cus longitudinalis medianus ; fis. long. 2 Intumescentia cervicalis. post, superior et inferior. 534 1HE NERVOUS SYSTEM. From each side of the cord, the spinal nerves originate by a series of anterior and posterior roots, the attachments of which give rise to slight furrows named the anterior and posterior lateral fissures, 1 Of these the posterior is the more evi- dent from the gray substance of the interior of the cord extending to its bottom, so as to isolate the white substance of the posterior part of the cord from the antero- lateral part. The fissures of the spinal cord have led to its division into col- umns. The portions included be- tween the anterior median fissure and the antero-lateral fissures con- stitute the anterior columns; 2 those at the sides between the lat- eral fissures or the roots of the spinal nerves are the lateral columns ; 3 and those between the posterior median and postero-lateral fissures are the posterior columns. 4 In con- sequence of the feebly-marked character of the antero-lateral fissures, the anterior and lateral portions of the cord are usually referred to under the name of the antero-lateral columns. At the upper part of the cord, a pair of narrow, white tracts are ob- served separated by the posterior median fissure. These are named the posterior median columns, 5 and are continuous with the posterior pyra- mids of the medulla oblongata. In a transverse section of the spinal cord, the gray substance is noticed to be arranged in the form of two irregular crescentoid bars, situated one on each side, with their convexities conjoined by a transverse bar. The extremities of the crescentoid bars are called horns, 6 and the inter- vening transverse bar is the posterior or gray commissure. 7 The anterior horns 8 are short, broad, and obtuse, and are inclosed SEGMENT OF THE SPINAL CORD. 1, anterior median fissure; 2, posterior median fissure; 3, postero- lateral fissure ; 4, antero-lateral fissure ; 5, anterior column ; 6, lateral column ; 7, posterior column ; 8, anterior commissure ; 9, anterior horns of the gray substance : 10, posterior horns; 11, gray com- missure ; 12, anterior root of a spinal nerve spring- ing by a number of filaments from the antero- lateral fissure; 13, posterior root from postero- lateral fissure ; 14, ganglion on the posterior root ; 15, spinal nerve formed by the union of the two roots. 1 Fissura lateralis anterior et poste- rior. 2 Funiculi anteriora. 3 Funiculi lateralia. 4 Funiculi posteriora. 5 Fasciculi graciles. 6 Cornua ; crura. 7 Commissura cinerea. Its central portion is the nucleus cinereus; centrum cinereum; commissura gelatinosa ; sub- stantia grisea centralis ; gray central nucleus ; gelatinous central cord of the gray commissure. 8 Cornua anteriora. THE NERVOUS SYSTEM. 585 within the autero-lateral columns of the cord. The posterior horns 1 are longer and narrower, and are capped at the extremity by a more trans- lucent portion of the gray substance, called the gelatinoid substance. 2 They separate the antero-lateral from the posterior columns, and reach the bottom of the postero-lateral fissures. Toward the lower extremity of the spinal cord, the crescentoid appear- ance of the lateral bars of gray substance becomes indistinct, and the relative quantity of the white substance is diminished. MEMBRANES OF THE BRAIN AND SPINAL CORD. THE PIA MATER. The Pia mater 3 is a delicate fibro-vascular membrane closely investing the brain and spinal cord, contributing' to sustain their structure, and serving as a point of departure and termination to their numerous capil- lary blood-vessels. PIA MATER OP THE BRAIN. The branches of the internal carotid and vertebral arteries destined to supply the brain with blood, by frequent anastomosis form upon its sur- face an intricate net-work. This vascular net, in conjunction with numerous veins, and strengthened with delicate, interlacing bundles of fibrous tissue, constitutes the pia mater of the brain. Processes of the membrane extend into all the fissures of the brain, and its vessels supply and return the blood of the capillaries of the latter. When the pia mater is detached, the torn capillaries from the brain give its inner sur- face a flocculent appearance. A process of the pia mater, named the interposed velum, 4 dips from between the cerebrum and cerebellum, beneath the posterior border of the corpus callosum, and above the quadrigeminal body, into the third ventricle. The velum extends along the under surface of the fornix, and has the same form. In the median line it incloses the two ventricular veins, which lie parallel to each other, and end in a short trunk 5 which opens into the straight sinus of the dura mater. On each side the velum projects beyond the lateral borders of the for- 1 Cornua posteriora. inner lamina of the meninges ; tunica 2 Substantia cinerea gelatinosa. cerebri et medullas spinalis propria. 3 Pia meninx; mollis, or tenuis mater; 4 Velum interpositum, triangulare, or tunica, or meninx interior, vasculosa, or choroides ; tela choroidea ; t. c. supe- choroides; membrana vasculosa cerebri; rior; plexus choroideus medius; rete m. cerebri tenuis, mollis, or propria; mirabile; r. choroideum. 5 Vena Galeni. 536 THE NERVOUS SYSTEM. nix, and forms the choroid plexuses of the lateral ventricles. 1 These plexuses are two remarkable vascular appendages, which resemble in ap- pearance pieces of knotted red worsted cord. They extend from the foramen beneath the anterior crura of the fornix, along the floor of the lateral ventricles at the side of the latter, and descend to the bottom of the middle horns of the ventricles. Narrow at their commencement, they increase in bulk until they reach the middle horns of the lateral ventricles, and then decrease to their termination. In structure the cho- roid plexuses consist of portions of the interposed velum, furnished with many villous processes, and containing tortuous blood-vessels. The villous processes, in an advanced period of life, are frequently found more or less dilated into spherical bodies, from the size of a pin-head to that of a pea, and have been mistaken for hydatid parasites. On the under surface of the interposed velum are situated the choroid plexuses of the third ventricle. 2 These are two narrow, vascular ap- pendages, extending from those of the lateral ventricles backward along the course of the ventricular veins. The choroid plexuses of the fourth ventricle 3 extend from the pneu- mogastric lobule of the cerebellum, join each other across the vermiform process, and are prolonged a short distance along the sides of the latter. Connected with the pia mater at the borders of the great longitudinal fissure, there is found a variable number of coarse, rounded granules, called Pacchio'nian bodies. 4 These are usually collected in groups, and frequently protrude through openings of the dura mater into the longi- tudinal sinus. The openings just indicated appear to result from pres- sure of the Pacchionian bodies, and absorption of the contiguous osse- ous wall of the cranium is also occasionally produced by them. They were formerly supposed to be glandular in character, but as they do not exist at birth, they are perhaps to be viewed as a pathological produc- tion, notwithstanding their frequency. PIA MATER OF THE SPINAL CORD. The pia mater of the spinal cord has fewer vessels and more fibrous tissue entering into its composition than that of the brain, and therefore appears denser, stronger, and less vascular. Thin pro- cesses of the membrane dip into the anterior and posterior median 1 Plexus choroideus, or choroides ; p. 3 Plexus choroideus ventriculi quarti. c. lateralis dexter et sinister: p. choroi- *Glandula3 Pacchionii; glands of Pac- forines ; p. reticularis ; p. reteformes ; chioni ; glandulae durse matris ; g. durae p. glandulares ; vermes cerebri ; retia meningis ; tubercula parva ; corpora mirabilia. glandiformia ; cerebral granulations. 2 Plexus choroideus ventriculi tertii. THE NERVOUS SYSTEM. 537 fissures. In front it exhibits a longitudinal fibrous band, 1 and on each side, between the roots of the spinal nerves, it forms the denticulate liga- ment. 2 This is a projecting fibrous band deeply toothed in a saw-like manner at its outer part, the points of the dentations being attached to the dura mater in the intervals of the spinal nerves. From the lower end of the spinal cord the pia mater is continued, as a partially hollow, thread-like prolongation, 3 to the termination of the vertebral canal, where it is attached to the dura mater. The hollow of the prolongation is apparently occupied by a continuation of the gray substance of the spinal cord. THE EPENDYMA. The Epen'dyma 4 is the delicate, transparent, serous membrane, lining the ventricles of the brain and the central canal of the spinal cord of the embryo. At birth its epithelium consists of ciliated cells, but at a later period the cilia are obliterated. THE DURA MATER. The Dura mater, 5 the exterior investment of the brain and spinal cord, is a dense, strong, inextensible bluish-white membrane, composed of an intertexture of bundles of fibrous tissue. DURA MATER OF THE BRAIN. 6 This consists of two intimately adherent layers, of which the outer corresponds with the periosteum in other parts of the skeleton, while the inner alone corresponds with the spinal dura mater. The adhesion of the dura mater to the inner surface of the cranium depends on the many minute blood-vessels and fibrous processes passing between the two. The connection is closest along the sutures, and at the borders of the foramina, and is especially well marked at the base of the cranium. The inner layer of the dura mater has a smooth internal surface closely invested by the arachnoid membrane. Between the cerebrum and cere- bellum and their hemispheres it sends strong partitions which contribute to sustain the mass of the brain. 1 Linea splendens Halleri. 5 Dura meninx; meninx exterior; m. 2 Ligaraentum denticulatum ; 1. serra- sclera ; m. dennatodes ; m. pacheia ; turn ; 1. dentatum ; membrana dentata. crassa meninx ; cuticularis membrana ; 3 Fibrum terminale; nervus impar. membrana externa; m. dura; m. fibrosa. 4 Endyma, or indumentum ventriculo- 6 Dura mater cerebri ; d. m. sensu rum. strictiori ; d. membi'ana cerebrum am- biens. 538 THE NERVOUS SYSTEM. The Cer'ebral falx, 1 one of the partitions just indicated, occupies the great longitudinal fissure, and separates the hemispheres of the cere- brum. Commencing at the ethmoidal crest, to which it tightly adheres, it extends along the course of the superior longitudinal sinus, gradually increasing in breadth until it joins the tentoriurn. It is thus shaped like a sickle, from whence its name is derived. The Cerebel'lar falx 2 is a thick fold of the dura mater occupying the valley, and separating the hemispheres of the cerebellum. It extends from the tentorium downward to the" occipital foramen. The Tento'rium 3 is a broad partition of the dura mater separating the cerebrum from the cerebellum. It is continuous along its median line with the cerebral falx, from which it inclines on each side downward, outward, and backward. It is attached along the horizontal limbs of the occipital cross, and the superior border of the petrous portion of the temporal bones, extending to the posterior clinoid processes. Its inner border includes a large oval space 4 through which the cerebral crura diverge from the pons to the hemispheres of the cerebrum. Through separation of the layers of the dura mater in certain po- sitions, channels are formed named the sinuses of the dura mater. These perform the office of veins, and are lined with a continuation of the ordinary epithelium of blood-vessels. In them terminate the veins of the pia mater, which return the blood from the capillary vessels of the brain. The superior longitudinal, straight, and lateral sinuses are three sided, from their occupying the angular intervals along the lines of departure of the cerebral falx and tentorium. The remaining sinuses, smaller than those just mentioned, are generally cylindroid, and occupy the base of the cranial cavity. A description of the course of the sinuses of the dura mater is given in the account of the venous system, page 409. The meningeal arteries of the dura mater, which give rise to the ar- borescent channels on the interior surface of the cranium, not only sup- ply the membrane, but are also destined to supply the bones of the latter. 1 Falx cerebri, major, or magna; pro- 3 T. cerebelli; t. cerebello super ex- cessus falciformis cerebri ; septum, or tensum ; tentaculum cerebelli ; septum mediastinum cerebri; vertical superior encephali; diaphragma cerebri; inter- longitudinal process. septa horizontalia Pacchioni ; processus 2 Falx cerebelli ; f. minor ; processus transversus ; lateral processes ; trans- falciformis cerebelli ; septum cerebelli ; verse septum. s. parvum occipitale ; median septum of 4 Incisura tentorii. the cerebellum. THE NERVOUS SYSTEM. 539 In the passage of vessels and nerves through foramina at the base of the cranium, the dura mater becomes continuous with their fibrous sheaths. DURA MATER OP THE SPINAL CORD. 1 This corresponds alone with the internal layer of the dura mater of the brain, with which it is continuous through the occipital foramen. Firmly attached to the border of the latter, the spinal dura mater ex- tends to the end of the vertebral canal, and forms a loose sheath for the spinal cord and its nerves. It is unattached to the periosteum of the vertebral canal, except at the occipital foramen, the interval of the two membranous layers being occupied by the intra-spinal plexus of veins, together with some loose areolar and adipose tissue. Opposite the intervertebral foramina the dura mater is pierced sepa- rately by the roots of the spinal nerves, but prolongations of the mem- brane extend as sheaths of the latter and become firmly attached to the periosteum bordering the intervertebral foramina. THE ARACHNOID MEMBRANE. The Arach/noid membrane 2 is a delicate, transparent, and colorless, serous tunic, intervening between the pia mater and the dura mater. Its reflected portion adheres closely to the internal surface of the latter membrane ; while its investing portion is connected with the pia mater without dipping into any of the fissures or depressions of the brain and spinal cord, except those which receive the cerebral falx, the cerebellar falx, and the tentorium. The arachnoid membrane is especially remarkable among serous mem- branes from its loose attachment to the structure beneath. Being con- nected with the pia mater by scattered bands of fibrous tissue and blood-vessels, an interval is left between the two membranes, called the subarach'noid space. This varies in extent in different positions, but is most capacious along the middle part of the base of the brain, at the bottom of the superior longitudinal fissure, and on the spinal cord. A serous fluid, the cer'ebro-spinal liquid, amounting to several ounces, occupies both the cavity of the arachnoid membrane and the subarachnoid space. The bottom of the fourth ventricle is closed by the arachnoid mem- brane, but the cavity of the former communicates with the subarachnoid space. 1 Dura mater spinalis ; pars spinalis durae matris. 2 Membrana, or tunica arachnoidea; m. media; t, mucosa; t. serosa; t. aranea ; t. crystallina ; meninx media ; m. serosa ; meningion. 540 THE NERVOUS SYSTEM. The roots of the cerebro-spinal nerves are loosely invested with tubu- lar sheaths of the arachnoid membrane, extending from the pia mater to their exit through the dura mater. THE NERVES OF THE BRAIN, OR THE CEREBRAL NERVES. The Nerves of the Brain, usually called the Cerebral nerves, 1 consist of twelve pairs, 2 and are either named numerically from before backward, or from their function, destination, or other special character. THE OLFACTORY, OR FIRST PAIR OF NERVES. The Olfactory nerves 3 are situated beneath the anterior cerebral lobes, and appear rather as appendages of the brain than as true nerves. They are small in comparison with those of most lower mammals, in accordance with the less acute sense of smell in man. They occupy a groove a short distance from the longitudinal fissure, and rest in the ethmoidal gutters. Each nerve is a club-shaped body, with a three-sided handle or ped- icle, and an oval head or bulb, The pedicle of the olfactory nerve is composed of white substance or nerve fibres below, and of gray substance above. The nerve fibres orig- inate by a pair of roots 4 converging from the sides of the anterior per- forated space at the inner part of the Sylvian fissure ; the gray substance communicates by a single root 5 with the space just mentioned. The bulb 6 forms the free extremity of the olfactory nerve anteriorly. It is oval, soft, and composed of gray substance. From it emanate many branches, 7 which descend through the foramina of the cribriform plate of the ethmoid bone to be distributed to the mucous membrane of the upper part of the nose. 1 Cranial, or encephalic nerves. lie nerves ; nerves of smelling, or olfac- 2 Nine pairs of Willis. tion. 3 Nervi olfactorii ; n. odoratorii ; pro- * Radix externa, or longa, and radix cessus mammillares ; p. m. cerebri ad interna, or brevis. nares ; p. papillares ; carunculge mam- 5 Radix media, grisea, or superior, millares ; ethmoidal nerves ; par primum G Bulbus olfactorius ; b. cinereus ; ol- nervorum cerebri ; first pair of encepha- factory tubercle or lobe. 7 Nervi olfactorii; rami bulbi. THE NERVOUS SYSTEM. 541 THE OPTIC, OR SECOND PAIR OF NEEYES. The Optic nerves, 1 among the largest of those of the brain, originate each in a white band, named the optic tract. 2 This starts from the quadrigerninal and geniculate bodies, winds around the outer side of the crus of the cerebrum, and converges to join that of the opposite side in front of the base of the infundibulum. The conjunction of the tracts forms the optic commissnre, 3 from which the optic nerves diverge to pass through the optic foramina into the orbits. The optic tracts and commissure throughout their course intimately adhere to the contiguous structures of the brain, from which they receive additional nerve fibres. In the optic commissure some of the nerve fibres cross from one side to the other, or decussate ; another set proceed directly from the optic tracts to the corresponding nerves ; a third series, in the form of loops, appear to associate the tracts together ; and a fourth series, in the same manner, conjoin the two nerves independently of the tracts. The optic nerves are those of vision, and terminate in the retina of the eyeball. THE OCULO-MOTOR, OR THIRD PAIR OF NERYES. The Oc'ulo-motor nerves 4 ap- FIG. 332. pear at the surface of the brain, springing from the inner side of the cerebral crura, just in advance of the pons. Their nerve fibres are OCULO-MOTOR AND ABDUCENT NERVE, the upper part of the right orbit removed. 1, oculo-motor nerve ; 2, 3, branch to the superior straight and oblique muscles ; 4, 5, branches to the internal and inferior straight muscles; 6, branch to the inferior oblique muscle ; 7, branch from the latter to the ophthalmic ganglion ; 8, abducent nerve to the ex- ternal straight muscle ; 9, communicating filaments between the abducent nerve and the carotid plexus of the sympathetic. To their outer side is the tri- facial nerve. 10, ciliary nerves perforating the sclerotic coat of the eyeball, and passing forward between it and the choroid to the ciliary muscle and iris. traceable to the gray substance in the interior of the crura of the cer- ebrum and the pons. 1 Nervi optici ; n. visorii ; par secun- dum, opticum, or visorium ; ocular nerves ; nerves of sight or vision. 2 Tractus opticus. 3 Chiasma, or commissura nervorum opticorum. 4 Nervi oculo-motores; n. motores ocu- lorum ; n. oculares communes ; n. oph- thalmic! externi ; common oculo-muscu- lar nerves ; par tertium. 542 THE NERVOUS SYSTEM. Passing obliquely forward and outward, the oculo-motor nerve pierces the dura mater in front of the posterior clinoid process, and, after travers- ing the outer wall of the cavernous sinus, it divides into two branches, which enter the orbit through the sphenoidal foramen. Of the two branches, the upper and smaller is distributed to the pal- pebral elevator and superior straight muscles ; while the lower one sup- plies the internal and inferior straight and the inferior oblique muscles, and is connected by a short branch 1 with the ophthalmic ganglion. The name of the oculo-motor nerve indicates its function. THE PATHETIC, OR FOURTH PAIR OF NERVES. The Pathetic nerves, 2 the smallest of those connected with the brain, start from the upper part of the " valve of the brain," immediately behind the quadrigeminal body. Their fibres are traceable to the gray substance of the pons and the floor of the fourth ventricle. Each pathetic nerve appears like a white thread winding around the outer side of the crus of the cerebrum. Piercing the dura mater just behind the oculo-motor nerve, it accompanies this through the outer wall of the cavernous sinus and the sphenoidal foramen into the orbit." It is motor in its function, and is distributed to the superior oblique muscle of the eye. THE TRIFACIAL, OR FIFTH PAIR OF NERVES. The Trifa'cial nerves 3 are the largest of those derived from the brain. They arise by two roots of unequal size, which emerge from the side of the pons at its fore part inferiorly. The large root 4 of the trifacial nerve, sensory in its function, consists of numerous bundles of nerve fibres, which may be traced through the pons into the restiform body and the gray substance of the floor of the fourth ventricle. The small root, 5 motor in its function, though trace- able through the pons to the medulla oblongata, has not had its origin satisfactorily determined. The two roots of the trifacial nerve, the smaller concealed behind the large one, pass through an oval aperture of the dura mater, near the 1 Radix brevis ganglii ciliaris ; short par trigeminum ; par trium funiculorum. root of the ophthalmic ganglion. Sing. : n. divisus ; n. trimellus ; n. mix- 2 Nervi pathetici; n. trochleares ; n. tus ; n. quintus ; n. sympatheticus me- oculo-musculares superior, minimi, or dius ; n. anonymus ; n. innominatus. interni; par quartum. 4 Radix major, posterior, inferior, or 3 N. trifaciales ; n. trigemini ; trigem- longior. inal nerves ; n. gustatorii ; par quintum ; 6 Radix minor, anterior, or superior. THE NERVOUS SYSTEM. 543 apex of the petrous portion of the temporal bone. The large root terminates in the semilunar ganglion, which rests in a slight depression in front of the apex of the petrous portion of the temporal bone ; while the small root passes beneath the ganglion, and simply lies in contact with.it. The- semilunar ganglion 1 of the trifacial nerve is a large crescentic body, with its concavity upward, and receiving the diverging fibres of the large root of the nerve. From its convexity emanate the ophthalmic and superior maxillary nerves, and a third branch, which joins the small root of the trifacial to form the inferior maxillary nerve. THE OPHTHALMIC NERVE. 2 FIG. 333. This is the first division of the trifacial nerve, and the smallest branch from the semilunar gan- glion. After traversing the outer wall of the cavernous sinus, it di- vides into three branches, which pass through the sphenoidal foramen into the orbit. TRIFACIAL NERVE, the upper part of the orbit and temporal fossa re- moved. 1. semihinar ganglion; 2, ophthalmic nerve; 3, lachrymal nerve; 4, frontal nerve; 5, 6, its two principal branches; 7, a branch passing from the orbit above the pulley of the superior oblique mus- cle ; 8, nasal nerve ; 9, its exter- nal nasal branch ; 10, course of the internal nasal nerve from the orbit into the cranium, and nose; 11, 12, 13, temporal branches of the inferior maxillary nerve; 14, com- mencement of the auriculo-tempo- ral nerve; 15, greater petrosal . nerve; I, olfactory nerve; II, optic nerves; III, oculo-motor nerve; IV, pathetic nerve to the superior ob- lique muscle of the eye; V, trifacial nerve; its small root visible beneath the cut end of the large root, which forms the semilunar ganglion dividing into the ophthalmic, superior and inferior maxillary nerves; VI, abducent nerve; VII, facial, included inagroove of the auditory nerve, VIII, both entering the auditory meatus; IX, glosso-pharyngeal, X, pneumogastric, and XI, accessory nerves emerging at the jugular foramen; XII, hypoglossal nerve. 1 G. semilunare; g. Gasseri; Gasserian ganglion; ganglion of Gasser; intumes- centia, or moles gangliformis; i. semilunaris; taenia nervosa Halleri; ganglion of the fifth nerve. 2 Nervus ophthalmicus ; n. orbito-frontalis. 544 THE NERVOUS SYSTEM. The Lach/rymal nerve, 1 one of the branches of the ophthalmic, passes along the outer part of the orbit to be distributed to the lachrymal gland and upper eyelid. The Frontal nerve, 2 the largest branch of the ophthalmic, passes along the roof of the orbit, and divides into two branches, of which one 3 emerges at the supra-orbital foramen, the other 4 between the latter and the pulley of the superior oblique muscle, and both are distributed to the skin and muscles of the forehead and upper eyelid. The Nasal nerve, 5 the remaining branch of the ophthalmic, passes above the optic nerve and along the inner side of the orbit to the anterior ethmoidal foramen, where it divides into the internal and external nasal nerves. In its course within the orbit it is connected by an anastomotic filament 6 with the ophthalmic ganglion, and gives off two or three ciliary nerves. 7 The internal nasal nerve 8 passes through the anterior ethmoidal fora- men and enters the cranium, when it proceeds forward to the most ante- rior of the foramina of the ethmoid bone, and descends to supply the mucous membrane at the fore part of the nose. The external nasal nerve 9 passes from the orbit beneath the pulley of the superior oblique muscle, and is distributed to the eyelids with their muscle, the lachrymal sac, and the skin of the nose. THE OPHTHALMIC GANGLION. 10 This is a small, reddish-gray body, situated at the back part of the orbit, between the optic nerve and the external straight muscle. It is imbedded in areolar and adipose tissue, and is connected by branches with the nasal nerve of the ophthalmic, the oculo -motor nerve, and the carotid plexus of the sympathetic. From its fore part emanate about a dozen cil'iary nerves. 11 These, together with the two or three ciliary branches from the nasal nerve, pierce the back part of the sclerotic coat, and advance between it and the choroid coat to be distributed to the ciliary muscle and iris. 1 Nervus lachrymalis. 7 Long ciliary nerves. 2 N. frontalis ; n. front o-palpebralis. 8 N. nasalis interims; n. ethmoidalis. 3 N. supra-orbitalis ; n. frontalis ex- 9 N. infra-trochlearis ; n. nasalis ex- ternus, or major. ternus. * N. supra-trochlearis ; n. frontalis in- 10 Ganglion ophthalmicum ; g. ciliare ; ternus, or minor. g. lenticulare ; g. semilunare ; g. orbi- 5 N. nasalis ; n. nasarius ; n. naso-ci- tale ; ciliary or lenticular ganglion, liaris ; n. naso-ocularis. n Short ciliary nerves ; nervi ciliares 6 Long root of the ophthalmic gan- breves, glion. THE NERVOUS SYSTEM. 545 OPHTHALMIC GANGLION THE OUTER PART OF THE RIGHT ORBIT REMOVED. I, optic nerve; 2, oculo-motor nerve; 3, branch to the superior straight and oblique muscles ; 4, branch to the in- ferior oblique muscle; 5, abducent nerve to the external straight muscle ; C, trifacinl nerve, its ganglion and three principal branches; 7, ophthal- mic nerve ; 8, nasal nerve ; 9, ophthal- mic ganglion; 10, its communicating branch with the oculo-motor nerve ; II, do. with the ophthalmic nerve; 12, do. with the carotid plexus of the sympathetic ; 13, the ciliary nerves ; 14, frontal nerve. FIG. 334. THE SUPERIOR MAXILLARY NERVE. 1 This is the second division of the trifacial nerve, and is intermediate in size and position to the others. Starting from the middle of the FIG. 335. SUPERIOR MAXILLARY NERVE THE EXTERNAL WALL OF THE LEFT ORBIT AND OF THE SUPERIOR MAXILLARY BONE REMOVED. I, superior maxillary nerve in its course through the infra-orbital canal; 2, 3, posterior dental nerves; 4, anterior dental nerve; 5, anastomosis between the dental nerves; 6, spheno-palatine ganglion; the branch from the superior maxillary nerve above is the commencement of the temporo-malar nerve; 7, pterygoid nerve ; 8, greater petrosal nerve joining the facial nerve ; 9, deep petrous nerve join- ing the carotid plexus of the sympathetic ; 10, abducent nerve with its communicating branches of the latter plexus; 11, superior cervical ganglion; 12, ascending branches to the carotid plexus; 13, facial nerve; 14, glosso-pharyngeal nerve; 15, the tympanic nerve; 16, branch to the carotid plexus ; 17, 18, 19, branches to the round and oval windows and Eustachian tube; 20, branch to the smaller petrosal nerve, 21. semilunar ganglion as a flattened cord, it assumes a rounded form, and passes from the cavity of the cranium through the rotund foramen of the sphenoid bone. It then crosses the upper part of the pterygo-max- Nervus maxillaris superior. 35 546 THE NERVOUS SYSTEM. illary fossa, and enters the infra orbital canal, 1 through which it advances to the face. In its course it gives off the temporo-malar, spheno-pala- tine, dental, and infra-orbital nerves. The Temporo-ma'lar nerve 2 enters the orbit through the spheno-max- illary foramen, and divides into filaments, which are transmitted by foramina of the malar bone to the skin of the temple and cheek. It anastomoses with the lachrymal and facial nerves. The Sphe'no-pal'atine nerves 3 are two short branches descending to join the spheno-palatine ganglion. The Dental nerves 4 consist of posterior and anterior branches. The posterior dental nerves, 5 of which there are two or three, descend behind the tuberosity of the superior maxillary bone, and enter small canals in the outer wall of the maxillary sinus to supply the back teeth. One of the branches also supplies the upper gum. The anterior dental nerve 6 comes off from the superior maxillary within the infra-orbital canal, and descends in the anterior wall of the maxillary sinus to supply the front teeth. The anterior and posterior dental nerves anastomose with one another, and also give branches to the lining membrane of the maxillary sinus. The Infra-orbital nerves 7 are the terminal branches of the superior maxillary, emerging at the infra-orbital foramen to be distributed to the lower eyelid, the upper lip, the side of the nose, and the mucous mem- brane of the cheek. THE SPHENO-PALATINE GANGLION. 8 This is a small, triangular body, situated in the pterygo-maxillary fossa, near the spheno-palatine foramen. It is joined by the spheno- palatine branches of the superior maxillary nerve, and besides giving small filaments 9 to the upper part of the pharynx, sends off the nasal, palatine, and pterygoid nerves. 1 Within which it is usually called the 6 N. dentalis, or alveolaris superior infra-orbital nerve ; nervus infra-orbi- anterior. talis. * N. infra-orbitales. 2 N. subcutaneus malae ; n. orbitarius. 8 G. spheno-palatinum ; g. pterygo- 8 Nervi spheno-palatini ; n. pterygo- palatinum; g. Meckelii; Meckel's gan- palatini. glion ; ganglion of Meckel ; g. nasale ; 4 N. dentales; n. d. superiores; n. al- g rhinicuni ; g. sphenoidale. veolares superiores. 9 Kami pharyngei. 5 N. dentales, or alveolares superiores posteriores. THE NERVOUS SYSTEM. 547 The Nasal nerves 1 consist of half a dozen or more small branches, which pass through the spheno-palatine foramen to supply the mucous membrane of the nose, including its partition, its outer wall, and the ethmoidal and sphenoidal sinuses. One 2 of the branches, descending obliquely on the partition, passes through the naso-palatine canal to the roof of the mouth. FIG. 336. VIEW OF THE SPHENO-PALATINE GANGLION, THE OUTER WALL OF THE LEFT NASAL CAVITY, AND THE OLFACTORY; NERVE. 1, olfactory nerve ; 2, nasal branch of the ophthalmic nerve; 3, spheno-palatine ganglion; 4,5, 6, palatine nerves; 7, branch to the nose; 8, nasal nerve to the outer wall of the nose; 9, do. to the inner wall ; 10, pterygoid nerve ; 11, facial nerve ; 12, deep petrous nerve joining the carotid plexus, 13 ; the other branch of the pterygoid is the larger petrosal nerve, which joins the facial. The Pal'atine nerves, 3 of which there are usually three, descend through the posterior palatine canal and its divisions to be distributed to the hard and soft palate, the palatine arches, the uvula, and the tonsil. From the largest palatine nerve, 4 in its course one or two branches 3 are given off to the outer wall of the nose. The Pter'ygoid nerve 6 proceeds from the spheno-palatine ganglion backward through the pterygoid canal of the sphenoid bone, and divides into two branches. One of these, the deep petrous nerve, 7 pierces the cartilage occupying the lacerated foramen, and joins the carotid plexus of the sympathetic nerve. The other branch, named the greater petro- 1 N. nasales superiores anteriores et posteriores, et naso-palatinus. 2 N. naso-palatinus ; n. naso-palatinus Scarpae ; n. septi narium. 3 N. palatini ; n. p. anterior et medius, posterior, or minus posterior et mini- mus exterior. 4 N. palatinus anterior, or major. 5 N. nasales inferiores. 6 N. pterygoideus ; n. Vidianus ; Vj- dian nerve ; n. recurrens Vidianus. 7 Ramus sympatheticus ; r. profundus nervi Vidiani. 648 THE NERVOUS SYSTEM. sal nerve, 1 enters the cranial cavity through the cartilage of the lacerated foramen, and passes into a canal on the front of the petrous portion of the temporal bone to join the facial nerve. THE INFERIOR MAXILLARY NERVE. 2 This is formed by the union of the small root of the trifacial nerve with the third branch of its semilunar ganglion. It is larger than the ophthalmic or superior maxillary nerve, and emerges from the cavity of the cranium through the oval foramen of the sphenoid bone. Imme- diately after its exit it separates into two divisions, of which the smaller receives nearly all the fibres of the small or motor root of the trifacial nerve ; while theMarger division receives most of the fibres emanating from the semilunar ganglion. The smaller division of the inferior maxillary nerve resolves itself into a number of muscular branches, 3 of which two 4 supply the tem- poral muscle, one 5 the masseter, one 6 the buccinator, and two 7 the ptery- goid muscles. The larger or sensory division of the inferior maxillary nerve is con- nected on its inner side with the otic ganglion, and divides into the auriculo-temporal, lingual, and inferior dental nerves. The Auric 'ulo-tem'poral nerve, 8 the smallest of the three branches just indicated, is directed outwardly between the ear and the articulation of the lower jaw, and ascends to be distributed to the skin of the temple. In its course it gives branches to the external ear, the articulation of the lower jaw, and the parotid gland ; and it anastomoses with the facial nerve. The Lin r gTial nerve 9 curves downward and forward between the pterygoid muscles to the side of the tongue, along which it continues to the tip, beneath the sublingual gland and in contact with the mucous membrane of the mouth. In its course it is joined by the tympanic branch 10 of the facial nerve, and gives small branches to the mucous 1 Greater superficial petrosal nerve ; 5 N. massetericus. nervus petrosus superficialis major ; n. 6 N. buccinatorius. superior, or superficialis nervi Vidiani. 7 N. pterygoideus internus et exter- 2 Nervus maxillaris inferior ; n. crota- nus. phitico-buccinatorius et maxillaris infe- 8 N. auriculo-temporalis ; n. tempora- rior; ramus tertius nervi quinti; third lis superficialis ; n. auricularis anterior, branch of the fifth, or trigeminal nerve. 9 N. lingualis ; n. gustatorius ; gusta- 3 Kami musculares. tory nerve. 4 N. temporalis profundus anterior et 10 Chorda tympani. posterior. THE NERVOUS SYSTEM. 549 membrane of the mouth, sublingual gland, and the submaxillary gan- glion. Its terminal branches perforate the muscular structure of the tongue, and ascend almost vertically to end in the papillae of taste. FIG. 337. DISTRIBUTION OF THE iNrERiOR MAXILLARY NERVE. 1, muscular branch to the masseter muscle; 2, 5, 7, branches to the temporal muscle ; 3, branch to the buccinator, anastomosing with one from the facial at 4; 6, external pterygoid muscle; 8, auriculo-temporal nerve; 9, brandies to the temple; 10, branches to the ear; 11, its anastomosis with the facial ; 12, lingual nerve ; 13, branch to the mylo-hyoid muscle from the inferior dental nerve, 14; 15, branches to the teeth; 16, terminal branches to the lower lip and chin. The Inferior dental nerve, 1 a little larger than the lingual, descends in company with it, but diverges to enter the dental canal of the inferior maxillary bone. In its course through the canal it supplies the lower teeth ; and it finally emerges at the mental foramen to be distributed to the lower lip and chin. Before entering the dental canal it gives a branch 2 to the muscles and skin of the floor of the mouth. 1 N. dentalis inferior; n. maxillaris inferior; n. mandibularis. 2 Ramus mylo-hyoideus. 550 THE NERVOUS SYSTEM THE OTIC GANGLION. This is a small, flattened, oval body, situated on the inner side of the sensory division of the inferior maxillary nerve, with which it is con- nected by several short filaments. Behind it is the great meningeal artery, and it is connected by a filament with the sympathetic plexus fol- lowing this vessel. It gives branches to the tympanic tensor and cir- cumflex palatine muscles, and an anastomotic filament to the auriculo- temporal nerve. From it emanates the small petro'sal nerve, 2 which enters the cranium through a fine canal in the spinous process of the sphenoid bone, and then traverses a canal in the front of the petrous portion of the temporal bone, to join the facial nerve and the tympanic branch of the glosso-pharyngeal nerve. THE SUBMAXILLARY GANGLION. 3 This is a minute body situated on the trunk of the lingual nerve, just above the submaxillary gland. It is connected by filaments with the lingual nerve, which are partly traceable to the tympanic branch of the facial. It is also connected with the sympathetic plexus of the facial artery, and sends all its branches to the submaxillary gland. THE ABDUCENT, OR SIXTH PAIR OF NERVES. The Abdu/cent nerves 4 appear at the surface of the brain, between the summits of the pyramidal bodies of the medulla oblongata and the pons. Their fibres, forming a large and small bundle, for the most part originate from the pyramidal bodies, a few being derived from the pons. The abducent nerve appears as a white thread, but is larger than the pathetic nerve. It proceeds forward, traverses the cavernous sinus, from the cavity of which it is separated by the lining membrane, and passes through the sphenoidal foramen into the orbit. In the cavernous sinus it lies at the outer side of the internal carotid artery, and is connected with its sympathetic plexus by a pair of filaments. In the orbit it passes between the two heads of the external straight muscle, to which it is distributed. 1 Ganglion oticum ; g. auriculare ; g. nus Meckelii ; plexus gangliosus sub- Arnoldi; ganglion of Arnold; otogan- maxillaris. glium ; g. maxillo-tympanicum. * Nervi abducentes. Sing. : nervus 2 Small superficial petrosal nerve; abducens; n. oculo-muscularus externus nervus petrosus superficialis minor. or posterior; n. ocularis externus; n. 3 G. submaxillare ; g. linguale ; g. mi- motor-oculi externus ; n. timidus. THE NERVOUS SYSTEM. 551 THE FACIAL, OB SEVENTH PAIR OF NERVES. The Facial nerves 1 emerge from the depression immediately back of the pons, between the olivary and restiform bodies. They have a large Fio. 338. THE FACIAL NERVE. 1, trunk of the nerve emerging at the stylo-mastoid foramen ; 2, its deep auricu- lar branch; 3, anastomosis of the latter with the great auricular nerve of the cervical plexus; 4, 5, 6, branches to the contiguous muscles; 7, 8, branches of the facial to the digastric and stylo-hyoid muscles ; 9, temporo-facial division of the nerve; 10, branch to the temple, anastomosing with the auriculo-temporal nerve; il, temporal branches; 12, /ygomatic branches; 13, infra-orbital branches; 14, 15, cervico-facial division of the facial nerve; 14, buccal branches; 16, inferior maxillary branches; 17, cervical branches ; 18, auriculo-temporal nerve; 19, 20, terminal branches of the frontal nerve; 21, terminal branch of the lachrymal nerve; 22, external nasal nerve; 23, branch of the temporo-malar nerve; 24, terminal branch of the internal nasal nerve; 25, infra-orbital nerves; 26, anastomosis between the buccal branch of the inferior maxillary nerve and the buccal branches of the facial nerve; 27, terminal branches of the infe- rior dental nerve; 28, great occipital nerve; 23,31, branches of the great auricular nerve; 30, small occipital nerve ; 32, superficial cervical nerve, anastomosing with the facial nerve. 1 Nervi faciales ; par septimum ; p. faciale. Sing.: portio dura nervi sep- timi; n. communicans faciei; n. primus paris septimi ; n. sympathetlcus parvus or minor ; ramus durior septimse conju- gationis; respiratory nerve of the face; portio dura nerve ; portio dura of the seventh pair of nerves. 552 THE NERVOUS SYSTEM. root whose fibres are derived from the restiform body, and a small root ' from the floor of the fourth ventricle. The two roots together accom- pany the auditory nerve, lying in a groove on its upper part, and pass down the internal auditory meatus. At the bottom of this passage the facial leaves the auditory nerve and enters the Fallopian canal, through the winding course of which it pursues its way to the stylo-mastoid foramen. At the position in which the Fallopian canal turns backward, the facial nerve presents a gangliform enlargement, 1 which is joined by the larger petrosal nerve, a branch of the smaller petrosal nerve, and a filament from the sympathetic plexus following the great meningeal artery. In the descending portion of the Fallopian canal the facial nerve sends a branch to the stapedius muscle, and gives off the tympanic nerve. 2 This enters the tympanum through a foramen near the pyra- mid, and proceeds forward to emerge at the glenoid fissure, from which it descends between the pterygoid muscles to join the lingual nerve. In its course it lies in contact with the tympanic membrane, between this and the handle of the mallet, and is separated from the cavity of the tympanum by its lining mucous membrane. Below the stylo-mastoid foramen the facial nerve gives branches to the digastric and stylo -hyoid muscles, anastomotic filaments to the auric- ulo-temporal nerve, and sends off the deep auricular nerve. 3 This ascends between the ear and the mastoid process, and is distributed to the muscles of the back of the ear and the occipital region. From the stylo-mastoid foramen the facial nerve turns forward through the parotid gland, and divides into numerous diverging branches, 4 which anastomose with one another on the side of the cheek, and are distrib- uted over the face, extending from the temple to the upper part of the neck. The branches of distribution form two groups, named the tem- poro-facial and cervico-facial divisions of the nerve. The Temporo-facial division of the facial nerve ramifies on the side of the face from the temple to the vicinity of the mouth, forming an intricate plexus, and anastomosing with the contiguous terminal branches of the trifacial nerve. Its branches, mainly distributed to the muscles of 'the temple, forehead, eyelids, cheek, nose, and upper lip, are named, from their special position, temporal, zygomatic, and infra-orbital. 1 Intumescentia gangliformis; gan- 3 Nervus auricularis profundus ; pos- glion geniculare. terior, or exterior. 2 Chorda tympani ; funiculus tympani. 4 Pes anserinus; plexus parotideus. THE NERVOUS SYSTEM. 553 The Cervico-facial division of the facial nerve is distributed to the lower part of the face and the upper part of the neck. Its upper or buccal branches anastomose with the lower ones of the preceding division, and supply the muscles of the cheek, nose, and upper lip. The inferior maxillary branches supply the muscles of the lower lip and chin, and anastomose with the inferior dental nerve. The cervical branches anastomose with the upper cervical nerves, and supply the subcutaneous cervical muscle. The facial nerve is the motor nerve of the face, and is the avenue through which its muscles are acted upon by the emotions. A few sen- sory filaments which it contains are derived through anastomosis with the pneumogastric and trifacial nerves. THE AUDITORY, OR EIGHTH PAIR OF NERV The Auditory nerves 1 have their origin in the transverse white striae of the floor of the fourth ventricle, and turn forward around the resti- form bodies, from which they also receive a few fibres. Each nerve is then directed outwardly, in company with the facial nerve, and passes into the internal auditory meatus, from whence it is distributed to the labyrinth. The auditory nerve is the special one of hearing, and is more particu- larly described in the account of the ear. THE GLOSSO-PHARYNGEAL, OR NINTH PAIR OF NERVES. The Glosso-pharynge'al nerves 2 arise by about a half dozen cords from the restiform body, just behind the olivary body. They issue from the cavity of the cranium, in company with the pneumogastric and accessory nerves, through the jugular foramen. Within the latter foramen, some of the fibres of the glosso-pharyngeal nerve become mingled with nerve cells, forming a small ganglion, 3 but its presence is inconstant. As it emerges from the jugular foramen, the glosso-pharyngeal nerve 1 Nervi auditor!!. Sing.: n. audito- tatorius linguae; n. lingualis paris oc- rius ; n. acusticus; portio mollis paris tari; n. lingualis paris noni; n. lingua- septirni, or nervi auditorii; portio mollis lis pneumogastrici ; first branch of the nerve : portio mollis of the seventh pair eighth pair of nerves. of nerves ; acoustic nerve. 3 Ganglion superius nervi glosso-pha- 2 N. glosso-pharyngei ; par nonum. ryngei; g. jugulare superius ; g. Ehren- Sing.: n. pharyngo-glossus; n. lingualis ritteri; g. Miilleri; ganglion of Ehren- lateralis; n. sensualis linguae; n. gus- ritter. enlarges into the SYSTEM. )trous ganglion, 1 which is connected by fine filaments with the pneumogastric sympathetic nerves, an import- tympanic nerve? ascends through a fine^ canal of the petrous por- tion of the temporal bone to the tympanum, and ex- pands upon the promon- tory into a number of branches, which supply the lining membrane of the tympanum, the round and o'val windows, and the Eustachian tube. It is. also connected with the sympathetic plexus of the internal carotid artery, witfi the smaller pe- il nerve. Frtfrn the petrous gan- glion, the glosso-pharyn- THE LAST FOUR CEREBRAL NERVES, THE FACIAL NERVE, THE SYMPA- gCal UCrVC paSSCS bC- THETIC, AND THE VPPER TWO CERVICAL NERVES. 1, facial nerve ; 2', tween the jugular Vein anastomosis between branches of the facial and glosso-pharyngeal nerve; 2, glosso-pharyngeal; 3, pneumogastric ; ^4 accessory, 5, ^nd the internal CarOti(^ hypoglossal; 6, first cervical ganglion of the sympathetic; 7, first^ arterV and descends in a and second cervical nerves; 8, carotid plexus of the sympathetic ,, , on the internal carotid artery; 9, tympanic nerve from the ptrous CUrVC TO the TOOt 01 the ganglion of the glosso-oharyngeal ; 10, its connection with the tongUC, On the inner carotid plexus; 11. Ip-anch to the Eustachian tube; 12,13, branches .-, . '\i * i i .to the round and^oval windows-of the ear; 14, 15, branches join- S1Cl ' pliaryn- ing the small and greater petrosal nerves; 16, otic ganglion ; 17, geal niUSCle, and beneath auricular branch from the jugular ganglion, connected by fila- 1-1 . -i j , ments with the petrous ganglion and tfie facial nerve; 18, anas- ] tomosis of the accessory with the pneumogastric; 19, anastomosis * it is Connected by of the first cervical nerve with , the pulley through which the tendon of inser- tion plays ; 4. superior straight muscle ; 5, inferior straight muscle ; 6, external straight muscle ; 7, 8, its two points of origin ; 9, in- terval through which pass the oculo-motor and abducent nerves ; 1 Musculi recti oculi. 2 Musculus rectus superior ; m. attol- lens oculi ; m. levator oculi ; m. super- bus; m. oculum movens tertius ; elevator muscle of the eyeball. 3 M. rectus inferior ; m depressor ocu- li ; m. deprimens ; m. humilis ; m. timi- dus ; m. oculum movens quartus ; de- pressor muscle of the eyeball. 4 M. rectus externus ; m. abductor oculi; m. indignabundus ; m. indignato- rius ; m. iracundus ; m. oculum movens secundus ; abductor muscle of the eye- ball. 5 M. rectus internus; m. adductor ocu- li ; m. adducens oculi ; m. bibitorius ; m. oculum movens primus ; adductor muscle of the eyeball. 6 M. obliquus superior oculi ; m. o. major oculi; m. trochlearis; m. trochlea- tor; m. amatorius; m. circumductionis opifex ; m. longissimus oculi. 602 THE ORGANS OF SPECIAL SENSE. men, and advances along the upper and inner part of the orbit. Term- inating in a round tendon, this passes through a fibre-cartilaginous ring or pulley, 1 situated in a depression just within the inner extremity of the supra-orbital margin. The tendon then turns backward and out- ward beneath the superior straight muscle, and is inserted into the eye- ball, midway between the latter and the external straight muscle, the cor- nea and the optic nerve. To facilitate movement, the tendon as it passes through the pulley is invested with a synovial bursa. The Inferior Oblique muscle 2 arises from the superior maxillary bone within the lower margin of the orbit and just external to the lachrymal fossa. Proceeding outward and backward below the inferior straight muscle, it is inserted into the outer part of the eyeball a little back of its middle. The oblique muscles antagonize the straight muscles by protruding the eyeball, and they also rotate it on its axis in opposite directions. THE SCLEROTICA. The Sclerot'ica, or sclerot'ic coat, 8 forms the posterior four-fifths of the exterior wall of the eyeball It is a strong, white, opaque, inextensible membrane, composed of interlacing bundles of fibrous tissue, and is adapted to give form and solidity to the eyeball. Its front part, seen through the conjunctiva, is commonly called the white of the eye. 4 It is thickest posteriorly, and gradually becomes thin- ner anteriorly, in which position the tendons of the straight and ob- lique muscles are inserted. Its back part admits the optic nerve through a funnel-shaped opening ; and the sheath of the nerve becomes continuous with the sclerotica. Into a circular aperture at its fore part the cornea is inserted, in the manner of a watch-crystal in its frame. The margin of the aperture is beveled inwardly, so as to inclose the cor- responding margin of the cornea. In the vicinity of the optic nerve and near the cornea, the sclerotica is pierced by the ciliary blood-vessels and nerves. Its inner surface is brownish, and is attached to the choroid tunic by a small quantity of delicate connective tissue. 5 The sclerotica is supplied with blood from branches of the ciliary arteries ; and its veins join the choroid and ciliary veins. 1 Trochlea. Candida, or innominata oculi; cornea 2 M. obliquus inferior oculi ; m o. mi- opaca. nor oculi. 4 Album, or albumen oculi ; lonchades. 3 Tunica sclerotica; t. albuginea; t. 5 Lamina, or membrana fusca. dura, durior, crassior, alba, extima, THE ORGANS OF SPECIAL SENSE. FIG. 357. 603 VERTICAL SECTION ANTERO-POSTERIORLY OF THE EYEBALL. 1, optic nerve; 2, sclerotica; 3, its posterior thicker portion; 4, sheath of the optic nerve continuous with the sclerotica; 5, the nerve within the sheath; 6, insertion of the straight muscles into the sclerotica; 7,8, superior and inferior straight muscles ; 9, cornea; 10, its conjunctival surface; 11, membrane of the aqueous humor; 12, 13, beveled edge of the cornea fitting into the sclerotica; 14, circular sinus of the iris; 15, choroidea; 16, the anterior portion of the same, constituting the ciliary body ; 17, the ciliary muscle ; 18, the ciliary processes ; 19, retina; 20, its origin; 21, its anterior border; 22, central retinal artery; 23, vitreous humor; 24, 25, hya- loid tunic; 26, 27, its separation into two lamina?, which inclose the crystalline lens, 28; 29, iris; 30, pupil ; 31, posterior chamber, and 32, anterior chamber occupied by the aqueous humor. THE CORNEA. The Cor'nea 1 is the transparent membrane at the front of the eyeball, the exterior wall of which it constitutes the most prominent fifth part. By a beveled margin it fits into the circular aperture adapted to it in the sclerotica. Externally the conjunctiva 2 is reflected over it ; and inter- nally it is lined by an equally transparent layer named the membrane of the aqueous humor. 3 Independently of the two layers just mentioned, the cornea 4 is composed of a fibrous tissue much resembling in appear- ance and chemical constitution that not unfrequently observed in the matrix of cartilages. The fibrous tissue has a lamellar arrangement, so that the cornea may be dissected into a number of layers, varying with the delicacy of manipulation. At the conjunction of the cornea and sclerotica the two become intimately associated, and in this position inclose a venous channel, called the circular sinus of the iris. 5 1 C. pellucida, lucida, or transparens ; membrana cornea; sclerotica ceratoides; ceratoides ; membrana ceratoides ; cera- tomeninx; the sight. 2 Conjunctival portion of the cornea. 3 Membrana, tunica propria, vagina, or capsula humoris aquei ; m. Descemeti ; m. Demoursii; m. Duddeliana; m Demu- riana ; proper membrane of Descemet ; posterior elastic lamina of the cornea ; capsula aquea cartilaginosa ; c. prsea- quosa. 4 Cornea propria. 5 Canalis Schlemmii ; c. Fontanae ; si- nus venosus Hovii ; circulus venosus orbiculi iridis, or ciliaris. 604 THE ORGANS OF SPECIAL SENSE. The cornea in a healthy condition is non-vascular, but is pervaded with a system of branching lacunae which resemble those of the bones, and serve to convey colorless nutritive liquid throughout the membrane It is supplied with delicate filaments from the ciliary nerves. On the approach of old age the circumference of the cornea usually becomes more or less dull or opaque by the deposit of fatty matter in its tissue, constituting the so-called arcus senilis. 1 FIG. 358. Fig.SbS. THE CHOROIDEA AND IRIS. 1, ciliary arteries situated at the sides of the optic nerve; 2, the long ciliary arteries ; 3, the same after having pierced the sclerotica ; 4, 5, the main divisions of the same vessels ; 6, the ciliary muscle ; 7, the anterior ciliary arteries ; 8, the short ciliary arteries to the choroidea; 9, the iris supplied by the long and anterior ciliary arteries; 10, the pupil. Fig. 359. VEINS OP THE CHOROIDEA AND IRIS. 1, sclerotica; 2, choroidea; 3, ciliary muscle, of which a portion has been removed to exhibit the ciliary processes, 4; 5. the iris; 6, pupil; 7, 8, trunks of the cho- roid veins; 9. 10, vorticose vessels ; 11, their conjunction with the veins of the ciliary processes; 12, anas- tomosis between the groups of vorticose vessels. THE CHOROIDEA. The Choroi'dea, or choroid coat, 2 is a thin, black, and highly vascular membrane succeeding the sclerotica and separating it from the retina. It is perforated behind for the passage of the optic nerve, and terminates 1 Gerontoxon ; macula cornese arcuata ; leucoma gerontotoxon. 2 The choroid; tunica or membrana choroidea; t. vasculosa; t. aciniformis; t. rhagoides; uvea. THE ORGANS OF SPECIAL SENSE. 605 in front in the ciliary muscle and body. Its outer surface, 1 of a brownish- black hue, is attached to the sclerotica, loosely at the fore part, more intimately behind, by delicate connective tissue and blood-vessels. The inner surface is smooth, shining, intensely black, and is simply applied to the contiguous surface of the retina. FIG. 360. FJG. 361. VIEW FROM BEHIND OF THE ANTERIOR PART OF THE EYEBALL. 1, sclerotica; 2, clioroidea ; 3, retina; 4, its anterior border; 5, ciliary processes; 6, the crystalline lens placed back of the iris and pupil. THE SAME VIEW, WITH THE CRYSTALLINE LENS AND RETINA REMOVED. 1, sclerotica ; 2, choroidea; 3, ciliary body ; 4, line at which the retina ceases; 5, ciliary processes; 6, iris; 7, cornea seen through the pupil. The cil'iary muscle 2 is a whitish zone connecting the anterior part of the choroidea with the circumference of the iris and the conjuction of the sclerotica and cornea. It is composed of pale, unstriated muscular fibres, and is abundantly supplied with nerves and blood-vessels. Within the position of the ciliary muscle the choroidea constitutes the so-called ciliary body, 3 of which the fore part 4 is thrown into about sixty convergent folds, 5 named ciliary processes. 6 These are received into corresponding grooves of the vitreous humor in advance of the retina, and serve to retain it in position. Their anterior extremities 7 are free, suspended behind the iris, and are bathed in the aqueous humor of the posterior chamber of the eye. In structure the choroidea consists of a vascular lamina lined on the interior with a pigmentary layer. ^ l Lamina fusca : 1. supra-choroidea ; 1. cellulosa ; 1. arachnoidea chorioideae ; 1. villoso-glandulosa. 2 Musculus ciliaris; ciliary ligament; ligamentumciliare; 1. sclerotico-chorioi- dale ; 1. iridis ; annulus, circulus, orbi- culus, or plexus ciliaris ; interstitium ciliare, or iridis ; tensori chorioideae ; circulus chorioideae ; annulus cellulosus; commissure of the uvea ; ciliary circle, or ring. V*A ^V: ' ' ' & 3 Corpus ciliare ; corona ciliaris ; orbi- culus ciliaris ; tunica ciliaris ; ciliary disk. * Pars plicata corporis ciliaris. 5 Plicae ciliares ; ciliary folds. 6 Processus ciliares ; plicse ciliares ; p. corporis ciliaris; radii ciliares; striae ciliares, ligamenta ciliaria ; nbrae palli- dse. 7 Processus ciliares. 606 THE ORGANS OF SPECIAL SENSE. FIG. 362. 13 The vascular lamina 1 is composed of blood-vessels mingled with a stroma of fusiform and stellate cells, apparently an incipient form of connective tissue. The arterial branches of the vascular lamina are derived from the short ciliary arteries, which pierce the sclerotica in the vicinity of the optic nerve, and, after repeated branching, end in a fine capillary net- work. 2 The veins derived from the latter form an intricate and remarkable plexus exterior to it, and are named, from their peculiar whorled arrange- ment, the vorticose vessels. 3 These form four groups, 4 and converge in curving lines to four equidistant trunks, which perforate the scle- rotica midway between the cornea and optic nerve, and end in the ophthalmic vein. The ciliary processes are equally vascular with other portions of the choroidea. The arteries proceed- ing from the latter into the pro- cesses become convoluted, inoscu- late, and finally terminate in veins which pursue a reverse course to join the vorticose vessels. The ciliary muscle is supplied by terminal branches of the short ciliary and the anterior ciliary arteries. The pigmen'tary layer 5 of the inner surface of the choroidea also en- velops the ciliary processes. It consists of flattened, regularly hexahe- dral nucleated cells, filled with brownish-black granular contents, which give to the choroidea its intensely black color. In albinoes the pig- mentary granular matter is absent, and the choroidea presents a red color, due to its vascularity. In many of the lower animals the inner surface of the choroidea at its back part exhibits a patch of metallic color and brilliancy, named the SEGMENT OF THE CHOROIDEA AND IRIS, SEEN ON ITS INNER SURFACE, magnified four diameters. 1, ciliary processes; 2, their free extremities behind the iris ; 3, 4, commencement of the processes ; 5, interven- ing reticular folds ; 6, veins of the ciliary processes ; 7, posterior margin of the ciliary body ; 8, choroi- dea with its veins; 9, iris; 10, its outer border; 11, the pupillary border ; 12, radiating fibres of the iris; 13, circular fibres. 1 Tunica vasculosa Halleri; t. chorioi- dea propria; external layer; proper vascular layer. 2 Membrana chorio-capillaris ; m. Ho- vii ; m. Ruyschii ; tunica Ruyschiana. 3 Vasa vorticosa ; venae vorticosee ; v. tortuossB. * Stellulae vasculosse Winslowii. 5 Stratum pigment! ; pigmentum ni- grum ; membrana Doellingeriana. ' THE ORGANS OF SPECIAL SENSE. 607 tape'tum. 1 In this the black pigmentary matter is replaced by colorless granules, which reflect the rays of light falling upon them, and thus give rise to that shining of the eyes of animals in the dark, which has proved to be so fertile a source of terror to the superstitious. THE IRIS. The Iris 2 is a flat disk with a central aperture, and regulates the amount of light received by the retina from its being endowed with the power of contracting or dilating. It is inserted into the anterior border of the ciliary muscle, is vertical in position, and is bathed in the aqueous humor. The anterior surface is divided into two zones, 3 of which the outer one is the broader. It also appears striated from the circumference ARTERIES OF THE IRIS. l,long ciliary arteries ; 2, 3, their principal divisions; 4, small branches to the ciliary muscle ; 5, 6, anterior ciliary arteries ; 7, the pupil. toward the pupil, and in different individuals presents various shades of gray, blue, or brown passing into black. The posterior surface is intensely black, arising from the presence of a layer of pigment cells like those of the choroidea. The central aperture of the iris, named the pupil, 4 is circular, and in 1 Membrana versicolor. 2 Tunica coerulea ; uvea. 3 Annul! irridis ; annulus major et mi- nor iridis ; a. externus et interims ; a. ciliaris et pupillaris. 4 Pupila ; pupula ; fenestra nigrum ; foramen oculi ; prunella ; sight of the eye. 608 THE ORGANS OF SPECIAL SENSE. the living eye appears as a black spot. ' Under the influence of light it decreases, and with the diminution of that agency it enlarges. The iris is a highly vascular fibro-muscular structure, with its surfaces covered by an epithelium. The posterior layer 1 of the latter consists of black pigment cells; the anterior layer is composed of colorless pave- ment cells. The muscular fibres of the iris are unstriated ; form a circu- lar layer 2 around the pupil, and radiate 3 toward the circumference of the iris. The blood of the iris is derived from the long and anterior ciliary arteries. The former pierce the back of the sclerotica, one on each side, and advance on the outer surface of the choroidea to the ciliary muscle, when they bifurcate and form together an arterial circle, from which nu- merous branches proceed to the iris. The anterior ciliary arteries, about half a dozen in number, pierce the sclerotica in the vicinity of the cor- nea, and, after anastomosing with the branches of the long ciliary arteries, end in the capillary vessels of the iris. The veins of the latter join the circular sinus, 4 situated at the conjunction of the cornea, sclerotica, and ciliary muscle ; and the veins from the sinus pursue the same course as the anterior ciliary arteries to terminate in the ophthalmic vein. The nerves of the iris are numerous, and are derived from the ciliary nerves which enter the eyeball by piercing the back part of the sclerotica. Advancing on the exterior of the choroidea, they reach the ciliary muscle and there form a plexus from which the iris is supplied. Prior to the eighth month of foatal life the pupil is closed by a delicate pu'pillary membrane, 5 which appears to be a continuous vascular struc- ture with the iris. At birth it is completely obliterated. THE RETINA. The Ret'ina 6 is a soft, delicate, nearly transparent and colorless mem- brane, which extends from the optic nerve on the inner surface of the choroidea to the ciliary body, where it terminates in a waving margin. 7 After death it loses much of its transparency, and assumes the appear- ance of ground glass. v 1 Uvea ; pigmentum nigrum ; membra- 5 Membrana pupillavis ; in. Wachen- na pigmenti. dorfiana ; pupillse velum. 2 Sphincter pupillae ; occlusor muscle 6 Tunica retina ; t. reticularis or reti- of the pupil ; fibrae circulares. formis ; t. nervea ; t. arachnoidea ; t. in- 3 Dilator pupillee ; fibrse radiatoe ; f. tima oculi. longitudinales iridis. 7 Ora serrata ; margo dentatus ; m. * Canal of Fontana, or of Schlemm ; undulato-dentatus. canalis Fontanse ; c. Schlemmii. THE ORGANS OF SPECIAL SENSE. 609 The surfaces of the retina are simply in contact with the contiguous structures, and in the living or perfectly fresh state are smooth. Shortly after death a small fold 1 appears on the inner surface, extending a little distance outwardly from the entrance of the optic nerve. Upon the summit of this fold, in the axis of the eyeball, there is a yellow spot, 2 FIG. 364. FIG. 365. THE EYEBALL, WITH THE SCLEROTICA, CORNEA, CHO- ROIDEA, AND IRIS REMOVED. 1, optic nerve; 2,3, retina; 4, central retinal artery entering the eye- ball through the optic nerve and distributed to the retina ; 5, 6, ciliary zone, at which the ciliary folds of the choroidea impress the vitreous humor; 7, space of the hyaloid tunic at the circumference of the crystalline lens, 8, artificially inflated, and as- suming the form of a beaded canal. RETINA, SEEN ON ITS POSTERIOR INNER SURFACE. 1, sclerotica; 2, choroidea; 3, retina; 4, white spot indicating the entrance of the optic nerve ; 5, cen- tral retinal artery ; 6, a slight fold of the retina, upon which is situated, in the axis of the eye, the yellow spot, 7 ; 8, its minute ce atral aperture. with an apparent central aperture 3 depending on a thinning of the retina. The entrance of the optic nerve is seen as an opaque, white spot, 4 from the centre of which diverge the branches of the central retinal artery. * The structure of the retina is exceedingly complex, and consists of a series of elements, enumerated from without inwardly, as follows : 1, a layer composed of narrow, vertical, columnar cells; 5 2, a granular layer; 6 3, a layer of nerve cells with caudate appendages; 7 4, nerve fibres derived from the expansion of the optic nerve ; 8 5, a structureless, limit- ary membrane. 9 The blood-vessels derived from the central retinal artery form a cap- 1 Plica centralis retinae ; p. transversa retinas. 2 Macula lutea ; m. flava centralis re- tinas ; limbus luteus foraminis centralis. 3 Foramen centrale Scemmerringii ; fo- vea centralis retinae. 4 Papilla, or colliculus nervi optici. 5 Tunica Jacobi ; Jacob's membrane; basillar layer ; stratum bassillorum ; basilli et coni ; rods and cones ; prisma- ta praeacuta et coni gemini; layer of rods and cones. 6 Stratum granulosum. 7 The layer of cineritious cerebral substance of Kolliker; layer of gray nerve substance ; stratum globulosum. 8 Expansion of the optic nerve; stra- tum fibrillosum; s. vasculoso-nerveum ; stratum medullare. 9 Membrana limitans. 39 610 THE ORGANS OF SPECIAL SENSE illary net-work in the nervous layers of the retina j 1 and the veins return in the course of the corresponding arteries. The retina is the sensitive membrane of the eyeball that which re- ceives the impression of light, the form and color of exterior objects. THE AQUEOUS HUMOR. The A'queous humor 2 is a transparent, colorless, albuminoid liquid, which fills the space between the cornea and crystalline lens. The space it occupies is divided by the iris into two parts, named the anterior and posterior chambers of the eye, 3 of which the former is the larger. The iris is freely suspended in the aqueous humor, both of its surfaces being bathed in it, which is likewise the case with the ciliary processes. Lining the interior of the cornea, and continuous with the anterior layer of the iris, is the so-called membrane of the aqueous humor. 4 It is an elastic membrane, consisting of a structureless basement layer and a pavement epithelium. Its border is resolved into a fine net-work of fibres, 5 which are reflected upon, and become continuous with, the ante- rior surface of the iris. THE CRYSTALLINE LENS. The Crystalline lens 6 succeeds the aqueous humor from behind, and is the most consistent of the humors of the eye. It is a double convex lens, of which the poste- FIG. 366. r i or surface is the more 1234 5 convex, and is received into a depression 7 of the vitreous humor : while its anterior surface is bathed by the aqueOUS humor. It IS retained in position ^ fa ^ ^^ Qf the vitreous humor, which is reflected from its border to its anterior and posterior surfaces. THE CRYSTALLINE LENS. 1, lens of a foetus of seven months ; 2, lens of a foetus of nine months; 3, lens of a child of ten years of age^^ensofanadultviewedinprofilej^thesameseenonits anterior surface. 1 Lamina vasculosa retinae. 2 Humor aquosus ; h. oviformis ; h. ovatus ; h. oodes ; h. hydatodes ; albu- gineous humor. 3 Camerse oculi. 4 Membrane of Descemet. See page 5 Ligamentum pectinatum iridis ; pro- cessus peripherici ; pillars of the iris. 6 Lens crystallina ; corpus crystalli- num ; crystalline humor or body ; the crystallinus ; corpus discoides or pha- coides ; phacus ; gemma oculi. 7 Fossa lenticularis ; f. patellaris. \ 4/ THE ORGANS OF SPECIAL SENSE. 611 From foetal life to the adult period the lens gradually diminishes in its degree of convexity, and increases in breadth ; and in the advance of life it continues to decline in convexity. It is perfectly transparent and colorless, though in old age it is apt to assume a yellowish hue. Boil- ing water or alcohol coagulate it and render it hard and opaque white. The lens is provided with a transparent membranous capsule, 1 which is structureless, and is thickest anteriorly. The substance 2 of the lens is composed of concentric lamina, which increase in density toward the centre. The laminag are composed of hexahedral fibres, with corrugated sides closely adapted to one another. In fishes this corrugated character is much exaggerated, and the fibres indigitate by serrated processes. FIG. 367. FIG. 368. CRYSTALLINE LENS, BREAKING UP INTO SEGMENTS. SEGMENT OF THE CRYSTALLINE LENS, exhibiting the concentric arrangement of the laminae. Not unfrequently, in dissections, the lens is observed with a disposi-. tion to separate into segments from its axis, and this appears to indicate the arrangement of structure. The segments are composed of the con-- centric laminae above described, and these consist of the hexahedral fibres, which pursue a direction from the bases of the segments to their summits and lateral edges. The intervals of the segments are oqcupied, with a mingled amorphous and finely granular matter. Between the front of the lens and its capsule there exists a lawyer Qf" delicate epithelial cells, 3 which, after death, become detached and mingled with some liquid 4 exuding from the contiguous structures. In foetal life, a vessel from the central retinal artery traverses the axis of the vitreous humor, and is distributed to the capsule of the lens; but it is obliterated before birth. THE YITEEOUS HUMOE. The Vit'reous humor, 5 less consistent than the crystalline lens, but more so than the aqueous humor, is equally transparent and colorless. 1 Capsula lentis ; tunica crystalioidea; * Liquor or aqua Morgagni. t. arachnoidea. 5 Corpus vitreum ; c. hyaloideum ; hu- 2 Humor crystallinus ; h. glacialis. mor vitreus ; h. hyalinus ; h. glacialis. 3 Globuli lentis. 612 THE ORGANS OF SPECIAL SENSE. It occupies all the space included within the expanse of the retina and the ciliary body, and consists of a viscid albuminoid liquid 1 contained in the meshes of a delicate membranous structure, named the hy'aloid tunic. 2 This is homogeneous, and, besides forming partitions 3 through the mass of the vitreous humor, affords it an exterior investment. In advance of the retina the hyaloid tunic is thicker than elsewhere, and forms the ciliary zone.* This is in contact externally with the ciliary body, and is impressed by its processes, which, being received into corresponding grooves of the zone, contribute to maintain the position of the vitreous humor. In front, the tunic separates into two laminee, which diverge upon the border of the crystalline lens, and become confluent with the anterior and pos- terior surfaces of its capsule. The angle of separation 5 of the two laminae is partially interrupted at short distances, so that when inflated it assumes the appearance of a beaded canal 8 at the circumference of the lens. THE EAR. The Ear or organ of hearing is exceedingly complicated in its struc- ture, and is for the most part concealed from view within the petrous portion of the temporal bone. It is divisible into the external, middle, and internal ear. THE EXTERNAL EAR. The External ear consists of the auricle and the external auditory meatus. The Auricle, 7 or ear of common language, joins the external auditory meatus between the articulation of the lower jaw and the mastoid proc- ess. It resembles the expanded mouth of a trumpet crushed inwardly, and mainly derives its peculiar form from a fibre-cartilage. The wind- ing ridges and hollows of its outer surface correspond with reverse char- acters on the inner surface or back of the ear. Its lower pendant portion, named the lobe, 8 is a pouch of skin filled with connective tissue and fat. 1 Vitrina ocularis. ciliaris ; membranula coronas ciliaris ; 2 Tunica hyaloidea; t. vitrea; mem- corona ciliaris; orbiculus capsulo-cilia- brana arachnoidea. ris ; ligamentum suspensorium lentis. 8 Hyaloidea interna ; pars cellularis 5 Canal of Petit ; canalis Petitianus ; hyaloideae ; cellularis corporis vitrei ; circulus Petit! ; camera tertia aquosa. tunica arachnoidea. 6 Bullular canal of Petit. 4 Zona ciliaris; pars ciliaris hyaloi- 7 Auricula; pavilion; pinna; ala; deae ; corpus ciliare hyaloideae ; zonula otium. Zinni ; zonula, or zone of Zinn ; lamina 8 Lobulus auriculas. THE ORGANS OF SPECIAL SENSE. 613 FIG. 369. The inflected border of the auricle, curving from above the audit- ory meatus upward, backward, and downward, is the helix. 1 Separated from this by a groove 2 is the ridge named the antihelix, which bifur- cates above, 3 and includes a trian- gular fossa. 4 In front of the audit- ory meatus is a conical eminence, the tragus ; 5 and separated from this by a rounded notch, and situ- ated below the antihelix, is an- other eminence, the antitragus, The deep concavity within the po- sition of the antihelix, and present- ing a semispiral course toward the entrance of the auditory meatus, is the concha. The auricle, excepting its lobe, consists of a plate of fibro-cartilage, invested with a perichondrium, to which the skin tightly adheres. Several fissures or intervals exist in the fibro-cartilage, occupied by con- nective tissue. Thus the fibro-car- tilage is deficient between the tragus and the commencement of the he- lix, and between the lower end of the latter and the antitragus. Short fissures also exist on the tragus and the fore part of the helix. In the last-mentioned position there is a small conical eminence, named the process of the helix. The fibro-cartilage of the auricle is thin, and rather brittle, but is ren- dered more tenacious by its perichondrium. The skin is thin, and, as elsewhere generally, is furnished with minute hairs and sebaceous glands. The latter are well developed in the fossaB of the auricle, more especially in the concha. Besides the connection of the skin, the auricle is attached to the side of the head by ligamentous bands. The anterior ligament, broad and strong, extends from the process of the helix to the root of the zygo- THE AURICLE. 1, helix; 2, fossa of the helix; 3, antihelix; 4, fossa of the antihelix; 5, concha sub- divided by the commencement of the helix ; 6, tra- gus; 7, antitragus; 8, entrance of the external auditory meatus ; 9, the lobe. The large dots in the concha and fossa of the autihelix are the ori- fices of sebaceous glands. 1 Capreolus. 2 Fossa navicularis, scaphoides, or in- nominata; fossa of the helix. 3 Crura furcata. * Fossa of the antihelix; fossa trian- gularis, or ovalis. 6 Hircus. 614 THE ORGANS OF SPECIAL SENSE. matic process. The posterior ligament attaches the convexity of the concha to the root of the mastoid process. The auricle possesses five small muscles situated between the fibro- cartilage and the skin, and three larger ones which connect it with the side of the head. They are all composed of striated fibres, and while the function of the former is very obscure, the latter are generally quite inactive. The smaller muscle of the helix 1 is a short fasciculus situated on the commencement of the latter. The greater muscle of the helix 2 is a narrow band situated on the fore part of the auricle, above the process of the helix. The muscle of the tragus 3 is a short plane of fibres situated on the outer surface of the tragus. The muscle of the antitragus 4 is a band extended from the antitragus to the lower extremity of the helix. The transverse muscle, 5 larger than the preceding, is situated on the back of the auricle, and consists of a plane of fibres extending from the concha to the ridge bounding the groove of the antihelix. The superior auric'ular muscle 6 is a broad, thin, and pale fan-like plane of fibres, arising from the border of the occipito-frontal aponeu- rosis, and descending to be inserted back of the fossa of the antihelix. In action, it will draw the auricle upward. The anterior auric'ular muscle, 7 generally less distinct than the pre- ceding, is a thin, transverse fasciculus arising from the temporal fascia, and inserted into the helix and concha. In action it would draw the auricle forward. The posterior auric'ular muscle, 8 stronger and less pale than the others, consists of two or three fasciculi arising from the mastoid proc- ess, and inserted into the back of the concha. In action it draws the auricle backward. The auricle is abundantly supplied with blood-vessels and nerves. Its 1 M. helicis minor. 7 M. auricularis anterior; m. attra- 2 M. helicis major. hens auriculae; m. anterior aims ; m. 3 M. tragicus. zygomato-auricularis. 4 M. antitragicus. 8 M. auricularis posterior; m. retra- 5 M. transversus auriculae ; m. t. and hens, or retrahentes auriculae ; m. pos- obliquus auris. terior auris: m. mastoido-auricularis; 6 M. auricularis superior; m. attollens m. deprimens auriculae; m. bicaudalis, auriculae, or aurem; m. levator, or su- triceps, or tricaudalis auris; m. pro- perior auris; m. temporo-auricularis. prius auris externae; m. secundus pro- priorum auriculae. THE ORGANS OF SPECIAL SENSE! 615 arteries form a conspicuous net-work upon the fibro-cartilage, and are derived from the anterior and posterior auricular branches of the tem- poral and external carotid arteries. Its veins terminate in the temporal vein. The nerves are derived from the great auricular branch of the cervical plexus, the posterior auricular branch of the facial nerve, and the auriculo-temporal branch of the inferior maxillary nerve. The External aud'itory mea'tus 1 is a canal extending from the concha to the tympanum, and serves to conduct sounds to the latter which FIG. 370. GENERAL VIEW OF THE EAR, RIGHT SIDE, LAID OPEN FROM THE FRONT. 1, auricle; 2, concha; 3, 4, exter- nal auditory meatus; 5, ceruminous glands; 6, tympanic membrane; 7, anvil; 8, mallet; 9, its handle inserted into the tympanic membrane; 10, tensor muscle of the latter; 11, cavity of the tympanum: 12, Eustachian tube; 13, 14, 15, the three semicircular canals; 16, cochlea; 17, the internal auditory meatus: 18, facial nerve occupying a groove of the auditory nerve, 20, 21. are collected by the auricle. It is about an inch in length, is directed inward and forward, and curves in its course upward and downward. Its commencement is vertically oval, its middle is the narrowest part, and its bottom is closed by the tympanic membrane. The meatus consists of an outer shorter portion, which is a prolonga- tion of the auricle, and an inner portion composed of the osseous audit- ory meatus lined with an extension of the skin. The outer portion of the meatus, independently of the skin, is com- 1 Meatus auditorius externus; external auditory canal; auricular canal; alve- arium; scapha. 616 THE ORGANS OF SPECIAL SENSE. posed of a scroll of fibro-cartilage, open above, and continuous by a nar- row slip with that of the auricle. The interval of the scroll is occupied with fibrous membrane, thus producing a complete tube. The fissures intervening between the outer part of the latter and the concha are like- wise occupied with fibrous membrane, and its inner extremity is con- nected by an annular ligament with the orifice of the osseous rneatus. The skin of the outer portion of the auditory meatus is comparatively thick, and is furnished with numerous hairs and sebaceous glands. Its surface presents a punctated appearance, from the many orifices of the ceru/minous glands, 1 which secrete the ceru/men or ear-wax. 2 These glands are small, rounded bodies, of a brownish-yellow color, im- bedded in the subcutaneous tissue. They consist of a narrow tube con- voluted upon itself into a rounded mass, the terminal portion of the tube penetrating the skin as the duct of the gland. The inner portion of the auditory meatus corresponds with the passage of the same name in the macerated bone, and is narrower and longer than the outer portion. The skin lining it is very thin, is unprovided with hairs or glands, and becomes continuous with the structure of the tympanic membrane which closes the bottom of the meatus. The blood-vessels and nerves of the external auditory meatus have the same derivation as those of the auricle. THE MIDDLE EAE. The Middle ear consists of the tympanum, together with its inclosed bones, their ligaments and muscles, and the mastoid sinuses and Eusta- chian tube. The Tym'panum, or drum of the ear, 3 is an irregular cavity in the in- terior of the petrous portion of the temporal bone. It is about half an inch in height and breadth, and one to"* two lines from without inward. Its roof is a plate of bone separating it from the cranial cavity ; its floor is a groove between the outer and inner walls. Into its upper back part open the mastoid sinuses ; and in front it narrows into the Eusta- chian tube. The outer wall is formed by the tympanic membrane, and its inner wall bounds the labyrinth. The tym'panic membrane, or membrane of the tym'panum, 4 is a cir- 1 Glandulae, or folliculae ceruminosse. the ear; antrum, or cavitas antrosa 2 Cerea; sordes, sordiculse, or mar- auris. morata aurium; ceruminous humor; 4 Membrana tympani; membrane of cypsele, or cypselis; fugile. the drum; diaphragma, mediastinum, or 3 Cavum, or cavitas tympani; cavity tegumentum auris; myringa; myrinx. of the tympanum, or drum; barrel of THE ORGANS OF SPECIAL SENSE. cular partition separating the cavity of the tympanum from the external auditory meatus, from which it receives transmitted sounds. It is not flat, but slightly funnel shaped, and is situated obliquely, so that its outer, depressed surface 1 is directed downward and forward. The greater part of its circumference is inserted into a fine groove, which in the new- born child is included by an osseous ring, subsequently developed, by prolongation outwardly, into the osseous auditory meatus. Into its upper part, descending as far as the centre, the handle of the mallet is inserted, so that vibrations of the tympanic membrane are communicated to the latter. The tympanic membrane is thin and translucent, and is composed of a layer of fibrous tissue invested externally with a continuation of the epi- dermis of the meatus, and internally with an extension of the lining mu- cous membrane of the tympanum. Its fibrous layer consists of fibres radiating from the centre, with some concentric fibres at its circumference. FIG. 371. CAVITY OF THE TYMPANUM AND MASTOID SINUSES, right side. The auditory meatus, tympanic mem- brane, small bones, and outer wall of the mastoid sinuses removed. 1, promontory; 2, pyramid; 3, ridge within which descends the Fallopian canal; 4, round window; 5, oval window; 6, osseous portion of the Eustachian tube; 7, surface of attachment of the cartilage of the latter; 8, canal above the tube which lodges the tensor muscle of the tympanum ; 9, Fallopian canal laid open ; 10, canal occupied by the greater petrous nerve; 11, mastoid sinuses; 12, communication of the latter with the tympanum; 13, orifice through which the tympanic branch of the facial nerve enters the tympanum. The inner wall of the tympanum presents a convex eminence, the prom'ontory, 2 produced by the projection of the cochlea. Above the 1 Umbo. 2 Promontorium ; tuber, or tuberositas tympani. 618 THE ORGANS OF SPECIAL SENSE. back of the promontory is an orifice, the oval window, 1 which communi- cates with the vestibule, but is closed by the application of the base of the stirrup. Above the oval window and promontory is a ridge, pass- ing from before backward, produced by the course of the Fallopian canal, which transmits the facial nerve. Behind the lower part of the promontory is a pit, at the bottom of which is an aperture named the round window. 2 This communicates with the cochlea, but is closed by the secondary tym/panic membrane, 3 which consists of a fibrous layer, invested externally with the lining membrane of the tympanum, inter- nally with that of the cochlea. At the back part of the tympanum a descending ridge indicates the continuation of the Fallopian canal to the stylo-mastoid foramen. From the ridge there projects forward a hollow, conical eminence, named the pyramid, 4 The small bones 5 occupy the upper part FIG. 372. 4 5 SMALL BONES OF THE EAR. 1. Mallet seen on its inner surface. a, head; b, articular surface for the anvil; c, handle; d, the long process. 2. Mallet seen on its outer surface, a, head ; b, articu- lar surface; c, handle; d, long process; e, short process. 3. Mal- let seen from behind, a, head and articular facet; b, short proc- ess; c, long process. 4. Anvil seen on its inner surface, a, body ; b, articular facet for the mallet ; c, short process ; d, long process; e, orbicular process. 5. Anvil seen on its outer surface. a, body ; b, articular facet ; c, d, short and long processes. 6. Or- bicular process, at birth a distinct bone. 7. Stirrup, a, head; b, c, crura; d, base. 8. Base of the stirrup, which is applied to the oval window. 9. Stirrup cut so as to exhibit the groove on the inner side of its crura a. the fibrous layer of the tympanic membrane of the tympanum, and are named, from their resem- blance, the mallet, anvil, and stirrup. Articulating movably with one an- other in the order given, the mallet is attached to the tympanic membrane, and the stirrup communi- cates with the oval win- dow, so that the vibra- tions of the former are continued through the se- ries of bones to the latter. The Mallet 6 is situated vertically, with its head lodged in the upper part of the tympanum, and its handle descending into as far as its centre. The 1 Fenestra ovalis, or vestibularis ; fora- men ovale. 2 Fenestra rotunda, triquetra, or coch- learis; foramen rotundum. 3 Membrana tympani secnndaria; m. fenestras rotundae ; tympanum minus, or secundarium. 4 Pyramis; eminent i a pyramidalis tympani. 5 Ossiculi auditus; o. auris. e Malleus, malleolus; ossiculum mal- leolo-assimilatum; the hammer. THE ORGANS OF SPECIAL SENSE. 619 head is rounded, and at its back part has an oval facet invested with cartilage, for articulation with the anvil. The handle 1 is a tapering process, slightly twisted and compressed. The neck is slightly con- stricted, and gives off two processes. The long process 2 is a slender spine projecting nearly at a right angle from the neck, and enters the glenoid fissure ; the short process 3 is a conical eminence at the root of the neck. The Anvil 4 is situated behind the mallet, near the entrance to the mas- toid sinuses. Its body is irregularly square, and at its fore part has an oval articular surface for the head of the mallet. Behind, it has a pair of diverging processes, of which the lower is the longer. The short process 3 projects backward, and is connected by a ligamentous band to the posterior part of the tympanum. The long process 6 is curved and tapering, and descends nearly parallel to the handle of the mallet. Its end internally supports an orbicular process, 7 which articulates with the head of the stirrup. At birth the latter process is a distinct bone, but it soon becomes co-ossified with the anvil. The Stirrup 8 is directed horizontally inward from the anvil to the oval window. Its head is flattened, and at the summit has a concave artic- ular facet, invested with cartilage, for the orbicular process of the anvil. From the head a pair of crura curve inwardly to join the base, which is applied to the oval window. The three bones just described have movable articulations, surrounded by a capsular ligament and lined with synovial membrane. The articu- lation between the mallet and anvil is hinge like; that between the latter bone and the stirrup is a ball-and-socket joint. The suspensory ligament 9 of the mallet is a slender band of fibres, extending from the head of the bone to the roof of the tympanum. The suspensory ligament 10 of the anvil extends from its short process to the back part of the tympanum. The annular ligament 11 of the stirrup connects the margin of the base with the border of the oval window. 1 Manubrium. 7 QS, or ossiculum orbiculare, lenticu- 2 Processus, or apophysis longus, gra- lare, squamosum, cochleare, or quartum; cilis, Folii, or Rauii. processuslenticularis; ossiculum orbicu- 3 P. brevis; p. obtusus. lare or lenticulare Sylvii; globulus sta- 4 Incus; acmon; os incude simile; os- pedis; epiphysis cruris longioris incudis. siculum incudi, or molari denti compa- 8 Stapes ; stapha ; staffa. ratum. Ligamentum superiores, or teres. 5 Ramus horizontals. 10 Posterior ligament. 6 Ramus verticalis. L. annulare, or orbiculare baseos stapedis. 620 THE ORGANS OF SPECIAL SENSE. Three minute muscles, composed of striated fibre, are connected with the bones of the ear, to regulate their movements. Others 1 have been described, but their existence is not usually acknowledged. The tensor muscle 2 arises from the end of the cartilage of the Eusta- chian tube and the contiguous surfaces of the sphenoid and temporal bone. Passing through an osseous canal of the latter, above the Eusta- chian tube, it ends in a tendon which enters the tympanum and turns outwardly to be inserted into the neck of the mallet. Its contraction increases the tensity of the tympanic membrane. The laxa'tor muscle 3 arises from the spinous process of the sphenoid bone, passes upward and outward, and enters the glenoid fissure, to be inserted into the long process of the mallet. In action it relaxes the tympanic membrane. The stape'dius muscle 4 arises within the hollow of the pyramid, and is inserted into the head of the stirrup. It regulates the pressure of the base of the latter against the oval window. The cavity of the tympanum is everywhere lined with a delicate mu- cous membrane, which likewise invests the small bones, stretching across the aperture of the stirrup, 5 and covering the muscles and ligaments. It is pink in color from its vascularity, and is provided with a pavement- like epithelium. The arteries of the tympanum, though small, are nu- merous. They are derived from the tympanic branch of the internal maxillary artery, the stylo-mastoid artery, the great meiiingeal and de- scending palatine arteries, and from the internal carotid artery as it passes through the carotid canal. The veins communicate with the great meningeal and pharyngeal veins, and through a plexus, near the glenoid articulation, with the internal jugular vein. The nerves are derived from the tympanic branch of the glosso-pharyngeal, and the carotid plexus of the sympathetic nerve. The Mastoid sinuses 6 consist of numerous irregular cavities in the interior of the mastoid portion of the temporal bone, communicating by a large orifice 7 with the upper back part of the tympanum. They are 1 Laxator tympani minor. ternus; m. Eustachii; m. spheni-salpin- 3 M. tensor tympani; m. internus go-mallei. mallei; m. tensor auris internus; m. 4 M. stapedius, or pyramo-stapedius. salpingo-mallei. 5 Membrana obturatoria, or propria 8 M. laxator tympani; m. 1. t. major; stapedis. anterior ligament of the malleus; m. 6 Mastoid cells; cellulse mastoidese; mallei externus, or anterior; m. obliquus, antrum mastoideum. or externus auris; m. laxator auris in- 7 Petro-mastoid canal. THE ORGANS OF SPECIAL SENSE. 621 lined throughout with a delicate mucous membrane, provided with a pave- ment epithelium. The Eusta'chian tube 1 is a trumpet-shaped canal, rather over an inch and a half long, extending from the fore part of the tympanum obliquely inward, forward, and downward to the pharynx. Its upper section is formed by an osseous canal in the petrous portion of the temporal bone, which communicates at its outer end with the tympanum, and narrows to its union with the other section in the angle between the squamous and petrous portions of the temporal bone. The lower and longer section of the Eustachian tube proceeds from the angle mentioned along the posterior border of the sphenoid bone to the inner side of the internal pterygoid process. Gradually expanding in its course, it terminates by an oval orifice, with a prominent border, at the side of the pharynx, on a level with the turbinated bone, just back of the posterior nasal orifice. It is composed of a triangular plate of cartilage, bent into a gutter, open at its outer part, but converted into a complete tube by fibrous membrane. The Eustachian tube is lined with mucous membrane, provided with a ciliated epithelium, and is continuous with that of the pharynx and tym- panum. THE INTERNAL EAE. The Internal ear includes the labyrinth and the internal auditory meatus. The Lab'yrinth, 2 named from its highly complex character, is the most important portion of the organ of hearing, as it contains the entire dis- tribution of the auditory nerve. It is imbedded in the petrous portion of the temporal bone, and consists of three parts, named the vestibule, the semicircular canals, and the cochlea. Though these may be des- cribed as cavities, it should be understood that the labyrinth has os- seous walls independent of the bony structure embracing it. At birth it may be readily excavated from the looser surrounding osseous sub- stance ; but at a later period this substance becomes condensed and confounded with the exterior surface of the labyrinth. The Ves'tibule 3 is an irregularly oval cavity, situated between the tympanum and the bottom of the internal auditory meatus, and joining 1 Tuba Eustachiana, or Aristotelica ; 2 Labyrinthus ; 1. auris intimae ; laby- canalis gutteralis ; meatus csecus : Her rintliic cavity ; pars intiraa organ! audi- a palato ad aurem ; ductus auris palati- tus ; antrum buccinosum. nus; syrinx; syringa. 3 Vestibulum labyrinth!. 622 THE ORGANS OF SPECIAL SENSE. FIG the semicircular canals postero-externally, the cochlea antero-internally. Through its outer wall it communicates with the tympanum by the oval window. A slight semicircular ridge or crest 1 springs from the floor of the vestibule, ascends on its inner wall to the roof, and terminates in a small pyramidal eminence. 2 The latter presents a group of minute foramina commu- THE INTERNAL EAR, CONSISTING OF nicating with the internal auditory meatus, and THE LABYRINTH AND INTERNAL AUD- name( J ^6 SUpCnOr CriVrifbrHl SpOt. 3 TllC ITORT MEATUS, LAID OPEN. The lower part of the figure exhibits the three crest separates two recesses, called, from their osseous semicircular canals con- shape, the hemispherical 4 and hemielliptical taining the membranous semicir- . cuiar canals, i, 2, two semidrcu- fossa. 5 The former is the smaller, and occu- iar canals, ending in a common pj es the antero-internal portion of the vesti- tube, 3; 4, simple extremity of one , - of the canals; 5, 6, 7, dilated ex- bule ; the latter occupies the postero-external tremeties or ampullae of the canals; portion. Just below the Centre of the hemi- S, elliptical, and 9, hemispherical -i i f / saccules contained in the vestibule. Spherical fossa IS a SCCOnd group of minute Above the latter is the cochlea; foramina communicating with the internal and to its left the internal auditory -,., -, ,-. . , , ., , meatus auditory meatus, and named the middle criV- riform spot. 6 Immediately in advance of the fossa, the orifice 7 of the vestibular scala of the cochlea communicates with the vestibule. Into the hemielliptical fossa open the orifices of the semicircular canals and the aperture 8 of a small vascular canal 9 which communicates with the posterior surface of the petrous portion of the temporal bone, and transmits the vestibular vein to the inferior petrosal sinus. The Semicircular canals, 10 three in number, are situated postero-ex- ternally to the vestibule and above the inner back part of the tympanum. From their position they are named superior, 11 posterior, 12 and infe- rior; 13 the former two being vertical, the last horizontal. They are so 1 Crista vestibuli. 2 Eminentia pyramidalis ; pyramis vestibuli. 8 Macula cribrosa superius. * Fossa, or fovea hemispherica ; re- cessus hemisphericus ; sinus rotundus. 5 Fossa, or fovea hemielliptica, semi- elliptica, or elliptica; recessus hemiel- lipticus; sinus ovatus. 6 Macula crfbrosa media. 7 Apertura scalaa vestibuli. 8 Recessus, or fovea sulciformis. 9 Aqueduct of the vestibule ; aquas- ductus vestibuli, or Cotunnii ; canal of Cotunnius. 10 Canales, or ductus semicirculares, circulares, or tubaeformes; semicircular! ossei; funes, or canaliculi semicirculares labyrinthi. 11 Also vertical, or superior vertical. 12 Also posterior vertical, or oblique. 13 Also external, or horizontal. THE ORGANS OF SPECIAL SENSE. 623 related with one another as to correspond with the inner, back, and lower faces of a cube. Each canal is rather more than half a circle, and forms at one extremity a bottle-like dilatation, named the ampulla, which communicates with the vestibule. Of the undilated extremities, two conjoin, and, with the re- maining extremity, likewise open into the vestibule ; and thus the three canals communicate with the latter by five orifices. Within the ampulla of the posterior semicircular canal there is a third group of minute foramina communicating with the internal auditory meatus, and named the inferior cribriform spot. 1 The interior of the vestibule and the semicircular canals is lined with- a delicate membrane, resembling a serous membrane. It consists of a fibrous layer adhering to the osseous surface as a periosteum, a structure- less basement layer, and a tessellated epithelium. Within this mem- brane the cavity is occupied by a serous liquid, named the perilymph, 2 from its surrounding a secondary structure, known as the membranous lab'yrinth, This consists of a pair of communicating pouches, 3 con- tained in the vestibule, and three semicircular canals, of the same form as the osseous canals which contain them. The smaller pouch occupies the hemispherical fossa, and is named the spherical saccule ; 4 while the other pouch, occupying the hemielliptical fossa, is named the elliptical saccule, 5 and is joined by three membranous semicircular canals. The membranous labyrinth consists of an outer fibrous structure, lined internally with a tessellated epithelium, and filled with a serous liquid, named the endolymph. 6 The vestibular branch of the internal auditory nerve is distributed to the membranous labyrinth, and maintains its floating position in the perilymph. This nerve divides at the bottom of the internal aud- itory meatus into three branches, of which one enters the vestibule at the superior cribriform spot, to be distributed to the elliptical sac- cule and the ampullae of the superior and inferior semicircular canals ; a second enters at the middle cribriform spot, and is distributed to the 1 Macula cribrosa inferius. utriculus, sinus, or alveus communis ; 2 Liquor, or aquula Cotunnii; aqua, utricle; sinus, or alveus utriculosus; or aquula acustica, or auditoria; aquula. median sinus. 3 Sacculus vestibuli. Endolympha; vitrina auditiva; aqu- 4 Sacculus sphaericus ; sacculus ; sac- ula vitrea auditiva ; aqua labyrinth! cule. membranacei ; humor vitreus auris; 5 Sacculus ellipticus ; s. vestibuli ; liquor of Scarpa. 624 THE ORGANS OF SPECIAL SENSE. hemispherical saccule ; and the third enters at the inferior cribriform spot, and is distributed to the ampulla of the posterior semicircular canal. FIG. 374. fig. 374. INTERNAL EAR LAID OPEN. 1, vestibular branch of the auditory nerve ; z, branch to the spherical saccule ; 3, branch to the elliptical saccule ; 4, 5, 6, branches to the ampulla} of the membranous semicircular canals; 7, cochlear branch of the auditory nerve; 8, cochlea. Fig. 375. NERVES OF THE VESTIBULE AND SEMICIRCULAR CANALS, magnified three diameters. 1, vestibular branch of the auditory nerve; 2, branch to the spherical saccule; 3, branch to the elliptical saccule; 4, 5, 6, branches to the ampullae of the semicircular canals ; 7, cochlear nerve. Adhering to the inner surface of the two saccules of the vestibule, at the point of entrance of the nervous filaments from the cribriform spots, are two white discoidal masses, consisting of minute crystalline particles, called o'tolites, 1 These cohere, and appear to be in contact with the nervous filaments distributed to the saccules. They are composed of carbonate of lime, and are an important element of structure to the organ of hearing, as they are found in the ear of most animals. The arteries of the vestibule and semicircular canals are derived from the vestibular branches of the auditory artery accompanying the branches of the vestibular nerve. The veins partly terminate in the venous sinus of the cochlea, and partly in the vestibular vein, which communicates with the inferior petrosal sinus. The Coch/lea 2 is the inner portion of the labyrinth, and is named from its resemblance to a snail-shell. Its base is applied to the bottom of the internal auditory meatus, and its apex is directed forward and slightly outward. It consists of an osseous tube, about an inch and a half long, wound nearly three times around a central axis, with each turn suc- cessively rising. The commencement of the tube is connected with the fore part of the vestibule, and produces the promontory of the 1 0tolithi; otoliths; otoconia; otoconites. 2 Concha auris interna; c. labyrinth!; cavitas cochleata, or buccinata; trochlea labyrinth! ; antrum buccinosum. THE ORGANS OF SPECIAL SENSE. 625 tympanum. Turning from right to left in the right ear, and the reverse direction in the left ear, it ends in a closed extremity, named the cupola, which nearly reaches the front surface of the petrous portion of the tem- poral bone above the ascending part of the carotid canal. FIG. 376. FIG. 377. THE COCHLEA, LAID OPEN, ITS SUMMIT TURNED UP- WARD, magnified three diameters. 1, 2, 3, the tym- panic scala ; 4, 5, 6, the vestibular scala ; 7, 8, os- seous spiral lamina; 9, membranous spiral lamina; 10, orifice of communication of the two scalar at the summit of the cochlea; 11, 12, termination of the osseous and membranous spiral laminae. * 1 6 4 2 S35 71 THE COCHLEA, LAID OPEN, AND VIEWED FROM IT 8 SUMMIT TOWARD THE BASE. 1, Cut edges of the Of~ seous wall of the cochlea ; 2, osseous spiral lamina, seen within the vestibular scala; 3, end of the lamina; 4, 5, its outer border; 6, membranous spiral lamina; 7, its end; 8, foramen of communi- cation with the tympanic scala. The axis of the coch/lea 1 is conical, its base forming the spiral tract at the bottom of the internal auditory meatus, and its summit becoming continuous with the inner wall of the last turn of the canal of the cochlea. 2 It is traversed by numerous fine canals, continuous with the foramina of the spiral tract and transmitting the filaments of the coch- lear nerve, together with the cochlear branches of the auditory artery. A central canal, 3 larger than the others, extends the entire length of the axis, and transmits a branch of the latter vessel. An osseous spiral lamina 4 commences just below the hemispherical fossa of the vestibule, winds around the axis of the cochlea, extending about half way across its canal, and terminates in a pointed process 5 at the summit of the latter. The lamina is traversed by a multitude of fine anastomosing canals, which are continuous with those of the axis of the cochlea, and open into a groove at the free margin of the lamina. 1 Column of the cochlea ; axis, colu- mella, or pyramis cochleae ; modiolus. 2 The last turn of the inner wall of the cochlea upon its axis forms the infun- dibulum, or scyphus Vieussenii, or au- ditorius. 3 Canalis centralis modioli. * Lamina spiralis ossea; septum scalae, or cochlae auditorine ; zona ossea. 5 Hamulus. 40 626 THE ORGANS OF SPECIAL SENSE. The interior of the cochlea is lined by a delicate membrane continu- ous with, and like that of the vestibule. After investing the two sur- faces of the osseous spiral lamina, it is extended in a double layer from the free border of the latter across the canal of the cochlea to the outer wall, where it is firmly attached. This extension of the membrane, which is named the membranous spiral lamina, 1 together with the osseous spiral lamina, divides the canal of the cochlea into two distinct pas- sages, which communicate with each other only at the summit of the cochlea. 2 At the lower extremity of the latter, one of the passages terminates at the round window of the tympanum, and is thence named the tym/panic sca'la, 3 while the other opens into the vestibule, and is called the vestib'ular sca'la, 4 Both scalae 5 of the cochlea are filled with a limpid serous liquid, which communicates with the perilymph of the vestibule, but is prevented from escaping at the round window by the secondary tympanic membrane. The axis of the cochlea within the tympanic scala is pierced with a series of foramina, transmitting veins from the lining membrane of the cochlea to a spiral sinus 6 within the axis. At the lower extremity of the same scala is the orifice of a canal 7 which ends in a triangular pit in ad- vance of the jugular foramen, and transmits a vein from the spiral sinus just mentioned to the inferior petrosal sinus. The cochlear branch of the internal auditory nerve is resolved into a multitude of filaments, which, together with branches of the correspond- ing artery, enter the foramina of the spiral tract at the bottom of the internal auditory meatus. Ascending the canals of the axis of the cochlea, they are reflected outwardly to the osseous spiral lamina, within which they form an intricate plexus, and become associated near its free border with a series of nerve cells. From these the nerve fibres emerge, and enter the membranous spiral lamina, where, with pe- 1 Lamina spiralis membranacea; zona 3 Scala tympani, posterior, interna, or membranacea, or mollis; zona choriacea superior; incorrectly inferior. and pars membranacea; z. cartilaginea 4 Scala vestibuli, anterior, externa, or and membranacea; z. media and mem- inferior; incorrectly superior, branacea; z. nervea and cartilaginea; z. 5 Gyri; ductus spirales; canales. denticulata and pectinata; habenula in- 6 The canal containing the sinus is the terna, or sulcata, and h. externa, den- canalis Rosenthalianus, or c. spiralis ticulata, or perforata, are subdivisions modioli. of the zona denticulata. 7 Aqueduct of the cochlea; aquseductus 2 The communication is named the cochleae. Helicotrema. , THE ORGANS OF SPECIAL SENSE. 627 culiar nerve cells, they form a complex arrangement, the character of which has not yet been conclusively determined. 1 FIG. 378. DISTRIBUTION OF THE COCHLEAE, NERVE. 1, trunk of the cochlear nerve; 2, membranous spiral lamina ; 3. terminal filaments of the cochlear nerve emerging from the osseous spiral lamina to spread themselves in the membranous lamina; 4, orifice of communication of the tympanic and vestibular scalas. The arteries of the cochlea are mainly derived from the cochlear branches of the auditory artery, and, as previously indicated, they follow the course of the cochlear branch of the auditory nerve They term- inate in a capillary net of the lining membrane and spiral lamina of the cochlea, from which veins originate and join the spiral venous sinus within the axis of the cochlea. The spiral sinus communicates by means of a vein with the inferior petrosal sinus. The Internal aud/itory mea'tus 2 is a cylindroid canal about three- fourths of an inch in length, leading from the posterior surface of the petrous portion of the temporal bone, obliquely downward, forward, and outward to the position of the labyrinth. Its bottom is unequally di- vided by a prominent, transverse, crescentic crest into two compartment?, of which the lower is the larger. The upper compartment is subdivided by a vertical ridge into two pits, of which the inner one is the com- mencement of the Fallopian canal for the transmission of the facial nerve, and the outer one corresponds with the superior cribriform spot of the vestibule for the transmission of the superior division of the ves- 1 For a more intimate description of this structure see the admirable researches of Corti and Kolliker. 2 Meatus auditorius interims; foramen, porus, or sinus acusticus. 628 THE ORGANS OF SPECIAL SENSE. tibular nerve to the elliptical saccule. The lower compartment inter- nally is occupied by a spiral tract, 1 pierced with a multitude of minute foramina, for the transmission of the cochlear nerve; externally is a fossa corresponding with the middle cribriform spot for the transmission of the inferior division of the vestibular nerve to the hemispherical sac- cule and ampullae of the superior and inferior semicircular canals. In the posterior wall of the meatus there is a small canal, transmitting the posterior division of the vestibular nerve to the inferior cribriform spot of the ampulla of the posterior semicircular canal. The auditory meatus transmits the auditory and facial nerves, and the auditory artery. The facial nerve enters the Fallopian canal, and pursues its course to emerge at the stylo-mastoid foramen. The auditory nerve divides into two branches, the cochlear and vestiVular nerves. The former resolves itself into numerous filaments, which enter the foramina of the spiral tract to be distributed in the manner indicated. The vestibular nerve divides into three branches, which resolve them- selves into many filaments transmitted through the foramina of the three cribriform spots as above mentioned. The auditory artery, a branch of the basilar, divides into cochlear and vestibular branches, which accompany the corresponding nerves. THE ORGAN OF TASTE. (For an account of the organ of taste, the student is referred to the description of the tongue, page 280.) THE SKIN AND ITS APPENDAGES. The Skin 2 is the organ of touch, 3 and in the healthy condition of the body is among the most sensitive to the impression of pain, through which quality we are led to avoid agencies injurious or destructive to life. By its peculiar constitution it prevents evaporation of the liquids of the body, and yet holds a correlation with other organs in getting rid of an excess of those liquids. In general it is thickest on the most ex- posed parts on the back of the trunk, outer part of the limbs, palms of the hands and soles of the feet. It is thinnest on the eyelids, lips, inner surface of the prepuce, and glans penis. It is flexible, moderately ex- tensible, slightly elastic, semitransparent, and varies in color in different races and individuals. On the palms and soles it is closely covered with 1 Tractus spiralis foraminulosus. 2 Cutis; derma; deris; corium; pellis; integumentum commune. 8 Organon tactus. THE ORGANS OF SPECIAL SENSE. 629 fine parallel ridges, mostly arranged in curving lines, and with peculiar regularity. In other positions it presents fine reticular furrows, and pits from which hairs project. In parts exposed to frequent doubling or flexion it becomes more or less coarsely furrowed or wrinkled, as around many of the joints, and on the forehead. The skin is composed of two principal layers, the dermis and epider- mis ; is provided with two kinds of glands, the sweat and sebaceous glands ; and is furnished with two varieties of appendages, the hairs and nails. THE DERMIS. The Dermis 1 constitutes the deeper layer of the skin, and is thickest where the entire skin presents that condition. It is about one-sixth of a line thick on the eyelids, from one-fourth to one-half a line on the front of the body, and from one-half a line to one and a half lines on the back of the body and the heels. It is thinner in the female than the male ; in children, is about half as thick as it is in adult age, and it becomes thinner in old age. It is of a pinkish cream color, and varies in the depth of pinkish hue in different positions according to its degree of vascularity. The dermis is mainly composed of a dense intertexture of bundles of fibrous tissue, which cross one another at acute angles, in different direc- tions. It is mingled with some elastic tissue, which is most abundant on the front of the body and about the joints. It also contains unstri- ated muscular fibres, which descend from the more superficial part of the dermis to the bottom of the hair follicles. When excited to con- traction, through the impression of cold, the emotion of fear, or the influence of electricity, these muscular fibres elevate the hairs and pro- duce the phenomenon of " goose flesh." 2 The dermis is densest approaching its exterior surface, which is de- fined by a more homogeneous layer or basement membrane. Its in- terior surface is continuous with the connective tissue of the adipose layer of the superficial fascia, or in positions in which the adipose layer is absent it adheres to the deeper layer of the superficial fascia, or other subjacent structure, by more or less long and loose connective tissue, which allows the skin to be moved backward and forward. The interior surface, when freed from its connections, presents the appearance of a coarsely-corded net, with the meshes occupied by small, round masses of adipose tissue. The outer surface of the dermis is provided with a multitude of mi- 1 Derma; derm; cutis; cutis vera; corium; true skin. 2 Cutis anserina. 030 THE ORGANS OF SPECIAL SENSE. FIG. 379. nute processes, which, from their function, have been named the tactile papillae. 1 They vary in number and degree of development in different parts of the body. They are most numerous and longest on the palms and -soles, where they are arranged in double rows supported on linear ridges of the dermis. corresponding with those seen on the surface of the skin. They are also numerous on the prepuce, glans penis, nym- phae, clitoris, and nipple. In other positions they are more widely set apart, less well developed, and on the face are nearly obsolete. The largest or .best developed papillae are conical, and either sim- ple or compound the latter con- sisting of two, three, or even more, springing from a common base. The less well developed pa- pillre are mammillary or wart like, and degenerate into feeble ridges of the surface. In the palms and soles they measure from the one- thirtieth to the one-tenth of a line long, and in other positions descend from the one-thirtieth to one-eight- ieth of a line They are composed of a continuation of the fibrous structure of the dermis, defined by structureless basement mem- brane, and receive terminal filaments of the cutaneous nerves, and each a looped capillary blood-vessel. Some of the papillae of the palm and sole contain peculiar bodies, which have already been described as tactile corpuscles on page 511. The dermis is richly supplied with blood-vessels, lymphatics, and nerves. The arteries of the skin penetrate from beneath, and end in a capillary net-work, which becomes more close the nearer it approaches the exterior surface of the dermis, and from this net-work single loops enter the tactile papillae. The veins emerging from the skin are more VERTICAL SECTION OF THE eKi\ OF THE FORE- FINGER ACROSS TWO OF THE RIDGES OF THE SUR- FACE, highly magnified. 1, dermis composed of an intertexture of bundles of fibrous tissue; 2, epi- dermis; 3, its cuticle; 4, its soft layer; 5, subcu- taneous connective and adipose tissue: 6, tactile papillae; 7. sweat glands; 8, duct; 9, spiral pas- sage from the latter through the epidermis; 10, termination of the passage on the summit of tactus; papillae of touch; papillary layer of the derm; corpus papillare. THE ORGANS OF SPECIAL SENSE. 631 numerous and much larger than the arteries, and end in the superficial venous trunks beneath. The lymphatics also form an intricate net-work in the dermis, and are most numerous on the fore and inner part of the body and limbs, especially in the palms and soles. The nerves are abundant, and are derived from the various cutaneous branches described in the account of the nervous system. They extend to the exterior sur- face of the dermis, and into the tactile papillae ; but their mode of term* ination has not been accurately ascertained. By boiling, the dermis is resolved into gelatin, and indeed the main source of glue used in the arts is obtained from fragments of the skin of animals. By tanning, the dermis is converted into leather; deprived of fatty and other matters, and properly thinned, it forms parchment. The cut edge and rough surface of a piece of leather illustrates the arrangement of the fibrous structure of the dermis, and its smooth outer surface frequently exhibits the mouths of the hair follicles, papilla, and other marks. THE EPIDERMIS. The Epider'mis 1 constitutes the superficial layer of the skin, and holds the same relation to the dermis that the epithelium does to the deeper layer of the mucous membranes. It is thickest in the palms and soles, where it measures from the one-tenth to one line or more, and in other positions forms a thin layer ranging from about ^ to T ! ff of a line. The thickness is however in some measure dependent on the pres- sure or friction to which the skin is subjected, and thus it becomes thicker in the palm of the laborer and the sole of the plowman than in most other persons. Corns are much-thickened portions of the epider- mis in particular spots, which are exposed to excessive pressure or friction. They are not necessarily confined to the feet, but are produced on the knee of the shoemaker from frequent hammering, or in front of the clavicle of the soldier from the pressure of his musket. The pain so frequently induced by their presence is due to their exciting inflammation in the sensitive dermis upon which they press, just as a pebble does under the same circumstances. The epidermis is entirely non-vascular, but derives its nutritive liquid by imbibition from the vessels of the dermis. It is without nerves, and therefore completely insensible; but it transmits impressions through pressure to the exquisitely sensitive dermis, the soft and delicate struc- 1 Cuticnla; cuticle; epiderma; epichorium ; cutis extima; pellis summa; lamina prima cutis; scarf skin. 632 THE ORGANS OF SPECIAL SENSE. ture of which it protects from laceration or drying. If removed, the contact of the atmosphere is sufficient to produce inflammation of the dermis, and after death the latter speedily dries. The epidermis consists of two layers, quite different in many respects ; one being named the cuticle, the other the soft epidermic layer. % % The Cu'ticle 1 is a nearly dry, yellowish, translucent, horn-like mem- brane, well illustrated by the slice of a corn. Its deeper surface is con- tinuous with the soft epidermic layer from which it is incessantly renewed, while from its free surface it is constantly worn away, or is shed in small flakes, constituting the so-called scurf and dandruff. In many lower animals, as for instance serpents, it exfoliates from time to time in an FIG. 380. FIG. 381. SCURF FROM THE LEG. 1, a fragment of scurf, consisting of dried, flattened, non-nucleated cells or scales; 2, a few cells with a nucleus; 3, a cell more highly magnified, to exhibit its polyhedral form. FRAGMENT OF DANDRUFF FROM THE HEAD. 1, por- tion of dandruff, consisting of non-nucleated cells ; 2, several fragments, consisting of nucleated cells; 3, isolated cells, some with and without nuclei : 4. a cell more highly magnified, exhibiting granular contents and a nucleus. entire state. It consists of numerous laminae, according to its degree of thickness, of minute scales, which are completely flattened and nearly dried organic cells. These have a small quantity of granular contents, but usually no nucleus, though frequently the remains of one, especially in the deeper part of the cuticle, may be detected. By treatment with a solution of potash, the scales of the cuticle sep- arate from one another, and swell into spheroidal vesicles. Hence it is that alkaline solutions remove the epidermis. A blister or burn pro- duces inflammation of the dermis and effusion of liquid, which breaks up the soft epidermic layer, and elevates the cuticle. By maceration of the skin after death, the cuticle becomes detached from the dermis through disorganization of the soft epidermic layer. When the cuticle is sufficiently thick and strong to sustain itself, it may be removed in large pieces, and thus from the hand it may be stripped off like a glove. Cuticula. THE ORGANS OF SPECIAL SENSE. 633 The Soft' epidermic layer 1 consists of many laminae of delicate poly- hedral cells with soft granular contents and a nucleus. The upper laminae of cells are successively more and more flattened, and are inces- santly transformed into the comparatively dry scales of the cuticle, while they are as constantly reproduced from the surface of the dermis. In the white race the soft epidermic layer is colorless, and,Tike the cuticle, translucent, and hence it allows the color and vascularity of thP dermis to be seen. In the negro, its cells, especially the deeper ones, are filled with brown or black pigmentary matter, which produces the char- acteristic color of the race. Smaller quantities of the same material give rise to the various shades of complexion of other races, of different individuals, and even different parts of the skin of the same person. The sun-burnt complexion is due to the development or increase of the same coloring matter; and in freckles it is accumulated in spots. As the soft epidermic layer Js transformed into the cuticle, the pigmentary matter disappears from its cells. THE SWEAT GLANDS. The Sweat or perspiratory glands 2 exist almost everywhere in the skin, and number a million or more. They are yellowish-red, spheroidal bodies, averaging about one-sixth of a line in diameter, and are lodged in interspaces of the deep part of the dermis, usually surrounded by adipose tissue. Each gland consists of a tube convoluted into a ball, and afterwards ascending, as the sweat duct, in a slightly tortuous man- ner, to the exterior surface of the dermis. The tube is composed of an exterior fibrous layer, succeeded by one of basement membrane ; and is lined with a pavement epithelium, consisting of polyhedral cells contain- ing a nucleus, and granular contents mingled with some yellowish pig- ment particles. From th>e sweat duct opening on the surface of the dermis a passage way conducts to the exterior of the epidermis. When the latter is thin, the passage is straight ; but when thick, as in the palms and soles, it pursues a spiral course, and terminates in a funnel-shaped orifice. The apertures of the ducts are distinctly visible with a common pocket lens, in 1 Rete mucosnm ; r. Malpighi ; cor- 2 Glandulae sudoripara) : g. miliariae ; pus, or stratum Malpighi; corpus mu- g. hydrophora} ; organa sudoripara; su- cosum ; c. reticulare ; reticulum cuta- doriparous glands ; diapnogenous appa- neum; r. mucosura; mesodermum ; mu- ratus; perspiratory organs; fontes su- cous web ; tunica albida superficialis et doris. profunda, et gemmula, et bourgeons sanguins. 634 THE ORGANS OF SPECIAL SENSE. a single row on the summits of the ridges of the palms and soles ; but in other positions are not so readily distinguished. A modification of the sweat glands constitutes the ceruminous glands, described in the account of the ear, and the odoriferous glands of the axilla. 1 These form a patch, an inch and a half or more in diameter, situated in the subcutaneous connective and adipose tissue of the hairy T>art of the armpit. They are largest near the centre of the patch, and gradually diminish toward the circumference, where they merge into the ordinary sweat glands. They are usually much better developed in the negro, in whom the largest reach the size of a small pea. They are of a dusky, yellowish-red color, and, like the sweat glands, are composed of a tube coiled into a ball, from which the tube continues as the duct to open on the exterior surface of the skin. The tube of the gland con- tains unstriated muscular fibres in its wall ; and its cavity is filled with a finely granular matter mingled with brown or yellow pigment and fat particles. Besides an abundance of sweat, these glands yield a strongly odorous substance, which is somewhat peculiar in the different races. Sweat 2 is a clear, watery liquid, with an acid reaction and a saline taste. It contains formic, butyric, and acetic acids, and a number of salts, of which the most abundant is chloride of sodium. THE SEBACEOUS GLANDS. The Seba'ceous glands 3 of the skin are very numerous, and exist almost everywhere, except in the palms and soles. They are mostly associated with the hair follicles, being situated around them in groups from two to eight for each follicle, imbedded in the more superficial part of the dermis. Generally the largest glands are found with the small- est hair follicles, so that these appear of secondary importance, while the smallest glands exist in pairs in connection with the hairs of the scalp. The largest sebaceous glands are those of the nose, concha of the ear, skin of the penis, the scrotum, labia, and areola surrounding the female nipple. The groups of glands connected with each hair follicle appear as rounded whitish bodies imbedded in the semitransparent skin, and measure from one-tenth to one-half a line or more in diameter. 1 Glandulae odoriferae of Homer. sebiferse 1 ; cryptae sebacese; folliculi se- 2 Sudor; perspiration; perspiratory baceae: sebiparous, or sebiferous fluid. glands; sebaceous follicles, or crypts; 3 Glandulae sebaceae ; g. sebiparae ; g. miliary glands ; oil glands. THE ORGANS OF SPECIAL SENSE. 635 The sebaceous glands are simple or compound, being composed of one or more purse-shaped pouches, the ducts of which open into the FIG. 382. FIG. 383. SEBACEOUS GLANDS OPENING INTO THE MOUTH OF A HAIR FOLLICLE, much magnified. mouths of the hair follicles, or in the case of the largest glands, together with the latter they open on the sur- face of the skin. In structure the glands possess a delicate wall of fibrous tissue, defined by a base- ment membrane, and are lined with an epithelium consisting of polyhe- dral, nucleated cells with granular contents. The cavity of the glands is filled with sebaceous matter, 1 consisting of cells and oil globules. Of the cells, some contain finely granular matter mingled with oil drops, while others are distended with oil. The sebaceous matter anoints the hairs with oil in their progress of growth from the skin, and also imbues the cuticle, by which it is rendered repellant of water. The greasiness of the surface of the skin, occa- sioned by this material, permits the ready adhesion of dust and dirt, and renders the employment of soaps necessary for easy removal of its excess. The too free use of alkaline washes, by depriving the cuticle of its oil, produces a dry and harsh feeling in the skin. The sebaceous matter often becomes inspissated and distends the glands, most frequently in the face, and especially on the nose ; and at the mouths of the ducts it A LARGE SEBACEOUS GLAND FROM THE NOSE, viewed by transmitted light, and highly magnified, a, epithelium of the gland ; 6, the same continuous with the epidermis; c, the sebaceous matter; d, subdivisions of the gland ; e, a hair follicle ; /, a hair. Sebum, or sraegnia cutaneum. 636 THE ORGANS OF SPECIAL SENSE. becomes incorporated with dirt. By pressure it is squeezed out, and from its assuming the form of the duct, is vulgarly taken for a worm, of FIG. 384. FIG. 385. Fig. 384. SEBACEOUS MATTER, FROM ONE OF THE SEBACEOUS GLANDS OF -HE NOSE, magnified. 1, cells filled with granular matter ; 2, one of the cells more highly magnified; 3, oil drops mingled with the cells. Fig. 385. STRUCTURE OF THE SEBACEOUS GLANDS. A, a simple sebaceous gland, or one of the divisions of a compound gland, highly magnified, a, epithelial cells; 6, sebaceous matter. B, sebaceous cells, much more highly magnified, a, small cells from the epithelial layer ; b, larger cells abounding in fat; c, cell in which the fat has accumulated in large drops; d, cell distended with fat; e,f, cells from which the fat has partially escaped. which the dirt at the end is supposed to be the head. The sebaceous matter, nevertheless, even in most healthy individuals, contains a curious parasitic animal, the pimple mite. 1 THE HAIRS. The Hairs 2 are solid, thread-like appendages of the skin, projecting from almost every part of its surface except the palms and soles. They are flexible, elastic, and shining, but vary in degree of development, fineness, color, form, and arrangement in different races, sexes, individ- uals, and parts of the body. From the long hairs of the head 3 they exist of every gradation of size to such 4 as are hardly visible. The portion of a hair projecting from the skin is its shaft or stem 5 terminated by the point or end ; the portion inserted into the skin is the root, 6 which begins in a club-like expansion, named the bulb. 7 The hairs generally project obliquely from the skin, singly, or in groups of two, three, or more. They are regularly arranged in the dif- ferent parts of the body, mostly in curving lines or whorls from particu- lar points. 1 Acarus folliculorum ; Demodex folliculorum. 2 Pili; the hair; crinis; pile; thrix. 3 Capilli. 4 Lanugo ; down. 5 Scapus. e Radix pili. 7 Bulbus pili; button. THE ORGANS OF SPECIAL SENSE. 637 The fine silken hair of the head of the white race is cylindrical ; the crisp, curling hair of the beard, other parts of the body, and the head of the negro, is more or less flattened cylindrical. In structure the hairs consist of an exterior cuticle, a cortical sub- stance, and an interior medullary substance. FIG. 386. A ^v .# FIG. 387. A. PORTION OF THE SHAFT OF A LIGHT HAIR, mag- nified. The longitudinal lines are produced by the cortical substance; the transverse, undulating lines, by the cuticle. B. Isolated scales of the cuticle. The cuticle of the hair consists of a single layer of thin, colorless, quadrilateral scales or completely flattened cells, which overlap like the shingles of a roof. The projecting edges of these scales are directed upward and outward along the shaft; and in a hair examined be- neath the microscope are seen as irregularly undulating and intersecting transverse lines. As feebly as their edges appear to project, they nevertheless present an obstacle to the hair being moved in any other direction than with its root forward, when rubbed between two surfaces. It is upon a similar condition that the felting of the hair and wool of various animals depends. The cortical substance 1 makes the chief bulk of the hair, and is that upon which the color mainly depends in different races and individuals. When sufficiently translucent, as in white or light-colored hairs, beneath the microscope it presents a longitudinally striated appearance. It is composed of layers of flexible fibres, into which it is not unfrequently found more or less split at the ends of hairs, as the result of dry- ing and friction. The fibres consist of much elongated, fusiform cells containing a linear nucleus. The coloring matter is usually dif- itil PORTION OF A HAIR FROM THE OUTER PART OF THE THIGH, magni- fied. 1, shaft of the hair covered with transverse markings indicat- ing the projecting edges of the cu- ticular scales ; 2, cortical substance at the end of the hair broken up into coarse fibres as the result of friction of the clothing. 1 Cortex. 638 TH E ORGANS OF SPECIAL SEXSE. fused through the cortical substance, though it is also often accumulated in streaks or spots. With the loss of the coloring matter, generally occurring in the advance of age, the cortical substance becomes white. The medullary substance 1 is frequently absent, especially in dark- colored hairs of the head, and in fine down-like hairs of the body. It occupies the axis of the hair, and by transmitted light appears as a dark, coarsely granular streak, usually of uniform diameter, but often con- tracted, and sometimes completely interrupted in its course. By re- flected light it appears white, though modified by the color of the cortical substance through which it is seen. It consists of somewhat cuboidal cells, with granular contents and an indistinct nucleus. The medullary substance is generally mingled with more or less air, in small bubbles, which penetrates from the ends of the hairs, and gives to these when white the characteristic silvery lustre. The root of the hair is lodged in a flask-shaped receptacle of the skin called the hair follicle, 2 at the bottom of which is a papilla from which the hair grows. The hair follicles are imbedded in the derails, or, in the case of the large hairs, extend into the subcutaneous connective and adipose tissue. They may be viewed as inflections of the skin, and the hair papilla at their bottom as a modified tactile papilla. The wall of the hair follicle is composed of a fibrous layer defined by a basement membrane, and lined with an inflection 3 of the epidermis. The cuticular portion 4 of this inflection is remarkably modified from the corresponding layer on the free surface of the skin. It forms a com- paratively thick, transparent, elastic membrane, composed of somewhat elongated non-nucleated cells, adhering to one another in such a manner as to assume the appearance of fenestrated membrane. The elastic cuticular layer merges into the softer epidermic layer beneath, and tightly clasps the root of the hair. It perhaps acts upon the latter as it is projected in its growth from the papilla, as a wire is acted upon when it is protruded through a draw-plate. The hair papilla 5 is ovoid, of soft consistence, and supplied with both capillary vessels and nerves. The hair bulb caps or incloses the papilla, 1 Medulla. 4 Inner root sheath of the hair. The 2 Folliculus pili. softer cells beneath constitute the outer 3 Root sheath of the hair; vagina pili. root sheath. 5 Papilla pili ; pulpa, or blastema pili. THE ORGANS OF SPECIAL SENSE. 639 and in the extraction of a hair it is traction on the latter which gives rise to the pain. The root of the hair is softer and thicker than the shaft, the character of which it assumes in its growth. The hair bulb is soft, translucent, and is continuous at the bottom of the hair papilla with the epidermic layer of the hair follicle. It is com- posed of soft, polyhedral nucleated cells, which exhibit a gradual and successive transition into the cu- ticle, cortical and medullary sub- stances of the root above. By the FIG 380. FIG. 388. -4- Fig. 388. ROOT OF A HAIR LODGED WITHIN ITS FOLLICLE, magnified, a, shaft of the hair; b, root; c, bulb : d, cuticle of the hair; e,f, epidermic lining of the follicle; g, basement membrane; h, fibrous layer of the wall of the hair follicle; i, hair papilla; k, mouths of two sebaceous glands; I, derrnis; m, soft layer of the epidermis; n, cuticle of the epidermis. Fig. 389. DIAGRAM OF STRUCTURE OF THE ROOT OF A HAIR WITHIN ITS FOLLICLE. 1, hair papilla; 2, capil- lary vessel; 3, nerve fibres; 4, fibrous wall of the hair follicle; 5, basement membrane; 6, soft epider- mic lining of the follicle; 7, its elastic cuticular layer; 8, cuticle of the hair; 9, cortical substance; 10, medullary substance; 11, bulb of the hair composed of soft polyhedral cells; 12, transition of the lat- ter into the cortical substance, medullary substance, and cuticle of the hair. transformation of the cells into the elements just mentioned, and the pro- duction of new cells from the papilla, the hair constantly grows in length. Like the epidermis the hairs receive nutriment by imbibition the liquids being transmitted from one cell element to another in gradually diminishing quantity throughout the length of the hair. 640 THE ORGANS OF SPECIAL SENSE. The hairs are not only renewed by constant growth, but in many in- stances, even in the healthy condition, but especially after diseases, they are cast off or shed, and new ones are produced. In such instances, likewise when the hairs are violently extracted, the new hairs are pro- duced from the same hair follicles, but sometimes at least from new pa- pillae. Permanent baldness, so often occurring in the advance of age, arises from atrophy of the hair papillae. The apparent growth of the beard after death arises from the shrink- ing of the skin, which protrudes the remaining roots of the hairs the eighth of an inch or more. THE NAILS. The Nails 1 are corneous appendages of the skin, and correspond with the claws and hoofs of other animals. They are thin, flexible, translu- FIG. 390. FIG. 391. FIG. 392. Fig. 390. MATRIX OF THE NAIL. 1, fold of the skin which covers the root of the nail ; 2, the fold par- tially turned up to show the depth of the groove beneath ; 3, 4, posterior and anterior portions of the matrix, the former the less vascular, and giving rise to the appearance called the lunula. The longitudi- nal lines indicate the ridges bordered with papilla;. Fig. 391. UNDER SURFACE OF THE NAIL. 1, root; 2, part corresponding with the lunula; 3, grooved sur- face adapted to the ridges of the matrix ; 4, free border. Fig. 392. VERTICAL SECTION OF THE END OF A FINGER. 1, epidermis on the back of the finger; 2, point at which it is reflected to become continuous with the nail; 3, the nail; 4, epidermis at the end of the fin- ger; 5, 6, 7, 8, surface of the dermis corresponding with the position of the soft epidermic layer; 9, 10, 11, 12, dermis; 13, last phalanx; 14, flexor tendon. cent, quadrilateral plates continuous with the epidermis, and resting on a depressed surface of the dermis, called the matrix or bed. The exposed portion of the nail, named its body, is terminated ante- riorly by the free border. The posterior third or fourth of the nail, named its root, is lodged in a deep groove 2 of the matrix, and the lateral borders are received into shallow grooves. From the body of the nail the root gradually thins away to a sharp edge, and the lateral borders more abruptly thin out. 1 Ungues. 2 Vallecula unguis ; nail follicle. THE ORGANS OF SPECIAL SENSE. The translucency of the nail permits the redness of the matrix to be seen, which color is due to vascularity of the part. The less degree of vascularity of the matrix at the root, defined by a semicircular line, gives rise to the whitish spot called the lu'nula. 1 The free surface of the body of the nail is shining and faintly striated longitudinally ; its under sur- face is finely grooved in the same direction. The matrix of the nail, constituted by a highly vascular portion of the dermis, is covered with fine longitudinal ridges beset with a multitude of minute papillae. The ridges and papillaa fit into the grooves of the under surface of the nail, and correspond with the tactile papillae in other positions. By maceration the nails become detached continuously with the epi- dermis from the dermis. They consist of a thick horny layer attached by a delicate soft layer to the dermis. The horny layer answers to the cuticle of the epidermis, and is com- posed of numerous intimately associated laminae of flattened nucleated cells or scales, which can only be distinguished microscopically after treatment with certain chemical reagents, as the alkalies. The soft layer 2 of the nails corresponds with that of the epidermis, and like it is composed of delicate, polyhedral nucleated cells. These are incessantly transformed into the scales of the horny layer, and are renewed from the surface of the dermis. By the constant addition of cells at the root, the nail grows in length ; by addition beneath, they grow in thickness. 1 Semilunula; arcus; albedo unguium. 2 Stratum Malpighi; soft mucous layer; stratum mucosum. 41 INDEX. ABDOMEN 211 cavity of 298 Abdominal parietes 211 ring, external 213, 220 internal 219 walls 211 Abduction 47 Abductor of great toe 257 of little finger 237 of little toe 258 of thumb 236 Accessory flexor of the foot 256 parotid gland 279 Acetabulum 124 Acid, butyric 29 carbonic 29 chloro-hydric 28 formic 29 lactic 29 Acini of thymus body 457 Acromion 132 Adduction 47 Adductor of great toe 257 of little finger 237 of thumb 236 great 250 long 249 short 250 Adam's apple 193, 440 Adipose tissue 176 Afferent vessels 429 Air-cells 452 Alar folds 162 Albumen 26 Albuminose 26 Albugineous tunic of testis 470 Alimentary apparatus 273 canal 273 Allantois 463 Alveolar border 77, 84 Alveoli 77 Ammonia, urate of. 29 Ampulla 623 Anatomy 17 Anastomoses 333 Angle, facial 88 Angles of the eye 595 Ankle 152, 153, 238 Ankle bone 153 joint 163 Antihelix 613 Antitragus 613 Anus 318 internal sphincter of. 319 pouches of 319 Anvil 619 Aorta 351 abdominal 383 thoracic 381 Aortic orifice 222 Aperture of the larynx 445 Aponeuroses 180 Apparatus, lachrymal 598 Appendages of the eye 594 Aqueous humor 610 Arachnoid membrane 539 Arch of aorta 351 deep palmar 378 plantar 404 superficial palmar 380 zygomatic 88, 89 Arches, palatine 276 Arciform fibres 531 Arcus senilis 604 Areola 500 Areolar tissue 170 Arm 223 Arm bone 132 Armpit 228 Arteries 332, 351 anterior intercostal 371 articular 400 bronchial 382, 4~>3 calcanean 403 cerebellar, inferior 368 common iliac 390 digital of superficial palmar arch 381 of plantar arch 404 external pudic 396 helicine 478 ileal 387 (643) 644 INDEX. Arteries, inferior articular 400 Artery, interosseous . 379 intercostal 382 communicating RRO anterior branches of 383 coronary 384 dorsal branches of 383 left 353 interosseous of palmar arch 378 right 858 ieiunal .. 387 cystic 385 lateral sacral 392 deferent 393 473 lumbar 389 dental of inferior maxillary 862 anterior branches of 389 descendin** palatine 868 389 359 spinal branches of 389 dorsal lingual 356 mediastinal 371, 382 dorsal, of clitoris 8% oesophageal 382 of great toe '102 ovarian 390 of penis 895 pancreatic 386 pedal 401 perforating, of internal inaru- scapular 374 marv... 371 duodenal 387 of plantar arch 404 epigastric 3% of profound femoral 397 external carot id 355 pericardiac 382 iliac 89fi phrenic ... 389 malleolar 401 renal 390 plantar 404 short gastric 386 facial 357, 358 spermat ic 390 fern oral 306 splenic branches of splenic 386 frontal 866 superior articular 400 gastro-epiploic right 385 supra-renal 390 duodenal 885 tarsal .. .. 401 srluteal. . 393 vesical 393 great meningeal 361 Artery angular . ... 358 hsjmorrhoidal, inferior 394 acromial thoracic 373 middle 394 anastomotic 37G 398 superior 888 anterior auricular 360 hepatic . . . 885 carpal 377 380 left 386 cerebral 366 right 385 ciliary 365 hyoid branch of superior thyroid 356 circumflex 374 ilio-colic 387 communicating 366 ilio-lumbar 39? dental of infra-orbital 36 inferior coronary 858 ethmoidal 365 maxillary . . 861 interosseous 379 mesenteric 388 nasal 366 palatine 358 spinal 368 profound 375 360 thyroid 370 tibial 400 401 vesical .. 893 ascending cervical 371 infra- orbital 3 (5? axillary 372 innominate.. . 353 basilar 368 ischiatic 895 brachial 374, 376 internal auditory 369 394 carotid 363 394 circumflex 398 central retinal 365 iliac 391 choroid 366 401 365 371 loner.... 365 maxillary 361, 362 " . short 365 plant ar 403 circumflex iliac 396 pudic 393 colic left 388 380 middle 387 365 right . .. 387 laryngeal 356 354 lateral nasal 358 right... 354 lingual... 356 INDEX. 645 Artery, long thoracic medullary nutritious meningeal branches of anterior eth- moidal branches of occipital metacarpal inetatarsal middle articular of popliteal.... cerebral sacral temporal muscular branches of superior thyroid musculo-phrenic nasal obturator occipital ophthalmic 364, pancreatico-duodenal palpebral parotid branches of external carotid permeal peroneal anterior posterior pharyngeal popliteal.. 399, posterior auricular carpal 378, cerebellar circumflex communicating dental, of superior maxil- lary . ethmoidal interosseous scapular temporal tibial , 402, principal, of the thumb profound cervical femoral pulmonary left right pyloric radial 37G, 373 376 403 368 recurrent, index... ranine recurrent tibial.... sigmoid small meningeal spheno-palatine spinal branches of vertebral splenic subclavian, left right sublingual 366 359 378 402 400 366 389 360 356 372 366 392 359 365 385 366 359 394 403 403 356 400 359 380 369 374 366 362 365 380 370 360 403 378 372 397 453 405 405 385 377 377 378 356 401 388 361 363 368 368 386 367 367 356 Artery, sub-maxillary branches of facial 358 submental 358 subscapular 374 superficial circumflex 397 epigastric 397 superior cerebellar 369 cervical 370 coronary 358 epigastric 372 intercostal 372 maxillary 362 mesenteric 386 phrenic 371 profound 375 thoracic 373 thyroid 355 vesical 393 stylo-mast oid 359 supra-orbital 360, 365 supra-scapular 370 temporal 360 tonsillar '. 358 transverse facial 360 perineal 394 tympanic 361 ulnar, and ulnar recurrent 379 uterine 305 vaginal 395 vertebral 367, 368 volar : 377 Articular borders 34 cartilage 48, 174 extremities 34 process 34 surfaces 34 Articulation, carpo-metacarpal 147 crico-arytenoid 443 crico-thyroid 442 inferior radio-ulnar 145 tibio-fibular 163 intercarpal 147 middle radio uluar 145 radio-carpal 146 scapulo clavicular 142 sterno-clavicular 141 superior radio-ulnar 145 tibio fibular 163 temporo-maxillary 86 Articulations 46 costo-sternal 119 costo-vertebral 118 immovable.... 46 intertarsal 164 metacarpo-phalangial 147 metatarso-phalangial 1 66 movable 46 of the atlas Ill axis Ill hip bones 125 lower extremities 158 occipital bone Ill 646 INDEX. Articulations of the ribs 118 of the sternum 118 upper extremities 141 vertebral column 107 Arytenoid cartilages 441 Auditory meatus, external 63 internal 63 process 63, 64 Axis 101 cerebro-spinal 503, 513 coeliac 384 fibre 505 of the pelvis 127 Aryteno-epiglottic folds 445 Astragalus 153 Asperous ridge 148 Atlas 100 Auricle of the ear 612 of the heart 343 left 344 right 343 Auricular appendage 343, 344 Auriculo-ventricular orifice, left, 344, 347 right 344, 345 Axilla 223 BASILAR process 51 Base of the skull 90 Basement membrane 262 Band, semicircular 524 Back 200, 203 of hand 223 Ball of the thumb 222 Band-like ligaments 48 Belly 211 cavity of 298 muscles of 178 Bile ducts 324 Biliary duct, common 328 Biliverdin 29 Bladder, ligaments of. 403 urinary 300, 462 Blood 338 corpuscles 339 colorless 340 red 339 liquor 340 Bodies, geniculate 524 nerve capsular 510 olivary 530 Pacchionian 536 pyramidal 530 quadrigeminal 525 restiform 531 striated 523 supra-renal. 465 Body, ciliary 605 dentated 528, 531 of bone 34 of teeth 285 quadrigeminal 525 pituitary 518 Body, striated 523 thymus 456 thyroid 455 Bone, occipital 50 arm 132 canaliculi of. 41 capitate 138 collar 129 cuboid 154 cuneiform 137 ethmoid 56 frontal 58 hip 121 hyoid 96 inferior maxillary 83 innominate 121 lachrymal 80 lacunae of. 41 lunar 137 malar 83 nasal 81 palate 78 parietal 60 pisiform 137 scaphoid, of carpus 137 scaphoid, of tarsus 154 shin 150 sphenoid ni* superior maxillary , 76 temporal 61 thigh 148 trapezial 137 trapezoid 137 turbinated 81 unciform 138 vascular canals of.. 40 Bones, articular extremities of. 34 articular process of 34 body of 34 borders of 34 canal of 34 canaliculi of. 41 carpal 136 compact substance of. 36 condyles of 34 crest of 34 cuneiform, of tarsus 155 diaphysis of 42 distal extremity of 34 endosteum of 39 epiphyses of. 42 foramen of 34 fossa of 34 head of 34 irregular 34 lacunae of 41 line of 34 long 34 marrow of 36 meatus of 34 medulla of 36 medullary cavity of 36 INDEX. 647 Bones, metacarpal 138 metatarsal 156 neck of 34 periosteum of 39 process of 34 proximal extremity of 34 ridge of 34 sesamoid 140, 157 shaft of 34 short 34 sinus of 34 spinous process of. 34 spongy substance of 36 surface of 34 tabular 34 tubercle of 34 tuberosity of 34 vascular canals of 40 Brain 503, 513, 514 gray substance of 503, 505 white substance of. 503, 504 ventricles of. 521, 523, 531 Breasts 499 Bromine 21 Bronchi 448 Bronchial arteries 453 tubes 453 veins 453 Bronchus, left 449 right 448 Brunner's glands 312 Bulb, olfactory 540 Bundles of muscles 178 Bursse, synovial 183, 265 Buttocks 238 Butyrin 27 CAECUM 315 Calcaneum 154 Calcium 21, 25 Calyces 461 Canal, alimentary 273 anterior dental 77 carotid 65 infra-orbital 77 inguinal 219 lachrymal 599 naso-palatine 78 posterior dental 77 posterior palatine 79 pterygoid 56 pterygo-palatine 56, 80 sacral 105 semicircular 623 spinal 114 Canals, semicircular 622, 623 vascular of bone 40 Canine teeth 287 Capillaries 337 Capitate papillae 282 Capsular ligaments 48 Capsule of the lens 611 Carbou 21, 25 Carbonate of lime 28 of magnesia 28 of soda 28 Carbonic acid 29 Cardiac orifice of stomach 305 Carneous columns 345 Carotid canal 65 Carpal bones 136 Carpus 136, 223 Cartilage 171 articular 48, 174 ensiform 117 Cartilages, costal 114, 116 of the larynx 440 of the nose 589 palpebral 596 permanent 172 temporary 172 Cartilaginous rings of bronchi 449 Caruncle, lachrymal 598 Caruncles, myrtiform 490 Casein , 26 Cava, inferior 420 superior 406 Cavernous bodies 476 of clitoris 493 of penis 476 Cavities, nasal 591 Cavity of the uterus 482 Cell, hepatic 326 organic 22 Cells, spermatic 472 Cellular layer of membranes 259 Cement of teeth 289, 291 Centres of ossification 42 Cerebellar falx 538 Cerebellum 526 cortical substance of 527 medullary substance of. 527 Cerebral falx 538 Cerebro -spinal axis 503, 513 liquid 539 Cerebrum 515 convolutions of 515, 516 cortical substance of 516 crura of 516 hemispheres of 515 lobes of 515 medullary substance of 516 Cerumen 616 Cervical vertebrae 99 triangles 199 Chambers of the eye 610 Cheek bone 83 Cheeks 275 Chest 119, 200 Chlorine 21, 25 Chloride of sodium 28 of potassium 28 Chloro-hydric acid 28 Cholesterine..., 29 648 INDEX, Chondrigen 26 Corpuscles colostrum 502 Choroid coat 604 lymph .. 1SO plexuses 523, 536 mucous 967 604 of blood R39 Chyle 430 Pacinian 510 receptacle of 431 splenic 3 9() Ciliary body . 605 tactile. . 511 630 motion 261 Cortical layer of the supra-renal muscle 605 bodies 466 processes 605 substance of cerebellum ^07 zone 612 of cerebrum 516 Circle of Willis 369 of hair 637 Circumduction ... 47 of the kidneys 459 Circumvallate papillss 282 Costal cartilages 116 Clavicle 129 Cranial fossa anterior 67 53 middle 68 Clitoris 492 posterior 68 Clot of blood. 340 Cranium 67 Coagulum 340 vault of . . . 69 Coats of the arteries 333 Cream 509 of the veins 336 Creatin ?9 Coccyx 105 Creatinin 29 Cochlea 624 Crest of bone 34 axis of 625 ethmoidal 56 Coeliac axis . 384 frontal 59 Collagen 26 occipital .. . . 5?, Collarbone 129 sphenoidal 54 Colon 315 urethral 479 Colostrum 502 Cribriform fascia 2^9 241 43 corpuscles 502 plate of ethmoid bone 57 Column vertebral 97 113 spot inferior 6^3 Commissure . ... 514 middle 69?, optic 518 superior 69,9, great cerebral 519 441 Cross occipital 59 cord 514 Crown of head 184 of mouth 274 of teeth 985 of the third ventricle 526 Crus of diaphragm left 999, of vulva 492 ri^ht .... 999, Companion veins 335 Crura of cerebellum 59,8 Concha 613 516 Condyles 34 of diaphragm 9,9,9, occipital 51 of fornix 591 of femur 149 Crystalline 27 of humerus 133 lens .. 610 of inferior maxillary bone 85 63?, Condyloid. foramen ... ... 51 637 134 Cystic duct 3?8 Confluence of the sinuses 409 282 DARTOS .. 468 Conjoined tendon 215 486 Conjunctiva . . 597 77 Connective tissue 170 posterior 77 349 groove ... 292, 9,93 516 ligament . 9,86 Coracoid foramen 130 pulp 291, ?,9?, ligament . 130 9,99, notch 130 Dent at ed band 5?,2 603 5?8 519 ?90 487 ?,89 striatum... 523 Dermis... 629 INDEX. 649 Descriptive anatomy 17 Diaphragm 221 Diaphysis of bones 42 Dilatation of heart 349 Disks, intervertebral 107 Dorsal vertebrae 102 Drum of the ear 616 Duct, common biliary 328 cystic 328 hepatic 324, 328 lachrymo-nasal 91, 600 lactiferous 501 of glands 269 of Miiller 489 pancreatic 320 parotid 279 right lymphatic 430, 432 spermatic 472 submaxillary 279 thoracic 430, 431 Ducts, ejaculatory... 474 Duodenal glands 312 Duodenum 309 Dura mater 537 EAR 612 external 612 internal 621 ligaments of 613, 619 middle 616 muscles of 614, 620 small bones of 618, 619 wax 616 Efferent lymphatic vessels 429 Egg 486 Ejaculatory ducts 474 Elastic tissue 175 Elbow joint 144 Eminence, nasal 58 parietal 60 pyramidal 622 Eminences, mammillary 518 Enamel 285, 289, 290 organ. 293 Endocardium 347 Endolymph 623 Endosteum 39 Ependyma 537 Epidermis 259, 631 Epigastric fold 220 region 299 Epiglottis 441 Epiphyses of bones 42 Epiploic appendages 317 Epithelium 259 ciliated 261 columnar 260 irregular 260 pavement 260 polyhedral 260 spheroidal 260 squamous 260 Erectile tissue 476 Ergot 523 Eruption of temporary teeth 293 permanent teeth 294 Ethmoidal crest 56 fissure 59 gutters 57 sinuses 57 wings 56 Ethmoid bone 56 Eustachian tube 65, 621 valve 344 Excretion 267 Extremities, lower 238 upper 223 Eye 594 Eyeball 594, 600 Eyebrow 595 Eyelashes 597 Eyelids 595 Eye teeth 287 FACE 87 Facial angle 88 Falciform process 240, 243 Fallopian canal 63 tube 488 False vocal cords 447 Falx, cerebellar 538 cerebral 538 Fang of tooth 285 Fascia 182 cervical 194 cribriform 239, 241 crural 239, 241 deep 224, 239 perineal 497 temporal 185 femoral 239 ischio-rectal 497 lata 239 lumbar 218 of the foot 239 palmar 225 pectineal 240, 243 pelvic 496 plantar 242 recto-vesical 497 sartorial 240, 243 spermatic 469 superficial 212,224, 238 superficial perineal 497 superficial temporal 185 transverse '. 216, 218 Fasciculi of muscular fibres 178 Fat tissue 176 Fauces 276 Femoral arch 214, 243 hernia 243, 244 ring 243 Femur 148 Fenestrated membranes 334 42 650 INDEX. Fibre, muscular 178 Fibres, striated muscular 181 unstriated muscular 271 Fibrils, muscular 181 Fibro-cartilage 173 interarticular 86, 142 se tnilunar 1 60 Fibro-serous membranes 264 Fibrous tissue 167 Fibula 152 Filaments, homogeneous 30 Fimbriated extremity of Fallopian tube 488 body 522 Fingers 139 Fissure of the anus 238 ethmoidal 59 glenoid 62 great longitudinal 515 longitudinal, of liver 323 oral 274 transverse, of liver 323 of the vulva 492 Flesh 178 Flexion 47 Flexure, sigmoid 315, 316 Fluoride of calcium 28 Fluorine 21 Fold, alar 162 ary teno-epiglottic 445 axillary 223 epigastric 220 glosso-epiglottic 445 recto-uterine 304, 484 recto- vesical 304, 463 semilunar 598 utero-vesical 463 vesico-uterine 304, 463, 484 Follicular glands 269 Fontanel, anterior 74 lateral 75 posterior 75 Fontanels 74 Foot 148, 157 arch of 157 hollow of 157 sole of 157 Foramen, of bone 34 anterior ethmoidal 92 anterior palatine 78, 90 condyloid 51 coracoid 130 infra-orbital 77 jugular 69 lacerated 68 obturat or 1 24 of Winslow 302 optic 55 oval, of sphenoid bone 56 of heart 344 posterior ethmoidal 92 posterior palatine 90 Foramen, quadrate rotund sphenoidal spheno-palatine spheno-maxillary spinous spinal stylo-mastoid supra-orbital Foramina, inter- vertebral great sciatic sacral small sciatic Forearm Fornix Fossa of bone glenoid hemielliptical hemispherical infra-clavicular infra-spinous intercondyloid ischio-rectal jugular 64, 193, navicular ptery go-maxillary spheno-maxillary submaxillary subscapular supra-clavicular 193, supra-spinous temporal trochanteric cranial, anterior middle.... posterior inguinal, internal.... external nasal Fourchette Fraena, glosso-epiglottic. Fraenum, inferior labial. lingual preputial -superior labial../.... Fringes, synovial Frontal bone Front teeth Fundus, of gall-bladder. of urinary bladder.. of uterus Furrow, naso-labial 220, 220, ,49, 223 56 55 80 89 56 98 64 58 98 126 105 126 223 521 34 62 622 622 200 130 149 497 199 479 89 89 199 130 199 130 88 148 67 68 68 304 304 92 492 280 275 280 475 275 265 58 286 328 463 482 184 GALL-BLADDER 328 Ganglia 512 Gangliated cord 582 Gangliform enlargement of the fa- cial nerve 552 Gangliform plexus 555 Ganglion, inferior cervical 584 jugular 555 middle cervical 584 INDEX. 651 544 Glans of the penis 475 otic.... 550 of the clitoris 493 petrous 554 Glenoid cavity 131 semilunar of solar plexus 586 fissure 6? 543 fossa 62 546 tubercle fi*? 550 Globulin 97 583 Glomerule renal . 460 512 Glosso-epiglottic frseua ^80 309 folds 445 General anatomy 17 Glottis 447 Germinal eminence 486 Glucose ?8 spot 487 Glvcosren. .. ?,7 vesicle 487 Grape sugar ?,8 Gimbernat's ligament 215 243 Gray substance 505 Glabella. ... 183 Grinders >>88 Gland 267 Gristle '. 171 500 Groin 212 9R8 parotid 278 Groove, bicipital 133 pineal 526 dental 292, ?93 prostate 480 digastric 6? sublingual 279 labial 184 submaxillary 279 labio-mental 184 Glands agminated 312 313 Gubernaculum of testicle 469 Bartlioline's 494 Gullet >97 bronchial 436 Gums ... >73 Brunner's 312 Gutters, ethmoidal 57 ceruminous 616 Guttural region qo coeliac 439 convoluted 270 HAIRS 636 Cowper's 481 Ham ?51 deep inguinal 437 strings 9 51 duodenal 312 Hand 140 follicular 269 Handle of sternum 117 o-astric 308 Hard palate 975 iliac external 437 Head 183 internal 437 of bone. . 34 intercostal 436 of muscle 179 lachrymal 598 Heart 341 lingual 283 Heel... >38 lumbar 438 Helicine arteries 478 lymphatic 428 429 Helix 613 mediastinal anterior 436 Hemispheres of the cerebellum 597 posterior . . .... 436 of the cerebrum 515 mesenteric ... 438 Hepatic cells 3?6 mesocolic '. 438 duct 324, 3?8 odoriferous 634 substance 3 'M palatine 275 Hernia 990 palpebral 596 femoral 243 944 perspiratory 633 inguinal direct 991 Peyer's 313 oblique ... 990 popliteal 437 Hernial sac ... ... 220 944 preputial 476 Hilus of kidneys 458 pulmonary 436 of spleen 399 racemose... . 270 of supra-renal bodies 466 sebaceous 634 Hip... ?1?, simple follicular 276 bones 1 9 1 solitary 812 313 318 joint 159 suburethral 481 494 Hippocampus fi99 superficial inguinal 437 Hollow of the foot 157 sweat 633 of the knee . '>38 tubular... . 269, 312, 318 Homogeneous filaments... . 18. 30 652 INDEX. Homogeneous granules 18, 29 liquid 18, 29 membrane 19, 30 Horns of the lateral ventricles 522 Human anatom} T ."..... 17 Humerus 132 Humor, aqueous 610 vitreous 611 Humors of the eye 600 Hyaloid tunic 612 Hydrogen 21 Hymen 490 Hyoid bone 96 Hypochondriac regions 299 Hypogastric region 299 ILEUM Ileo-colic valve Iliac regions Ilium Ilio-pectineal line Ilio-pubic eminence Incisors Infundibulum Inguinal canal fossae, external internal 220, hernia, direct oblique region Innominate bones Inosit Instep Intermuscular partitions Interposed velum 524, Interver t ebral disks foramina ligaments notches Intestinal juice Intestine large small Iodine Iris Iron 21, Irregular bones Ischium plan e of Ivory 310 316 299 121 126 124 286 518 219 220 304 221 220 212 121 28 157 182 535 107 98 107 98 313 309 315 309 21 607 26 34 121 124 289 JAW BONE, lower 83 Jejunum 310 Joints 46 Jugular foramen 51, 69 fossa 64, 193, 199 KIDNEYS 458 Kneecap 150, 238 joint 160 Knuckles... ,.140 LABIA, of the vulva 492 Labial frsena 275 Labyrinth, of ear 621 membranous 623 Lacerated foramen 68 Lachrymal apparatus 598 bone 80 caruncle 598 orifice 595, 599 papillae 595, 599 point 599 sac 599 Lachrymo-nasal duct 80, 91 Lacteals 438 Lamina, membranous spiral 626 osseous spiral 625 Laminae of the cerebellum 527 Larynx 440 aperture of 445 cartilages of 440 muscles of 444, 445 ventricles of 445 Layer, cellular, of membranes 259 fibrous, of membranes 262 Ligament, anterior annular. ... 138, 225 accessory of hip joint 159 annular, anterior, of the wrist.. 225 of the radius 145 of the ankle joint 241, 242 of the ear 616 of the stirrup 619 posterior, of the wrist 225 arcuate, external 218 astragalo-scaphoid ] 64 calcaneo-cuboid, inferior 165 capsular, between radius and ulna 145 of ankle joint 163 of astragalus and scaphoid bone 164 of calcaneum and cuboid bone 165 of elbow joint 144 of hip joint 159 of knee joint 161 of scapulo- clavicular ar- ticulation 142 of shoulder joint 143 of sterno-clavicular artic- ulation 141 of tempero- maxillary ar- ticulation 87 of wrist joint 146 coraco-acromial 143 coraco-clavicular 142 coraco-humeral 1 43 coracoid 130 costo-clavicular 142 costo-transverse, anterior 119 middle and posterior 119 costo-xiphoid 119 INDEX. 653 Ligament, cotyloid 159 dental 286 denticulat e 537 external calcaneo-scaphoid 165 lateral, of ankle joint 164 of the jaw 87 of elbow joint 145 of knee joint 162 of wrist joint 146 glenoid 143 great sacro-sciatic 126 ilio-lumbar 126 inferior calcaneo-cuboid 165 calcaneo-scaphoid 1G<5 inter-articular, of rib 118 inter-clavicular 142 internal lateral, of ankle joint.. 164 of elbow joint 145 of knee joint 162 of wrist joint 146 interosseous, of tarsal bones... 164 left lateral, of liver 302, 321 long plantar 166 nuchal Ill of the patella 161, 249 ovarian 485 palmar, of lingers 147 ptery go-maxillary 190 radiating 118 round, of hip joint 159 of ulna and radius 145 of uterus 484 right lateral, of liver 302, 321 small sacro-sciatic 126 spheno-m axillary 1 95 stylo-hyoid 64, 96 stylo-maxillary 194 superior calcaneo-cuboid 165 supra-spinous Ill sub-pubic 125 suspensory, of the anvil 619 of the clitoris 493 of the liver 302, 321 of the mallet 619 of the penis 476 of the spleen 302, 329 thyro-epiglottic 443 transverse 112 triangular 497 vertebral, anterior 109 posterior 110 Ligaments, acromio-clavicular 142 anterior of the bladder 463 arcuate 221 atlo-axoid, anterior 112 posterior 112 band-like 48 broad, of the uterus 304 capsular 48 of the costal cartilages 119 of the ribs 118, 119 costo-sternal 119 Ligaments, crucial 161 dorsal 147, 165 interosseous 147 of metatarsus 165 of tarsus 165 interspinous Ill intervertebral 107 lateral, of the bladder.... 463 lateral, of phalanges 147 occipito-atloid, anterior Ill posterior Ill odontoid 113 of the ear 013, 619 of the liver 301, 302, 321 of the metatarso-phalangial ar- ticulations 1 66 of the phalangial articulations.. 166 of the tibio-fibular articula- tions 163 of the uterus 484 of the urinary bladder 463 of the larynx 442 palmar ' 147 palpebral 596 sacro-iliac 126 sterno-clavicular 142 thyro-hy oid 442 vaginal, of fingers 226 of the toes 242 yellow 109 Linea aspera 148 alba 217 Line, median, of abdomen 217 semilunar, of abdomen 217 Lines, transverse, of abdomen 217 Lime, phosphate of 28 carbonate of 28 oxalate of 29 Lingual fraenum 280 Lips 274 of the uterus 482 Liquid, cerebro-spinal 539 Liquor sanguinis 340 Liver :JOO, 321 Lobes of a gland 270 of the cerebrum 515 of the liver 322, 323 of the lungs 451 of the prostate gland 480 Lobules of glands 270 of the liver 271, 325 of lungs, primary 452 secondary 452 Loins 211 Lower jaw bone 83 Lumbar regions 211, 299 vertebrae 103 Lungs 450 Lunula 641 Lymph 430 corpuscles 430 Lymphatic system 428 654 INDEX. Lymphatic glands 428, 429 anterior auricular 434 axillary 435 bronchial 436 coeliac 439 deep cervical 434 deep inguinal 437 external iliac 437 intercostal 436 internal iliac 437 internal maxillary 434 lumbar 438 mediastinal, anterior 436 posterior 436 mesenteric 438 mesocolic 438 occipital , 433 popliteal 437 posterior auricular 433 pulmonary 436 submaxillary .' 434 superficial cervical 434 inguinal 437 trunk, broncho-mediastinal 436 intestinal 439 vessels 428 anterior mediastinal 436 deep cervical 434 deep facial 434 intercostal 435 lingual 434 occipital 433 of the exterior of the tho- rax 435 of the large intestines 438 of the liver 438 of the lower extremities... 437 of the stomach 438 of the upper extremities... 435 pulmonary 436 superficial cervical 434 facial 434 temporal 433 MAGNESIA, phosphate of 28 Magnesium 21, 26 Malar bone 83 Malleolus, internal 152 external 153 Mallet 618 Malpighian corpuscles 460 Mammae 499 Mammillary eminences 518 Manganese.. 21 Margarin 27 Marrow 36, 39 Mastoid portion of temporal bone... 62 process 62 sinuses 62, 620 Matrix of nails 640 Maxillary bone, inferior 83 superior 76 Maxiliary sinus Meatus external auditory 63, inferior, of the nose internal auditory 63, middle, of the nose 57, superior, of the nose 57, Mediastinal cavities. . . ; Mediastinum of the testis Mediastinum Medulla 36, oblongat a Medullary cavity sheath substance of kidney of supra-renal bodies Melanin Membrane, arachnoid basement fenestrat ed mucous of the aqueous humor 603, of the tympanum perforated pupillary synovial 48, thyro-hy oid tympanic vocal Membranous labyrinth portion of urethra semicircular canals Mesentery 301, Mesocolon, ascending 301, descending 301 , transverse 301 , Mesorectum 301 , Metacarpal bones Metacarpus Metatarsal bones Metatarsus Milk globules plasma Mineral bodies Mitral valve Molars Mons veneris Motion, ciliary Mouth floor of the roof of the Mucus Mucous corpuscles membrane gastro-pulmonary genito-urinary mammary nasal Muscle, accessory flexor adductor, great v .. <6 34 615 94 627 93 93 454 470 454 39 530 30 505 459 466 27 539 334 266 610 616 334 608 263 265 442 616 443 623 479 623 303 303 303 303 304 138 138 156 156 502 502 502 18 347 288 491 261 278 275 267 267 266 266 266 266 593 256 250 Muscle adductor long INE 249 257 237 258 236 250 499 499 229 445 228 250 229 190 498 605 499 208 296 296 295 228 469 444 444 444 249 227 189 190 196 206 190 189 277 205 189 233 235 253 235 235 252 253 235 235 238 233 234 191 232 256 237 232 255 236 258 257 236 EX. 655 Muscle, flexor, snort, of the toes 256 superficial, of fingers 231 of the great toe gastrocnemius 254 of the little toe geminous 246 genio-glossal 284 short genio-hyoid 197 inal elevator gluteal, grea t 244 middle anconeous . ... small 245 gracilis 248 biceps flexor great serrated 202 biceps flexor of thigh pectoral 201 hyo-^lossal 284 - iliac 247 bulbo-urethral inferior oblique 209 ciliary 187 serrated . 206 coccygeal . infra-spinous complex internal pterygoid .. 191 constrictor of the pharynx, in- ferior interosseous of the foot., ischio-cavernous ... 258 . .. 498 middle .... labio-nasal depressor elevator 189 188 coraco brachial larger straight anterior . posterior 198 209 crico-arytenoid lateral larger zygomatic lateral straight latis^imus 189 209 204 posterior . crico-thyroid cruralis laxator 620 deltoid lingual 284 depressor of the lower lip long cervical 198 of the oral angle lumbrical 232, 256' 191 digastric masseter. . . dorsal extensor multifid spinal 208 197 elevator of the lower lip of the oral angle mylo-hyoid .. .. nasal compressor . 188 of the palate dilator... 188 of the scapular angle of the upper lip pyramidal . 186 oblique, external. 213 extensor, common, of the fin- gers inferior 602 internal metacarpal, of thumb of the great toe. superior .. . . 601 obturator, external internal 246 246 of the index finger of the little finger occipito-frontal 185 of the toes long omo-hyoid 196 oral orbicular 188 phalangial, of thumb, first, phalangial, of thumb, sec- palato-glossal 278 pharyngeal 295 palmar, long 230 radio-carpal, longer radio-carpal, shorter short palpebral elevator. 187 ulno-carpal orbicular 187 external pterygoid pectineal . . . 249 flexor deep of fingers. peroneal, anterior lonsr 252 ....... 253 long of great toe. . of little finger of the thumb . short plantar . of the toes. popliteal .. . 255 metacarpal, of thumb of the little toe posterior tibinl 256 psoas 247 short, of great toe of the thumb..., small 247 pyramidal ... .. 217 656 INDEX. Muscle, pyriform 246 quadrate femoral 246 lumbar 218 pronator 230 quadriceps extensor 249 radio-carpal flexor 230 rectus 249 rhomboid 205 sacro-lumbar 207 sartorius 248 scalene, anterior 197 middle 197 posterior 198 semi-membranous 251 semispinal 208 semi-tendinous 250 smaller straight, anterior 198 straight posterior 209 small pectoral 202 zygomatic 189 soleus 254 splenius 207 stapedius 620 sterno-costal 210 sterno-hyoid 195 sterno-mastoid..... 195 sterno-thyroid 196 straight, of abdomen 216 stylo-glossal 284 stylo-hyoid 196 stylo-pharyngeal 295 subclavian 202 subcutaneous cervical 193 subscapular 226 superciliary 187 superior oblique 209 serrated 205 supinator, long 233 short 235 supra-spinous 226 tarsal tensor 187 temporal 192 tensor of the ear 620 of the femoral fascia 248 of the palate 278 terete, greater 227 lesser 226 pronator 230 thyro-arytenoid 444 thyro-hyoid 196 tibial, anterior 252 trachelo-mastoid 208 transverse 215 of foot 258 transverse perineal 499 trapezius 203 triceps extensor 229 sural 254 ulno-carpal flexor 230 uvular 278 vaginal constrictor 498 vastus, external 249 Muscle, vastus, internal 249 Muscles 178 ciliary 605 costal elevator 210 form of 179 head of 179 insertion of. 179 intercostal 210 interosseous of the hand 237 inter-spinal 209 inter-transverse 209 of eyeball 601 of the larynx 443 origin of 179 pectinate 344 straight 601 Muscular fibres 178 striated 181 unstriated 271 fibrils 181 Myolemma 181 Myrtiform caruncles 490 NAILS 640 Nares 92, 184, 588 Nasal bone 81 cavities 92, 591 fossae 92 meatuses 93, 591 notch 77 orifices 92 partition 591 plate ,. 79 process 77 septum 92 spine 77 Nates 238 Navel 212 Navicular fossa 479 Neck 193 Nerve, auriculo-temporal 548 capsular bodies 510 cells 505 circumflex 568 crural 574 cutaneous, external 566 internal 566 small 566 deep auricular 552 dorsal of penis 578 clitoris 578 external cutaneous, of lumbar plexus 574 fibres 504, 508 frontal 544 genito-crural 573 great auricular 563 sciatic 578 ilio-hypogastric 573 ilio-inguinal 573 inferior dental 549 hsemorrhoidal 577 INDEX. 657 Nerve inferior maxillary ~>43 548 Nerves, fibres of.. . . 508 infra-orbital 552 ganglionic system of . 512 intercosto- humeral 572 glosso-pharyngeal 553 internal cutaneous of crural . 576 hypoglossal 559 lachrymal 544 inferior gluteal 578 lingual 548 infra-orbital 546 576 intercostal 571 median. . 568 lary ngeal 557 575 lumbar 572 musculo-cutaneous 579 oculo-motor 541 musculo-spiral 570 olfactory. 540 nasal 544 547 ophthalmic 543 obturator 574 optic 541 perineal 578 origin of 509 peroneal communicating 581 palatine 547 phrenic ... 563 pathetic 542 popliteal, external 579 phary ngeal .. 557, 583 internal 579 plantar 581 posterior interosseal 570 plexuses of 508 pterygoid... 547 pneumogastric 555 pudendal 578 pulmonary 557 pudic 577 real origin of 510 radial 570 sacral 576 short saphenous. 580 spheno-palatine 546 small occipital . 563 spinal 514 559 petrosal 550 subscapular ... 566 sciatic 578 superficial origin of. 510 splanchnic, great 585 supra-clavicular 563 small 585 termination of. . 509 third 585 thoracic 565 570 superficial cervical 563 vestibular 628 superior gluteal 577 Nervous system 503 maxillary 545 Neurilemma 60S temporal 552 Nipple 500 temporo-malar 546 Nitrogen 21 25 tibial anterior 579 Nose 588 posterior. 581 back of 184 trifacial 542 bridge of 184 tympanic.. 552, 554 cartilages of 590 591 ulnar 568 column of 184 zygomatic 552 meatuses of. 591 Nerves 503 root of 184 abdu cent 550 sinuses of 591 accessory 558 winf s of 591 apparent origin of. 510 Nostrils 184 auditory 553 Notch coracoid 130 cochlear branch of. 6?6 great sciatic 122 vestibular branch of. 6^,3 lesser sciatic 123 cardiac 557 nasal 77 inferior . ... 584 semilunar 85 middle 584 Nucleolus. . .. 23 superior 583 Nucleus 23 cerebral 514, 540 lenticular 523 cerebro-spinal 507, 514 Ny mphae 493 cervical 561 coccygeal 576 OBTURATOR FORAMEN 124 ciliary 544 membrane 125 cochlear . . 628 Occipital angle 52 deep origin of. 510 bone 50 dental 546 cross... 52 digital 581 protuberances 52 facial. . . 551 region... 91 658 INDEX. Odontoid ligaments 113 process 101 (Esophageal orifice 222 (Esophagus 297 Olecranon 135 Olein 27 Olfactory region 593 Olivary bodies 530 Omentum, gastro-colic 303 gastro-hepatic .'.... 301, 302 gastro-splenic 303, 329 great. 301, 303 Optic commissure 518, 541 tract 541 Orbital entrance 91 plate 77 Orbits 91 Organic cells 22 Organized bodies 18 Orifice, aortic 222 auriculo-ventricular 344 cesophageal 222 urethral 480 Orifices of the ureters 464 Origin of nerves 510 Osseous tissue 40 Ossification 42 centres of 42 Otolites 624 Oval foramen, of heart 344 sphenoid bone 56 Oval window 618 Ovarian ligament 485 Ovaries 485 Oviduct 488 Ovisacs 486 Ovum 486 Oxalate of lime 29 Oxygen 21, 25 PACINIAN CORPUSCLES 510 Palate 275 half arches of 276 bone 78 Palatine region 90 Palm 140, 223 Pancreas 300, 320 Pancreatic juice 321 Pancreatin 27, 326 Papillee of taste 282 tactile 630 Papillary muscles 345 Parietal bone . 60 Parotid gland 278 Paro varium 487 Partitions, intermuscular 182, 239 Patella 150 Pavilion 488 Pectinate muscles 344 Pectineal line 123 Pedicle, olfactory 540 Peduncles of cerebellum 528, 529 Peduncles of pineal gland 526 Pellucid septum 521 Pelvis 126 cavity of 494 of kidney 461 Penis * 475 Pepsin 27, 309 Pericardium 349 Perilymph 623 Perineum 496 Periosteum 39 Peritoneum 300 Permanent teeth 286 Petrous portion of temporal bone... 63 Peyer's glands 313 Phalanges of foot 157 of hand 139, 140 Phalanx 139 Pharynx 294 Phosphorus 21 Pia mater of brain 535 of spinal cord 536 Pimplemite 636 Pineal gland 526 Pit of the stomach 200, 212 Pituitary body.. 518 fossa 53 Plane of the ischium 124 Plate, nasal 79 of malar bone 83 orbital 57, 59, 77 palate 78, 79 Pleura 454 Plexus, aortic 586 brachial 563 cardiac 584 carotid 583 cavernous 583 cervical 562 choroid 523, 536 coronary 586 dorsi- spinal 423 ganglitorm 555 hsemorrhoidal , 319, 424 hepatic 586 hy pogastric 587 intra-spinal 423 lumbar 573 mesenteric, inferior 586 superior 586 cesophageal 558 pampiniform 473 pharyngeal 583 phrenic 586 prost atic 424 pulmonary 557 renal 586 reteform 471 sacral 577 solar 585 spermatic 586 splenic 586 INDEX. 659 Plexus, supra-renal 586 uterine 587 utero- vaginal 424 vesical 425 vesico-prostatic 587 vesico vaginal 587 Plexuses, nervous 508 venous 336 Pons 529 Popliteal region 238, 251 Potassa, carbonated 28 phosphate of 28 urate of 29 Potassium 26 chloride of. 28 Poupart's ligament 242 Premolars 287 Preperitoneal cavity 217 Prepuce of clitoris 493 of penis 475 Process, angular, external 58 internal 58 articular, of temporal bone.. .. 64 auditory 63 basilar 51 ciliary 605 clinoid, anterior 53 posterior 53 coracoicl 132 coronoiil 85, 135 falciform 243 frontal 83 lateral, of calcaneum 154 long, of the mallet 619 malar 78 inastoM 62 nasal 77 odontoid 101 of bone . 34 olivary 53 orbicular 619 orbital 80 pterygoid, external 55 internal 55 pyramidal 80 short, of the mallet 619 sphenoidal 80 spinous 34 of ilium, anterioi 122 posterior 122 superior 122 of radius 136 of sphenoid bone 55 of temporal bone 63 of the tibia 151 of vertebrae 98 styloid, of ulna 135 transverse, of occipital bone... 51 transverse, of vertebrie 98 turbinated, inferior 67 superior 57 vaginal 63 Process, vermiform 527 Promontory 617 of the pelvis 126 Prostate gland 480 Prostatic portion of urethra 478 Protuberance, occipital, external.... 52 internal 52 mental 84 zygomatic 62, 83 Ptyalin '. 27 Pubic symphysis 125 arch ...,. 127 Pubis 121, 123 Pulp of cavity 286 of teeth 286 of the spleen 330 Pulsation 350 Pulse 350 Pupil 607 Pulmonary circulation 350 Pyloric extremity of stomach 305 orifice 305 sphincter 306 valve 307 Pyramidal bodies 530 Pyramid of the tympanum 618 Pyramids, decussation of 531 posterior 531 renal 459 QUADRATE FORAMEN 223 RADIUS 135 Kami of pubis 123 Ramus of ischium 123 Raphe of perineum 496 of scrotum 468 of tongue 280 Receptacle of chyle 431 Rectum 318 Region, guttural 90 occipital 91 oral 90 palatine 90 Regions of the abdomen 299 Renal glomerule 460 papillae 459 pyramids 459 Restiform bodies 531 Reteform plexus 471 Retinn 608 Ribs 114 Ridge, asperous 148 inter-trochanteric 148 molar 84 of bone 34 superciliary 58 temporal 61, 88 Ring, external abdominal 213, 219 internal . 219 Root of lungs 450 of hairs ....>.-...> 636 660 INDEX. Rostrum 54 Rotation 48 Rotund foramen 5G Round window 618 SAC, LACHRYMAL 599 Saccule, spherical 623 elliptical 623 Sacrum 104 Saliva 280 Saphenous opening 240 Scala, tympanic 626 vestibular 626 Scalp 184 Scapula 130 Sclerotica 602 Sclerotic coat 602 Scrotum 468 Sebaceous glands 634 matter 635 Secondary tympanic membrane 618 Secretion 267 Semen 474 Semi-bulbs of the clitoris 493 Semicircular band 524 canals 622 membranous 623 Semilunar fibro-cartilages 160 folds 598 valves 346, 347 Seminal liquid 474, 472 vesicles 473 Seminiferous tubules 471, 472 Septal fibres 531 Septula of testicles 470 Septum, osseous nasal 92 pellucid 521 Serum 340 Sexual differences of the pelvis 128 Shaft of bone 34 Shin 151 Shin bone 150 Shoulder blade 130 Sigmoid flexure of the colon 315 Sinews 180 Sinus, anterior occipital 411 cavernous 411 circular 418 circular, of the iris 601 frontal 60 inferior longitudinal 410 petrosal 411 lateral 409 maxillary 76 of bone 34 posterior occipital 412 straight 410 superior longitudinal 410 petrosal 411 Sinuses, sphenoidal 54 ethmoidal 57 lactiferous 501 Sinuses, mastoid 62, 620 of dura mater 409, 538 venous 336 Soda, carbonate of 28 phosphate of. 28 taurocholate of 29 urate of 29 Sodium 21, 25 chloride of 28 Skeleton 33 Skin : 628 Skull 85, 87 Smegma 476 Soft epidermic layer 633 Soft palate 275 Solar plexus 585 Sole 157 Space, anterior, perforated 519 posterior " 518 Special anatomy 17 Sperm cells 472 Spermatic cones 471 cord 469 duct 471, 472 liquid. 472 Spermatozoids 474, 472 Sphenoid bone 52 Sphenoidal foramen 55 Spinal cord 513, 533 columns of 534 commissures of 533 fissures of. 533 gelatinoid substance of. 535 gray substance of 505 horns of 534 white substance of 504 Spine, nasal 77 of scapula 131 palate 79 Sphincter of the anus 319 of the bladder 464 Spinous foramen 56 Spiral lamina, osseous 625 membranous 626 tract 628 Spleen 329 Splenic corpuscles 330 Spongy body, of clitoris 493 of penis 477 portion of urethra 479 Squamous portion of temporal bone. 61 Sternum 117 Stirrup 619 Stomach 305 pit of 211 position of 299 Strait, inferior, of pelvis 127, 494 superior " 127,494 Striated body 523 Stroma of the ovary 485 Sub-arachnoid space 539 Sub-arachnoid tissue 264 INDEX. 661 Submaxillary gland... 279 Sub-mucous tissue 266 Sub-serous tissue 264 Substance of bone 36 Superciliary ridge 58 Supra renal bodies 465 Sutures 46, 66 dentated 46 of the cranium 66 of the face 86, 90 serrated 46 squamous 46 Sweat 634 duct 633 glands 633 Sylvian fissure 515 Sympathetic system of nerves 581 Syrnphysis 46 of inferior maxillary bone. 84 pubic 125 sacro-iliac 125 Synovia 49, 265 Synovial burssB 183, 265 fringes 49, 265 membranes 48, 265 Systemic circulation 351 TACTILE CORPUSCLES 511, 630 papillae 630 Tapetum 607 Tarsal bones 153 Tarsus 153 Teeth 285 bicuspid 287 canine 287 eruption of 293 eye 287 front 286 jaw 288 milk 288 permanent 285, 286 stomach 287 temporary 285, 288 Temple 183 Temporal bone 61 fossa 88 regions 183 Tendinous cords 346 Tendon of Achilles 254 Tendons 178,180, 182 Tentorium 538 Testicles 468 Thalami 524 Thalamus 524 Thoracic aorta 381 duct 431 Thorax 119 Throat 193, 294 Thymus body.. 456 Thyroid body 455 cartilage 440 Tibia... . 150 Tissue, adipose 176 areolar 170 connective 170 elastic 175 fat 176 fibrous 167 sub-archnoH 264 sub-serous 264 Toes 157 Tongue 280 Tonsils 276 Tonsils of the cerebellum 528 Topographical anatomy 17 Trabeculse of penis 476 of spleen , 330 Trachea 447 Tract, spiral 628 Tricuspid valve 345 Trochanters 148 Trunk of skeleton 96 Tubercle 34 mental 84 Tuberosity 34 Tunics of the eye 600 Turbinated bone 81 Tympanic membrane 616 secondary 618 Tympanum 616 ULNA 134 Umbilical region 299 Umbilicus 212 Urachus 463 Urea 29, 462 Ureter 461 Ureters 458 Urethra 465, 478 Urinary bladder 462 Urine 462 Uriniferous tubules 460 Uroerythrin 29 Uterus 481 Utricle 474 Uvula 275 of the cerebellum 528 vesicle 464 VAGINA 489 Valley 527 Valve, ileo-colic 316 mitral 347 of the brain.... 529 pyloric 307 tricuspid 345 Valves of veins 336 semilunar 346, 347 Valvulse conniventes 266, 310 Vasdeferens 472 Vein, angular 414 axillary 417 azygos 419 basilic .. 418 662 INDEX. Vein, cardiac anterior 406 Veins cerebellar superior 41 posterior . 406 cerebral inferior 412 cephalic 418 internal 412 coronary 405, 422 median 41'> cystic 422 superior. '11 *> dorsal lingual 416 common iliac 493 of clitoris 425 companion 335 of penis 425 diploic 41o 493 facial 414 dorsi-spinal plexus of dS femoral 426 hsemorrhoidal plexus of I'M frontal 414 hemi-azygos 419 iliac external 425 hepatic 421 internal 424 inferior palpebral 414 innominate, left 406 innominate 406 right 406 intercostal left 4*>0 internal maxillary 415 right . . . 419 jugular, anterior 413 internal mammarv. 407 external 413 intra-spinal plexus of 12'-? internal 408 409 jugular 108 posterior. 413 labial 114 mastoid 416 longitudinal anterior 4'>3 median basilic 419 posterior 4^3 cephalic 419 lumbar 491 mesenteric, inferior.... 422 masseteric .... 414 superior 422 median 1 1 9 middle sacral 420 meningeal 113 occipital . 416 nasal 41 4 ophthalmic 413 O3sopha u 'eal 419 palatine 414 ovarian .. vn pharyno"vl vertebral . 407 of the heart 343 Veins . ... ... 335, 405 of the larynx 445 articular. 415 Vermiform appendix 315 auricular anterior 415 process 5?,7 brachial 417 Vertebrae 97 453 cervical 99 414 dorsal 10?, 406 false . ... 103 cerebellar, inferior.... .. 412 lumbar 103 INDEX. 663 Vertebras, true 97 Vertebral column 1)7, 113 Vertex 184 Vesical sphincter 464 triangle 464 uvula 464 Vesicles, seminal 473 Vesico-uterine pouches o04 folds 304 Vessels afferent 429 efferent 429 lymphatic 428 Vestibule 494 of the ear 621 of the labyrinth 621 Villi 311 Vitelline membrane 487 Vitreous humor 611 table of bone 65 Vocal cords 443, 446 false 447 membrane... .. 443 Vomer 82 Vulva 491 WHITE SUBSTANCE 505 of the eye 598, 602 Windpipe 447 Window, oval 618 round 618 Wings of the sphenoid bone 54 ethmoidal 56 Womb 481 Wrist 136 joint 146 YELK 487 Yellow ligaments 109 spot 609 ZONE, ciliary 612 Zygoma 62 Zygomatic arch 88, 89 14 DAY USE RETURN TO DESK FROM WHICH BORROWED JBiyLw'iiu , ^j * , This book is oue on the last date stamped below, or on the date to which renewed. Renewed books are subject to immediate recall. LD 21-50m-6,'59 (A2845slO)476 General Library University of California Berkeley