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Jfg~ They are arranged in the most approved form, thorough and concise, containing over 300 illustrations, inserted wherever they could be used to advantage. fl-^'Can be used by students of any college. Jtif- They contain information nowhere else collected in such a condensed, practical shape. SPECIAL NOTICE. These Compends may be obtained through any Bookseller, Wholesale Druggist or Dental Depot, or upon receipt of the price, will be sent, postpaid, by the publishers. In ordering, always specify " Blakiston's ? Quiz-Compends ?". No. i. HUMAN ANATOMY. Based on "Gray." Fifth Revised and Enlarged Edition. Including Visceral Anatomy, formerly published separately. 117 Illustrations and 16 Lithographic Places of Nerves and Arteries, with Explanatory Tables, etc. By SAMUEL O. L. POTTER, M.D., Professor of the Practice of Medicine, Cooper Medical College, San Francisco; late A. A. Surgeon, U. S. Army. No. a. PRACTICE OF MEDICINE Part I. Fourth Edition. Revised, Enlarged and Improved. 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PHARMACY. Third Edition. Based upon Prof. Remington's Text-book of , . , No. 12. VETERINARY ANATOMY AND PHYSIOLOGY. Illustrated. By WM. R. BALLOU, M.D., Professor of Equine Anatomy at New York College of Veterinary Surgeons : Physician to Bellevue Dispensary, and Lecturer on Genito-Urinary Surgery at the New York Polyclinic, etc. With 29 graphic Illustrations. Just Ready. No. 13. WARREN. DENTAL PATHOLOGY AND DENTAL MEDICINE, containing all the most noteworthy points of interest to the Dental Student. By GEO. W. WARREN, D.D s.. Clinical Chief Pennsylvania College of Dental Surgery, Phila. No. 14. DISEASES OF CHILDREN. By MARCUS P. HATFIELD, Professor of Dis- eases of Children, Chicago Medical College. Just Ready. Price, each, Cloth, $1.00. Interleaved, for taking Notes, $1.25. P. BLAKISTON, SON & CO. 1012 Walnut St., Philadelphia. MANUAL OF THE DISSECTION OF THE HUMAN BODY LUTHER HOLDEN LATE PRESIDENT OP THE ROYAL COLLEGE OP SURGEONS OP ENGLAND CONSULTING SURGEON TO ST. BARTHOLOMEW'S AND FOUNDLING HOSPITALS FIFTH EDITION EDITED BY JOHN LANGTON SURGEON TO, AND LECTURER ON ANATOMY AT, ST. BARTHOLOMEW'S HOSPITAL MEMBER OF THE BOARD OF EXAMINERS, ROYAL COLLEGE OF SURGEONS OF ENGLAND SURGEON TO THE CITY OF LONDON TRUSS SOCIETY CONSULTING SURGEON TO THE CITY OF LONDON LYING-IN HOSPITAL AND TO THE MEMORIAL HOSPITAL AT MILDMAY PARK PHILADELPHIA : P. BLAKISTON, SON & CO., 1012 WALNUT STREET. TO THE STUDENTS OF ST BABTHOLOMEW'S HOSPITAL IN THE HOPE THAT IT MAY ASSIST THEM IN THEIR ANATOMICAL STUDIES h grifoaUfc \ BY THBIE FAITHFUL FRIEND AND WELL-WISHER THE AUTHOR >- PREFACE THE FIFTH EDITION. IN THIS EDITION the Editor has most carefully revised the entire work. The order of dissection has been here and there altered, and further illustrations and additional matter introduced, especi- ally concerning the Anatomy of the Nervous System and the Organs of Special Sense. The object throughout has been to be as concise as possible, and to put the subject in as clear and practical a light as is com- patible with the faithful handling of its natural difficulties. It is hoped that the work, in its present form, is adapted, not only for students, but for members of the profession who wish to refresh their anatomical knowledge. The best thanks of the Editor are due to the Demonstrators and Assistant Demonstrators of Anatomy at St. Bartholomew's Hospital for valuable suggestions. 2 HARLEY STREET, CAVENDISH SQUARE : September 1884. X PEEFACE TO THE FIRST EDITION. The several regions of the body are treated of in the order considered most suitable for their examination ; and the muscles, vessels, nerves, &c. are described, as they are successively exposed to view in the process of dissection. The Author has written the work entirely from actual observa- tion : at the same time no available sources of information have been neglected, the highest authorities both English and Foreign having been carefully consulted. His acknowledgments are especially due to F. C. SKEY, Esq. F.R.S., Lecturer on Anatomy at St. Bartholomew's Hospital, for many valuable suggestions. He is also much indebted to his young friend, Mr. W. CLUBBE, for able assistance in dissections. September 1851. CONTENTS. PAKE DISSECTION OF THE SCALP . . . . . 1 DISSECTION OF THE FACE . . . . . .24 DISSECTION OF THE ORBIT . . . . . 49 DISSECTION OF THE NECK . . . . . .63 COURSE AND EELATIONS OF THE SUBCLAVIAN ARTERIES . . 113 THE MUSCLES OF MASTICATION. TEMPORAL AND PTERYGO-MAXILLARY EEGIONS . . . . . . . . 127 BRANCHES OF THE INTERNAL MAXILLARY ARTERY IN THE THREE STAGES OF ITS COURSE ........ 134 BRANCHES OF THE INFERIOR MAXILLARY NERVE . . . 138 DISSECTION OF THE THORAX . *. - . . . 155 DISSECTION OF THE HEART ...... 198 FOZTAL CIRCULATION . . . . '. . . 213 STRUCTURE OF THE LUNGS ' . . . . . . 216 DISSECTION OF THE PHARYNX . . . . . . 224 DISSECTION OF THE LARYNX ...... 238 DISSECTION OF THE TONGUE . . . . . . 253 DISSECTION OF THE SUPERIOR MAXILLARY NERVE . . . 258 DISSECTION OF THE NINTH, TENTH, AND ELEVENTH CRANIAL NERVES AT THE BASE OF THE SKULL . . . . . . 265 DISSECTION OF THE NOSE ...... 271 DISSECTION OF THE MUSCLES OF THE BACK . . . 278 LIGAMENTS OF THE SPINE ...... 295 DISSECTION OF THE UPPER EXTREMITY . . . . 305 DISSECTION OF THE AXILLA 312 Xll CONTENTS. PAGE DISSECTION OF THE UPPEK ARM . . . . . 324 DISSECTION OF THE FRONT OF THE FOREARM .... 839 DISSECTION OF THE PALM OF THE HAND . . . . 353 MUSCLES OF THE BACK CONNECTED WITH THE ARM . . . 366 DISSECTION OF THE MUSCLES OF THE SHOULDER . . . 378 DISSECTION OF THE BACK OF THE FOREARM ..... 387 DISSECTION OF THE LIGAMENTS . . . . . 401 DISSECTION OF THE ABDOMEN ...... 419 DISSECTION OF THE PARTS CONCERNED IN INGUINAL HERNIA . . 440 DISSECTION OF THE PELVIC VISCERA ..... 499 DISSECTION OF THE MALE PERINEUM . . . . 505 DISSECTION OF THE FEMALE PERINEUM ..... 521 ANATOMY OF THE SIDE VIEW OF THE PELVIC VISCERA . . . 525 STRUCTURE OF THE BLADDER, PROSTATE, URETHRA, AND PENIS . 547 DISSECTION OF THE FEMALE PELVIC VISCERA . . . 562 DISSECTION OF THE ABDOMINAL VISCERA .... 575 DISSECTION OF THE LOWER EXTREMITY . . . . 609 ANATOMY OF THE PARTS CONCERNED IN FEMORAL HERNIA . . 619 DISSECTION OF THE FRONT OF THE LEG . . . . 643 DISSECTION OF THE GLUTEAL EEGION . . . . . 653 DISSECTION OF THE BACK OF THE THIGH . . . . 668 DISSECTION OF THE BACK OF THE LEG ..... 672 DISSECTION OF THE SOLE OF THE FOOT . . . . . 683 DISSECTION OF THE LIGAMENTS . . ,..'. . . 693 DISSECTION OF THE BRAIN . . . . . . . 715 DISSECTION OF THE SPINAL CORD ..... 780 DISSECTION OF THE EYE . . . . . . 793 DISSECTION OF THE ORGAN OF HEARING .... 816 DISSECTION OF THE MAMMARY GLAND . . . . 836 DISSECTION OF THE SCROTUM AND TESTIS .... 838 INDEX , 849 LIST OF ILLUSTBATIONS. 1. Muscular and Aponeurotic Stratum of the Scalp . . .2 2. Sensory Nerves of the Scalp and Face . . . . . 5 3. Branches of the Facial Nerve . . . . . .7 4. Diagram to show the Formation of a Sinus . . . 11 5. The Cranial Sinuses . . . . . . .11 6. The Venous Sinuses at the Base of the Skull . . . 15 7. The Exit of the Cranial Nerves . . . . .18 8. The Nerves in the Foramen Jugulare . . . . . 20 9. Relation of Structures in the Cavernous Sinus . . .21 10. Eelations of the Nerves in the Sphenoidal Fissure . . 22 11. Eelations of the Nerves and Muscles in the Orbit . . .22 12. The Geniculate Ganglion of the Facial Nerve . . . . 28 13. The Muscles of the Face . . . . . .26 14. The Lachrymal Apparatus . . . ... 83 15. The Muscles of the Pharynx . . . ' . . . .37 16. The Branches of the External Carotid Artery . . . 39 17. The Branches of the Facial Nerve . . . . .46 18. The Sensory Nerves of the Scalp and Face . . . . 48 19. The Nerves of the Orhit . . . . . .50 20. View of the Orbit from above . . . . . . 52 21. Lachrymal Duct . . . . . . .54 22. View of the Optic and Lower Nerves of the Orbit . . . 57 23. Insertion of the Eecti Muscles . . .62 24. The Superficial Nerves and Veins of the Neck . . . . 66 Xll CONTENTS. PAGE DISSECTION OF THE UPPER ARM . . . . . 324 DISSECTION OF THE FRONT OF THE FOREARM .... 339 DISSECTION OF THE PALM OF THE HAND . . . . . 353 MUSCLES OF THE BACK CONNECTED WITH THE ARM . . . 366 DISSECTION OF THE MUSCLES OF THE SHOULDER . . . 378 DISSECTION OF THE BACK OF THE FOREARM ..... 387 DISSECTION OF THE LIGAMENTS . . . . . 401 DISSECTION OF THE ABDOMEN ...... 419 DISSECTION OF THE PARTS CONCERNED IN INGUINAL HERNIA . . 440 DISSECTION OF THE PELVIC VISCERA ..... 499 DISSECTION OF THE MALE PERINEUM . . . . 505 DISSECTION OF THE FEMALE PERINEUM ..... 521 ANATOMY OF THE SIDE VIEW OF THE PELVIC VISCERA . . . 525 STRUCTURE OF THE BLADDER, PROSTATE, URETHRA, AND PENIS . 547 DISSECTION OF THE FEMALE PELVIC VISCERA . . . 562 DISSECTION OF THE ABDOMINAL VISCERA .... 575 DISSECTION OF THE LOWER EXTREMITY . . . . 609 ANATOMY OF THE PARTS CONCERNED IN FEMORAL HERNIA . . 619 DISSECTION OF THE FRONT OF THE LEG . . . . 643 DISSECTION OF THE GLUTEAL EEGION ..... 653 DISSECTION OF THE BACK OF THE THIGH . . . . 668 DISSECTION OF THE BACK OF THE LEG ..... 672 DISSECTION OF THE SOLE OF THE FOOT . . . . . 683 DISSECTION OF THE LIGAMENTS . . . . . . 693 DISSECTION OF THE BRAIN . . . . . . . 715 DISSECTION OF THE SPINAL CORD ..... 780 DISSECTION OF THE EYE . . . . . . 793 DISSECTION OF THE ORGAN OF HEARING .... 816 DISSECTION OF THE MAMMARY GLAND . . . . 836 DISSECTION OF THE SCROTUM AND TESTIS .... 838 V INDEX , 849 LIST OF IKLUSTKATIONS. FIG. PAGE 1. Muscular and Aponeurotic Stratum of the Scalp . . .2 2. Sensory Nerves of the Scalp and Face . . . 5 3. Branches of the Facial Nerve . . . . . .7 4. Diagram to show the Formation of a Sinus . . . 11 5. The Cranial Sinuses . . . . . . .11 6. The Venous Sinuses at the Base of the Skull . . . 15 7. The Exit of the Cranial Nerves . . . . .18 8. The Nerves in the Foramen Jugulare . . . . . 20 9. Relation of Structures in the Cavernous Sinus . . .21 10. Relations of the Nerves in the Sphenoidal Fissure . . 22 11. Relations of the Nerves and Muscles in the Orbit . . .22 12. The Geniculate Ganglion of the Facial Nerve . . . . 23 13. The Muscles of the Face . . . . . .26 14. The Lachrymal Apparatus . . . ... 33 15. The Muscles of the Pharynx . . . ' . . . .37 16. The Branches of the External Carotid Artery . . . 39 17. The Branches of the Facial Nerve . . . . .46 18. The Sensory Nerves of the Scalp and Face . . . . 48 19. The Nerves of the Orbit . . . . . .50 20. View of the Orbit from above . . . . . . 52 21. Lachrymal Duct . . . . . . .54 22. View of the Optic and Lower Nerves of the Orbit . . . 57 23. Insertion of the Recti Muscles . . . . .62 24. The Superficial Nerves and Veins of the Neck . . . . 66 xiv LIST OF ILLUSTRATIONS. F[G. PAGE 25. The Triangles of the Neck . . . . 73 26. Central Line of the Neck ...... 78 27. Digastric Triangle and Contents . . . . 92 28. The Branches of the External Carotid Artery and their Branches . 97 29. Muscles, Vessels, and Nerves of the Tongue . . . . 102 30. The Heart and Large Vessels ..... 114 31. The Inosculations of the Subclavian Artery . . . 122 32. The Formation of the Brachial Plexus and its Branches . . 125 33. Pterygoid Muscles and the Internal Maxillary Artery . . . 132 34. Plan of the Internal Maxillary Artery .... 135 35. Plan of the Branches of the Inferior Maxillary Nerve . . . 139 36. The Communications of the Facial, Glosso-pharyngeal, Pneumo- gastric, Spinal Accessory, Hypoglossal, Sympathetic, and the two Upper Cervical Nerves ...... 152 37. Form and Position of the Lungs . . . . . 156 38. The Reflections of the Pleural Sacs ..... 161 39. The Heart, showing Interpleural Space . . . . 163 40. Form and Position of the Lungs ..... 164 41. Eelative Position of the Heart and its Valves with regard to the Walls of the Chest . . . . . . . 168 42. Superior Vena Cava and its Tributaries . . . 173 43. Course and Eelations of the Arch of the Aorta . . . 175 44. The Course of the Vena Azygos and the Thoracic Duct . . 183 45. The Thoracic Portion of the Sympathetic Nerve . . . 189 46. Diagram of a Spinal Nerve ...... 192 47. The Constituents of the Boot of each Lung and their relative position 197 48. The Interior of the Bight Auricle . . . . 201 49. The relative Position of the Valves of the Heart seen from above . 209 50. Scheme of the Festal Circulation . . . . . 214 51. Ultimate Air-cells of the Lung ..... 222 52. Side view of the Muscles of the Pharynx . . . 227 53. View of the Constrictor Muscles from behind . . . 229 54. View of the Pharynx laid open from behind . . . 231 55. Shape of the Glottis when at rest ..... 246 56. Diagram showing the Action of the Crico-thyroid Muscle . . 247 LIST OF ILLUSTRATIONS. XV FIG. PAGE. 57. Glottis dilated : Muscles dilating it . . . . . 248 58. Side view of the Muscles of the Larynx . . . . . 249 59. Glottis closed : Muscles closing it . . . . 250 60. Upper Surface of the Tongue, with the Fauces and Tonsils . , . 254 61. Diagram of the Superior Maxillary Nerve . 259 62. Deep view of the Spheno -palatine Ganglion . . . 261 63. Communications of the Facial, Glosso-pharyngeal, Pneumogastric, Spinal Accessory, Hypoglossal, Sympathetic, and the two Upper Cervical Nerves ....... 264 64. The Geniculate Ganglion of the Facial Nerve and its Communica- tions . . . . . . . . 268 65. Cartilages of the Nose . . . . . .272 66. Transverse Section through the Abdomen to show the attachment of the Lumbar Fascia . . . . . . 279 67. The Superficial Muscles of the Back . . . . .280 68. The Suboccipital Triangle . . . . . 288 69. The Cutaneous Nerves of the Back ..... 292 70. The Prevertebral Muscles . . . . ... 71. The Odontoid and Transverse Ligaments .... 72. Costo-vertebral Ligaments . . . . . 73. The Ligaments connecting the Eib with the Vertebra 74. Transverse Section to show the Ligaments and the Fibro-Cartilage of the Lower Jaw . . . . . . . 304 75. The Axilla ........ 316 76. Plan of the Branches of the Axillary Artery . . . 317 77. The Origins of the Triceps . . . . . .318 78. The Brachial Plexus of Nerves . . . . . 320 79. Distribution of the Cutaneous Nerves to the front of the Shoulder and Arm ........ 325 80. Superficial Veins and Nerves at the bend of the Left Elbow . . 326 81. Plan of the Chief Branches of the Brachial Artery . . . 334 82. The Muscles of the Front of the Forearm . . . . 343 83. The Superficial and Deep Palmar Arches . . . 356 84. Cutaneous Nerves of the Back . . . . . 369 85. The Superficial Muscles of the Back . . . . .371 Xvi LIST OF ILLUSTRATIONS. FIG. PAGE 86. Cutaneous Nerves of the Left Shoulder and Arm (posterior view) . 378 87. Analysis of the Deltoid . . . . . .380 88. The Arteries of the Scapula . . . . . 384 89. The Anastomoses of the Arteries at the back of the Elbow and Wrist Joints . . . . . . . .396 90. The Dorsal Interossei . . . . . . . 399 91. The Palmar Interossei, and the Adductor Pollicis . . . 399 92. The Sterno- clavicular Ligaments . . . . . 402 93. Anterior view of the Scapulo-clavicular Ligaments, and of the Shoulder-joint ....... 404 94. Ligaments of the Elbow-joint . . . . . 408 95. The Ligaments and Synovial Membranes of the Wrist-joint . 412 96. The Abdominal Eegions . . . . . . 420 97. Superficial Vessels and Glands of the Groin . . . 422 98. Poupart's Ligament, and the External Abdominal Ring . . 426 99. The Lower Fibres of the Internal Oblique and Transversalis, with the Cremaster Muscle ...... 428 100. Transverse Section to show the Formation of the Sheaths of the Eectus, the Quadratus Lumborum, and the Erector Spinae . . 431 101. The Fascia Transversalis seen from the front . . . 435 102. Varieties of Congenital Inguinal Herniae . . . . 444 103. Section to show the Ileo-caecal Valve and Appendix Vermiformis . 451 104. Relative Position of the Kidneys and the Large Intestine, seen from behind . . . . . . . . 452 105. The Peritoneum ....... 459 106. A Transverse Section through the Upper Part of the Abdominal Cavity . . . . . . . . 461 107. A Transverse Section through the Lower Part of the Abdominal Cavity ........ 461 108. Branches of the Abdominal Aorta . . . . 465 109. The Branches of the Coeliac Axis ..... 467 110. The Vena Portse . . . . . . . 470 111. Plan of the Mesenteric Arteries, and their Communications . 471 112. The Diaphragm . . . . . . . 478 113. The Diaphragm from its Upper Surface .... 479 LIST OF ILLUSTRATIONS. FIG. PAGE 114. The Course and Kelations of the Abdominal Aorta and Vena Cava Inferior. ........ 483 115. Plan of the Lumbar Plexus and Branches .... 497 116. The Relative Position of the Pelvic Viscera . . . . 502 117. Vertical Section through the Female Pelvic Viscera . . 504 118. Framework of the Perineum . . . . . 505 119. Muscles, with Superficial Vessels and Nerves, of the Perineum . 510 120. The Accelerator Urinae in profile . . . . 512 121. The Triangular Ligament of the Urethra .... 513 122. The Parts behind the Anterior Layer of the Triangular Ligament . 514 123. The Relations of the Compressor Urethras .... 518 124. Bulb of the Vagina . . . . . . . 524 125. Vertical Section through the Perineum and Pelvic Viscera . 526 126. Transverse Section to show the Reflections of the Pelvic Fascia . 527 127. Side View of the Pelvic Viscera . . . . .530 128. Posterior View of the Bladder . . . . . 533 129. Plan of the Branches of the Internal Iliac Artery . . . 539 130. View of the Abnormalities of the Obturator Artery . . . 541 131. Plan of the Sacral Plexus and Branches .... 545 132. Bladder and Urethra exposed from the Upper Surface . . 549 133. Transverse Sections of the Urethra ..... 556 134. Transverse Section through the Penis . . . . . 560 135. The Uterus, the Ovaries, and Fallopian Tubes . . . 571 136. The Under Surface of the Liver . . . . . 5177 137. Transverse Sections of Lobules of the Liver . 579 138. Longitudinal Sections of Lobules of the Liver . . . 580 139. Section of the Kidney . . . . . .590 140. The Course and Arrangement of the Uriniferous Tubes . . 592 141. A Tubulus Uriniferus . . . . . .594 142. Section to show the Ileo-caecal Valve . ... 605 143. Saphenous Opening with the Cribriform Fascia . . . 612 144. Fascia on the Outside of the Thigh . . . . 616 145. The Femoral Ring and the Saphenous Opening . . 617 146. Position of Parts under the Crural Arch 621 a XV111 LIST OF ILLUSTRATIONS. FIG. PAGE 147. The Sheath of the Femoral Vessels . . . . .622 148. View of the Abnormalities of the Obturator Artery . . . 625 149. Scarpa's Triangle . . . . . . .628 150. Section through Hunter's Canal . . . . . 637 151. Plan of the Inosculations of the Circumflex Arteries . . 640 152. Plan of the Sacral Plexus and Branches . . . 660 153. Deep Muscles of the Gluteal Region .... 661 154. The Arteries of the Gluteal Region . . . . 663 155. Left Popliteal Space . . . . . . .666 156. Diagram showing Action of the Hamstring Muscles . . . 671 157. Diagram showing Action of the Gastrocnemius . . . 676 158. Muscles, Vessels, and Nerves of the Sole of the Right Foot . . 686 159. Plantar Arteries ... . . . . .688 160. View of the Third Layer of the Muscles of the Foot . . . 691 161. The Sacro-sciatic Ligaments ...... 695 162. Vertical Section through the Hip . . . . 698 163. The Semilunar Cartilages and Lateral Ligaments of the Knee . 702 164. Crucial Ligaments of the Knee . . . . . 706 165. Ligaments of Ankle-joint ...... 708 166. The External Lateral Ligament . . . . 708 167. Calcaneo-cuboid Articulation ..... 711 168. Interosseous Ligaments of the Cuneiform Bones . . 712 169. The Articulations of the Tarsus and the Tar so -metatarsus . . 713 170. The Base of the Brain . . . . . . . 718 171. The Front Surface of the Medulla Oblongata . . .723 172. The Fourth Ventricle and the Restiform Bodies . . . 725 173. The Course of the Fibres through the Medulla Oblongata . . 728 174. The General Division of the Brain . . . . 733 175. Convolutions and Fissures of the External Surface of the Brain . 735 176. Convolutions of the Upper Surface of the Brain . . . 736 177. Convolutions of the Base of the Cerebrum .... 739 178. Convolutions and Fissures of the Median Surface of Right Hemi- sphere . . . . . . . . 741 179. Diagram of the Course of the Fibres through the Medulla and Pons 746 LIST OF ILLUSTRATIONS. xix FIG. PAGB 180. The Origins of the Olfactory and Optic Nerves . . . 747 181. The Floor of the Fourth Ventricle . . . . 751 182. Upper Surface of the Corpus Callosum .... 754 183. Diagram of the Lamina Cinerea . . . . 754 184. Vertical Section through the Corpus Callosum, and parts below . 755 185. The Lateral Ventricles . . . . . . . 757 186. Transverse Vertical Section through the Brain . . . 758 187. The Fornix . . . . . . . . 760 188. The Lateral Ventricles and the Velum Interpositum . . 763 189. The Cerebellum . . . . . . . . 768 190. Floor of the Fourth Ventricle . . . . .772 191. Superior Surface of the Cerebellum . . . . . 775 192. Inferior Surface of the Cerebellum . . . . . 777 193. The Spinal Veins (vertical section) . . . . 781 194. The Spinal Veins (transverse section) .... 782 195. The Ligamentum Denticulatum . . . . 785 196. A Transverse Section through the Spinal Cord and its Membranes 787 197. Insertion of the Eecti Muscles . . . . . . 796 198. A Vertical Section of the Eye . . . . .797 199. The Choroid, the Ciliary Muscle, and Nerves . . . . 801 200. The Various Layers of the Ketina ..... 808 201. Arteries of the Eetina . . . . . . 813 202. The Ossicles of the Eight Tympanum . . . .822 203. Osseous Labyrinth of the Eight Side . . . . _ . 825 204. The Osseous Cochlea . . . . . .827 205. Section of a Coil of the Cochlea . . . . . 829 206. Vertical Section of the First Turn of the Cochlea . . .831 207. A Vertical Section through the Testicle . ... 840 208. Transverse Section through the Left Testicle . . . 842 A MANUAL OF THE DISSECTION OF THE HUMAN BODY. DISSECTION OF THE SCALP. AN INCISION should be made from the root of the nose along the mesial line of the vertex to the external protuberance of the occipital bone ; another, horizontally round each half of the head, to join at right angles the two ends of the first incision. These incisions must not divide more than the skin, so that the subcutaneous vessels and nerves be not injured. It is well to dissect on one side of the head the muscles only, re- serving the other side for the dissection of the vessels and nerves. STRATA COMPOS- The several strata of tissues covering the skull- ING THE SCALP. cap are 1, the skin ; 2, a thin layer of connective tissue and fat which contains the cutaneous vessels and nerves and the bulbs of the hair ; and by which the skin is very closely, con- nected to, 3, the broad thin aponeurosis of the occipito-frontalis muscle (aponeurosis of the scalp) ; 4, an abundance of loose connec- tive tissue, which permits the free motion of the scalp upon, 5, the pericranium, or periosteum of the skull-cap. Immediately beneath the skin, then, we expose the thin stratum of connective and adipose tissue which firmly connects it with the aponeurosis of the scalp. This layer is continuous behind with the superficial fascia covering the muscles at the back of the neck, and laterally it passes over the temporal fascia. It forms a bed for the bulbs of the hair and for the ramifications of the cutaneous arteries. B 2 DISSECTION OF THE SCALP. The toughness of this tissue, in which the arteries ramify, does not permit them to retract when divided ; hence the haemorrhage which follows incised wounds of the scalp ; hence, also, the difficulty of drawing them out with the forceps. OCCIPITO-FBON- This cutaneous muscle is closely connected to TALIS MUSCLE AND the scalp. It consists of two fleshy portions, one EPICBANIAL O n the occiput, the other on the forehead, con- APONEUBOSIS. nected by a broad aponeurosis. The occipital portion of the muscle is thin, and takes origin from the outer two- FIG. l. DIAGBAM SHOWING THE MUSCULAR AND APONEUBOTIC STBATUM OF THE SCALP. A. Attollens aurem. c. Retrahens aurem. B. Attrahens aurem. D. Orbicularis palpebrarum. thirds of the upper curved line of the occipital bone, and the adjoining part of the mastoid process of the temporal bone. The fibres ascend over the back of the head for about two inches, and then terminate in the epicranial aponeurosis. The frontal portion, commencing in an arched form from the epicranial aponeurosis below the coronal suture, descends over the forehead, and termi- MUSCLES OF THE PINNA. 3 nates partly in the skin of the brow, partly in the orbicularis oculi and corrugator supercilii, while some of the inner fibres are con- tinuous in front of the nose with the pyramidalis nasi muscle. The aponeurosis of the scalp covers the vertex of the skull, the two being continuous across the middle line. It is continued over the temples and side of the head, gradually changing from tendinous into connective tissue. This muscle enables us to move the scalp backwards and forwards. But its chief action is as a muscle of expression. It elevates the brows, and occasions the transverse wrinkles in the expression of surprise. The occipital portion is supplied by the posterior auricular branch of the facial ; the frontal portion by the temporal branch of the same nerve. MUSCLES OP THE There are several small muscles to move the EAE. cartilage of the ear. In man they are thin and pale, and require care to dissect them out satisfactorily. In animals who possess a more delicate sense of hearing, they are much more developed, for the purpose of quickly directing the cartilage of the ear towards the direction of the sound. ATTOLLENS To indicate the position of this muscle the AUKEM. student should draw down the upper part of the pinna of the ear, when it will be found immediately under the ridge of skin so produced. It is a thin fan-shaped muscle and arises from the epicranial aponeurosis, and is inserted into the cranial aspect of the upper part of the concha. ATTRAHENS This muscle is the smallest of these muscles, AUKEM. and its situation is indicated by the prominence of skin produced by drawing backwards the front part of the helix. It arises from the aponeurosis of the occipito-frontalis, and is inserted into the front of the helix. BETRAHENS This muscle is exposed by reflecting the skin AUKEM. from the ridge produced by drawing the pinna forwards. Consisting of two or three fasciculi, it arises from the base of the mastoid process and is inserted into the lower part of the concha. The retrahens and the attollens aurem are supplied by the pos- terior auricular branch of the facial nerve ; the attrahens, by an offset from the temporal branch of the same nerve. B 2 4 ARTERIES OF THE SCALP. AKTEKIES OF The arteries of the scalp are derived, in front, SCALP. from the supra-orbital and frontal arteries, branches of the ophthalmic artery which is a branch of the internal carotid ; on the sides, from the temporal; behind, from the occipital and posterior auricular, all branches of the external carotid. The frontal emerges from the orbit at its inner angle ; it runs up- wards for a short distance on the forehead and inosculates with the following artery. The supra-orbital passes through the supra-orbital notch and then divides into a superficial and a deep branch. It distributes branches, some of which ascend towards the top of the head and communicate with the temporal and frontal arteries. The temporal, about two inches above the zygoma, divides into two branches an anterior and a posterior. The anterior runs forwards in a tortuous course and anastomoses with the supra-orbital and frontal arteries ; the posterior (usually the larger) arches backwards over the temporal fascia, and its branches communicate with the corresponding branch of the opposite side and with the occipital and posterior auri- cular arteries. The posterior auricidar is a small vessel seen in the cleft between the ear and the mastoid process. It ascends, and divides into two branches : one, the mastoid or occipital, which passes backwards and inoscu- lates with the occipital ; the other, the auricular, which runs forwards above the ear and communicates with the posterior branch of the temporal artery. The occipital may be noticed piercing the trapezius near to the external occipital protuberance ; ascending over the back of the head, it divides into numerous branches which inosculate with the preceding arteries. The frontal vein passes downwards with its corresponding artery, and joins the supra-orbital vein, to form the angular vein. The other veins of the scalp accompany their respective arteries. NERVES OF THE The sensory nerves of the scalp are derived from SCALP. each of the three divisions of the fifth cranial nerve, namely, the ophthalmic, the superior and inferior maxillary ; also from the second cervical nerve. The nerves to the muscles of the scalp and ear come from the facial, which is one of the divisions of the seventh cranial nerve. SENSORY NERVES OF THE SCALP. In front will be found the supra-trochlear and supra-orbital nerves ; in the temporal region, there are the temporal filament from the orbital branch of the superior maxillary, the auriculo- temporal, and the temporal branches of the facial nerve ; and behind will be seen the posterior auricular branch of the facial, the small and great occipital nerves, and occasionally, a small filament from the posterior division of the sub-occipital nerve. FIG. 2. DIAGRAM OF THE SENSORY NERVES OF THE SCALP AND FACE. , I 1. Great occipital. %, _i,'/u CiA/wc-0-X. g. Supra-trochlear. J >'' 2. Small occipital. >o *AW*- , . 9. Malar br. of superior maxillary nerve. 3. Auricular br. of thejmeumogastric. 10. Infra-trochlear. /lv -^ 4. Great auricular. ^poK^C i/wHC.J.^ - iijv fj 5* 14. Mental. -' ^J ,,-. The supra-trochlear nerve is derived from the frontal branch of the ophthalmic division of the fifth. It appears at the inner angle of the orbit, and ascending beneath the orbicularis palpebrarum and occipito- frontalis, it finally supplies the skin of the forehead, and the upper eyelid. The supra-orbital nerve is a continuation of the frontal branch of the fifth. It emerges from the orbit through the notch in the frontal 6 NERVES OF THE SCALP. bone, and subdivides into branches, which are covered at first by the fibres of the orbicularis and occipito-frontalis ; but they presently become subcutaneous, and terminate in two branches an inner, which ascends, to supply the structures as high as the parietal bone ; and an otiter and larger, which may be traced over the vertex as far as the occipital bone. The temporal branch of the orbital branch of the superior maxillary nerve pierces the temporal fascia about an inch above the zygoma, and is distributed to the skin of the temple, communicating with the facial nerve and occasionally with the following. The auriculo-temporal nerve, a branch of the inferior maxillary nerve, after sending a small filament to the upper part of the pinna, divides into two branches, which accompany the divisions of the super- ficial temporal artery ; of these, the posterior is the smaller. The anterior communicates with the facial nerve, and with the orbital branch of the superior maxillary. The temporal branches of the facial nerve lie superficial to the temporal fascia, and supply the attrahens and attollens aurem, the orbi- cularis palpebrarum, the corrugator supercilii and the occipito-frontalis. These branches communicate with the temporal branch of the superior maxillary, the auriculo-temporal nerve, and with the lachrymal and supra- orbital branches of the ophthalmic. The posterior atirictdar nerve is a branch of the facial, and divides like its accompanying artery behind the pinna of the ear into a pos- terior or occipital branch which supplies the posterior belly of the occipito-frontalis, and into an anterior or aurlctdar branch which ends in the auricle, the retrahens and attollens aurem. It communicates with the great auricular and small occipital nerves, and with the auricular branch (Arnold's) of the pneumogastric. The auricular branch of the pneumogastric (Arnold's) emerges from the auricular fissure immediately behind the pinna, and supplies the skin of the pinna and the neighbourhood. The great occipital nerve is the internal branch of the posterior division of the second cervical nerve. After piercing the complexus it appears on the occiput with the occipital artery, and divides into wide- spreading branches which supply the skin. It communicates with the posterior auricular, the small occipital, and the third cervical nerves. The small occipital nerve, a branch of the anterior division of the second cervical nerve, runs along the posterior border of the sterno- mastoid and supplies the scalp behind the ear. It communicates with the great auricular, and with the two preceding nerves. NERVES OF THE SCALP. 7 Occasionally, though rarely, a cutaneous branch of the suboccipital nerve is distributed to the back of the head. FIG. 3. DIAGBAJI OF THE BRANCHES OF THE FACIAL NEEVE. 1. Branch to occipito-frontalis. 2. Posterior auricular. 3. Temporal brs. 4. Malar brs. 5. Infra-orbital. 6. Buccal. 7. Supra-maxillary. 8. Infra-maxillary. POINTS OF SUB- Raise the aponeurosis of the scalp, and observe GICAL INTEREST. the quantity of loose connective tissue which intervenes between it and the pericranium. This tissue never contains fat. There are some points of surgical interest concern- ing it : 1. Its looseness accounts for the extensive effusions of blood which one often sees after injuries of the head. 2. It admits of large flaps of the scalp being detached from the skull- cap ; but these flaps rarely slough, unless severely damaged, because they carry their blood-vessels with them. 3. In phleg- monous erysipelas of the scalp, the connective tissue becomes infiltrated with pus and sloughs ; hence the necessity of making incisions : for the scalp will not lose its vitality, and liberate the sloughs like the skin of other parts under similar conditions, DURA MATER. because its vessels run above the diseased tissue, and therefore its supply of blood is not cut off. LYMPHATICS OF The lymphatics of the scalp run for the most THE SCALP. part backwards towards the occiput to join the occipital and posterior auricular glands; a few run towards the root of the zygoma, where they enter the parotid lymphatic glands. It is in these situations, therefore, that one finds glandular enlarge- ments when the scalp is diseased. To examine the brain and its membranes, the skull-cap must be removed about half an inch above the supra-orbital ridges in front, and on a level with the occipital protuberance behind. The student should remember that the bone in the temporal region is very thin, and that here especial care is needed that the brain be not injured by the saw. It is better to saw only through the outer table of the skull, and to break through the inner with a chisel. In this way the dura mater and the brain are less likely to be injured. On removing the skull- cap, which is more or less intimately attached to the subjacent membrane, we expose a tough fibrous layer, the dura mater, which forms the most external of the membranes of the brain. The meningeal arteries ramify between the skull and the dura mater. We cannot, however, with the brain in situ, trace their course, at present, throughout ; so their consideration must be deferred until the brain has been removed. This membrane is so called because it was thought to give rise to all the other fibrous mem- Dranes in the body. It is a dense white fibrous membrane, rough on its outer aspect, where it is more or less adherent to the inner surface uf the skull, forming its internal periosteum. On its inner surface it is smooth and shining, being lined by a layer of endo- thelial cells, which anatomists now describe as constituting a part of the dura mater. In consequence, the term ' subdural space ' is now substituted for the old one ' the cavity of the arachnoid.' The dura mater differs in its adhesion to the subjacent bones : its ad- hesion is firmest at the sutures, the petrous portion of the temporal bone, the basilar process, the body of the sphenoid, the cribriform plate of the ethmoid bone, the depressions for the Pacchionian DURA MATER. 9 bodies, and at the margin of the foramen magnum. In front it sends downwards a prolongation into the foramen csecum ; also numerous small tubular sheaths through the foramina in the cribriform plate. It further sends a prolongation through the optic foramen, and another through the sphenoidal fissure into the orbit. The dura mater is supplied with nerves by the recurrent branch of the fourth nerve, and by the fifth cranial nerve. Filaments have likewise been traced into it from the sympathetic and from the Gasserian ganglion. Its remarkably tough and fibrous structure adapts it exceed- ingly well to the four purposes which it serves : 1. It forms the internal periosteum of the skull. 2. It forms, for the support of the lobes of the brain, three partitions namely, the falx cerebri, the falx cerebelli, and the tentorium cerebelli. 8. It forms the sinuses or venous canals which return the blood from the brain. 4. It forms sheaths for the nerves as they leave the skull. Of the partitions formed by the dura mater for the support of the lobes of the brain, two are vertical, and separate, respectively, the two hemispheres of the cerebrum, and those of the cerebellum ; the third arches backwards, and supports the posterior lobes of the cerebrum. This partition is named, from its resemblance to the blade of a sickle, falx cerebri. It is received into the longitudinal fissure, and separates the two cerebral hemi- spheres. It begins in a point attached to the crista galli, and gradually becomes broader as it extends backwards. Its upper edge is convex, and attached to the median groove on the inner aspect of the vertex of the skull ; its lower margin is concave and free, and runs along the upper aspect of the corpus callosum. From its base or broadest part proceeds the sloping arched par- TENTORIUM tition named tentorium cerebelli. This forms an CEREBELLI. arch for the support of the posterior lobes of the cerebrum, so that they may not press upon the cerebellum beneath. The tentorium is attached to the transverse ridge of the occipital bone, to the superior border of the petrous portion of the temporal bone, and to the posterior and anterior clinoid processes of the 10 GLA^DUL^E PACCHIONI. sphenoid. In front there is a large oval opening to allow of the passage of the crura cerebri. The small median partition which separates the lobes of the cerebellum is called the FALX CEKEBELLI. * . falx cerebelh. It is placed vertically in the same plane with the falx cerebri, and its point is downwards towards the foramen magnum. As it approaches the foramen it usually divides into two small folds. GLANDULE In the neighbourhood of the superior longitu- PACCHIONI. dinal sinus, we meet with small white elevated granulations, sometimes arranged singly, sometimes in clusters, which are received into the depressions on the inner aspect of the skull-cap. They are termed glandulce Pacchioni, 1 and are found in four situations : 1. On the outside of the dura mater, close to the superior longitudinal sinus, and so large as to occasion depressions in the bones. 2. Along the margin of the fissure of Sylvius. 3. On the surface of the pia mater. 4. In the interior of the superior longitudinal sinus, covered by its lining membrane. 5. On the poste- rior and antero-inferior parts of the posterior lobe of the cerebrum. They are due to an increased growth of the villi, which are normally found in the arachnoid membrane, and make their way, through the dura mater or the pia mater, to the different situations in which they are found. The greatest growth takes place from the visceral layer, as may be seen in the dissection of the brain. These bodies are not found at birth, but usually commence their growth about the third year, and are always found at the seventh year, after which they gradually increase as life advances. 2 SINUSES OF THE It is one of the peculiarities of the cerebral cir- DUBA MATER. culation, that the blood is returned through canals or sinuses formed by the dura mater. These canals are produced by a splitting of the dura mater into two layers as shown in fig. 4, where 1 represents a vertical section through the superior longitu- dinal sinus. They are lined by the same smooth membrane con- tinuous with that of the venous system. Since their walls consist of unyielding structure, and are always on the stretch, it is obvious 1 After the Italian anatomist who first described them, in 1705. 2 It is stated that when fluid is injected into the subarachnoid space it passes into the Pacchionian bodies. SINUSES OF THE DURA MATER. 11 FIG. 4. that they are admirably adapted to resist the pressure of the brain. There are fifteen of these sinuses, and they are classified into two groups a supero- posterior and an infer o-anterior. The supero- posterior group comprises the superior lon- gitudinal, the inferior longitudinal, the straight, the lateral, and the occipital sinuses ; while the infero-anterior group includes the cavernous, the circular, the superior and inferior petrosal, and the straight sinuses. Of these fifteen sinuses, five are pairs and five are single, as follows : DIAGRAM TO SHOW FOEJIA- TION OF A SINUS. The five pairs of sinuses are The lateral. The superior petrosal. The inferior petrosal. The cavernous. The occipital. The five single sinuses are The superior longitudinal. The inferior longitudinal. The circular. The transverse. The straight. FIG. 5. The blood from all these sinuses is eventually discharged into the internal jugular veins. SUPERIOR LON- This runs along the upper attached border of GITUDINAL SINUS. the falx cerebri (fig. 5). It begins very small at the foramen caecum, gradually increases in size in its course back- wards, and opposite the internal protuberance of the occipital bone opens into a triangular dilata- tion, the torcular Heropldli, or the confluence of the sinuses. It then divides into the right and left lateral sinuses, the right being generally the larger. Besides numerous vein's from the cancel- lous texture of the skull-cap, the superior longitudinal sinus re- ceives large veins from the upper part of each hemisphere of the cerebrum, and an emissary vein through the parietal foramen. It is interesting to observe that these veins run (as a rule) from behind forwards, contrary to the 1. Superior longitudinal sinus. 2. Inferior longitudinal sinus. 3. Straight sinus. 4. 4. Venae Galeni. 12 EEMOVAL OF THE BRAIN. current of blood in the sinus, and that they pass through the wall of the sinus very obliquely, like the ureter into the bladder. The probable object of this oblique entrance is to prevent regurgitation of blood from the sinus into the veins of the brain. Cut open the superior longitudinal sinus : observe that it is triangular with its base upwards, and that its cavity is intersected in many places by slender fibrous cords, termed chordce Willisii. 1 Their precise use is not understood. The brain should now be removed, and preserved in spirit for future examination. Its anatomy, with that of its remaining membranes, will be described in a subsequent part of this work. The brain is to be removed in the following DISSECTION manner : The dura mater should be cut through with a pair of scissors on a level corresponding with the sawn cal- varium, care being taken to cut completely through the falx cerebri in the front part of the longitudinal fissure. When this has been done the dura mater can be easily turned back over the brain, leaving its smooth, convex surface exposed. Now lift up gently, with the fingers of the left hand, the frontal lobes from the anterior fossae, taking care to raise with the brain the soft olfactory lobes from the cribriform plate of the ethmoid. Two white flat nerves the optic come into view prior to their leaving the skull through the optic foramina; these must be divided with a sharp knife together with the ophthalmic arteries which lie beneath the corre- sponding nerves. 2 In the middle line, fixed firmly in the sella turcica, lies the pituitary body, attached to the brain by a process the infundibulum. It is not easy to remove this body from the fossa in which it rests, owing to its being retained in its position by dura mater. When this is removed, two round white nerves the third are observed, one on each side, lying on the inner free border of the tentorium cerebelli, immediately behind the anterior clinoid process of the sphenoid. Divide these and then proceed to cut through the tentorium cerebelli close to its attachment to 1 So called after Willis, who first described them in his work De Cerebri Anatome, 1664. 2 It is well that each pair of nerves should be cut through first on one side and then on the other, before passing on to the nerve next in numerical order. LATERAL SINUSES. 13 the posterior clinoid process and the upper border of the petrous portion of the temporal bone, as far back as the lateral sinus. If this be done with care, the nerves lying beneath the tentorium will not have been injured. Immediately external to the third nerves are the slender fourth nerves ; and still further outside are the soft flattened fifth nerves. Cut these through, still gently raising the brain from the skull base, when the seventh pair come into view as they pass backwards and outwards towards the internal auditory foramina. When these have been cut, we notice the two sixth nerves running directly forwards to pierce the dura mater covering the basilar process of the occiput. Divide these as they pierce the dura mater, when the three divisions of the eighth are brought well into view, lying behind and internal to the seventh ; the anterior one is the glosso-pharyngeal, the middle one is the pneumogastric, and the hindermost one is the spinal accessory, whose spinal por- tion can be traced coming up from the foramen magnum. These all emerge through the jugular foramina. Below and internal to these are the hypoglossal nerves, which usually pass through the dura mater in two fasciculi. Cut these, and then pass down the knife as far into the spinal canal as possible, and cut through the spinal cord, the two vertebral arteries, and the spinal portions of the spinal accessory nerves. Now lay the knife aside, when by gentle traction the brain can be easily removed from the skull. The other sinuses should now be examined. LATERAL These are the two great sinuses through which SINUSES. all the blood from the brain is returned to the jugular veins. Their course is well marked in the dry skull. The right is usually the larger. Each commences at the internal occipital protuberance, and proceeds at first horizontally outwards, enclosed between the layers of the tentorium, along a groove in the occipital bone and the posterior inferior angle of the parietal ; it then descends along the mastoid portion of the temporal bone, and again indenting the occipital bone, turns forwards to the foramen lacerum posterius, and terminates in the bulb of the internal jugular vein, 1 where it is joined by the inferior petrosal 1 It has, in some subjects, another outlet, through the foramen mastoideum, or else through the posterior condylar foramen. 14 SINUSES OF THE DURA MATER. sinus. It receives blood also from the inferior cerebral and cere- bellar veins, from the diploe, and the superior petrosal sinus. It communicates with the veins of the scalp through emissary veins, which pass through the mastoid and posterior condylar foramina. INFERIOR LON- This is of small size. It runs in the inferior OITUDINAL SINUS. free border of the falx cerebri, and terminates in the straight sinus at the anterior margin of the tentorium (fig. 5). This may be considered as the continuation of STRAIGHT SINUS. , ,. T , ,1 v p .L- the preceding. It runs along the hne 01 junction of the falx cerebri with the tentorium cerebelli, and terminates in the torcular Herophili at the divergence of the two lateral sinuses. It receives the inferior cerebral and the superior cerebellar veins, and also the two vence Galeni (fig. 5), which return the blood from the lateral and third ventricles of the brain. CAVERNOUS This is so called because its interior is inter- SINUS. sected by numerous cords. It extends along the side of the body of the sphenoid bone, outside the internal carotid artery. It receives the ophthalmic vein which leaves the orbit through the sphenoidal fissure and the anterior inferior cerebral veins; it communicates with the circular sinus which surrounds the pituitary body (fig. 6). At the apex of the petrous portion of the temporal bone it divides into the superior and inferior petrosal sinuses. This surrounds the pituitary body (p in the dia- ClRCULAR SlNUS. AC C\ 1 T- '3 'j.1, gram (tig. o), and communicates on each side with the cavernous sinus. The posterior branch is sometimes absent. PETROSAL These lead from the cavernous to the lateral SINUSES. sinuses. There are two on each side. The supe- rior runs along the upper portion of the pars petrosa, in the attached border of the tentorium eerebelli ; the inferior, the larger of the two, runs along the suture between the pars petrosa and the occi- pital bone, and ends in the lateral sinus just before this terminates in the internal jugular vein. The superior sinus receives the in- ferior cerebral, the superior cerebellar veins, and a small branch from the tympanum ; the inferior sinus is joined by the inferior cerebellar and auditory veins. SINUSES OF THE DURA MATER. 15 TEANSVEESE SINUS. This extends from one inferior petrosal to the other, across the basilar process of the occipital bone. It communicates below with the anterior spinal veins. OCCIPITAL These are very small. They commence around SINUSES. the margin of the foramen magnum, run in the falx cerebelli, and uniting to form a single sinus, opens into the FIG. 6. Third nerve .... Fourth nerve . . . Sixth nerve .... First branch of the I fifth } Superior petrosal sinus Inferior petrosal sinus Ophthalmic vein. Carotid artery. Cavernous sinus. DIAGEAM OF THE VENOUS SINUSES AT THE BASE 01? THE SKULL. torcular Herophili. 1 They join inferiorly with the posterior spinal veins. 1 The junction of the several sinuses opposite the spine of the occipital bone is termed the torcular Herophili, after the celebrated anatomist who first described it. It is a kind of triangular reservoir, with the base below, and presents six openings namely, that of the superior longitudinal sinus, those of the two lateral and of the two occipital, and that of the straight sinus. The term torcular is an incorrect version of the original word ff /urjSe ave/j.01 (3\dirTia(Tiv, TiOfjAv /SAe^xxptSas f/j.(f>vffa.i' oQpvfft re airoytiffiaffai ra virtp TOIV o^drcav, us /njS' 6 eK TTJS Ketf>a,\TJs iSpws Kanovpyfi. 32 TAESAL CARTILAGES. The skin of the eyelids is remarkably smooth and delicate, and destitute of fat. It is abundantly supplied with sensory nerves by branches of the fifth pair namely, by the supra- orbital, supra-trochlear, infra-trochlear, lachrymal, and infra-orbital nerves. The orbicularis palpebrarum has been already described (p. 28). It is supplied by the facial nerve. The levator palpebrce arises from the lesser wing of the sphenoid above the optic foramen, gradually becomes broader, and termi- nates in a thin aponeurosis, which unites with the broad tarsal ligament, and is lost on the upper surface of the superior tarsal cartilage. TARSAL CAR- These are plates of dense connective tissue, TILAGES AND which support and give shape to the eyelids. LIGAMENTS. There is one for each lid, and they are connected at the angles (commissures or canthi) of the lids through the medium of fibrous tissue. They can best be examined by everting the lids. Each cartilage resembles its lid in form. The upper is the larger, is broad in the middle, and gradually becomes narrower at either end. The lower is nearly of uniform breadth throughout. Both are thicker on the nasal than on the temporal side. They are connected to the margin of the orbit, and maintained in position by the broad tarsal or palpebral ligament this is a continuation from the periosteum of the orbit to the tarsal cartilage, and is denser at the outer part of the orbit. There are two of them upper and lower and they pass to each cartilage respectively. When an abscess forms in the connective tissue of the lids, these ligaments prevent the matter from making its way into the orbit. Each tarsal cartilage is attached on its outer side to the malar bone by the external tarsal ligament, and on its side to the nasal process of the superior maxillary by the tendo palpebrarum or the internal tarsal ligament. The free or ciliary margin is straight, and is the thickest part of the tarsal cartilages. It is generally stated that the inner edge of each is sloped or bevelled off; and that, when the lids are closed, there is formed, with the globe of the eye, a triangular PUNCTA LACHRYMALIA. 33 channel. This channel is said to conduct the tears to the puncta lachrymalia. According to our observation, this channel does not exist ; for when the lids are closed, their margins are in such accurate apposition, that not the slightest interspace can be dis- covered between them. PUNCTA The puncta lachrymalia are two pin-hole aper- LACHBYMALIA. tures, easily discovered on the margin of the lids, close to the inner angle. They are the orifices of the canals, called canaliculi, which pass inwards, and convey the tears into the lachry- mal sac. Observe that their orifices are directed backwards. The upper canaliculus, the longer and narrower of the two, ascends for a short distance nearly vertically, and then dilating into a small pouch makes a sharp bend inwards for about a quarter of an inch to join the lachrymal sac ; the lower canal descends perpendicularly, and, like the upper, makes a sharp bend, after which it pursues a direction upwards and inwards to the sac. The two canals open separately into the sac (sometimes by a common orifice). In facial palsy, the tensor tarsi being affected, the puncta lose their proper direc- tion, and the tears flow over the cheek. In the introduction of probes for the purpose of opening the con- tracted puncta, or of slitting up the lachrymal ducts, it is necessary to know the exact direction of these canals. (See diagram.) When from any cause the tears are secreted in greater quantity than usual, they overflow and trickle down the cheek. MEIBOMIAN These long compound sebaceous glands, so called GLANDS. after the anatomist J who first described them, are situated on the under surface of each of the tarsal cartilages. In the upper lid there are between twenty and thirty ; not quite so many in the lower. On everting the lid, they are seen running in longitudinal parallel rows in grooves in the cartilage. Under the 1 H. Meibom, De Vasis Palpebrarum novis. Helmstedt, 1666. D .34 MUSCLES OF THE NOSE. microscope, each is seen to consist of a straight central tube, round the sides of which are a number of openings leading to short cascal dilatations. The orifices of these glands are situated on the free margin of the lids behind the lashes. They are lined with flattened epithelial cells which, in the cgecal dilatations and ducts, become cubical and filled with fat. Their function is to secrete a sebaceous material, which prevents the lids from sticking together. This muscle is only a deeper part of the orbicu- laris palpebrarum, and lies just behind the tendo palpebrarum. To expose it, cut perpendicularly through the middle of the upper and lower lids, and turn the inner halves toward the nose. After removing the mucous membrane, the muscle will be seen arising from the ridge of the lachrymal bone. It passes nearly horizontally outwards, for about three lines, and then divides into two portions, which are inserted into the upper and lower tarsal cartilages, close to the orifices of the lachrymal ducts. It is pro- bable that the tensor tarsi draws backwards the open mouths of the ducts, so that they may receive the tears at the inner angle of the eye. It is supplied by a small branch from the facial nerve. Let us now examine the muscles in connection with the nose : namely the pyramidalis nasi, the compressor naris, the depressor alas nasi, and the smaller intrinsic muscles of the nose. All are supplied by the facial nerve. PYRAMIDALIS This is situated on the bridge of the nose, one NASI. on each side of the mesial line, and is usually regarded as a continuation of the inner part of the occipito-frontalis (p. 26). The two muscles diverge as they descend, and their fibres blend with those of the compressor naris. Their action produces transverse wrinkles of the skin at the root of the nose, as in the expression of an aggressive feeling. COMPRESSOR This muscle is triangular, and arises by its NARIS. apex from the inner side of the canine fossa of the superior maxilla, and is attached to a broad thin aponeurosis which spreads over the dorsum of the nose, and joins its fellow. The origin of this muscle is concealed by the levator labii superioris alaeque nasi. When this muscle is reflected from its junction with its fellow, MUSCLES OF THE NOSE AND LIP. 35 a small nerve is seen running down towards the tip of the nose. This nerve is the superficial branch of the nasal nerve (called also naso-lobular'). It becomes subcutaneous between the nasal bone and the cartilage, and supplies the tip and lobule of the nose. It is joined by a branch of the facial nerve at its termination. DEPRESSOR ALJE This arises from the superior maxilla, above NASI. the second incisor tooth, and is inserted into the septum and ala of the nose. It is situated between the mucous membrane and the muscular structure of the upper lip ; so that, to expose it, the upper lip must be everted, and the mucous mem- brane removed. Besides the muscles above described, we find in connection with the cartilages of the alas of the nose, pale muscular fibres which have no very definite arrangement and require a lens for their detection. The dilatator naris posterior arises from the nasal pro- cess of the superior maxilla and the sesamoid cartilages, and is in- serted into the skin of the margin of the nostril j the dilatator naris anterior, descends vertically from the cartilage of the aper- ture to its free margin. The action of these small muscles is to raise and evert the ala of the nose, and to counteract its tendency to be closed by atmospheric pressure. In dyspnoea, and in certain mental emotions, they contract with great energy. LEVATOR LABII This ar i ses from the nasal process of the supe- SUPERIORIS rior maxillary bone near its orbital margin, and AI^EQUE NASI. passing downwards divides into two portions : an inner inserted into the side of the ala of the nose ; an outer, into the upper lip, where its fibres blend with the orbicularis oris and levator labii superioris. It acts chiefly in expressing the smile of derision. Its habitual use occasions the deep furrow which, in most faces, runs from the ala of the nose towards the corner of the mouth. LEVATOR LABII This arises from the lower margin of the orbit, SUPERIORIS i.e. from the superior maxilla and malar bone, PROPRIUS. above the infra-orbital foramen, and is inserted into the upper lip, where its fibres blend with the orbicularis oris. It is nearly an inch in breadth at its origin, which covers the infra-orbital vessels and nerves, and is itself overlapped by the orbicularis palpebrarum. D 2 36 BUCCINATOR. LEVATOB This muscle, which is covered by the levator ANGULI OBIS. labii superioris, arises from the canine fossa of the superior maxilla, below the infra-orbital foramen, and is inserted into the angle of the mouth, superficial to the buccinator, its fibres blending with those of the orbicularis oris, the zygomatici, and the depressor anguli oris. The buccinator arises from the outer surface of the alveolar borders of the upper and lower jaws corresponding to the molar teeth, and behind from the pterygo- maxillary ligament. The fibres pass forwards and converge, to be inserted into the angle of the mouth and the muscular structure of the lips ; the central fibres decussate, while the upper fibres pass to the upper lip, and the lower fibres pass to the lower lip. The muscle is covered on its inner aspect by the mucous membrane of the cheek, and on its outer by a thin fascia which passes backwards, and is continuous with that covering the pharynx. The buccinator is the principal muscle of the cheek. It forms with the superior constrictor of the pharynx a continuous muscular wall for the side of the mouth and pharynx. The bond of connec- tion between the buccinator and the superior constrictor is a ten- dinous band, the pterycjo-maxillary ligament. This ligament (see diagram) extends from the hamular process vertically to the poste- rior extremity of the mylo-hyoid ridge of the lower jaw near the last molar tooth. It is simply a fibrous intersection between the two muscles. The duct of the parotid gland pierces the buccinator obliquely, and opens into the mouth opposite the second molar tooth of the upper jaw. The chief use of the buccinator is to keep the food between the teeth during mastication. It can also widen the mouth. Its power of expelling air from the mouth, as in whistling or playing on a wind instrument, has given rise to its peculiar name. It is supplied by the facial nerve, and is, therefore, affected in facial paralysis. The buccinator is in relation, externally and behind, with a large amount of buccal fat, with the masseter and temporal muscles ; in front with the risorius, the levator anguli oris, depressor anguli BUCCAL FASCIA. 37 oris, the zygomatici, the duct of the parotid gland, the facial artery and vein, and the facial and buccal nerves ; internally with the mucous membrane of the mouth and buccal glands ; and pos- teriorly with the pterygo-maxillary ligament. FIG. 15. Tensor palati. Levator palati. Orbicularis oris . . Pterygo-maxill ary ligament . . Mylo-hyoideus . . Os hyoides . . . _ Thyro-hyoid liga- 1 ment . . . . / Pomum Adami . . Cricoid cartilage . Trachea . . . . Glosso-pharyngeal n. Stylo-pharyngeus. Superior laryngeal n. and a. External laryngeal n. Crico-thyroideua. Inferior laryngeal n. CEsopliagus. MUSCLES OF THE PHARYNX. BUCCAL FASCIA. The buccinator muscle is covered by a thin layer of fascia, which adheres closely to its surface, and is attached to the alveolar border of the upper and lower jaws. This structure is thin over the anterior part of the muscle, but more dense behind, where it is continuous with the aponeurosis of 88 FACIAL AKTERY. the pharynx. It is called the bucco-pharyngeal fascia, since it supports and strengthens the muscular walls of these cavities. In consequence of the density of this fascia, abscesses do not readily burst into the mouth or the pharynx. BUCCAL AND The luccal glands, in structure compound race- MOLAR GLANDS. mose like the salivary, are situated between the buccinator and the mucous membrane. They resemble the labial glands found beneath the mucous membrane of the lips, though somewhat smaller. Three or four other glands, about the size of a little split pea, should be made out, as they lie between the masseter and buccinator: these are the molar glands. Their secretion, said to be mucous, is conveyed to the mouth by separate ducts near the last molar teeth. Between the buccinator and the masseter, there is, in almost all subjects, an accumulation of fat. It is found, beneath the zygoma especially, in large round masses, and may be turned out with the handle of the scalpel. It helps to fill up the zygomatic fossa, and being soft and elastic, presents no obstacle to the free movements of the jaw. Its absorption in emaciated individuals occasions the sinking of the cheek. The facial (external maxillary) artery is the third branch of the external carotid. It ascends tortuously beneath the posterior belly of the digastricus and the stylo-hyoideus, next through or under the substance of the sub- maxillary gland ; it then rests upon the mylo-hyoideus, and sub- sequently mounts over the base of the jaw at the anterior edge of the masseter muscle. This part of the course of the facial will be fully examined further on in the dissection of the neck. It now ascends tortuously near the corner of the mouth and the ala of the nose, towards the inner angle of the eye, where, much diminished in size, it inosculates with the terminal branch of the ophthalmic, a branch of the internal carotid. In the first part of its course on the face, the artery is covered by the platysma and the deep fascia ; above the corner of the mouth it is crossed by a few fibres of the risorius and the zygomatici ; still higher it is covered by some of the fibres of the elevator of the upper lip. 1 It lies successively 1 Not infrequently the artery lies superficial to this muscle. FACIAL ARTERY. 39 upon the buccinator, levator anguli oris, and levator labii superioris alasque nasi muscles. In its course along the face it gives off the following branches : FIG. 16. BKANCHES OF THE EXTERNAL CAROTID ARTEEY. 1. External carotid. 2. Lingual. 3. Facial. 4. Inferior labial. 5. Inferior coronary. 6. Superior coronary. 7. Lateral nasal. 8. Angular. 9. Superior thyroid. 10. and 16. Occipital. 11. Posterior auricular. 12. Anterior auricular. 13. Internal maxillary. 14. Transverse facial. 15. Middle temporal. 17. Anterior temporal. 18. Posterior temporal. 19. Supra-orbital. 20. Frontal. a. The inferior labial artery passes inwards under the depressor anguli oris and inosculates with the mental branch of the inferior dental, the inferior coronary, and the submental arteries. 40 FACIAL ARTERY. b. The inferior coronary artery comes off near the angle of the mouth, either directly from the facial, or in common with the superior coronary. It runs tortuously along the lower lip, beneath the depressor anguli oris ; it then pierces the orbicularis, running between this muscle and the mucous membrane of the lip. It inosculates largely with its fellow, the inferior labial and the mental arteries. c. The superior coronary, larger than the preceding, is given off beneath the zygomatici. It proceeds along the upper lip close to the mucous membrane, and inosculates with its fellow ; thus is formed round the mouth a complete arterial circle, which can be felt pulsa- ting on the inner side of the lip, near the free border. From this circle numerous branches pass off to the papillae of the lips, and the labial glands. The superior coronary gives off a branch, the artery of the septum, which ascends along the septum to the apex of the nose ; also a small one to the ala nasi. d. The lateral artery of the nose, a branch of considerable size, arises opposite the ala nasi, ramifies upon the external surface of the nose, and inosculates with the nasal branch of the ophthalmic artery, the infra- orbital, and the artery of the septum. e. The angular artery, which may be regarded as the termination of the facial, inosculates on the inner side of the tendo palpebrarum with the nasal branch of the ophthalmic artery. The facial artery supplies numerous branches to the muscles of the face, and inosculates with the transversalis faciei, infra-orbital, the mental, the sublingual branch of the lingual, the nasal branches of the internal maxillary and the ophthalmic, the ascending pharyngeal and descending palatine arteries. The facial artery and its branches are surrounded by a minute plexus of nerves (nervi molles), invisible to the naked eye. They are derived from the superior cervical ganglion of the sympathetic, and exert a powerful influence over the contraction and dilatation of the capillary vessels, and thus occasion those sudden changes in the countenance indicative of certain mental emotions, e.g. 1 blushing or sudden paleness. 1 The facial vein does not run with the artery, but takes a 1 MM. Bernard and Brown-S6quard have proved by experiment, that if the branches of the sympathetic, which accompany the facial artery, be divided, the capillary vessels of the face, being deprived of their contractile power, become immediately distended with blood, and the temperature of the face is raised. PAROTID GLAND. 41 straight course from the inner angle of the eye to the anterior border of the masseter. In this course it descends upon the levator labii superioris, then passes beneath the zygomatic muscles, over the termination of the parotid duct, and at the anterior border of the masseter passes over the jaw, behind the facial artery, and joins the internal jugular. The facial vein is a continuation of the frontal, which descends over the forehead, and, after receiving the supra-orbital, takes the name of angular at the corner of the eye. It communicates with the ophthalmic vein, receives the veins of the eyelids, the external part of the nose, the coronary veins, and others from the muscles of the face. Near the angle of the mouth it is increased in size by a communicating branch from the infra-orbital vein, and by a large vein which comes from the temporo-maxillary vein. The other veins which empty themselves into the facial correspond with the branches given off from the facial artery. ARTEKIA This artery arises from the temporal, or occa- TEANSVEESALIS sionally from the external carotid in the substance FACIEI - of the parotid gland. It runs forwards across the masseter between the parotid duct and the zygoma, and is dis- tributed to the glandula socia parotidis, and the masseter. It anastomoses with the infra-orbital, buccal and facial. It is seldom of large size, except when it supplies those parts which usually receive blood from the facial. We have seen it as large as a goose- quill, furnishing the coronary and the nasal arteries ; the facial itself not being larger than a sewing thread. The parotid gland is now to be examined. Its boundaries, its deep relations, the course of its duct, and the objects contained within the gland, must be carefully observed. PAROTID The parotid, 1 the largest of the salivary glands, GLAND. occupies the space between the ramus of the jaw and the mastoid process, and weighs between five and eight drachms. It is bounded above by the zygoma ; below, by the sterno-mastoid and digastric muscles ; behind, by the meatus auditorius externus and the mastoid process; in front, it lies over the ascending ramus of the jaw, and is prolonged for some distance over the masseter. 1 From iropa, near ; oSs, the ear. 42 PAROTID GLAND. It is separated from the submaxillary gland by the stylo-maxillary ligament ; sometimes the two glands are directly continuous. The superficial surface of the gland is flat, and covered by a strong layer of fascia, a continuation of the cervical, and has one or two lymphatic glands lying on it. It not only surrounds the gland, but sends down numerous partitions which form a frame- work for its lobes. The density of this sheath explains the pain caused by inflammation of the gland, the tardiness with which abscesses within it make their way to the surface, and the propriety of an early opening. The deep surface of the gland is irregular, and moulded upon the subjacent parts. Thus it sends a prolongation which passes inwards between the neck of the jaw and the internal lateral liga- ment ; another process which passes in front of the styloid process, and extends upwards and occupies the posterior part of the glenoid cavity ; a third process passes behind the styloid process, below the mastoid process and behind the sterno-mastoid muscle, and sometimes penetrates deep enough to be in contact with the internal jugular vein. The internal carotid artery and internal jugular vein are in contact with the gland behind. On carefully removing the substance of the parotid gland, the following structures are seen in its interior, proceeding in the order of their depth from the surface : 1. Two or more small lymphatic glands. 2. The pes anserinus, or primary branches of the facial nerve r which emerge at its anterior border. 3. Branches from the great auricular and auriculo-temporal nerves which communicate in its substance with the facial nerve. 4. The external jugular vein formed by the junction of the internal maxillary and temporal veins. 5. The external carotid artery, which, after distributing many branches to the gland, divides, opposite the neck of the jaw, into the internal maxillary and temporal ; the latter giving off in the gland the posterior auricular and transverse facial arteries. 1 1 Keviewing the intimate and deep connections of the parotid gland, one cannot but conclude that it is almost impracticable to remove it entirely during life. If PAROTID GLAND. 43 That portion of the gland which lies on the masseter muscle is called glandula soda parotidis. It varies in size in different subjects ; and is situated chiefly above the parotid duct, into which it pours its secretion by one or two smaller ducts. The duct of the parotid gland (ductus Stenonis ! ), about two inches and a half long, is very thick and strong. In this respect it differs from the duct of the submaxillary gland, which is less exposed to injury. It runs transversely forwards over the mas- seter, about an inch below the zygoma, through the fat of the cheek, then perforates the buccinator obliquely, and opens into the mouth opposite the second molar tooth of the upper jaw. Near its termination it is crossed by the zygomaticus major and the facial vein. After perforating the buccinator, the duct passes for a short distance between the muscle and the mucous membrane. Its orifice is small and contracted compared with the diameter of the rest of the duct, which will admit a crow-quill ; it is not easily found in the mouth, being concealed by a fold of mucous membrane. The direction of the parotid duct corresponds with a line drawn from the middle of the lobule of the ear to a point midway between the nose and the mouth. The blood supply of the parotid is derived from the external carotid and its branches, which are accompanied by their respective veins. Its nerves are supplied from the sympathetic plexus around the external carotid, the auriculo-temporal, the great auricular and the facial nerves. The lymphatic glands about the parotid deserve notice, since they are liable to become enlarged, and simulate disease of the parotid itself. A lymphatic gland lies close to the root of the zygoma, in front of the cartilage of the ear ; this gland is some- times affected in disease of the external tunics of the eye ; e.g. in purulent ophthalmia : also in affections of the scalp. this conclusion be correct, even in the normal condition of the gland, what must it be when the gland is enlarged by disease ? John Bell, however, relates a case in which he was induced to attempt the extirpation of a diseased parotid (Principles of Surgery, vol. iii. p. 262). Other surgeons, too, of more modern date, have attempted the same thing. It is not unlikely that they have mistaken a tumour in the substance of the parotid for disease of the parotid itself. 1 Nic. Steno, De Glandulis Oris, etc. Bat. 1661. 44 THE FACIAL NERVE. The parotid belongs to the compound racemose form of glands. Tracing its main duct into the substance of the gland, we find that it divides into smaller ones, which again divide into the smaller ramuscules which open into caecal dilatations called alveoli. Each alveolus about 12 * 00 of an inch in diameter has a more or less defined basement membrane upon which the cells rest. The cells are flattened and spheroidal, enclosing nuclei, some of them having outstanding processes from the bases of the cells. An aggregation of these alveoli forms a small lobule, from which a small excretory duct proceeds ; these lobules are united by intervening connective tissue, which is a continuation inwards of the dense fascia covering the gland. The connective tissue varies much in thickness in different situations, and where it is most abundant it is distinctly lamellar (Klein), 1 and contains numerous granular plasma cells and lymphoid tissue. The small ramuscules have only a basement membrane with flattened cells, which change in the smaller ducts to a columnar form, while in the larger ducts the epithelium is squamous. The parotid gland secretes an alkaline watery fluid, containing solids which amount to 6 parts in 1,000. The solids consist of ptyalin, a special ferment, mucus, and certain salts, chiefly sulpho- cyanide of potassium, chlorides and phosphates of potassium, sodium, lime, and magnesia. Apart from its mechanical proper- ties, the parotid secretion has the power, by means of its ptyalin, of converting starch into dextrine and grape sugar. To display the plexus of nerves (pes anserinus), formed by the branches of the facial, cut into the parotid gland by a vertical incision until the main trunk of the nerve is reached. POBTIO DURA, This is the seventh cranial nerve, and is the OB FACIAL NERVE, motor nerve of the face. It supplies all the muscles of expression, the platysma, and the buccinator. Through some of its branches it supplies other muscles, the description of which will be deferred till the facial nerve is dissected in the tem- poral bone. It arises immediately below the pons Varolii, from the lateral tract of the medulla oblongata, between the olivary and restiform bodies. The nerve enters the meatus auditorius internus, 1 Klein, Quarterly Journal of Microscopical Science, 1882. THE FACIAL NERVE. 45 lying upon the auditory nerve, traverses a tortuous bony canal (aqueductus Fallopii) in the petrous portion of the temporal bone r and leaves the skull at the stylo-mastoid foramen. Its course and connections in the temporal bone will be studied hereafter : at present we must trace the facial part of the nerve. Having emerged from the stylo-mastoid foramen, the nerve enters the parotid gland, and divides behind the ramus of the jaw into two primary branches, named, from their distribution, temporo- facial and cervico-facial. These primary branches cross over the external carotid artery and the external jugular vein, and form, by their communications within the substance of the parotid, the plexus called pes anserinus, from its fancied resemblance to the skeleton of a goose's foot. (Diagram, p. 46.) Close to the stylo-mastoid foramen, the facial nerve gives off its 'posterior auricular branch (p. 6), which ascends behind the ear and divides into two, an auricular and an occipital ; the former supplies the retrahens and attollens aurem, the latter the posterior belly of the occipito-frontalis. This branch communicates with the deep branch of the great auricular n., with the small occipital, and with the auricular branch of the pneumogastric. Its two next branches supply the stylo-hyoideus and the posterior belly of the digastricus. The digastric nerve enters the muscle by many fila- ments ; the nerve to the stylo-hyoid is long and enters the muscle about the middle. The stylo-hyoid branch communicates with the sympathetic on the external carotid a. ; the digastric branch with the glosso-pharyngeal near the base of the skull. These two muscular nerves are frequently given off from a common branch. The temporo-facial division, the larger of the two, in passing through the parotid gland, crosses the external carotid and the neck of the jaw, receives two or more communications from the auriculo-temporal (branch of the fifth) and subdivides into temporal, malar, and infra-orbital branches. The temporal branches ascend over the zygoma, supply the frontalis, the attrahens aurem, the orbicularis palpebrarum, the corrugator super- cilii, and tensor tarsi, and communicate with filaments of the supra- orbital nerve, with the temporal branch of the superior maxillary n., with the auriculo-temporal n., and with the lachrymal n. 46 THE FACIAL NERVE. The malar branches cross the malar bone, supply the orbicular muscle, and communicate with filaments of the lachrymal, the supra- orbital, the superior maxillary, and the malar branch of the superior maxillary. FIG. 17. DIAGRAM OF THE BBANCHES OF THE FACIAL NERVE. 1. Branch to occipito-froutalis. 5. Infra-orbital. 2. Posterior auricular. 6. Buccal. 3. Temporal brandies. 7. Supra-maxillary. 4. Malar branches. 8. Infea-maxillary. The infra-orbital branches are the largest, and proceed transversely forwards over the masseter beneath the zygomatici, to supply the orbi- cularis oris, the elevators of the upper lip, and the muscles of the nose. The superficial branches join with the nasal and infra-trochlear branches of the ophthalmic along the side of the nose ; the deep branches com- municate beneath the levator labii superioris with the infra-orbital branches of the superior maxillary nerve forming the infra-orbital plextis, and also with the buccal branches of the facial. The cervico-facial division, joined in the parotid gland by fila- ments from the great auricular (branch of the cervical plexus), descends towards the angle of the jaw, and subdivides into buccal, supra- and infra-maxillary branches. SENSORY NERVES OF THE FACE. 47 The buccal branches pass forwards over the masseter parallel with the parotid duct, and supply the buccinator : they communicate with the buccal branch of the inferior maxillary nerve (third division of the fifth), and with the infra-orbital nerve. The supra-maxillary branches advance over the masseter and facial artery, and run under the platysma and the depressor muscles of the lower lip, all of which they supply. Some of the filaments communicate with the mental branch of the inferior dental nerve. The infra-maxillary or cervical branches, one or more in number arch forwards below the jaw covered by the platysma, as low as the hyoid bone, and communicate with the superficial cervical (branch of the cervical plexus). SENSORY NERVES These are the supra-orbital, the supra- and infra- OF THE FACE. trochlear, the naso-lobular, the temporo-malar, the infra-orbital, and the mental, all branches of the fifth pair. The supra-orbital nerve is the continuation of the frontal, which is a branch of the first division of the fifth pair. It leaves the orbit through the supra-orbital notch and ascends upon the fore- head, at first covered by the orbicularis and occipito-frontalis. It presently divides into two sets of branches an outer, the larger, which passes backwards as far as the occipital bone, and an inner, which ascends as far as the parietal bone. It distributes sensory muscular branches also to the orbicularis palpebrarurn, corrugator supercilii, the occipito-frontalis, to the pericranium and branches which supply the skin of the forehead, upper eyelid, and scalp. It communicates with the facial nerve on the forehead. The supra- orbital artery is a branch of the ophthalmic. The supra-trochlear n., or internal frontal, appears at the inner angle of the orbit between the supra-orbital foramen and the pulley of the superior oblique, and sends down in front of the pulley a loop to communicate with the infra-trochlear branch of the nasal. The main trunk of the nerve ascends to the forehead. Its further course has been described (p. 5). The infra-trochlear n. issues from the orbit below the pulley, and supplies branches to the eyelids, the conjunctiva, lachrymal sac, and the side of the nose. The infra-orbital nerve is the terminal branch of the superior 48 SENSORY NERVES OF THE FACE. maxillary or second division of the fifth nerve. It emerges with its artery from the infra-orbital foramen, covered by the levator labii superioris. The nerve immediately divides into several FIG. 18. DIAGRAM OF THE SENSORY NERVES OF THE SCALP AND FACE. 1. Great occipital. 2. Small occipital. 3. Auricular br. of the pneumogastric. 4. Great auricular. 5. Auriculo-temporal. 6. Temporal br. of superior maxillary nerve. 7. Supra-orbital. 8. Supra-trochlear. 9. Malar br. of superior maxillary nerve. 10. Infra-trochlear. 11. Kaso-lobular. 12. Infra-orbital. 13. Buccal br. of inferior maxillary nerve. 14. Mental. branches, palpebral, nasal, and labial ; the palpebral, ascending be- neath the orbicularis, supply the lower eyelid, and communicate with the facial and the malar branch of the orbital nerve ; the nasal pass inwards to supply the nose, and join the nasal branch (naso-lobular) of the ophthalmic ; the labial, by far the most nume- rous, descend into the upper lip, beneath the levator labii superioris, and eventually terminate in lashes of filaments, which endow the papillse of the lip and the mucous membrane of the mouth with exquisite sensibility. Close to the infra-orbital foramen is the infra-orbital plexus, before alluded to (p. 46). DISSECTION OF THE ORBIT. 49 The infra-orbital artery is the terminal branch of the internal maxillary ; it supplies the muscles, the skin, and the front teeth of the upper jaw, and inosculates with the transverse facial, buccal, facial, and coronary arteries. The naso-lobular nerce is the external branch of the nasal nerve and is distributed to the tip and lobule of the nose, and is joined by filaments from the facial nerve. The temporal branch of the orbital nerve (branch of the superior maxillary nerve, running along the outer wall of the orbit, and which divides into a temporal and a malar branch) issues through the temporal fascia about a finger's breadth above the zygoma, and supplies the skin of the temple. It communicates with the facial and the auriculo-temporal nerves. The malar nerve, a branch also of the orbital nerve, issues through a foramen in the malar bone, and, after piercing the orbi- cularis palpebrarum, supplies the skin of the cheek over the malar bone. It communicates with the facial and the palpebral branches of the infra-orbital nerve. The mental nerve is a branch of the inferior maxillary or third division of the fifth. It emerges from the mental foramen in the lower jaw, in a direction upwards and backwards, beneath the depressor anguli oris. It soon divides into a number of branches beneath the depressor labii inferioris, some of which supply the skin of the chin, but the greater number terminate in the papillee of the lower lip. It communicates with the facial nerve. The mental artery is a branch of the inferior dental. It supplies the gums and the chin, and inosculates with the sub-mental, the inferior labial, and inferior coronary arteries. _, To expose the contents of the orbit, remove that DISSECTION. . , . . , portion of the orbital plate, which forms the roof of the orbit, as far back as the optic foramen, making one section with a saw on the outer side, the other on the inner side of the roof, so that the two sections converge at the optic foramen. In doing this, be careful not to injure the little pulley on the inner side for the superior oblique. If the bone be sufficiently sawn through, a gentle tap with the saw on the front of the orbital plate will fracture its thin wall transversely. The anterior fourth of the 50 DISSECTION OF THE ORBIT. roof should be turned forwards and downwards and kept in this position by hooks ; the remainder is to be removed by bone forceps nearly as far as the optic foramen, so as to leave a ring of bone from which most of the ocular muscles have their origin. The eyeball should be made tense by blowing air through a blowpipe passed well into the globe through the cranial end of the optic nerve. PERIOSTEUM OF The roof being removed we expose the fibrous THE ORBIT. membrane which lines the walls of the orbit. It is a continuation of the dura mater through the sphenoidal fissure. Traced forwards, we find that it is loosely connected to the walls of the orbit, and that at the margin of the orbit it divides into two layers, one of which is continuous with the periosteum of the fore- head, the other forms the broad tarsal ligament which fixes the tarsal cartilage. The periosteum is now to be removed, and the fascia of the orbit made out. The following objects should then be carefully DIAGRAM Otf THE NERVES 01? THE ORBIT. traced : in the middle are seen the frontal artery and nerve, lying on the levator palpebrae ; on the outer side, the lachrymal nerve and artery pass forwards on the external rectus to the lachrymal gland, which lies under cover of the external angular process ; on CONTENTS OF THE ORBIT. 51 the inner side is the fourth nerve, lying on and supplying the superior oblique. FASCIA OF THE The fascia of the orbit provides the lachry- OKBIT AND CAPSULE mal gland and each of the muscles with a loose OF TENON. sheath, thin and delicate at the back of the orbit, but stronger near the eyeball. It is pierced behind by the optic nerve and by the arteries and nerves of the orbit, while in front it is connected with the ocular conjunctiva close to the cornea. The sheaths are firmly adherent to the muscles, and their tendinous in- sertions into the globe are connected by the fascia. From the in- sertions of the muscles it is reflected as a double layer backwards over the globe, so that it resembles a serous membranous sac a tunica vaginalis one layer being loosely connected with the globe, the other lining the fat in which the globe is set. These layers are lined with epithelium, and are separated by an external lymph space. This reflection of the orbital fascia is called the capsule of Tenon, its use being to allow free movement of the globe. The orbit contains a large quantity of granular fat, which forms a soft bed for the eye, and prevents its being retracted too far by its muscles. Upon the amount of this fat depends, in some measure, the prominence of the eyes. Its absorption in disease or old age occasions the sinking of the eyeballs. CONTENTS OF In the middle of the orbit is the eyeball, sur- ras ORBIT. rounded by more or less fat, and attached to it are six muscles which move it : four, running forwards in a straight direction, are called the recti, and are arranged one above, one below, and one on each side of the globe ; the remaining two are called, from their direction, obliqui, one superior, the other inferior. There is also a muscle to raise the upper eyelid, termed levator palpetoce. The nerves are : the optic, which passes through the optic foramen ; the third, the fourth, the first division of -the fifth, the sixth, and some filaments of the sympathetic, all of which pass through the sphenoidal fissure. The third supplies all the muscles with motor power, except the superior oblique, which is supplied by the fourth, and the external rectus, which is supplied by the sixth. The first or ophthalmic division of the fifth divides into a frontal, lachrymal, E 2 52 FRONTAL NERVE. and nasal branch. The ophthalmic artery, a branch of the internal carotid, passes into the orbit through the optic foramen ; its vein passes backwards through the sphenoidal fissure to join the cavern- ous sinus. The ophthalmic, or first division of the fifth a sensory nerve after giving off from its inner and lower side, whilst within the cavernous sinus, the nasal nerve, divides into the frontal and lachrymal nerves, of which the former is the larger. It is the smallest division of the fifth, and runs for- wards for the distance of about an inch ; in its course it is con- nected with the cavernous plexus of the sympathetic, with the third, fourth, and sixth nerves, and close to its origin from the Gasserian ganglion it sends off a small recurrent branch to the ten- torium cerebelli. One of its divisions, the frontal nerve, runs for- wards upon the upper surface of the levator palpebrse, on which, about midway in the orbit, it divides into two branches the supra- trochlear and the supra-orbital. FIG. 20. IN FRA-TROCHLEAR SUPRA-ORBITAl. TROCHLE AR OPTIC VIEW OF DEBIT FROM ABOVE. . The snpra-trochlear, the smaller of the two (fig. 20) runs obliquely inwards above the pulley of the superior oblique to the inner angle of the orbit. Here it gives off a 'small communication downwards to the LACHRYMAL GLAND. 53 infra-trochlear branch of the nasal, and then divides, after passing between the bone and the orbicularis palpebrarum, into filaments which supply the skin of the upper eyelid, forehead, and nose. One or two small filaments may be traced through the bone to the mucous mem- brane of the frontal sinuses. 1 b. The supra-orbital is the continuation of the frontal nerve, and runs forwards 011 the levator palpebrse to the supra-orbital notch, through which it ascends to supply the skin of the upper eyelid, fore- head, pericranium, and scalp. Its cutaneous branches, an inner and an outer, which run upwards beneath- the occipito-frontalis, have been described in the dissection of the scalp (p. 5). It supplies with common sensation the orbicularis palpebrarum, the occipito-frontalis, and the corrugator supercilii, where it joins the facial nerve. LACHRYMAL This is the smallest of the three branches of the NERVE. ophthalmic nerve. It runs along the upper border of the external rectus 011 the outer side of the orbit with the lachrymal artery, through the lachrymal gland, which it supplies as well as the upper eyelid. Its branches within the orbit are : 1, a branch which passes down behind the lachrymal gland to communi- cate with the orbital branch of the superior maxillary nerve ; 2. filaments to the lachrymal gland. It then pierces the palpebral ligament to supply the skin of the upper eyelid. FOURTH CRA- This nerve enters the orbit through the sphe- NIAL NERVE. noidal fissure above the other nerves. It runs along the inner side of the frontal nerve, and enters the upper or orbital surface of the superior oblique, to which it is solely distri- buted. This nerve is joined in the outer wall of the cavern- ous sinus by filaments from the sympathetic. It communicates occasionally with the lachrymal, and the ophthalmic division of the fifth. Here also it sends backwards two or more filaments to supply the tentorium cerebelli. LACHRYMAL This gland is situated below the external GLAND. angular process of the frontal bone. It is about the size and shape of an almond. Its upper surface is convex, in adaptation to the roof of the orbit ; its lower is concave, in adap- tation to the eyeball, and rests upon the external and superior 1 These filaments have been described by Blumenbach, De Sinibus Frontalibus. 54 MUSCLES OF THE ORBIT. FIG. 21. rectus. The anterior part of the gland lies sometimes separated from the rest, close to the back part of the upper eyelid, and is covered by the conjunctiva. The gland is invested by a capsule ' formed by the fascia of the orbit. The lachrymal gland consists of an aggregation of small lobes composed of smaller lobules, connected by fibro-cellular tissue, and resembles the structure of the sali- vary glands. The excretory ducts, seven to ten in number, run parallel, and perforate the conjunctiva in a row, about a quarter of an inch above the edge of the tarsal cartilage (fig. 21). They are not easily dis- covered in the human eye ; in that of the horse or bullock they are large enough to admit a small probe. The secretion of the gland keeps the surface of the cornea constantly moist and polished ; but if dust, or any foreign substance, irritate the eye, the tears flow in abundance, and wash it off. All the muscles of the orbit, with the exception of the inferior oblique, arise from the margin of the foramen opticum, and pass forwards, like ribands, to their insertions. LEVATOB This muscle arises from the roof of the orbit, PALPEBK^:. above and in front of the optic foramen. It gradually increases in breadth, and terminates in a broad, thin aponeurosis, which is inserted into the upper surface of the tarsal cartilage beneath the palpebral ligament. It is constantly in action when the eyes are open, in order to counteract the ten- dency of the lids to fall. As sleep approaches, the muscle relaxes, the eyes feel heavy, and the lids close. Its nerve comes from the superior division of the third nerve, and enters it on its under or ocular aspect. 1 This capsule, being a little stronger on the under surface of the gland, is described and figured by Sommerring as a distinct ligament, Icones Oculi Humani, tab. vii. MUSCLES OF THE ORBIT. 55 OBLIQUUS This muscle arises from the inner side of the SUPERIOR. optic foramen. It runs forwards along the inner and upper side of the orbit, and terminates in a round tendon, which passes through a fibro-cartilaginous pulley trochlea attached to the trochlear fossa in the frontal bone. From the pulley the tendon is reflected outwards and backwards, beneath the supe- rior rectus, and is inserted by an expanded tendon into the outer part of the sclerotic coat, midway between the cornea and the entrance of the optic nerve. The pulley is lined by a synovial membrane, which is continued over the tendon. The action of this muscle will be considered with that of the inferior oblique. It is supplied by the fourth nerve, which enters the back part of its upper surface. The frontal nerve and levator palpebrse are now to be cut through the middle and reflected, the front part forwards and the hind part backwards. On its under aspect is seen the twig from the upper division of the third nerve entering it. On reflecting this muscle the superior rectus is exposed. The superior rectus arises by a tendinous origin from the upper margin of the optic foramen and from the sheath of the optic nerve, and is inserted by a broad thin tendon into the sclerotic coat, about a quarter of an inch from the margin of the cornea (p. 61). Reflect this muscle by cutting through the DISSECTION. . middle, and, in doing so, observe a filament from the third nerve entering its under aspect. After the removal of a quantity of granular fat, the following objects are exposed : beneath the muscle are the optic nerve, the ophthalmic artery and vein, the nasal nerve and its ciliary branches crossing over the optic nerve, and further forwards is the reflected tendon of the superior oblique ; on the outer side of the optic nerve, and close to the ophthalmic artery, is the lenticular ganglion, with numerous ciliary filaments passing forwards from it to enter the sclerotic. The student should now trace backwards the two roots which enter the upper and lower angle respectively of the ganglion, the upper being its sensory branch from the nasal, the lower its motor root from the lower division of the third nerve. Further back should be traced the third, the nasal branch of the ophthalmic, and the 56 NASAL NERVE IN THE ORBIT. sixth nerves passing between the two heads of the external rectus to their respective destinations. The ophthalmic artery and its branches may also at this stage be exposed and cleaned. This is one of the three divisions of the oph- thalmic branch of the fifth, and is usually the first branch given off (fig. 19, p. 50). It enters the orbit through the sphenoidal fissure between the two origins of the external rectus, and between the two divisions of the third n. It then crosses obliquely over the optic nerve, beneath the levator palpebrse and the superior rectus, towards the inner wall of the orbit. After giving off the infra-trochlear branch, the nerve passes out of the orbit between the superior oblique and internal rectus, through the anterior ethmoidal foramen, into the cranium, where it lies beneath the dura mater, upon the cribriform plate of the ethmoid bone. It soon leaves the cranium through the nasal slit near the crista galli, and enters the nose. Here it divides into two branches an inner or septal, which supplies the mucous membrane of the front of the septum ; and an outer, the main continuation of the nerve which runs in a groove on the under surface of the nasal bone, and distributes branches to the pituitary membrane of the outer part of the nose and the two lower turbinated bones ; it also gives off a superficial branch, which emerges between the nasal bone and the cartilage, under the name of the naso-lobular, and is distributed to the skin of the tip and ala of the nose (p. 49). The nasal nerve gives off the following branches in the orbit : a. One slender filament to the lenticular yanylion (forming its upper or long root) is given off from the nasal nerve as it passes between the heads of the external rectus close to the optic nerve. It is about half an inch long, and enters the posterior- superior angle of the ganglion. b. Two or three long ciliary nerves. They run along the inner side of the optic nerve to the back of the globe of the eye. They are joined by filaments from the lenticular ganglion, and pass through the sclerotic coat to supply the iris (fig. 22). c. Infra-trochlear nerve. This runs forwards along the inner side of the orbit, below the pulley of the superior oblique, where it communi- cates with the supra-trochlear branch of the frontal nerve. It passes to the inner angle of the orbit, and divides into filaments, Avhich supply the OPHTHALMIC ARTERY. 57 skin of the eyelids, the caruncle, the lachrymal sac, and the side of the nose. FIG. 22. CILIARr GANGLION OPTIC NERVE. VIEW OF OPTIC AND LOWER NERVES OF ORBIT. This nerve, having passed through the optic foramen, proceeds forwards and a little outwards for about an inch to the globe of the eye, which it enters on the nasal side of its axis. It pierces the sclerotic and choroid coats, and then expands to form the retina. The nerve is invested by a dense fibrous coat derived from the dura mater, and by a thin one from the arachnoid, both of which pass forwards as far as the sclerotic. At the optic foramen it is surrounded by the tendinous origins of the recti ; in the rest of its course, by loose fat and by the ciliary nerves and arteries. It is pierced in its course through the orbit by the arteria centralis retinae which runs along with its vein in the middle of the nerve to the eyeball. 1 OPHTHALMIC This artery arises from the internal carotid, close ARTERY. by the anterior clinoid process. It enters the orbit through the optic foramen, outside and below the optic nerve ; occasionally through the sphenoidal fissure. Its course in the orbit is remarkably tortuous. Situated at first on the outer side of the optic nerve, it soon crosses over it, and runs along the inner 1 A small branch from Meckel's ganglion, ascending through the spheno-maxil- lary fissure, is described by Arnold as joining the optic nerve. 58 LACHRYMAL ARTERY. side of the orbit between the superior and internal recti, to inoscu- late with the internal angular artery (the terminal branch of the facial). Its branches arise in the following order : a. Lachrymal artery. This branch proceeds along the outer wall of the orbit above the external rectus, in company with the nerve of the same name to the lachrymal gland. After supplying the gland, it ter- minates in the conjunctiva and eyelids. In the orbit it gives off some malar branches which pierce the malar bone to get to the temporal fossa, and anastomose with the deep temporal arteries. It also sends a branch backwards through the sphenoidal fissure to anastomose with the arteria meiihigea media. b. Supra-orbital artery. This branch runs forwards with the frontal nerve under the roof of the orbit and upon the levator palpebrae. It emerges on the forehead through the supra-orbital foramen, where it communicates with the superficial temporal, frontal and angular arteries. c. Arteria centralis retina;. This small branch enters the optic nerve obliquely on the outer aspect close to the optic foramen. It runs in the centre of this nerve to the interior of the eye. d. Ciliary arteries. These branches may be arranged in three groups. The short ciliary, twelve to fifteen in number, proceed tor- tuously forwards with the optic nerve, and pierce the sclerotic coat at the back of the eye to supply the choroid coat and the iris. The long ciliary, two in number, run on each side of the optic nerve, enter the sclerotic, and pass horizontally forwards, one on each side of the globe, between the sclerotic and the choroid, nearly as far as the iris where each divides into an upper and a lower branch. These branches of the two long ciliary arteries anastomose with the anterior ciliary and form two vascular circles, an outer at the circumference of the iris, the circuit is major and an inner at the free margin of the iris, the circulus minor. The anterior ciliary are branches of the muscular and lachry- mal arteries and proceed with the tendons of the recti, and enter the front part of the sclerotic coat. In inflammation of the iris the vascular zone round the cornea arises from enlargement and congestion of the anterior ciliary arteries. e. JSthmoidal arteries. Of these arteries, two in number, the anterior and larger passes through the anterior ethmoidal foramen with the nasal nerve ; the posterior enters the posterior ethmoidal foramen with the spheno-ethmoiclal nerve. The anterior gives off brandies to the frontal and anterior ethmoidal cells, and a nasal branch to the nose ; it likewise gives off an anterior meningeal branch to the dura LENTICULAR GANGLION. 59 mater in the anterior fossa. The posterior is distributed to the pos- terior ethmoidal cells and upper part of the nose. f. Muscular branches. There is an upper and a lower branch sup- plying respectively the upper and lower muscles : besides these, there are irregular branches from the lachrymal and supra-orbital arteries. g. Palpebral arteries. These branches, a superior and an inferior, proceed from the ophthalmic artery near the front of the orbit. They are distributed to their respective eyelids, forming arches near the margins of the lids between the tarsal cartilages and the orbicularis palpebrarum with branches from the lachrymal and the infra-orbital arteries. h. Nasal artery. This branch may be considered one of the ter- minal divisions of the ophthalmic. It leaves the orbit on the nasal side of the eye above the tendon of the orbicularis, and inosculates with the angular and nasal arteries of the facial. It supplies the side of the nose and the lachrymal sac. i. Frontal artery. This is the other terminal branch of the oph- thalmic. It emerges at the inner angle of the eye, ascends, and inoscu- lates with the supra-orbital artery. OPHTHALMIC There are two ophthalmic veins. The superior VEINS. commences at the inner angle of. the eye by a communication with the frontal and angular veins. It runs back- wards above the optic nerve in a straighter course than the artery, receives the veins corresponding to the arteries of the upper and inner part of the orbit, and finally passes between the two heads of the external rectus, through the inner part of the spkenoidal fissure, to terminate in the cavernous sinus. The inferior ophthalmic vein is formed by the union of branches from the lower and outer part of the orbit, and proceeding backwards along the floor of the orbit, opens into the superior vein, or directly into the cavernous sinus. In front it sends a communicating vein through the spheno- maxillary fissure to join the pterygoid plexus. OPHTHALMIC OB Tnis sma11 ganglion ' (fig. 19, p. 50), of reddish LENTICDLAB colour and about the size of a pin's head, is situ- GANGLION. ated at tlie back of the orbit, between the optic nerve and the external rectus, on the outer side of, and usually 1 W. Marshall regards this ganglion, from its mode of development and from its relations in some of the lower vertebrates, to be connected more with the third nerve than the ophthalmic. 60 THIRD NERVE. closely adherent to, the ophthalmic artery. It is somewhat quadri- lateral in shape, and receives its sensory or long root from the nasal nerve, which joins its posterior superior angle ; its motor or short root, from the branch of the third nerve, going to the inferior oblique, which enters its posterior inferior angle ; and its sympa- thetic root from the cavernous plexus which joins it at its posterior border, or in conjunction with its sensory root. The ganglion, thus furnished with motor, sensory and sympathetic roots, gives off the short ciliary nerves. These, from eight to twelve in number, issue from the anterior upper and lower angles of the ganglion, usually four or five from the upper, the remainder from the lower. They run very tortuously with the optic nerve, pass through the back of the sclerotic coat, where they are joined by the long ciliary (from the nasal), and are distributed to the iris and the ciliary muscle. Since the ciliary nerves derive their motor influence from the third nerve, the iris must lose its power of contraction when this nerve is paralysed. THIRD NEBVE, The third nerve passes forwards in the outer MOTOR OCULI. wall of the cavernous sinus, and here receives one or two filaments from the cavernous plexus of the sympathetic. Just before it enters the inner end of the sphenoidal fissure it divides into two branches, both of which pass between the two heads of origin of .the external rectus, separated from each other by the nasal nerve. The upper and smaller division has been already traced into the superior rectus and levator palpebrae. The lower division after a short course divides into three branches, one passing inwards under the optic nerve to supply the internal rectus, another passes to the inferior rectus, and a third runs along the floor of the orbit to the inferior oblique (fig. 19). This last-named branch sends a small twig upwards to the lenticular ganglion, mentioned in the description of this ganglion, and another to the inferior rectus. What is the result of paralysis of the third nerve ? Falling of the upper eyelid (ptosis), external squint, dilatation and immobility of the pupil. SIXTH NERVE, This nerve lies in the inner wall of the cavernous ABDUCENS. sinus external to the internal carotid artery, passes RECTI MUSCLES. 61 through the sphenoidal fissure, and enters the orbit between the two heads of the external rectus. Here it lies below the lower division of the third and above the ophthalmic vein. The nerve terminates in fine filaments, which are distributed to the ocular surface of the external rectus. In the cavernous sinus it is joined by filaments from the carotid plexus, and in the orbit by a branch from Meckel's ganglion and from the ophthalmic nerve. Respecting the motor nerves in the orbit, observe that they all enter the ocular surface of the muscles, with the exception of the fourth, which enters the orbital surface of the superior oblique. The internal and inferior recti arise from a fibrous BECTI MUSCLES. , -, ,, 7 . ,,. , , , band the ligament oj Z/inn attached to the inner and lower borders of the optic foramen. The external rectus arises by two heads, the lower from the ligament of Zinn and the lower border of the sphenoidal fissure, the upper from the margin of the foramen opticum ; between these heads pass in the following order, from above downwards the upper division of the third, the nasal , the lower division of the third, the sixth nerves, and the ophthalmic vein. The four recti diverge from each other, one above, one below, and one on each side of the optic nerve. Their broad thin tendons are inserted into the sclerotic coat of the eye, about a quarter of an inch from the margin of the cornea (fig. 23). The recti muscles enable us to direct the eye towards different points ; hence the names given to them by Albinus attollens, depressor, adductor, and abductor oculi. It is obvious that by the single action of one, or the combined action of two, the eye can be turned towards any direction. The rectus superior as supplied by the upper division of the third nerve ; the rectus internus, the rectus inferior and obliquus inferior, by the lower division. The rectus externus is supplied by the sixth. Follow the recti to the eye, in order to see the tendons by which they are inserted. Notice also the anterior ciliary arteries, which run to the eye along the tendons. The congestion of these little vessels occasions the red zone round the cornea in iritis. It has G2 INSERTION OF THE RECTI MUSCLES. INSERTION OF THE EECTI MUSCLES WITH THE ANTERIOR CILIARY ARTERIES. been already mentioned that the tendons are invested by a fascia, which passes from one to the other, forming a loose tunic capsule FlG 23. f Tenon over the back of the eye. This tunic consists of two layers with an intermediate space, lined with flat cells, thus allow- ing free mobility of the globe. It is this fascia which resists the passage of the hook in the ope- ration for the cure of squinting. Even after the complete division of the tendon, the eye may still be held in its faulty position, if this tissue, instead of possessing its proper softness and pliancy, happen to have become contracted and un- yielding. Under such circumstances it is necessary to divide it freely with the scissors. By removing the conjunctival coat of the eye, the tendons of the recti are soon exposed. The breadth and the precise situation of their insertion deserve attention in reference to the operation for strabismus. The breadth of their insertion is about three- eighths of an inch, but the line of this insertion is not, at all points, equidistant from the cornea. The centre of the insertion is nearer to the cornea by about one line than either end. Taking the internal rectus, which has most frequently to be divided in strabis- mus, we find that the centre of its tendon is, upon an average, three lines only from the cornea, the lower part nearly five lines, and the upper four. It is, therefore, very possible that the lower part may be left undivided in the operation, being more in the background than the rest. The tendon of the internal rectus is nearer to the cornea than either of the others. INFERIOR This muscle arises by a flat tendon from the OBLIQUE. orbital plate of the superior maxilla on the outer side of the lachrymal groove. It runs outwards and backwards between the orbit and the inferior rectus, then curves upwards be- tween the globe and the external rectus, and is inserted by a broad DISSECTION OF THE NECK. 63 thin tendon into the outer and back part of the sclerotic, close to the tendon of the superior oblique. 1 It is supplied by the lower division of the third nerve. The tensor tarsi muscle has been described in the dissection of the face (p. 34). ORBITAL This is always very small, and is sometimes BRANCH OF THE absent. It comes from the trunk of the superior SUPERIOR MAXIL- maxillary in the spheno-maxillary fossa, enters the orbit through the spheno-maxillary fissure, and divides into two branches. Of these, one, the temporal, lies in a groove in the outer wall of the orbit, and after sending a small branch to the lachrymal nerve in the orbit, passes through a foramen in the malar bone to the temporal fossa. It then pierces the temporal aponeurosis an inch above the zygoma, and supplies the skin of the temple communicating with the facial, and join- ing frequently with the auriculo-temporal branch of the inferior maxillary. The other branch, the malar, passes along the outer part of the floor of the orbit, imbedded in fat, and makes its exit through a foramen in the malar tone, to supply the skin of the cheek over the malar bone (p. 49). DISSECTION OF THE NECK. SURFACE Before the student reflects the skin of the neck MARKING. he should examine the skin surface, which in some places is raised, in others depressed, indicating thereby unevenness of the subjacent structures. The neck is bounded above by a well- marked transverse ridge, indicating the lower border of the inferior maxilla, and at its lower part the neck is bounded by another ridge which corresponds with the clavicle. Crossing obliquely from the centre of the neck below to the mastoid process above, is the rounded prominence caused by the sterno-mastoid, and crossing this muscle diagonally from its anterior to its posterior border is the external jugular vein, which varies in size in different subjects. In front and behind the sterno-mastoid are two triangular depres- 1 On the action of the recti and oblique muscles, consult M. Foster, Text-Book of Physiology . 64 PLATYSMA MYOIDES. sions ; the posterior one, it will be seen, has its base at the clavicle, the anterior one at the lower jaw. The posterior triangle has the trapezius as its outer boundary, but this border is only well defined iiiferiorly, where the hollow becomes most marked, and takes the name of the supra-clavicular or Mohrenheiin's fossa. In this is placed deeply the subclavian artery, the posterior belly of the omo-hyoid, and the brachial plexus. In front of the sterno- mastoid is another triangular hollow space with its base upwards ; this is called the carotid triangle, for in it lies the carotid artery immediately beneath the anterior border of the sterno-mastoid. The body of the hyoid bone can always be felt in the middle line below the symphysis of the lower jaw. About a finger's breadth below the hyoid is the prominent pomum Adami of the thyroid cartilage, and a short distance below this cartilage is the cricoid, separated from the cartilage above by the crico-thyroid membrane. The cricoid cartilage corresponds with the fifth cervical vertebra, and from it the trachea passes down, gradually receding from the surface, so that there is, especially in emaciated subjects, a deep hollow fonticulus gutturis immediately above the sternum. In front of the second, third, and fourth rings of the trachea is the isthmus of the thyroid gland, and there are usually another four rings below these above the sternum, covered more or less by the depressor muscles of the os hyoides. The head must be slightly raised, and the face turned from the side on which the dissection is to be made. Then make a vertical incision through the skin, down the middle of the neck from the symphysis of the lower jaw to the sternum ; a second along the clavicle to the acromion ; a third along the base of the jaw as far as the mastoid process. Reflect the skin and subcutaneous fat, and expose the cutaneous muscle, called the platysma myoides. Between the platysma and the skin is a layer of adipose tissue, called the superficial fascia. It varies in thickness in different subjects, but is generally more abundant at the upper part of the neck, especially in corpulent individuals, in whom it occasions a double chin. PLATYSMA '^e l^citysma myoides is the thin cutaneous MYOIDES. muscle covering the front and side of the neck. DISSECTION OF THE NECK. 65 It arises from the subcutaneous tissue over the pectoralis major, trapezius and deltoid muscles ; l thence proceeding obliquely over the clavicle and the side of the neck, its fibres become more closely aggregated, and terminate thus : The anterior cross those of the opposite platysma, immediately below the symphysis of the jaw, and are lost in the skin of the chin ; the middle are attached along the base of the jaw ; the posterior cross the masseter muscle, and terminate, partly in the subcutaneous tissue of the cheek, partly in the muscles at the corner of the mouth blending with the depressor anguli oris and orbicularis. 2 The platysma forms a strong muscular defence for the neck. It is also a muscle of expression. 3 It is supplied with nerves by the cervical plexus, and by the cervical branch of the facial nerve. Cut through the platysma near the clavicle and turn it upwards. Beneath it lies the general in- vestment of the neck, called the deep cervical fascia. Upon this fascia we trace the superficial branches of the cervical plexus of nerves, the external jugular vein, and a smaller vein in front, called the anterior jugular. These superficial veins are so variable in size and course, that a general description only is applicable. 1 Some anatomists describe it as having a slender origin from the clavicle and the acromion. 2 Some of the uppermost fibres of this part of the platysma take the name of musculus risorius : this has been described among the muscles of the face. 3 If the entire muscle be permanently contracted it may occasion wry-neck, though distortion from such a cause is an exceedingly rare occurrence. A case in point is related by Mr. Gooch (Chirurg. Works), in which a complete cure was effected, after the failure of all ordinary means of relief, by the division of the platysma a little below the jaw. The platysma myoides belongs to a class of muscles called cutaneous, from their office of moving the skin. There are not many in man, except upon the neck and face, and there is a little one (palmaris brevis) in the palm of the hand. To understand their use thoroughly we must refer to the lower orders of animals, in whom they fulfil very important functions, by moving not only the skin, but also its appendages. For instance, by muscles of this kind the hedgehog, porcu- pine, and animals of that family can roll themselves up and erect their quills : we are all familiar with the broad ' panniculus carnosus ' on the sides of herbivorous quadrupeds, which enables them to twitch their skins, and thus rid themselves of insects. In birds, too, these cutaneous muscles are extremely numerous, each feather having appropriate muscles to move it. F 66 EXTERNAL JUGULAR VEIN. EXTERNAL The external jugular vein is formed within the JUGULAR VEIN. substance of the parotid gland by the junction of the temporal and internal maxillary veins. After receiving the transverse facial and posterior auricular veins, it appears at the lower border of the gland, crosses obliquely over the sterno-mastoid muscle (fig. 24), running along its posterior border, nearly as low down as the clavicle, where it pierces the deep cervical fascia and terminates in the subclavian vein. Accompanying the vein in its FIG. 24. Cervical branch of facial n. . . . Superficial cervical nerve .... External jugu- lar v Anterior jugu- lar v. Small occipital n. Auricularis magnus n. Nervus acces- sorius. Descending branch of cer- vical plexus. UIAGKAM OF THE SUPERFICIAL NERVES AND VEINS OF THE NECK. upper part is the auricularis magnus nerve, and crossing it, about the middle, is the superficial cervical nerve, both being branches of the superficial cervical plexus. It is usually provided with two pairs of valves the lower, imperfect, close to its termination in the subclavian vein ; the upper, placed about an inch and a half above the clavicle'. A line drawn from the angle of the jaw to the middle of the clavicle would indicate its course. To trace the vein, during life, press upon it just above the clavicle ; but do not be surprised if you fail to find it : it is sometimes wanting, and frequently very small. CUTANEOUS NERVES OF THE NECK. 67 Near the angle of the jaw the external jugular vein communi- cates by a large branch with the internal jugular, and about its middle it is joined by a large vein posterior external jugular from the occipital region. Before its termination the external jugular vein generally receives the supra-scapular, posterior scapular, and other unnamed veins : a disposition very embarrassing to the surgeon, because there is a confluence of veins immediately over the subclavian artery in the place where it is usually tied. ANTERIOR The anterior jugular vein is situated more in JUGULAR VEIN. the middle of the neck, and is much smaller than the external jugular. It commences by small branches below the chin, and runs down the front of the neck, nearly to the sternum ; it then curves outwards, beneath the sterno-mastoid muscle, and opens either into the external jugular or the subclavian vein. We commonly meet with two anterior jugular veins, one on either side ; immediately above the sternum they communicate by a transverse branch. The size of the anterior jugular vein is inversely proportionate to that of the external jugular. When the external jugular is small, or terminates in the internal jugular, then the anterior jugular becomes an important supplemental vein, and attains con- siderable size. It is not uncommon to find it a quarter of an inch in diameier, and we have seen it nearly half an inch. These varieties should be remembered in tracheotomy. Superficial lymphatic glands are sometimes found near the cutaneous veins of the neck. From four to six in number, they are small and escape observation unless enlarged by disease. One or two are situated over the sterno-mastoid muscle ; others, near the mesial line. CUTANEOUS The cutaneous nerves of the neck are the super- NERVES OF THE ficial branches of the cervical plexus : the plexus NECK - itself cannot at present be seen. It is formed by the communications of the anterior divisions of the four upper cer- vical nerves, and lies under the sterno-mastoid muscle, close to the transverse processes of the four upper cervical vertebrae, resting on the levator anguli scapulas and the scalenus medius. The super- F 2 C8 CUTANEOUS NERVES OF THE NECK. ficial branches of the plexus emerge from beneath the posterior border of the sterno-mastoid, and take different directions. They are named thus (fig. 24) : / . f Great auricular. Ascending branches . . . j gmall occipital> Superficial branches of J Transverse branch . . . Superficial cervical, the cervical plexus. I ( Sternal. Descending branches . . j Clavicular. V I Acromial. The great auricular n. comes from the second and third cervical nerves, winds round the posterior border of the sterno-mastoid, and ascends obliquely over that muscle, near the external jugular vein, towards the parotid gland. Near the gland it divides into two prin- cipal branches, of which the anterior or facial branches are distributed to the skin over the parotid gland, where they join branches from the facial nerve, and to the side of the cheek ; the posterior or auricular, after ascending a short distance, give off a branch, which ramifies mainly upon the cranial aspect of the cartilage of the ear ; and a smaller branch, the mastoid, which supplies the skin over the mastoid process. Other filaments of this nerve communicate in the substance of the parotid gland with branches of the facial nerve. The small occipital n. comes from the second cervical nerve, and is occasionally double. It ascends along the posterior border of the sterno-mastoid muscle to the occiput, where it supplies the back of the scalp, and communicates with the great occipital, the great auricular, and the posterior auricular nerves. It also sends off one branch, which is distributed to the skin of the temporal region, and another auricular to the pinna of the ear. Beneath the sterno-mastoid this nerve com- monly forms a loop, which embraces the nervus accessorius, and sends a branch to it. The superficial cervical n. comes from the second and third cervical nerves. It passes transversely forwards over the sterno-mastoid muscle, and supplies the front of the neck. Some of its filaments ascend towards the jaw, and join the cervical branch of the facial nerve ; other filaments descend and supply the skin in front of the neck as low as the sternum. The descending or supra-clavicular branches are derived from the third and fourth cervical nerves, and divide into three branches, which cross over the clavicle, and supply the skin of the front of the chest and shoulder. Of these, one, called the internal or sternal, supplies the skin DEEP CERVICAL FASCIA. 69 over the inner end of the clavicle and the upper part of the sternum ; another, the middle or claviciilar, passes over the middle of the clavicle, and is distributed to the skin over the pectoral muscle, the mammary gland, and the nipple ; the third, named external or acromial, crosses over the trapezius and acromion to supply the skin of the shoulder. Reviewing these cutaneous branches of the cervical plexus, we find that they have a very wide distribution, for they supply the skin covering the following parts viz., the ear, the back of the scalp, the side of the cheek, the parotid gland, the front and side of the neck, the upper and front part of the chest and shoulder. CERVICAL Look for this branch beneath the fascia near BRANCH OF THE the angle of the jaw (p. 66). It leaves the FACIAL NERVE. parotid gland, and, piercing the deep cervical fascia, divides into filaments which curve forwards below the jaw ; some of these, forming arches, join the superficial cervical branch of the cervical plexus ; others supply the platysma and skin. DEEP CERVICAL Now turn your attention to the membranous FASCIA. investment called the deep cervical fascia, which encloses the several structures of the neck. In some subjects the fascia is very thin ; in others, with strong muscles, it is proportion- ally dense and resisting. It is always stronger in particular situa- tions, for. the more effective protection of the parts beneath ; for instance, in front of the trachea, in the fossa above the clavicle, and below the angle of the jaw. It not only covers the soft parts of the neck collectively, but, by its inflections, forms separate sheaths for the muscles, vessels, and glands. It isolates them, and keeps them in their proper relative position. A lengthened de- scription of its numerous layers would be not only extremely tedious, but unintelligible, without considerable knowledge of the anatomy of the neck. We propose, therefore, to give only a gene- ral outline of the fascia, and of its principal layers, commencing from behind. Tracing it from behind, we find that the cervical fascia (some- times called deep cervical or muscular fascia of the neck) is attached to the ligamentum nuchas and to the spinous and transverse pro- cesses of the cervical vertebrae. From these attachments it passes forwards over the posterior triangle of the reck to the posterior 70 DEEP CERVICAL FASCIA. border of the sterno-mastoid, where it splits into two layers, super- ficial and deep, which invest that muscle and reunite at its an- terior border. The superficial layer passes towards the mesial line, where it becomes continuous with the corresponding fascia of the opposite side. The layer which lies in front of the sterno-mastoid is attached above to the base of the inferior maxilla, and passes over the parotid gland to the zygoma, to the mastoid process, and the superior curved line of the occipital bone. Traced downwards, we find it attached to the clavicle and to the upper border of the sternum. In the middle line it is closely connected to the hyoid bone, and below the thyroid body divides into two layers, one being attached to the front of the upper border of the sternum, the other to the back of the upper border of the same bone. Between these layers there is a well-marked interval, containing more or less fat, and one or two small lymphatic glands. This layer forms investing sheaths for the depressor muscles of the os hyoides and larynx. The deep layer viz., that which passes beneath the sterno- mastoid forms the common sheath. for the carotid artery, internal jugular vein, and the pneumogastric nerve, which lie behind this muscle ; the structures contained in the carotid sheath are separated from each other by delicate septa. The fascia is continued behind the pharynx (constituting the prcevertebral fascia) to join the fascia of the opposite side, w r hile another prolongation passes in front of the trachea beneath the sterno-thyroid muscle. Below, it is attached to the first rib, to which it binds down the intermediate tendon of the omo-hyoid ; and still further down it is continuous in the chest with the pericardium. It may also be traced under the clavicle along the axillary vessels and nerves into the axilla. Above, it is attached to the angle of the lower jaw, from which it extends backwards to the styloid process, and forms the sti/lo- maxillary ligament. Thence it is attached to the base of the skull, the petrous portion of the temporal bone, and the basilar process of the occipital bone. A correct knowledge of the attachments of the principal layers of the cervical fascia is essential to a right understanding of the course which pus takes when it forms in the neck. For instance, STERNO-CLEIDO-MASTOIDEUS. 71 suppose the pus to be formed at the lower part of the neck. If it be seated under the superficial layer (which is attached to the clavicle), it may burrow beneath the clavicle into the axilla. But if it be seated beneath the deep layer (which is attached to the first rib), then it becomes more serious, since the pus may travel through the loose tissue by the side of the pharynx, and make its way into the chest, where it may burrow down the anterior or the posterior mediastinum, and burst into the trachea or the oesophagus. Besides forming sheaths for the several structures of the neck, there are other purposes to which the cervical fascia is subservient. The firm attachment of its layers to the sternum, the first rib, and the clavicle, forms a fibrous barrier at the upper opening of the chest, which supports the soft parts, and prevents their yielding to the pressure of the atmosphere during inspiration. Dr. Allan Burns 1 first pointed out this important function of the cervical fascia, and has recorded a case exemplifying the results of its destruction by disease. Moreover, the great veins at the root of the neck, namely, the internal jugular, subclavian, and innominate, are so closely united by the cervical fascia to the adjacent bones and muscles, that when divided they gape. They are, as the French express it, ' canalisees,' and are therefore better able to resist the pressure of the atmosphere, which tends to render them flaccid and impervious during inspira- tion. But this anatomical disposition of the great veins makes them more liable to the entrance of air when wounded. Instances of death have been recorded, resulting from the sudden entrance of air into the veins during operations about the neck, or even the axilla. STEKNO-CLEIDO- The sterno-cleido-mastoideus is the large muscle MASTOIDEUS. which passes obliquely across the neck. It arises by a rounded tendon from the upper part of the sternum, and by fleshy fibres from the sternal third of the clavicle. It is inserted by a thick tendon into the external surface of the mastoid process, and by a thin aponeurosis into about the outer half of the superior curved ridge of the occipital bone. The sternal origin of the muscle is at first separated from the 1 Surgical Anatomy of the Head and Neck. 72 TRIANGLES OF THE NECK. clavicular by a slight interval ; subsequently the sternal fibres gradually overlap the clavicular. The muscle is confined by its strong sheath of fascia, in such a manner that it forms a slight curve, with the convexity forwards. Observe especially that its front border overlaps the common carotid artery; along this border we make the incision in the operation of tying the vessel. ACTION OF When both sterno-mastoids act simultaneously STERNO-MASTOID. they draw the head and neck forwards and down- wards, and are therefore especially concerned in raising the head from the recumbent position. When one sterno-mastoid acts singly, it turns the head obliquely towards the opposite shoulder ; in this action it co-operates with the splenius of the other side. 1 On emergency, the sterno-mastoid acts as a muscle of inspiration, by raising the sternum ; its fixed point being, in this case, at the head. The sterno-mastoid is supplied by three nutrient arteries an upper, a middle, and a lower. The upper sterno-mastoid artery, a branch of the occipital, enters the muscle with the n. accessorius, close to the mastoid process of the temporal bone ; the middle mastoid is a branch of the superior thyroid, and enters the under surface of the muscle, crossing over the common carotid on a level with the thyroid cartilage ; the lower mastoid is a branch of the supra-scapular, and supplies the clavicular portion of the muscle, close to its origin. The sterno-mastoid is supplied with nerves by the n. accessorius, and by branches from the deep cervical plexus : these branches come from the second and sometimes the third cervical nerves. TBIANGLES OF Anatomists avail themselves of the oblique THE NECK. direction of the sterno-mastoid muscle to divide the neck on each side into two great triangles, an anterior and a posterior (fig. 25). The base of the anterior triangle is formed by the jaw, its sides by the mesial line and the front border of the sterno-mastoid. The posterior has the clavicle for the base, while 1 The single action of the muscle is well seen when it becomes rigid and causes a wry-neck. Other means of relief failing, the division of the muscle near its origin is sometimes beneficial in curing the distortion. In deciding as to the pro- priety of this operation, we should be careful to examine the condition of the other muscles, lest, after having divided the sterno-mastoid, we should be disappointed in removing the deformity. CONTENTS OF THE POSTEKIOR TRIANGLE. 73 the sides are defined by the hind border of the sterno-mastoid, and the front border of the trapezius. The omo-hyoid muscle, which crosses the neck under the sterno-mastoid, subdivides these primary triangles into four smaller ones (fig. 25) of unequal size : an anterior superior, an anterior in- ferior, a posterior superior, and a posterior inferior. The direction FIG. 25. N. accessorius . . Digastricus . . . Os hyoides . . . Omo-hyoideus . . Sterno-mastoid muscle drawn aside. Splenius capitis. Levator anguli sca- pulae. Scalenus medius. Scalenus anticus. DIAGRAM OF TRIANGLES OF THE NECK. 1. Superior carotid triangle. 2. Inferior 3. Occipital triangle. 4. Supra-clavicular triangle. 5. Snbmaxillary triangle. of the omo-hyoid muscle renders their boundaries at once obvious. CONTENTS OF The fat and connective tissue must now be care- POSTERIOR fully removed from the posterior triangle. The TRIANGLE. following muscles will be seen forming its floor : viz., beginning from above, the splenius capitis, the levator anguli scapulae, the scalenus medius and posticus, and a small portion of the serratus magnus. The posterior belly of the omo-hyoid crosses this triangle about an inch above the clavicle, and subdivides it into two unequal parts an upper or occipital, and a lower or supra- clavicular. In the occipital triangle, the larger of the two, besides 74 NERVUS ACCESSORIUS. the muscles just mentioned (with the exception of the serratus magnus), are found the descending branches of the cervical plexus ; and, passing obliquely downwards from beneath the sterno-mastoid is the spinal accessory nerve, which enters the under part of the trapezius. Curving round the posterior border of the sterno- mastoid, and becoming superficial, are the ascending and transverse branches of the superficial cervical plexus. The transversalis colli (posterior scapular) artery and vein, and its branch the superficialis colli (which chiefly supplies the trapezius), cross transversely out- wards the lower part of the space. A chain of lymphatic glands is also found along the posterior border of the sterno-mastoid. NERVUS The upper part of the sterno-mastoid is traversed ACCESSOKIUS. obliquely by a large nerve called the spinal acces- sory or n. accessorius. This nerve the eleventh cranial consists of two parts : one, the accessory, arises from the side of the medulla oblongata below the pneumogastric nerve; the other, the s.pinal part, arises from the cervical portion of the spinal cord by a series of filaments from the lateral tract as low down as the sixth cervical vertebra. The spinal portion ascends between the ligamentum denticulatum and the posterior roots of the spinal nerves, through the foramen magnum into the skull. Within the cranium the two parts unite and form a single nerve, which leaves the skull through the foramen jugulare. Here the accessor// portion is connected with the ganglion of the root of the pneumogastric by several filaments ; and lower down it again joins the pneumogastric at the ganglion of the trunk, below which the two nerves become blended. The accessory and spinal portions communicate in the foramen jugulare. Below the foramen the spinal part runs behind the internal jugular vein, the digastric and stylo-hyoid muscles, and then pierces obliquely the upper third of the sterno-mastoid. Emerging beneath its outer border, it crosses the posterior triangle of the neck to the under surface of the trapezius, to which it is distributed. The nervus accessorius supplies also the sterno- mastoid in its passage through it, and here it joins some branches from the third cervical. After leaving the muscle it is joined by branches from the second and third cervical nerves. Beneath the trapezius it forms a plexus with the third and fourth cervical SUPRA-CLAVICULAR TRIANGLE. 75 nerves. The upper mastoid artery, a branch of the occipital, enters the sterno-mastoid with the nerve. SUPRA-CLAVICU- The supra-clavicular or subclavian triangle is IAR TRIANGLE, bounded below by the clavicle, in front by the outer border of the sterno-niastoid, and above by the posterior belly of the omo-hyoid muscle. The area of the triangle thus formed will vary in proportion to the obliquity of the omo-hyoid muscle, and the extent to which the sterno-mastoid and trapezius are attached to the clavicle. The depth of the vessels and nerves contained in this space depends, not only upon the degree to which the clavicle arches forwards, but varies with the elevation and depression of the shoulder. The descending branches of the cervical plexus, together with some fat, should now be cut through and turned aside, when a layer of a fascia which binds down the omo-hyoid muscle to the clavicle will be exposed. Beneath this is a deeper layer of fascia, which covers the subclavian vessels and brachial plexus of nerves, and descends with them under the clavicle into the axilla. Between these two layers we meet with more or less fat and connective tissue and lymphatic glands continuous with those in the axilla. It will be easily understood how a collection of pus in the axilla may ascend in front of the vessels and point above the clavicle, or, vice versa, how matter formed in the neck may travel under the clavicle and point in the axilla. Near the posterior border of the sterno-mastoid muscle the external jugular vein passes through both layers of the deep fascia, and terminates in the subclavian ; but before its termination it is commonly joined by the supra-scapular, the posterior scapular, and other unnamed veins proceeding from the surrounding muscles ; so that there is in this situation a confluence of veins, which, when large or distended, is exceedingly embarrassing. The fascia and the glands should be removed, and the following objects carefully dissected. Behind and nearly parallel with the clavicle is the supra-scapular (transversalis humeri) artery, a branch of the thyroid axis. A little higher is the transversalis colli, or posterior scapular (commonly a branch of the thyroid axis), which crosses the lower part of the neck towards the posterior superior 76 ANTERIOR TRIANGLE. angle of the scapula. Both these arteries are very irregular in respect to their origin, the last particularly being often given off from the subclavian in the third part of its course. Search for the outer border of the scalenus anticus, which descends from the transverse processes of the cervical vertebree to the first rib : run- ning down longitudinally upon it may be seen the phrenic nerve. The subclavian vein lies upon the first rib in front of the insertion of the anterior scalene muscle behind the clavicle, so that it is not usually seen in this triangle. The subclavian artery rises up into- the neck as high as an inch above the clavicle, and sometimes on the right side as high as an inch and a half. It appears higher than the vein, emerging beneath the outer border of the scalenus anticus, and care must be taken to preserve the small branch from the brachial plexus, which crosses the artery and proceeds to the subclavius muscle. The large nerves constituting the brachial plexus come out between the scalenus anticus and medius, higher than the subclavian artery, and on a plane posterior to that vessel. These different objects will be described in detail hereafter. DISSECTION OF T ne anterior triangle must now be dissected. THE ANTERIOR In doing so, notice, before the deep cervical fascia TRIANGLE. \^ removed, the arching forwards of the anterior border of the sterno-mastoid muscle, which is connected to the lower jaw by the fascia, so that the common carotid artery is concealed from view before the parts are disturbed. The anterior triangle is bounded behind by the anterior border of the sterno- mastoid, in front by the middle line of the neck, and above by the lower border of the inferior maxilla. Covering the triangle are the superficial and deep cervical fascias, and the platysma ; passing across it are the superficial cervical n., the infra-maxillary branch of the facial nerve ; and descending in front is the anterior jugular vein. This space is subdivided by the anterior belly of the omo- hyoid into a superior and an inferior carotid triangle, and above them is a third triangle mapped out by the converging bellies of the digastric muscle arid* the lower jaw, and is called the sub- maxillary or digastric triangle (fig. 25, p. 73). The inferior carotid triangle is bounded above and below by the omo-hyoid and sterno-mastoid muscles, and in front by the STERNO-HYOID MUSCLE. 77 middle line. The muscles forming its floor are the sterno-hyoid and sterno-thyroid muscles, and lying on them is the anterior jugular vein; in the middle line is the thyroid body covering the trachea. 1 The superior carotid triangle has for its boundaries the sterno- mastoid, the omo-hyoid, and the posterior belly of the digastricus. Its muscular floor is formed by the hyo-glossus, the middle and inferior pharyngeal constrictors, and the thyro-hyoid. In this space are found the bifurcation of the common carotid into its external and internal divisions, and the following branches of the external carotid the superior thyroid, lingual, facial, the occipital, and the ascending pharyngeal .arteries their accompanying veins and the internal jugular vein. The nerves seen are the hypoglossal, crossing over the external carotid, the infra-maxillary branch of the facial, the spinal accessory, the superior and external laryngeal nerves, and in front of the carotid sheath is the descendens noni. The digastric triangle will be described subsequently (p. 91). Now examine the flat muscles in front of the neck, which pull down the larynx and os hyoides namely, the sterno-hyoid, sterno- thyroid, omo-hyoid, and thyro-hyoid. 2 Remove the fascia which covers them, disturbing them as little as possible, and take care of the nerves (branches of the descendens noni), which enter their outer borders. The sterno-hyoid arises from the back part of STEENO-HYOID. , , . , . . ,. the sternum and posterior sterno-clavicular liga- ment, from the clavicle and occasionally from the cartilage of the first rib, and is inserted into the lower border of the body of the os hyoides. This is the most superficial of the muscles in front of the neck. We cut in the mesial line between these muscles in laryngotomy. STEKNO- The sterno-thyroid arises from the back part of THYROID. the sternum, below and internal to the origin of 1 The vessels and nerves lying within and upon the carotid sheath are not seen, as they are situated beneath the anterior border of the sterno-mastoid . * The sterno-hyoid and sterno-thyroid muscles often present slight transverse tendinous lines. These tendinous intersections are quite rudimentary in man ; but in some animals with long necks, e.g. the giraffe, they are so developed that each depressor muscle is composed of alternations of muscle and tendon. 78 CENTRAL LINE OF THE NECK. the sterno-hyoid, and the cartilage of the first rib, and is inserted into the oblique ridge on the ala of the thyroid cartilage. This muscle is situated immediately under, and is much broader than, the sterno-hyoid. FIG. 26. Digastricus. Occipital a. . Hypoglossal 11 . Descender) s noni n. . . 2nd cervical n. Superior thy- roid a. . . 3rd cervical n. Communicans noni n. . . Crico- thyroid m Internal jugu- lar v. . . Common caro- tid a. . . Cricoid cartilage. Isthmus of thyroid gland. Trachea. Inferior thyroid v. CENTRAL LINE OF NECK. COUKSE AND RELATIONS OF COMMON CAROTID ABTEBY. The two sterno-hyoid muscles converge as they ascend to their insertions, and opposite the cricoid cartilage and the two or three tipper rings of the trachea they are in contact with one another. DEPRESSOR MUSCLES OF THE LARYNX. 79 The sterno-thyroid, however, diverge to their insertions, but are in contact below, the result of which is that the trachea is completely covered in front by muscular fibres. The omo-hyoid consists of two fleshy portions OMO-HYOID. .,, , T . ,, connected by a tendon. It arises from the upper border of the scapula, and sometimes from the ligament over the notch, and is inserted into the lower border of the body of the os hyoides just external to the sterno-hyoid. From the scapula it comes nearly horizontally forwards across the lower part of the neck, and passes beneath the sterno-mastoid, over the sheath of the great vessels of the neck on a level with the cricoid cartilage; then, changing its direction, it ascends nearly vertically close to the outer border of the sterno-hyoid. Thus the muscle does not proceed straight from origin to insertion, but forms an obtuse angle beneath the sterno-mastoid muscle. The intermediate tendon is situated at the angle and is bound down to the first rib and the sternum by a process of the deep cervical fascia. The object of this peculiar direction of the omo-hyoid appears to be to keep tense that part of the cervical fascia which covers the apex of the pleura, and thus to resist atmospheric pressure. EELATIONS OF At its origin the omo-hyoid is covered by the THE OMO-HYOID. trapezius, then by the clavicle and subclavius, and lastly, by the sterno-mastoid and platysma myoides. It lies on the scalenus medius and anticus, the brachial plexus, the phrenic nerve, then on the internal jugular vein, pneumogastric nerve and common carotid artery enclosed within their common sheath, on the descen- dens noni, the sterno-thyroid, and thyro-hyoid muscles. These depressor muscles are all supplied with nerves (fig. 26, p. 78) by the descendens noni (a branch of the twelfth or hypo- glossal), and by the communicantes noni (branches of the second and third cervical nerves). The descendens noni sends a separate branch to each belly of the omo-hyoid. They are supplied with blood by the superior and inferior thyroid arteries. The thyro-hyoid arises from the oblique line on THYKO-HYOID. ., , .;,, _:, . -, ,., -. , , the ala of the thyroid cartilage, and runs up to be inserted into the lower border of the body and the inner half of the great cornu of the Kyoid bone. This muscle is a continuation of 80 PARTS BENEATH THE STERNO-MASTOID. the ster no-thyroid. It is supplied by a special branch of the hypo- glossal nerve which enters the muscle close by its posterior border, in company with the hyoid branch of the lingual artery. In front of the muscle, are the omo-hyoid and sterno-hyoid muscles, and it covers the thyro-hyoid membrane, the thyroid cartilage, and the superior laryngeal vessels and nerve as they enter the larynx. ACTION OF THE The sterno-hyoid, sterno-thyroid, omo-hyoid, DEPKESSOB and thyro-hyoid muscles co-operate in fixing the MUSCLES. larynx and os hyoides, e.g., in sucking, or they depress the larynx after it has been raised in deglutition. Again, they depress it in the utterance of low notes. That the larynx is raised or depressed, according to the height of the note, may be ascertained by placing the finger on it while singing through an octave. The omo-hyoid, in addition, is a tensor of the cervical fascia, and draws down the hyoid bone to its own side. The thyro- hyoid depresses the hyoid bone, or elevates the thyroid cartilage, according as the one or the other is the fixed point. The sterno-mastoid muscle must now be cut transversely through the middle, and the two ends turned upwards and downwards, so that they may be replaced if necessary. This done, notice the strong layer of fascia which lies under the muscle and forms part of its sheath. It is attached to the angle of the jaw, thence descends over the large vessels of the neck, and is firmly connected to the clavicle and first rib. This fascia prevents matter coming to the surface, when suppuration takes place by the side of the pharynx. Remove the fascia, and clean the various structures beneath the sterno-mastoid, taking care not to cut away the descendeiis noni and communicantes noni nerves, which lie in front of the sheath of the common carotid. Dissect out the lymphatic glands which lie along the sheath of the large vessels. PAKTS EXPOSED The objects exposed to view, when the muscle is BENEATH THE reflected, are very numerous. Among these the STEKNO-MASTOID. mO re important are : the sterno-clavicular articu- lation, the splenius capitis and colli, the posterior belly of the di- gastricus, the levator anguli scapulae, scalenus medius and anticus, omo-hyoid, sterno-hyoid, and sterno-thyroid muscles ; the occipital COMMON CAROTID ARTERY. 81 artery, the common carotid artery and its division, the internal jugular vein, the subclavian artery and the branches of the first part of its course, the cervical plexus, and the lower cervical nerves which form the brachial plexus ; the phrenic, pneumogastric, hypoglossal, and spinal accessory nerves, the descendens and com- municantes noni nerves ; the subclavian vein and its tributaries ; and lastly, a small part of the parotid gland, and the three sterno- mastoid arteries. On the left side, in addition, we find the thoracic duct ; on the right side, the right lymphatic duct. COURSE AND RELA- The common carotid artery is now exposed in TIONS OF THE the whole extent of its course in the neck. It COMMON CABOTID. arises, on the right side from the arteria innomi- nata, behind the upper part of the right sterno-clavicular articula- tion ; on the left, from the arch of the aorta. It ascends in front of the bodies of the cervical vertebrae, by the side of the trachea, thyroid gland, and larynx, as high as the upper border of the thyroid cartilage, and then divides into the external and internal carotids. Thus, a line drawn from the sternal end of the clavicle to a point midway between the mastoid process and the angle of the jaw, will nearly indicate its course. It is contained in a sheath of the deep cervical fascia, together with the internal jugular vein and the pneumogastric nerve. The vein lies on the outer side of, and parallel with, the' artery ; the nerve lies behind and between the artery and the vein. The structures contained within this sheath are separated from each other by a thin septum of fascia, so that each has a separate investment. Owing to the increasing breadth of the larynx, the two common carotid arteries, which at their origin lie near together, are separated by a wide interval at their point of division. At the lower part of the neck the carotid artery is deeply placed, but as it ascends it becomes more superficial, although it has the appearance of being deeply situated owing to the promi- nence of the thyroid cartilage. In front the artery is covered by the skin, superficial fascia, platysma myoides, deep fascia, the sternal portion of the sterno-mastoid, the sterno-hyoid, and thyroid muscles, and, on a level with the cricoid cartilage, it is crossed by the omo-hyoid. Above this point the artery becomes more super- G 82 RELATIONS OF THE COMMON CAROTID ARTERY. ficial, and is covered by the integument, platysma, the cervical fasciae, the middle sterno-mastoid artery, and only slightly over- lapped by the sterno-mastoid. Lying upon the sheath of the artery, we find the descendens noni joined by the communi- cantes noni nerves. The sheath is crossed by the facial, the superior, and middle thyroid veins, and lower down by the anterior jugular vein, all of which empty themselves into the internal jugular. This is the general rule, and especial attention should be directed to it, because the veins are liable to be overlooked and injured in the operation of tying the carotid. To the inner side of the artery we find the trachea, the thyroid body, the recurrent laryngeal nerve, the inferior thyroid artery, the external laryngeal nerve, the inferior constrictor of the pharynx, and the larynx. On the outer side are the pneumogastric nerve and the internal jugu- lar vein. Behind the artery are the sympathetic nerve, the inferior thyroid artery, the recurrent laryngeal nerve; and lastly, the carotid sheath lies successively upon the longus colli and the rectus capitis anticus major muscles. 1 The common carotid may be ligatured either above or below the omo-hyoid. It is most accessible above the point where this muscle crosses ; and therefore, if the surgeon has his choice, he would prefer to tie the vessel in this situation. In the higher operation we make an incision,' three inches in length, along the inner border of the sterno-mastoid, the centre of the incision being opposite the cricoid cartilage : we cut through the skin, superficial fascia, platysma, deep cervical fascia, when we come to the anterior border of the sterno-mastoid. The overlapping edge of this muscle 1 It is important that we should be aware that the common carotids vary occa- sionally in their origin. Thus the right may arise in common with the left carotid, or the right may arise separately from the arch of the aorta, in which case the right subclavian is usually transposed. The left may be given off from the in- nominate artery of the right side, or it may arise in common with the left subclavian, and thus form a left innominate. In transposition of the aorta there is a left innominate, which is given off first, the right carotid and the right subclavian arising as separate branches from the arch. The place of division of the common carotid is subject to considerable variation : it may divide higher or lower than usual, the former being the more frequent. Rarely there has been no common carotid artery, the external and internal arising as separate branches from the arch of the aorta. LEFT COMMON CAROTID ARTERY. 83 must be drawn outwards, and the muscle at the same time relaxed by turning the head to the same side. The sheath of the vessel is then exposed, and a small opening is to be made on its inner side large enough to admit the aneurism needle, which should be passed round the artery on its outer side, so as to avoid wounding the in- ternal jugular vein. The vessel is then to be ligatured, care being taken not to separate more of the sheath than is necessary from the artery, and not to include in the ligature the pneumogastric or descendens noni nerves. After ligation of the artery, the collateral circulation is main- tained by the following vessels : between the branches of the external and internal carotid arteries of the opposite side with the corresponding branches of the ligatured side ; between the verte- bral and the posterior communicating of the same side ; between the inferior and superior thyroids of the same side ; between the profunda cervicis and the princeps cervicis of the occipital of the same side. TxT T In the first part of its course the left carotid J.N WMAJ. .KHi- * SPECTS THE LEFT differs from the right in the following particulars : CAROTID DIFFEBS 1. It arises from the arch of the aorta, is there- FBOM THE BIGHT. fore longer and Deeper seated than the right, and is covered by the first bone of the sternum. 2. It is crossed by the left brachio-cephalic vein. 3. It is in close relation with the oesophagus and the trachea. 4. It is in close relation with the left recurrent laryngeal nerve. 5. It is in close relation posteriorly with the thoracic duct. 6. It is covered by the thymus gland in early life. The artery has in front the sternum, the sterno-hyoid and sterno-thyroid muscles, the left innominate vein, and the remains of the thymus gland; to the left side it has the left subclavian artery and the left pneumogastric nerve ; to the right side the arteria innominata ; and behind, the trachea, oesophagus, and thoracic duct. The common carotid as a rule gives off no branch in its course ; bat, occasionally, the middle sterno-mastoid, the superior thyroid, or, more rarely, the vertebral, arise from it prior to its division. G 2 84 INTERNAL JUGULAR VEIN. At its bifurcation it usually presents a slight bulbous enlargement., which is sometimes so marked that it might be mistaken for an incipient aneurism. It is necessary to know that the carotid sometimes divides as low as the level of the cricoid cartilage, and that not infrequently the division takes place as high as the hyoid bone. INTERNAL The internal jugular vein is the continuation of JUGULAR VEIN. the lateral sinus, and returns the blood from the brain. Leaving the skull through the foramen jugulare, it receives the inferior petrosal sinus, and at the junction it presents a slight enlargement, the sinus. The vein descends on the outer side of the internal carotid, and subsequently the common carotid arteries, in the same sheath, and joins the subclavian vein at a right angle to form the brachio-cephalic or innominate vein. In its course down the neck it receives the pharyngeal, occipital, facial, lingual, superior, and middle thyroid veins. Previous to their terminations the internal jugular veins incline somewhat to the right side to meet the corresponding subclavian veins ; thus, on the right side, there is a triangular interval between the artery and vein in which is seen the pneumogastric nerve and vertebral artery ; on the left side the vein slightly overlaps the artery, thus rendering ligature of the left carotid more difficult than of the right. The internal jugular veins moreover advance slightly to meet the subclavian veins, so that they lie on a plane a little anterior to their accompanying arteries. A little before their termination the internal jugulars have a double valve. DESCENDBNS ^ ie d' escen d ens noni (p. 92), a branch of the NONI AND COM- hypoglossal, runs down obliquely over the sheath MUNICANTES NONI o f the carotid to supply the depressor muscles of the os hyoides. Trace the nerve upwards to see that it leaves the hypoglossul where this nerve curves round the occipital artery. For a short distance the descendens noni lies within the carotid sheath ; but, about the level of the os hyoides, it comes through the sheath, and crosses obliquely over the carotid, from the outer to the inner side. The descendens noni is reinforced by one or more nerves termed communicantes noni, derived from the second and third cervical nerves. These com- THYROID BODY. 85 raunicating branches descend on the outer side of the internal jugular vein, and form generally two loops in front of the carotid sheath, constituting a triangular plexus called the ' ansa liypo- ylossi.' From these loops the nerves proceed to the anterior and posterior bellies of the omo-hyoid, to the sterno-hyoid, and sterno- thyroid muscles. A small branch may sometimes be traced pro- ceeding from the descendeiis noni into the chest to join the cardiac and phrenic nerves. In some subjects the descendens noni seems to be wanting, in which case it will probably be concealed within the carotid sheath : when this happens the reinforcing loops from the cervical nerves will be found behind the internal jugular vein. 1 The thyroid body should now be examined. DlSSFCTION To expose it, reflect the sterno-hyoid and thyroid muscles from their insertions, so that they can be replaced if neces- sary. Next observe the lymphatic glands of the neck, and lastly survey the objects in the central line of the neck, from the jaw to the sternum. This very vascular gland-like body lies over the front and sides of the upper part of the trachea, and extends upwards on each side of the larynx. It consists of two lateral lobes, connected a little below the cricoid cartilage by a transverse portion called the isthmus, and weighs from one to two ounces. Each lobe is conical, about two inches in length, and an inch and a quarter in breadth. Its base is opposite the fifth or sixth ring of the trachea, and the apex by the side of the thyroid cartilage. Its anterior surface is convex, and is covered by the sterno-hyoid, sterno-thyroid, and omo-hyoid muscles; its deep surface concave embraces the sides of the trachea and larynx, and usually extends so far backwards as to be in contact with the pharynx. Its external border overlaps, in most cases partially, but sometimes completely, the common carotid artery, 1 By many anatomists the descendens noni is regarded as the combination of filaments from the hypoglossal and pneumogastric nerves ; by some, it is looked upon as a branch of the pneumogastric ; and lastly, which is most probable, it is considered by others to be mainly derived from a branch which is sent to the hypoglossal from the first and second cervical nerves. 86 THYROID BODY. particularly on the right side ; and there are instances in which the lobe is deeply grooved by the vessel. The isthmus lies over the second and third rings of the trachea. This portion of the organ varies much in its dimensions. In some instances there is no transverse portion. This corresponds with . the normal disposition in most of the lower orders of mammalia ; but in man, it is a failure in the union of the two halves by which the organ is originally developed. 1 Generally, the vertical measurement is about half an inch. Between its upper border and the cricoid cartilage is a space about one-third of an inch in extent, where the trachea is free ; this space, therefore, is the more preferable situation for tracheotomy. But the vertical measure- ment of this isthmus is sometimes of very considerable length, so that it has been seen covering the trachea almost down to the sternum. 2 The thyroid body is closely connected, by areolar tissue, to the sides of the trachea, to the cricoid and thyroid cartilages. Hence it rises and falls with the larynx in deglutition. The thyroid varies in size in different individuals and at dif- ferent periods of life. It is relatively larger in the child than the adult, in the female than the male. In old age it diminishes in size, becomes firmer, and occasionally contains earthy matter. 3 By far the most notable considerations in respect to the thyroid 1 Concerning the development of the lateral halves and central portion of the thyroid body, see a paper by Callender in the Proceedings of tJie Royal Society, 1867. 2 From the upper part of the isthmus, or from the adjacent border of either lobe, most commonly the left, a conical prolongation of the thyroid body, called the pyramid, frequently ascends in front of the crico-thyroid membrane, as high as the pomum Adami, and is attached to the body of the os hyoides by fibrous tissue. In some subjects we may observe a few muscular fibres passing from the os hyoides to the pyramid. This constitutes the levator glandules thyroidece (see preparation in Museum of St. Earth. Hosp., Patholog. Series, No. 14) of some anatomists. There are instances in which the pyramid is double ; and, lastly, we have seen a considerable portion of this thyroid substance lying over the crico- thyroid membrane, completely isolated from the rest of the organ. These varieties deserve notice, because any one portion of this structure may become enlarged independently of the rest, and occasion a bronchocele. 3 The thyroid body is, primarily, developed as a pouch from the anterior wall of the pharynx ; the lateral lobes are first formed, and are subsequently united by the isthmus. W. Muller, Jenaisch. Zeitsch. 1871. THYROID BODY. 87 body are the number, the large size, and the free inosculations of its arteries. The superior thyroid arteries come from the external carotid and enter the front surface of the apex of each lobe ; the inferior thyroid come from the subclavian, and enter the under sur- face of the base. An artery, called the middle thyroid (thyroidea ima), is observed in some subjects ; it is given off from the arteria innominata, or the arch of the aorta, and ascends directly in front of the trachea to the isthmus. Its veins are equally large, and form a plexus upon it. The superior and middle thyroid veins cross the common carotid, and open into the internal jugular. The inferior thyroid veins, two in number, descend over the front of the trachea, communicate freely with each other, and terminate in the left brachio-cephalic vein. When you perform tracheotomy, bear in mind the size of these inferior thyroid veins, and the possible existence of a middle thyroid artery. Its nerves are furnished by the middle and inferior cervical ganglia of the sympathetic. They accompany the arteries. The lymphatics of the thyroid body are both numerous and large. They form a dense network on the surface, and pass into the connective tissue of the gland, and eventually ' enclose the primary lobes in complete rings or more or less perfect arches.' On the right side they open into the right lymphatic duct, on the left side into the thoracic duct. STRUCTURE OF The thyroid body belongs to the class of duct- THE THYROID less glands, since no excretory duct has been dis- BoDV - covered. It is invested by a thin covering of dense areolar tissue, which connects it with the surrounding struc- tures and also penetrates it, imperfectly dividing it into lobes and supporting the vessels as they enter it. It consists of a multitude of closed vesicles, which are imbedded in a delicate reticulum. The cells vary in size, from -^-"o inch to that of a pin's head, and do not communicate with each other. In hypertrophy of the gland we sometimes see them as large as a horse-bean, or even larger. The vesicles are oval and are lined by a single layer of endothelial columnar cells containing a glairy yellow fluid, in which are found a large number of nuclei, nucleated cells, and not infrequently 88 DEEP CERVICAL GLANDS. red blood-cells in various stages of disintegration and decolorisa- tion. 1 The blood-vessels pass into the connective tissue surround- ing the vesicles, and form a dense capillary plexus, which comes into close relation with the vesicular epithelium cells, and with the endothelium of the lymph-spaces ; from these lymph-spaces, which are placed between the vesicles, the lymphatics have their com- mencement. The function of the gland is probably that of disin- tegration of the red blood-cells, and of the conveyance into the general lymphatic system of the products of these degenerative changes. An enlargement of the thyroid body is termed a ' bronchocele.' If the relation of its lobes to the trachea and oesophagus be pro- perly understood, it is easy to predicate the consequences which may result from their enlargement. The nature and severity of the symptoms will to a certain extent be determined by the part of the organ affected. An enlargement of the left lobe is more likely to produce a difficulty in swallowing, on account of the in- clination of the oesophagus towards the left side. If the isthmus be enlarged, difficulty in breathing will probably be the prominent symptom, and, in order to remove this danger, the isthmus has been divided, and in part removed. An instance is related by Allan Burns in which the isthmus was placed between the trachea and the oesophagus. It must be obvious that enlargement of a part so situated would occasion great difficulty in swallowing. I have seen two cases in which the lateral lobes projected so far inwards that they completely embraced the back of the oesophagus. Small lymphatic glands are observed about the thyroid body, especially in front of the trachea ; one is often situated over the crico-thyroid membrane. These glands, if enlarged by disease, might be mistaken for a small bronchocele. DEEP CERVICAL I n the connective tissue which surrounds the LYMPHATIC great vessels of the neck, we meet with a series GLANDS. o f ly m p na ti c glands, called the deep cervical. They form an uninterrupted chain (whence their name glandulce 1 Baber, ' Eesearches on the Minute Structure of the Thyroid Gland,' Philos. Trans. 1881. DEEP CERVICAL GLANDS. 89 concatenates), from the baSe of tlie skull, along the side of the neck, to the clavicle, beneath which they are continuous with the thoracic and the axillary glands. Some of these glands lie anterior to the common carotid artery ; others, between it and the spine. This disposition explains the well-known fact, that, when these glands are enlarged, the great vessels and nerves of the neck are liable to become imbedded in their substance. The glands are particularly numerous near the division of the common carotid, by the side of the pharynx, and the posterior belly of the digastricus. The lymphatics connected with them come from all parts of the head and neck. These vessels unite, to form, on both sides of the neck, one or more absorbent trunks, called the jugular. On the left side this jugular trunk joins the thoracic duct, or opens by a separate orifice into the junction of the left internal jugular and subclavian veins : on the right side it opens into the right lymphatic duct, a short trunk about half an inch in length, which terminates at the angle of the junction of the right internal jugular and subclavian veins. The terminations of the thoracic duct and the right lymphatic duct are guarded by two small semilunar valves, in order to prevent regurgitation of blood back from the veins. The contiguity of the glands to the great vessels and nerves of the neck explains the symptoms produced by their enlargement. The tumour may be so situated as to be raised and depressed by the pulsation of the carotid, and thus simulate an aneurism. A careful examination, however, will distinguish between an inher- ent and a communicated pulsation. By grasping the tumour we become sensible that the pulsation does not depend upon any variation of its magnitude, but upon the impulse derived from the artery ; consequently, if the tumour be lifted from the vessel, all feeling of pulsation ceases. SURVEY OF THE The parts in the central line of the neck should CENTKAL LINE OF now be well studied (fig. 26, p. 78). Beginning THE NECK. a f-^e chj^ we observe the insertions of the di- gastric muscles. Below these is the junction, or raphe, of the mylo-hyoid muscles. Then comes the os hyoides. Below the os hyoides is the thyro-hyoid membrane, attached above to the 90 CENTRAL LINE OF THE NECK. posterior and upper border of the hyoid bone, and below to the thyroid cartilage. Next is the pomum Adami, or projection of the thyroid cartilage, which is apparent between the contiguous borders of the sterno-hyoidei. Below the thyroid cartilage is the cricoid. These two cartilages are connected by the crico-thyroid membrane, across which runs the crico-thyroid artery to join its fellow. Below the cricoid cartilage is the trachea. This is crossed by the isthmus of the thyroid body, and lower down it recedes from the surface, covered by the inferior thyroid veins. Now the chief surgical interest lies just above, and just below, the cricoid cartilage. This cartilage can be felt very plainly in the living subject at any age, no matter how fat. In laryngotomy, the crico-thyroid membrane is divided transversely. The mem- brane should be divided close to the edge of the cricoid c., for two reasons : 1. In order to be farther from the vocal cords. 2. To avoid the crico-thyroid artery which crosses the middle of the membrane. If more room be required, the cricoid cartilage should be divided longitudinally. In tracheotomy, the trachea may be opened by a perpendicular incision, above the isthmus of the thyroid body, or below it. The operation above the isthmus, if there be space enough for the in- troduction of the tube, is the easier and safer of the two ; for here the trachea is nearer to the surface, and no large blood-vessels are, generally speaking, in the way. The space available measures from a quarter to half an inch ; and the isthmus is not so firmly adherent to the trachea as to prevent its being drawn downwards for a short distance. However, it is right to state that, in one case out of every eight or ten, there is no available space. Tracheotomy below the isthmus is neither an easy nor a safe operation, for many reasons : 1 . The trachea recedes from the surface as it descends, so that just above the sternum it is nearly an inch and a half from the skin. 2. The large inferior thyroid veins are in the way. 3. A middle thyroid artery may run up in front of the trachea, direct from the arteria innominata. 4. The arteria innominata itself lies sometimes upon the trachea higher than usual, and ma,y, therefore, be in danger. 5. The left brachio- cephalic vein in some cases crosses the trachea above the edge of DIGASTRIC TRIANGLE. 91 the sternum instead of below it. The celebrated French surgeon Beclard used to relate in his lectures the following occurrence : A student had fallen into the Seine, and was nearly drowned. As he was recovering very gradually, some kind friends attempted to accelerate the process by making an opening into the trachea. In so doing they wounded the brachio-cephalic vein. Blood poured into the trachea, and the result was instantly fatal. Whoever pays attention to this subject in the dissecting-room will soon be convinced of the fact that, not only large veins, but large arteries, occasionally cross the crico-thyroid membrane as well as the trachea, thus showing the necessity of cutting cautiously . down to, and fairly exposing, the air tube before we venture to open it. It is preferable, after making the first incision through the skin, to lay aside the sharp knife and to use a blunt one, so that the tissues may be torn rather than cut ; by this proceeding the liability to haemorrhage is materially lessened. When the platysma and the cervical fascia have DISSECTION OF . THE SUBMAXILLAEY k een removed from their attachment to the jaw, EEGION OB THE the most conspicuous object is the submaxillary gland. Observe that the fascia is here very strong, and forms for the gland a complete capsule. Be- neath the jaw are several lymphatic glands, from six to ten in number, of which some lie superficial to the salivary gland, others beneath it. These glands receive the lymphatics of the face, the tonsils and the tongue. A little dissection will expose a muscle called the digastricus, consisting of two distinct fleshy portions connected by a tendon. They form, with the body of the jaw, a triangle called the digastric, of which we propose to examine the contents. The muscles form- ing its floor are the mylo-hyoideus and hyo-glossus. Under the submaxillary gland is the facial artery, which here runs a tortuous course, and finally turns up over the lower jaw in front of the masseter muscle. Lying on the mylo-hyoideus, under cover of the lower jaw, is the submental artery, accompanied by the mylo-hyoid nerve and artery. Behind the submaxillary gland, and separating it from the parotid, which also is contained within this triangle, is the stylo-maxillary ligament. Ascending and then entering the 92 DIGASTRICUS. parotid is the external carotid artery, in front of which is the infra-maxillary branch of the facial nerve. Deep in this space are situated the internal jugular vein, the internal carotid artery, and the pneumogastric nerve; and running obliquely forwards between the internal and external carotid arteries are the stylo-glossus, FIG. 27. Facial a. Mylo-hyoid n. Submcntal a. Occipital a. . . . Hypoglossal n Descendens noni n. Lingual a Internal jugular v. Superior thyroid a. . Common carotid a. DIGASTRIC TRIANGLE AND CONTENTS. DlGASTRICUS. stylo-pharyngeus, glosso-pharyngeal nerve, and the stylo-hyoid ligament. The dif/astricm consists of two muscular bellies united by an intermediate tendon. The posterior belly arises from the digastric fossa of the temporal bone, passes obliquely downwards^ forwards, and inwards, and then ascends to be inserted by its anterior belly close to the symphysis of the lower DIGASTRIC TRIANGLE. 93 jaw. Raise the submaxillary gland to see the intermediate tendon of the digastricus piercing the stylo-hyoid muscle, the angle which it forms, and how it is fastened by aponeurosis to the body and the greater cornu of the os hyoides. Observe also that this aponeurosis supra-liyoid aponeurosis is connected in the mesial line with its fellow of the opposite side, so that a fibrous expan- sion occupies the interval between the anterior portions of the digastrici. The chief action of the digastricus is to depress the lower jaw. But if the lower jaw be fixed, then the muscle raises the os hyoides, as in deglutition. The posterior belly of the digastricus is supplied by a nerve from the facial; the anterior belly by a branch from the mylo- hyoidean nerve (which comes from the third division of the fifth pair). STYLO- The stylo-hyoideus arises from the middle of HYOIDEUS. the styloid process of the temporal bone, and pass- ing downwards and forwards is inserted into the body of the os hyoides. This muscle at first runs above the posterior belly of the digastricus, and near its insertion is pierced by the digastric tendon. Its nerve is derived from the facial close to its exit from the stylo-mastoid foramen, in common with the branch to the pos- terior belly of the digastricus. 1 Its action is to raise and draw back the os hyoides. The digastric triangle is bounded above by the horizontal ramus of the lower jaw, and mastoid process of the temporal bone ; behind by the posterior belly of the digastricus ; and in front by the ante- rior belly. The objects to be examined in this triangle are twelve in number, as follow 1. Submaxillary salivary gland. 7. Stylo-maxillary ligament. 2. Facial vein. 8. Part of the parotid gland. 3. Facial artery. 9. Part of the external carotid artery. 4. Submental artery. 10. Mylo-hyoideus muscle. 5. Mylo-hyoidean nerve. 11. Hypcglossal nerve. 6. Submaxillary lymphatic glands. 12. Part of the hyo-glossus muscle. 1 In many, if not in most subjects, a small filament from the hypoglossal nerve is distributed to this muscle. 94 FACIAL VEIN. SUBMAXILLARY In the ordinary position of the head, the sub- SALIVARY GLAND. maxillary gland is partially concealed by the jaw, but when the head falls back the gland is more exposed. It is about the size of a chestnut, weighs about two drachms, and is divided into several lobes. Its upper margin is covered by the body of the jaw ; its lower margin overlaps the side of the os hyoides. Its cutaneous surface is flat, being covered only by the skin, platysma, and deep cervical fascia ; but the lobes on its deep surface are irregular, and often continuous with those of the sub- lingual gland. By raising the gland we find that it lies upon the mylo-hyoideus, the hyo-glossus, the stylo-glossus, the tendon of the digastricus, and a portion of the hypoglossal nerve, seen above the tendon. Part of the gland passes beneath the posterior border of the mylo-hyoid, and not infrequently becomes continuous with the sublingual gland. The facial artery lies in a groove on its deeper surface, and subsequently upon its upper border ; and it is separated from the parotid gland, which is situated behind it, by the stylo-maxillary ligament. Mark these relations well, because they are of importance, as will be presently explained in tying the lingual artery. The duct of the gland cannot at this stage of the dissection be traced further, for it runs forwards, under cover of the mylo- hyoideus, to end in the floor of the mouth, by the side of the frgenum linguae. The description of its course and relations had better therefore be deferred till it can be dissected in its whole length with the gustatory nerve in the pterygoid region. _, The facial vein does not accompany the facial artery, but runs nearly a straight course. It leaves the face at the anterior edge of the masseter m., then runs over the submaxillary gland, the digastricus and stylo-hyoideus and the carotid artery, to join the internal jugular. This is the rule but there are frequent exceptions. Before it empties itself into the internal jugular it is joined by a large branch from the external jugular vein. The principal point to remember is, that the vein runs superficial to the gland, and that we must be cautious in opening abscesses under the jaw. EXTERNAL CAROTID ARTERY. 95 COURSE AND course an d relations of the external carotid EELATIONS OF THE artery, and its branches in the neck, should now EXTERNAL CAROTID be made out as far as the parotid gland. In pre- ARTERY. paring a view of them, observe that nearly all the veins lie in front of their corresponding arteries. In removing the connective tissue, fat and lymphatic glands, the student must take care of the nerves and other structures which are liable to be injured. The external carotid arises from the common carotid about the level of the upper border of the thyroid cartilage. It ascends to the interval between the ear and the jaw in a slightly curved direction, at first forwards and then backwards. The external and the internal carotids are in the adult nearly of equal size ; but the external rapidly diminishes in size, owing to the large branches it gives off within a short distance. At first it lies beneath the skin, superficial fascia, platysma myoides, deep cervical fascia, some of the superficial cer- vical nerves, and the sterno-mastoid muscle. It is next crossed by the hypoglossal nerve, the facial and lingual veins, the posterior belly of the digastricus and stylo-hyoideus ; it then enters the parotid gland, where it lies beneath the facial nerve and the external jugular vein, and terminates between the external audi- tory meatus and the neck of the jaw, by dividing into the temporal and internal maxillary arteries. Internally the artery is in relation with the hyoid bone, the pharynx, the parotid gland, and the posterior border of the ascending ramus of the lower jaw. Behind the external carotid, and separating it from the in- ternal, are the stylo-glossus, the stylo-pharyngeus, the glosso- pharyngeal nerve, and the stylo-hyoid ligament. The superior laryngeal nerve and part of the parotid gland are also placed behind the artery. Notice the relative position which the external and internal carotids bear to each other. The external lies at first on the same plane with, but nearer to the side of the pharynx than the internal. It soon, however, changes its position, and crosses obliquely in front of the internal to reach the space between the angle of the jaw and the mastoid process. The internal carotid <)G SUPERIOR THYROID ARTERY. ascends perpendicularly by the side of the pharynx to the base of the skull. The external carotid gives off the following branches 1. The superior thyroid. 5. The posterior auricular. 2. The lingual. 6. The internal maxillary. 3. The facial. 7. The temporal. 4. The occipital. 8. The ascending pharyngeal. SUPERIOR The superior thyroid, the first branch of the THYKOID AKTEKY. external carotid, arises just below the great cornu of the os hyoides. It lies in the superior carotid triangle, and, curving downwards and inwards, runs beneath the omo-hyoid, sterno-hyoid, and sterno-thyroid muscles to the upper and front surface of the thyroid body, in which it terminates. Its branches are the four following : 1. The hyoid, a small muscular branch, runs horizontally inwards below the greater cornu of the os hyoides, and anastomoses with its fellow. 2. The siqjerior laryngeal branch, accompanied by the superior laryngeal nerve, runs inwards beneath the thyro-hyoid muscle, pierces the thyro-hyoid membrane (sometimes the thyroid cartilage), supplies the muscles and the mucous membrane of the larynx, and anastomoses with its fellow of the opposite side. 3. The middle sterno-mastoid, a small branch, variable as to origin, descends over the sheath of the common carotid artery, and enters the under aspect of the sterno-mastoid muscle. 4. The crico-thyroid, an artery of great interest in reference to the operation of laryngotomy, crosses the crico-thyroid membrane, and com- municates with a corresponding branch on the opposite side (fig. 26, p. 78). One or two small branches pass through the membrane to the interior of the larynx. It is important to know that the crico-thyroid artery often varies in direction and size. In most cases it is small, and runs across the centre of the membrane ; we should therefore be least likely to wound it in laryngotomy, by dividing the membrane close to the cricoid cartilage. But it is by no means infrequent to find this artery of considerable size, taking an oblique or even a perpendicular direction in front of the membrane, and finally distributed to one of the lobes of the thyroid body. We have seen several instances in which the membrane was crossed by .the main trunk of the superior thyroid. BRANCHES OF THE EXTERNAL, CAROTID. These facts should establish the practical rule in laryngotomy, not to make an opening into the larynx until it has been fairly exposed. FIG. 28. POST. ANT. / TEMPORAL! ASAL SUP. CORONARY A.FR/ENUM CRICO-THYR01D MIDDLE STERNC-MASTOID DIAGRAM OF THE BRANCHES OF THE EXTERNAL CAROTID ARTERY AND THEIR BRANCHES. Among the many arterial inosculations about the thyroid body are two which deserve notice : the one is formed between the two superior thyroid arteries along the upper border of the isthmus ; H 98 FACIAL ARTERY. the other takes place along the back part of the lateral lobe between the superior and inferior thyroid arteries of the same side. The superior thyroid vein leaves the upper part of the thyroid body, crosses over the common carotid artery, and joins the internal jugular or the facial vein. SUPERIOR LARYK- The superior laryngeal nerve, mentioned as ac- GEAL NERVE. companying the superior laryngeal artery, is given off from the inferior ganglion of the pneumogastric nerve. It descends by the side of the pharynx, behind both carotid arteries, and divides into two branches the internal and external laryngeal nerves. The internal branch enters the larynx through the thyro- hyoid membrane accompanied by the superior laryngeal artery, and supplies the mucous membrane of the larynx with its exquisite sensibility. Some of its branches may be traced upwards in the ary-epiglottidean fold to supply the epiglottis and the base of the tongue ; others descend to the rima glottidis ; a large branch passes down behind the ala of the thyroid cartilage to join the recurrent laryngeal nerve ; and a small branch pierces the arytenoideus to supply the mucous membrane beneath it. The external branch, descending beneath the depressors of the larynx, accompanies the crico-thyroid artery, and after distributing filaments to the pharyn- geal plexus, supplies the thyroid body, the inferior constrictor, and the crico-thyroid muscles. It receives a branch from the superior cervical ganglion of the sympathetic, and sends off a cardiac fila- ment to join the superior cardiac branch of the sympathetic behind the common carotid artery. LINGUAL The lingual artery and its branches will be de- ARTEBY. scribed in the dissection of the submaxillary region. The facial artery is the third branch of the external carotid. It runs tortuously under the hypoglossal nerve, the posterior belly of the digastricus and stylo- hyoideus, and beneath or through the substance of the submaxillary gland to the face, where it appears at the anterior border of the masseter. Below the jaw the facial rests on the mylo-hyoideus, and gives off the four following branches : 1. The ascending or inferior palatine artery runs up between the stylo-glossus and the stylo-pharyngeus m., and behind the internal MYLO-HYOIDEUS. 99 pterygoid m. to the pharynx, to which and the neighbouring parts it gives branches. Ascending as far as the levator palati, it divides into two branches : one courses along the tensor palati to supply the soft palate ; the other enters the tonsil, and anastomoses with the descending palatine of the internal maxillary, and with the tonsillar branches of the ascending pharyngeal. 2. The tonsillar runs up between the internal pterygoid and the stylo-glossus m. ; then, perforating the superior constrictor, it supplies the tonsil and root of the tongue. 3. Glandular branches to the submaxillary gland and side of tongue. 4. The submental arises from the facial behind the submaxillary gland, and runs forwards upon the mylo-hyoideus, beneath the inferior maxilla, distributing branches in its course to the gland and the adjacent muscles. It then curves over the bone and divides into two branches : a superficial one, which supplies the skin and lip ; and a deep one, which runs between the muscles and the bone, and inosculates with the mental and inferior labial arteries. Beneath the inferior maxilla it usually inosculates with the sublingual artery. The remaining branches of the external carotid artery will be described later on. MYLO-HYOIDEAN Look for the mylo-hyoidean nerve near the sub- NEBVE. mental artery. The nerve comes from the inferior dental (before its entrance into the dental foramen), and running along a groove on the inner side of the inferior maxilla, advances between the bone and the internal pterygoid m., to supply the mylo-hyoideus and the anterior belly of the digastricus. SUBMAXILLABY The submaxillary lymphatic glands receive the LYMPHATIC lymphatics of the face and the tongue. They are GLANDS. often enlarged in cancerous diseases of the tongue or the lower lip. It should be remembered also that there are lymphatic glands in the mesial line below the chin. MYLO- The mylo-hyoideus, a triangular muscle, arises HYOIDEUS. from the mylo-hyoid ridge of the lower jaw, from the symphysis, as far back as the last molar tooth. Its posterior fibres are inserted into the body of the os hyoides, the anterior being attached to a median tendinous line, termed the raplie, Thus the muscles of opposite , yiotef-s 1 ferfn^ja, mu'soiijaf fiber for the mouth. Superficially, it is in relation* with the 1 anterior belly of 100 STYLO-MAXILLARY LIGAMENT. the digastricus, the submaxillary gland, the submental artery, and the mylo-hyoidean n. By its deep surface, it is in relation with part of the hyo-glossus, the stylo-glossus, the genio-hyoideus, Wharton's duct, the gustatory and hypoglossal nerves- with their communications, and the sublingual gland. It is supplied with nerves by the mylo-hyoid branch of the inferior dental ; with blood by the submental artery. The muscles of opposite sides conjointly elevate the os hyoides and the floor of the mouth as in degluti- tion. STYLO -MAXIL- This is a layer of the deep cervical fascia, ex- IABY LIGAMENT. tending from the angle of the jaw to the styloid process. It is a broad sheet of fascia, and separates the submax- illary gland from the parotid. It is continuous with the fascia covering the pharynx ; this gives it a surgical interest, because it prevents accumulations of matter formed near the tonsils and upper part of the pharynx from coming to the surface. The remaining objects seen in the submaxillary triangle namely, the parotid gland, the hypoglossal nerve, the hyo-glossus muscle will be described presently when they can be better seen. Your attention should now be directed to a piece of surgical ana- tomy, which will enable you readily to find and tie the lingual artery. It is this : A curved incision, about two inches in length, being made from the lesser cornu along the upper border of the great cornu of the os hyoides, through the skin, the platysma, and the cervical fascia, you will come upon the lower edge of the submaxillary gland. Lift up the gland, which is easily done, and underneath it you will observe that the tendon of the digastricus makes two sides of a triangle, of which the base is formed by the hypoglossal nerve crossing the hyo-glossus muscle. Within this little triangle, cut transversely through the fibres of the hyo-glossus : under them is the lingual artery, lying on the middle constrictor. The first time you perform this operation on the dead subject, you will not un- likely miss the artery and cut through the middle constrictor into the pharynx. j /. **The!3fa*cial Wsels.'niuSt now be divided imme- * t % * c * * ^ 1 ' diately ibelow the *jaW. * 'Reflect the anterior belly of thfe /dvga^tiou^ vfi*(5,m ils/insetijigii|;"43tach the mylo-hyoideus HYO-GLOSSUS. 101 from the middle line and the os hyoides, and turn it over the body of the jaw, taking care not to injure the muscles and structures beneath. The lower jaw must now be sawn through, a little to the dissector's side of the symphysis, and the bone drawn upwards by hooks. The tongue should then be drawn out of the mouth, and fastened by hooks. The os hyoides should be drawn down by means of hooks, so as to put the parts on the stretch. All this done, we have to make out, by carefully cleaning away the fat and connective tissue, the following objects represented in fig. 29, p. 102 1. Genio-hyoideus. (5. Sublingual gland. 2. Hyo-glossus. 7. Hypoglossal nerve. 3. Stylo-glossus. 8. Gustatory nerve. 4. Genio-hyo-glossus. 9. Submaxillary ganglion. 5. Submaxillary duct. 10. Lingual artery. GENIO- The genio-hyoideus arises from the inferior HYOIDEOS. tubercle .behind the symphysis of the jaw, and passes downwards and backwards to be inserted into the front of the body of the os hyoides. This round muscle is situated in the mesial line, parallel to its fellow. Its nerve comes from the hypoglossal, and its blood from the lingual artery. Its action is to draw the os hyoides forwards and upwards ; and if the hyoid bone be fixed, it depresses the lower jaw. The hyo-glossus arises from the body, the HYO-GLOSSUS. -, , , , ., , greater and lesser cornua of the os hyoides, and is inserted into the posterior two-thirds of the side of the tongue, its fibres blending with the stylo-glossus and palato-glossus. It is a square and flat muscle, and its fibres ascend nearly perpen- dicularly from origin to insertion. The fibres arising from the body of the hyoid bone, termed the l>asio-ylossus, are directed backwards and upwards and overlap the fibres which have their origin from the greater cornu and are termed the Tcerato-glossus . Those that arise from the lesser cornu are termed the chondro- (flossus. The nerve to the hyo-glossus comes from the hypo- glossal, and its blood from the lingual. Its action (with that of its fellow) is to depress the tongue. Observe the objects which lie upon the hyo-glossus ; namely, the hypoglossal and gustatory nerves (which at the anterior border form one or more loops of communication with one another), the chorda tympani nerve, the 102 GENIO-HYO-GLOSSUS. submaxillary ganglion, the submaxillary gland and its duct, the hyoid branch of lingual artery, the lingual vein, the sublingual gland, the digastricus, stylo-hyoid, stylo-glossus, and mylo-hyoid muscles. Beneath the hyo-glossus muscle lie the lingual artery and vein, part of the middle constrictor of the pharynx, part of the genio-hyo-glossus, the lingualis and the glosso-pharyngeal nerve. GENIO- The genio-hyo-glossus arises by a tendon from HYO-GLOSSUS. the upper tubercle behind the symphysis of the FIG. 29. Styloid process . . Glosso-pharyngeal n. Hypoglossal n. Occipital a. . Snbmaxillary gan- glion Duct of submaxillary gland. Middle constrictor m, Lingual a. .... Descendens noni n. . _ Chorda tympani n. \\ Gustatory n. MUSCLES, VESSELS, AND NERVES OF THE TONGUE. lower jaw, and is inserted as follows : the lower fibres into the body of the os hyoides ; the upper fibres into the tongue from the base to the apex. It is the largest and most important of the muscles of the tongue. It is fan-shaped, with the apex attached to the symphysis ; thence its fibres radiate into the entire length of the tongue. Externally, the muscle is in relation with the stylo- glossus, lingualis, and hyo-glossus, the lingual artery, the sub- HYPOGLOSSAL NERVE. 103 lingual gland, Wharton's duct, the hypoglossal and gustatory nerves ; inferiorly, by its lower border it is in contact with the genio-hyoid ; above, by its anterior border with the mucous mem- brane of the mouth ; and internally, it is in contact with its fellow and the fibrous septum of the tongue. It derives its nerves from the hypoglossal, and its blood from the lingual artery. Its action is various. The posterior fibres, by raising the os hyoides and drawing forwards the base of the tongue, protrude the tongue out of the mouth ; the anterior draw the tongue back again. When every part of the muscle acts, it draws down the whole tongue, and is therefore one of the chief muscles concerned in suction. The stylo-glossus, a long and slender muscle, STYLO-GLOSSUS. . " ., arises from the outer side or the styloid process near its apex and from the stylo-maxillary ligament; its fibres pass downwards and forwards, and then nearly horizontal, and are inserted along the side of the tongue. It runs outside the hyo- glossus nearly to the tip of the tongue, and blends with the fibres of this muscle, as well as with the palato-glossus. Its nerve comes from the hypoglossal. Its action is to retract the tongue. HYPOGLOSSAL The hypoglossal, or twelfth cranial nerve, is the NERVE. motor nerve of the muscles of the tongue. It arises by several filaments, twelve to fifteen, from the front of the medulla oblongata between the anterior pyramid and the olivary body. It pierces the. dura mater in two fasciculi which leave the skull through the anterior condylar foramen ; these subsequently blend to form a single nerve trunk. It lies deeply beneath the internal jugular vein and internal carotid artery, where it is intimately connected with the lower ganglion of the pneumo- gastric nerve ; it then comes up between the artery and vein, and, immediately below the posterior belly of the digastricus, curves forwards over the occipital, the internal and external carotid and facial, arteries. Next it crosses the hyo-glossus muscle, and pass- ing beneath the mylo-hyoid, divides into branches which supply the following muscles ; namely, the stylo-glossus, hyo-glossus, genio-hyo-glossus, lingualis, and the genio-hyoideus. As it curves round the occipital artery, the hypoglossal nerve sends the descendens noni to the depressors of the os hyoides (p. 102). 104 - LINGUAL NERVE. It also sends a nerve to the thyro-hyoideus, which proceeds from it where it crosses over the external carotid, accompanied by the hyoid branch of the lingual artery. Near the anterior border of the hyo-glossus, it communicates by several loops with the gusta- tory nerve. (Fig. 29.) The hypoglossal at its origin is purely a motor nerve. But after leaving the skull, it receives communications from the first two cervical nerves. These communications are important physio- logically for two reasons : 1 . They account for the hypoglossal nerve containing sensory fibres. 2. They contribute the greater part of the filaments of the descendens noni. It is also connected by small branches with the pneumogastric nerve and the superior cervical ganglion of the sympathetic at the base of the skull. SUBLINGOAL The suHingual gland lies immediately beneath GiiiND. the mucous membrane of the floor of the mouth. Its shape is oblong, with the long axis (about an inch and a half) directed from before backwards, and it weighs about a drachm. Its relations are as follows : above, it is covered with mucous membrane ; beloiv, it rests upon the upper surface of the naylo- hyoid muscle ; internally, it is in contact with the hyo-glossus, genio-hyo-glossus, stylo-glossus, the gustatory nerve and Wharton's duct ; posteriorly, with the submaxillary gland ; and in front, it rests in a depression behind the symphysis of the lower jaw. The ducts of the sublingual gland (ducts of Kivinus ! ) vary in number from eight to twenty. They terminate by minute openings behind the orifice of the submaxillary duct, along the ridge felt upon the floor of the mouth. One or more ducts terminate in the submax- illary duct : one of these takes the name of the duct of Bartholin. The duct of the submaxillary gland may now be traced across the hyo-glossus, and under the gustatory nerve to the floor of the mouth. LINGUAL OB This nerve is a branch of the inferior maxillary GUSTATOB* NEEVE. O r third division of the fifth pair of cranial nerves. Emerging beneath the external pterygoid muscle, in company with, but in front of, the inferior dental nerve, it rests upon the internal pterygoid muscle. It descends between this latter muscle 1 Aug. Quirin. Eivinus, De Dyspepsia, Lips., 1678. LINGUAL ARTERY. 105 and the ramus of the lower jaw, and curves forwards towards the side of the tongue over the superior constrictor of the pharynx, along the. upper part of the hyo-glossus, at the anterior border of which it crosses, superficially, the duct of the submaxillary gland (fig. 29). Having reached the under part of the tongue, the nerve divides into numerous branches which pierce the muscular struc- ture of the tongue, and then break up into filaments which supply the mucous membrane and the fungiform and filiform papillae on its anterior three-fourths. Beneath the external pterygoid it is joined at an acute angle by the chorda tympani, a branch of the facial nerve ; in its course it gives off some communicating branches to the hypoglossal nerve near the anterior border of the hyo-glossus. It supplies also the mucous membrane of the mouth, gums, and the sublingual gland, one or more branches to the submaxillary ganglion, and at the apex of the tongue the terminal branches of this nerve and the hypoglossal are connected. SUBMAXILLARY At the lower border of the gustatory nerve as GANGLION. it lies upon the hyo-glossus muscle, and before it crosses the submaxillary duct, you will find a small, convex, tri- angular ganglion, about the size of a pin's head. Like the other ganglia in connection with the branches of the fifth pair, it receives filaments of communication of three different kinds viz. motor, sensory, and sympathetic. Its motor root is the chorda tympani, derived from the facial nerve : its sensory branches proceed from the gustatory ; and its connection with the sympathetic system is established by a branch which comes from the nervi molles round the facial artery. The ganglion supplies five or six branches of distribution to the submaxillary gland, its duct, and the mucous membrane of the floor of the mouth. Meckel describes a small branch of the ganglion which sometimes passes forwards to join a branch of the hypoglossal, on the hyo-glossus m., and ends in the genio-hyo-glossus . LINGUAL The lingual artery is generally the second ARTEHY. branch of the external carotid. Curving slightly upwards and inwards from its origin, the artery soon runs forwards round the great cornu of the hyoid bone, beneath the posterior belly of the digastricus and stylo-hyoideus, and then passes 106 RANINE VEIN. beneath the hyo-glossus m. parallel to the os hyoides. At the ante- rior edge of the hyo-glossus it ascends to the under surface of the tongue, and is continued forwards to the apex of the tongue under the name of ranine. Before the artery passes beneath the hyo- glossus, it is crossed by the hypoglossal nerve, but it immediately after becomes separated from the nerve by this muscle. Under the hyo-glossus the artery lies upon the middle constrictor of the pharynx, and the genio-hyo-glossus ; in the substance of the tongue, it lies between the genio-hyo-glossus and the inferior lingualis. The curves made by the artery are for the purpose of allowing the elongation of the tongue. Its branches are : 1. The hyoid, a small artery which runs along the upper border of the hyoid bone, supplying the muscles and anastomosing with its fellow, and with the hyoid branch of the superior thyroid artery. The nerve to the thyro-hyoid muscle, which is derived from the hypoglossal, accompanies this artery. 2. The dorsales linyuce, two or more, run under the hyo-glossus to the back of the tongue, the mucous membrane, tonsil, and soft palate. 3. The siiblingual, arising near the anterior border of the hyo- glossus, supplies the sublingual gland, the mylo-hyoideus, and the mucous membrane of the mouth and gums. This artery generally gives off the little artery of the frsenum linguae, which is sometimes wounded in cutting the fraenum in children who are tongue-tied ; especially when we neglect the rule of pointing the scissors downwards and backwards. 4. The ranine is the termination of the lingual artery. As it runs forwards to the tip of the tongue along the outer side of the genio-hyo- glossus, along with the gustatory nerve, it distributes branches to the tongue, and at the tip inosculates slightly with its fellow of the opposite side. The ranine vein, commencing at the tip of the tongue, after join- ing with the venae comites of the lingual artery and the dorsal veins of the tongue, runs along its under surface over the hyo- glossus, and terminates in the internal jugular or facial vein. The best place for finding and tying the lingual artery has been mentioned (p. 100). The rule laid down is trustworthy only when the artery runs its normal course. We have known an instance in which a good anatomist failed in an attempt to tie the OCCIPITAL ARTERY. 107 lingual artery, because the vessel arose from the facial behind the submaxillary gland, and then passed through the mylo-hyoideus to reach the tongue. OCCIPITAL The occipital artery arises from the posterior ARTERY. part of the external carotid, usually opposite the facial artery, and runs upwards and backwards along the lower border of the digastricus towards the mastoid process. It passes then under the posterior belly of the digastricus, and further on in its course it lies in the interval between the transverse process of the atlas and the mastoid process, close to the rectus capitis lateralis ; it now changes its direction, for it runs horizontally backwards in the occipital groove of the temporal bone, under all the muscles attached to the mastoid process namely, the sterno-mastoid, the splenius capitis, the trachelo-mastoid, and the digastricus, and it lies on the superior oblique and the com plexus. Arrived at the back of the head, the artery pierces the cranial attachment of the trapezius, and ascending, divides into wide-spreading branches for the supply of the scalp. In the first part of its course, the occipital artery crosses over the internal carotid artery, the internal jugular vein, the pneumo- gastric and the spinal accessory nerves, and is itself crossed by the hypoglossal nerve. It sends off the seven following branches : 1. Muscular branches to the digastric, stylo-hyoid, splenius, and trachelo-mastoid muscles. 2. The superior sterno-mastoid, which enters the muscle with the nervus accessorius. 3. The auricular ramifies on the cranial aspect of the concha. 4. The posterior meningeal Ascends with the internal jugular vein, and enters the cranium through the foramen jugulare to supply the dura mater of the posterior fossa. 5. The princeps cervicis, which we shall see better hereafter, is a short trunk which runs down the back of the neck, and divides into two branches a superficial, lying beneath the splenius, and supplying also the trapezius, and a deep branch lying under the complexus, and anastomosing with branches of the vertebral and with the deep cervical branch of the superior intercostal artery between this muscle and the semi-spinalis colli. 108 POSTERIOR AURICULAR ARTERY. 6. The mastoid enters the foramen in the mastoid process, and supplies the dura mater. 7. The cranial branches supply the scalp on its posterior aspect, and anastomose freely with the corresponding artery of the opposite side, the posterior auricular and the superficial temporal arteries. The occipital vein accompanies the artery, and is connected with the lateral sinus through a small vein running through the mas- toid foramen. It subsequently terminates in the internal jugular, occasionally in the external jugular vein. POSTEKIOB Au- The posterior auricular artery, the fifth branch, EICULAE ABTEBY. j s given off from the posterior part of the external carotid. It arises above the digastricus, lies on the styloid process, and under cover of the parotid gland reaches the furrow between the cartilage of the ear and the mastoid process. Before it reaches the furrow it is crossed by the facial nerve, 1 and just beneath it is the spinal accessory. Above the mastoid process it divides into two branches, a posterior inosculating with the occipital, and an anterior communicating with the temporal. It supplies the back of the scalp and the cartilage of the ear. It gives off 1. Small branches to the digastricus, stylo-hyoid, and the parotid gland. 2. The slylo-mastoid, a very constant little artery, which runs through the stylo-mastoid foramen to supply the mastoid cells, the vestibule, and the membrana tyrnpani. In young subjects, one of these latter branches forms a vascular circle around the circumference of the membrane with the tympanic branch of the internal maxillary. 3. The atiricular branch runs along the cranial surface of the auricle, and anastomoses with the superficial temporal and occipital arteries. Some of the branches pierce the cartilage of the ear and ramify on its. anterior surface. 4. The mastoid branch is distributed to the structures over the mastoid process. The posterior auricular vein is rather large, and running over the mastoid process, terminates in the external jugular vein. POSTEEIOK Au- The posterior auricular nerve lies close to the BICULAB NEBVE. artery of the same name. It is the first branch of 1 The posterior auricular artery frequently runs superficial to the facial nerve. CERVICAL PLEXUS OF NERVES. 109 the seventh or facial nerve after its exit from the stylo-mastoid foramen. It runs behind the ear and divides into an auricular branch to the retrahens and the attollens aurem, and an occipital branch to the posterior belly of the occipito-frontalis, which com- municates with the small occipital nerve. The nerve is connected with the great auricular nerve of the cervical plexus, and with the auricular branch of the pneumogastric nerve. ASCENDING This long and straight branch arises about half PHARYNGEAL an inch above the division of the common carotid. ARTERY. j^ asc ends between the internal carotid and the side of the pharynx to the base of the skull, lying upon the rectus capitis anticus major. It gives off numerous branches ; among them are : 1. Small external branches which pass outwards to supply the anterior recti muscles, the superior cervical ganglion, the pneumogastric and hypoglossal nerves, and the prevertebral lymphatic glands. They anastomose with the ascending cervical artery. 2. Pharyngeal branches, some of which pass to the two lower pharyngeal constrictors and the stylo-pharyngeus : one, the largest of all, enters the pharynx above the superior constrictor, and terminates in the soft palate, the Eustachian tube, and the tonsils. 3. Meningeal branches. One passes through the foramen lacerum ppsticum, with the internal jugular vein, and is distributed to the dura mater of the occipital fossa ; another through the foramen lacerum medium, and one through the anterior condylar foramen. . The pharyngeal vein receives some meningeal branches, also small veins from the soft palate, Eustachian tube, and uniting, form the pharyngeal plexus which opens into the internal jugular or common facial vein. The examination of the two remaining branches of the external carotid, the internal maxillary and temporal, must for the present be postponed. Meanwhile the student should make out the deep cervical plexus and its branches. CERVICAL This plexus is formed by the anterior branches PLEXUS OF of the four upper cervical nerves. It consists of a NERVES. series of loop-like communications, between these nerves, close to the transverse processes of the four upper cervical vertebrae ; each nerve dividing into an ascending and a descending 110 DEEP CERVICAL PLEXUS. branch, with the exception of the first. The plexus rests on the levator anguli scapulas and scalenus medius, and is situated behind the sterno-mastoid m. and the internal jugular vein. The plexus gives off superficial and deep branches : the super- ficial coming from the second, third and fourth nerves, the deep from the third and fourth n. The superficial branches have been already described (p. 68). The deep branches may be divided into an internal and an ex- ternal series. INTERNAL SERIES. 1. The phrenic arises from the third, fourth, and fifth cervical nerves, descends obliquely inwards over the scalenus anticus, and then crosses over the first part of the subclavian artery. Near the thorax it is joined by the sympathetic, and frequently by a looped branch from the nerve to the subclavius muscle. Its course through the thorax to its destination in the diaphragm will be described p. 112. 2. The communicantes noni come from the second and third cervical nerves, wind round the internal jugular vein, and join the descendens noni in front of the carotid sheath, forming the ' ansa hypoglossi.' They supply the depressor muscles of the os hyoides and larynx. 3. Muscular branches which proceed from the first cervical and the loop between it and the second cervical, to the recti antici, the rectus lateralis, and longus colli muscles. 4. Branches which communicate with the pneumogastric, hypo- glossal, and sympathetic nerves, and one to join the fifth cervical. EXTERNAL SERIES. 1. One or more comrminicating branches to the nervus accessorius : firstly in the sterno-mastoid, then in the occipital triangle, and lastly beneath the trapezius. 2. Musctilar branches to supply the trapezius, levator anguli scapulae, scalenus medius and sterno-mastoid. The branches to the trapezius, levator anguli scapulae, and scalenus medius, come from the third and fourth ; the branch to the sterno-mastoid from the second cervical nerve. The clavicle should now be sawn through the DISSECTION. middle, and the sternal half raised with the sterno-mastoid attached, so that the bone can be replaced, to study its relation to the subjacent parts. The scalene muscles and the subclavian artery throughout its whole course must next be care- fully dissected. While this is being done, the student must be SCALENE MUSCLES. Ill careful not to injure the branches of the subclavian artery, th& lymphatic duct on the right, and the thoracic duct on the left side,, the nerve to the subclavius m., the phrenic nerve, the cervical and the brachial plexuses of nerves, and their small branches. SCALENE The scalene muscles, so called from their resem- MUSCLES. blance to a scalene triangle, extend from the trans- verse processes of the cervical vertebras to the first and second ribs. They may be considered as intercostal muscles, since the transverse processes of the cervical vertebras are but rudimentary ribs. Anato- mists describe them as three separate muscles an anterior, a middle, and a posterior ; the anterior and middle are attached to the first rib, the posterior to the second. In plan and purpose these three muscles are one. SCALENUS The scalenus anticus is attached above to the ANTICUS. anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebras, and below by a flat tendon to the tubercle on the inner border and upper surface of the first rib in the front of the groove for the subclavian artery. SCALENUS The scalenus medius is attached above to the MEDIUS. posterior tubercles of the transverse processes of all the cervical vertebrae except the first, and below to the first rib behind the scalenus anticus, extending, from the tubercle, forwards for an inch and a half. SCALENUS The scalenus posticus is attached above to the POSTICUS. posterior tubercles of the transverse processes of the two or three lowest cervical vertebras, and below to the second rib between its tubercle and angle, anterior to the levator costas, and behind the serratus magnus. The scaleni are supplied by branches derived from the lower cervical nerves. The scalene muscles are important agents in raising the thorax, in a deep inspiration. Take a deep breath, and you can easily feel them contracting. They can bend the cervical portion of the spine, if their lower attachment be the fixed point, as in rising from the recumbent position. The scalenus anticus is one of those muscles about which we ought to know well all that lies in front of it, and all that lies- 112 PHRENIC NERVE. behind it. In the front of it are, the clavicle, the subclavius, the clavicular origin of the sterno-mastoid, the omo-hyoid, the phrenic nerve, the subclavian vein, the supra-scapular, the posterior scapu- lar, and the ascending cervical arteries. Behind it are the sub- clavian artery, the five nerves which form the brachial plexus, and the pleura ; to its inner side is the internal jugular vein, and the vertebral artery separates it from the longus Colli. Make your finger familiar with the feel of the tubercle on the first rib, to which the scalenus anticus is attached. This tubercle is the guide to the subclavian artery, for it enables you to find the outer edge of the scalenus anticus, where you must look for the vessel. Is the scalenus anticus entirely concealed from view by the sterno-mastoid or not ? This will depend upon the breadth of the clavicular attachment of the sterno-mastoid. As a general rule, it may be said that the scalene muscle is concealed by the sterno- mastoid, and that consequently, in tying the subclavian artery, it may be necessary to divide partially the clavicular origin of the muscle. The phrenic nerve runs down in front of the PHRENIC NERVE. , . ,, , , scalenus anticus, irom the outer to the inner border. It arises from the third, fourth, and fifth cervical nerves, but chiefly from the fourth. It enters the chest between the sub- clavian artery and vein, crosses in front of the internal mammary artery, and continues its course between the pericardium and pleura, in front of the root of the lung, to the diaphragm, which it supplies. When the spinal cord is injured above the fourth cervical ver- tebra, the origin of the phrenic is implicated ; therefore the dia- phragm, as well as the other muscles of inspiration, are paralysed. Death is the immediate result. 1 1 The phrenic nerve is joined by a filament from the sympathetic, and fre- quently by a filament from that branch of the brachial plexus which supplies the subclavius muscle. This is sometimes a branch of considerable size, and forms the greater portion of the phrenic itself. We have met with many instances in which this accessory branch was larger than the regular trunk ; in all of them it crossed over the subclavian artery in the third part of its course, and would prob- ably have been injured in the operation of tying this vessel. That such an acci- dent has actually happened is reported by Bransby Cooper in his surgical lectures. He speaks of having injured this accessory branch of the phrenic in tying the sub- clavian artery. The patient had incessant spasm of the diaphragm till he died. SUBCLAVIAN ARTERY. 113 COURSE AND RELATIONS OF THE SUBCLAVIAN ARTERIES. The left subclavian artery differs from the right, not only in its origin, but in the relations of the first part of its course. The right should, therefore, be examined first, and then the differences between it and the left. EIGHT SUBCLA- The right subclavian artery is one of the two VIAN ARTEKY. great branches into which the arteria innominata divides behind the sterno-clavicular joint. It runs outwards behind the scalenus anticus, then inclines downwards over the first rib, at the outer border of which it takes the name of axillary. The artery describes a curve, of which the greatest convexity is between the scalene muscles. The height to which the arch ascends varies. Generally, it rises higher in women than in men, on the right side than on the left. To study its relations more precisely, the course of the sub- clavian is divided into three parts : 1 . The part which intervenes between its origin and the inner border of the scalenus anticus. 2. That which lies behind the scalenus. 3. That which intervenes between the outer border of the scalenus and the outer border of the first rib. The first portion of the artery lies deeply in the neck and passes upwards and outwards to the inner border of the scalenus anticus. It is covered by the skin, platysma, superficial and deep fasciae, the sternal end of the clavicle, the sterno-inastoid, sterno-hyoid, and sterno-thyroid muscles, and a layer of deep fascia, continued from the inner border of the scalenus anticus. It is crossed by the internal jugular and vertebral veins, by the pneumogastric and phrenic nerves, and by some cardiac filaments of the sympathetic. Inferiorly it rests upon the pleura. Behind the artery are the recurrent branch of the pneumogastric, the sympathetic nerve, the longus colli, the transverse process of the seventh cervical vertebra and the apex of the lung covered with the pleura. The subclavian vein lies below the artery. Three branches arise from this portion of the subclavian viz. the vertebral, internal mammary, and thyroid axis. 114 SUBCLAVIAN ARTERY. In the second (the highest) part of its course, the artery lies between the scalene muscles. It is covered by skin, platysma, and superficial fascia, by the clavicular origin of the sterno-inastoid, the deep cervical fascia, and by the scalenus anticus and phrenic nerve FIG. 30. 3rd cervical n. . 4th cervical n. Piieumogas- tric n. . . . 5th cervical n. Brachial plexus Phrenic n. . . Line of reflec- tion of peri- cardium. Cervicalis ascendens a. Scalenus anticus. Inferior thyroid a. Superficialis colli a. Phrenic n. Posterior scapular a. Supra-scapular a. Subclavian a. Superior intercostal a. Internal mammary a. Pneumogastric n. Phrenic n. Appendix of left auricl* which separate it from the subclavian vein. Behind the artery is the scalenus medius ; above it, is the brachial plexus ; below it, is the pleura. Only one branch, the superior intercostal, is given off from this part of the artery. LEFT SUBCLAVIAN ARTERY. 115 In the third part of its course, the artery passes downwards and outwards, and lies in the supra-clavicular triangle upon the surface of the first rib. Here it is most superficial, and is covered by the skin, platysma, the two layers of the cervical fascia, and the clavicular branches of the superficial cervical plexus ; subse- quently by the suprascapular artery and vein, the clavicle, the subclavius muscle, with its nerve ; and, what is of much more consequence, it is here crossed by the external jugular and (often) the supra and posterior scapular veins ; so that there is here a confluence of large veins in front of the artery. The subclavian vein is situated below the artery, but on a plane an- terior to it. Beloiv it, is the first rib, and behind it the scalenus medius. Above the artery, and to its outer side, are the trunk nerves of the brachial plexus and the omo-hyoid m. One of these nerves (the conjoined fifth and sixth cervical) runs so nearly paral- lel with the artery, and on a plane anterior to it, that it is quite possible to mistake the nerve for the artery, in the operation of tying it. We have heard a hospital surgeon of great experience say, that he had seen this mistake committed on three separate occasions. In this part of its course, the artery as a rule gives off' no branches; the most frequent exceptions are the posterior scapular, and supra-scapular. LEFT SUBCLA- The left subclavian is the last of the three great VIAN AKTEKY. branches which arise from the arch of the aorta. It ascends nearly vertically out of the chest, and then arches in front of the apex of the lung and pleura to reach the inner border of the scalenus anticus, behind which it runs over the first rib. In the first part of its course the left subclavian lies deeply in the chest, near the spine. On its outer or left side it is covered by the pleura ; on its inner or right side are at first the trachea, then the oesophagus and thoracic duct ; in front are the left lung, covered with its pleura, the pneumogastric and phrenic nerves, and the cardiac branches, all of which lie parallel with the artery, the left common carotid, and the left brachio-cephalic vein ; at the level of the upper part of the chest it has in front the sterno-thyroid, sterno-hyoid, the sterno-mastoid muscles, the left internal jugular and vertebral veins, and the sternal end of the clavicle ; behind it i 2 116 LEFf SUBCLAVIAN ARTEKY. are the longus colli, the vertebral column, the inferior cervical ganglion of the sympathetic, the oesophagus, and the thoracic duct. Behind the scalenus anticus, and on the surface of the first rib, the relations of the left subclavian are similar to those of the right (P- H4). The left subclavian, then, differs from the right only in the first part of its course. Now, what are these differences ? 1. The left subclavian comes direct from the arch of the aorta, and is therefore longer, deeper in the chest, and more vertical than the right, which comes from the arteria innominata. 2. The left subclavian is in close relation with the oesophagus and the thoracic duct : the right is not. 3. The left subclavian is crossed by the left brachio-cephalic vein. 4. The left subclavian has the phrenic, pneumogastric, and cardiac nerves nearly parallel with it ; on the right side, these nerves cross the artery at a nearly right angle. 5. The left subclavian is not embraced by the recurrent laryn- geal nerve, like the right subclavian. The thoracic duct bears an important relation to the left sub- clavian. It ascends from the chest to .the left of the oesophagus and behind the artery ; then arching behind the internal jugular vein as high as the seventh cervical vertebra, it curves downwards and forwards in front of the scalenus anticus to terminate in the subclavian vein at its junction with the jugular. The duct is so thin and transparent that it easily escapes observation ; it is most readily found by raising the subclavian vein near its junction with the jugular, and searching with the handle of the scalpel on the inner side of the scalenus anticus, in front of the vertebral vein. Before tracing the branches of the subclavian artery, consider some points relating to the operation of tying it. To tie the artery in the first part of its course, namely, on the inner edge of the scalenus anticus, is an operation of great difficulty and danger, even with the parts in a normal position. The great depth at which the artery is placed, the size and close proximity of its numerous branches, the large veins by which it is covered, its connection with the pneumogastric, recurrent laryngeal, phrenic, LIGATURE OF THE SUBCLAVIAN ARTERY. 117 and sympathetic nerves, and, above all, its close contiguity with the pleura, form a combination of circumstances so formidable that one cannot be surprised the operation has never been performed with a favourable result. On the left side the operation is more difficult to perform than on the right, owing to the difference in the anatomical relation of the two sides. In the second part of its course, between the scalene muscles, the artery is more accessible, although it is rarely ligatured in this situation. It would be necessary to divide the clavicular origin of the sterno-mastoid, the cervical fascia, and the scalenus anticus, to reach the vessel ; the phrenic nerve and the subclavian vein would be the chief objects exposed to injury. This operation was per- formed first and with success by Dupuytren in the year 1819. More recently it has been performed by Dr. Warren, of Boston. The patient recovered, though the pleura was wounded. 1 But in the last part of its course, that is, on the outer side of the scalenus, the artery may be tied with comparative facility. The incision should be made from three to four inches in length, parallel with the upper border of the clavicle. We divide the platysma, some of the supra-clavicular nerves, and the cervical fascia. The external jugular vein and its tributaries must be drawn to the outer side, or divided and tied at both ends. The connective tissue should now be carefully cut through, and the posterior belly of the omo-hyoid sought for, as it runs just above the clavicle. After clearing away some fat and cellular tissue, the outer border of the scalenus anticus must be felt for, behind which the artery will be found lying upon the first rib. The operator now passes his finger downwards along the outer border of this muscle, as far as its insertion into the tubercle of the first rib, which can always be distinctly felt. The artery having been exposed by carefully dividing a layer of fascia immediately covering the vessel, the ligature is to be passed round the artery from above downwards, care being taken not to include in the ligature one of the cords of the brachial plexus. Mr. Ramsden, of St. Bartholomew's Hospital, was the first who tied the subclavian in the third part of its course, in the year 1 Med. Chirurg. Trans, vol. xxix. p. 25. 118 BRANCHES OF THE SUBCLAVIAN ARTERY. 1809 ; since that time the operation has been repeatedly performed, with very favourable results. In the hands of a surgeon possessed of a practical knowledge of anatomy the operation is easy, provided all circumstances be favourable : but circumstances are often very unfavourable. Ana- tomical deviations are by no means rare, and it often happens that the aneurismal or other tumour, on account of which the operation is performed, raises the clavicle beyond its natural level, and so disturbs the parts, that to expose the artery and place 'a ligature around it becomes exceedingly difficult. Under such circumstances one cannot be surprised that even distinguished anatomists have committed mistakes. Sir Astley Cooper l failed in one instance. Dupuytren perforated the artery with the point of the needle, and included one of the nerves in the ligature : fatal haemorrhage was the result. 2 We were present at an operation in which the large nerve (a branch of the brachial plexus) which runs parallel with and on a plane anterior to the artery was mistaken for it and tied ; the surgeon being deceived by the pulsation communicated to the nerve. The description of the means whereby the collateral circulation is maintained is deferred until the branches of the subclavian have been made out and described. BRANCHES OP r ^ ne branches of the subclavian extend so wide- THE SUBCLAVIAN ly, that in the present dissection we can trace ARTERY. them only for a short distance. They are four in number: 1. The vertebral. 2. The thyroid axis, a short thick trunk which gives off the inferior thyroid, supra-scapular, and posterior 'scapular. 3. The internal mammary. 4. The superior intercostal, which gives off the deep cervi- cal. As a rule, the vertebral, the thyroid axis, and the internal mammary are given off from the subclavian in the first part of its course, and the superior intercostal in the second part. The 1 London Medical Eeview, vol. ii. p. 300. 2 Edinburgh Med. and Surg. Journal, vol. xvi. 1820. SUBCLAVIAN VEIN. 123 vein terminates on the right side in the vena azygos major ; on the left in the brachio-cephalic. DEEP CERVICAL This artery arises from the superior intercostal, ARTEKY. seldom direct from the subclavian. It goes to the back of the neck between the first rib and the transverse process of the seventh cervical vertebra, and ascends between the com- plexus and the semi-spinalis colli, both of which it supplies. It sometimes inosculates with the princeps cervicis, a branch of the occipital (p. 107). To test your knowledge of the branches of the subclavian artery, reflect upon the answer to the following question : ' If the artery were tied in the first part of its course before it gives off any branches, how would the arm be supplied with blood ? ' The answer is, by six collateral channels, as follow ; 1 . By the communi- cations between the superior and inferior thyroid ; 2. Between the two vertebral ; 3. Between the internal mammary and the inter- costals and the epigastric ; 4. Between the thoracic branches of the axillary, and the intercostal branches of the aorta ; 5. Between the superior intercostal and the aortic intercostals ; 6. Between the princeps cervicis and the deep cervical. Most of these inoscu- lations are shown in the diagram (p. 122). Again, if the subclavian were tied in the third part of its course, the circulation would be carried on by the communications : 1 . Be- tween the supra-scapular and the dorsalis scapulas, a branch of the subscapular ; 2. Between the supra-acromial branch of the supra- scapular and the acromio-thoracic ; 3. Between the posterior scapular and the subscapular and dorsalis scapulae ; 4. Between the internal mammary, the aortic intercostals and superior intercostal on the one hand, and the long and short thoracic branches of the axillary, on the other. SUBCLAVIAN The subclavian vein does not form an arch like VEIN, the artery, but proceeds in a nearly straight line over the first rib to join the internal jugular. It extends from the outer margin of the first rib to midway between the inner border of the scalenus anticus and the sterno-clavicular articulation, where it joins the internal jugular to form the brachio-cephalic vein. Throughout its whole course the vein is situated on a plane 124 BRACHIAL PLEXUS OF NERVES. anterior to and a little lower than the artery, from which it is separated by the scalenus anticus, the phrenic and pneumogastric nerves. It has a pair of valves just before its junction with the internal jugular. It receives the anterior jugular, the external jugular, and through it, the supra-scapular and posterior scapular veins. BRACHIAL The large nerves forming the plexus which sup- PLEXTJS OF plies the upper extremity are the anterior divisions NERVES. o f the four lower cervical and the larger portion of the first dorsal, with a small fasciculus derived from the fourth cervical nerve. Emerging from the intervertebral foramina the nerves appear between the anterior and middle scalene muscles, and pass with the subclavian artery into the axilla. In the neck the nerves have no plexiform arrangement, and it is only in the axilla that they branch and communicate largely with each other, and form the brachial plexus of nerves. The nerves in the neck are wide and are situated higher than the subclavian artery, and nearly on the same plane ; but as they descend beneath the clavicle, they converge and form large communications; with each other, thus constituting the brachial plexus which completely surrounds the artery : one cord lying to. the outer side, a second lying to the inner side, and a third behind the vessel. The plexus is crossed superficially by the omo-hyoid muscle, and by the supra-scapular and posterior scapular arteries, and their corresponding veins. The arrangement of the nerves in the formation of the plexus is very variable, and often not alike on both sides. The most usual arrangement is, that at the outer border of the scalenus anticus, the fifth and sixth cervical nerves unite to form an upper trunk ; the eighth and the first dorsal n. form a lower trunk ; the seventh cervical runs for some distance alone, and forms a middle trunk. Now each of these four upper primary nerves divides into an anterior and a posterior branch : the anterior branches given off from the fifth, sixth, and seventh form the outer cord of the plexus ; the anterior branches given off from the eighth cervical and first dorsal form the inner cord ; while the posterior branches of all the BRANCHES OF THE BRACHIAL PLEXUS. 125 nerves (namely, the fifth, sixth, seventh, and eighth cervical) unite to form the posterior cord. 1 The branches arising from the plexus are best arranged into those given off above the clavicle, and those given off below it. The following are those given off above the clavicle. FIG. 32. DIAGRAM OF THE FORMATION OF THE BBACHIAL PLEXUS AND ITS BRANCHES. C 4-8. Anterior trunks of the cervical nerves. 17. Lesser int. cutaneous. D 1. Anterior trunk of the first dorsal n. 18. Musculo-cutaneous. 9. N. to the rhomboid m. 19. Circumflex. 10. Supra-scapular. 20. Median. 11. N. to subclavius m. 21. Musculo-zpiral. 12-13. Anterior thoracic. 22. Ulnar. 14, 15, 16. Subscapular n. 23. Int. cutaneous. 24. Ext. respiratory of Bell. a. The branch forming one of the roots of the phrenic arises from the fifth cervical. (Not in the diagram.) b. Nerve to the subclavius m. This proceeds from the fifth and sixth cervical, and crosses the subclavian artery in the third part 1 Very frequently the posterior branch of the eighth cervical nerve does not, stricfly speaking, form part of the posterior cord, but is continued on as a separate fasciculus to form part of the musculo-spiral nerve. For a description of the arrangement of the nerves constituting the plexus, see a paper, by Lucas, Guy's Hospital Reports, 1875 ; also Turner in the Journal of Anatomy, 1872. 126 BRANCHES OF THE BRACHIAL PLEXUS. of its course. It frequently sends a filament, which passes in front of the subclavian vein to join the phrenic nerve. c. Nerves to the scaleni and the longus colli muscles are given off from the lower cervical nerves as they leave the inter vertebral foramina. d. Nerve to the rhomboid muscles. This arises from the fifth cervical nerve, passes through the scalenus medius, and accom- panies the posterior scapular artery, beneath the levator anguli scapulae, which, as well as the rhomboid muscles, it supplies. e. The supra-scapular nerve arises from the cord formed by the fifth and sixth cervical n., runs to the upper border of the scapula, where it meets with the corresponding artery, and then passes through the notch in the scapula. In the supra-spinous fossa it gives off two branches to the supra-spinatus m. and an upper articular branch to the shoulder; it then descends behind the acromion process to the infra-spinous fossa, distributing a branch to the infra-spinatus muscle, and a lower articular filament to the shoulder joint. f. The posterior thoracic nerve (called external respiratory by Sir C. Bell) to the serratus mar/nus arises from the fifth and sixth cervical (sometimes also from the seventh) in the substance of the scalenus medius. It passes through this muscle and subsequently emerges below the rhomboid nerve ; it then descends behind the brachial plexus and the subclavian vessels to the outer surface of the serratus magnus, to the several digitations of which it is exclusively distributed. cj. An articular branch is distributed to the shoulder joint ; besides some filaments to the constituent bones. It only remains to be observed that the upper cord of the brachial plexus receives a branch from the lower cord of the cer- vical, and that each of its component nerves communicates by slender filaments with the sympathetic. Below the clavicle the plexus gives off branches for the supply of the arm ; namely, from the outer cord, the external anterior thoracic (to the pectoralis major), the musculo-cutaneous, and the outer head of the median ; from the inner cord, the internal anterior thoracic n. (to the pectoralis minor), the inner head of TEMPORAL AND PTERYGO-MAXILLARY REGIONS. 127 the median, the ulnar, the internal cutaneous, and the lesser in- ternal cutaneous (nerve of Wrisberg) nerves ; from the posterior cord, the three subscapular (to the subscapularis, the latissimus dorsi, and teres major), the circumflex (to the deltoid and teres minor) and the musculo-spiral nerves : all of which will be described more fully in the dissection of the upper extremity. TEMPOEAL AND PTEEYGO-MAXILLAEY EEGIONS. In this dissection, the parts should be examined in the following order : 1. Superficial and deep fasciae. 6. Pterygoid muscles. 2. Superficial arteries and nerves of 7. Internal maxillary artery and the temple. branches. 3. Masseter muscle. 8. Inferior maxillary nerves and 4. Temporal aponeurosis. branches. 5. Temporal muscle. To expose the temporal region, the skin of the temple should be reflected from below upwards. Beneath the skin you come upon a layer of tough connective tissue, continuous, above, with the aponeurosis of the scalp ; below, with the fascia covering the masseter and the parotid gland. In this tissue are contained the superficial temporal vessels and nerves. TEMPORAL This is the smaller of the two terminal branches ARTERY. of the external carotid. Arising in the substance of the parotid gland near the neck of the jaw, it passes over the root of the zygoma, close to the meatus auditorius externus, ascends for about 1^ inches on the temporal fascia, and there divides into an anterior and a posterior branch. Above the zygoma it is superficial, being covered only by the attrahens aurem and a strong layer of fascia; here it is accompanied by branches of the facial nerve, and by the auriculo-temporal branch of the inferior division of the fifth nerve. It gives off the following branches : a. Several small branches to the parotid gland, the temporo-maxil- lary articulation, and the masseter. 128 AURICULO-TEMPORAL NERVE. b. The transversalis faciei (p. 41). c. The anterior auricular branches, two in number, superior and inferior, ramify on the front of the pinna of the ear, inosculating with branches of the posterior auricular. d. The middle temporal, a small vessel given off while the artery is still in the parotid gland, pierces the temporal fascia above the zygoma, and running in the substance of the temporal muscle, anastomoses with the temporal branches of the internal maxillary. Of the two branches into which the temporal divides, the anterior runs tortuously towards the external angle of the frontal bone, distant from it about an inch. Its ramifications extend over the forehead, supplying the orbicularis and occipito-frontalis m., and inosculate with the supra-orbital and frontal arteries. The posterior runs towards the back of the head, and inosculates freely with the occipital and posterior auricular. The anterior branch, although the smaller, is usually selected for arteriotoiny, the posterior being covered by a strong and unyielding fascia. The temporal vein is formed by the junction of the veins accom- panying the terminal branches of the temporal artery, which are situated superficial to the arteries; just above the zygoma it is joined by the middle temporal vein which takes its origin from a plexus in the temporal fossa. The common temporal vein, formed by the union of these three veins, passes over the zygoma, enters the parotid gland, and joins the internal maxillary vein to form the temporo-maxillary vein. AURICULO-TEM- This nerve supplies the temple and side of the poBAi NEKVE. head with common sensation. It arises, close to the foramen ovale, from the third division of the fifth pair by two roots (between which the middle meningeal artery runs). From its origin it proceeds outwards beneath the external pterygoid, between the neck of the jaw and the internal lateral ligament. It then ascends beneath the parotid, over the root of the zygoma, where it accompanies the temporal artery, and divides, like it, into an anterior and a posterior branch. The posterior branch is the smaller of the two ; the anterior forms communications with the temporal branches of the facial, and the orbital branch of the superior maxillary. The ramifications of the nerve correspond with those of the artery. TEMPORAL REGION. 129 Near their origin the roots of the nerve are connected by fine filaments with the otic ganglion, and close to the condyle of the jaw the nerve sends round the external carotid artery two com- municating brandies to the temporo-facial branch of the facial nerve. It here distributes parotid brandies to the gland ; articular brandies to the temporo-maxillary articulation, to the meatus auditorius and the membrana tympani. Above the zygoma it gives off two auri- cular filaments ; the upper ramifies in the skin of the outer aspect of the ear, mainly on the tragus and upper half of the auricle ; the lower supplies the lobule and lower part of the pinna. Lastly, in the subcutaneous tissue of the temple, we find the temporal branches of the facial nerve, which supply the frontalis, the attrahens aurem, the orbicularis palpebrarum, tensor tarsi, and corrugator supercilii. MASSETEB This muscle arises from the lower edge of the MOSCLE. zygoma, and is inserted into the outer side of the ramus and coronoid process of the jaw. The masseter is composed of superficial and deep fibres which cross like the letter X. The superficial fibres, constituting the principal part of the muscle, arise from the anterior two-thirds of the zygoma and the malar process of the superior maxilla, by tendinous fibres which occupy the front border of the muscle, and send aponeurotic partitions into its substance. These fibres pass downwards and backwards, this direction giving them greater advantage, and are inserted into the angle and part of the ramus of the jaw. The deep fibres, mainly muscular (which are concealed by the parotid gland), arise from the posterior third of the zygoma, incline forwards, and are in- serted into the upper half of the ramus and the coronoid process. Besides these, a few fibres, arising from the inner surface of the zygoma, are inserted into the coronoid process and the tendon of the temporal muscle. Its action is to raise the jaw and help to masticate the food. Its nerve comes from the inferior maxillary. The following objects lie superficial to the masseter : 1 . Zygomatici major and minor; 2. Orbicularis palpebrarum; 3. Glandula socia parotidis and parotid duct ; 4. Transversalis faciei artery ; 5. Facial artery and vein ; 6. Branches of the facial nerve. K 130 TEMPORAL MUSCLE. TEMPORAL This strong shining aponeurotic membrane FASCIA. covers the temporal muscle ; its chief use being to give additional origin to its fibres. It is attached above to the temporal ridge, and increasing in thickness as it descends, divides near the zygoma into two layers, which are attached to the outer and inner borders of the zygomatic arch. These layers are separated by -fat, in which is found a filament from the orbital branch of the superior maxillary nerve, and the orbital branch of the temporal artery. The density of this aponeurosis explains why abscesses in the temporal fossa rarely point outwards ; the pus generally makes its way, beneath the zygoma, into the mouth. Reflect the aponeurosis, and notice that it is separated from the temporal muscle, near the zygoma, by fat. The absorption of this fat, and the wasting of the muscle, occasion the sinking of the temple in emaciation and old age. Divide the zygomatic arch on each side of the DISSECTION masseter, and turn it downwards, taking care of the masseteric nerve and artery which enter its under aspect. Observe the direction of the superficial and deep fibres, and the tendinous partitions whicll augment the power of the muscle by increasing its extent of origin. The masseteric nerve and artery enter the under surface of the muscle near to its posterior border, through the sigmoid notch of the jaw ; the artery comes from the internal maxillary, the nerve from the motor division of the inferior maxillary. TEMPOBAL This broad fan-shaped muscle arises from the MUSCLE. whole of the temporal fossa (except the malar sur- face) and the deep surface of the temporal fascia. Its fibres converge to a strong tendon, which is inserted into the inner sur- face, the apex, and anterior border of the coronoid process, as far forwards as the last molar tooth. The fibres of the muscle, converging from their wide origin, pass under the zygomatic arch, and terminate upon their tendon, the outer surface of which is partially concealed by the insertion of those fibres which come from the temporal aponeurosis : remove them, and see how this tendon radiates into the muscle like the ribs of a fan. PTERYGO-MAXILLARY REGION. 131 Its nerves (two deep temporal) are branches of the inferior maxillary (p. 139). Between the posterior border of this muscle and the neck of the inferior maxilla, the masseteric nerve and artery pass to their destination : in front of the- muscle, the buccal branch of the in- ferior maxillary nerve descends to the buccinator with its companion artery. The temporal muscle is in relation on its deeper surface with the external pterygoid and buccinator muscles, the internal max- illary artery and vein, and the deep temporal arteries and nerves. PTERYGO-MAX- The zygomatic arch having been already divided, ILLARY EEGION. the structures should be cleaned so as to expose the coronoid process of the jaw, the insertion of the temporal muscle, and the loose fat which surrounds it. Next, saw through the coronoid process in a direction downwards and forwards, so as to include the insertion of the muscle, and reflect it upwards without injuring the subjacent vessels and nerves. To gain a good view of the muscles, nerves, and DISSECTION vessels of the pterygo-maxillary region, a portion of the ascending ramus of the jaw must be removed with a Hey's saw, as shown in the diagram on the next page. In this region we have to examine the two pterygoid muscles, the trunk and branches of the internal maxillary artery, the inferior maxillary nerve, and the internal lateral ligament of the lower jaw. All these structures are imbedded in loose soft fat, which must be cautiously removed without injuring them. EXTERNAL This muscle arises by two heads, one, the upper, PTERYGOID. from the great wing of the sphenoid and from the ridge below it ; the lower, from the outer surface of the external pterygoid plate, a few fibres taking origin from the outer side of the tuberosities of the palate and superior maxillary bones. The muscle passes horizontally backwards and is inserted into the neck of the jaw, and slightly into the border of the inter-articular fibre cartilage of the temporo-maxillary articulation. The advantage of the insertion of some of its fibres into the inter-articular cartilage is, that the cartilage follows the condyle in all its movements. When the jaw is dislocated, it is chiefly by the K 2 132 PTERYGOID MUSCLES. action of this muscle, which draws the condyle forwards into the zygomatic fossa ; the inter-articular cartilage being dislocated with the condyle. By its deep surface the muscle is in relation with the internal pterygoid m., the internal lateral ligament, the arteria meningea media, the auriculo-temporal, the gustatory, the inferior dental, and chorda tympani nerves, and occasionally with the internal FIG. 33. Anterior deep temporal n. and a. External pterygoid m. Posterior deep temporal n. and a. Masscteric 11. and a. Infra-orbital a. Spheno-maxillary fossa .... Superior dental a. Buccal a. . . . Parotid duct . . Buccal n. . . . . Pterygo-maxillary ligament. Inter-articular flbro- cartilage. Temporal artery and auriculo- temporal nerve. Middle meningeal a. Inferior dental a. Inferior dental n. Gustatory n. Mylo-hyoid n. Internal pterygoid in. PTERYGOID MUSCLES AND INTERNAL MAXILLARY ARTERY. maxillary artery. Between its two heads of origin the buccal and anterior deep temporal nerves emerge. INTERNAL This muscle arises by musculo-tendinous fibres PTERYGOID. from the inner surface of the external pterygoid plate of the sphenoid bone and from that portion of the tuberosity of the palate bone which forms the lower part of the pterygoid fossa, also by a smaller slip in front of the external pterygoid from the external surface of the tuberosities of the palate and superior INTERNAL MAXILLARY ARTERY. 133 maxillary bones. It is inserted into the rough surface on the inner side of the angle of the lower jaw, as high as the dental foramen. The internal pterygoid is in relation superficially with the ex- ternal pterygoid, the internal lateral ligament, the internal maxillary artery and vein, the inferior dental vessels and nerve, the mylo-hyoid artery and nerve, the chorda tympani and the buccal nerves ; by its deep surface, with the tensor palati and superior constrictor muscles. Notice particularly the direction of the fibres of the pterygoid muscles. The fibres of the external run horizontally outwards and backwards from their origin ; the fibres of the internal run downwards, backwards and outwards from their origin. The in- ternal pterygoid has tendinous septa like the masseter. Both the pterygoids get their nerves from the motor division of the inferior maxillary nerve. The internal pterygoid raises the lower jaw, acting in concert with the temporal and masseter muscles ; it moreover assists the external pterygoid and anterior part of the masseter to draw the jaw forwards. The external pterygoid draws the jaw forwards and somewhat to the opposite side, and also in conjunction with the internal pterygoid produces the lateral movements of the jaw essential to the mastication of the food. Consequently they are enormously developed in all ruminants and comparatively feebly in carnivorous animals. The antagonistic muscles of the forward action of the two pterygoids are the temporal m. and the deep fibres of the masseter. Saw through the neck of the jaw, disarticulate the condyle with its fibro-cartilage from the glenoid cavity, and turn it forwards with the external pterygoid, so that the condyle can be replaced if desirable. A little dissec- tion will bring into view the internal lateral ligament, the internal maxillary artery and vein, the inferior maxillary nerve and its branches, and the chorda tympani nerve. INTERNAL MAX- This is the larger of the two terminal branches ILLAEY AKTERY. into which the external carotid divides, opposite the neck of the jaw in the parotid gland. It passes horizontally forwards between the neck of the jaw and the internal lateral liga- ment, then runs tortuously, in some cases above, in others beneath, 134 INTERNAL MAXILLARY ARTERY. the external pterygoid, enters the spheno-maxillary fossa between the two heads of the external pteiygoid, where it terminates by dividing into numerous branches. The course of this artery is divided into three stages. In the first, the artery lies between the neck of the jaw and the internal lateral ligament ; in the second, it lies either over or under the external pterygoid ; in the third, it lies in the spheno-maxillary fossa. BEANCHES OF THE INTEENAL MAXILLAEY AETEEY IN THE THEEE STAGES OF ITS COUESE. BEANCHES IN THE FIRST BRANCHES IN THE SECOND STAGE. STAGE. BRANCHES IN THE THIRD STAGE. a. Tympanic. Six to the five muscles of i. Superior dental. 6. Meningea media. mastication, namely : c. Meningea parva. d. Inferior dental. e. Masseteric. /. Anterior and posterior deep temporal. g. External and internal pterygoid. h. Buccal. j. Infra-orbital. k. Descending palatine. I. Vidian. m. Pterygo-palatine. n. Nasal or spheno-pala- tine. BRANCHES IN a. The tympanic ascends behind the articulation of THE FIRST PART. the jaw, and passes through the Glaserian fissure to the tympanum. It supplies that cavity and the membrana tympani, and anastomoses with the stylo-mastoid and Vidian arteries. It occa- sionally gives off a deep auricular branch which pierces the anterior wall of the external auditory meatus, supplying the skin of this canal. This artery is not infrequently given off from a branch of the internal maxillary artery. 6. The middle meningeal artery ascends between the two roots of the auriculo-temporal nerve, behind the external pterygoid, and enters through the foramen spinosum into the cranium, where it ramifies between the dura mater and the bones. In the skull it gives off small branches to the Gasserian ganglion ; a petrosal branch passing through the hiatus Fallppii ; orbital branches entering the orbit through the sphenoidal fissure ; and temporal branches which pierce the great wing of the sphenoid to enter the temporal fossa. Its further course is described at p. 16. INTERNAL MAXILLARY ARTERY. 135 c. The meningea, parva (not marked in the plan) ascends through the foramen ovale into the skull, and supplies chiefly the ganglion of the fifth cranial nerve. It often comes from the meningea media. d. The inferior dental artery descends behind the neck of the jaw to the dental foramen, which it enters with the dental nerve. It then proceeds through a canal in the diploe to the symphysis, where it minutely inosculates with its fellow. In this canal, which runs beneath the roots of all the teeth, the artery gives branches which, ascend through the little foramina in the fangs, and supply the pulp in their interior. Opposite the foramen mentale arises the mental branch already de- scribed (p. 49). Before entering the dental foramen the artery furnishes a small branch mylo-hyoid which accompanies the nerve proceeding to the mylo-hyoid muscle. FIG. 34. Tliird stage. Second stage. First stage. PLAN OF INTERNAL MAXILLARY ARTERY. BRANCHES IN e. The masseteric branch passes through the sigmoid THE SECOND PART, notch of the jaw behind the temporal muscle to the under surface of the masseter, with the masseteric nerve, and inoscu- lates with the facial and transverse facial arteries. f. The anterior and posterior deep temporal arteries ascend to supply the temporal muscle, ramifying between the muscle and the bone, one near the front, the other near the posterior border of the muscle. They communicate with the superficial and middle temporal arteries, with the terminal branches of the lachrymal a., and with the temporal branches of the arteria meningea media. 136 BRANCHES OF THE INTERNAL MAXILLARY ARTERY. g. The pteryyoid branches supply the internal and external pterygoid muscles. h. The buccal branch runs forward with the buccal nerve to the buccinator, where it anastomoses with the facial artery. BRANCHES IN i. The superior dental branch runs along the tube- THK THIRD PABT. rosity of the superior maxillary bone, and sends small arteries through the foramina in the bone to the pulps of the molar and bicuspid teeth. It also supplies the gums, and the mucous membrane of the antrum. j. The infra-orbital branch ascends through the spheno-maxillary fissure, then runs forward along the infra- orbital canal with the superior maxillary nerve, and emerges upon the face at the infra-orbital foramen, beneath the levator labii superioris. In the infra-orbital canal the artery sends branches, anterior dental, downwards through little canals in the bone to the incisor and canine teeth, and upwards into the orbit to the lachrymal gland, the inferior oblique, and inferior rectus. After issuing from the foramen it sends upwards branches to the lachrymal sac, and descending branches to the upper lip. The former anastomose with the nasal branches of the ophthalmic and facial arteries ; the latter with the superior coronary, transverse facial, and buccal arteries. k. The descending palatine, a branch of considerable size, runs down the posterior palatine canal with the palatine nerve (a branch from Meckel's ganglion), and then along the roof of the hard palate, towards, the anterior palatine canal, in which, much diminished in size, it inos- culates on the septum nasi with a branch of the spheno-palatine artery. It supplies the gums, the glands, and mucous membrane of this part, and furnishes branches to the soft palate. I. The Vidian, an insignificant branch, runs backwards through the Vidian canal with the Vidian nerve, and is distributed to the Eustachian tube, the pharynx, and the tympanum. m. The ptery go -palatine is a small but constant branch which runs backwards through the pterygo-palatine canal with the pharyngeal nerve from Meckel's ganglion, and ramifies upon the upper part of the pharynx and the Eustachian tube. n. The nasal or splieno-palatine branch enters the nose through the spheno-palatine foramen in. company with the nasal nerve from Meckel's (spheno-palatine) ganglion, and ramifies upon the spongy bones, the ethmoidal cells, and the antrum. One large branch, the artery of the septum, runs along the septum nasi towards the anterior palatine canal, where it joins the descending palatine artery. INFERIOR MAXILLARY NERVE. 137 Observe that all the branches of the internal maxillary artery in the first and third parts of its course traverse bony canals ; while the branches in the second part go directly to muscles. The internal maxillary vein is formed by the veins correspond- ing to the branches of the artery. As the vein lies between the PTERYGOID temporal and external pterygoid muscles it forms PLEXUS OF VEINS. a plexus ptenjcfoid plexus which communicates, above, with the cavernous sinus by branches which come through the foramina at the base of the skull ; in front it communicates with the facial vein. It joins the temporal in the substance of the parotid gland, and thus communicates with the external jugular vein. INFERIOR MAX- This great nerve is the largest of the three ILLARY NERVE divisions of the fifth cerebral nerve. It differs AND BRANCHES. from the other two divisions, i.e. the ophthalmic and the superior maxillary, in that it contains motor as well as sensory filaments ; the motor being furnished by the small non- ganglionic root of the fifth nerve. It is necessary to remember this point of its physiology, in order to understand its extensive distribution ; for the sensory portion supplies the parts to which it is distributed with common sensation only, whilst the motor portion supplies all the muscles concerned in mastication. The nerve, composed of sensory and motor filaments, emerges from the skull through the foramen ovale as a thick trunk, under the name of the inferior maxillary. It lies directly external to the Eustachian tube, and is covered by the external pterygoid muscle, which must be turned on one side to expose it. Immediately after its exit from the skull, the nerve divides into two parts, an anterior, or motor division, and a posterior or sensory division. From the anterior portion (chiefly motor) are derived branches distributed to the muscles of mastication and the buccal nerve. From the posterior (mainly sensory) come the following branches : the auriculo-temporal, gustatory, and inferior dental ; there are also motor branches to the mylo-hyoid and anterior belly of the digastricus. This apparent anomaly will be presently explained. 138 INFERIOR MAXILLARY NERVE. BRANCHES OF THE INFEKIOR MAXILLAEY NERVE. ANTERIOR PORTION. POSTERIOR PORTION. Auriculo-temporal. To temporal muscle. Inferior dental. masseter. Gustatory or lingual. external pterygoid. Mylo-hyoideus. - internal pterygoid. Anterior belly of digastricus. buecal. The deep temporal branches, two in number, anterior and pos- terior, pass outwards close to the great wing of the sphenoid bone, and ascend with the temporal arteries to the temporal muscle. A middle temporal nerve is not infrequently present, and ascends beneath the temporal muscle to enter its deeper aspect. The posterior branch is occasionally joined with the masseteric nerve, the anterior with the buecal nerve. The branch to the masseter runs outwards above the external pterygoid, through the sigmoid notch of the jaw, to the under surface of the muscle. The branch to the external pterygoid comes, apparently, from the buecal nerve in its passage through this muscle. The branch to the internal pterygoid muscle proceeds from the inner side of the main trunk, close to the otic ganglion, and descending between the internal pterygoid and the tensor palati, enters the inner and deeper aspect of the muscle. The buecal branch, a sensory nerve, united at its origin with the anterior deep temporal and external pterygoid nerves, passes either above or between the fibres of the external pterygoid to the buccinator, where it spreads out into filaments, which form a plexus with the buecal branches of the facial nerve, and then supply the skin, mucous membrane, and glands of the cheek with common sensation. The motor power of the buccinator, remember, is de- rived from the facial nerve. That this buecal branch is mainly sensory is proved by the action of the muscle still continuing when the motor division of the fifth nerve is paralysed. The evidence is corroborated by a case in which this buecal branch proceeded from the second division of the fifth nerve; no communication being INFERIOR MAXILLARY NERVE. 139 discovered, after very careful dissection, between it and the motor root of the third division. 1 The auricula-temporal branch arises by two roots which embrace the middle meningeal artery before it enters the skull. The nerve runs backwards behind the external pterygoid and the neck of the jaw, ascends at first beneath the parotid gland, then over the root of the zygoma with the temporal artery, and divides, like it, into FIG. 35. PLAN OF THE BRANCHES OF THE INFERIOR MAXILLARY NERVE. an anterior and a posterior branch. The posterior branch supplies the pinna and surrounding tissues ; the anterior is distributed to the skin covering the vertex and temporal region, communicating with the temporal branches of the facial nerve and the orbital branch of the superior maxillary. 1 Turner, ' On the Variation of the Buccal Nerve.' Journal of Anat. and Phys., Ko. I., 1866. 140 INFERIOR MAXILLARY NERVE. The auriculo-temporal communicates at its origin with the otic ganglion, and then ascends behind the jaw with the temporal branches of the facial n. ; it also gives off an articular branch to the temporo-maxillary joint ; ttvo branches to the meatus auditorius and the membrana tympani ; parotid branches to the gland ; auri- cular branches, two in number an inferior, which is distributed to the ear below the auditory meatus, and a superior to the tragus and auricle. Its branches have been described (p. 6). The inferior dental branch emerges beneath the external ptery- goid, and descends between the ramus and the internal lateral ligament of the jaw to the dental foramen, which it enters with the dental artery. It then runs in the canal in the diploe of the jaw and furnishes filaments which ascend through the canals in the fangs of the teeth to the pulp in their interior. Opposite the foramen mentale it divides into two branches, the mental and incisor. Observe that the same nerve which supplies the teeth supplies the gums ; hence the sympathy between them. a. The mylo-hyoid branch, apparently arising from the dental, is derived from the motor root of the fifth, and may, with careful dissec- tion, be traced to it. It leaves the sheath of the inferior dental nerve near the foramen in the jaw, and runs in a groove on the inner side of the ramus to the lower surface of the mylo-hyoid, which muscle it supplies together with the anterior portion of the digastricus. b. The dental branches pass upwards to the fangs of the molar and bicuspid teeth. c. The incisor branch is the continuation of the nerve, and passes to the symphysis, supplying the canine and incisor teeth. d. The mental branch (sometimes called labial) emerges through the foramen mentale, and soon divides into numerous branches ; some ascend to the lower lip beneath the depressor labii inferioris, and com- municate with the facial nerve ; others pass inwards to the skin of the chin. The giistatory or lingual nerve lies at first behind the external pterygoid m., then descends obliquely forwards between the ramus of the jaw and the internal pterygoid in., and subsequently for a short distance between the jaw and the superior constrictor of the pharynx. Here it lies close under the mucous membrane of the GUSTATORY NERVE. 141 mouth near the last molar tooth of the lower jaw. Division of it in this situation relieves pain in cancer of the tongue. The gus- tatory n. then rests upon the stylo-glossus and the hyo-glossus m., and after crossing Wharton's duct passes to the tip of the tongue. The nerve at first lies in front of the inferior dental nerve (with which it is frequently connected), and beneath the internal maxillary a. Beneath the external pterygoid, the gustatory n. is joined at an acute angle by the chorda tympani (a branch of the facial). This branch emerges through a small canal, canal of Huguier, by the side of the Glaserian fissure, and passing behind the dental n., meets the gustatory, and runs along the lower border of this nerve to supply the submaxillary gland ; part of it joins the submaxillary ganglion, and it is then eventually distributed to the lingualis muscle. The gustatory nerve in its course gives off a. Communicating branches to the hypoglossal n., forming two or more loops at the anterior border of the hyo-glossus muscle. b. Communicating branches to the submaxillary ganglion. c. Branches to the mucotis membrane of the mouth, gums, and sub- lingual gland. d. Lingual branches which pass to the papillae of the sides and tip of the tongue : here also we find communications between this nerve and the hypoglossal. The duct of the submaxillary gland (p. 94), Wharton's duct, can now be traced to its termination. It passes from its under surface, runs forwards under the mylo-hyoideus and upon the hyo-glossus muscle ; it then passes beneath the gustatory nerve, and subse- quently runs between the sublingual gland and the genio-hyo- glossus, to open into the floor of the mouth, by the side of the frasimm linguae. Its length is about two inches ; its dimensions are not equal throughout ; it is dilated about the middle, and contracted at the orifice. Saliva, collected in the dilated portion, is sometimes spirted to a considerable distance out of the narrow orifice, in con- sequence of the sudden contraction of the neighbouring muscles. The gland is supplied with nerves by branches from the sub- maxillary ganglion, from the sympathetic, and the mylo-hyoid nerves. 142 DTTERXAL LATERAL LIGAMENT. In the floor of the mouth there occasionally exists a cystic tumour, called a ra?iZ, with semi-transparent walls, perceptible beneath the tongue. By some of the older writers it was looked upon as an abnormal dilatation of the submaxillary duct. There is, however, no reason for believing this swelling (except very rarely) to be connected with the duct. It is rather a cyst formed in the loose areolar tissue under the tongue, or is an enlargement of one of the small bursae which normally exist in this situation. The character of the saliva presents no agreement with the fluid contained in these cysts, which is thickly glairy, like the white of an egg. This so-called ligament (which is more like a LATEBAL LIGAMENT layer of fascia) passes from the spinous process oFTHELowEE of the sphenoid bone to the inner side of the ' AW> foramen dentale. Between this ligament and the neck of the jaw, we find the internal maxillary artery and vein, the auriculo-temporal nerve, the middle meningeal artery, the inferior dental nerve and artery, and a portion of the parotid gland. At this stage of the dissection you will be able to trace the course and relations of the internal carotid artery. But before doing this, examine the several objects which intervene between the external and internal carotids. These are 1. The stylo- glossus ; 2. The stylo-pharyngeus ; 3. The glosso-pharyngeal nerve; 4. The stylo-hyoid ligament. This arises from the front of the styloid process STTLO-GLOSSCS. , , - .1,1 m T near the apex, and from the stylo-maxillary liga- ment. It passes at first downwards and then horizontally forwards, and is inserted along the side of the tongue as far as the tip, some of its lower fibres decussating with those of the hyo-glossus. Its action is to retract the tongue. Its nerve is a branch of the hypo- glossal. STYLO- This arises from the inner side of the styloid PHABYXGECS. process near the base, and is inserted into the upper and posterior edges of the thyroid cartilage. It descends along the side of the pharynx between the superior and the middle constrictors ; some of its fibres blend with the constrictor muscles ; GLOSSO-PHARYNGEAL NERVE. 143 others join those of the palato-pharyngeus at its insertion. Curving round its lower border is seen the glosso-pharyngeal nerve, from which its nerve-supply is derived. Its action is to raise the larynx with the pharynx in deglutition. 1 Between the stylo-glossus and stylo-pharyngeus, and nearly parallel with both, is the stylo-ht/oid ligament. It extends from the apex of the styloid process to the lesser cornu of the os hyoides. It is often more or less ossified. The ascending palatine artery, a branch of the facial (p. 98), runs up between the stylo-glossus and the stylo-pharyngeus, and divides into branches which supply these muscles, the palate, the side of the pharynx, and the tonsils. It inosculates with the descending palatine, a branch of the internal maxillary. GLOSSO-PHA- The glosso-pharyngeal nerve is observed curving BYNGEAL NEEVE. forwards round the lower border of the stylo- pharyngeus (p. 142). It is the ninth cranial nerve, arises by five or six filaments from the groove between the olivary body and the restiform tract of the medulla oblongata, leaves the skull through the middle part of the foramen jugulare in a separate sheath of dura mater, in front of the pneumogastric and spinal accessory nerves, and descends between the internal jugular vein and the in- ternal carotid artery. It then crosses in front of the artery below the styloid process, and proceeds along the lower border of the stylo-pharyngeus. At this point, it curves forwards over that muscle and the middle constrictor of the pharynx, and disappears beneath the hyo-glossus, where it divides into its terminal branches, which supply the mucous membrane of the pharynx, the back of the tongue, and the tonsils. The glosso-pharyngeal is, at its origin, purely a sensory nerve. But soon after its exit from the skull it receives communications from the facial, the pneumogastric, and the sympathetic, so that it soon becomes a compound nerve i.e. composed of both sensory and motor filaments. At the base of the skull it presents two 1 Varieties of this muscle are frequently met with, chiefly as supernumerary muscles. They arise variably from neighbouring parts of the base of the skull close to the styloid process, and are inserted either into the pharyngeal constrictors or into the aponeurosis of the pharynx. 144 INTERNAL CAROTID ARTERY. ganglia tine jugular and the petrous (ganglion of Andersch). The branches given off by the petrous ganglion will be dissected here- after ; at present the student can only make out the branches which this nerve gives off in the neck, namely : Carotid branches, which surround the internal carotid artery as far as its origin, and communicate with the pharyngeal branch of the pneumogastric and with the sympathetic. Pharnygeal branches, three or four in number, which form by the side of the middle constrictor of the pharynx, a plexus, the pharyngeal plexus, supplemented by filaments derived from the pneumogastric, the nervus accessorius, the external laryngeal, and the sympathetic. Its branches supply the constrictor muscles and the mucous membrane of the pharynx, the back of the tongue, and the tonsils. Muscular branches which enter the stylo-pharyngeus m. Tonsillar branches which are given to the soft palate and the fauces, and to the tonsils forming a plexus (circulus tonsillaris). Lingual brandies, two in number, which are distributed to the base and lateral aspects of the tongue : one branch turns upwards and is distributed to the papillae circumvallatse, and the mucous membrane of the posterior third of the tongue as far backwards as the epiglottis ; the other passes to the middle of the side of the tongue communicating with the gustatory nerve. The styloid process must now be cut through at its base, and turned forwards with the muscles arising from it. The internal carotid artery will thus be exposed in the cerviqal region, as far as the carotid canal. The part of the artery contained within the carotid canal will be described hereafter. INTERNAL The internal carotid artery proceeds from the CAKOTID ABTEET. bifurcation of the common carotid at the upper border of the thyroid cartilage, and ascends vertically to the base of the skull by the side of the pharynx, in front of the transverse processes of the three upper cervical vertebrae. It enters the skull through the carotid canal in the temporal bone, runs tortuously by the side of the body of the sphenoid, and terminates in branches which supply the orbit and the brain. It is divided into four por- tions the cervical, petrous, cavernous, and cerebral. In the cer- vical part of its course, it is situated immediately to the outer side INTERNAL CAROTID ARTERY. 145 of the external carotid artery, behind the inner border of the sterno- mastoid. It soon gets beneath the external carotid, and lies deeply beneath the parotid gland, and ascends by the side of the pharynx and tonsil. It lies upon the rectus capitis anticus major, the supe- rior laryngeal nerve, and the superior cervical ganglion of the sym- pathetic ; to its outer side, is the internal jugular vein and the pneumogastric nerve ; to its inner side, is the pharynx, the tonsil, and the ascending pharyngeal artery ; it is crossed, successively, by the hypoglossal nerve, the occipital artery, the digastricus, and stylo-hyoid muscles ; higher up it is crossed by the styloid process, the stylo-glossus, and stylo-pharyngeus muscles, by the glosso- pharyngeal nerve and the stylo-hyoid ligament, all of which last- named structures intervene between it and the external carotid. The most important relation of the artery, in a surgical point of view, is, that it ascends close by the s.ide of the pharynx and tonsil. In opening an abscess, therefore, near the tonsil, or at the back of the pharynx, be careful to introduce the knife with its point inwards towards the mesial line : observe this caution the more, because in some subjects, the internal carotid makes a curve, or even a complete curl upon itself, in its ascent near the pharynx. In such cases an undue deviation of the instrument in an outward direction might injure the vessel. ASCENDING This artery generally arises from the back part PUABYNGEAL of the external carotid about half an inch above ABTEEY. the angle of the common carotid. It ascends in a straight course between the internal carotid artery and the side of the pharynx, towards the base of the skull, resting upon the rectus capitis anticus major. Its gives off three sets of branches : a. Pharyngeal branches, three or four in number : the two lower supply the inferior and middle constrictors, and stylo-pharyngeus, ana- stomosing with the superior thyroid a. ; the upper branch, the palatine, ascends upon the superior constrictor, runs down with the levator palati, above the superior constrictor, and supplies the muscles of the palate, the Eustachian tube, and the tonsil. b. Prevertebral branches, which supply the prevertebral muscles, the superior cervical ganglion of the sympathetic, the lymphatic glands, and the pneumogastric and hypoglossal nerves. L 146 PNEUMOGASTRIC NERVE. c. Meningeal branches, which supply the dura mater ; passing through the foramen lacerum medium, the anterior condylar foramen, and the foramen jugulare with the internal jugular vein. PNEUMOGASTBIC The pneumogastric nerve is the tenth cranial NEKVE. nerve, and has the longest course of all the cerebral nerves. It arises from the medulla oblongata by a series of roots, from twelve to fifteen in number, from the front of the restiform body. It passes out of the skull in a common sheath of dura mater and arachnoid, with the nervus accessorius through the foramen jugulare. Within the foramen jugulare a small ganglion ganglion of tlie root (Arnold's ganglion) about two lines in length, is situated upon the pneumogastric nerve, and is joined by a branch from the nervus accessorius. This ganglion will be described hereafter. About half an inch below the preceding the pneumogastric nerve swells out, and forms a second ganglion ganglion of the trunk (inferior ganglion), of a reddish-grey colour. This ganglion occu- pies about an inch of the nerve, but does not involve the whole of its fibres ; the branch from the spinal accessory joining the pneumo- gastric below the ganglion. It is united to the hypoglossal nerve, from which it receives filaments : it also receives filaments from the first and second spinal nerves, and from the superior cervical ganglion of the sympathetic. Thus, the pneumogastric, at its origin probably a nerve of sensation only, becomes, in consequence of the connecting filaments from these various branches, a compound nerve, and in all respects analogous to a spinal nerve. Leaving the skull at the foramen jugulare, the nerve descends in front of the cervical vertebras, lying successively upon the rectus capitis anticus major and the longus colli. In the upper part of the neck it is situated, lying in the same sheath, between the in- ternal carotid artery and the internal jugular vein ; lower down, it lies between and behind the common carotid and the internal jugular vein. It enters the chest, on the right side, crossing in front of the first part of the subclavian artery, nearly at a right angle ; on the left, running nearly parallel with it. In their course through the chest, the pneumogastric nerves PNEUMOGASTRIC NERVE. 147 have not similar relations. The right nerve lies beneath the subcla- vian vein, and then descending behind the right brachio-cephalic vein by the side of the trachea, is continued behind the right bronchus to the posterior part of the oesophagus. The left nerve passes behind the left brachio-cephalic vein, then crosses in front of the arch of the aorta, and behind the left bronchus to the anterior part of the oesophagus. Both nerves subdivide on the oesophagus into a plexus; the right nerve forming the posterior ossophageal plexus, the left the anterior. Each plexus again collects its fibres together to form a single trunk : thus two main nerves are formed which pass with the oesophagus through the diaphragm : of these the right is distributed over the posterior, the left over the anterior surface of the stomach. 1 In their long course from the medulla oblongata to the abdo- men, the pneumogastric nerves supply branches to most important organs : namely, to the pharynx, the larynx, the heart, the lungs, the oesophagus, the stomach, and the liver. The branches of the pneumogastric are those of communication and those of distribution : 1 . The branches of communication are those in connection with the ganglion of the root and the ganglion of the trunk. a. The ganglion of the root has connecting filaments with the accessory portion of the spinal accessory, the superior cervical ganglion of the sympathetic, and with the petrous ganglion of the glosso-pharyngeal. I). The ganglion of the trunk has communicating filaments with the hypoglossal, the loop between the first two cervical nerves, and the superior cervical ganglion of the sympathetic. 2. The branches of distribution are a. The auricular (Arnold), which cannot at present be seen, will be made out in the dissection of the nerve at the base of the skull. b. The plianjngeal arises from the upper part of the ganglion of the trunk, and, receiving a filament from the accessory part of 1 The differences in the course and destination of the right and the left pneumogastric nerves may be explained in the process of development. The student is therefore referred to works which treat of this subject. L 2 148 BRANCHES OF THE PNEUMOGA3TRIC NERVE. the spinal accessory, descends either in front of, or behind the internal carotid. The nerve, after passing to the inner side of the internal carotid, divides into branches, which with the other fila- ments (described p. 144) upon the middle constrictor muscle form the pharyngeal plexus. From this plexus branches are distributed to the muscles and the mucous membrane of the pharynx. 1 c. The superior larynyeal, derived from the middle of the ganglion of the trunk, descends behind the internal carotid, and divides into two branches, the internal and the external laryngeal. The internal laryngeal passes to the interval between the os hyoides and the thyroid cartilage, and enters the larynx (with tlie superior laryngeal a.), through the thyro-hyoid membrane, to be distributed, as a nerve of sensation, to the mucous membrane of the larynx and epi- glottis. The external laryngeal, the smaller, gives off some branches to the pharyngeal plexus, the inferior constrictor, and the thyroid body, and then descends by the side of the larynx beneath the depressors of the os hyoides to supply the crico-thyroid muscle : it communicates with the superior cardiac nerve of the sympathetic. d. The cervical cardiac branches descend behind the sheath of the carotid artery to the cardiac plexus. The upper brandies, one or two in number, are small, and proceed from the ganglion of the trunk ; they join the cardiac branches of the sympathetic and the deep cardiac plexus ; the lower conies from the trunk of the pneumogastric before it enters the chest. Subsequently, the right lower cardiac nerve descends by the side of the innominate artery to join the deep cardiac plexus ; the left passes over the arch of the aorta to join the superficial cardiac plexus. e. The inferior- or recurrent laryngeal nerve turns, on the right side, under the subclavian artery (p. 113), and ascends obliquely inwards to the larynx behind the common carotid and the inferior thyroid arteries : it lies subsequently in the groove between the oesophagus and the trachea. On the left side, it turns under the arch of the aorta, just on the outer side of the remains of the ductus arteriosus ; after which it runs up between the trachea and 1 A branch from the plexus is described by Luschka as receiving filaments from the pharyngeal branches of the glosso-pharyngeal and pneumogastric nerves, and joining with the hypoglossal as it winds round the occipital artery. SPINAL ACCESSORY NERVE. 149 the oesophagus. On both sides the nerves enter the larynx beneath the lower border of the inferior constrictor, and supply all the intrinsic muscles of the larynx, except the crico-thyroid. These nerves as they turn under their respective vessels give off cardiac branches to the deep cardiac plexus. They supply also filaments to the trachea, oesophagus, and inferior constrictor muscle. The remaining branches of the pneumogastric nerve to the lungs, heart, oesophagus and stomach will be examined in the dissection of the chest. SPINAL ACCES- The spinal accessory nerve issues through the SORT NERVE. middle part of the foramen jugulare, in a sheath of dura mater common to it and the pneumogastric nerve. It arises by numerous filaments from the side of the medulla oblon- gata below the pneumogastric, and from the lateral column of the spinal cord as low down as the sixth cervical vertebra. The fila- ments which arise from the medulla oblongata join to form the accessory portion of the nerve ; the spinal filaments ascend between the ligamentum denticulatum and the posterior roots of the cervical spinal nerves, and form the spinal portion of the nerve. These por- tions converge to the jugular foramen, where they communicate with each other more or less, and are then continued onwards below the jugular foramen as two portions the internal or accessory, which joins the pneumogastric n. ; the external or spinal which is distributed to muscles. The accessory, part, within the foramen jugulare, sends one or more filaments to the ganglion of the root of the pneumogastric. It lies close to the pneumogastric nerve at the ganglion of the trunk, and is finally incorporated with the nerve below the ganglion. It sends filaments to the pharyngeal and superior laryngeal branches of the pneumogastric. The spinal part separates from the accessory part below the foramen jugulare. It then takes a curved course backwards and outwards, lying in front of the internal jugular vein and the trans- verse process of the atlas, and behind the digastric and stylo-hyoid muscles. It pierces the upper part of the sterno-mastoid muscle accompanied by the superior sterno-mastoid artery, a branch of the occipital, and supplies the muscle, joining in its substance with 150 SYMPATHETIC NERVE IN THE NECK. branches from the third cervical n. The nerve then crosses obliquely the occipital triangle, where it communicates with the second and third cervical nerves. It is eventually distributed to the under aspect of the trapezius, where it is joined by branches from the third and fourth cervical nerves. HYPOGLOSSAL This nerve arises, by from ten to fifteen filaments, NEEVE. from the groove between the anterior pyramid and the olivary body. It passes through the dura mater in two fasciculi, which emerge from the skull through the anterior condylar fora- men, and then unite to form a single nerve. It comes forward between the internal jugular vein and the internal carotid artery, where it is intimately connected with the pneumogastric nerve. Its further course has been described (p. 103). In the anterior condylar foramen the hypoglossal gives off a small filament to the diploe and to the dura mater around the fora- men magnum. At the base of the skull it gives off several branches, which connect it with the ganglion of the trunk of the pneumo- gastric nerve. These two nerves are sometimes almost inseparably united. It gives off also several delicate filaments to the superior cervical ganglion of the sympathetic, and communicates with the loop formed by the first two spinal nerves in front of the atlas. SYMPATHETIC Now examine the cervical ganglia of the sym- NEBVE. pathetic system of nerves. This system consists of a series of ganglia arranged on each side of the spine, from the first cervical to the last sacral vertebra. The successive ganglia of the same side are connected by intermediate nerves, so as to form a continuous cord on each side of the spine : this constitutes what is called the trunk of the sympathetic system, and is connected with all the spinal nerves. Its upper or cephalic extremity enters the cranium through the carotid canal, surrounds the internal carotid artery, communicates with the third, fourth, fifth, and sixth cranial nerves, and joins its fellow of the opposite side upon the anterior communicating artery. 1 Its sacral extremity joins its fellow by means of the little ganglion impar, situated in the mesial line, upon the coccyx. The ganglia are connected together by branches composed of 1 Here is situated the so-called ganglion of Ribes. SYMPATHETIC NERVE IN THE NECK. 151 grey and white nerve-fibres ; they are also connected with the spinal nerves by two filaments one, of white nerve-fibres which passes from the spinal nerve to the ganglion ; the other, of grey, from the ganglion to the spinal nerve. Branches of distribution are also given off by the ganglia, some to the various blood-vessels and viscera, forming intricate plexuses upon them ; others to the various ganglia of the viscera the cardiac and semilunar ganglia. The different portions of the sympathetic gangliated cord re- ceive, respectively, the distinguishing names of the cervical, dorsal, lumbar, sacral, and coccygeal. At present we have only to consider the cervical portion of it. To expose the cervical ganglion of the sympathetic, the internal carotid artery, the pneumogastric, glosso-pharyngeal and hypo- glossal nerves should be cut through, near the base of the skull ; then by careful dissection the superior cervical ganglion can be traced out. CEBVICAL GAN- ^ n ^ ne cervical portion of the "sympathetic are QUA OF SYMPA- three ganglia, named from their position,' superior, THETIC - middle, and inferior. The superior cervical ganglion, the largest of the three, is situated near the base of the skull, opposite the second and third cervical vertebrae, upon the rectus capitis anticus major, and lies behind, and on the inner side of the internal carotid artery. It is of a reddish-grey colour like the other ganglia, of an elongated oval shape, varying in length from one to two inches. To facilitate the description of its several branches', we divide them into an upper, a lower, an external, an internal, and an anterior set a. Its tipper or cranial branch runs with the internal carotid a. into the carotid canal of the temporal bone, and there divides into two branches, an outer and an inner. The outer and larger branch accom- panies the artery through its bony canal, ramifies upon it by the side of the body of the sphenoid, and so constitutes the ' CAROTID PLEXUS.' ! Trom this outer branch a filament proceeds to the Gasserian ganglion ; another to the sixth cranial nerve ; a third joins the great petrosal 1 A small ganglion, the carotid ganglion, is sometimes met with in this plexus on the under aspect of the artery. 152 SYMPATHETIC NERVE IN THE NECK. branch of the facial, and forms the Vidian nerve, and thus communicates with the spheno-palatine ganglion. It also communicates in the carotid FIG. 36. N. to great petrosal . . N. to lesser petrosal . . N. to Eustachian tube . Ns. to carotid plexus . Chorda tympani . . . N. to stylo-liyoid . . N. to digastricus . . Petrous ganglion . . Carotid plexus . . . Branch to pharyngeal plexus Lingual branch . . . Ganglion of the trunk . Pharyngeal n. . Superior laryngeal Crangliform enlarge- ment. N. to fenestn ovalis. N. to fenestra ro- tunda. Tympanic n. Auricular n. Glosso-pharyngeal n. Jugular ganglion of do. Pneumogastric. Ganglion of root. Spinal accessory. Hypoglossal. Supr. cervical gn- glion. 1st cervical n. Br. to ganglion of trunk. 2nd cervical n. DIAGEAM OF THE COMMUNICATIONS OF THE FACIAL, GLOSSO-PHABYNGEAL, PNEUMO- GASTBIC, SPINAL ACCESSORY, HYPOGLOSSAL, SYMPATHETIC, AND IHE TWO UPPE* CEIiVICAL NEEVES. 1. Great petrosal nerve. 2. Lesser do. 3. External do. 4. Nerve to Stapedins muscle. 5. Spheno-palatine ganglion. 6. Otic ganglion. canal with the tympanic branch of the glosso-pharyngeal. The inner branch, running on with the artery to the cavernous sinus, there forms another plexus, called from its position the 'CAVERNOUS PLEXUS.' SYMPATHETIC NERVE IN THE NECK. 153 Here the sympathetic is seen to communicate with the third, the fourth, and the ophthalmic branch of the fifth and sixth cranial nerves, and with the ophthalmic ganglion. Lastly, from both these plexuses secondary plexuses proceed, of which the minute filaments ramify on, and supply the coats of, the terminal branches of the internal carotid. b. The lower branch descends and joins the middle cervical ganglion of the sympathetic. c. The external branches are numerous, and connect the ganglion with the ganglion of the pneumogastric and hypoglossal nerves, and with the four upper cervical spinal nerves. A small twig also joins the petrosal ganglion of the glosso-pharyngeal and the upper ganglion of the pneumogastric in the foramen jugulare. d. The internal branches are distributed to the pharynx, larynx, and the heart. The pharyngeal branches join the pharyngeal plexus on the middle constrictor of the pharynx : the laryngeal join the superior laryngeal nerve ; the cardiac nerves, one or more in number superior cardiac descend behind the sheath of the carotid in front of the inferior thyroid artery and recurrent laryngeal nerve, and, entering the chest, join the superficial and deep cardiac plexuses. e. The anterior branches lie in front of the external carotid artery and ramify around this vessel and its branches, forming the various plexuses, and named, on account of their delicacy, the nervi molles. In some of these plexuses are occasionally seen several ganglia, the in- tercarotic, 1 lingual, temporal, and pharyngeal ganglia. They are con- nected with the several ganglia about the head and neck ; namely, the ophthalmic, spheno-palatine, otic, and submaxillary. The middle cervical ganglion, the smallest of the three ganglia, is something less than a barleycorn in size. It is situated behind the carotid sheath, about the fifth or sixth cervical vertebra, on or near the inferior thyroid artery. a. It is connected by branches with the superior ganglion above, and with the inferior cervical ganglion below. b. Its external branches usually pass outwards to join the fifth and sixth cervical spinal nerves. c. Its internal branches are distributed to the thyroid body and the heart. The branches to the thyroid body accompany the inferior thyroid 1 Situated in the angle at the bifurcation of the common carotid into the external and internal carotid arteries ; it corresponds in structure with the coccygeal gland. 154 SYMPATHETIC NERVE IN THE NECK. artery, and join the superior cardiac nerve, and in the gland they com- municate with the external and recurrent laryngeal nerves. The middle cardiac nerve, the largest of the three cardiac nerves, descends, on the right side behind the common carotid a., usually in front of the first part of the subclavian artery, into the chest, when it lies on the trachea. It is joined by some cardiac filaments from the recurrent laryngeal nerve and superior cardiac nerve, and joins the deep cardiac plexus. On the left side this cardiac nerve enters the chest between the left carotid and subclavian arteries. In cases where the middle cervical ganglion is absent, the pre- ceding nerves are supplied by the sympathetic cord connecting the superior and inferior ganglia. The inferior cervical ganglion is of considerable size, and is situated in the interval between the base of the transverse process of the seventh cervical vertebra and the neck of the first rib, im- mediately behind the vertebral artery, and to the inner side of the superior intercostal artery. Not infrequently it is coalesced with the first dorsal sympathetic ganglion. Its branches are as follow : a. Superior brandies which pass upwards and connect it with the middle cervical ganglion. b. Inferior Ranches which descend, some in front of, and some behind, the subclavian a., to join the first dorsal ganglion. One of these, the inferior cardiac nerve, passes behind the subclavian a. in front of the trachea, to join the deep cardiac plexus, beneath, the arch of the aorta, and communicates with the recurrent laryn- geal and middle cardiac nerves. c. External branches which communicate with the seventh and eighth cervical nerves ; others form a plexus around the verte- bral artery, which join with the fourth, fifth, and sixth cervical nerves. DISSECTION OF THE THORAX. Before the several organs contained in the thorax are examined, the student should have some knowledge of its framework. The ribs with their cartilages describe a series of arcs increasing in length from above downwards, and form, with the dorsal vertebra? behind and the sternum in front, a barrel of a conical shape, broader in the lateral than in the antero-posterior diameter. The spaces between the ribs are occupied by the intercostal muscles. In each intercostal space there are two layers of these muscles, arranged like the letter X. The fibres of the outer layer run obliquely from above downwards and forwards ; those of the inner layer in the reverse direction. The base is closed in the recent state by a muscle the diaphragm which forms a muscular par- tition between the chest and the abdomen. This partition is arched upwards, so that it constitutes a vaulted floor for the chest, and by its capability of alternately falling and rising, it increases and diminishes the capacity of the thorax. In front, the diaphragm is attached to the ensiform cartilage, but it slopes posteriorly, to become attached to the last rib. The cir- cumference of the diaphragm is convex and muscular ; in the centre it is flattened and aponeurotic. On the right side it corresponds, in front, with the upper border of the cartilage of the fifth rib ; on the left side it corresponds with the upper border of the sixth rib. The upper opening of the osseous thorax is bounded posteriorly by the body of the first dorsal vertebra, laterally by the first ribs, and in front by the upper border of the manubrium sterni. 1 1 That the student may have some knowledge of the diameters of the chest at different situations, the following measurements have been taken from a well- articulated male skeleton of the average height : The antero-posterior diameter at the upper opening of the thorax is 2^ inches, at the articulation of the manubrium 156 DISSECTION OF THE THORAX. Such, in outline, is the framework of the thorax, which con- tains the heart with its large vessels and the lungs. Its walls are FIG. 37. FORM OF THE LUNGS, AND THE EXTENT TO WHICH THEY OVERLAP THE HEART AND ITS VALVES. composed of different structures bone, cartilage, muscles, and ligaments, which fulfil two important conditions : 1st, by their with the gladiolus it is 4 inches, and at the junction of the gladiolus with the ensiform cartilage it has increased to 5-f inches. The transverse diameter of the upper opening was found to be 4| inches ; between the second ribs, 7 inches ; between the third, 8^ inches ; the diameter increased in regular proportion as far as the ninth rib, where it attained a measurement of lOf inches ; below this it gradually decreased. The upper border of the manubrium corresponds to the second dorsal vertebra. The articulation of the manubrium and the gladiolus is on a level with the fourth dorsal vertebra ; and, lastly, the junction of the ensiform cartilage with the gladiolus is on a level with the border of the ninth or tenth dorsal vertebra. DISSECTION OF THE THORAX. 157 solidity and elasticity they protect the important organs contained in the thorax ; 2ndly, by their alternate expansion and contraction they act as mechanical powers of respiration. For they can in- crease the capacity of the chest in three directions : in height, by the descent of the diaphragm ; in width, by the rotation of the ribs ; and in depth, by the elevation of the sternum. The chest of the female differs from that of the male in the following points : Its general capacity is less : the sternum is shorter ; the upper opening is larger in proportion to the lower ; the upper ribs are more moveable, and therefore permit a greater enlargement of the chest at its upper part, in adaptation to the condition of the abdomen during pregnancy. The upper opening of the thorax gives passage to the trachea, the oesophagus, the large vessels of the head and neck and upper extremities, viz., the innominate, the left carotid and subclavian arteries, with the left innominate and right subclavian and internal jugular veins, the superior intercostal and internal mammary arteries, the inferior thyroid veins, the sterno-hyoid, sterno-thyroid and longus colli muscles of each side, the pneumogastric, the left recurrent laryngeal, the phrenic and the sympathetic nerves ; the cardiac branches of the sympathetic, and the cardiac branches of the pneumogastric ; also to the anterior branch of the first dorsal nerve as it passes up to join the brachial plexus, the thoracic duct, the thymus gland (in early life), and, lastly, to the apices of the lungs, which, with their pleural coverings, rise up on each side into the neck for about one inch and a half above the first rib ; the interspaces between these various structures being occupied by a dense fibro-cellular tissue, continuous with the deep cervical fascia. The diaphragm, which forms the base of the thorax, is pierced by the following foramina : the aortic opening, for the passage of the aorta, vena azygos major, thoracic duct ; the oesophageal opening for the oesophagus, pneumogastric nerves, and oesophageal branch of the coronaria ventriculi artery ; the foramen quadratum, for the vena cava inferior, a branch of the right phrenic nerve and lym- phatics from the liver ; the right cms transmits the greater and lesser splanchnic nerves ; the -left cms, in addition, transmits the vena 158 TRIANGULARIS STERNI. azygos minor. In front there are the narrow intervals for the passage of the internal mammary arteries. An opening must be made into the chest, by carefully removing the upper four-fifths of the sternum, and the cartilages of all the true ribs. 1 In doing this, care must be taken not to wound the pleura, which is closely con- nected with the cartilages. On one side the internal mammary artery should be dissected ; on the other, removed. In the dissection of the chest let us take the parts in the following order : 1. Triangularis sterni, with the internal mammary artery. 2. Mediastina, anterior, middle, and posterior. 3. Pleura. 4. Position and form of the lungs. 5. Pericardium. 6. Position and relations of the heart. 7. Posterior mediastinum and its contents ; namely, the aorta, the thoracic duct, the vena azygos, the ossophagus, and pneumogastric nerves. 8. Eight and left brachio-cephalic veins and superior vena cava. 9. Course of the phrenic nerves. 10. Course and relations of the arch of the aorta. 11. The three great branches of the arch. 12. Sympathetic nerve. 13. Intercostal muscles, vessels and nerves. 14. Nerves of the heart ; cardiac plexuses. TBIANGULAEIS On the under surface of the sternum and carti- STEKNI. lages of the ribs is a thin flat muscle, named the tricing idaris sterni. It arises from the ensiform cartilage, the lower part of the side of the sternum, and the cartilages of two or three lower true ribs. Its fibres ascend obliquely outwards, and are inserted by fleshy digitations into the lower borders of the car- tilages of the true ribs from the sixth to the second. Its lowest digitation runs transversely outwards, each successive one, how- ever, becomes more oblique, so that the highest one is nearly ver- tical in direction. The muscle is evidently a continuation upwards 1 Those who are more proficient in dissection should not remove the whole of the sternum, but leave a quarter of an inch of its upper part with the first rib attached to it. This portion serves as a valuable landmark, although it obstructs, to a certain extent, the view of the subjacent vessels. INTERNAL MAMMARY ARTERY. 159 of the anterior portion of the transversalis abdominis. Its action is to draw down the costal cartilages, and thus it acts in expiration. Its nerves come from the intercostal nerves, its arteries from the internal mammary. INTERNAL MAM- This artery is given off from the subclavian in MARY AETEBY. the first part of its course opposite the thyroid axis. It passes down behind the clavicle, and on entering the chest it lies between the cartilage of the first rib and the pleura, and is crossed by the phrenic nerve. It then descends perpendicularly, about half an inch from the sternum, lying on the pleura and behind the costal cartilages ; lower down it gets between the carti- lages of the ribs and the triangularis sterni, as far as the seventh costal cartilage, where it divides into two branches, the musculo- plirenic and the superior epigastric. The latter branch then enters the wall of the abdomen behind the rectus abdominis, and finally inosculates with the deep epigastric (a branch of the external iliac). The branches of the internal mammary are as follows : a. Arteria comes nervi phrenici. A very slender artery, which accompanies the phrenic nerve between the pleura and pericardium to the diaphragm, and anastomoses with the phrenic branches of the abdominal aorta, and internal mammary. b. Mediastinal, pericardiac, sternal, and thymic. These branches supply the cellular tissue of the anterior mediastinum, the pericardium, and the triangularis sterni. The thymic are only visible in childhood, and disappear with the thymus gland. c. Anterior intercostal. Two for each intercostal space are distributed to the five or six upper intercostal spaces. They pass outwards, and lie at first between the pleura and the internal intercostal muscle, and subsequently between the two intercostals. They inosculate with the intercostal arteries from the aorta. d. The perforating arteries pass through the same number of inter- costal spaces as the preceding branches, and supply the pectoral muscle and skin of the chest. In the female they are of large size (especially the third), to supply the mammary gland. e. The mi(culo-j)krenic branch runs outwards behind the cartilages of the false ribs, pierces the attachment of the diaphragm, and termi- nates near the last intercostal space. It supplies small branches to the 160 PLEURA. diaphragm, to the sixth, seventh, and sometimes the eighth intercostal spaces. Two venas comites accompany the artery, and form a single trunk at the upper part of the chest, which terminates in the brachio-cephalic vein of its own side. LYMPHATIC There are several lymphatic glands in the neigh- GIANDS. bourhood of the internal mammary artery. They receive the lymphatics from the upper part of the abdominal wall, the diaphragm, the inner portion of the mammary gland, and the intercostal spaces. On the right side they terminate in the right lymphatic duct, on the left in the thoracic duct. In disease of the inner portion of the mamma, these glands may enlarge without any enlargement of those in the axilla. As the lungs are constantly gliding to and fro within the chest they are provided with a serous membrane to facilitate their motion. This membrane is termed the pleura. There is one for each lung. Each pleura forms a com- pletely closed sac, and, like all other serous sacs, has a parietal and a visceral layer that is, the first layer lines the containing walls, the latter is reflected over the contained organ or viscus. Its several parts are named after the surface to which they adhere : the parietal layer, which lines the ribs and intercostal muscles, is called pleura costalis ; the visceral layer, which invests the lungs, pleura pulmonis ; between these two layers is a space which is termed the cavity of the pleura. Each pleura occupies its own half of the thorax ; they do not communicate with one another, nor do they come into contact with each other, except for the short distance of about two inches in front, behind the sternum. Unlike the peritoneum, the pleura forms no folds except a small one, called ligamentum latum pulmonis, which extends from the root of the lung to the diaphragm. The pleura costalis (fig. 38), in front, lines part of the back of the sternum and the inner surfaces of the costal cartilages ; later- ally, it is reflected over the ribs and the intercostal muscles ; pos- teriorly, it is traced over the sides of the bodies of the dorsal vertebrae ; thence it passes to the back of the pericardium, over the PLEURA. 161 posterior aspect of the root of the lung. It may now be traced, as the pleura pidmonalis, over the surface of the lung, to which it is intimately adherent, into the fissures between the lobes, as far as the anterior border of the lung ; thence round its pericardial aspect Internal mam- mary a. . . Phrenic n. Internal mam- mary a. Phrenic n. (Esophagus with pneumogastric n. Aorta. DIAGBAM OF THE REFLECTIONS OF THE PLEURAL SACS IN DOTTED LINES. to the front of the root of the lung, passing forwards over the pericardium to the back of the sternum. Its only reflection, the ligamentum latum pulmonis, has been already alluded to. Below, the pleura covers the diaphragm. The pleura rises as a conical dome into the base of the neck, about an inch above the first rib, and is strengthened in this situation by expansions from the scaleni muscles. 1 The thickness of the pleura differs : on the lung it is thin, semi-transparent, and firmly adherent ; on the ribs and diaphragm it is thick, and may be easily separated from its osseous and muscular connections. 2 1 A slip is described by Sibson as passing from the transverse process of the last cervical vertebra, and, spreading out, is inserted into the pleural dome and the inner margin of the first rib. 2 From the prevertebral fascia, a ligamentous band passes downwards along the inner border of the lung to be attached to the pericardium and the central M 162 MEDIASTINA. The spaces called anterior and posterior mediastind, formed by the separation of 'the pleurae, will be described further on. In health the internal surface of the pleura is smooth, polished, and lubricated by moisture sufficient to facilitate the sliding of the lung. 1 When this surface is thickened and roughened by inflammation, the moving lung produces a friction sound. When the pleural sac is distended by serum, it constitutes hydro-thorax ; when by pus, empyema ; when by air, pneumo-thorax ; when by blood, haemo-thorax. Introduce your hand into the pleural sac, and ascertain that the reflection of the pleura on to the diaphragm corresponds with an imaginary line commencing at the lower part of the sternum, and sloping along the cartilages of the successive ribs down to the lower border of the last rib. Supposing a ball to lodge in the pleural sac, it might fall upon the dome of the diaphragm, and roll down to the lowest part of the pleural cavity. The place, therefore, to extract it, would be in the back, at the eleventh intercostal space. This operation has been done during life with success. If a transverse section were made through the chest (see fig. 38), you would observe that as the pleuraa nowhere come into actual contact, a space is left between them extending from the sternum to the spine, and which is larger in the middle than in front or behind. This interval is called by anatomists the in- terpleural space or the mediastinum, and for convenience sake is subdivided into three parts an anterior, middle, and posterior mediastinum. MEDIASTINA, The mediastina are the spaces which the two ANTERIOR, MIDDLE pleural sacs leave between them in the antero- AND POSTERIOR. posterior plane of the chest, and which contain all the thoracic viscera except the lungs. There is an anterior, a middle, and a posterior mediastinum. To put these spaces in the tendon of the diaphragm. As it passes downwards it embraces the root of the lung, and supports it in its proper position. This band has been described as the ' suspensory ligament of the diaphragm,' by Teutleben. 1 The pleura costalis is covered with flattened epithelial cells ; the pleura pulmonalis with polyhedral granular cells. (Klein.) MEDIASTINA. 163 FIG. 39. simplest light, let us imagine the heart and lungs to be removed from the chest, and the two pleural sacs to be left in it by them- selves. The two sacs, if in- flated, would then appear like two bladders, in contact only in the middle, as shown by the dotted outlines in the annexed scheme (fig. 39). The interval marked a, behind the sternum, would represent the anterior mediastinum; the interval &, the posterior mediastinum. Now let us introduce the heart again, between the two pleural sacs : these must give way to make room for it, so that the two sacs are largely separated in the middle line of the chest ; and the space thus occupied by the heart and large vessels takes the name of the middle mediastinum. Looking at the chest in front, the anterior mediastinum appears as shown in the diagram (fig. 40). It is not precisely vertical in its direction, for it inclines slightly towards the left, owing to the position of the heart. Its area varies : thus it is very shallow from before backwards; it is extremely narrow in the middle where the edges of the lungs nearly meet ; it is wider above, and widest of all below, where the lungs diverge. Posteriorly it is limited by the pericardium covering the heart, aorta and its branches, and the pulmonary artery. What parts are contained in the anterior mediastinum ? The remains of the thymus gland, the origins of the sterno-hyoid, sterno-thyroid, and triangularis sterni muscles, the left brachio- cephalic vein (which crosses behind the first bone of the sternum), a few lymphatic glands, and the left internal mammary artery and vein. The posterior mediastinum (fig. 38) is triangular in shape, placed in front of the dorsal vertebrae : it contains the oesophagus, the two pneumogastric nerves, the descending aorta, the thoracic duct, the greater and smaller azygos veins, the left superior intercostal M 2 164 MEDIASTINA. vein, and some lymphatic glands. This space will be described in detail at a later stage. The middle mediastinum is the largest of the mediastina, and contains the heart enclosed in the pericardium, the vena cava superior, the ascending aorta, the pulmonary arteries and veins, the phrenic nerves with their accompanying arteries, and the bifurcation of the trachea. FIG. 40. FOBM 01- THE LUNGS, AND THE EXTENT TO WHICH THHY OVEBLAP THE HEART AND ITS VALVES. A superior mediastinum has also been described comprising that part of -the interpleural space which lies above a horizontal plane, extending behind from the lower part of the body of the fourth dorsal vertebra to the articulation between the manubrium and gladiolus in front. The contents of this mediastinum include all PLEURA. 165 those structures found above this nearly horizontal plane, and are the transverse portion of the arch of the aorta and its three large branches, the trachea, oesophagus, and thoracic duct, the inno- minate veins, superior vena cava, left recurrent laryngeal nerve, phrenic, pneumogastric, and cardiac nerves, lymphatic glands, and the thymus or its remains. Before passing to the dissection of the contents of the thorax, the student should carefully trace the outline of the free borders of the pleurae as seen in the front of the chest. As the margins of the lungs for all practical purposes correspond with the borders of the pleurae, we shall confine our description to the more important of the two structures, viz. the lungs. The value of this investi- gation is, that we are enabled to trace upon a living chest the outlines of the lungs, and know what parts are naturally resonant on percussion. Commencing from above (fig. 40, p. 164), we find that the apex of the lung extends into the neck, from an inch to an inch and a half above the clavicle. This part of the lung ascends behind the subclavian artery and the scalenus anticus muscle, and deserves especial attention",' because it is, more than any other, the seat of tubercular disease. From the sternal end of the clavicles the lungs converge towards the middle line, where their borders nearly meet opposite the junction of the second rib. There is thus little or no lung behind the manubrium sterni. From the level of the second costal cartilage to the level of the fourth, the inner margins of each lung run nearly parallel and almost in contact behind the middle of the sternum ; consequently they overlap the great vessels at the root of the heart. Below the level of the fourth costal cartilage the margins of the lungs diverge from each other, but not in an equal degree. The left presents the notch for the heart, and follows nearly the course of the fourth costal cartilage ; at the lower part of its curve it projects more or less over the apex of the heart like a little tongue. The right descends almost perpendicularly behind the sternum as low as the attachment of the ensiform cartilage, and then turning outwards corresponds with the direction of the sixth costal cartilage. Hypertrophy of the heart, or effusion into the 166 POSITION OF THE LUNGS. pericardium, will not only raise the point where the lungs diverge above the ordinary level, but also increase their divergence ; hence the greater dulness on percussion. POSITION AND The two lungs are situated in the chest : each FORM OF THE LUNGS, in its own half of the thorax, with the heart, enclosed in its pericardium, between them. Each fits accurately into the cavity which contains it. Each, therefore, is conical in form ; the apex projects into the root of the neck, a little more than an inch above the sternal end of the clavicle ; the base is broad and rests on the diaphragm, the posterior part being thin and extending as far as the eleventh rib. Its outer surface is con- vex and adapted to the ribs ; its inner surface is excavated, to make room for the heart in front ; and behind presents a deep fissure liilum pulmonis for the attachment of the root of the lung. Its posterior surface is convex, and fits into the concavity of the thorax, on each side of the spinal column. The best way to see the shape of the lungs is to inject them through the trachea with wax. which is tantamount to taking a cast of each thoracic cavity. In such a preparation, besides the general convexities and concavities alluded to, you would find in the right lung a little indentation for the right brachio-cephalic vein ; in the left an indentation for the arch of the aorta and the left subclavian artery. Each lung is divided into an upper and a lower lobe by a deep fissure, which commences, behind, about three inches from the apex, and proceeds obliquely downwards and forwards to the junc- tion of the sixth rib with its cartilage (fig. 40). Speaking broadly, nearly the whole of the anterior portion of the lung is formed by the upper lobe; nearly the whole of the posterior portion by the lower lobe. It should be noticed, however, that the upper lobe of the right lung is divided by a second fissure which marks off, from its lower part, a triangular portion called its middle lobe. The dimensions of the right lung are greater than those of the left in all directions except the vertical ; the reason of this excep- tion is the greater elevation of the diaphragm on the right side by the liver. On an average the right lung weighs 24 ounces, the left 21 ounces. POSITION OF THE HEART. 167 The constituents of the root of the lung will be described hereafter when they can be more satisfactorily displayed. PB^COEDIAL The prcecordial region is the outline of the EEGION. heart traced upon the front wall of the chest. It is important for auscultatory purposes that we should know how much of the heart is covered and separated from the wall of the chest by intervening lung (fig. 40). The following will give a fair indication :- ' Make a circle of two inches in diameter round a point midway between the nipple and the end of the sternum. This circle will define, sufficiently for all practical purposes, that part of the heart which lies immediately behind the wall of the chest, and is not covered by lung or pleura.' l This part of the praecordial region is naturally less resonant to percussion, for it is here uncovered, except by pericardium and loose connective tissue, and lies close behind the thoracic wall. In the rest of the praecordial region the heart is covered and separated from the chest wall by intervening lung. Where should we put the stethoscope when we listen to the valves of the heart ? For practical purposes it is enough to remember that the mouth of an ordinary-sized stethoscope will cover a portion of them all, if it be placed a little to the left of the mesial line of the sternum opposite the third intercostal space (fig. 40, p. 164). They are all covered by a thin portion of lung ; for this reason we ask a patient to stop breathing while we listen to his heart. POSITION AND The heart is situated obliquely in the chest, FORM OF THE between the lungs. Its base, i.e. the part by HEART, which it is attached, and from which its great vessels proceed, is directed upwards towards the right shoulder ; its apex points downwards and to the left, between the fifth and sixth costal cartilages. It is supported, towards the abdomen, by the tendinous centre of the diaphragm. It is maintained in its posi- tion by a membranous bag termed the pericardium, which is lined by a serous membrane to facilitate its movements. The pericar- dium must first claim our attention. 1 Latham's Clinical Lectures. 168 THE PERICARDIUM. The pericardium is the conical membranous bag which encloses the heart and the large vessels at its base. It is broadest below, where it is attached to the tendinous centre of the diaphragm, and to the muscular part in connection FIG. 41. RELATIVE POSITION OF THE HEART AND ITS VALVES WITH REGARD TO THE WALLS OF THE CHEST. The valves are denoted by curved lines. The aortic valves are opposite the third intercostal space on the left side, close to the sternum. The pulmonary valves are just above the aortic, opposite the junction of the third rib with the sternum. The mitral valves are opposite the third intercostal space, about one inch to the left of the sternum. The tricuspid valves lie behind the middle of the sternum, about the level of the fourth rib. Aortic murmurs, as shown by the arrow, are propagated up the aorta : mitral murmurs, as shown by the arrow, are propagated towards the apex of the heart. with the tendon, further to the left side than to the right ; above, it is prolonged over the great vessels of the heart, about two inches from their origin, and is connected with the deep cervical fascia. On each side, it is in contact with the pleura ; the phrenic nerve THE PERICARDIUM. 169 running down between them. In front of it, is the anterior media- stinum ; behind it, is the posterior. Of the objects in the poste- rior mediastinum, that which is nearest to the pericardium is the oesophagus and the left pneumogastric nerve. It should be re- membered that the oesophagus is in close contact with the back of the pericardium and left auricle for nearly two inches ; this fact ac- counts for what is sometimes observed in cases of pericarditis where there is much eifusion : namely, pain and difficulty in swallowing. The pericardium is a fibro-serous membrane, and consists of two layers an external or fibrous, and an internal or serous. Its fibrous layer, a dense membrane, constitutes its chief strength, and is attached, below, to the central tendon and the adjoining muscular part of the diaphragm. Above, it forms eight tubular sheaths for the great vessels at the base of the heart ; namely, one for the vena cava superior, four for the pulmonary veins, two for the pulmonary arteries, and one for the aorta. The serous layer forms a shut sac. Its parietal layer lines the fibrous layer to which it is intimately attached, and is reflected over the great vessels and the heart to form its visceral layer. To see where the serous layer is reflected over the vessels, distend the pericardium with air. Thus you will find that this layer is reflected over the aorta as high as the com- mencement of the transverse portion of the arch of the aorta. It is reflected over the front and sides of the vena cava superior. The serous layer of the pericardium covers the large vessels to an extent greater than is generally imagined ; though the extent is not precisely similar in all bodies. The aorta and pulmonary artery are enclosed in a complete sheath, two inches in length, so that these vessels are covered all round by the serous layer, except where they are in contact. Indeed you can pass your finger behind them both, through a foramen bounded, in front, by the two great vessels themselves ; behind, by the upper part of the auricles ; and above, by the right pulmonary artery. Again, the back of the aorta, where it lies on the auricles, is covered by the serous pericardium. The superior cava is covered all round, except behind, whore it crosses the right pulmonary artery. The inferior cava within the pericardium is partly covered in front. The left pulmonary veins are covered nearly all round ; the right less so. Behind the 170 POSITION OF THE HEART. auricles, chiefly the left, the serous layer extends upwards in the form of a pouch, rising above their upper border, so as to be loosely connected to the left bronchus. The object of these serous reflec- tions is to facilitate the free action of the heart and the great vessels at its base. In the healthy state, the capacity of the pericardium nearly corresponds to the size of the heart when distended to its utmost. The healthy pericardium, with the heart in situ, may be made to hold, in the adult, about ten ounces of fluid. The pericardium is not extensile. When an aneurism bursts into it, death is caused, not by loss of blood, but by compression of the heart in consequence of the inextensibility of the pericardium. The pericardium derives its blood from the internal mammary, bronchial, and cesophageal arteries; its nerve-supply from the phrenic nerves. On separating the left pulmonary artery and pulmonary vein, you will notice a fold of serous membrane about three-quarters of an inch long and about one inch in depth : this is the vestigial fold of tlie pericardium, described by Marshall. 1 It passes from the side of the left auricle, curving round the lower left pulmonary vein, to the left superior intercostal vein. It is a vestige of the left v. c. superior (duct of Cuvier) which exists in foetal life. Open the pericardium, and observe that the heart is conical in form, and convex everywhere except upon its lower surface, which is flat, and rests upon the tendinous centre of the diaphragm. When the pericardium is thus laid open, the following objects are exposed: viz. 1. Part of the right ventricle; 2. Part of the left ventricle ; 3. Part of the right auricle with its appendix over- lapping the root of the aorta ; 4. The appendix of the left auricle overlapping the root of the pulmonary artery ; 5. The aorta ; 6. The pulmonary artery ; 7. The vena cava superior; 8. The right and left coronary arteries. POSITION OF ^h 6 heart, then, placed behind the lower half THE HEABT of the sternum, occupies more of the left than the CONTINUED. riht llal f Q f th 1 ' On the Development of the Great Anterior Veins in Man and Mammalia, Pliilosopli. Transactions, 1850. POSITION OF THE HEART. 171 dinous centre of the diaphragm, which is a little below the lowest part of the fifth rib. At each contraction the apex of the heart may be felt beating between the cartilages of the fifth and sixth ribs, about two inches below the nipple and an inch to its sternal side, or about three and a half inches to the left of the middle of the sternum. Speaking broadly, the base corresponds with a line drawn across the sternum along the upper borders of the third costal cartilages. The right border of the heart is formed almost Entirely by the free margin of the right auricle, and, when dis- tended, bulges nearly an inch to the right of the sternum. The left border of the heart is formed by the round border of the left ventricle, and reaches from a point, commencing at the second left intercostal space, to a point placed two inches below the nipple and an inch to its sternal side. The horizontal border is formed by the sharp margin of the right ventricle, and extends from the sternal attachment of the fifth right costal cartilage, to meet the lowest point of the left margin. The normal position which the cardiac valves hold to the thoracic walls is difficult to define with precision, and this pro- bably accounts for the discrepancies noticed in anatomical works on this subject. The following relations are the results of care- fully made observations in the post-mortem room : The right auricula-ventricular valves are situated behind "the sternum on the level of the fourth costal cartilage; the left auricula-ventri- cular valves are opposite the third intercostal space, about one inch to the left of the sternum ; the cusps of these valves extend as low as the fifth costal cartilage. The pulmonary valves lie immediately behind the junction of the third left costal cartilage with the ster- num ; the aortic valves are on a level with the upper border of the third intercostal space just at the left of the middle line of the sternum. 1 The position of the heart varies a little with the position of the body. Of this anyone may convince himself by leaning alter- nately forwards and backwards, by lying on this side and on that, placing at the same time his hand upon the prsecordial region. 1 Anatomists differ much in the description they give of the relations of the valves to the thoracic walls : in fact no two agree in all the details. 172 BRACHIO-CEPHALIC VEINS. He will find that he can, in a slight degree, alter the place and the extent of the impulse of the heart. Inspiration and expira- tion also alter the position of the heart. In inspiration the heart descends with the tendinous centre of the diaphragm about half an inch. The student should now make out the large vessels in con- nection with the base of the heart, leaving the consideration of this organ to a later stage of the dissection. Before we can display the bracbio-cephalic veins, the layer of the deep cervical fascia must be removed which descends over them from the neck and is lost upon the pericardium. Their coats are intimately connected with this fascia; and one of its functions appears to be to keep the veins permanently open for the free return of blood to the heart. BRACHIO- The right and left brachio-cephalic (innomin- CEPHALIC VEINS. ate) veins are formed, near the sternal end of the clavicle, by the confluence of the internal jugular and subclavian veins. They differ in their course and relations, and must, there- fore, be described separately. The left brachio-cephalic vein passes from the left side obliquely behind the first bone of the sternum, the sterno-hyoid and thyroid muscles, the remains of the thymus gland, towards the right side, to form with the right innominate vein the vena cava superior (fig. 42). It is about three inches in length, and its direction inclines a little downwards. It is larger than the right brachio-cephalic, and crosses over the trachea and the origins of the three primary branches of the arch of the aorta. We are reminded of this fact in some cases of aneurism of these vessels for what happens ? The vein becomes compressed between the aneurism and the sternum ; hence the swelling and venous congestion of the parts from which it returns its blood ; namely, of the left arm, and the left side of the neck. The upper border of the vein is not far from the upper border of the sternum : in some cases it lies even higher, and we have seen it crossing in front of the trachea fully an inch above the sternum. This occasional deviation should be borne in mind in the perform- ance of tracheotomy. The right brachio-cephalic vein descends nearly vertically to SUPEKIOR VENA CAVA. 173 join the superior vena cava, opposite the first right intercostal space. It is about an inch and a half in length, and is situated about one inch from the mesial line of the sternum. On its left side, but on a posterior plane, runs the arteria innominata ; on its right side is the pleura. Between the vein and the pleura is the phrenic nerve. The brachio-cephalic veins are not provided with valves. The veins which generally empty themselves into the right and left brachio-cephalic are as follow : The EIGHT B.-C. Vein receives : The vertebral. The internal mammary. The inferior thyroid. The LEFT B.-C. Vein receives :- The vertebral. The internal mammary. The inferior thyroid. The superior intercostal. The pericardiac. The thymic. FIG. 42. Superior intercostal . . Internal mammary . . Venaazygos Middle thyroid. Internal jugular. - - External jugular. Vertebral. ^ ;. x ^ Supra-scapular. Posterior scapular. JB- Subclavian. Internal mammary. Pericardiac and thymic. Left superior inter- costal. SUPERIOR VENA CAVA AND ITS TRIBUTARIES. Opening into the point of junction of the internal jugular and subclavian veins, on the right side is the right lymphatic duct ; on the left side is the thoracic duct. VENA CAVA This is the great vein through which the im- SUPERIOR. pure blood from the head, upper extremities, and chest, returns into the right auricle. It is formed by the junction of the right and left brachio-cephalic veins, which unite at nearly 174 THE AORTA. a right angle opposite the upper part of the first intercostal space on the right border of the sternum ; that is, about the level of the highest point of the arch of the aorta. The vena cava descends vertically, with a slight inclination backwards, to the upper and anterior part of the right auricle. It is from two and a half to three inches long, ' and has no valves. The lower half of it is covered by the pericardium ; you must, therefore, open this sac to see how the serous layer of the pericardium is reflected over the front and sides of the vein. In respect to its relations, notice that the vein lies in front of the right bronchus and the right pulmonary vessels ; and that it is overlapped by the ascending aorta, which lies to its left side. In the upper half of its course, that is, above the pericardium, it is covered on its right side by the pleura ; on this side, in contact with it, descends the phrenic nerve. Before it is covered by the pericardium, the vena cava receives the right vena azygos, which opens into it after hooking over the right bronchus ; also some pericardiac and mediastinal veins. COURSE OF THE The aorta is the great trunk from which all the AORTA. arteries of the body carrying arterial blood are derived. It commences at the upper and back part of the left ventricle of the heart. It ascends forwards and to the right as high as the lower border of the first intercostal space on the right side ; it then arches backwards towards the left side of the body of the second dorsal vertebra, and turning downwards over the left side of the third, completes the arch at the fifth dorsal vertebra. The aorta descends through the thorax on the left side of the bodies of the remaining dorsal vertebras as far as the diaphragm ; it enters the abdomen through the aortic opening of the diaphragm, and descends as far as the left side of the body of the fourth lumbar vertebra, where it bifurcates into the right and left common iliac arteries. The aorta has received different names in the various parts of its course : thus, the arched portion extending from its origin at the left ventricle to the fifth dorsal vertebra, is called the arch of tlie aorfa ; the portion between this vertebra and the diaphragm is the descending thoracic aorta ; and the remainder of its course to its division at the fourth lumbar vertebra is known as the abdominal aorta. ARCH OF THE AORTA. 175 COUBSE AND arc ^ f * ne aorta, as before stated, com- KELATIONS OF THE mences at the upper part of the left ventricle, AKCH OF THE and describes an arch which terminates at the A * fifth dorsal vertebra. Its origin is situated be- FIG. 43. 3rd cervical n. 4th cervical n. Pneumogas- tric n. . . . 5th cervical n. Cervicalis ascendens a. Scaleuus anticus. Inferior thyroid a. Superficialis colli a. Phrenic n. Posterior scapular a. Supra-scapular a. Subclavian a. Superior intercostal a. Internal mammary a. Pneumogastric n. Phrenic n. Appendix of left anrkle. hind the pulmonary artery, and on the left side of the middle of the sternum, about the level of the lower border of the third costal cartilage. The direction of the arch, therefore, is from the sternum to the spine and rather obliquely from right to left. 176 ARCH OF THE AORTA. For convenience of description, the arch of the aorta is divided into an ascending, a transverse, and a descending portion. Ascending portion. To see this portion of the aorta, the peri- cardium must be opened. You then observe that this part of the artery is enclosed all round by the serous layer of the pericardium, except where it is in contact with the pulmonary artery. It is about two inches in length, and ascends with a slight curve, the convexity looking forwards and to the right side, as far as the upper border of the second costal cartilage of the right side, where it lies almost in contact with the sternum. Its commencement is covered by the pulmonary artery, and is overlapped by the appendix of the right auricle, and higher up by the remains of the thymus gland. On its right side, but on a posterior plane, is the superior vena cava and the right auricle ; on its left side, is the pulmonary artery ; behind it, are part of the right auricle, the right pulmonary artery and vein, and the root of the right lung. This part of the arch gives off the right and left coronary arteries for the supply of the heart. The right border of the ascending portion of the arch bulges to the right of the sternum to the extent of a quarter of an inch, and may be seen at the sternal end of the second right intercostal space. The arch of the aorta presents partial dilatations in certain situations. One of these, called the great sinus of the aorta, is observed on the right side of the arch, about the junction of the ascending with the transverse portion : it is little marked in the infant, but increases with age. Three other dilatations (the sinuses of Valsalva), one corresponding to each of the valves at the com- mencement of the aorta, will be examined hereafter. Transverse portion. This portion of the aorta arches from the front to the back of the thorax, and extends from the upper border of the second right costal cartilage to the left side of the third dorsal vertebra. Its highest convex portion ascends usually to about an inch below the upper border of the sternum, and its con- cavity corresponds with the articulation of the first and second bones of the sternum. In front, it is covered by the left pleura and lung, and is crossed by the left phrenic, the left pneumogastric, the superficial cardiac nerves, the pericardiac and the left superior intercostal veins. Near its summit runs the left brachio-cephalic RELATIONS OF THE ARCH OF THE AORTA. 177 vein. Within its concavity, are the left bronchus, the bifurcation of the pulmonary artery, the left recurrent laryngeal nerve, and the remains of the ductus arteriosus. The artery rests upon the trachea (a little above its bifurcation), the deep cardiac plexus, the O3sophagus, the thoracic duct, and the left recurrent laryngeal nerve. From the upper part of the transverse portion of the arch arise the arteria innominata, the left carotid, and the left subclavian arteries ; and lying in front of these arteries is the left-brachio- cephalic vein. Descending portion. This part of the arch lies upon the left side of the body of the fourth dorsal vertebra, and at the lower border of the body of the fourth, or the upper part of the fifth, dorsal it takes the name of the descending thoracic aorta. On its right side, are the oesophagus and thoracic duct ; on its left, is the pleura ; in front, are the pleura and the root of the left lung ; behind, it lies on the anterior common ligament, corresponding to the fourth dorsal vertebra. What parts are contained within the arch of the aorta ? The left bronchus, the right pulmonary artery, the left recurrent nerve, the remains of the ductus arteriosus, and the superficial cardiac plexus of nerves. EELATIONS OF These relations vary according to the size of the THE ARCH OF THE heart, the obliquity of the ribs, and the general AOETA TO THE development of the chest. In a well-formed adult STERNUM. ^g ascending aorta is, at the most prominent part of its bulge, about half an inch behind the first bone of the sternum. The highest part of the arch is about one inch below the upper edge of the sternum. 1 The branches given off from the ascending portion of the arch 1 The relations of the arch of the aorta to the sternum vary even in adults, more especially if there be any hypertrophy of the heart. As an instance among many, we may mention that of a young female who died of phthisis. The position of the aortic valves was opposite the middle of the sternum, on a level with the middle of the second costal articulation. The highest part of the arch was on a level with the upper border of the sternum ; the arteria innominata was situated entirely in front of the trachea ; and the left brachio-cephalic vein crossed the trachea so much above the sternum that it would have been directly exposed to injury in tracheotomy. H 178 INNOMINATE ARTERY. are the right and left coronary arteries, which pass, one in front of, and the other behind, the heart to supply its muscular tissue. The right coronary artery arises from the anterior sinus of Val- salva, and passes to the right between the pulmonary artery and the right auricular appendix, running in the auriculo-ventricular groove. The left coronary artery, larger than the preceding, is given off from the left posterior sinus of Valsalva, and passes between the pulmonary artery and left auricular appendix ; it runs down in the anterior interventricular sulcus towards the apex of the heart. The further description of these vessels will be considered in the dissection of the heart. From the highest part of the arch arise three large arteries for the head, neck, and upper limbs ; namely, the brachio-cephalic or innominate artery, the left carotid, and the left subclavian. BRACHIO-CEPHA- This, the largest of the three, arises from the LIC OK INNOMINATE commencement of the transverse part of the arch. ARTEHY. j^ ascends obliquely towards the right, and, after a course of about one inch and a half to two inches, divides behind the right sterno-clavicular joint into two arteries of nearly equal size the right subclavian and the right common carotid. The relations of the innominate artery are as follow : In front, it has the manubrium sterni, the right sterno-clavicular joint, the origins of the sterno-hyoid and thyroid muscles, the remains of the thymus gland, the left brachio-cephalic vein, the right inferior thyroid vein, and the right inferior cervical cardiac branch of the pneumogastric nerve. Behind, it rests upon the trachea. On its left side, are the left common carotid and the remains of the thymus. On its right side, are the lung and pleura, the right brachio-cephalic vein, and the pneumogastric nerve. 1 With the anatomy of the parts before you, you can understand that an aneurism of the innominate artery might be distinguished 1 In some cases the innominate artery ascends for a short distance above the clavicle before it divides, lying close to the right of the trachea. We have already alluded to the fact that it occasionally gives off a middle thyroid artery (p. 90), which ascends in front of the trachea to the thyroid body, and is therefore directly in the way in tracheotomy. LEFT COMMON CAROTID ARTERY. 179 from an aneurism of the aorta 1. By a pulsation in the neck between the sterno-mastoid muscles, i.e. in the fossa above the sternum; 2. By occasional dyspnrea owing to pressure on the trachea; 3. By venous congestion in the left arm; 4. By the aneurismal thrill being confined to the right arm. 1 LEFT COMMON This artery arises from the arch of the aorta, CAKOTID ABTEBY. close to, and to the left of, the arteria innominata. It ascends obliquely to the left sterno-clavicular joint, and thence to the neck, where its course nearly corresponds with the right common carotid (p. 81). In front, it has the sternum, the left sterno-hyoid and thyroid muscles, the left brachio-cephalic vein, and the remains of the thymus gland ; behind, it has at first the trachea, and higher up the oasophagus and thoracic duct ; to the riglit side, is the innominate artery ; to the left side, are the left subclavian artery and left pneumogastric nerve. LEFT SUBCLA- This is the third branch of the transverse part VIAN AKTEKY. o f the arch, and arises from it opposite the third dorsal vertebra. It ascends nearly vertically out of the chest to the inner border of the first rib, and then curves outwards behind the scalenus anticus. In front, it has the lung covered with pleura, the pneumogastric, phrenic and cardiac nerves, the left common carotid, the left internal jugular and the left innominate veins, the sterno-hyoid, sterno^thyroid, and sterno-mastoid muscles. To its right side, are the left carotid, oesophagus, and trachea ; between the artery and the oesophagus is the thoracic duct ; to its left side, is the lung covered with pleura ; behind it, are the longus colli muscle covering the vertebrae, the oesophagus, thoracic duct, and the inferior cervical ganglion of the sympathetic. The upper part of its course, where the vessel passes in front of the apex of the lung, has been described with the anatomy of the neck (p. 115). 1 If the innominate artery be ligatured, the circulation would be maintained by the following collateral branches : 1. Between the branches of the two exter- nal carotids, which anastomose across the middle line. 2. Between the aortic intercostal and the superior intercostal. 3. Between the aortic intercostals and the internal mammary, long thoracic, alar thoracic, and subscapular arteries. 4. Between the internal mammary and deep epigastric. 5. Between the inferior thyroid arteries. 6. Between the two vertebrals. 7. Between the two internal carotid arteries. N2 180 PHRENIC NERVES IN THE CHEST. COUESE OF THE ^e plivenic nerve comes from the third, fourth, PHRENIC NERVES and fifth cervical nerves, but chiefly from the THROUGH THE fourth. It descends on the scalenus anticus, gradually inclining to its inner border, and enters the chest between the subclavian vein and artery. It then crosses over the internal mammary artery and runs in front of the root of the lung, between the pleura and the pericardium to the diaphragm (fig. 30), to the under surface of which it is distributed. 1 The phrenic nerve is joined on the scalenus anticus by an oifset from the fifth cervical branch of the brachial plexus ; by another filament from the sympathetic nerve ; and very frequently by a small loop from the nerve to the subclavius muscle ; occasionally also by a branch from the descendens noni. In what respects do the phrenic nerves differ from each other in their course ? The right phrenic runs along the outer side of the brachio-cephalic vein and superior vena cava ; the left crosses in front of the transverse part of the arch of the aorta ; besides which, the left is rather longer than the right, since it curves over the apex of the heart. Before the phrenic nerve divides into branches to supply the diaphragm, it sends off minute filaments to the pleura and the pericardium : after it has pierced the diaphragm it distributes branches to the peritoneum. The right phrenic gives off one or two filaments, which unite with some filaments from the solar plexus and form a small ganglion, from which branches are dis- tributed to the supra-renal capsule, the hepatic plexus, and the inferior vena cava. The left phrenic gives off a branch which joins a twig from the sympathetic near the cesophageal opening of the diaphragm, but there is no appearance of a ganglion. Having studied these anatomical details, consider for a moment what symptoms are likely to be produced by an aneurism of the arch of the aorta, or any of the primary branches. A glance at the important parts in the neighbourhood helps to answer the question. The effects will vary according to the part of the artery which is 1 In the Museum of the College of Surgeons there is a dissection showing that the right phrenic nerve enters the diaphragm close to the right side of the vena pava inferior, while the left phrenic enters the left muscle of the diaphragm. THE POSTERIOR MEDIASTINUM. 181 the seat of the aneurism, and according to the size, the form, and the position of the tumour. One can understand that compression of the vena cava superior, or either of the brachio-cephalic veins, would occasion congestion and redema of the parts from which they return the blood ; that compression of the trachea or one of the bronchi might occasion dyspnoea, and thus simulate disease of the larynx ; l that compression of the oesophagus would give rise to symptoms of obstruction. Nor must we forget the immediate vicinity of the thoracic duct and the recurrent nerve, 2 and the effects which would be produced by their compression. Can one, then, be surprised that a disease which may give rise to so many different symptoms should be a fertile source of fallacy in diagnosis ? Thus you can understand how aneurisms of the aorta may prove fatal, by bursting into the contiguous tubes or cavities ; for instance, into the trachea, the oesophagus, the pleura, or the peri- cardium. You will see, too, why an aneurism of the first part of the arch is so much more dangerous than elsewhere. The reason is, that in this part of its course the aorta is covered only by a thin layer of serous membrane. If an aneurism take place here, the coats of the vessel soon become distended, give way, and allow the blood to escape into the pericardium ; an occurrence which is speedily fatal, because, the pericardium being filled with blood, the heart is prevented from acting. POSTERIOR MEDIA- The posterior mediastinum (p. 163) is formed STINUM AND ITS by the reflection of the pleural sac on each side, CONTENTS. from the root of the lung to the sides of the bodies of the dorsal vertebrae. It is boundc d in front by the peri- cardium and the roots of the lungs. To obtain a view of it, cut away the ribs nearly as far as their angles, draw out the right lung towards the left side, and fasten it firmly to the left side of the thorax. Remove the pleura of the right side from the ribs, and the posterior aspect of the root of the right lung, and then by a 1 In the Museum of Guy's Hospital there is a preparation, No. 1,487, in which laryngotomy was performed under the circumstances described in the text. 2 See Med. Gaz., Dec. 22nd, 1843 : a case in which loss of voice was produced by the pressure of an aneurismal tumour upon the left recurrent nerve. 182 DESCENDING THORACIC AORTA. little careful dissection the space and the structures contained in it will be displayed. This mediastinum contains the descending thoracic aorta with some of the right aortic intercostal arteries ; in front of the aorta, the oesophagus, with the pneumogastric nerves, the left in front and the right behind ; on the right of the aorta is the vena azygos major, between this vein and the aorta is the thoracic duct ; superiorly is the trachea ; inferiorly are the splanchnic nerves and some lymphatic glands. To expose these last, we must remove the pleura, and a layer of dense fascia which lines the chest outside it. DESCENDING We have already traced the arch of the aorta THOEACIC AOKTA. to the body of the fifth dorsal vertebra (p. 177). From this point, the aorta descends on the left side of the spine, gradually approaching towards the middle line. The artery, more- over, following the dorsal spinal curve, is not vertical, but concave forwards. Opposite the last dorsal vertebra it passes between the crura of the diaphragm and enters the abdomen. It is contained in the posterior mediastinum ; on its left side it is covered with pleura enclosing the left lung, and below it has the oesophagus to the left; on its right, run the vena azygos, the oesophagus, and thoracic duct ; in front of it are, the root of the left lung, and the pericardium. Lower down the oesophagus is in front of the artery, and subsequently lies a little to its left side ; behind are the verte- bral column and the vena azygos minor. Its branches will be described presently. VENA AZYGOS This vein commences in the abdomen opposite MAJOR. the first or second lumbar vertebra, by small branches from one of the lumbar veins of the right side, and gene- rally communicates with the renal, or the vena cava itself. This, indeed, is the main point about the origin of the vena azygos, that it communicates directly or indirectly with the vena cava inferior. It enters the chest through the aortic opening of the diaphragm, and ascends on the right side of the aorta through the posterior mediastinum, in front of the bodies of the lower dorsal vertebrae, and over the right intercostal arteries. When the vein reaches the level of the third dorsal vertebra, it arches forwards over the right bronchus, and terminates in the superior vena cava, just before this vessel is covered by pericardium. In its course it VENA AZYGOS MINOK. 183 FIG. 44. receives nine or ten of the lower intercostal veins of the right side, the spinal veins, the posterior mediastinal, the oesophageal and the right bronchial veins. Opposite the sixth or seventh dorsal vertebra it is joined by the left vena azy- gos. It is occasionally connected with the right superior intercostal vein. The left vena azygos, vena azygos minor, runs up the left side of the spine. This vein commences in the abdomen from one of the lumbar veins of the left side, or from the left renal. It then ascends on the left side of the aorta, through the left crus of the diaphragm. On a level with the sixth or seventh dorsal vertebra, it passes beneath the aorta and thoracic duct to join the azygos major. Before passing beneath the aorta it usually communicates with the left superior intercostal vein. It generally receives six or seven of the lower intercostal veins of the left side, the cesophageal and mediastinal veins. These azygos veins are provided with imperfect valves, and are supplemental to the inferior vena cava. The left upper azyyos vein re- ceives the intercostal veins of the left side, usually from the fourth to the sixth ; it communicates above with the left superior intercostal vein, and opens below, either directly into the vena azygos major, or indirectly into it through the vena azygos minor. DIAGRAM TO SHOW THE COURSE OF THE VENA AZYGOS AND THE THORACIC DUCT. 184 THORACIC DUCT. THORACIC DUCT The thoracic duct (fig. 43) is a canal, from AND EECEPTA- fifteen to eighteen inches long, through which the CULUM CHYLI. contents of the lacteal vessels from the intestines and the lymphatics from the lower limbs are conveyed into the blood. These vessels converge to an oval dilatation, termed recep- taculum cliyli (cistern of Pecquet), situated a little to the right side of the front of the body of the second lumbar vertebra, behind the aorta and close to the right crus of the diaphragm. Then, getting to the right side of the aorta, it ascends through the aortic opening of the diaphragm into the chest, and runs up the posterior mediastinum, still along the right side of the aorta, between this vessel and the vena azygos major, and opposite the sixth dorsal vertebra crosses over the vena azygos minor. Near the third dorsal vertebra, it inclines to the left side, and then passes behind the arch of the aorta and the oesophagus, and ascends on the left side of this tube, between it and the left pleura ; subsequently the duct passes up between the oesophagus and the left subclavian artery, as high as the seventh cervical vertebra, resting on the longus colli. It then emerges from beneath the carotid sheath, curves downwards over the subclavian artery, in front of the scalenus anticus, and opens into the back part of the confluence of the left internal jugular and subclavian veins. The orifice of the duct is guarded .by two valves which permit fluid to pass from the duct into the vein, but not vice versa. Valves, disposed like those in the venous system, are placed at short intervals along the duct, more numerous in its upper part, so that its contents can only pass upwards. 1 The diameter of the duct varies in different parts of its course ; at its commencement it is about three lines in diameter, at the sixth dorsal it is about two lines, and it enlarges again towards the termination. It receives the lymphatics from the lower extremities, and from all the abdominal viscera (except the convex surface of the liver and the abdominal walls) ; above 1 The thoracic duct varies in size in different individuals. It may divide in its course into two branches, which subsequently reunite ; instead of one there may be several terminal orifices. Instances have been observed in which the duct has terminated on the right instead of the left side (Fleischmann, Leichenoffnungen, 1815 ; also Morrison, Journal of Anat., vol. vi. p. 427). It has been seen to ter- minate in the vena azygos (Mtiller's Archiv, 1834). (ESOPHAGUS. 185 these it receives the lymphatics from the left side of the thorax, the left lung, the left side of' the heart, the left upper extremity, and the left side of the head and neck. The oesophagus is that part of the alimentary (ESOPHAGUS. * .; t A canal which conveys the food from the pharynx to the stomach. It commences at the lower border of the fifth cervical vertebra, at the back of the cricoid cartilage; runs down in front of the spine, to the right side of the transverse portion of the arch of the aorta, then through the posterior mediastinum in front of the descending aorta, and passes through the oesophageal opening in the diaphragm to end in the stomach, opposite the ninth dorsal vertebra. It is from nine to ten inches long. Its course is not exactly straight, for it describes three curves one an antero- posterior, the other two lateral curves. In the neck at its com- mencement it lies at first in the middle line ; it then gets behind, and a little to the left of the trachea ; in the chest, i.e. about the fourth dorsal vertebra, it inclines towards the right side to make way for the aorta ; but it again inclines to the left before it passes through the diaphragm. Its antero-posterior curve corresponds to the curve of the spinal column. The oesophagus, in the neck, rests behind, upon the front of the spine covered by the longus colli muscle ; in front, it has the trachea ; on each side, it is in relation with the thyroid body, the common carotid (chiefly the left), and inferior thyroid arteries, and the recurrent laryngeal nerves ; to the left of it is the thoracic duct. In the thorax, the oesophagus has, in front, the trachea, the left bronchus, the arch of the aorta, the left carotid and left subclavian arteries ; and, lastly, for about two inches, the posterior surfage of the pericardium (behind the left auricle) : this accounts for the pain which is sometimes experienced, in cases of pericarditis, during the passage of food ; behind, it rests upon the spinal column, the longus colli, the thoracic duct, the third, fourth, and fifth intercostal arteries of the right side ; and, lastly, it lies in front of and slightly to the left side of the aorta ; laterally, the aorta and pleura are to the left, and the vena azygos major to the right of the tube. As it passes down in the interpleural space, it is in connection with both pleurae. The oesophagus is surrounded by a 186 PNEUMOGASTRIC NERVES. plexus of nerves formed by the pneumogastric nerves, the left being in front of, the right behind it. The oesophagus is supplied with blood by the inferior thyroid, the oesophageal branches of the aorta, the coronaria ventriculi, and the left phrenic artery. It is supplied with nerves by the pneumo- gastric and the sympathetic, which ramify between the two mus- cular layers. The oesophagus is composed of three coats, an external or muscular, a middle or areolar, and an internal or mucous. The muscular coat consists of an outer longitudinal, and an inner cir- cular layer of fibres. The longitudinal layer is particularly strong, and arranged in the upper part mainly in three fasciculi, an ante- rior attached to the vertical ridge on the cricoid cartilage, and two lateral, which are continuous with the inferior constrictor ; these, lower down, spread out and form a continuous layer round the oesophagus and support the circular fibres. Under the microscope the muscular fibres composing the upper part are seen to consist entirely of the striped variety ; at the lower part, almost exclu- sively of the non-striped variety. The middle coat is composed of areolar tissue, and connects very loosely the muscular and mucous coats. The mucous membrane is of a pale colour and considerable thickness, and in the contracted state of the oesophagus is arranged in longitudinal folds within the tube which lies flattened in front of the spine. On the surface of the mucous membrane there are numerous minute papillae placed obliquely. It is lined by a very thick layer of scaly epithelium. In the submucous tissue are many small compound racemose glands oesophageal glands especially towards the lower end of the oesophagus. COURSE AND The course of the pneumogastric nerves in BKANCHES OF THE the chest is not the same on both sides. The PNEUMOGASTRIC right pneumogastric nerve enters the chest between the subclavian artery and vein, descends behind the right innominate vein by the side of the trachea to the back of the root of the lung, where it breaks up into a plexus forming the posterior pulmonary plexus. From this plexus two cords descend to the posterior surface of the oesophagus, upon which they divide into numerous branches : forming, with corresponding branches of the left pneumogastric nerve, the oesophageal plexus (plexus guise). BRANCHES OF THE PNETJMOGASTRIC IN THE CHEST. 187 The plexus then reunites into a single trunk, consisting also of some fibres from the left pneumogastric, and passes into the abdo- men through the cesophageal opening in the diaphragm. The left pneumogastric descends into the chest between the left subclavian and carotid arteries, and behind the left brachio-cephalic vein. It then crosses in front of the arch of the aorta, and passes behind the root of the left lung to the anterior surface of the ossophagus, upon which it also assists to form a plexus with the nerve of the right side. The branches of the pneumogastric nerve in the chest are as follow : a. The inferior laryngeal or recurrent. This nerve on the right side turns under the subclavian and the common carotid arteries (p. 114); on the left, under the arch of the aorta, below the ductus arteriosus, and ascends to the larynx. It passes beneath the inferior thyroid artery, and lying in the groove between the trachea and oesophagus, it enters the larynx beneath the lower border of the inferior constrictor of the pharynx. It supplies with motor nerves all the muscles which act upon the rima glottidis, except the crico-thyroid (supplied by the external laryngeal nerve). As they turn beneath their respective arteries, they give off branches to the deep cardiac plexus ; also some small filaments to the inferior cervical ganglion of the sympathetic. In the neck it distributes small branches to the trachea, oesophagus, and inferior constrictor muscle. b. Cardiac branches. These are very small, and join the cardiac plexuses ; the right arise from the right pneumogastric, and the right recurrent laryngeal, close to the trachea ; the left come from the left recurrent laryngeal nerve. On both sides these branches pass to the deep cardiac plexus. c. Pulmonary branches. These accompany the bronchial tubes. The greater number run behind the root of the lung, and constitute the posterior pulmonary plexus. A few, forming the anterior pul- monary plexus, supply the front part of the root of the lung. Both these plexuses are joined by filaments from the second, third, and fourth thoracic ganglia of the sympathetic. The nerves of the lungs are, however, very small, and cannot be traced far in to their substance. 1 d. (Eso])hageal plexus. Below the root of the lung each pneumo- gastric nerve is subdivided so as to form an interlacement of nerves round the oesophagus (plexus guise). From this plexus numerous 1 Upon this subject, see the beautiful plates of Scarpa. 188 SYMPATHETIC IN THE CHEST. filaments supply the coats of the tube ; but the majority of them are collected into two nerves the one, chiefly the continuation of the left pneumogastric nerve; lying in front of the oesophagus ; the other, chiefly that of the right, lying behind it. Both nerves pass through the oasophageal opening in the diaphragm for the supply of the stomach : the left also sending filaments to join the hepatic plexus ; the right sending branches to the coeliac, splenic and left renal plexuses. Having examined the contents of the posterior mediastinum from the right side, now do so from the left. The left lung should be turned out of its cavity and fastened by hooks towards the right side. After removing the pleura, we see the descending thoracic aorta, the pneumogastric nerve crossing the arch and sending the recurrent branch under it; also the first part of the left subclavian, covered externally by the pleura. The pneumogastric nerve must be traced behind the root of the left lung to the O3SO- phagus, and the cesophageal plexus of this side dissected. Lastly, notice the lesser vena azygos which crosses under the aorta about the sixth or seventh dorsal vertebra to join the vena azygos major. THORACIC FOR- This portion of the sympathetic system is gene- TION OF THE rally composed of twelve ganglia covered by the SYMPATHETIC. pleura ; one ganglion being found over the head of each rib, except the last two, which lie on the side of the bodies of the vertebrae. Often there are only ten ganglia, in consequence of two of them being fused here and there. The first thoracic ganglion is the largest. The ganglia are connected together by thick branches, and each ganglion is connected externally by two branches with the corresponding intercostal nerve. The nerves proceeding from the ganglia pass inwards to supply the thoracic and part of the abdo- minal viscera. The internal branches which proceed from the six upper ganglia are small, and are distributed as follows (see the diagram) : a. Minute nerves from the first and second ganglia to the deep cardiac plexus. b. Minute nerves from the third and fourth ganglia to the pos- terior pulmonary plexus. The branches arising from the six lower ganglia unite to form SPLANCHNIC NERVES. 189 Fro. 45. three nerves the great splanchnic, the lesser, and the smallest splanchnic nerves. a. The great splanchnic nerve is generally formed by branches from the fifth or sixth to the tenth ganglion, and also receiving filaments, according to Beck, from all the thoracic ganglia above the sixth. They descend obliquely by the sides of the bodies of the dorsal ver- tebree, along the posterior mediasti- num, and unite into a single nerve, which passes through the correspond- ing cms of the diaphragm, and joins the semilunar ganglion of the abdo- men, sending also branches to the renal and supra-renal plexuses. b. The lesser splanchnic nerve is commonly formed by branches from the tenth and eleventh ganglia. It passes through the crus of the dia- phragm to the coeliac plexus, and occasionally to the renal plexus. 1 c. The smallest splanchnic nerve comes from the twelfth ganglion, passes through the crus of the dia- phragm, and terminates in the lower part of the coeliac and renal plexuses. (This is not represented in the dia- gram.) INTERCOSTAL The intercostal MUSCLES. muscles fill in the intervals between the ribs and are ar- ranged in each interval in two layers, an external and an internal, which cross each other like the letter X. The external intercostals, eleven on each side, run obliquely from behind forwards, like the external oblique muscle of the 1 In a few instances we have traced a minute filament from one of the ganglia into the body of a vertebra. According to Cruveilhier each vertebra receives one. DIAGRAM OF THE THORACIC PORTION OF THE SYMPATHETIC. 190 INTERCOSTAL MUSCLES. abdomen. They connect the contiguous borders of the ribs, passing from the outer lip of the rib above to the upper border of the rib below : they extend from the tubercles of the ribs behind to the costal cartilages in front, and are continued for- wards to the sternum as a thin membrane. The internal run from before backwards like the internal oblique, and pass from the inner lip of the groove in the rib above and from the costal cartilage, and are inserted into the upper border of the rib below. Observe that a few fibres of the inner layer pass over one or even two ribs, chiefly near the angles (especially of the lower ribs), and terminate upon a rib lower down. 1 Neither of these layers of intercostal muscles extends all the way between the sternum and the spine : the outer layer, begin- ning at the spine, ceases at the cartilages of the ribs ; the inner, commencing at the sternum, ceases at the angles of the ribs. The intercostal muscles present an intermixture of tendinous and fleshy fibres ; and they are covered inside and outside the chest by a glistening fascia, to give greater protection to the intercostal spaces. The external intercostal muscles elevate the ribs, and are therefore muscles of inspiration. The internal intercostal muscles depress the ribs, and are therefore muscles of expiration. INTERCOSTAL There are eleven intercostal arteries on each ARTERIES. side which lie between the internal and external intercostal muscles. The two upper arteries are derived from the superior intercostal branch of the subclavian ; the remaining nine are furnished by the thoracic aorta : and since this vessel lies rather on the left side of the spine, the right intercostal arteries are longer than the left. The upper intercostal arteries from the aorta ascend obliquely to reach their intercostal spaces ; the lower run more transversely. They are given off from the back of the descending aorta, and as they pass outwards across the bodies of the vertebras they are covered by the pleura, and the sympathetic nerves ; the right, in addition, pass behind the ossophagus, thoracic duct, and the vena azygos major ; the left behind the left superior intercostal vein and the vena azygos minor. Having 1 These irregular muscular bundles are called the subcostal muscles. INTERCOSTAL ARTERIES. 191 reached the intercostal space, each artery divides into an anterior and a posterior branch. The anterior branch in direction and size appears to be the continuation of the common trunk. At first it runs along the middle of the intercostal space, lying upon the external intercostal muscle, and separated from the cavity of the chest by the pleura and intercostal fascia. Here, therefore, it is liable to be injured by a wound in the back. But near the angle of the rib it passes between the intercostal muscles, and occupies the groove in the lower border of the rib above. Here it gives off a small branch, the collateral intercostal, which runs for some distance along the upper border of the rib below. After supplying the muscles, the main trunk anastomoses with the anterior inter- costal branch of the internal mammary artery. In some cases this branch is as large as the intercostal itself, and situated so as to be directly exposed to injury in the operation of tapping the chest. In its course along the intercostal space, each artery sends branches to the intercostal muscles and the ribs. About midway between the sternum and the spine, each gives off a small branch, which accompanies the lateral cutaneous branch of the intercostal nerve. The continued trunk, gradually decreasing in size, becomes very small towards the anterior part of the space, and is placed more in the middle of it. Those of the true intercostal spaces inosculate with branches of the internal mammary, and thoracic branches of the axillary ; those of the false run between the layers of the abdominal muscles, and anastomose with the epigastric and lumbar arteries. The posterior or dorsal branch passes backwards between the transverse processes of the vertebrae, on the inner side of the anterior costo-transverse ligament, and is distributed to the muscles and skin of the back. Each sends an artery through the inter vertebral foramen to the spinal cord and its membranes. On the right side the intercostal veins terminate in the vena azygos major ; on the left, the seven or eight lower terminate in the vena azygos minor, the remainder in the left superior inter- costal vein. The usual relation which the intercostal vessels and nerve bear 192 INTERCOSTAL NERVES. DOKSAL NERVES. PIG. 46. to each other in the intercostal space, is, that the vein lies upper- most, the nerve lowest, and the artery between them. The dorsal nerves are twelve in number, the first emerging between the first and second dorsal vertebras, and do not form a plexus as in the cervical, lumbar and sacral regions. Each dorsal nerve (like all the spinal nerves) arises from the spinal cord by two roots, an anterior or motor, and a posterior or sensory. The sensory root has a ganglion upon it. The two roots unite in the intervertebral foramen and form a compoimd nerve. After passing through the foramen, it is con- nected by two filaments with the sympathetic nerve, and then divides into an anterior and a posterior branch. The posterior or dorsal branches pass back- wards between the transverse processes of the dorsal vertebras and divide into internal and external branches : the internal branches pass between the multi- fidus spinae and semispinalis dorsi, pierce the rhomboidei and tra- pezius muscles ; the six upper branches become cutaneous at the spinous processes of the ver- tebrae ; the six lower supply only the multifidus spinae, not giving off any cutaneous filaments ; the external branches pass through the longissimus dorsi and supply this muscle, the ilio-costalis and their continuations and the levatores costarum ; the six lower branches, in addition, distribute cutaneous filaments to the skin. These branches will be described more fully later on in the dissection of the back. INTERCOSTAL The intercostal nerves are the anterior divisions NERVES. of the dorsal nerves, and are twelve in number. Each nerve receives a filament from the sympathetic, and then proceeds between the intercostal muscles in company with, and immediately below, the corresponding artery. Midway between DIAGRAM OF A SPINAL NERVE. INTERCOSTAL NERVES. 193 the spine and the sternum, they give off lateral cutaneous branches, which supply the skin over the scapula and the thorax. The intercostal nerves terminate in front in the anterior cutaneous nerves. In the anterior part of the intercostal space the nerves lie in the substance of the internal intercostal muscles, and at the costal cartilages get to the inner side of the muscles, passing between them and the pleura. The intercostal nerves are divided into two sets : the six upper are called the pectoral intercostals, because they supply the struc- tures of the pectoral region ; the six lower, the abdominal inter- costals, because they supply the chest and abdominal walls. The upper or pectoral intercostal nerves pass between the external and internal intercostal muscl.es, run forwards in the substance of the latter muscle, and at the sternal end of the in- tercostal spaces pierce the internal intercostal muscles and the pectoralis major, to be ultimately distributed to the skin of the chest. The upper intercostal nerves supply the levatores costarum, serratus posticus superior, the intercostals, and the triangularis sterni. The lower or abdominal intercostal nerves pass like the upper nerves between the intercostal muscles as far forwards as the costal cartilages. They pass behind these, and then run between the transversalis and internal oblique, as far as the outer border of the rectus. Piercing the , sheath of the muscle, they supply it, and subsequently end as the anterior cutaneous nerves of the abdomen. They supply the intercostal muscles, the serratus posticus inferior, and the abdominal parietal muscles. Notice that the first dorsal nerve ascends nearly perpendicu- larly over the neck of the first rib to form part of the brachial plexus. This nerve, however, gives off a small branch, the first intercostal nerve, to supply the first intercostal space. This, as a rule, has no lateral cutaneous branch. Intercostal lymphatic glands These are situated near the heads of the ribs ; there are some between the layers of the intercostal muscles. They are of small size, and their efferent vessels go into the thoracic duct. Some of the upper ones on the right side pass into the right lymphatic duct. We have seen these intercostal glands enlarged and diseased in phthisis. O 194 PULMONARY ARTERY. BRONCHIAL AND Small bronchial arteries, arising on the right (EsopHAGEAL side most frequently from the first aortic inter- AKTEEIES. costal (third intercostal) artery, and on the left from the thoracic aorta, accompany the bronchial tube on its posterior aspect into the substance of the lung. 1 Their distribu- tion and office will be considered with the anatomy of the lung. CEsopliacjeal arteries, four or five in number, proceed from the front of the thoracic aorta to ramify on the oesophagus, where they inosculate above with the cesophageal branches of the inferior thyroid, and below with the cesophageal branches of the coron- aria ventriculi and phrenic arteries. Small posterior mediastinal arteries are given off from the posterior part of the aorta, and supply the lymphatic glands and tissues of the posterior media- stinum. Having finished the posterior mediastinum, replace the lung, and turn your attention once more to the great vessels at the root of the heart. PULMONARY This vessel is about two inches in length, and ARTERY. conveys the venous blood from the heart to the lungs. It proceeds from the upper part of the base of the right ventricle, and passes upwards and backwards along the left side of the aorta to the concavity of the arch of the aorta, where it divides into two branches, a right and a left, one for each lung. At its origin it has on each side an auricular appendix and a coronary artery, and lies in front of the root of the aorta. The pulmonary artery and the aorta are surrounded for two inches by a common sheath of pericardium. The right branch, the larger and longer, passes horizontally below the arch of the aorta, behind the ascending aorta and the superior vena cava, to the root of its lung ; the left is easily followed to its lung by removing the layer of pericardium investing it, when it will be found to pass hori- zontally in front of the descending aorta and the left bronchus to the root of the left lung. Search should be made for a short fibrous cord which connects 1 On the left side there are usually two bronchial arteries a superior, arising from the highest part of the thoracic aorta, and an inferior, arising about an inch lower down. CARDIAC NERVES. 195 the commencement of the left pulmonary artery with the concavity of the arch of the aorta. This cord is the remains of the duct its arteriosus, a canal which in foetal life conveyed blood from the pulmonary artery to the aorta. Draw towards the left side the first part of the arch of the aorta, and dissect the pericardium from the great vessels at the base of the heart. Thus a good view will be obtained of the trachea and its bifurcation into the two bronchi. Below the division of the trachea the right pulmonary artery is seen passing in front of the right bronchus. The superior vena cava and aorta are seen in front of, and nearly at right angles to, the right pul- monary artery. The vena azygos major is seen arching over the right bronchus and terminating in the vena cava superior, just before this vein pierces the pericardium. Notice, especially, a number of lymphatic glands called bronchial, at the angle of bifurcation of the trachea. The situation of these glands in the midst of so many tubes explains the variety of symptoms which may be produced by their enlargement. NERVES OF THE The nerves of the heart come from the pneumo- HEAKT AND CAB- gastric and its recurrent branch, and the three DIAC PLEXUSES. cervical ganglia of the sympathetic. The pneumo- gastric gives off (generally) two or more filaments (cardiac) which proceed from the main trunk in the neck, or from its recurrent branch. The sympathetic sends three (cardiac) filaments : one from the upper cervical ganglion, a second from the middle, and a third from the lower; and they are called, respectively, the upper, middle, and lower cardiac nerves of the sympathetic. The minute and delicate nerves from these several sources on each side, pass downwards to the base of the heart. They vary very much in their precise relations to the great vessels upon which they run ; but speaking generally, it may be said that the nerves on the right side run chiefly behind the arch of the aorta ; those on the left, in front of it. Eventually they form, by their mutual subdivisions and interlacement, an intricate network of nerves, termed, according to their position, the superficial and the deep cardiac plexus. The superficial and smaller cardiac plexus lies in the concavity o 2 196 CARDIAC PLEXUS. of the arcli of the aorta in front of the right pulmonary artery. It is closely connected with the deep plexus. It receives the upper cardiac branch of the left sympathetic, the lower cervical cardiac branch from the left pneumogastric, and filaments from the deep plexus. In it is usually found a small ganglion, ganglion of Wrisberg, placed beneath the arch of the aorta on the right side of the ductus arteriosus. This plexus distributes branches to the anterior coronary and the anterior pulmonary plexuses. The deeper and larger cardiac plexus is situated behind the arch of the aorta in front of the bifurcation of the trachea and imme- diately above the right pulmonary artery. To see it the peri- cardial covering of the aorta must be carefully removed and the vessel hooked forwards and to the left. This plexus is formed by all the cardiac branches of the right and left sympathetic ganglia, and by the cardiac branches of the pneumogastric and recurrent laryngeal nerves, except the left superior cardiac branch of the sympathetic and the left cervical cardiac branch of the pneumo- gastric, both of which pass to the superficial cardiac plexus. The branches from the right side of this plexus descend chiefly in front of the pulmonary artery and pass to the anterior pulmonary plexus, and to the anterior coronary plexus ; a few branches which pass behind the pulmonary artery are distributed to the right auricle and to the posterior coronary plexus. The branches from the left side of the plexus go to the left auricle, the anterior pulmonary plexus, but chiefly to the posterior coronary plexus. From the cardiac plexuses, as a common centre, the nerves pass off to the heart, forming plexuses around the coronary arteries. Thus, the anterior coronary plexus (derived chiefly from the super- ficial cardiac) accompanies the anterior coronary artery. The posterior coronary plexus (derived chiefly from the left side of the deep cardiac) runs with the posterior coronary artery. The two plexuses communicate at the apex of the heart, and in the ventri- cular septum. It is not an easy matter to trace the nerves into the substance of the heart. For this purpose a horse's heart is the best, and previous maceration in water is desirable. The nerves in the substance of the heart are peculiar in this respect ; that they CONSTITUENTS OF THE ROOTS OF THE LUNGS. 197 present minute ganglia in their course, which are presumed to preside over the rhythmical contractions of the heart. Draw aside the margin of the right lung ; divide the superior vena cava above the vena azygos, and turn down the lower part. Remove FIG. 47. CONSTITUENTS OF THE BOOT OF EACH LUNG. DIAGRAM SHOWING THE CONSTITUENTS OF THE ROOT OF EACH LUNG, AND THEIR RELATIVE POSITION : ALSO THE POSITION OF THE VALVES OF THE HEART. THE ARROWS INDICATE THE DIRECTIONS IN WHICH AORTIC AND MITRAL MURMURS ARE PROPAGATED. the layer of pericardium which covers the pulmonary veins, and the constituent parts of the root of the right lung will be exposed. It is composed of the pulmonary artery, the pulmonary veins, bronchus, bronchial vessels, anterior and posterior pulmonary 198 DISSECTION OF THE HEAET. plexuses, and some lymphatics. The following is the disposition of the large vessels forming the root of the lung. In front are the two pulmonary veins : behind the veins are the subdivisions of the pulmonary artery ; behind the artery are the divisions of the bronchus. From above downwards they are disposed thus : On the right side we find 1st, the bronchus ; 2nd, the artery ; 3rd, the veins. On the left, we find : 1st, the artery ; 2nd, the bronchus ; 3rd, the veins as shown in fig. 47. DISSECTION OF THE HEAET. The heart is conical in form, and more or less convex on its external aspect, with the exception of that portion lying on the tendinous centre of the diaphragm, which is flattened. It is situated obliquely in the thorax between the two lungs, and is completely surrounded by the pericardium. It extends from the fifth to the eighth dorsal vertebra, with its base directed upwards and to the right, its apex downwards and to the left, where during life it beats in the fifth intercostal space, two inches below the nipple and an inch to its sternal side. The position which the heart bears to the thoracic walls has been already described (p. 167) ; it varies, however, in different sub- jects, and as a rule is higher in the dead body than in the living, owing to the shrinking of the lungs. The anterior surface of the heart is convex and looks upwards, and forwards ; the posterior surface is flattened and rests upon the diaphragm : the former is chiefly formed by the right ventricle, the latter by the left ventricle. The right border is sharp (ratmyo acutiis), while the left border is thick and rounded (margo obtusus). SIZE AND The size of the heart is dependent upon so WEIGHT. many conditions, that the following measurements must be received with more or less limitation. An average heart will measure, in its transverse direction at the base, three and a half inches ; in its length, about five inches ; in its thickness, two and a half inches. The weight is from ten to twelve ounces in the male, and from eight to ten in the female ; but much depends upon the THE HEART. 199 size and condition of the body generally. As a rule, the heart gradually increases in length, breadth, and thickness from child- hood to old age. 1 Notice two longitudinal grooves (sulci) on the front and back surfaces of the heart, which extend from the base of the ventricles to the apex, and which indicate the septum between the two ven- tricles ; the anterior groove lies nearer to the left side, the posterior to the right side of the heart. A circular groove, nearer the base, marks the separation be- tween the auricles and ventricles. In the circular and longitu- dinal furrows, surrounded by more or less fat, run the coronary vessels, the nerves, and the lymphatics. The heart is a double hollow muscular organ; that is, it is composed of two hearts, a right and a left, separated by a septum, and not communicating with each other except during uterine, and rarely in adult, life. Each half consists of two cavities, an auricle and a ventricle, which communicate by a wide orifice, the auriculo-ventricular opening. The right half of the heart propels venous blood to the lungs, and is called the pulmonary ; the left propels arterial blood from the lungs throughout the body, and is called the systemic. These two hearts are not placed apart, be- cause important advantages result from their union. By being enclosed in a single bag they occupy less room in the chest ; and the action of their corresponding cavities being precisely synchro- nous, their fibres, mutually intermixing, contribute to their mutual support. The cavities of the heart should now be examined in the order in which the blood circulates through them. This is situated at the right side of the base of the heart, and forms a quadrangular cavity, the atrium or sinus venosus, between the two venae cavae, from which it receives the blood. From its front, a small pouch projects towards the left, and overlaps the root of the aorta ; this part is termed the appendix auriculce, and resembles a dog's ear in shape. 1 T. B. Peacock, London and Edinb. Monthly Journal of Medical Science, 1846 and 1854 ; Clendinning, Med. Chir. Trans., 1838 ; Beneke, Marburger Schriften, xi., 1879. 200 THE RIGHT AURICLE. To see the interior, make a horizontal incision through the anterior wall from the apex of the appendix transversely across the cavity : from this make another upwards at right angles into the superior vena cava. The interior is lined by a polished mem- brane called the endocardium, and is everywhere smooth except in the appendix, where the muscular fibres are collected into bun- dles, called, from their resemblance to the teeth of a comb, mmcnli pectinati. They radiate from the auricle to the edge of the auriculo- ventricular opening. The following objects are seen on opening the auricle : Superior vena cava. Eustachian valve. Inferior vena cava. Coronary valve. Coronary sinus. Annulus ovalis. Auriculo-ventricular opening. Fossa ovalis. Foramina Thebesii. Tubercle of Lower. Musculi pectinati. Examine carefully the openings of the two vence cavce : they are not directly opposite to each other ; the superior cava opens into the auricle on a plane rather in front, and a little to the left, of the inferior, so that its orifice is opposite to the auriculo-ventri- cular opening. The inferior cava, after passing through the ten- dinous centre of the diaphragm, makes a slight curve to the left before it opens into the lowest part of the auricle ; its direction is upwards and inwards, so that the stream of blood is directed towards the auricular septum. The orifice of each vena cava is nearly circular, and surrounded by circular muscular fibres continuous with those of the auricle. The posterior wall of the auricle is formed by the partition between the auricles, the septum auricidarum. Upon this septum, above, and to the left of the orifice of the vena cava inferior, is an oval depression (fossa ovalis), bounded by a prominent border (annidus ovalis). This depression indicates the remains of the opening (foramen ovale) through which the blood in foetal life passed from the right into the left auricle. After birth this open- ing closes ; but if the closure is imperfect, the stream of dark blood in the right auricle mixes with the florid blood in the left, and occasions what is called cyanosis. A valvular communication, INTERIOR OF THE RIGHT AURICLE. 201 however, not infrequently exists between the auricles in this situa- tion which is not attended with indications of this disease. A more or less noticeable fold of the lining membrane, the Stulafhian valcej- may be seen projecting from the front margin of the v. c. inferior to the front border of the fossa ovalis. It is placed between the inferior vena cava and the lower margin of the annulus ovalis. Curved in shape, it passes forwards and ends in two cornua ; of which, one is attached to the annulus ovalis, the other is lost on the wall of the auricle. It consists of a reduplica- tion of the endocardium and contains some muscular tissue. It is FIG. 48. Anricnlo-Yentriciilar orifice. F066*0TliS Opening of the coronary rein Line of Enstacliian nlre DIAGBAH OF THE IXTEKIOH OF THE BIGHT AURICLE. the remnant of a valve, which was of considerable size in foetal life, and served to direct the current of blood from the v. c. inferior, through the foramen ovale, into the left auricle. To the left of the Eustachian valve, that is, between its remains and the auriculo- ventricular opening, is the orifice of the cwoni-ij sinus. The sinus is about an inch in length and receives the great cardiac vein, the posterior cardiac vein, and the oblique vein (of Marshall), and will nearly admit the end of the little finger. It is surrounded by muscular fibres, and is guarded by a semi- circular fold of the endocardium, called the voice of Thebesim* 1 Eustachius, Libell. de Vena sine Part. * This valve is occasionally doable. 202 THE EIGHT VENTRICLE. to prevent regurgitation of the blood during the auricular con- traction. Here and there upon the posterior wall of the auricle may be observed minute openings, called foramina Thebesii : some being the orifices of small veins returning blood from the substance of the heart ; others being simple depressions in the muscular tissue. To the left, and rather in front of the orifice of the vena cava in- ferior, is the auricitlo-ventricular opening, guarded by the tricuspid valve. It is oval in form, and will admit the passage of three fingers. Lastly, between the orifices of the superior and inferior venas cavae is a rounded elevation, the tubercle of Lower * (not seen in the diagram), which is supposed to direct the current of blood, in foetal life, from the superior cava to the auriculo-ventricular opening. The musculi pectinati are parallel muscular elevations running across the inner surface of the auricular appendix, and to a slight extent also of the sinus venosus. EIGHT VEN- This forms the right border and about two- TBICLE. thirds of the front surface of the heart. To examine its interior, a triangular flap should be raised from its anterior wall. The apex of this flap should' be below: one cut along the right edge of the ventricle, the other along the line of the ventricular septum. Observe that the wall of the ventricle is much thicker than that of the auricle. The cavity of the ventricle is conical, with base upwards and to the right. Its inner wall is convex, and is formed by the septum ventriculorum. The upper and front part presents a smooth passage, the infundibulum or conns arteriosus, which leads to the opening of the pulmonary artery. It is situated to the left and in front of the auriculo- ventricular opening, and about three-fourths of an inch higher. The following objects are seen in the right ventricle : Columnae earner. Auriculo-ventricular opening. Chordae tendineffi. Pulmonary opening guarded by the tricuspid and semilunar valves. From its walls project bands of muscular fibres, columnar carnece, 1 Most distinct in quadrupeds. . TRICUSPID VALVE. 203 of various length and thickness, which cross each other in every direction ; this muscular network is generally filled with coagulated blood. Of these columnse carneae there are three kinds : one stands out in relief from the ventricle ; another is attached to the ventricle by its extremities only, the intermediate portion being free ; a third, and by far the most important set, called musculi papillares, is fixed by one extremity to the wall of the ventricle, while the other extremity gives attachment to the fine tendinous cords, chorda} tendinece, which regulate the action of the tricuspid valve. The number of these musculi papillares is equal to the number of the chief segments of the valve ; hence there are three in the right, and two in the left ventricle. Of those in the right ventricle, one is attached to the septum. There are two openings in the right ventricle. One, the auricula-ventricular, through which the blood passes from the aur- icle, is oval in form and placed at the base of the ventricle. It is surrounded by a ring of fibrous tissue, to which is attached the tricuspid valve. TRICUSPID This is situated at the right auriculo- ventricular VALVE. opening, and consists of three triangular flaps. Like all the valves of the heart, it is formed by a fold of the lining membrane (endocardium) of the heart, strengthened by fibrous tissue, in which a few muscular fibres may be demonstrated. The bases of the valves are continuous with one another, so that they form a membranous ring between the auricle and ventricle, while the segments project into the cavity of the right ventricle. Of its three flaps, the largest or anterior is so placed, that, when not in action, it partially covers the orifice of the pulmonary artery; another, the internal, corresponds with the inferior wall of the ventricle ; the third, or posterior, rests upon the septum ventriculorum. Observe the arrangement of the tendinous cords which regulate the action of the valve. First, they are all attached to the ven- tricular surface of the valve. Secondly, the tendinous cords pro- ceeding from a given papillary muscle are attached to the ad- jacent halves of two of the flaps ; consequently, when the ventricle contracts, and the papillary muscle also, the adjacent borders of 204 PULMONARY VALVES. the flaps will be approximated. Thirdly, to insure the strength of every part of the valve, the tendinous cords are inserted at three different points of it in straight lines ; accordingly, they are divi- sible into three sets. Those of the first, which are three or four in number, are attached to the base of the valve ; those of the second, from four to six, proceed to the middle of its ventricular surface ; those of the third, which are the smallest and most numerous, are attached to its free margin. 1 PDLMOXAKY OR These are three semicircular membranous folds, SEMILUNAB like watch-pockets, situated at the orifice of the VALVES. pulmonary artery. They, are attached by. their convex borders to the root of the artery; their free edges look upwards, and present a festooned border, in the centre of which is a small cartilaginous body called the nodulus or corpus Araintii? The use of these bodies is plain. Since the valves are semilunar, when they fall together they would not exactly close the artery ; there would be a space of a triangular form left between them in the centre, just as there is when we put the thumb, fore, and middle fingers together. This space is filled up by these nodules, so that the closure becomes complete. The valves, two anterior and one posterior, are composed of folds of the endocardium, or lining membrane of the heart. Between the folds is a thin layer of fibrous tissue, which is prolonged from the fibrous ring at the orifice of the artery. This layer of fibrous tissue, however, reaches the free edge of the valve at three points 1 The best mode of showing the action of the valve is to introduce a glass tube into the pulmonary artery, and then to pour water through it into the ventricle until the cavity is quite distended. By gently squeezing the ventricle in the hand, so as artificially to imitate its natural contraction, the tricuspid valve will flap back like a flood-gate, and close the auriculo-ventricular opening. In this way one can understand how, when the ventricle contracts, the blood catches the margin of the valve, and by its pressure gives it the proper distension and figure requisite to block up the aperture into the auricle. It is obvious that the tendinous cords Will prevent the valve from flapping back into the auricle ; and this purpose is assisted by the papillary muscles, which nicely adjust the degree of tension of the cords at a time when they would otherwise be too much slackened by the contraction of the ventricle. z So called after Arantius, an Italian anatomist, who lived towards the close of the sixteenth century. LEFT AURICLE. 205 only : namely, at the centre, or corpus Arantii, and at each ex- tremity. Between these points it stops short, and leaves a crescent- shaped portion of the valve, which is thinner than the rest, and consists of the endocardial membrane. This crescent-shaped por- tion, called the lunula, is not wholly without fibrous tissue ; a thin tendinous cord runs along its free edge, to give it additional strength to resist the pressure of the blood. Behind each of the valves the artery bulges and forms three slight dilatations called the sinuses of Valsalva. 1 These, we shall presently see, are more marked at the orifice of the aorta. The action of these. valves is evident. During the contraction of the ventricle the valves lie against the side of the artery, and offer no impediment to the current of blood ; during its dilatation, the elasticity of the distended artery would force back the column of blood, but that the valves, being caught by the refluent blood, bag, and fall together so as to close the tube. The greater the pressure, the more complete is the closure. The coats of the artery are very elastic and yielding, while the valve, like the circumference to which it is attached, is quite unyielding ; consequently, when the artery is distended by the impulse of the blood, its wall is removed from the contact of the free margin of the valves, and these are the more readily caught by the regurgitating motion of the blood. The force of the reflux is sustained by the tendinous part of the valves, and by the muscular wall of the ventricle (pro- bably in a state of contraction). The valves are capable of sustain- ing a weight of sixty-three pounds before they give way. 2 The thinner portions (lunulce) become placed so as to lie side by side, each one with that of the adjacent valve. This may be demonstrated by filling the artery with water. This is situated at the left side and posterior part of the base of the heart., and is somewhat smaller than the right auricle. It consists, like the right auricle, of a cavity the sinus venosus and the auricular appendix. It is quadrilateral, and receives the four pulmonary veins, two on either side, which return the oxygenated blood from the lungs. From 1 An Italian anatomist, b. 1666, d. 1723. - Haller. 206 LEFT VENTRICLE. its upper and left side, the auricular appendix projects towards the right, curling over the root of the pulmonary artery. The auricle should be opened by a horizontal incision along the ventricular border of the auricle, and another should be made upwards from the centre of the first incision. The interior of the atrium is smooth and flat, but in the appendix there are numerous raised muscular bands, the musculi pectinati. The interior presents the following objects for exam- ination : The orifices of the four pulmonary veins. The auriculo-ventricular opening. The musculi pectinati. The openings of the pulmonary veins are seen in the posterior wall, two on the right side (sometimes three), and two on the left side. They are not guarded by valves. Upon the septum between the auricles is a semilunar depression, indicating the remains of the foramen ovale. The auriculo-ventricular opening, situated at the lower and front part of the auricle, is smaller than that of the right side, and somewhat oval. Its long axis is nearly transverse, and, in the adult, will admit the passage of two fingers. The 'musculi pectinati are also smaller and fewer than in the right auricle. LEFT YEN- This occupies the left border, and forms the TEICLE. apex of the heart. One-third of it only is seen on the anterior surface, the rest being on the posterior. To examine the interior, raise a triangular flap, with the apex below, from its front wall. Observe that its wall is about three times as thick as that of the right ventricle, and that this thickness gradually diminishes towards the apex. The interior of the left ventricle presents the following objects for examination : Auriculo-ventricular opening. Auriculo-ventricular or mitral valves. Aortic opening. Semilunar valves. Columnae carneffi. These parts so closely resemble that of the right that there is no necessity to describe them in detail. The auriculo-ventricular valve consists of two flaps : hence its name mitral or bicuspid. The larger of these flaps is placed between the aortic and auriculo- CORONARY ARTERIES. 207 ventricular orifices. 'There are only two muscnli papillares: one attached to the anterior, the other to the posterior wall of the ventricle. They are thicker, and their chordce tendinece stronger, than those of the right ventricle, but their arrangement is precisely similar. From the upper and back part of the ventricle, a smooth passage leads to the orifice of the aorta. This orifice is placed in the groove between the two auricles, and somewhat in front and to the right side of the left auriculo-ventricular opening. The two orifices are close together, and only separated by the larger flap of the mitral valve. The aortic orifice is guarded by three semilunar valves, of which the arrangement, structure, and mode of action are similar to those of the pulmonary artery. Their framework is proportionately stronger, consistently with the greater strength of the left ventricle, and the greater impulse of the blood. In the sinuses of Valsalva are observed the orifices of the two coronary arteries ; the left arising from the sinus behind the left posterior segment ; the right from behind the anterior segment. SIZE OF THE ^e circumferences of the four orifices are as AUKICULO-VENTBI- follows : that of the tricuspid orifice, 4- 74 inches; CULAR AND ARTE- that of the mitral, 4 inches ; that of the pulmonary, BIAL OPENINGS. 3.55 inches . and that of ^ ^^ 3.^ inches i CORONARY The heart is supplied with blood by the two ARTERIES. coronary arteries, a right or posterior, and a left or anterior. They are about the size of a crow's quill. Both arise from the aorta just above the free margins of the two semilunar valves, and thus always allow the passage of blood ; both run in the furrows on the surface of the heart ; both are accompanied by the cardiac nerves and by lymphatics. The anterior or left coronary artery, the smaller of the two, arises from behind the left posterior valve of the aortic orifice. It appears between the pulmonary artery and the appendix of the left auricle, and then divides into two branches : one which seems the continuation of the main trunk and runs down the inter- ventricular furrow on the anterior surface of the heart to the apex ; the other passes transversely to the left, in the left auriculo- ventricular groove to the back of the heart. 1 Dr. Peacock, Croonian Lectures, 18G5. 208 COKONAKY VEINS AND SINUS. The posterior or right coronary artery arises from behind the anterior cusp of the aortic opening, and descends obliquely between the pulmonary artery and the appendix of the right auricle. It then turns to the right in the groove between the right ventricle and auricle to the back of the heart, where it divides into two branches ; one of which descends in the posterior inter-ventricular furrow towards the apex of the heart ; the other, which appears to be the continuation of the main trunk, runs in the left auriculo- ventricular groove. Besides these branches, the right coronary gives off a large branch which runs along the free border of the right ventricle. Thus, the leading trunks of the coronary arteries run in the furrows of the heart, usually surrounded by fat. Their numerous branches supply the walls of the auricles and ventricles, and their terminations communicate with each other. CORONARY The vein which corresponds with the anterior VEINS AND SINUS. coronary artery ascends in the anterior inter-ven- tricular sulcus, and then curves round the left side of the heart in the left auriculo-ventricular groove, where it takes the name of the great cardiac vein. This vein soon dilates into a large trunk, the coronary sinus, which opens at the back of the right auricle below the Eustachian valve. Another vein, known as the posterior cardiac, ascends along the posterior inter-ventricular groove, to open by valved orifices into the coronary sinus; while others, the anterior cardiac veins, three or four in number, are seen running up on the anterior surface of the right ventricle to terminate directly in the right auricle. The vence Thebesii transmit the blood directly from the muscular structure into the right auricle by small apertures, the foramina Thebesii. The coronary sinus is about an inch in length, and receives the great cardiac vein, the posterior cardiac vein, and the oblique vein of Marshall, placed on the posterior surface of the left auricle. Its orifice in the right auricle is guarded by a semilunar valve (valve of Thebesius') to prevent re- gurgitation of the blood. It is covered and more or less supported in its course by muscular fibres passing from one auricle to the other. The lymphatics of the heart pass mainly into a trunk which THE HEART. 209 runs in the anterior inter-ventricular groove, and then, passing into the glands between the aorta and trachea, opens into the right lymphatic duct : other smaller lymphatics pass into the thoracic duct. The nerves are derived from the cardiac plexuses, which have been already described, p. 195. FIBROUS RINGS What may be termed the fibrous skeleton of OF THE HEART. the heart, consists of four rings, which surround, respectively, the four orifices at its base : namely, the two auriculo- ventricular, the aortic, and the pulmonary. These rings give FIG. 49. Pulm< cuspid valve litral valve DIAGRAM OF THE^RELATIVE POSITION OF THE VALVES OF THE HEART, SEEN FROM ABOVE. A is placed on the triangular interval where the fibrous skeleton is the thickest. attachment by their external circumference to the muscular fibres of the heart, and from their internal circumference send fibrous prolongations to form the framework of the several valves. The skeleton is strongest just in the triangular interspace between the aortic and the two auriculo-ventricular orifices (letter A in fig. 49). In some animals, as in the ox and the elephant, there is here an irregularly triangular bone, known as the os cordis. The relative position of these rings is best seen by removing the auricles and the great vessels at the base of the heart leaving the several valves 3 and looking at them from above, as shown in P 210 THE HEART. the diagram. The pulmonary ring is on the highest level, and nearest to the sternum ; below it, is the aortic ring lying between and in front of the auriculo-ventricular rings, which are on the lowest level. ATTACHMENT OF ^ e ^rous rings at the arterial orifices present THE LARGE AKTE- three festoons with their concavities directed up- HIES TO THE wards. These give attachment, above, to the middle coat of the artery ; below, to the muscular fibres of the ventricles ; and, internally, to the fibrous tissue of the valves. The vessels are also connected to the heart by the serous layer of the pericardium, and by a continuation of the lining membrane of the ventricle. This, the visceral layer of the pericardium, closely invests the external surface of the heart, and presents the usual appearances of a visceral serous membrane : having externally a layer of polygonal epithelial cells which rest upon a connective tissue layer, intermingled with elastic tissue. Beneath this layer there exists the subserous areolar tissue stratum which is closely connected with the muscular structure of the heart (myocardium), and in which the vessels, nerves, and lymphatics lie imbedded in more or less fat. This smooth membrane lining the cavities of the heart resembles the visceral layer of the peri- cardium, and is continuous with the inner coat of the blood- vessels. It may be easily stripped off, and is thin and semi- transparent, thicker in the left than in the right cavities, thickest of all in the left auricle. It consists of three layers: 1, a layer of flattened polygonal cells, resting upon, 2, a layer of con- nective tissue in which are some elastic fibres resembling the fenestrated coat of an artery; and, 3, a thin layer of connective tissue. The muscular fibres of the heart are of the striped variety, although they are less well marked and regular than in voluntary muscular fibres : the striae are both transverse and longitudinal. The fibres are smaller than in the voluntary kind, have a well marked single nucleus, are branched, and are destitute of sarco- lemma. MUSCULAR FIBRES OF THE HEART. 211 ARRANGEMENT ' ^^ e fibres of the auricles are distinct from those OF THE MUSCULAR of the ventricles. They consist of a superficial FIBRES OF THE layer common to both cavities, and a deeper layer proper to each. The superficial fibres run trans- versely across the auricles, and are most marked on the anterior surface; some pass into the inter-auricular septum. Of the deeper fibres, some are annular and surround the auricular appendages and the entrance of the great veins, upon which a few may be traced for a short distance ; others, looped, run over the auricles, and are attached in front and behind to the auriculo-ventricular rings. ARRANGEMENT Speaking generally, it may be said that the OF THE MUSCULAR right and left ventricles of the heart are two FIBRES OF THE conical muscular sacs, enclosed in a third, which VENTRICLES. not or j v enve i O p es them, but is reflected into the interior of both, at their apices, so as to line their cavities. All the muscular fibres are attached by one end to the fibrous rings of the orifices, and, by the other end, after a more or less spiral course, they reach the rings again, either directly or through the medium of the chordae tendineae and valves. The external or superficial fibres pass from the base, where they are attached to the auriculo-ventricular rings, to the apex. This layer is thin in front, but behind it is better marked, and here the fibres do not pass into the septum, but over it, while in front, they pass over the anterior septum, only at the base and apex of the ventricle. The fibres run more or less spirally towards the apex, where they form a whorl and pass into the left ventricle, so as to form, in part the innermost vertical muscular layer, in part the fleshy columns of its cavity. The superficial anterior fibres pass backwards to the left, and form, behind, the posterior papillary muscle ; and, on the other hand, the superficial posterior fibres pass over the right side of the heart and constitute the anterior papillary muscle. The remaining fibres of the left ventricle, which constitute its chief thickness, are attached to the fibrous rings at the base of the heart. They pass, more or less obliquely, in the posterior and anterior walls, and entering the lower end of the septum pass in three different directions : one set, upwards in the septum to be p 2 212 PECULIARITIES OF THE POSTAL CIRCULATION. attached to the fibrous tissue in the triangular interspace ; a second set pass through the septum to form the posterior wall of the right ventricle and its posterior papillary muscle ; while the third set take a transverse circular course in the left ventricle, some of its fibres being continuous with those of the right ventricle. The fibres of the right ventricle are arranged on a plan similar to that of the left ventricle, of which it may be considered an appendage. The fibres, which correspond to those forming the chief thickness of the left ventricle, are similarly arranged into an anterior, middle and posterior set : the anterior pass backwards into the septum to reach the posterior wall of the left ventricle and interlace in the septum with the posterior set which pass forwards in the septum to the front wall of the left ventricle ; the middle set come chiefly from the outer wall of the right ventricle, deep down at the lower part of the septum, and then ascend to be attached to the fibro-cartilage. Besides these there are more or less numerous annular fibres encircling the right ventricle. 1 THICKNESS OF The average thickness of the right auricle is THE CAVITIES. about one line ; that of the left, one and a half. The average thickness of the right ventricle at its thickest part i.e. the base, is about two lines. That of the left ventricle at its thickest part i.e. the middle is about half an inch. In the female the average is less. PECULIARITIES The heart and the circulation of the foetus OF THE FCETAL differ from that of the adult in the following CIRCULATION. points : 1. The Eustachian valve is well developed as a crescentic fold which guides the current of blood from the inferior vena cava through the right auricle into the foramen ovale. 2. The foramen ovale is widely open up to the fourth month, after which a septum grows up from the lower border of the left side, so that at the sixth month the blood can only pass in the onward direction into the left auricle. 1 There are other accounts given of the arrangements of the muscular struc- ture of the heart, and that given by Pettigrew is one which is adopted .by many of the best anatomists. For further information on this subject consult Pettigrew, Philosoph. Transactions, 1864 ; Dr. Sibson, Medical Anatomy, 1869 ; Winckler, Mailer's Archiv, 1865 ; Quain's Anatomy, vol. ii. p. 495, 1882. FOETAL CIKCULATION. 213 3. The right and left pulmonary arteries are very small and ill developed, so as to admit very little blood to the lungs. 4. The ductus arteriosus, from the commencement of the left pulmonary artery to the aorta, is widely open. 5. The liypocjastric or umbilical arteries, branches of the anterior division of the internal iliac, emerge through the umbilicus and pass to the placenta, so that the impure blood may be oxygenated. 6. The umbilical vein returns the pure blood partly to the liver, and partly through the 7. Ductus venosus into the inferior vena cava. 8. The right and left ventricles are of equal thickness, because they have equal work to perform. FCETAL CIRCULATION. CIKCCLATION OF Arterial blood is brought from the placenta by THE BLOOD IN THE the umbilical vein (fig. 50), and enters at the um- F(ETtTS - bilicus, whence it passes to the under surface of the liver. Here it gives off some branches to the left lobe, and others to the lobulus Spigelii and lobulus quadratus, which eventu- ally return their blood into the inferior vena cava. At the trans- verse fissure it divides into two branches one, the smaller, termed the ductus venosus, passes straight to enter into the inferior vena cava, having previously joined the left hepatic vein ; the other, or right division, joins the vena portse, and, after ramifying in the right lobe of the liver, returns its blood through the hepatic veins into the inferior vena cava. From the inferior vena cava, which thus receives its blood from three sources, the blood enters the right auricle, and the stream (directed by the Eustachian valve) flows through the fora- men ovale into the left auricle, where it becomes mingled with a little blood, which is returned from the pulmonary veins. From the left auricle it runs through the left auriculo-ventricular open- ing into the left ventricle, and thence through the aorta into the great vessels of the head and upper extremities (only a small quantity passing into the descending thoracic aorta), which are 214 FOETAL CIRCULATION. thus supplied by almost pure blood. From the head and upper limbs, the blood returns (impure) through the superior vena cava into the right auricle, whence, mixed with a small quantity derived FIG. 50. SUP R V. C FORAMEN OVALE PLAC ENTA SCHEME OF THE FCETAL CIECULATION. from the inferior cava, it passes into the right ventricle. From the right ventricle the blood passes through the pulmonary artery and the ductus arteriosus into the commencement of the descend- POSTAL CIRCULATION. 215 ing aorta, only a very small quantity of it being distributed to the lungs ; the lungs are in the fetus almost solid organs, and the blood distributed to them is returned by the pulmonary veins into the left auricle. The blood which passes into the descending aorta, through the ductus arteriosus, is mingled with the small amount coming through the arch, and is then conveyed through the ab- dominal aorta into the iliac arteries ; part is transmitted through the umbilical arteries (branches of the internal iliac arteries) to the placenta to become re-oxygenated ; part passes into the lower extremities through the external iliac and femoral arteries. CHANGES IN THH The following changes take place in the circu- CIKCULATION AT lation after birth : l BlRTH - 1. The umbilical vein becomes obliterated from the second to the fifth day after birth, and subsequently forms the round ligament of the liver. 2. The ductus venosus also becomes closed about the same period, and may be traced as a thickened cord in the fissure of the ductus venosus. 3. The foramen ovale becomes closed from the sixth to the tenth day ; but not infrequently a small indirect valvular com- munication may be found forming a communication between the two auricles. 4. The ductus arteriosus contracts immediately after birth, and becomes closed from the sixth to the tenth day. It eventually forms a fibrous cord connecting the left pulmonary artery with the aorta, the left recurrent laryngeal nerve winding round its left border. 5. The pulmonary arteries enlarge and convey venous blood to the lungs. These organs during foetal life receive only a small quantity of blood from these arteries. 6. The liypofjasiric arteries become obliterated on the fourth or fifth day after birth. 1 It is well to bear in mind that these important vascular changes do not take place suddenly at birth, but that they are the result of a gradual development which is completed at, or soon after, birth, mainly by the act of inspiration, whereby the blood passes through the lungs, the placental circulation at the same time being interrupted. 216 THE TRACHEA. STEUCTUEE OF THE LUNGS. The lungs are very vascular spongy organs in which the blood is oxygenated by exposure to atmospheric air. Their situation and shape have been described (p. 166). We must now examine the trachea, the common air-passage to both lungs, and then trace this tube downwards to its bifurcation into the two bronchi, which, with their minute subdivisions, form the main structure of the lungs. This is a partly cartilaginous, partly mem- TBACHEA. , , , , f . ' J ./,, r branous tube, and is situated in the middle line. It extends from the cricoid cartilage, i.e. opposite the upper border of the sixth cervical vertebra, to the third dorsal vertebra, where it divides into two tubes, the right and left bronchus : one for each lung. Its length is from four to four and a half inches, and its width from eight to ten lines ; but these measurements vary according to the age and sex of the patient and the capacity of the lungs. The trachea is surrounded by a quantity of loose connective tissue, so as to allow of its free mobility. It is kept permanently open by a series of incomplete cartilaginous rings, from sixteen to twenty in number, which extend round the anterior two-thirds of its circumference. These rings are deficient at the posterior part of the tube, where it is completed by a fibro-muscular membrane. This deficiency allows the trachea to enlarge or diminish its calibre ; and for this purpose the membranous part of the tube is provided with unstriped muscular fibres which can approximate the ends of the rings. The relations of the trachea to the surrounding parts should be considered, first, in the neck, and then within the thorax. In the neck, kVhas, in front of it, the isthmus of the thyroid body, the sterno-hyoid and sterno-thyroid muscles, the inferior thyroid veins, two layers of the deep cervical fascia, the arteria thyroidea ima, if present, and (at the root of the neck) the innominate and left common carotid arteries. Laterally, it is in relation with the lobes of the thyroid body, the common carotid arteries, the recur- rent laryngeal nerves, and the inferior thyroid arteries. Behind it, is the oesophagus, inclining slightly to the left. THE TRACHEA. 217 In the chest, the trachea is contained in the superior media- stinum, and has, in front of it, the manubrium sterni, the origins of the sterno-hyoid and thyroid muscles, the left brachio-cephalic vein, the first parts of the innominate and left common carotid arteries, the transverse portion of the arch of the aorta, and the deep cardiac plexus. On the right side are the pleura and right pneumogastric nerve ; on the left, the pleura, the left carotid, the left pneumo- gastric, cardiac, and recurrent laryngeal nerves. BRONCHI, EIGHT The two bronchi differ in length, direction, and AND LEFT. diameter. The right, wider but shorter than the left, is about an inch long, and passes more horizontally to the root of its lung, on a level with the fourth dorsal vertebra. It is larger in all its diameters than the left ; hence, foreign bodies which have accidentally dropped into the trachea are more likely to be carried into the right bronchus by the current of the air. The vena azygos major arches over the right bronchus to terminate in the superior vena cava. The left is about two inches in length, and, descending more obliquely to its lung than the right, enters it on a level with the fifth dorsal vertebra. The left bronchus passes under the arch of the aorta, in front of the oesophagus and the thoracic duct, and subsequently crosses in front of the descend- ing aorta. The cartilages of the trachea vary in number from sixteen to twenty, of the right bronchus from six to eight, and of the left from nine to twelve. Those of the trachea form about two-thirds of a circle, somewhat like a horseshoe in shape, are about -\ th of an inch in their vertical direction, and -^th in thickness, and thicker in the middle than at the upper and lower borders. The cartilages are connected and covered on their outer and inner surfaces by a tough membrane, consisting of connective and elastic tissues. This membrane is attached above to the circumference of the cricoid cartilage, and is continued through the whole extent of the trachea and bronchial tubes. Posteriorly, where the cartilages are 'defi- cient, it completes the integrity of the air tube. In this tissue, which is of a pale reddish colour, is a layer of unstriped muscular fibres, arranged in a transverse and a longitudinal direction. The first cartilage is the broadest, and is frequently divided at 218 THE TRACHEA. one end; the last cartilage is placed at the bifurcation of the trachea, and is shaped like the letter y ; its angle projects into the centre of the main tube, and its sides belong one to each bronchus. MUSCULAB This thin stratum of unstriped muscular fibres FIBRES, consists of two layers, and is brought into view when the fibrous membrane and tracheal glands have been removed. The longitudinal fibres are the more external, and are attached by minute tendons to the extremities of the cartilages ; the trans- verse fibres (trachealis muscle) extend transversely between the posterior free ends of the cartilages. By their contraction they approximate the ends of the cartilages and diminish the calibre of the trachea. This lines the whole tube, but is most abundant at the posterior or membranous part of the trachea, and its fibres run in a longitudinal direction. It is this layer which raises the mucous membrane into folds, and its elasticity admits of the elongation and the recoil of the tube. TRACHEAL Upon the outer surface of the fibrous layer of GLANDS. the trachea are a number of small mucous glands, most numerous on the posterior part of the tube. They are com- pound racemose glands lined with columnar epithelium, and their excretory ducts pierce the fibrous and muscular layers, and termi- nate on the free surface of the mucous membrane. In health their secretion is clear, and just sufficient to lubricate the air-passages. In bronchitis they are the sources of the abundant viscid expectoration. Mucous MEM- The mucous membrane lining the air-passages BBANE. is a continuation of that of the larynx. Its colour in the natural state is nearly white, but in catarrhal affections it becomes bright red, in consequence of the accumulation of blood in the capillary vessels. It is continued into the ultimate air-cells, where it becomes thinner and more transparent. In its deeper layer is found a considerable amount of elastic tissue ; in its super- ficial layer a quantity of lymphoid tissue. Its surface is lined with a layer of columnar ciliated epithelial cells. The vibratile movement of the cilia is directed in such a way as to favour the STRUCTURE OF THE LUNGS. 219 expectoration of the mucus. The ciliated epithelium lining the mucous membrane ceases at the commencement of the air-cells, where it is replaced by the squamous variety. At the root of the lung each bronchus divides into two branches, an upper and a lower, corresponding to the lobes of the lung ; on the right side, the lower branch sends a small division to the third lobe of the lung. The tubes diverge through the lung, and divide into branches, successively smaller and smaller, until they lead to the air-cells. These ramifications do not communicate with each other ; hence, when a bronchial tube is obstructed, all supply of air is cut off from those cells to which it leads. The several tissues cartilaginous, fibrous, muscular, mucous, and glandular which compose the air-passages, are not present in equal proportions throughout all their ramifications, but each is placed in greater or less amount where it is required. The car- tilaginous rings necessary to keep the larger tubes permanently open become, in the smaller tubes, fewer and less regular in form. As the subdivisions of the tubes multiply, the cartilages consist of small pieces placed here and there ; they become less and less firm, and finally disappear when the tube is reduced to one-fortieth of an inch in diameter. The smallest air-passages are entirely mem- branous, being formed of fibrous, elastic, and muscular tissues. The lungs are two in number, and occupy the lateral cavities of the chest. Each is conical in shape, its apex extending into the neck, the base resting n the upper or convex surface of the diaphragm. The lung presents for examination an apex, a base, two surfaces, and two borders. The apex extends upwards about an inch and a half above the first rib, and is generally marked by a slight groove for the sub- clavian artery. The lose is concave, and slopes downwards at its posterior part. Its outer surface, in contact with the chest wall, is smooth and convex, and is deeper behind than in front. Its inner surface is concave, and hollowed out to accommodate the heart and its large vessels. Its anterior border is sharp and overlaps the large vessels and the pericardium. The posterior border is rounded and rests in the broad groove on the side of the bodies of the dorsal vertebrae. On the inner concave surface, a little above the middle 220 STRUCTURE OF THE LUNGS. and nearer the posterior than the anterior border, is the root, where the large vessels and bronchi pass to and from the lungs. Each lung is traversed on its external surface by an oblique fissure which passes deeply into its interior. It extends from the upper part of the posterior border, downwards and forwards to the anterior border, and on the right side there is a second fissure passing, forwards and upwards from the oblique fissure, to the middle of the anterior margin. The left lung presents a deep notch in the anterior border in which the pericardium is seen as far as the apex of the heart. CONTBACTIBI- When an opening is made into the chest, the LITY OF THK l 1111 ^ which was in contact with the ribs, imme- LcNO> diately recedes from' them, and, provided there be no adhesions, gradually contracts. If the lungs be artificially inflated, either in or out of the chest, we observe that they sponta- neously expel a part of the air. This disposition to contract, in the living and the dead lung, is due to the elastic tissue in the bronchial tubes and the air-cells ; but more especially to a layer of delicate elastic tissue on the surface of the lung, which has been described by some anatomists as a distinct coat, under the name of the second or inner layer of the pleura. 1 The lungs are of a livid red or violet colour ; they often present a mixture of tints, giving them a marble-like appearance. This is not the natural colour of the organ, since it is produced in the act of dying. It depends upon the stagnation of the venous blood, which the right ventricle still propels into the lungs, though respiration is failing. The tint varies in particular situations in proportion to the amount of blood, and is always deepest at the back of the lung. But the colour of the proper tissue of the lung, apart from the blood which it con- tains, is pale and light grey. This colour is seldom seen except in the lungs of infants who have never breathed, or after death from profuse haemorrhage. Upon or near the surface of the lungs, numerous dark spots are observed which do not depend upon the blood, since they are 1 In some animals, the seal especially, the elasticity of this tissue is very strongly marked. STRUCTURE OF THE LUNGS. 221 seen in the palest lungs. They vary in number and size, and in- crease with age. The source of these discolorations is not exactly known ; but they are probably deposits of minute particles of car- bonaceous matter which have been inhaled with the air. The lungs are composed of cartilaginous and membranous tubes, of which the successive subdivisions convey the air into closely- packed minute cells, called the air-vesicles ; of the ramifications of the pulmonary artery and veins ; of the bronchial vessels concerned in their nutrition ; of lymphatics and nerves. These component parts are united by connective tissue, and covered externally by pleura. The part at which they respectively pass in and out is called the root of the lung. The lungs are the lightest organs in the body, and float in water, their specific gravity varying from '345 to '746. When entirely deprived of air they sink. This is observed in certain pathological conditions ; e.g. when one lung is compressed by effu- sion into the chest, or rendered solid by inflammation. In the male the average weight of the right lung is 22 oz., that of the left 20 oz. ; in the female the average is about 17 oz. on the right, and 15 oz. on the left side. The total capacity of the lungs in an adult male of ordinary height is 282 cubic inches ; and the amount of air still contained in the lungs after a forced expiration has been estimated at 57 cubic inches. The difference between these volumes viz. 225 cubic inches indicates the amount of air which can be inhaled, from the deepest expiration to the fullest inspiration, and has been termed the vital capacity of the lungs. 1 The surface of the lung is closely invested by a thin transpa- rent layer of serous membrane, immediately beneath which is a fine areolar tissue, called subserous, which is very soft and elastic so as to allow of the free expansion of the organ. This tissue sends inwards prolongations, called interlobular, which map out the lungs into a number of angular spaces of various sizes termed lobules : those on the surface, indicated by faint white lines, are larger than those in the interior of the lung. Each lobule is a lung in miniature, and consists of a small bronchial tube and its termination in dilated 1 Hutchinson, Med. Chir. Trans., vol. xxix., 1846. 222 STRUCTURE OF THE LUNGS. FIG. 61. extremities, called infundibula, of ramifications of the pulmonary vessels, lymphatics, and nerves, and, lastly, of the bronchial vessels. The cells of the interlobular tissue have no communication with the air-vesicles, unless the latter be ruptured by excessive straining, and then this connective tissue becomes inflated with air and is called interlobular emphysema. When infiltrated with serum it constitutes oedema of the lung. Each bronchial tube divides and subdivides into smaller and smaller divergent tubes, until each has reached a reduced size of about 1 mm. ; it then enters a pul- monary lobule, when it is termed a lobular bronchial tube, and presents on its walls numerous dilatations, called air-cells or alveoli, which vary from -^ to -^ of an inch in diameter (fig. 51). Thus reduced f in size, the walls of the tubes no longer present traces of cartilaginous tissue, but are com- posed of a delicate elastic membrane upon which the capillaries ramify in a very minute network. 1 Each tube finally terminates in an enlarged ir- regular passage alveolar passage from which proceed on all sides nume- rous blind dilatations, named infundi- bula. The smaller bronchial tubes are encircled by more or less complete rings of cartilage ; but as the tubes lessen in calibre, the rings become less perfect ; so that when the tubes are reduced to ^th of an inch in diameter the rings entirely disappear. The continuation of the air-tubes consists simply -of fibrous tissue which becomes gradually thinner, so that in the smallest tubes they are reduced to simply membranous tubes, and are continued on as irregular passages intercellular 1 In phthisis the expectoration contains some of the dtbris of this elastic framework of the air-vesicles ; it can be seen under the microscope, and is a test of the character of the sputa. ULTIMATE AIR-CELLS OF THE LUNG (FROM KSLLIKER). MAGNIFIED TWENTY-FIVE TIMES. STRUCTURE OF THE LUNGS. 223 passages l which are studded with numerous small saccules termed air-cells or alveoli. The air-cells are small, shallow, polyhedral depressions, from ^th to --fro-th of an inch in diameter, separated by thin partitions or septa which communicate freely with the intercellular passages, but not with each other. 2 The mucous membrane which invests the divisions of the bronchi as far as the intercellular passages is lined with epithelium of the columnar ciliated variety. At this situation the character of the epithelium changes to that of a squamous kind consisting of a single layer of flat polygonal nucleated cells. The structure of the air-cells differs in some important features from that of the smaller bronchial tubes ; the muscular tissue dis- appears, the elastic tissue is no longer arranged in bundles, but becomes frayed out and intermingled with the connective tissue. PULMONARY The pulmonary artery conveying venous blood VESSELS. to the lungs divides and subdivides with the bronchial tubes, and terminates in a fine dense capillary plexus on the walls of the intercellular passages and air cells, beneath the epithelium. These plexuses the pulmonary capillaries form a single layer of capillaries which is so close that the interstices are even narrower than the blood-vessels, which average about - 3 * of an inch in diameter. The plexus which ramifies over the air cell does not communicate with the plexus covering another air cell. The blood and air are not in actual contact. Nothing, however, intervenes but the wall of the cell and the capillary vessels, which are such delicate structures that they oppose no obstacle to the free interchange of gases by which the blood is purified. This purifi- cation is effected by the taking in of oxygen, and the elimination of carbonic acid and watery vapour. The most complete purifica- tion takes place in the single layer of capillaries between the folds of membrane projecting into the cell ; for in this situation both sides of these vessels are exposed to the action of the air. The blood, circulating in steady streams through this capillary plexus, 1 Kainey, Med. Chir. Trans., vol. xxviii., 1845. 2 The structure of the minute air-cells of the human lung is in all respects similar to the large respiratory sac of the reptile. 224 DISSECTION OF THE PHARYNX. returns through the pulmonary veins. These, at first extremely- minute, gradually coalesce into larger and larger branches which anastomose very freely, and accompany the arteries. They finally emerge from the root of the lung by two large trunks which carry the oxygenated blood to the left auricle of the heart. The pul- monary veins are not provided with valves. ' BRONCHIAL These small arteries, two or more in number, ARTERIES. are the nutrient vessels of the lungs. The right arises either from the first aortic intercostal, or, conjointly with the left bronchial, from the thoracic aorta. The left, usually two in number, come from the thoracic aorta. .They enter the lung behind the divisions of the bronchi, which they accompany. The bronchial vessels are distributed in various ways : some of their branches supply the coats of the air-passages, the large blood- vessels and the lymphatic glands ; others the interlobular tissue : a few reach the surface of the lung, and ramify beneath the pleura. The right bronchial veins terminate in the vena azygos ; the left, in the superior intercostal vein. The nerves of the lung are derived from the pneumogastric and the sympathetic. They enter with the bronchial tubes, forming a plexus in front and behind them, anterior and posterior pulmonary plexus, in which are found minute ganglia. The lymphatics of the lungs consist of a superficial and deep set : some commence in the lymphatic capillaries in the inter- lobular tissue, and thence pass to the surface, forming a network which communicates with the subpleural lymphatic plexus ; others take their origin in the mucous membrane of the bronchial tubes ; and all eventually enter the bronchial glands. Of these, the larger are situated about the bronchi near the root of the lung, parti- cularly under the bifurcation of the trachea. DISSECTION OF THE PHAEYNX. To obtain a view of the pharynx, cut through the trachea, the oesophagus, the large vessels and nerves of the neck, a short distance above the first rib, and then THE PHARYNX. 225 'separate them from the prevertebral muscles which lie immediately in front of the bodies of the cervical vertebras, and to which they are but loosely connected. The sawn surface of the skull should now be allowed to rest horizontally upon the table, and the base should then be sawn or chiselled through transversely between the vertebral column and the styloid processes of the temporal bone. It is not always easy to keep the saw so well behind the pharynx and the vessels and nerves as to detach them without injury, in which case it is well to use the chisel in preference. When this is accom- plished the student will find that the pharynx and larynx are left attached to the anterior half of the section; the spinal column and the prevertebral muscles to the posterior half. Tow should then be introduced through the mouth and oesophagus to distend the walls of the pharynx. The front section is now to be fastened to a block by means of hooks, so that the pharyngeal muscles are towards the dissector, and the oesophagus downwards. One side of the pharynx should be dissected to show the con- strictor muscles, the other should be reserved for the vessels and nerves in immediate relation with the pharynx. GENERAL DE- ^ ne term pharynx is applied to that part of the SCRIPTION OF alimentary canal which receives the food after it PHARYNX. ^as been masticated, and propels it downwards into the ossophagus. It is a funnel-shaped muscula rbag, about four and a half inches in length, and broader in its transverse than in its antero-posterior diameter. Its broadest portion is situated opposite the os hyoides, and it then gradually tapers as far as the cricoid cartilage, where it is continuous with the oesophagus, which is its narrowest portion. Its upper part is attached to the basi- lar process of the occipital bone and the petrous portions of the temporal bones ; behind, it is loosely connected by deep cervical fascia with the prevertebral muscles ; l in front, it is attached to the internal pterygoid plates and hamular processes of the sphenoid, to the pterygo-maxillary ligaments, the lower jaw, the tongue, the hyoid bone, and the stylo-hyoid ligaments, and to the thyroid and cricoid cartilages; laterally, it is loosely connected 1 It is in this tissue (which never contains fat) that post-pharyngeal abscesses are seated. 226 THE PHARYNX. to the styloid muscles, and it has in close relation with it, the common and internal carotid arteries, the glosso-pharyngeal, pneumogastric, spinal accessory, hypoglossal and sympathetic nerves ; the internal pterygoid, tensor palati and stylo-pharyngeus muscles ; the lingual and ascending pharyngeal arteries, the superior laryngeal and external laryngeal nerves, the ascending palatine artery, and the internal jugular vein. Its dimensions are not equal throughout. Its breadth at the upper part is equal to that of the posterior openings of the nose : here it is only required to convey air, but it becomes much wider in the situation where it transmits the food that is, at the back of the mouth ; thence it gradually contracts to the oesophagus. The pharynx, therefore, may be compared to a funnel communicating in front by wide apertures with the nose, the mouth, and the larynx; while the oesophagus represents the tube leading from its lower end. The upper part of the funnel forms a cul-de-sac at the basilar process of the occipital bone. At this part there is, on each side, the opening of a narrow canal, called the Eustachian tube, through which air passes to the tympanum of the ear. 1 Before the muscles of the pharynx can be examined, we must remove a layer of thin fascia, termed the pharyngeal fascia. It is the layer of deep cervical fascia behind the pharynx, and must not be confounded with the proper pharyngeal aponeurosis, which intervenes between its muscular and mucous walls. At the back of the pharynx, near the base of the skull, are a few lymphatic glands. They sometimes enlarge, and form a, perceptible tumour in the pharynx. In removing the fascia from the pharyngeal muscles, notice 1 Observe that the pharynx conducts to the oesophagus by a gradual contraction of its channel. This transition, however, is in some cases sufficiently abrupt to. detain a foreign body, such as a morsel of food more bulky than usual, at the top of the oesophagus. If such a substance become firmly impacted in this situation, one can readily understand that it will not only prevent the descent of food into the stomach, but that it may occasion, by its pressure on the trachea, alarming symptoms of suffocation. Supposing that the obstacle can neither be removed by the forceps, nor pushed into the stomach by the probang, it may then become necessary to extract it by making an incision into the oesophagus on the left side of the neck. CONSTRICTOR MUSCLES OF THE PHARYNX. 227 PHARYNX. that a number of veins ramify and communicate in all directions. They constitute the pharyngeal venous plexus, and terminate in the internal jugular veins. CONSTRICTOR They are three in number, and arranged so that MUSCLES OF THE they overlap each other i.e. the inferior overlaps the middle, and the middle the superior (fig. 52). FIG. 52. J\J> Tensor palati. Levator palati. Orbicularis oris . . Pterygo-maxillary ) ligament . . j Mylo-hyoideus . Os hyoides . . Thyro-hyoid liga- ment .... Pomum Adami . Cricoid cartilage Trachea . . .Glosso-pbaryngeal n. Stylo-pharyngeus. Superior laryngeal u. and a. External laryngeal r. - Crico-thyroideus. Inferior laryngeal n. (Esophagus. SIDE VIEW OF THE MUSCLES OF THE PHABYNX. They have the same attachments on both sides of the body ; and the fibres from the right and left meet together, and are inserted Q 2 228 CONSTRICTOR MUSCLES OF THE PHARYNX. in the mesial line, the insertion being marked by a white longitu- dinal line, called the raphe. The inferior constrictor, the most superficial and thickest of the thin constrictors, arises from the side of the cricoid cartilage behind the crico-thyroid muscle, from the surface behind the oblique ridge and the lower cornu of the thyroid cartilage. Its fibres expand over the lower part of the pharynx. The superior fibres ascend ; the middle run transversely ; the inferior descend slightly, and are inserted into the posterior median raphe. The lower fibres are continuous with those of the oesophagus. Beneath its lower border the recurrent laryngeal nerve enters the larynx. Its nerve-supply is from the pharyngeal plexus, the external laryngeal and the recurrent laryngeal nerves. In order to completely expose the next muscle, the right half of the inferior constrictor should be reflected from the middle line. The middle constrictor arises from the upper edge of the greater cornu of the os hyoides, from its lesser cornu, and part of the stylo- hyoid ligament, and is inserted into the posterior median raphe. Its fibres take different directions, so that, with those of the opposite muscle, they form a lozenge. The lower angle of the lozenge is covered by the inferior constrictor; the upper angle ascends nearly to the basilar process of the occipital bone, and terminates upon the pharyngeal aponeurosis. The external surface of the muscle is covered at its origin by the hyo-glossus, from which it is separated by the lingual artery ; while beneath it are the superior constrictor, the stylo-pharyngeus, and palato-pharyn- geus muscles and the pharyngeal aponeurosis. Its nerve comes from the pharyngeal plexus. Between the middle and inferior constrictors, the superior laryngeal artery and nerve perforate the thyro-hyoid membrane to supply the larynx. The superior constrictor consists of pale muscular fibres, and arises from the hamular process of the sphenoid bone, and from the lower part of its internal pterygoid plate ; from the tuberosity of the palate bone and the reflected tendon of the tensor palati ; from the pterygo-maxillary ligament (which connects it with the buccinator) ; from the back part of the ruylo-hyoid ridge of the lower jaw, and from the side of the tongue. The fibres pass back- CONSTRICTOR MUSCLES OF THE PHARYNX. 229 wards to the mesial raphe : some of them are inserted through the medium of the pharyngeal aponeurosis into the basil ar process. Its nerve comes from the pharyngeal plexus. The upper border of the superior constrictor presents, on either side, a free semilunar edge with its concavity upwards, so that, FIG. 53. VIEW OF THE CONSTRICTOR MUSCLES FROM BEHIND. between it and the base of the skull, a space is left in which the muscle is deficient (fig. 53). Here the pharynx is strengthened and walled in by its own aponeurosis. The space is called the sinus of Morgagni ; and in it, with a little dissection, we expose the muscles which raise and tighten the soft palate: i.e. the levator palati and the tensor palati. The Eustachian tube opens into the 230 OPENINGS INTO THE PHARYNX. pharynx just here. The fibres of the stylo-pharyngeus pass in between the superior and middle constrictors, and expand upon the side of the pharynx ; some of them mingle with those of the con- strictors, so as to be able to lift up the pharynx in deglutition ; but most of them are inserted into the superior and posterior margins of the thyroid cartilage. PHARYNGEAL The pharyngeal aponeurosis intervenes between APONEUBOSIS. the muscles and the mucous membrane of the pharynx. It is attached to the basilar process of the occipital bone, and to the points of the petrous portions of the temporal bones. It maintains the strength and integrity of the pharynx at its upper part, where the muscular fibres are deficient ; but it gradually diminishes in thickness as it descends, and is finally lost on the oesophagus. Notice the number of mucous glands upon this aponeurosis, especially near the base of the skull and the Eustachian tube. These glands sometimes enlarge and occasion deafness from the pressure on the tube. OPENINGS INTO Lay open the pharynx by a longitudinal incision THE PHARYNX. in the middle line, up to the pharyngeal tubercle ; then divide transversely, for a short distance, that part of the pharyngeal aponeurosis which is attached to the basilar process, so as the better to view the cavity of the pharynx. Observe the seven openings leading into it (fig. 54) : 1. The two posterior nares: below the nares is the soft palate, with the uvula. 2. On either side of them, near the lower turbinated bones, are the openings of the Eustachian tubes. 3. Below the soft palate is the communication with the mouth, called the isthmus faucium. On either side of this are two folds of mucous membrane, constituting the anterior and posterior half-arches of the palate ; between them are the tonsils. Below the isthmus faucium is the epiglottis, which is connected to the base of the tongue by three folds of mucous membrane. 4. Below the epiglottis is the aperture of the larynx. 5. Lastly, is the opening into the oesophagus. 1 1 On reflecting the mucous membrane at the pharyngeal termination of the Eustachian tube, a thin pale muscle, the salpingo-pharyngeus, can be made out. It arises by a thin tendon from the Eustachian tube, and joins the palato-pharyn- geus. It is lost among the fibres of the constrictor muscles. MUCOUS MEMBRANE OF THE PHARYNX. 231 The pharynx consists of three coats, viz., muscular, fibrous and Ynucous. The two former have been already described. Mucous The mucous membrane is common to the en- MEMBRANE. tire tract of the respiratory passages and the ali- Eustachian tube. Levator palati m. L Tensor palati m. Hamular process. Posterior palatine arch. Tonsil. Anterior palatine arch. Epiglottis. Aryteno-epiglottidean fold. Opening into the larynx. Opening into the oesophagus. DIAGRAMMATIC VIEW OF THE PHARYNX LAID OPEN FROM BEHIND. mentary canal. This membrane, however, presents varieties in the different parts of these channels, according as they are intended as passages for air or for food. The mucous membrane of the pharynx 232 THE SOFT PALATE. above the velum palati, being intended to transmit air only, is very delicate in its texture, and lined by columnar ciliated epithelium like the rest of the air-passages. But opposite the fauces, the mucous membrane resembles that of the mouth, and is provided with squamous epithelium. At the back of the larynx the mem- brane is corrugated into folds, to allow the expansion of the pharynx during the passage of the food. The membrane is lubricated by a secretion from the nume- rous mucous glands which are situated in the submucous tissue throughout the whole extent of the pharynx, particularly in the neighbourhood of the Eustachian tubes. 1 POSTERIOR These are two oval openings, each of which is OPENINGS OF THE about an inch in the long, and half an inch in the NASAL Foss^. short diameter. They are bounded above by the body of the sphenoid bone, externally by its pterygoid plate, below by the horizontal portion of the palate bone ; they are separated from each other by the vomer. On removing the mucous membrane from the posterior part of the roof of the nose and the top of the pharynx, you will find beneath it much fibrous tissue. Hence polypi growing from these parts are, generally, of a fibrous nature. ISTHMUS This name is given to the opening by which FAUCIUM. the mouth communicates with the pharynx. It is bounded, above by the soft palate and uvula, below by the root of the tongue, and on either side by the arches of the palate, enclosing the tonsils between them. SOFT PALATE, OB This moveable prolongation of the roof of the VELUM PENDULUM mouth is attached to the border of the hard PALATI. palate, and laterally to the side of the pharynx. Posteriorly it has a free edge, with a pendulous conical projection in the centre, called the uvula. It constitutes an imperfect parti- tion between the mouth and the posterior nares. Its upper or nasal surface is convex and continuous with the floor of the nose ; its lower surface is concave, in adaptation to the back of the tongue, and is marked in the middle by a ridge or raphe, indicat- ing its original formation by two lateral halves. The soft palate, 1 This aggregation of mucous glands is called the pharyngeal tonsil. ARCHES OF THE SOFT PALATE. 233 when at rest, hangs obliquely downwards and backwards ; but in swallowing, it is raised to the horizontal position by the levatores palati, comes into apposition with the back of the pharynx, and thus prevents the food from passing through the nose. On making a perpendicular section through the soft palate, you come first upon the oral mucous membrane ; then you see that the great bulk of it is made up of muciparous glands, which lie thick on its under surface to lubricate the passage of the food. Above these glands is the thin layer of the palato-glossus, then the insertion of the tensor palati forming the broad aponeurosis of the palate ; still higher, are the two portions of the palato-pharyn- geus, separated by the fibres of the levator palati, the azygos uvulse, and, lastly, the nasal mucous membrane. The soft palate is sup- plied with blood by the descending palatine branch of the internal maxillary, the ascending palatine branch of the facial, the ascend- ing pharyngeal and the dorsales linguae of the lingual artery. Its nerves are derived from the palatine branches of the superior maxillary division of the fifth and from the glosso-pharyngeal. The uvula projects from the middle of the soft palate, and gives the free edge of it the appearance of a double arch. It contains a number of muciparous glands, and a small muscle, the azygos uvulce. Its length varies according to the state of its muscle. It occasionally becomes permanently elon- gated, and causes considerable irritation, a tickle in the throat, and harassing cough. When you have to remove a portion of it, cut off only the redundant mucous membrane. ARCHES OR ^ ne so ft P a ^ e is connected with the tongue PILLARS OF THE and pharynx by two folds of mucous membrane PALATE. on eac h side, enclosing muscular fibres. These are the anterior and posterior arches or pillars of the palate. The ante- rior arch describes a curve downwards and forwards, from the base of the uvula to the side of the tongue. It is well seen when the tongue is extruded. The posterior arch, commencing at the side of the uvula, curves downwards and backwards, along the free margin of the palate, and terminates on the side of the pharynx. The posterior arches, when the tongue is depressed, can be seen through the span of the anterior. The pillars of each side diverge from 234 MUSCLES OF THE SOFT PALATE. their origin, and in the triangular space thus formed is situated the tonsil. The chief use of the arches of the palate is to assist in deglutition. The anterior, enclosing the palato-glossi muscles, con- tract so as to prevent the food from coming back into the mouth ; the posterior, enclosing the palato-pliaryngei, contract like side curtains, and co-operate in preventing the food from passing into the nose. In vomiting, food does sometimes escape through the nostrils, but one cannot wonder at this, considering the violence with which it is driven into the pharynx. MUSCLES OF THE The muscles of the soft palate lie immediately SOFT PALATE. beneath the mucous membrane. There are five pairs namely, the levatores palati, the circumflexi or tensores palati, the palato-glossi, the palato-pharyngei, and the azygos uvulee. This last pair is sometimes described as a single muscle. To clean the muscles, the soft palate should be made tense by means of hooks, as they are severally dissected. This muscle arises from the under aspect of the LEVATOB PALATI. ,, , . . . apex oi the petrous portion of the temporal bone, and from the under part of the cartilage of the Eustachian tube. It descends obliquely inwards, and then passes over the concave border of the superior constrictor into the pharynx, where its fibres spread out and are inserted along the upper surface of the soft palate below the azygos uvulse, meeting those of its fellow in the middle line (fig. 54). Its action is to raise the soft palate, so as to make it horizontal in deglutition. It is supplied by the descending palatine branch from the spheno-palatine ganglion. CIECUMFLEXUS This muscle is situated between the internal OR TENSOR PALATI. pterygoid m. and the internal pterygoid plate of the sphenoid bone. It arises by a flattened muscular belly from the scaphoid fossa, and from the spine of the sphenoid ; from the vaginal process of the temporal bone and from the outer and anterior side of the cartilage of the Eustachian tube. Thence it descends perpendicularly, and ends in a tendon which winds round the hamular process, where there is a synovial bursa. Now chang- ing its direction, the tendon passes horizontally inwards, and expands into a broad aponeurosis, which is inserted into the horizontal plate of the palate bone, and is also connected to its THE TONSILS. 235 fellow of the opposite side. It gives strength to the soft palate. A synovial membrane facilitates the play of the tendon round the hanralar process. Its action is to draw down and tighten the soft palate, and, owing to its insertion into the palate bone, also to keep the Eustachian tube open. Its nerve is derived from the otic ganglion, and enters the muscle on its inner aspect. AZYGOS OB This consists of two thin bundles of parallel LEVATOB UVUM:. muscular fibres situated one on each side of the middle line. It arises from the aponeurosis of the palate and de- scends along the uvula nearly down to its extremity. It receives its nerve from the descending palatine branch of the spheno- palatine ganglion. PALATO-GLOSSUS These muscles are contained within the arches AND PALATO- of the soft palate, and the mucous membrane must PHABYNGEUS. |-, e re moved in order to expose them. The -palaio- glossus, within the anterior arch, proceeds from the anterior surface of the soft palate to the side of the tongue, and is lost in the stylo- glossus muscle. The palato-pliarynfjeus, within the posterior arch, arises from the posterior border of the soft palate by two origins, separated by the levator palati. As it descends its fibres spread out and, passing along the side of the pharynx, blend with the fibres of the inferior constrictor and the stylo-pharyngeus. Both these muscles are supplied by the descending palatine branches of the spheno-palatine ganglion. The tonsils are two glandular bodies, situated at the entrance of the fauces, between the arches of the soft palate. They are rounded in shape, and their use is to lubricate the fauces during the passage of the food. On their inner surface are visible from twelve to fifteen orifices leading into crypts, which make the tonsil appear like the shell of an almond. Hence, as well as from their oval figure, they are called the amyydalce. These openings lead into small follicles in the substance of the tonsil, lined by mucous membrane. Their walls are thick, and around them is a layer of closed cells (like Peyer's glands) situated in the submucous tissue. The fluid secreted by these cells is viscid and transparent, in the healthy state : but it is apt to become 236 EUSTACHIAN TUBE. white and opaque in inflammatory affections of the tonsils, and occasionally accumulates in these superficial depressions, giving rise to the deceptive appearance of a small ulcer, or a slough, or even a false membrane on the part. The tonsil lies close to the inner side of the internal carotid artery. It is only separated from this vessel by the ascending pharyngeal artery, the superior constrictor, and the aponeurosis of the pharynx. Therefore, in removing a portion of the tonsil, or in opening an abscess near it, the point of the instrument should never be directed outwards, but inwards towards the mesial line. 1 The tonsil is supplied with blood by the tonsillar and palatine branches of the facial, and by the descending palatine branch of the internal maxillary. Nerves are furnished to it from the glosso- pharyngeal and from Meckel's ganglion. EUSTACHIAN This canal conveys air from the pharynx to the TUBE, tympanum. Its orifice is situated opposite the back part of the inferior spongy bone. The direction of the tube from the pharynx is upwards, backwards, and outwards ; it is an inch and a half long. The narrowest part is about the middle, and here its walls are in contact. Near the tympanum its walls are osseous, but towards the pharynx they are composed of fibro- cartilage and fibrous membrane. The cartilaginous end, about an inch in length, projects between the origins of the levator and the tensor palati, and gives attachment to some of their fibres. It is situated at the base of the skull, in the furrow between the petrous portion of the temporal and the great wing of the sphenoid bone. It adheres closely to the bony furrow, as well as to the fibro- cartilage filling up the foramen lacerum medium. The orifice is not trumpet-shaped, as usually described, but an elliptical slit about half an inch long^ and nearly perpendicular. The fibro- cartilage bounds it only on the inner and the upper part of the 1 Cases are related by Portal and Beclard, in which the carotid artery was punctured in opening an abscess in the tonsil. The result was immediately fatal haemorrhage. It should, however, be borne in mind that the artery usually injured is the tonsillar branch of the facial artery, and not the internal carotid. The surgical treatment of this accident is therefore ligature of the external carotid artery between its superior thyroid and lingual branches, and not ligature of the common carotid artery as is often recommended. MECHANISM OF DEGLUTITION. 237 circumference ; the integrity of the canal below is maintained by tough fibrous membrane. The Eustachian tube is lined by a continuation of the mucous membrane of the pharynx, and covered by ciliated epithelium. That which lines the cartilaginous portion of the tube is thick and vascular, and gradually becomes thinner towards the tympanum. Hence, inflammatory affections of the throat or tonsils are liable to l)e attended with deafness, from temporary obstruction of the tube. Mucous glands surround the orifice of the tube, and are similar in nature and function to the glands beneath the mucous membrane of the mouth, the palate, and the pharynx. The hard palate, formed by the superior maxil- lary and palate bones, is a resisting surface for the tongue in tasting, in mastication, in deglutition, and in the articu- lation of sounds. The tissue covering the bones is thick and close in texture, and firmly united to the asperities on the bones. But it is not everywhere of equal thickness. Along the raphe in the mesial line, it is much thinner than at the sides ; for this reason, the hard palate is in this situation more prone to be perforated in syphilitic disease. A thick layer of glands (glandulce palatince) is arranged in rows on either side of the hard palate. These glands become more numerous and larger towards the soft palate. Their orifices are visible to the naked eye. The mucous membrane has a very thick epithelial coat, which gives the white colour to the palate. The descending palatine branch of the internal maxillary artery, and the palatine nerves from the superior maxillary, may be traced along each side of the roof of the mouth. The ramifications of these arteries and nerves supply the soft as well as the hard palate. MECHANISM OF With the anatomy of the parts fresh in your DEGLUTITION. mind, consider for a moment the mechanism, of deglutition. The food, duly masticated, is collected into a mass upon the back of the tongue ; the lower jaw is then closed to give a fixed point for the action of the muscles which raise the os hyoides and larynx, and the food is carried back into the pharynx by the pressure of the tongue against the palate, at the same time that the pharynx is elevated and expanded to receive it (by 238 DISSECTION OF THE LARYNX. the stylo-pharyngei on each side). 1 The food, having reached the pharynx, is prevented from ascending into the nasal passages by the approximation of the posterior palatine arches, and the eleva- tion of the soft palate, which thus forms a horizontal temporary roof to the pharynx; it is prevented from returning into the mouth by the pressure of the retracted tongue, and the contraction of the anterior palatine arches : it cannot enter the larynx, because its upper opening is closed and protected by the falling of the epiglottis : - consequently, being forcibly compressed by the con- strictors of the pharynx, the food passes into the oesophagus, through which it is conveyed into the stomach by the undulatory contraction of that tube. The food passes with different degrees of rapidity through the different parts of its course ; but most rapidly through the pharynx. The necessity of this is obvious, as the air-tube must be closed while the food passes over it, and the closure produces a temporary interruption to respiration. The progress of the food through the oesophagus is slow and gradual. DISSECTION OP THE LAEYNX. SITUATION AND The larynx is the upper dilated part of the EELATIONS. windpipe, in which phonation takes place. It consists of numerous cartilages articulated together to form an open tube, and to protect the delicate structures concerned in vocalisation. It forms a prominence in the middle line of the neck, covered in front by the integument and cervical fasciae, the sterno-hyoid, sterno-thyroid, and thyro-hyoid muscles, and the thyroid body. It has the large vessels of the neck on each side. Above, it is attached to the hyoid bone ; below, it is continuous with the 1 The larynx being also elevated and drawn forward, a greater space is thus left between it and the vertebrae for the distention of the pharynx. 2 This falling of the epiglottis is effected, not by special muscular agency, but by the simultaneous elevation of the larynx and the retraction of the tongue. A perpendicular section through all the parts concerned is necessary to show the working of this mechanism. LIGAMENTS OF THE OS HYOIDES. trachea ; behind it, is the pharynx, into the anterior part of which it opens. Before commencing the dissection of the larynx, the student should make himself acquainted with the cartilages which compose- it, and the ligaments which connect them, as seen in a dry pre- paration. This bone, named from its resemblance to the Greek Upsilon, is situated between the larynx and the tongue, and serves for the attachment of the muscles of the tongue. It may be felt immediately below, and one inch and a half behind, the symphysis of the jaw. It is arched in shape, and consists of a body, two greater and two lesser cornua. The body (basi-hyafy is the thick central portion. Its anterior surface is convex, and has a median vertical ridge : on each side of which are depressions for the attachments of muscles; its posterior surface is smooth, deeply concave, and corresponds to the epi- glottis. The greater cornua (thyro-hyals), right and left, project backwards for about an inch and a half, with a slight inclination upwards, and terminate in blunt ends tipped with cartilage. In young subjects they are connected to the body of the bone by fibro-cartilage ; this in process of years becomes ossified. The lesser cornua (cerato-liyals) are connected, one on each side, to the point of junction between the body and the greater cornua, by means of a little joint lined with synovial membrane, which admits of free motion. They are of the size of a barleycorn, and give attachment to the stylo-hyoid ligaments. The os hyoides is connected with the thyroid cartilage by several ligaments, which contain a quantity of elastic tissue. There is: 1. The thyro-hyoid mem- brane, a broad fibrous membrane, which proceeds from the supe- rior border of the thyroid cartilage to the upper and posterior part of the hyoid bone. In front of this membrane there is a bursa, of which the use is to facilitate the play of the thyroid cartilage behind the os hyoides. The central portion is stronger than the lateral, and is called the anterior thyro-hyoid ligament. Through the lateral part of this membrane, the superior laryngeal nerve and artery enter the larynx. 2. The right and left lateral 240 THYROID CARTILAGE. thyro-hyoid ligaments extend between the extremities of the greater cornua of the os hyoides, and the ascending cornua of the thyroid cartilage. They contain a small nodule of cartilage (cartilayo triticea). CARTILAGES OF The framework of the larynx is composed of THE LABYNX. nine cartilages viz., the thyroid, the cricoid, the two arytenoid, the two cornicula laryngis, the two cuneiform cartilages, and the epiglottis. These are connected by joints and elastic ligaments, so that they can be moved upon each other by their respective muscles ; the object of this motion being to act upon two elastic ligaments, called the vocal cords, upon the vibra- tion of which phonation depends. THYROID CAB- This cartilage, so called because it shields the TILAGE. mechanism behind it, 1 consists of two lateral halves (cdce), united at an acute angle in front, which forms the prominence termed the pomum Adami. This prominence presents a notch at its upper part, to allow it to play behind the os hyoides in deglutition. There is a bursa in front of it. Each ala is some- what quadrilateral in form, and presents for examination two surfaces and four borders. The outer stirface of each ala is marked by an oblique line passing downwards and forwards from the base of the upper cornu, which gives attachment to the sterno-thyroid and thyro-hyoid muscles. The smooth surface behind the ridge gives attachment to the inferior constrictor. The inner surface is smooth, slightly concave, and is covered with mucous membrane. In the acute angle in front there are attached from above down- wards, the epiglottis, the false and true vocal cords, the thyro- arytenoidei and thyro-epiglottidei muscles. The inferior border is slightly arched in the middle, affording attachment to the crico- thyroid membrane, and on either side presents a convex promi- nence, which gives attachment to the crico-thyroid muscle and the crico-thyroid membrane. The superior border is nearly horizontal, and affords attachment to the thyro-hyoid membrane. The posterior border is thick, rounded and nearly vertical, and gives insertion to the stylo-pharyngeus and palato-pharyngeus muscles. This border terminates, above and below, in round projections called the upper 1 vpf6s, a shield. CEICOID CARTILAGE. 241 and lower cornua. The upper is the longer ; the lower articulates with the side of the cricoid cartilage. CEICOID CAB- This cartilage, named from its resemblance to TILAGE. a ring, 1 is situated below the thyroid. It is not of equal depth all round. It is narrow in front, where it may be felt about a quarter of an inch below the thyroid ; from this part, the upper border gradually rises, so that, posteriorly, the ring is an inch in vertical depth, and occupies part of the interval left between the alee of the thyroid. In the middle of this broad posterior surface is a vertical ridge, on either side of which observe a superficial excavation for the origin of the crico-arytenoidei postici : to the lower part of the vertical ridge are attached some of the longitudinal fibres of the oesophagus. On its upper part are two oval slightly convex surfaces for the articulation of the ary- tenoid cartilages, between which is a concavity for the attachment of the arytenoideus. In front, its upper border presents a broad excavation to which the crico-thyroid membrane (on which is seen the crico-thyroid artery), is attached. On its outer surface, external to the depression for the crico-arytenoideus posticus, is an elevated facet which articulates with the inferior cornu of the thyroid cartilage. In front of this articular surface it gives attachment to the inferior constrictor of the pharynx. The lower border is straight, and is connected by fibrous membrane to the first ring of the trachea. The inner surface is smooth, and the upper border is elliptical ; its lower being nearly circular. The thyroid cartilage is connected to the cricoid LIGAMENTS. , *, , ' . , ., T . by a membrane the cnco-tfiyroid. It consists of a median triangular portion, composed mainly of elastic tissue, with its base directed downwards. The lateral portions are thin and membranous, extending as far backwards as the articular facets for the thyroid cartilage, and are intimately connected with the inferior vocal cords. Between the inferior cornu of the thyroid cartilage and the cricoid there is a distinct joint, having a sy no vial membrane, and strengthened by a capsular ligament. The arti- culation allows of a movement revolving upon its own axis, and, consequently, permits the approximation of the two cartilages. 1 K/ji'/cos, a ring. 242 ARYTENOID CARTILAGES. ABYTENOID These cartilages are situated, one on each side, CARTILAGES. at the back of the upper border of the cricoid cartilage. In the recent state, before the membranes and muscles have been removed, the space between them resembles the lip of a pitcher l ; hence their name. Each is pyramidal, with the apex upwards, is about five or six lines in height, and three lines in diameter at its base, and presents for examination three surfaces (marked off by three borders), a base and an apex. The posterior surface of each is triangular and concave, and gives attachment to the arytenoideus muscle ; the anterior surface is irregular and convex, affording attachment to the thyro-arytenoideus, and to the superior or false vocal cord; the internal surface, the narrowest and nearly flat, faces the corresponding surface of the opposite cartilage, and is covered with mucous membrane. The base is broad, and presents a smooth somewhat concave triangular surface which articulates with the cricoid cartilage ; in front of the base is the pointed anterior angle, which gives attachment to the true vocal cord, and contributes to form part of the boundary of the rima glottidis ; at the outer and back part of the base is the external angle, into which certain muscles moving the cartilage are inserted, viz. the crico-arytenoideus posticus and crico-aryte- noideus lateralis. The base is articulated with the cricoid by a joint which has a loose capsular ligament and a synovial membrane, per- mitting motion in all directions, like the first joint of the thumb. The apex is truncated and points backwards and inwards. It is sur- mounted by a cartilaginous nodule, called the corniculum laryngis. CORNICULA. Are two small conical cartilaginous nodules, and LARYNGIS. continue the direction of the arytenoid cartilages upwards and inwards. CUNEIFORM These cartilages, sometimes called the cartilages ABTILAGES. of Wrisberg, are conical in form, and somewhat curved, with their broader part directed upwards and forwards. They are contained in the aryteno-epiglottidean fold. This piece of yellow fibro-cartilage is situated in the middle line, and projects over the larynx like a valve. It is like a leaf with its stalk directed downwards. Its , a pitcher. EPIGLOTTIS. 243 ordinary position is perpendicular, leaving the upper opening of the larynx free for respiration; but during the elevation of the larynx in deglutition it becomes horizontal, falls downwards and backwards over the larynx, and prevents the entrance of food into it. This descent of the epiglottis is accomplished, not by special muscular agency, but by the simultaneous elevation of the larynx and the retraction of the tongue. Its apex or lower part is at- tached by the tliyro-epiglottic ligament to the angle of the thyroid cartilage; it is also connected by an elastic ligament, hyo-epigloHic, to the posterior surface of the os hyoides. Laterally, its borders are rather turned backwards, and to them are attached two folds of mucous membrane, which pass to the arytenoid cartilages, called the aryteno-epiglottic folds. Its anterior surface is only free at its base, where it is connected with the base of the tongue by the three glosso-epiglottic folds. Its posterior or laryncjeal surface is smooth, concavo-convex and free, and looks towards the larynx. The surface of the epiglottis is closely invested by mucous membrane ; this being removed, the yellow cartilage of the epiglottis is seen pitted and often perforated by the small mucous glands. The cartilages of the larynx resemble those of the ribs in struc- ture. In the young they are dense and elastic, but some have a tendency to ossify with age. In very old subjects, the thyroid and cricoid cartilages are often completely ossified, and their interior presents an areolar tissue, containing oily matter, analogous to the spongy texture of the bones. The epiglottis, cornicula laryngis, and cuneiform cartilages are rarely ossified, on account of their consisting of yellow fibro-cartilage resembling that of the ear and nose. The larynx must now be examined in its perfect condition. Mucous MEM- The mucous membrane lines the whole of the in- BRANE OF THE terior of the larynx, being continuous above with LABYNX. tlaai, of the pharynx and mouth, below with that of the trachea. It is intimately adherent to the posterior part of the epiglottis and to the true vocal cords ; elsewhere it is loosely con- nected to the subjacent structures by an abundance of areolar tissue, which admits of its being elevated into large folds. This is R 2 244 MUCOUS MEMBRANE OF THE LARYNX. chiefly found about the upper opening of the larynx, and it deserve* notice from the rapidity with which it becomes the seat of serous effusion in acute inflammation of the larynx, and thus produces symptoms of suffocation. In the remaining part of the interior of the larynx the mucous membrane is moderately adherent to the subjacent tissues, and at the upper or false vocal cord it redupli- cates upon itself and then lines the sacculus laryngis. Naturally, the mucous membrane is of pale rose colour, except where it covers the cushion of the epiglottis, where it is bright pink. It is covered by columnar ciliated epithelium below the false vocal cords, and this variety is continued up the epiglottis as high as its middle ; above this, by squamous epithelium. From the root of the tongue to the anterior surface of the epiglottis, the membrane forms three folds, cjlosso-epiglottic, one median, and two lateral, containing elastic tissue. From the epiglottis, to which it is intimately ad- herent, it is continued backwards on either side to the apices of the arytenoid cartilages, forming the afnjteno-epiglottic folds which bound the upper entrance into the larynx. The mucous membrane of the larynx is remarkable for its acute sensibility. This is requisite to guard the upper opening of the larynx during the passage of the food over it. The larynx is closed during the act of deglutition ; but if, during this process, anyone attempt to speak or laugh, the epiglottis is raised, and allows the food to pass, as it is termed, the wrong way. As soon as the foreign body touches the mucous membrane of the larynx, a spasmodic fit of coughing expels it. The sub-mucous tissue of the larynx is studded with mucous: glands. An oblong mass of them lies in the aryteno-epiglottic fold, and they are particularly numerous about the ventricles of the larynx. The surface of the epiglottis towards the tongue is abundantly provided with them. Their ducts pass through the epiglottis, and may be recognised as minute openings on ita laryngeal aspect. SUPERIOR This is the opening through which the larynx OPENING OF THE communicates with the pharynx. Its outline ia LARYNX. triangular, with its base directed forwards, and it slopes from before backwards. Anteriorly it is bounded by tha FALSE AND TRUE VOCAL CORDS. 245 epiglottis, laterally by the aryteno-epiglottic folds and cuneiform cartilages, posteriorly by the arytenoid cartilages and the cornicula laryngis. The apex presents the funnel-shaped appearance from which the arytenoid cartilages derive their name. On looking down through this superior opening you see the cavity of the larynx, which is divided into an upper and a lower part by the narrow triangular fissure, called the glottis, or rima glottidis ; so that the upper part gradually narrows to this chink, while the lower part gradually widens, and becomes con- tinuous at the lower border of the cricoid cartilage with the trachea. The objects seen above the rima glottidis are, in the middle line, below the base of the epiglottis, a round elevation covered with mucous membrane of a bright pink colour, termed the cushion of the epiglottis ; on each side is an arched fold, the false vocal cords with their concavity looking downwards, and forming the upper boundary of a small recess, the ventricle of the larynx, leading into a pouch, called the sacculus laryngis ; below this, are the two white bands, the true vocal cords, which form the boundaries of the glottis. The larynx below the true vocal cords gradually enlarges, and presents nothing calling for special description. GLOTTIS, OK EIMA The rima glottidis is the triangular horizontal GLOTTIDIS. opening between the inferior or true vocal cords. Its apex is directed forwards, its base backwards. The anterior two-thirds of this opening is bounded by the true vocal cords, the posterior third by the arytenoid cartilages. The length in the male is eleven lines, its width at rest from three to four lines ; in the female its length is eight lines, its width two lines. Before the age of puberty these dimensions are much less. SUPERIOR OR These are the prominent crescentic folds of FALSE VOCAL mucous membrane which form the upper boun- CoKDS - daries of the ventricles and enclose within them thin ligamentous fibres, called the superior thyro-arytenoid ligaments. They are called the false vocal cords, because they have little or nothing to do with the production of the voice. They are com- posed of elastic tissue like the true vocal cords ; but they also contain fatty tissue, which the true ones do not. 24G THE GLOTTIS. INFERIOR OR TRUE VOCAL CORDS. FIG. 55. Thyroid cartilage. True vocal cord. Arytenoid cartilage. Elastic ligament. These two cords, called also the inferior thyro*. arytenoid ligaments, are composed of yellow elastic tissue, and extend horizontally from the angle of the thyroid cartilage to the anterior angles of the base of the arytenoid cartilages. Their inner or free edges are thin and sharp > and look upwards ; their outer borders are continuous with the crico-thyroid membrane, and are in contact with the thyro-*- arytenoidei muscles. They diverge as they pass backwards, and are covered with very thin and closely adherent mucous mem-, brane, having columnar ciliated epithelium. We shall presently see that, by the muscles which act upon the arytenoid cartilages, these cords can be approximated or separated from each other ; in other words, the rima glottidis can be closed or dilated. When suffi-. ciently tightened, and brought parallel by means of certain muscles, the cords are made to vibrate by the current of the expired air, and thus is produced the voice. In the adult male the true vocal cords measure about seven lines ; in the female, about five lines. In boys they are shorter ; hence their peculiar voice. At puberty, the cords lengthen, and the voice breaks. The glottis admits of being dilated, contracted, and even com- pletely closed, by its appropriate muscles. When at rest, its shape is triangular, as shown in fig. 55, where the arytenoid cartilages are cut through on a level with the vocal cords. During every inspiration, the glottis is dilated by the crico-arytenoidei postici ; it then becomes pear-shaped (fig. 57). During expiration, it re- sumes its triangular shape : and this return to a state of rest ia effected, not by muscular agency, but by two elastic ligaments, shown in fig. 55, which draw the arytenoid cartilages together. Thus then the glottis, like the chest, is dilated by muscular tissue ; like the chest, also, it is contracted by elastic tissue. In speaking SHAPE OF THE GLOTTIS WHEN AT REST. INTRINSIC MUSCLES OF THE LARYNX. 247 or singing, the glottis assumes what is called the vocalising posi- tion that is, the opening becomes narrower, and its edges nearly parallel. VENTRICLES OP These are the recesses between the upper and THE LARYNX. lower vocal cords, and each leads to a small conical pouch, the sacculus laryngis. Each ascends for about half an inch, as high as the upper border of the thyroid cartilage, which bounds it on its outer side, while on the inner side is the upper vocal cord. It contains from sixty to seventy muciparous glands. Over its inner and upper part is a layer of muscular tissue, compressor sacculi larynyis of Hilton (aryteno-epiglottideus inferior), which connects it with the aryteno-epiglottic fold ; on its outer side is the upper part of the thyro-arytenoideus. INTRINSIC There are eleven muscles which act upon the MUSCLES OF THE larynx : five on each side and one in the mid- LARYNX. ^j e< ip^e g ve p a j rs are the crico-thyroidei, the crico-arytenoidei postici, the crico-arytenoidei laterales, the thyro- arytenoidei, and the aryteno-epiglottidei. The single one is the arytenoideus. FIG. 56. Arytenoid cartilage . . Crico-arytenoid joint . Crico-thyroid joint . . Thyroid cartilage. True vocal cord. Cricoid cartilage raised. Cricoid cartilage. DIAGRAM SHOWING THE ACTION OF THE CRICO-THYROID MUSCLE. M. CRICO- This muscle is situated on the front of the THYROIDEUS. larynx. It arises from the front and side of the 248 INTRINSIC MUSCLES OF THE LARYNX. cricoid cartilage, ascends obliquely outwards, and is inserted into the inferior border and lower cornu of the thyroid. Its action is to tighten the vocal cords. It does this by raising the anterior part of the cricoid cartilage : since this cartilage cannot be raised without lengthening these cords, as shown by the dotted line, fig. 56. Its nerve is the external laryngeal branch of the superior laryngeal. Between the anterior borders of the two muscles is seen the crico-thyroid membrane, which is divided in laryngotomy. M. CKICO- This muscle arises from the broad depression on the posterior part of the cricoid cartilage ; its fibres converge, and pass outwards and upwards, FIG. 57. ARYTENOIDEUS POSTICUS. Vocal cord . . . Thyroid cartilage Cricoid cartilage . Arytenoid cartilage . Elastic ligament (crico-arytenoid) . Thyro-arytenoideus. Crico-arytenoideus lateralis. Ideal pivot. Crico-arvteiioideus posticus. GLOTTIS DILATED : MUSCLES DILATING IT KEPEESENTED WAVY. to be inserted into the outer angle of the base of the arytenoid. Its action is to dilate the glottis. It does this by drawing the posterior tubercle of the arytenoid cartilage toivards the mesial line, and therefore the anterior angle (to which the vocal cord is attached) from the mesial line (fig. 57). In. this movement the arytenoid cartilage rotates as upon a pivot, and acts as a lever of the first order; the fulcrum or ideal pivot being interme- diate between the power and the weight. This muscle dilates the glottis at each inspiration. Its nerve comes from the inferior laryngeal. 1 1 A slip called the ' kerato-cricoid ' is occasionally present. It is a short INTRINSIC MUSCLES OF THE LARYNX. 249 M. ABYTE- NOIDETJS. This single muscle is situated immediately at the back of the arytenoid cartilages. The fibres pass across from one cartilage to the other running in a transverse direction. Action. By approximating the arytenoid cartilages, they assist in contracting the glottis. It is supplied by the inferior laryngeal nerve. M. ARYTENO- This muscle EPIGLOTTIDEUS. cvrises from the inferior and outer angle of the arytenoid cartilage, and, crossing its fellow like the letter X, is inserted, partly into the apex of the opposite arytenoid cartilage, and partly into the aryteno- epiglottic fold. T expose this reflect crico-thyroid muscle, the crico-thyroid mem- brane, and then cut away the ala of the thyroid cartilage. It arises from the upper border of the side of the cricoid cartilage, and the fibres, passing backwards and up- wards, converge to be inserted into the external angle of the base of the arytenoid, in front of the crico- arytenoideus posticus. Action. By drawing the arytenoid carti- lages inwards, the muscles of opposite sides contract the glottis (fig. 59). Its nerve comes from the inferior laryngeal. M. CRICO- ARYTENOIDEUS LATERALIS. SIDE VIEW OF THE MUSCLES OF THE LARYNX. 1. Thyro-epiglottideus. 2. Thyro-arytenoideus, upper and lower portions. 3. Crico-arytenoideus lateralis. 4. Crico-arytenoideus postieus. 5. Arytenoideus. fasciculus passing from the cricoid to be inserted ' into the inferior cornu of the thyroid cartilage. It is in connection with the crico-arytenoideus posticus, and is usually found on one side only, being present in about one in five subjects. (Merkel, Anat. und Phys.des mensch. Stimme-und Sprach-Organs, 1857 ; Turner, Month. Med. Journ., Feb. 1860). 250 INTRINSIC MUSCLES OF THE LARYNX. M. THYRO- ARYTENOIDEUS. This muscle arises from the side of the angle of the thyroid cartilage and the crico-thyroid mem- brane, runs horizontally backwards, and is inserted into the base and anterior surface of the arytenoid. Its fibres run parallel with FIG. 59. Vocal cord Aryteuoid cartilage Elastic ligament . Thyro-arytenoideus.. Crico-arytenoideus lateralis. Crico-arytenoideus. posticus. GLOTTIS CLOSED : MUSCLES CLOSING IT REPRESENTED WAVY. the true vocal cord, and some of them are directly inserted into it. It consists of two fasciculi an upper and a lower. The lower and larger portion is inserted into the anterior angle and the anterior surface of the arytenoid ; the upper is inserted into the upper part of the anterior surface and the anterior border of the arytenoid. Its nerve comes from the inferior laryngeal. This muscle relaxes the vocal cord. More than this, it puts, the lip of the glottis in the vocalising position ; in this position the margins of the glottis are parallel, and the chink is reduced to the breadth of a shilling. The following table shows the action of the several muscles, which act upon the glottis : Crico-thyroidei . . Thyro-arytenoidei Crico-arytenoidei postici Stretch the vocal cords. Relax the vocal cords, and place them in the vocalising position. Dilate the glottis. VESSELS AND NERVES OF THE LARYNX. 251 Crico-arytenoidei laterales . Draw together the arytenoid \ cartilages r c * e Arytenoideus . . . Ditto ditto ditto j Aryteno-epiglottidei . . Contract the upper opening of the larynx. The epiglottis is connected by muscles with the arytenoid and thyroid cartilages : they are the thyro-epiglottideus, the aryteno- epiglottideus superior and inferior. The thyro-epiglottideus is a thin muscle, arising from the angle of the thyroid cartilage just above the thyro-arytenoideus, and is inserted by diverging fibres into the border of the epiglottis and into the aryteno-epiglottic fold. The aryteno-epiglottideus superior passes as thin muscular fibres from the tip of the arytenoid cartilage to the mucous membrane attached to the side of the epiglottis. The aryteno-epiglottideus inferior, separated from the preceding by a distant interval, arises from the anterior surface of the ary- tenoid cartilage, and is inserted into the upper and inner part of the epiglottis. This muscle is also called the compressor saceuli laryngis of Hilton. 1 The Mood-vessels of the larynx are derived from the superior and inferior thyroid arteries. The laryngeal branch of the superior thyroid passes through the thyro-hyoid membrane with the corresponding nerve, and divides into branches, which supply the muscles and the mucous membrane. The laryngeal branches of the inferior thyroid ascend behind the cricoid cartilage. A constant little artery passes through the crico-thyroid membrane. The nerves of the larynx are the superior and inferior (recurrent) laryngeal branches of the pneumogastric. The superior laryngeal, having passed through the thyro-hyoid membrane, divides into branches, distributed to the mucous mem- brane of the larynx. Its filaments spread out in various directions : some to the anterior and posterior surfaces of the epiglottis, and to the aryteno-epiglottidean folds, others to the interior of the larynx and the vocal cords. A constant filament descends behind the ala 1 The triticeo-glossus is a small muscle frequently present : it arises from the cartilage triticea, and passing forwards and upwards joins the cerato-glossus to be inserted into the tongue. 252 DIFFERENCES BETWEEN THE MALE AND FEMALE LARYNX. of the thyroid cartilage, and communicates with the inferior laryn- geal, and another communication with the same nerve is found behind the larynx beneath the pharyngeal mucous membrane. Its external laryngeal branch supplies the crico-thyroid muscle. The inferior (or recurrent} larynyeal nerve enters the larynx be- neath the inferior constrictor, and ascends behind the joint between the thyroid and cricoid cartilages. It supplies all the intrinsic muscles of the larynx except the crico-thyroid. If the recurrent nerve be divided, or in any way injured, the muscles moving the glottis become paralysed, but its sensibility remains unimpaired. When the nerve is compressed by a tumour for instance, an aneurism of the arch of the aorta the voice is changed to a whisper, 1 or even lost. DIFFEEENCE Until the approach of puberty, there is no great BETWEEN THE MALE difference in the relative size of the male and AND THE FEMALE female larynx. The larynx of the male, within AKYNX ' two years after this time, becomes nearly doubled in size ; that of the female grows, but to a less extent. The larynx of the adult male is in all proportions about one third larger than that of the adult female. The alee of the thyroid cartilage form a more acute angle in the male ; hence the greater projection of the pomum Adami and the greater length of the vocal cords in the male. ( Male 7 lines The average length of the vocal cords is in the J (Female .5 ,, (Mnlp 11 The average length of the glottis is in the . J (Female .8 ,, The size of the larynx does not necessarily follow the propor- tions of the general stature ; it may be as large in a little person as in a tall one : this corresponds with what we know of the voice. 1 Medical Gazette, Dec. 1843. THE TONGUE. 253 DISSECTION OF THE TONGUE. The tongue is a complex muscular organ, subservient to taste, speech, suction, mastication, and deglutition. It is situated in the space formed by the lower dental arch ; its upper surface is convex and free, as is also its anterior part or tip, which lies behind the lower incisor teeth ; its posterior and inferior part is connected to the os hyoides by the hyo-glossi, to the styloid process of the tem- poral bone by the stylo-glossi, and to the symphysis of the lower jaw by the genio-hyo-glossi muscles. The upper surface or dorsum is convex, and slopes on all sides from the centre ; it is divided into two symmetrical halves by a median groove rapJie running along the middle, and terminates posteriorly in a depression the foramen ccecum into which open several mucous glands. The posterior third of the dorsum is com- paratively smooth : the anterior two-thirds is rough, and covered with small eminences called papillce. Mucous MEM- The surface of the tongue is covered with mu- BRANE. cous membrane, which is composed of structures similar to those of the skin generally that is to say, it consists of a cutis vera with numerous elevations called papillae, and of a thick layer of squamous epithelium. The cutis is much thinner than that of the skin of the body, and affords insertion to some muscular fibres of the tongue. The mucous membrane on the under aspect of the tongue is smooth and comparatively thin, and, in the middle line in front, forms a fold the frcenum linguce which connects it to the mucous membrane of the floor of the mouth. On each side of the fraenum are the elevated orifices of the submaxillary ducts ; and further back, in the furrow between the tongue and gums, are the openings of the sublingual ducts. Laterally, the mucous membrane is re- flected from the under part of the tongue to the lower jaw, and forms the floor of the mouth. From the posterior part of the tongue the mucous membrane passes to the soft palate on each side, forming the folds termed the 254 THE TONGUE. FIG. 60. anterior palatine arches, which enclose the palato-glossi ; there are also three folds to the epiglottis, termed the glosso-epiglottic : two lateral and one median, the latter enclosing a layer of elastic tissue called the glosso-epiglottic ligament. This ligament raises the epiglottis when the tongue is protruded from the mouth ; hence the rule of never pulling the tongue forwards when passing^ a tube into the oesophagus, otherwise the tube might pass into the larynx. PAPILLA OF The anterior two-thirds of the tongue is studded THE TONGUE. with numerous small eminences called papillae, : these, according to their size and form, are distinguished into three kinds viz. papil- lae circumvallatce, papillce fungiformes, and papillce filiformes (fig. 60). The papillce circumvallatce vary in number from eight to twelve, and are arranged at the back of the tongue in two rows, which converge like the branches of the letter V, with the apex backwards, towards the for- amen caecum. Each of these papillae is circular, from the -^th to -^In. ^ an i ncn wide, and slightly broader above than below. Each is surrounded by a circular fossa, which itself is bounded by an elevated ring (vallum') . The papillae are covered with a thick stratum of scaly epithelium, beneath which are numerous secondary papillae. Buried in the epithelium surrounding the sides (but not on the upper surface) of these papillae, numerous flask-shaped bodies, called the taste-buds, have been discovered. Their bases rest upon the corium, and their apices open upon the surface. Each consists of a cortical and a medullary portion : the cortical is made up of one or more layers of long flattened cells ; the central consists of numerous spindle-shaped cells, whose free extremity projects from the orifice of the taste-bud, while the deeper extremity rests in the corium, and is in close connection. UPPEK SURFACE OF THE TONGUE, WITH THE FAUCES AND TONSILS. 1. Papillae circumvallatse. 2. Papillae f ungiformes. PAPILLAE OF THE TONGUE. 255 with a fine plexus of nerve-filaments derived from the glosso- pharyngeal nerve. 1 The papillce fungifarmes, smaller and more numerous than the circumvallatce, are scattered chiefly over the sides and tip of the tongue, and sparingly over its upper surface. They vary in shape, some being cylindrical, others having rounded heads like mush- rooms : whence their name. Near the apex of the tongue they may be distinguished during life from the other papillae by their redder colour. In scarlatina, and some exanthematous fevers, these papillae become elongated, and of a bright red colour ; as the fever subsides, their points acquire a brownish tint, giving rise to what is called the strawberry tongue. The papillce filiformes (conicce) are the smallest and most numerous. They are so closely aggregated that they give the tongue a velvet-like appearance. Their points are directed back- wards, so that the tongue feels smooth if the finger be passed over it from apex to base, but rough if in the contrary direction. These papillae consist of small conical processes arranged for the most part in a series of lines running parallel to the two rows of the papillae circumvallatas. Each papilla is covered with a thick layer of epithelium, which is prolonged into a number of free hair-like processes. If the papillae be injected, and examined under the microscope, it is found that they are not simple elevations, like those of the skin, but that from them arise secondary papillae. The papillae circumvallatae consist of an aggregation of smaller papillae arranged parallel to each other ; and the papillae fungiformes consist of cen- tral stems from which minute secondary papillae shoot off. This elaborate structure escapes observation because it is buried beneath the epithelium. 2 Each secondary papilla receives a blood-vessel, which passes nearly to its apex, and returns in a loop-like manner. The papillae are covered with one or more layers of squamous epithelium. That which covers the filiform is superimposed so 1 For further information about these bodies the student is referred to Engelmann in Strieker's Handbook. He states that each taste-bud consists of from fifteen to thirty cells. * See Bowman and Todd's Physiological Anatomy. 256 GLANDS BENEATH THE TONGUE. thickly as to give it sometimes the appearance of a brush when seen under the microscope. The various kinds of fur on the tongue consist of thick and sodden epithelium. Respecting the use of the papillse, it is probable that they enable the tongue to detect impressions with greater delicacy. From the density and arrangement of their epithelial coat, the filiform papillas give the surface of the tongue a roughness, which is useful in its action upon the food. An apparatus of this kind, proportionately stronger and more developed, makes the tongue of ruminant animals an instrument by which they lay hold of their food. In the feline tribe e.g. the lion and tiger these papillae are so sharp and strong that they act like rasps, and enable the animal to lick the periosteum from the bones by a single stroke of his tongue. In some mammalia, they act like combs for cleaning the skin and the hair. Numerous small racemose and acino-tubular glands, lingual glands, are found in the sub- mucous tissue at the root of the tongue. They are similar in structure and secretion to the tonsillar and palatine glands, so that there is a complete ring of glands round the isthmus faucium. Small round orifices upon their surface indicate the termination of their ducts. Other mucous glands, with ducts from one quarter to half an inch long, are situated in the muscular substance of the tongue. LYMPHOID A considerable amount of lymphoid tissue is TISSUE. situated at the back of the tongue, which in some parts is collected into definite masses called follicles. Small de- pressions also occur in this situation, whose walls are studded with lymphoid tissue, and into which some of the mucous glands open. On the under surface of the apex of the tongue GLANDS BE- NEATH THE is placed, on either side, a group of glands pre- APEX OF THE sumed to be salivary. Considering each group as TONGUE. one gigjy^ observe that it is oblong, with the long diameter from seven to ten lines, parallel with the axis of the tongue. It lies near the mesial line, a little below the ranine artery, on the outer side of the branches of the gustatory nerve, under some of the fibres of the stylo-glossus. Four or five ducts INTRINSIC MUSCLES OF THE TONGUE. 257 proceed from each group, and terminate by separate orifices on the under surface of the tongue. MUSCULAR The substance of the tongue is composed of FIBBKS OF THE muscular fibres and of a small quantity of fat. The TONGUE. extrinsic muscles of the tongue have been described in the dissection of the submaxillary region (p. 102). We have now to examine its intrinsic muscles. For this purpose the mucous membrane must be removed from the dorsum of the tongue. On dissection it will be found that the great bulk of the organ consists of fibres which proceed in a longitudinal direction, constituting the linguales muscles. The superficial lingualis runs longitudinally beneath the mucous membrane of the dorsum ; its fibres are attached posteriorly to the hyoid bone and run forwards to the front and margin of the tongue. Posteriorly the muscle is thin and is covered by the fibres of the palato-glossus and hyo-glossus. The inferior lingualis is larger than the preceding, and is situated on the under aspect of the tongue between the genio-hyo- glossus and the hyo-glossus. It may be readily exposed by dis- secting the under surface of the tongue immediately on the outer aspect of the genio-hyo-glossus. It arises posteriorly from the hyoid bone and the substance of the tongue, and its fibres pass forwards to the tip of the tongue after being reinforced by fibres from the stylo-glossus. On its under aspect it is in relation with the ranine artery. The transverse fibres form a considerable part of the thickness of the tongue and arise from the fibrous septum. They pass out- wards between the superficial and inferior linguales, ascending as they near the sides of the tongue, where the fibres become con- tinuous with those of the palato-glossus. A considerable amount of fat is found among these fibres. The vertical fibres run in a curved direction, descending from the dorsum to the under aspect of the tongue, with the concavity outwards. They interlace with the transverse fibres and with the genio-hyo-glossus. On tracing the genio-hyo-glossi into the tongue, we find that some of their fibres ascend directly to the surface ; others cross in s 258 DISSECTION OF THE SUPERIOR MAXILLARY NERVE. the middle line, intersect the longitudinal fibres, and finally termi- nate upon the sides of the tongue. Lastly, the fibres of the stylo- glossi should be traced along the side of the tongue to the apex. FIBBOXJS SEPTUM The fibrous septum of the tongue is a vertical OF THE TONGUE. plane of fibrous tissue which extends, in the mesial line, from the base to the apex. It is thick posteriorly, where it is connected behind with the hyoid bone, and is lost in front between the muscles. In it is sometimes found a piece of fibro-cartilage, called nucleus fibrosus linguce, a representative of the lingual bone in some of the lower animals. The arteries supplying the tongue are the dorsal and ranine branches of the lingual artery. It is important to bear in mind that the arteries do not anastomose across the middle line, and only very slightly at the apex, so that it is possible to cut along the septum of the tongue from the apex to the base with very little haemorrhage, a fact of much importance in the removal of the tongue or cancer of that organ. The nerves to the tongue should now be followed to their ter- mination. The hypoglossal supplies with motor power all the muscles. The gustatory or lingual branch of the inferior division of the fifth is distributed to the mucous membrane and papillae of the apex and sides of the tongue, supplying the anterior two-thirds with common sensation. Upon this nerve depends the sensation of all ordinary impressions, such as that of hardness, softness, heat, cold, and the like. The glosso-pharyngeal nerve supplies the mucous membrane at the back and the sides of the tongue, and the papillae circum- vallatae. Under the microscope small ganglia may be distin- guished on the terminal fibres of this nerve. DISSECTION OF THE SUPERIOR MAXILLARY NERVE. To trace this nerve and its branches we must remove the outer wall of the orbit as far as the foramen rotundum, so as to expose the spheno-maxillary fossa. The superior maxillary nerve is a sensory nerve, and is the SUPERIOR MAXILLARY NERVE. 259 second division of the fifth cranial nerve. Proceeding from the Gasserian ganglion (fig. 61), it leaves the skull through the fora- men rotundum, and passes horizontally forwards across the spheno- maxillary fossa. It then passes into the orbit through the spheno- FIG. 61. Trunk of the fifth nerve . Qasserian ) ganglion . | Facial n 'Chorda tym- pani . . Submaxillary ganglion . Frontal, lachry- mal and na-Ki! nn. Orbital branch. Infra-orbital n. Anterior dental n. Xaso-palatine n. Palatine n. Gustatory n. DIAGBAM OF THE SUPERIOR MAXILLARY NERVE. 1. Spheno-palatine ganglion. 2. Otic ganglion. maxillary fissure, enters the infra-orbital canal with the corre- sponding artery, and finally emerges upon the face, through the infra-orbital foramen, beneath the levator labii superioris, where it divides into a number of spreading branches, distributed to the lower eyelid, the nose and the upper lip. The branches given off are : 1. Within the skull. a. A recurrent branch, to the dura mater and the middle meningeal artery, is given off near the Gasserian ganglion. 2. In the spheno-maxillary fossa. b. The orbital branch already described (p. 63). c. Two spheno-palatine branches which descend to the spheno-pala- "tine ganglion (Meckel's), situated in the spheno-maxillary fossa (fig. 61). d. The dental branches are three in number : the two posterior are s 2 2GO SPHENO-PALATINE GANGLION. given off immediately before the nerve enters the infra-orbital canal, and descend along the tuberosity of the superior maxillary bone ; the- anterior is given off in the infra-orbital canal. The posterior branch divides into two branches, which send small filaments to the gums and the mucous membrane of cheek, and then run in bony canals in company with small arteries to supply the molar teeth and the antrum ; the middle branch passes down in a special canal in front of the antrum to be distributed to the bicuspid teeth ; the anterior branch, the largest, is given off before the nerve emerges from the infra-orbital foramen, and enters the canal in the front wall of the antrum ; it divides into dental branches for the supply of the canine and incisor teeth, and into a nasal branch for the mucous membrane of the floor of the nasal fossa. The anterior branch while in its bony canal gives off some filaments, which join with the posterior dental branches, and above the canine fossa it also forms a communication with a nasal branch from the spheno-palatine ganglion, to form the ganylion of Boclidalek. e. The terminal branch of the superior maxillary nerve is called the infra-orbital, which divides on the face into palpebral, nasal, and labial branches. These have been already dissected and described (p. 48). At this stage the student should make the dis- section to expose the spheno-palatine ganglion and its branches. To do this, it is necessary to saw through the skull rather on one side of its middle line, so as to expose the cavity of the nose. Search must now be made for the spheno-palatine foramen (just external to which is the spheno-palatine ganglion), which is situated immediately above the posterior extremity of the middle turbinated bone. Remove the mucous membrane at this point, when the terminal branch of the internal maxillary artery, which comes through this foramen into the nose, may be readily made out. The student should next cut away the thin plate of bone which forms the inner boundary of the posterior palatine canal. Then, by tracing upwards the branches contained within the canal, he will find the ganglion. SPHENO-PALA- This ganglion is called, after its discoverer, TINE GANGLION. Meckel's ganglion. It is the largest of the ganglia in connection with the branches of the fifth cerebral nerve, is tri-* angular, convex on its outer surface, of reddish-grey colour, about one-fifth of an inch in diameter, and is placed immediately below SFHENO-rALATINE GANGLION. 261 the superior maxillary nerve, as it crosses the spheno-maxillary fossa. Like other ganglia, it has three roots a sensory, from the superior maxillary ; a motor, from the great petrosal branch of the facial ; and a sympathetic, from the carotid plexus. FIG. 62. 15 DEEP VIEW 01' THE SPHENO-PALATINE GANGLION, AND ITS CONNECTION WITH OTHER NEEVES. (After Hirschfeld.) 1. Superior maxillary n. 2. Spheno-palatine ganglion, from the lower part of which are seen proceeding the palatine nerves. 3. Posterior superior dental brs. 4. Sixth n. receiving two filaments from the carotid plexus of the sympathetic n. 6. The carotid br. of the Vidian. 6. The great petrosal br. of the Vidian. 7. Lesser petrosal nerve. 8. External deep petrosal n., uniting with lesser petrosal n. 9. The internal deep petrosal nerve joining the great petrosal nerve. 10. Filament to fenestra ovalis. 11. Filament to Eustachian tube. 12. Filament to fenestra rotunda. 13. Chorda tympani. 14. Infra-orbital nerve. 15. Anterior dental n. 16. Junction of posterior and anterior dental filaments. 17. Grlosso-pharyngeal n. giving off tymj anic branch. Its branches pass upiuards to the orbit, downwards to the palate, inivards to the nose, and backivards to the pharynx, as follows : a. Ascending branches. These are very small, and run through the spheno-maxillary fissure to be distributed to the periosteum of the orbit. 1 1 Anatomists describe several branches ascending from the ganglion : one to join the sixth nerve (Bock); another to join the ophthalmic ganglion (Tiedemann); and, lastly, some to join the optic nerve through the ciliary branches (Hirzel). 262 SPHENO-PALATINE GANGLION. b. Descending branches. To see these the mucous membrane must be removed from the back part of the nose : we shall then be able to trace the nerves through their bony canals. Their course is indicated by their accompanying arteries. They descend through the palatine canals, and are three in number. The anterior palatine nerve, the largest, descends through the posterior palatine canal to the roof of the mouth, and then divides into branches, which run in grooves in the hard palate nearly to the gums of the incisor teeth, where it communi- cates with the naso-palatine nerve. Within its canal it sends two inferior nasal branches which enter the nose through foramina in the palate bone to supply the membrane on the middle and lower spongy bones. The posterior or smaller palatine descends in the same canal with the anterior, or in a smaller one of its own, and supplies the mucous membrane of the soft palate, the tonsil, and (according to Meckel) the levator palati muscle. 1 The external palatine may be traced in a special canal down to the soft palate, where it terminates in branches to the uvula, the palate, and tonsil. The two last branches communicate with the tonsillar filaments of the glosso-pharyngeal to form the tonsillar plexus of nerves. c. Internal branches. These, three or four in number, pass through the spheno-palatine foramen to the mucous membrane of the nose. To see them clearly, the parts should have been steeped in dilute nitric acid ; afterwards, when well washed, these minute filaments may be recognised beneath the mucous membrane covering the spongy bones. The upper nasal branches, four or five in number, pass inwards, and are distributed on the two upper spongy bones, the upper and back part of the septum and the posterior ethmoidal cells. The naso-palatine (nerve of Cotunnius), traverses the roof of the nose, distributes branches to the back part of the septum narium, and then proceeds obliquely forwards, along the septum, to the foramen incisivum, through which it passes, and finally terminates in the palate behind the incisor teeth, communi- cating here with the anterior palatine nerve. d. Posterior branches. The pharyngeal nerve (ptery go-palatine), very small, comes off from the back of the ganglion, and, after passing 1 According to Longet (Anat. et Physiol. dzt Systeme Nerveux, Paris, 1842),. the posterior palatine nerve supplies the levator palati and the azygos uvulas with motor power. In this view of the subject the nerve is considered to be the con- tinuation or terminal branch of the motor root of the ganglion : that, namely, derived from the facial. This opinion is supported by cases in which the uvula is stated to have been drawn on one side in consequence of paralysis of the oppo-. site facial nerve. OTIC GANGLION. 263 through the pterygo-palatine canal with its corresponding artery, .sup- plies the mucous membrane of the back of the pharynx and the Eusta- chian tube. The Vidian nerve is the principal branch. It proceeds backwards from the posterior part of the ganglion, through the Vidian canal, where it distributes small branches to the back part of the roof of the nose and septum. It then traverses the fibro-cartilage of the foramen lacerum medium, and divides into two branches. Of these two branches, one, the larger the carotid joins the sympathetic plexus on the outer side of the internal carotid artery ; the other, the great petrosal, enters the cranium, and runs beneath the Gasserian ganglion and the dura mater in a small groove on the anterior surface of the petrous bone : it then enters the hiatus Fallopii, and joins the facial nerve in the aquseductus Fallopii. It would seem to be more in accordance with modern views to regard the Vidian nerve, not as dividing to form the carotid and great super- ficial petrosal branches, but rather as formed by the junction of these branches. In this view, the Vidian runs, not from, but to, the spheiio- palatine ganglion. The otic ganglion (Arnold's *) is situated on the OTIC GANGLION. . ., ,, , . ,, . .,, ,. . . _ inner side ot the interior maxillary division 01 the fifth nerve, immediately below its exit through the foramen ovale (fig. 62). It is oval, of reddish-grey colour, and always small. Its inner surface is in contact with the circumflexus palati muscle and the cartilage of the Eustachian tube ; behind it, is the middle menin- geal artery ; externally, it is in relation with the inferior maxillary nerve, where the motor root joins the sensory root. This ganglion has branches of connection with other nerves ; namely, a sensory from the auriculo-temporal nerve ; a motor from the branch of the inferior maxillary, which goes to the internal pterygoid muscle ; and a sympathetic from the plexus around the arteria meningea media. It communicates also with the facial and the glosso-pharyngeal nerves by the lesser petrosal nerve. This branch passes backwards, either through the foramen ovale or the foramen spinosum, or through a small hole between them, and runs beneath the dura mater in a minute groove on the petrous bone, external to that for the great petrosal nerve. Here it divides into two filaments, one of which joins the facial nerve in the aquseductus 1 J. Arnold, Diss. Inaug. Med., &c. Heidelbergas, 1826. 264 DIAGRAM OF NERVE-COMMUNICATIONS. Fallopii ; the other joins the tympanic branch of the glossc-pharyn- geal. These nerves are difficult to trace, not only on account of FIG. 63. N. to great petrosal . . N. to lesser petrosal . . N. to Eustachian tube . Ns. to carotid plexus . Chorda tympani . . . N. to stylo-hyoid . . N. to (ligastricus . . Petrous ganglion . . Carotid plexus . . . Branch to pharyngeal plexus Lingual branch . . . Ganglion of the trunk . Pharyngeal n. . Superior laryugeal Gangliform enlarge- ment. N. to fenestra ovalis. N. to fenestra ro- tunda. Tympanic n. Auricular n. Glosso-pharyngoal n. Jugular ganglion of do. Pneumogastric. Ganglion of root. Spinal accessory. Hypoglossal. Supr. cervical gan- glion. 1st cervical n. Br. to ganglion of trunk. 2nd cervical n. DIAGRAM OF THE COMMUNICATIONS OF THE FACIAL, GLOSSO-PHARYNGEAL, PNEUMO- GASTRIC, SPINAL ACCESSORY, HYPOGLOSSAL, SYMPATHETIC, AND THE TWO UPPEU CERVICAL NERVES. 1. Great petrosal nerve. 2. Lesser do. 3. External do. 4. Nerve to stapedins muscle. 5. Spheno-palatine ganglion. 6. Otic ganglion. their minuteness, but because they frequently run in canals in the temporal bone. NERVES AT BASE OF THE SKULL. 265 The otic ganglion sends a branch forwards to the tensor palati, and one backwards to the tensor tympani, on the outer side of the Eustachian tube. DISSECTION OF THE NINTH, TENTH, AND ELEVENTH CEANIAL NEEVES AT THE BASE OP THE SKULL. In this dissection we propose to examine the glosso-pharyngeal, pneumogastric, and spinal accessory nerves in the jugular fossa, and the ganglia and nerves belonging to them in this part of their course. These are difficult to trace, and cannot be followed unless the nerves have been previously hardened by spirit, and the bones softened in acid. The next thing to be done is to remove the outer wall of the jugular fossa. GLOSSO-PHA- This nerve emerges from the cranium through a EYNGEAL NEEVE. separate tube of dura mater, in front of that for the tenth and eleventh cranial nerves. Looking at it from the interior of the skull, we notice that it is situated in front, and rather to the inner side of the jugular fossa, where it lies in a groove. In its passage through the foramen, the nerve presents two enlargements, termed the jugular and the petrous ganglia. The jugular ganglion * is found upon the nerve immediately after its entrance into the canal of the dura mater, and averages about the ^th of an inch in length and breadth. It is situated on the outer side of the nerve, and does not implicate all its fibres. According to our observation, this ganglion is not infrequently absent (fig. 63). The petrous ganglion 2 is lodged in a groove in the lower part of the jugular fossa. It is oval, about a quarter of an inch long, and involves all the filaments of the nerve. From it are given off branches of communication with other nerves and the tympanic nerve 3 (fig. 63). 1 Muller, Medicin. Zeitung, Berlin, 1833. No. 52. 2 Andersch, Fragm. Descript. Nerv. Cardiac. 1791. 3 This nerve, though commonly called Jacobson's, was fully described by Andersch. 266 TYMPANIC BRANCH OF THE GLOSSO-PHARYNGEAL. The communicating brandies which connect this ganglion with the pneumogastric are, one to its auricular branch, and a second to- the ganglion of the root. It is also connected with the sympathetic by a small filament from the superior cervical ganglion. Another communicating branch pierces the posterior belly of the digastricus to join the facial just external to the stylo-mastoid foramen. The tympanic nerve ( Jacobson's) ascends, through a minute canal in the bony ridge which separates the carotid from the jugular fossa, to the inner wall of the tympanum, grooving the surface of the promontory, where it terminates in -six filaments. Of these three are branches of distribution, and three of communication with other nerves. The branches of distribution are, one each to the fenestra rotunda and the fenestra ovalis, which pass backwards, and one to the Eustachian tube, which is directed forwards. The branches of communication are four small filaments ; one or two tra- verse a bony canal in the anterior wall of the tympanum, and arch- ing forwards, join the plexus on the outer side of the carotid artery ; another, the small deep petrosal nerve, runs in a canal in the pro- cessus cochleariformis, passes through the foramen lacerum medium to join the carotid plexus ; a third ascends in front of the fenestra ovalis, and, passing forwards, joins the great petrosal nerve in the hiatus Fallopii ; the fourth leaves the front of the tympanum, under the name of the small superficial petrosal nerve, through a canal, where it is joined by a filament from the geniculate ganglion of the facial nerve; then passing beneath the canal for the tensor tympani, it emerges through a foramen on the anterior surface of the pars petrosa, external to the hiatus Fallopii ; it proceeds along the anterior surface of pars petrosa, and emerges from the skull between the great wing of the sphenoid and the petrous bones to join the otic ganglion. Thus the tympanic branch is distributed to the mucous membrane of the tympanum and the Eustachian tube, and communicates with the spheno-palatine ganglion through the great petrosal nerve, and with the otic ganglion through the lesser petrosal (fig. 62). PNEUMOGASTRIC This nerve leaves the cranium with the nervus NEBVE. accessorius through a common canal in the dura mater, behind that for the glosso-pharyngeal. At its entrance into PNEUMOGASTRIC NERVE. 267 the canal, it is composed of a number of separate filaments, which are soon collected into a single trunk. In the jugular foramen, the nerve presents a ganglionic enlargement, called the ganglion of the root and after the nerve has emerged from the jugular foramen, it presents a second ganglion the ganglion of the trunk of the nerve where it is joined by the accessory portion of the spinal accessory nerve. 1 The ganglion of the root is about ^th of an inch in length. It is connected by filaments with the sympathetic through the superior cervical ganglion, with the petrous ganglion of the glosso- pharyngeal, with the auricular branch of the facial, and with the spinal accessory by one or two branches. It gives off the auricular branch* which is distributed to the pinna of the ear. This branch, shortly after its origin, is joined by a branch from the petrous gan- glion of the glosso-pharyngeal, and, passing outwards behind the internal jugular vein, it enters a minute foramen in the jugular fossa near the styloid process. It then proceeds through a canal in the bone, crosses the aquaeductus Fallopii, where it communicates with the facial nerve, and passes to the outside of the skull through the fissure between the mastoid process and the meatus auditorius externus. It here divides into two branches, one being distributed to the skin of the auricle, and communicating with the great auri- cular nerve; the other communicating with the posterior auricular branch of the facial over the mastoid process. This ganglion also sends backwards a meningeal branch, which passes through the jugular foramen to be distributed to the dura mater of the posterior fossa (fig. 63). The ganglion of the trunk has communications with the hypo- glossal nerve, with the loop formed between the first and second cervical nerves, and with the superior cervical ganglion of the sym- pathetic. It gives off, as branches of distribution, the pharyngeal and superior laryngeal nerves. This has been previously described (P- 147). FACIAL NERVE The facial nerve is contained within the meatus IN THE auditorius internus, together with the auditory TEMPORAL BONK. ne rve. At the bottom of the meatus the two 1 Arnold, Der Kopftlieil dcs Veget. Nerven Systems. Heidelberg, 1831. 8 Arnold's nerve. 268 FACIAL NERVE IN THE TEMPORAL BONE. nerves are connected by one or more filaments. The facial nerve then enters the aquaeductus Fallopii. This is a tortuous canal in the substance of the temporal bone, and terminates at the stylo- mastoid foramen. The nerve proceeds from the meatus audi- torius internus for a short distance outwards towards the hiatus Fallopii, where it presents a gangl ionic enlargement the intume- scentia gangliformis, or geniculate ganglion where it is joined by several nerves ; it then makes a sudden bend backwards along the inner wall of the tympanum above the fenestra ovalis, and lastly, FIG. 64. 1 . The chorda tympani. 2. The geniculate ganglion of the facial nerve. 3. The great petrosal nerve. -4. The lesser petrosal nerve lying over the tensor tympani. 5. The external petrosal nerve communicating with the sympathetic plexus on the arteria meningea media (6). 7. The Gasserian ganglion. THE GENICULATE GANGLION OF THE FACIAL NEKVE, AND ITS CONNECTIONS WITH THE OTHER NEHVES. (From Bidder.) curving downwards along the back of the tympanum, it leaves the skull through the stylo-mastoid foramen. Its branches of communication in the temporal bone are : Those in the meatus auditorius internus a. With the auditory nerve. Those in the aquaeductus Fallopii b. With Meckel's ganglion through the large petrosal nerve. c. With the otic ganglion through the small superficial petrosal nerve. d. With the sympathetic around the middle meningeal artery through the external superficial petrosal nerve. FACIAL NERVE IN THE TEMPORAL BONE. 269 1 Its branches of distribution are: e. The tympanic branch. f. The chorda tympani. a. The communicating brandies with the auditory are by several filaments, in the meatus auditorius internus. 5. The large petrosal nerve joins the carotid branch from the sympathetic to form the Vidian nerve, which joins the spheno- palatine ganglion (fig. 64, 3). c. The small superficial petrosal nerve passes along the anterior surface of the pars petrosa to join the otic ganglion below the fora- men ovale (fig. 64, 4). d. The external superficial petrosal nerve passes from the gen- iculate ganglion to the sympathetic plexus around the middle meningeal artery (fig. 64, 5). e. The tympanic branch passes through a foramen in the base of the posterior pyramid to supply the stapedius and the laxator tympani * (fig. 63, 4). /. The chorda tympani is given off from the facial nerve before its exit from the stylo-mastoid foramen. 2 It ascends a short distance in a bony canal at the back of the tympanum, and enters that cavity through a small foramen foramen chordae posterius below and external to the pyramid, close to the membrana tympani. It runs forwards, ensheathed in mucous membrane, through the tympanum, between the handle of the malleus and the long pro- cess of the incus, to the anterior part of that cavity. It emerges through a small aperture foramen chordae anterius then traverses a special bony canal canal of Huguier and makes its exit close to the fissura Glaseri. It passes downwards and forwards between the two pterygoid muscles, behind the arteria meningea media, the auriculo-temporal and inferior dental nerves, to join, at an acute angle, the lower border of the gustatory nerve. It then proceeds in part to the submaxillary ganglion, and in part to the lingualis muscle. 1 This is often not muscular, but ligamentous in structure. 2 In the foetus, this nerve is given off outside the foramen, but subsequently the bone grows downwards so as to enclose more of the facial nerve, and with it the chorda tympani. 270 INTERNAL CAROTID ARTERY THROUGH BASE OF SKULL. External to the stylo-mastoid foramen, the facial nerve com- municates with the pneumogastric, the glosso-pharyngeal, the great auricular, the auriculo-temporal nerves, and with the carotid plexus ; and on the face, with the numerous branches of the three divisions of the fifth nerve. Its branches of distribution, close to the stylo-mastoid foramen, are the posterior auricular, digastric and stylo-hyoid branches ; and on the face, branches to all the facial muscles and the platysma myoides. COURSE OF THE ^ e cerv i ca l portion of the internal carotid has INTERNAL CAROTID been already described (p. 144). Its subsequent THROUGH BASE OF course may be divided into the petrous, cavernous, SKULL. an( j cere b ra i portions. In the petrous portion, the artery takes a very tortuous course : at first it ascends for a short distance ; it then curves forwards and inwards ; and lastly, it again ascends to reach the side of the body of the sphenoid. It is situated in front of the tympanum, from which it is separated by a thin lamella of bone, which is frequently absorbed in advanced age. It gives off a tympanic branch to the tympanum and membrana tympani. In the cavernous portion, the artery again makes a series of curves : at first it ascends forwards on the side of the body of the sphenoid, and then curves upwards on the inner side of the anterior clinoid process. The artery in this part of its course lies in the inner wall of the cavernous sinus, having the sixth nerve below and to its outer side. From this portion are given off arterice re- ceptaculi to supply the pituitary body, Gasserian ganglion, and neighbouring structures ; the anterior meningeal to supply the dura mater; and the ophthalmic artery already described (p. 57). In the cerebral pm'tion, it pierces the dura mater on the inner side of the anterior clinoid process, and is surrounded by a sheath of the arachnoid membrane. It gives off the anterior cerebral, the middle cerebral, the anterior choroid, and the posterior communi- cating arteries. The internal carotid is accompanied in the carotid canal by the cranial branch of the superior cervical ganglion of the sympathetic, described p. 151. Its position on the inner wall of the cavernous sinus, and the nervous plexuses upon it, are described at p. 23. DISSECTION OF THE NOSE. 271 At this stage of the dissection we may conveniently trace the anterior divisions of the two upper cervical nerves. SUBOCCIPITAL The anterior division of the first cervical or sub- NEBVE. occipital nerve descends in front of the transverse process of the atlas to form a loop with the ascending branch of the second cervical nerve. It lies beneath the vertebral artery, on the inner side of the rectus capitis lateralis, to which it gives a branch ; as also, one to the occipito-atloid joint, one to the rectus capitis anticus minor, and one to the sympathetic around the vertebral artery. From its loop of communication with the second nerve it gives filaments of communication to the superior cervical ganglion, to the hypoglossal and pneumogastric nerves ; and muscular branches to the longus colli and rectus capitis anticus major. SECOND CEBVI- The anterior division of this nerve emerges be- CAL NEBVE. tween the arches of the atlas and axis, and passes between the vertebral artery and the intertransverse muscle, in front of which it subdivides into an ascending branch which joins the first cervical nerve, and into a descending which joins the third cervical nerve. DISSECTION OF THE NOSE. Presuming that the dissector is familiar with the bones com- posing the skeleton of the nose, we shall now describe : 1 . The nasal cartilages ; 2. The general figure and arrangement of the nasal cavities ; 3. The membrane which lines them ; and, 4. The distribution of the olfactory nerves. CARTILAGES OF THE The framework of the external nose is formed NOSE. by five cartilages; on each side by two lateral cartilages ; and by one in the centre, which completes the septum between the nasal fossae. The lateral cartilages are termed, respectively, upper and lower, which are covered externally by integument, and are lined internally by mucous membrane. The upper, triangular in shape, is connected superiorly to the margin of the nasal and superior maxilla r y bones ; anteriorly, which is its thickest part, to the cartilage of the septum ; 272 CARTILAGES OF THE NOSE. and, inferiorly, to the lower cartilage by means of a tough fibrous membrane. The lower is elongated, and curved upon itself in such a way as to form not only half the apex, but the outer and inner boundaries of the external opening of the nostrils. Superiorly, it FIG. 65. SESAMOID CARTILAGES CARTILAGE OF. SEPTUM UPPER.LATERAL CARTILAGE LOWER LATERAL CARTILAGE. CARTILAGES OF THE NOSE. is connected by fibrous membrane to the upper cartilage ; internally, it is in contact with its fellow of the opposite side, forming the upper part of the columna nasi ; posteriorly, it is attached by fibrous tissue to the superior maxillary bone ; in this tissue are usually found two or three nodules of cartilage, called cartilagines sesamoidece ; below, it is firmly connected to dense connective tissue. By their elasticity these several cartilages keep the nostrils continually open, and restore them to their ordinary size whenever they have been expanded by muscular action. The cartilage of the septum is placed perpendicularly in the middle line ; it may lean a little, however, to one side or the other, and in some instances it is perforated, so that the two nasal cavities communicate with each other. The cartilage is smooth and flat, and its outline is nearly triangular. The posterior border is re- ceived into a groove in the perpendicular plate of the ethmoid ; the anterior border is much thicker than the rest of the septum, and is connected, superiorly, with the nasal bones, and on either side with the lateral cartilages. The inferior border is attached to the vomer and the median ridge at the junction of the palatine processes of the superior maxillse. THE NASAL FOSSAE. 273 The nose receives its blood-supply from the lateralis nasi, the artery of the septum, the facial, the nasal branch of the ophthalmic, and the infra-orbital arteries. The veins are returned to the facial and ophthalmic veins. The nerves are derived from the nasal branch of the ophthalmic, the infra-orbital, and infra-trochlear nerves. Its muscles are supplied by branches from the facial nerve. The muscles moving the nasal cartilages have been described with the dissection of the face (p. 34). INTERIOR OP A vertical section should be made through the THE NOSE. right nasal cavity, a little on the same side of the middle line, 1 to expose the partly bony and partly cartilaginous partition of the nasal cavities (septum narium). Each nasal fossa is narrower above than below. The greatest perpendicular depth of each fossa is about the centre ; from this point the depth gradu- ally lessens towards the anterior and the posterior openings of the nose. Laterally, each fossa is very narrow, in consequence of the 'projection of the spongy bones towards the septum : this narrow- ness in the transverse direction explains the rapidity with which swelling of the lining membrane from a simple cold obstructs the passage of air. BOUNDARIES OF The nasal fossae are bounded by the following NASAL Fossa:. bones : superiorly, by the nasal, the nasal spine of the frontal, the cribriform plate of the ethmoid, the body of the sphenoid, and the sphenoidal turbinated bones ; inferiority., by the horizontal plates of the superior maxillary and palate bones ; inter- nally, is the smooth and flat septum formed by the perpendicular plate of the ethmoid, the ridge formed by the two nasal bones, the vomer, the septal cartilage, also by the nasal spine of the frontal, the rostrum of the sphenoid, and the crest of the superior maxillary and palate bones ; externally, by the nasal process and the inner surface of the superior maxillary, the lachrymal, the ethmoid, the palate, the inferior turbinated bones, and the internal pterygoid plate of the sphenoid. MEATUSES OF The outer wall of each nasal cavity is divided by THE NOSE. the turbinated bones into three comnartments 1 This has already been done in order to dissect the spheno-palatine ganglion. 274 MEATUSES OF THE NOSE. meatuses of unequal size ; and in these are orifices leading to air- cells sinuses in the sphenoid, ethmoid, frontal, and superior maxillary bones. Each of these compartments should be separately examined. a. The superior meat us is the smallest of the three, and does not extend beyond the posterior half of the wall of the nose. The posterior ethmoidal and sphenoidal cells open into it. The spheno- palatine foramen is covered by the mucous membrane, and is pos- terior to the meatus. b. The middle meatus is larger than the superior. At its an- terior part a long narrow passage (infundibulum), nearly hidden by a fold of membrane, leads upwards to the frontal and the anterior ethmoidal cells. About the middle a small opening leads into the antrum of the superior maxilla : this opening in the dry bone is large and irregular, but in the recent state it is reduced nearly to the size of a crow-quill by mucous membrane, so that a very little swelling of the membrane is sufficient to close the orifice entirely. Notice that the orifices of the frontal and ethmoid cells are so disposed that their secretion will pass easily into the nose. But this is not the case with the maxillary cells, to empty which the head must be inclined on one side. To see all these openings the respective turbinated bones must be raised. c. The inferior meatus extends nearly along the whole length of the outer wall of the nose. By raising the lower turbinated bone, we observe, towards the front of the meatus, the termination of the nasal duct, through which the tears pass down from the lachrymal sac into the nose. This sac and duct can now be conveniently examined. LACHRYMAL SAC The lachrymal sac and nasal duct constitute the AND NASAL DUCT. passage through which the tears are conveyed from the canaliculi into the nose (p. 33). The lachrymal sac occupies the groove formed by the lachrymal bone and the nasal process of the superior maxilla. The upper end is round and closed; the lower gradually contracts into the nasal duct, and opens into the inferior meatus. The sac is composed of a strong fibrous and elastic tissue, which adheres very closely to the bone, and is lined by MUCOUS MEMBRANE OF THE NOSE. 275 mucous membrane, continuous, above with that lining the canaliculi, and below with that of the nasal duct. Its front surface is covered by the tendo oculi and the fascia proceeding from it, and by the tensor tarsi muscle. The nasal duct is from half to three-quarters of an inch in length, and is directed downwards, backwards, and a little out- wards. Its termination is rather dilated, and is guarded by a val- vular fold of mucous membrane valve of Hasner consequently, when air is blown into the nasal passages while the nostrils are closed, the lachrymal sac does not become distended. The lachry- mal sac and the nasal duct are lined with ciliated epithelium, and the canaliculi with the squamous variety. Behind the inferior turbinated bone is the opening of the Eus- tachian tube (p. 236). Into this, as well as into the nasal duct, we ought to practise the introduction of a probe. The chief difficulty is to prevent the probe from slipping into the cul-de-sac between the tube and the back of the pharynx. Mucous OB This membrane lines the cavities of the nose and SCHNEIDERIAN the air-cells communicating with it, and adheres MEMBRANE.' very firmly to the periosteum. Its continuity may be traced into the pharynx, into the orbits through the nasal ducts and canaliculi, into the various air sinuses viz., the frontal, eth- moidal > sphenoidal sinuses, and the antra of Highmore, and into the tympana and mastoid cells through the Eustachian tubes. At the lower border of the turbinated bones it is disposed in thick and loose folds. The membrane varies in thickness and vascularity in different parts of the nasal cavities. Upon the lower half of the septum and the inferior turbinated bones it is much thicker than elsewhere, owing to a fine plexus of arteries and veins in the sub- mucous tissue. In the sinuses the mucous membrane is thinner, less vascular, and closely adherent to the periosteum. 2 1 Schneider, De Catarrhis. Wittenberg, 1660. 2 In the mucous membrane covering the lower part of the septum, in front, may be observed a small orifice which leads into a narrow blind channel, a few millimetres in length. This canal has numerous glands opening into it, and is the represen- tative of a much larger tubular organ (organ of Jacobson) in some quadrupeds, in whom it is surrounded by a curved plate of cartilage (cartilage of Jacobson). In T 2 276 MUCOUS MEMBRANE OF THE NOSE. The great vascularity of the mucous membrane raises the tem- perature of the inspired air, and pours out a copious secretion which prevents the membrane from becoming too dry. The mucous membrane of the nasal cavities is not lined through- out by the same kind of epithelium. Near the nostrils the mucous membrane is furnished with papillae, with a squamous epithelium like the skin, and a few small hairs (vibrissce). In the lower part of the nose namely, along the respiratory tract and in the sinuses the epithelium is columnar and ciliated ; but in the true olfactory region that is, upon the superior and middle turbinated bones and the upper half of the septum the epithelium is columnar, but not ciliated. In this region the mucous membrane is extremely vascular, thick, and studded with branched mucous glands. The columnar epithelial cells taper off at their deep ends into fine pro- cesses. Lying between these processes are fusiform cells, with central well-defined nuclei, to which the name of olfactory cells J has been given ; and it is probable that the attenuated processes which pass inwards from these cells are in direct connection with the terminal fibrils of the olfactory nerves. The arteries of the nasal cavities are derived from the anterior and posterior ethmoidal branches of the ophthalmic, which supply the roof of the nose, the anterior and posterior ethmoidal cells, and the frontal sinuses ; from the nasal artery of the internal maxillary, which supplies the septum, the meatuses, and the turbinated bones ; from the posterior dental branch of the internal maxillary which supplies the antrum. The external nose is supplied by the nasal branch of the ophthalmic (p. 59), the arteria lateralis nasi, the angular, and the artery of the septum. . The veins of the nose correspond with the arteries, and, like them, form close plexuses beneath the mucous membrane. They communicate with the veins within the cranium, through the fora- mina in the cribriform plate of the ethmoid bone ; also through the ophthalmic vein and the cavernous sinus. These communications man this cartilage is very narrow, and is situated below the rudimentary organ. For further information, see Klein, Quart. Journ. of Micros. Science, 1881 and 1882. 1 Max Schultze, Med. Centralblatt, 1864. OLFACTORY NERVES. 277 explain the relief frequently afforded by haemorrhage from the nose in cases of cerebral congestion. The mucous membrane of the nose is supplied with sensory nerves by the fifth pair. Thus, its roof is supplied by filaments from the external division of the nasal branch of the ophthalmic, and from the Vidian ; its outer wall, by filaments from the superior nasal branches of the spheno-palatine ganglion, from the nasal, from the inner branch of the anterior dental, and from the inferior nasal branches of the large palatine nerve ; its septum, by the septal branch of the nasal nerve, by the nasal branches of the spheno-palatine ganglion, by the naso-palatine, and by the A 7 idian ; its floor, by the naso-palatine, and the inferior nasal branches of the large palatine nerve. OLFACTORY The olfactory nerves, proceeding from each olfac- NEKVES. tory bulb, in number about twenty on .each side, pass through the foramina in the cribriform plate of the ethmoid bone. In its passage each nerve is invested with a coat derived from the dura mater. They are arranged into an inner, a middle, and an outer set. The septal, which are -the largest, traverse the grooves in the upper third of the septum. The middle ramify on the roof of the nose. The outer pass through grooves, and are divided into an anterior and a posterior group : the anterior being distributed over the superior turbinated bone, the posterior over the os planum of the ethmoid and the middle turbinated bone. The nerves descend obliquely between the mucous membrane and the periosteum, and break up into filaments, which communi- cate freely with one another, and form minute plexuses with small elongated intervals. Microscopically, the filaments differ from the other cerebral nerves, in containing no white substance of Schwann, and in their axis-cylinders being provided with a very distinct nucleated sheath with fewer nuclei and at longer intervals. 278 MUSCLES OF THE BACK. DISSECTION OF THE MUSCLES OF THE BACK. DISSECTION TO Those muscles of the back namely, the tra- EXPOSE THE THIED pezius, latissimus dorsi, levator anguli scapulas, LAYER OF an( J rhomboidei which are concerned in the movements of the upper extremity, will be ex- amined in the dissection of the arm. These must be reflected near to their insertions, together with the cutaneous vessels and nerves. We now proceed to examine the three muscles forming the third layer of muscles, named, from their appearance, serrati postici, superior and inferior, and the splenius. The nerves and arteries will be described after the dissection of the suboccipital triangle. SERBATUS Pos- This muscle is situated beneath the rhomboidei. TICUS SUPERIOR. It is a thin flat muscle, and arises from the lower part of the ligamentum nuchas, 1 from the spinous processes of the last cervical, and two or three upper dorsal vertebra, by a sheet- like aponeurosis which makes up nearly half the muscle ; the fibres run obliquely downwards and outwards, and are inserted by four fleshy slips into the second, third, fourth, and fifth ribs beyond their angles. Its action is to raise these ribs, and therefore to assist in inspiration. SERRATTJS Pos- This muscle is situated in the upper lumbar TICUS INFERIOR. region, beneath the latissimus dorsi. It arises, by means of the lumbar aponeurosis, from the spinous processes of the two last dorsal and two upper lumbar vertebras and their supra-spinous ligament. It ascends obliquely outwards, and is inserted by four fleshy slips into the four lower ribs, external to their angles. Its action is to pull down these ribs, and therefore to assist in expiration. The posterior serrati muscles are supplied, 1 The ligamentum nuchse is a rudiment of the great elastic ligament of quadru- peds (termed the pack-wax) which supports the weight of the head.. It proceeds from the spine of the occiput to the spines of all the cervical vertebrae except the atlas ; otherwise it would interfere with the free rotation of the head. VERTEBRAL APONEUROSIS. 279 respectively, by the external branches of the posterior divisions of the cervical and dorsal nerves. VERTEBRAL The thin aponeurosis which, in the posterior APONEUROSIS. aspect of the thoracic region, separates the muscles of the upper extremity from those of the back, is called the vertebral aponeurosis. Superiorly, it is continued beneath the splenius, and is continuous with the deep cervical fascia ; inferiorly, it binds down the muscles contained in the vertebral groove, and is attached to the upper border of the serratus posticus inferior, and the tendon of the latissimus dorsi ; internally, it is attached to the spinous processes of the dorsal vertebras, and externally to the angles of the ribs. This aponeurosis consists of three layers, of LUMBAR FASCIA. , . . . , , , , which only the posterior layer can now be seen ; the other two being demonstrated in the dissection of the abdo- FIG. 60. ERECTOR SP. TRANSVERSE SECTION THROUGH THE ABDOMEN TO SHOW THE ATTACHMENT OF THK THREE LAYERS OF THE LUMBAR FASCIA TO THE TRANSVERSE AND SPINOUS PROCESSES OF THE LUMBAR VERTEBRAE. minal muscles. The posterior or superficial layer is attached to the crest of the ilium, to the spinous processes of all the lower dorsal , lumbar, and sacral vertebras ; it forms a sheath for the erector spinae, and serves for the attachment of the latissimus dorsi, the serratus posticus inferior, and the internal oblique. 280 MUSCLES OF THE BACK. PIG. 67. THE SUPERFICIAL MUSCLES OF THE BACK. MUSCLES OF THE BACK. 281 The serratus posticus superior must now be reflected from its origin, and turned outwards to expose the following muscle. This muscle, so called from its resemblance to SPLENIDS. , , a strap, arises from the spinous processes of the five or six upper dorsal and the last cervical vertebrae, from the supra-spinous ligament, and from the lower half of the ligamentum nuchae. The fleshy fibres pass upwards and outwards and divide into two portions, named, according to their respective insertions, splenius capitis and splenius colli. a. The splenius capitis, the inner of the two portions, is in- serted into the mastoid process, and into the outer part of the superior curved line of the occipital bone, beneath the sterno- mastoid. b. The splenius colli, the outer of the two portions, is inserted by tendinous slips into the posterior tubercles of the transverse processes of the upper three cervical vertebrae. The splenius is supplied by the external branches of the posterior divisions of the cervical nerves. The action of the splenius, taken as a whole, is to draw the head and the upper cervical vertebras towards its own side : so far, it co-operates with the opposite sterno-mastoid muscle. When the splenii of opposite sides contract, they extend the cervical portion of the spine, and keep the head erect. The permanent contraction of a single splenius may occasion wry-neck. It is necessary to be aware of this, otherwise one might suppose the opposite sterno-mastoid to be affected, considering that the ap- pearance of the distortion is alike in either case. DISSECTION TO To lay bare the fourth layer of muscles, the EXPOSE THE splenius and serratus posticus inferior are to be FOURTH LATER. detached from their origins. After reflecting the vertebral aponeurosis and the lumbar fascia from its internal attachment, the erector spinas and its prolongations are exposed. The mass of muscle which occupies the vertebral groove on each side of the spine, is, collectively, called erector spince, since it counteracts the tendency of the trunk to fall forwards. It is pointed at its lower tendinous extremity where it arises from the sacral region ; in the lumbar region it is broad, thick and muscular; in the lower dorsal region 282 ERECTOR SPIN.E. \ .-3 O O o ft 3 PS 8 o w PS w ARRANGEMENT OF THE ERECTOR SPIN.E AND IITS PROLONGATIONS INTO THE POSTERIOR THORACIC AND CERVICAL REGIONS. it divides into two portions, which are continued upwards with addi- tional muscles into the cervical verte- bra and the head. Observe that it is thickest and strongest at that part of the spine where it has the greatest weight to support namely, in the lumbar region ; and that its thickness gradually decreases towards the top of the spine. It arises by thick tendinous fibres from the spinous processes of the two or three lowest dorsal and of all the lumbar vertebras, from the spines of the sacrum, from the supra-spinous ligament, from the posterior fifth of the inner lip of the crest of the ilium, from the lower and back part of the sacrum, and from the posterior sacro- iliac ligament. From this extensive origin the muscular fibres ascend, at first as a single mass. Near the last rib, this mass divides into two : an outer, called the ilio-costalis or sacro- lumbalis ; an inner, the long-issimus dor si. These two portions should be followed up the back ; and there is no difficulty in doing so, because the division is indicated by a longitudinal groove, in which we observe the ex- ternal cutaneous branches of the in- tercostal vessels and nerves. ILIO-COSTALIS OK Tracing the ilio-cos- SACRO-LUMBALIS. ialis or sacro-lumbalis upwards, we find that it terminates in a series of tendons which are in- serted into the angles of the six lower ribs. MUSCLES OF THE BACK. 283 MUSCULUS By turning outwards the ilio-costalis, we ACCESSORIUS. observe that it is continued upwards under the name of musculus accessorius ad ilio-costalem. This arises by a series of tendons from the angles of the six lower ribs, internal to the preceding, and is inserted by muscular slips into the angles of the six upper ribs. CERVICALIS This is the cervical continuation of the musculus ASCENDENS. accessorius. It arises by tendinous slips from the angles of the four or five upper ribs, internal to the musculus accessorius, and is inserted into the posterior tubercles of the transverse processes of the fourth, fifth and sixth cervical ver- tebrae. LONGISSIMUS The longissimus dorsi (the inner portion of the DORSI. erector spina3) terminates in tendons which are inserted, internally, into the tubercles * at the root of the transverse processes of the lumbar vertebra3, into the tubercles of the articular processes of the same vertebrae, into the middle layer of the fascia lumborum, also into the transverse processes of all the dorsal vertebrae and, externally, into the greater number of the ribs (vary- ing from eight to eleven) between their tubercles and angles. TRANSVEKSALIS This is the cervical continuation of the longissi- COLLI. mus dorsi. It arises by long tendinous slips from the tips of the transverse processes of the five or six upper dorsal vertebrae, and is inserted into the posterior tubercles of the trans- verse processes of the four or five lower cervical vertebrae except the last. TKACHELO- This muscle, situated on the inner side of the MASTOID. preceding, and external to the complexus, is the internal continuation of the longissimus dorsi to the cranium. It arises from the transverse processes of the three or four upper dorsal, and the articular processes of the three or four lower cervical ver- tebrae, and is inserted by a flat tendon into the back part of the mastoid process beneath the splenius. 2 1 Called anapophyses by Professor Owen. 2 Those who are familiar with the transcendental nomenclature of the verte- brate skeleton will understand from the following quotation the plan upon which the muscles of the back are arranged : ' The muscles of the back are either longitudinal or oblique : that is, they either pass vertically downwards from spinous process to spinous process, from diapo- .284 MUSCLES OF THE BACK. This is a long narrow muscle, situated close to SPINALIS DOKSI. , . / .1 i i . i ' i , , the spines or the dorsal vertebras, and apparently the inner part of the longissimus dorsi ; it is by some considered the innermost column of the erector spinas. It arises by tendinous slips from the spinous processes of the two lower dorsal and two upper lumbar vertebrae, and is inserted by little tendons into the spinous processes of the six or eight upper dorsal vertebras. Beneath it, is the semi-spinalis dorsi, which is closely connected with the spinalis dorsi. This small, but not constant muscle corresponds SPINAUS COLLI. . , . , . . . , . , . . 1 in the cervical region to the spinalis dorsi in the dorsal region. It arises by tendinous slips from the spinous processes of the two or three lower cervical vertebras (sometimes also from the two upper dorsal), and is inserted into the spine of the axis, and occasionally into the spinous processes of the third and fourth cervical. physis to diapophysis, from rib to rib (pleurapophysis),&c., or they extend obliquely from diapophysis to spine, or from diapophysis to pleurapophysis, &c. ' The erector spinse is composed of two planes of longitudinal fibres aggregated together, below, to form one mass at their poini of origin, from the spines and posterior surface of the sacrum, from the sacro-iliac ligament, and from the pos- terior third of the iliac crest. It divides into two portions, the sacro-lumbalis and the longissimus dorsi. ' The former, arising from the iliac crest, or from the pleurapophysis (rib) o the first sacral vertebra, is inserted by short flat tendons into (1) the apices of the stunted lumbar ribs, close to the tendinous origins of the transversalis abdominis ; (2) the angles of the eight or nine inferior dorsal ribs ; (3) it is inserted, through the medium of the musculus accessorius, into the angles of the remaining supe- rior ribs, and into the long and occasionally distinct pleurapophysial element of the seventh cervical vertebra ; and (4) through the medium of the cervicalis ascendens, into the pleurapophysial elements of the third, fourth, fifth, and sixth cervical vertebrae. In other words, the muscular fibres extend from rib to rib, from the sacrum to the third cervical vertebra. ' The longissimus dorsi, situated nearer the spine than the sacro-lumbalis, is inserted (1) into the metapophysial spine of the lumbar diapophyses ; (2) into the diapophyses of all the dorsal vertebrae, near the origin of the levatores costarum ; (3) through the medium of the transversalis colli into the diapophyses of the second, third, fourth, fifth, and sixth cervical vertebrae ; and (4) through the medium of the trachelo-mastoid into the mastoid process, or the only element of a transverse process possessed by the parietal vertebra. In other words, its fibres extend from diapophysis to diapophysis, from the sacrum, upwards, to the parietal vertebra.' Homologies of the Human Skeleton, by H. Coote, p. 75. MUSCLES OF THE BACK. 285 The muscles of the spine hitherto examined are all longitudinal in their direction. We now come to a series which run obliquely from the transverse to the spinous processes of the vertebras. And first of the complexus. This powerful muscle arises by tendinous slips from the transverse processes of the three or four upper dorsal and the last cervical vertebras, also from the articular processes of four or five cervical vertebrae and their capsular liga- ments. It is inserted between the two curved lines of the occiput, near the vertical crest. In the centre of the muscle there is generally a transverse tendinous intersection. The muscle is perforated by the posterior branches of the second (the great occipital), third, and fourth cervical nerves. It is chiefly supplied by the great occipital nerve. Its action is to maintain the head erect. BIVENTEB Is placed in the inner side of the preceding CERVICIS. muscle and frequently forms part of it. It has an intermediate tendon, and arises from the transverse processes of two or three upper dorsal vertebras, and ascends between the liga- mentum nuchas and the complexus, to be inserted into the inner- most depression between the two curved lines of the occipital bone. Cut transversely through the middle of the complexus, and reflect it to see the arteria cervicalis profunda (p. 123), and the posterior branches of the cervical nerves. DISSECTION TO Remove the complexus, and then turn aside EXPOSE THE FIFTH the erector spinas and its prolongations, when the LAYEK> fifth layer of muscles will be seen occupying the interval between the spinous and transverse processes. TBANSVEESO- This is the mass of muscle which lies in the SPINALIS. vertebral groove after the reflection of the com- plexus and the erector spinae. It consists of a series of fibres which extend from the transverse and articular processes to the spinous processes of the dorsal and cervical vertebras, and is for convenience divided into the semispinalis dorsi and semispinalis colli. a. The semispinalis dorsi arises by long thin tendinous slips from the transverse processes of the dorsal vertebras, from the sixth to the tenth, and is inserted into the spinous processes of the four 286 MUSCLES OF THE BACK. upper dorsal and the two or three lower cervical vertebrae. Its nerves are derived from the internal posterior branches of the dorsal nerves. 6. The semispinalis colli lies beneath the complexus, and arises from the transverse processes of the five or six upper dorsal ver- tebrae, and the articular processes of the four lower cervical, and is inserted into the spinous processes of the axis and the three or four succeeding vertebrae, that into the axis being the most fleshy fasci- culus. It is supplied by the internal posterior branches of the cervical nerves. Now reflect part of the semi-spinalis dorsi in order to expose the multifidus spinae. MULTIFIDUS This may be considered a part of the preceding SPINAE. muscle, since its fixed points and the direction of its fibres are the same. It consists of a series of little muscles which extend between the spinous and transverse processes of the vertebrae, from the sacrum to the second cervical vertebra. Those in the lumbar region are the largest. In the sacral region the fibres arise from the back of the sacrum as low down as the fourth fora- men, from the deep surface of the aponeurosis of the erector spinae, from the inner part of the posterior superior iliac spine, and from the posterior sacro-iliac ligament ; in the lumbar region, from the mammillary processes on the superior articular processes ; in the dorsal region, from the transverse processes, and in the cervical region from the articular processes of the four lower cervical ver- tebrae. They all ascend obliquely, and each fasciculus is inserted into the lamina and spinous process of the vertebra above, except the atlas. It should be observed that their fibres are not of uniform length ; some extend only from vertebra to vertebra, while others extend between one, two, or even three vertebrae. It is supplied by the internal posterior branches of the sacral, lumbar, dorsal, and cervical nerves. EOTATORES Beneath the multifidus spinae, in the dorsal SPIN.E. region of the spine only, are eleven flat and some- what square muscles, called rotatores spince. They arise from the upper and back part of the transverse processes, and are inserted into the lower border of the laminas of the vertebra above. These MUSCLES OF THE BACK. 287 muscles form but a part of the multifidus spinas, and are supplied by the internal posterior branches of the dorsal nerves. The action of the preceding muscles is, not only to assist in maintaining the trunk erect, but to incline and rotate the spine to one or the other side. They are all supplied by the posterior branches of the spinal nerves. LEVATOBES These small muscles, twelve in number, on each COSTABUM. side, arise from the apices of the transverse pro- cesses of the seventh cervical and the eleven upper dorsal vertebrae, and are inserted into the rib below. The direction of their fibres corresponds with that of the outer layer of the intercostal muscles, and they are supplied by the internal posterior branches of the dorsal nerves. They are muscles of inspiration. These are formed by a series of small muscular SUPEA-SPINALES. ,. , . , , slips lying over the spinous processes of the cer- vical vertebras. Their nerves are derived from the internal posterior branches of the cervical nerves. These muscles extend between the spinous pro- INTEB-SPINALES. ,, , , ,. , , mi cesses or the contiguous vertebrae. Ihey are ar- ranged in pairs, and only exist in those parts of the vertebral column which are most moveable. In the cervical region, they are the most distinct, and pass between the spinous processes of the six lower cervical vertebrae. In the dorsal, they are found between the spinous processes of the first and second, and between those of the eleventh and twelfth dorsal vertebras. They are also found more or less distinctly between the spinous processes of the lumbar vertebras. They are supplied by the internal posterior branches of the spinal nerves. INTEB-TBANS- These muscles extend between the transverse VEBSALES. processes of the vertebrae. In the cervical region they are seven in number, and are most marked, being arranged in pairs, and extend between the anterior and posterior tubercles of contiguous vertebras. The anterior branch of the corresponding cervical nerve separates the two fasciculi. In the dorsal region these muscles in the upper part are represented by small round tendons, but in the three lower dorsal vertebrae they again become muscular in structure. In the lumbar region the muscular fasciculi 288 MUSCLES OF THE BACK. are four in number, and are also arranged in pairs between the transverse processes. Their nerve-supply is derived from the internal posterior branches of the cervical, dorsal, and lumbar nerves. We have next to examine the muscles concerned in the move- ments of the head upon the first and second cervical vertebras (fig. 68). FIG. 68. DRAWING FROM NATURE OF THE SUBOCCIPITAL TRIANGLE. 1 and 7. Complexus. 2. Eectus cap. posticus minor. 3. Reotns cap. posticus major. 4. Obliquus inferior. 5. Sterno-mastoid. 6. Semispinalis colli. 8. Obliquus superior. 10. Splenms. 11. Trachelo-mastoid. 12. Great occipital nerve. 13. Occipital artery giving off its descending branch the pnnceps cer-eicis. 14. Suboccipital nerve. 15. Third cervical nerve (posterior branch). EECTUS CAPITIS This is a largely developed interspinal muscle. POSTICUS MAJOR. It arises by a small tendon from the well-marked spinous process of the second cervical vertebra, and, expanding con- siderably, is inserted into the inferior curved ridge of the occipital bone, and into the surface of bone below it. These recti muscles, as they ascend, one on each side, to their insertions, diverge and leave an interval between them in which are found the recti capitis postici minores. NERVES OF THE BACK. 289 EECTUS CAPITIS This is an interspinal muscle, but smaller than POSTICUS MINOR. the preceding. Arising from the posterior tubercle of the first vertebra, it expands as it ascends, and is inserted into the occipital bone between the inferior curved ridge and the fora- men magnum. The action of the two preceding muscles is to raise the head. They are supplied with nerves from the'posterior branch of the suboccipital. OBLIQUUS This arises from the spinous process of the second INFERIOR. cervical vertebra, and is inserted into the transverse process of the first. Its action is to rotate the first upon the second vertebra : in other words, to turn the head round to the same side. It is supplied with a nerve by the great occipital (posterior division of the second cervical), which curves up under its lower border. OBLIQUUS This muscle arises from the transverse process SUPERIOR. of the atlas, and, ascending obliquely inwards, is inserted in the interval between the curved ridges of the occipital bone. Its action is to draw the occiput towards the spine. SUBOCCIPITAL Observe that the obliqui (superior and inferior) TRIANGLE. and the rectus capitis posticus major form what is called the suboccipital triangle. The outer side is formed by the obliquus superior ; the inner, by the rectus capitis posticus major ; the lower, by the obliquus inferior. Within this triangle may be seen the arch of the atlas, the vertebral artery lying in a groove on its upper surface, and the posterior occipito-atloid ligament. Be- tween the artery and the bone appears the posterior division of the suboccipital nerve, which here sends branches to the recti postici, the obliqui, and the complexus : that is to say, it supplies the muscles which form the triangle, and the complexus that covers it. EECTUS CAPITIS This small muscle extends between the trans- LATERALIS. verse process of the first vertebra and the eminentia jugularis of the occiput ; but, since this eminence is the transverse process of the occipital vertebra, the muscle should be considered as an intertransverse one. Its nerve comes from the anterior division of the suboccipital. NERVES OF THE Th^ posterior branches of the spinal nerves sup- BACK. ply the muscles and skin of the back. They pass backwards between the transverse processes of the vertebrae, and u 290 NERVES OF THE BACK. divide into external and internal branches. The general plan upon which these nerves are arranged is the same throughout the whole length of the spine ; but, since there are certain peculiarities de- serving of notice in particular situations, we must examine each region separately. CEKVICAL The posterior division of the first cervical nerve EEGION. (the suboccipital) passes between the arch of the atlas and the vertebral artery ; it then enters the suboccipital triangle, and divides into branches which supply the muscles : one, which passes downwards to supply the inferior oblique, and also sends downwards a branch to communicate with the second cervical nerve ; another passes upwards to supply the recti capitis major and minor ; another supplies the obliquus superior ; another enters the com plexus ; and, lastly, a cutaneous branch is sometimes given off which accompanies the occipital artery, and is distributed to the back of the scalp. The posterior branch (the great occipital) of the second cervical nerve is the largest of the series, and emerges between the arches of the atlas and axis. It turns upwards beneath the inferior oblique muscle, passes through the complexus, and runs with the occipital artery to the back of the scalp. The posterior divisions of the six lower cervical nerves divide into external and internal branches. The external are small, and terminate in the splenius, and the continuation of the erector spinse viz., the trachelo-mastoid, the transversalis colli, and the cervicalis ascendens. The internal, by far the larger, proceed towards the spinous processes of the vertebrae ; those of the third, fourth, and fifth lie between the complexus and the semispinalis, 1 and after supplying the muscles terminate in the skin over the trapezius ; those of the sixth, seventh, and eighth lie between the semispinalis and the multifidus spinae, to which they are distributed, and do not as a rule give off any cutaneous branches. D ORSAL The posterior divisions of the spinal nerves in EEGION. this region come out between the transverse pro- 1 The posterior branches of the second, third, and fourth nerves are generally connected, beneath the complexus, by branches in the form of loops. This consti- tutes ih& posterior cervical plexus of some anatomists. NERVES OF THE BACK. 291 cesses and the tendons attached to them. They soon divide into external and internal branches. The external pass obliquely over the levatores costarum, between the ilio-costalis and the longissimus dorsi ; and successively increase in size from above downwards. The upper six terminate in the erector spinae and the levatores cos- tarum ; the lower six, after supplying these muscles, pass through the latissimus dorsi, and become the cutaneous nerves of the back. The internal successively decrease in size from above downwards. They run towards the spine between the semispinalis dorsi and the multifidus spinse. The upper six, after giving branches to the muscles, perforate the trapezius and become cutaneous nerves. The lower ones terminate in the muscles of the vertebral groove. LUMBAR The general arrangement of the nerves in this REGION. region resembles that of the dorsal. Their external branches, after supplying the erector spinae, become cutaneous and terminate in the skin over the buttock. The internal branches supply the multifidus spinae. The posterior divisions of the spinal nerves in SACRAL REGION. . \ . -nrM.1. .0. *. e ^ this region are small. With the exception or the last, they come out of the spinal canal through the foramina in the back of the sacrum. The upper two or three divide into external and internal branches. The internal terminate in the multifidus spinae ; the external become cutaneous and supply the skin of the gluteal region. The last two sacral nerves proceed, without divi- ding, to the integument. The coccygeal nerve is exceedingly small, and, after joining a small branch from the last sacral, terminates in the skin over the coccyx. ARTERIES OF The arteries which supply the back are : 1 . THE BACK. Small branches from the occipital ; 2. Small branches from the vertebral; 3. The deep cervical; 4. The pos- terior branches of the intercostal and lumbar arteries. The occipital artery furnishes several small branches to the muscles at the back of the neck ; one, larger than the rest, the arteria princeps cervicis, descends beneath the complexus, and generally inosculates with the deep cervical artery, and with small branches from the vertebral. r 2 FIG. (59. a, a, Small occipital nerve from the cervical plexus ; 1, external muscular branches of the first cer- vical nerve and union by a loop with the second ; 2, the rectus capitis posti- cus major, with the great occipital nerve passing round, the short muscles and piercing the corn- plexus ; the external branch is seen to the outside ; 2', the great occi- pital ; 3, external branch of the posterior primary division of the third nerve ; 3', its internal branch, or third occipital nerve ; 4', 5', 6', 7', 8', internal branches of the several corn spending nerves on the left side ; the external branches of these nerves proceeding to muscles are displayed on the right side : d 1 to d 6, and thence to d 12, ex- ternal muscular branches of the posterior primary divisions of the twelve dorsal nerves on the right side ; d I', to d 6', the in- ternal cutaneous branches of the six upper dorsal nerves on the left side ; d T to d 12', cutaneous branches of the six lower dorsal uerves from the ex- ternal branches ; I, I, ex- ternal branches of the pos- terior primary branches of several lumbar nerves on the right side piercing the muscles, the lower descending over the glu- teal region ; V, I', the same more superficially on the left side'; *, t, on the right side, the issue and union by loops of the posterior primary divisions of four sacral nerves ; i', s', some of these distributed to the skin on the left side. DIAGKAM OF THE CUTANEOUS NERVES OF THE BACK. PRE VERTEBRAL MUSCLES. 293 The vertebral artery runs along the groove in the arch of the atlas, and, before perforating the posterior occipito-atloid liga- ment to enter the skull, distributes small branches to the adjacent muscles. The deep cervical artery is the posterior branch of the first intercostal artery (from the subclavian). It passes backwards between the transverse process of the last cervical vertebra and the first rib : it then ascends between the complexus and the semispinalis colli, and anastomoses with the princeps cervicis. The posterior branches of the intercostal and lumbar arteries accompany the corresponding nerves, and are in all respects similar to them in distribution. Each sends a small branch into the spinal canal (intraspinal), and small branches to the vertebra. The veins correspond to the arteries. PREVEKTEBKAL We have, lastly, to examine three muscles, MUSCLES. situated in front of the spine : namely, the longus colli, the rectus capitis anticus major, and the rectus capitis anticus minor. In order to have a complete view of the two latter, a special dissection should be made, before the head is removed from the first vertebra. This muscle is situated in front of the spine, and extends from the third dorsal vertebra to the atlas. For convenience of description it is divided into three sets of fibres, of which one extends longitudinally from the body of one vertebra to that of another ; the two others extend obliquely between the transverse processes and the bodies of the vertebrae. The longitudinal portion of the muscle arises from the bodies of the three upper dorsal and the three lower cervical vertebrae, and is inserted into the bodies of the second, third and fourth cervical vertebrae. The superior oblique portion, arising from the anterior tubercles of the transverse processes of the third, fourth, and fifth cervical vertebrae, ascends inwards, and is inserted into the front part or body of the atlas. The inferior oblique portion proceeds from the bodies of the three upper dorsal vertebrae, and passing upwards and outwards, is inserted into the transverse processes of the fifth and sixth cervical vertebrae. The action of this muscle, taken as a 294 PRE VERTEBRAL MUSCLES. whole, must be to bend the cervical region of the spine. Its nerves come from the lower cervical nerves. RECTUS CAPITIS This muscle arises by tendinous slips from the ANTICUS MAJOR. anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebras, and, ascending FIG. 70. DIAGRAM OF THE PEEVEETEBEAL MUSCLES. 1-7. The bodies of the cervical vertebrae : below ore the bodies of the three upper dorsal vertebrae. a. Bectus capitis lateralis. 6. Rectus capitis anticns major. c. Bectus capitis anticus minor. d. Intertransverse muscle. e. Scalenus anticus. /. Scalenus medius. g. Longus colli. h. Scalenus posticus. obliquely inwards, is inserted into the basilar process of the occipital bone, in front of the foramen magnum. RECTUS CAPITIS This muscle arises from the front of the root of ANTICUS MINOR. the transverse process of the atlas, and is inserted into the basilar process of the occipital bone, nearer to the foramen magnum than the preceding muscle. The action of the recti LIGAMENTS OF THE SPINE. 295 muscles is to bend the head forwards. They are supplied with nerves from the anterior division of the suboccipital, and from the deep cervical plexus. LIGAMENTS OF THE SPINE. The vertebras are connected by their intervertebral fibre-carti- lages, by ligaments in front of and behind their bodies, and by ligaments which extend between their arches and their spines. Their articular processes have capsular ligaments, and synovial membranes. ANTERIOR COM- This is a strong broad band of longitudinal MON LIGAMENT. fibres which extends along the front of the bodies of the vertebrae, from the axis to the sacrum. The ligament is broader below than above, thickest in the dorsal region, and its fibres are more firmly adherent to the intervertebral cartilages and to the borders of the vertebrae, than to the middle of the bones. The fibres are not all of equal length ; the more superficial extend from one vertebra to the fourth or fifth below it ; those a little deeper pass from one vertebra to the second or thir;l below it ; while the deepest of all proceed from vertebra to vertebra. Above, it is attached to the axis by a pointed process, where it is con- nected with the longus colli, and it is thicker over the bodies of the vertebra than over the intervertebral cartilages, thus filling up the concavities of the bodies and rendering the surface more smooth and even. POSTERIOE COM- This extends longitudinally, in a similar man- MON LIGAMENT. ner to the anterior common ligament, within the spinal canal, along the posterior surface of the bodies of the vertebrae, from the axis to the sacrum. It is broader above than below, and, like the anterior ligament, is thickest in the dorsal region, and is more intimately connected with the intervertebral fibro-cartilages than with the bodies of the vertebrae. It sends up a prolongation to the anterior border of the foramen magnum continuous with the apparatus ligamentosus. INTEBSPINOUS These bands of ligamentous fibres fill up the LIGAMENTS. intervals between the spines of the dorsal and 296 LIGAMENTS OF THE SPINE. lumbar vertebras. They are the most marked in the lumbar SUPRASPINOUS region. Those fibres which connect the apices LIGAMENT. of the spines, being stronger than the rest, are described as a separate ligament under the name of supraspinous. It extends from the spinous process of the seventh cervical to the spine of the sacrum ; and is strongest in the lumbar region. Their use is to limit the flexion of the spine. LIGAMENTS These are called, on account of their colour, BETWEEN THE ligamenta subflava. To obtain a good view of ARCHES OF THE them, the arches of the vertebrae should be re- moved with a saw, and the ligaments should be seen from within, since viewed from without they are to a large extent hidden by the overlapping laminae. They pass between the laminae of the contiguous vertebrae, from the axis to the sacrum ; none existing between the occiput and the atlas, or between the atlas and the axis. Each ligament consists of two halves which are attached to the corresponding half laminae above and below on each side. They are composed of yellow elastic tissue, the fibres being arranged vertically, and their strength increases with the size of the vertebrae. This elasticity answers a double purpose : it not only permits the spine to bend forwards, but materially assists in restoring it to its curve of rest. They economise muscular force, like the ligamentum nuchae in animals. INTERVERTE- This substance, placed between the bodies of BRAL FIBRO- the vertebrae, is by far the strongest bond of con- CARTILAGE. nection between them, and fulfils most important purposes in the mechanism of the spine. Its peculiar structure is adapted to break shocks, and to render the spine flexible and resilient. To see the structure of an intervertebral fibro-cartilage, a horizontal section must be made through it. It is firm and resisting near the circumference, but soft and pulpy towards the centre. The circumferential portion is composed of concentric layers of fibro-cartilage, placed vertically. These layers are attached by their edges to the vertebrae ; they gradually decrease in number from the circumference towards the centre ; and the interstices between them are filled by soft pulpy tissue. The central portion is composed almost entirely of this pulpy tissue ; INTERVERTEBRAL FIBRO-CARTILAGES. 297 and it bulges when no longer under pressure. Thus the bodies of the vertebras, in their motions upon each other, revolve upon an elastic cushion tightly girt all round by bands of fibrous tissue. These motions are regulated by the articular processes. Dissect an intervertebral substance layer after layer in front, and you will find that the circumferential fibres extend obliquely between the vertebrae, crossing each other like the branches of the letter X (fig. 72). The thickness of the intervertebral cartilages is not the same in front and behind. It is this difference in their thickness, more than that in the bodies of the vertebrae, which produces the several curves of the spine. In the lumbar and cervical regions they are thicker in front ; in the dorsal region, behind. The structure of the intervertebral cartilages explains the well- known fact that a man becomes shorter after standing for some hours ; and that he regains his usual height after rest. The difference between the morning and evening stature amounts to more than half an inch. It also explains the fact that a permanent lateral curvature of the spine may be produced (especially in the young) by the habitual practice of leaning to this or that side. Experience proves that the cause of lateral curvature depends more frequently upon some alteration in the structure of the fibro-cartilages than upon the bones. From an exami- nation of the bodies of one hundred and thirty-four individuals with crooked spines, it was concluded that, in two-thirds, the bones were perfectly healthy ; that the most frequent cause of curvature resided in the intervertebral substances, these being, on the concave side of the curve, almost absorbed, and, on the convex side, preternatu rally deve- loped. As might be expected in these cases, the muscles on the convex side become lengthened, and degenerate in structure. 1 LIGAMENTUM This ligament is a thin fibrous septum inter- NUCH;E. mingled with elastic tissue, situated in the middle line, and extends from the spinous processes of the cervical ver- tebrae to the external occipital protuberance. It forms an inter- muscular septum down the back of the neck, and may be regarded as the continuation upwards of the supraspinous ligament. CAPSULAB Each joint between the articular processes has LIGAMENTS. a synovial membrane surrounded by loose liga- 1 On this subject see Hildebrandt's Anatomic, B. ii. s. 155. 298 LIGAMENTS BETWEEN OCCIPITAL BONE AND ATLAS. mentous fibres, forming a capsular ligament which is longest in the cervical vertebras, thus allowing free movement in this region. The surfaces of the bones are crusted with cartilage. INTEKTKANS- These are thin bands of fibres which pass be- VEESE LIGAMENTS, tween the transverse processes of the vertebras. They are rudimentary in the cervical region, and are sometimes absent. MOVEMENTS OP Though but little movement is permitted be- THE SPINE. tween any two vertebras (the atlas and axis ex- cepted), yet the collective motion between them all is considerable. The spine can be bent forwards, backwards, or on either side ; it also admits of slight rotation. In consequence of the elasticity of the intervertebral cartilages and the ligamenta subflava, it returns spontaneously to its natural curve of rest like an elastic bow. Its mobility is greatest in the cervical region, on account of the thick- ness of the fibro-cartilages, the small size of the vertebras, the oblique direction of their articulations, and, above all, the horizontal position and the shortness of their spines. In the dorsal region there is very little mobility, on account of the vertical direction of the articular processes, and the manner in which the arches and the spines overlap each other. In the lumbar region, the spine again becomes more moveable, on account of the thickness of the intervertebral cartilages, and the horizontal direction of the spinous processes. LIGAMENTS BE ^e occiput is connected to the atlas by the TWEEN THE Occipi- following ligaments : viz. two anterior occipito- TAL BONE AND atloid, a posterior occipito-atloid, two lateral THE ATLAS. occipito-atloid, and two capsular ligaments. The two anterior ligaments are composed of a superficial and a deep portion ; the superficial part is a strong rounded cord which passes from the basilar process above, to the tubercle on the ante- rior arch of the atlas below ; the deep portion is membranous, and passes from the anterior margin of the foramen magnum to the front arch of the atlas. The posterior ligament extends in a similar manner from the posterior border of the foramen magnum to the posterior arch of the atlas. It is thin, and superiorly becomes blended with the LIGAMENTS BETWEEN OCCIPITAL BONE AND AXIS. 299 dura mater, and is pierced by the vertebral artery and the sub- occipital nerve. The two lateral ligaments pass from the jugular eminences of the occiput, downwards and outwards to the transverse processes of the atlas. The capsular ligaments extend from the margin of the condyles of the occipital bone to the upper articular borders of the atlas. The movements which take place between the occipital bone and the atlas are flexion and extension, as in nodding forwards and backwards ; and lateral movement, as in inclining the head side- ways. FIG. 71. POST? COMMON LICT DIAGRAM OF THE ODONTOID AND TRANSVERSE LIGAMENTS. LIGAMENTS These are the most important ; and to see them, BETWEEN THE the spinal canal must be exposed by removing the OCCIPITAL BONE posterior arches of the upper cervical vertebrae, and AND THE AXIS. j.1 T i i i tne posterior common ligament, which is here very thick and strong. It ascends from the posterior surface of the axis, then passes over the odontoid and transverse ligaments, and is attached to the basilar process of the occipital bone. It is called the occipito-axial ligament, or the apparatus ligamentosus colli. ODONTOID OR The odontoid or check ligaments (fig. 71) are CHECK LIGAMENTS, two very strong ligaments, which proceed from the sides of the odontoid process to the tubercles on the inner 300 ATLO-AXIAL LIGAMENTS. sides of the condyles of the occiput. Their use is to limit the rotation of the head. A third or middle odontoid ligament passes from the apex of the odontoid process to the margin of the foramen magnum. It is sometimes called the ligamentum suspefoorium. ARTICULATION Tllis J oint forms a lateral ginglvmus or diar- BETWEEN THE throsis rotatoria, and is maintained by the follow- ATLAS AND THE ing ligaments : two anterior atlo-axial, a posterior atlo-axial, two capsular, and a transverse. The two anterior ligaments consist of a superficial and a deep portion : the superficial is a rounded ligament passing from the tubercle of the atlas to the base of the odontoid process ; the deep passes as a membranous layer from the anterior arch of the atlas to the body of the axis. The posterior ligament extends from the posterior arch of the atlas to the upper border of the lamina of the axis. The capsular ligaments are thin loose ligamentous sacs connect- ing the borders of the articular surfaces. The transverse ligament (fig. 71) passes transversely behind the odontoid process, and is attached to the tubercles on the inner sides of the articular processes of the atlas. From the centre of this ligament a few fibres pass upwards, to be attached to the basilar process, and some downwards to the body of the axis, giving it a cruciform appearance. Thus it forms with the atlas a ring, into which the odontoid process is received. If this transverse ligament be divided, we observe that the odontoid process is covered with cartilage in front and behind, and is provided with two synovial membranes. The ribs articulate by their heads with the bodies of the dorsal vertebrse ; by their necks and tubercles with the transverse pro- cesses of the vertebrae, and by their cartilages with the sternum in front. The head of each rib presents two articular sur- ARTICULATIONS . r OF THE HEADS OF faces, corresponding to the bodies of two vertebras. THE EIBS WITH There are two distinct articulations, each provided THE BODIES OF with a separate synovial membrane. The ligaments THE VERTEBRAE. are 1 . An anterior costo-central or stellate, which connects the front COSTO-VERTEBRAL LIGAMENTS. of the head of the rib with the sides of the bodies of two vertebra; and the intervening fibre-cartilage (fig. 72). It is composed of three fasciculi of fibres which radiate from the rib, one of which passes upwards to be attached to the body of the vertebra above ; the lower one passes to the body of the vertebra below ; while the intermediate one passes horizontally forwards to the intervertebral disc. In the three lower ribs the fasciculi are not separately distin- guishable, although the fibres pass upwards to the vertebree and downwards to the vertebra with which the rib articulates. Some anatomists describe a capsular ligament surrounding the articulation ; the fibres are very thin, and form part of the costo- central ligament. FIG. 72. 1, 1, 1. Superior costo- transverse ligaments. 2, 2, 2. Anterior costo-con- tral or stellate ligaments. COSTO-VEKTEBEAL LIGAMENTS. 2. An interarticular ligament which passes across the joint from the ridge on the head of the rib to the iutervertebral cartilage. It divides the articulation into two joints which do not communicate with each other. It is absent in the three lower articulations. The ligaments connecting these bones are the capsular, the anterior, middle and posterior costo- transverse. The capsular ligament surrounds the articular surfaces of the tubercle of the rib and the transverse process of its corresponding vertebra, and has a synovial membrane. It is absent in the eleventh and twelfth ribs. The anterior or superior costo-transverse ligament ascends from ABTICULATIONS OF THE NECK AND TUBERCLE OF THE KlBS WITH THE TRANSVERSE PRO- CESSES. 302 COSTO-STERNAL LIGAMENTS. the upper border of the neck of the rib to the lower border of the transverse process above it. It is continuous externally with the aponeurosis covering the external intercostal muscle. The first and twelfth ribs have no anterior costo-trans verse ligament (fig. 72). The middle costo-transverse ligament is an interosseous one, and connects the adjacent surfaces of the neck of the rib, and the trans- verse process. It is badly developed in the eleventh and twelfth ribs (fig. 73). The posterior costo-transverse ligament passes from the apex of the transverse process to the summit of the tubercle of the rib. It is wanting in the eleventh and twelfth ribs (fig. 73). FIG. 73. DIAGRAM SHOWING THE LIGAMENTS CONNECTING THE KIB WITH THE VERTEBRA. 1. The anterior costo-ccntral ligament. 2. The interosseous, or middle costo-transverse ligament. 3. The posterior costo-transverse ligament. 4. The synovial membrane between the rib and the body of the vertebra. CONNECTION BETWEEN THE CARTILAGES OF THE ElBS AND STERNUM. The anterior extremities of the ribs are concave, and receive the cartilages of the ribs ; this junction is maintained by the periosteum. The cartilages of all the true ribs are received into slight con- cavities on the side of the sternum, and are se- cured by anterior, posterior, upper, and lower ligaments. There is a synovial membrane between the cartilage of each rib and the sternum, except that of the first, and usually at each articulation the synovial membrane is separated into two by an interarticular ligament. The costal cartilages from the sixth to the tenth are connected by TEMPORO-MAXILLARY ARTICULATION. 303 ligamentous fibres. There are intercostal synovial membranes in front between the adjacent borders of the sixth, seventh, eighth, and ninth costal cartilages. MOVEMENTS OF The movements permitted between the heads of THE BIBS. the ribs and the bodies of the vertebrae are those of elevation and depression, and those of rotation forwards and backwards ; the centre of these movements being at the interarticu- lar ligament. Between the tubercles and the transverse processes there is the movement of an arthrodial nature ; and between the costal cartilages and the sternum, that of elevation and depression. The movement of the first rib is very slight ; that of the second is freer ; and mobility of the ribs gradually increases from above downwards. ARTICULATION The condyle of the lower jaw articulates with OF THE LOWER the glenoid cavity of the temporal bone, and forms JAW - an arthrodial joint. The joint is provided with an interarticular fibre-cartilage, with external and internal lateral and capsular ligaments, and two synovial membranes (fig, 74). The external lateral ligament extends from the zygoma and its tubercle ; its fibres pass downwards and backwards to the outer surface and posterior border of the neck of the jaw. The internal lateral ligament a long, thin, flat band extends from the spinous process of the sphenoid bone to the inner border of the dental foramen. The capsular ligament consists of a few scattered fibres attached above to the margin of the glenoid cavity, below to the neck of the jaw. The interarticular fibro-cartilage is a thin plate of an oval form, and thicker at the margin than at the centre. It is placed hori- zontally, and its upper surface is concavo-convex from before back- wards ; its lower surface is concave. It is connected on the outer side to the external lateral ligament, and on the inner side some of the fibres of the external pterygoid muscle are inserted into it. There are two synovial membranes an upper and a lower for the joint. The larger and looser of the two is situated between the glenoid cavity and the fibro-cartilage. The lower is interposed between the fibro-cartilage and the condyle of the jaw. They 304 TEMPORO-MAXILLARY ARTICULATION. sometimes communicate through a small aperture in the centre of the fibro-cartilage. The form of the articulation of the lower jaw admits of move- ment, upwards and downwards, forwards, backwards, and from side to side. A combination of these movements takes place in masti- cation : during this act the condyles of the jaw describe an oblique rotatory movement in the glenoid cavity. The purposes served by the fibro-cartilage in this joint are : first, it follows the condyle, FIG. 74. Section through the glenoid cavity Interarticular fibro-cartilage . . Internal lateral ligament . . . . _ TRANSVERSE SECTION TO SHOW THE LIGAMENTS AND THE FIBRO-CARTILAGE OF THE JOINT OF THE LOWER JAW. THE DOTTED LINES REPRESENT THE TWO SYNOVIAL MEMBRANES. and interposes a convenient socket for all its movements : second, being elastic, it breaks shocks ; for shocks here would be almost fatal, considering what a thin plate of bone the glenoid cavity is, and that just above it is the brain. Its nerves are derived from the auriculo-temporal, and the masseteric branches of the inferior maxillary. The stylo-hyoid and stylo-maxillary ligaments have been pre- viously described. 305 DISSECTION OF THE UPPER EXTREMITY. THE subject should be placed on its back, and, the thorax being raised by a block placed under the shoulders, the arm is to be ex- tended to a right angle with the trunk and slightly rotated out- wards. A narrow board must be placed under the arm to keep it in position, and the hand, with the palm upwards, is to be firmly encircled by string to the board. SURFACE Before commencing the dissection of the arm, MARKING. the student should carefully examine with the eye and the finger the various inequalities of the surface of the skin, which are caused by, or are landmarks of, important subjacent structures. Beginning in the middle line, we notice a broad shallow groove in front of the sternum between the sternal origins of the pectoralis major ; about two inches below the upper border of the sternum is a prominent transverse bony ridge (angulus sterni), which cor- responds to the junction of the first and second portions of the sternum. The clavicle may be easily traced, convex as to its sternal half, and concave in its outer half; not placed quite horizontally, but inclined upwards in the present position of the limb, and articula- ting externally with the prominent acromion process. Extending obliquely downwards and outwards, from the middle of the clavicle, is a groove, marking the separation between the contiguous borders of the deltoid and pectoralis major, and in which may, by deep pres- sure, be felt the coracoid process. Another groove, passing outwards from the sterno-clavicular joint, indicates the interval between the sternal and clavicular attachments of the pectoralis major. The upper arm below the acromion is rounded, the convexity being caused by the greater and lesser tuberosities of the humerus. In the more x 306 CUTANEOUS NERVES OF THE CHEST. common forms of dislocations of the humerus, this roundness is lost, and a depression takes its place. Between the thorax and the arm there is a deep hollow the axilla which varies according to the position of the arm to the side. Its front border is formed by the pectoralis major, and its hinder border by the latissinms dorsi ; and if the fingers be pushed up into this space, the head of the humerus can be easily felt. The free border of the pectoralis major muscle corresponds with the fifth rib, and below this can be distinguished the lower digitations of the serratus magnus with the external oblique. The student must now make three incisions through the skin : the first, along the middle of the whole length of the sternum ; the second, along the lower border of the clavicle, and down along the front of the upper arm for four inches ; the third, from the ensiform cartilage, backwards to the posterior border of the axilla. The skin should now be taken up with the forceps at the upper and inner angle, and when the skin has been so far reflected as to enable the fingers to take it up, lay aside the forceps and use the fingers in their place. The skin should be carefully dissected from the subjacent layer of subcutaneous fascia and fat. In doing so, notice the thin, pale fibres of the broad subcutaneous muscle of the neck platysma my aides (fig. 13). Beneath this subcutaneous fascia and fat there is the strong deep fascia which closely invests the muscles, and in the axilla it forms a dense fascia which passes from the pectoralis major to the latissimus dorsi. CUTANEOUS The numerous nerves which run through the NEKVES. subcutaneous tissue to the skin and mammary gland must be carefully dissected out. They are derived from various sources : some, branches of the superficial cervical plexus, descend over the clavicle ; others, branches of the intercostal nerves, come through the intercostal spaces close to the sternum, each with a small artery ; a third series, also branches of the intercostal nerves, come out on the side of the chest, and run forwards over the outer border of the pectoralis major. The supra-clavicular nerves, which arise from the third and CUTANEOUS NERVES OF THE CHEST. 307 fourth cervical nerves, descend over the clavicle, and are subdivided, according to their direction, into sternal, clavicular, and acromial branches (diagram, p. 66). The inner or sternal cross the inner end of the clavicle to supply the skin over the upper part of the sternum. The middle or clavicular pass over the middle of the cla- vicle, and supply the integument over the front of the chest and the mammary gland. The outer or acromial branches cross over the outer end of the clavicle, and distribute their filaments to the skin of the shoulder. Near the sternum are found the anterior cutaneous branches or terminal filaments of the intercostal nerves. After piercing the in- ternal intercostal and pectoralis major muscles, each nerve sends an inner filament to the skin over the sternum, and an outer larger one, which supplies the skin over the pectoral muscle. Those of the third and fourth intercostal supply also the mammary gland. Branches of the internal mammary artery, for the supply of the mammary gland, accompany these nerves. During lactation they increase in size, ramifying tortuously over the surface of the gland. They are occasionally as large as the radial at the wrist. The lateral cutaneous branches of the intercostal nerves come out between the digitations of the serratus magnus on the side of the chest, and divide into anterior and posterior branches. The anterior branches curve round the free border of the pectoralis major, and then supply the skin over that muscle and the mamma. The pos- terior branches supply the skin of the back of the chest. Dissect off the superficial fascia and fat with the DlSSFCTION mammary gland. Thus you will expose the strong deep fascia which is closely attached to the pectoralis major and deltoid muscles. It is continuous, above, with the fascia of the neck ; below, with that of the arm. At the axilla it becomes denser, where it passes from the pectoral to the latissimus dorsi muscles. Reflect this fascia from the pectoralis major by dissecting parallel with the course of its fibres. The muscle having been fully exposed, observe its shape, the course of its fibres, their origin and insertion. 1 1 Sometimes we find a thin little muscle running perpendicularly in front of the inner part of the pectoralis major. This is the rectus sternalis or sternalis 308 PECTORALIS MAJOR. PECTOKALIS The pectoralis major is the large triangular MAJOK. muscle in the front of the chest. It arises from the anterior surface of the sternal half of the clavicle, from the front of its own half of the sternum, from the cartilages of all the true ribs except the last, and from the aponeurosis of the external oblique muscle of the abdomen. From this extensive origin the fibres converge towards the arm, the upper ones passing downwards and outwards, the middle ones transversely outwards, and the lower fibres upwards and outwards ; they terminate in a flat tendon, about two inches in breadth, which is inserted into the anterior margin of the bicipital groove of the humerus. The arrangement of its fibres, as well as the structure of its tendon, is peculiar. The lower fibres, which form the boundary of the axilla, are folded be- neath the rest, and terminate upon the upper part of the tendon i.e. nearer to the shoulder-joint ; the upper fibres, which arise from the clavicle, and are frequently separated from the main body of the muscle by a slight interval, descend in front of the lower, and terminate upon the lower part of the tendon. Consequently the upper and lower fibres of the muscle cross each other previously to their insertion. The object of this arrangement is to enable all the fibres to act simultaneously when the arm is extended. The upper part of the tendon sends off a fibrous prolongation, which binds down the long head of the biceps, and is attached to the great tuberosity of the humerus ; another tendinous expansion is prolonged backwards to the tendon of the deltoid muscle ; and a third passes downwards to be intimately connected with the fascia of the upper arm. The chief action of the pectoralis major is to draw the humerus towards the chest, as in placing the hand on the opposite shoulder, or in pulling an object towards the body. When the arm is raised and made the fixed point, the muscle assists in raising the trunk, as in climbing. Thus too, on emergency, it can act as an auxiliary muscle of inspiration. Between the pectoralis major and the deltoid, the great muscle- brutorum. It arises inferiorly by a tendinous expansion from the reotus ab- dominis, and is connected above to the tendon of the sterno-mastoid. INFRA- CLAVICULAR REGION. 309 covering the shoulder, is an interval varying in extent in different subjects, but always more marked towards the clavicle. It contains a small artery the thoracica humeraria and the cephalic vein, which ascends on the outer side of the arm, and empties itself into the axillary. This interval is the proper place to feel for the cora- coid process. In doubtful injuries about the shoulder, this point of bone is a good landmark in helping the surgeon to arrive at a correct diagnosis. The pectoralis major is supplied with nerves by the anterior thoracic branches of the brachial plexus ; with blood, by the long and short thoracic branches of the axillary artery. DISSECTION Reflect the clavicular part of the pectoralis ANATOMY OP THE major by detaching it from the clavicle, and turn INFKA-CLAVICULAR it downwards ; in doing so, notice a small nerve, EEGION. ^ external anterior thoracic, which enters the under surface of this part of the muscle. Beneath the portion thus reflected, part of the pectoralis minor will be exposed. In this triangle bounded, above, by the clavicle ; below, by the upper border of the sternal origin of the pectoralis major ; and, on the outer side, by the deltoid is an important space in which the relative position of the following objects must be carefully ex- amined : COSTO-COBACOID A strong ligamentous expansion, called the MEMBRANE. costo-coracoid membrane, extends from the car- tilage of the first rib to the coracoid process. Between these points it is attached to the clavicle, and forms a complete investment for the subclavius muscle. Its lower crescent-shaped edge arches over, and protects the axillary vessels and nerves ; from this edge is prolonged downwards a funnel-shaped fascia, which covers the axillary vessels, forming the anterior portion of their sheath ; the posterior being formed by a prolongation of the deep cervical fascia. The front portion of this sheath is perforated by the cephalic vein, the thoracica acromialis artery and vein, the ante- rior thoracic nerves, and the superior thoracic artery. This fascia must be removed. b. The subclavius muscle enclosed in its fibrous sheath. c. The axillary vein, artery, and brachial plexus of nerves. 810 INFRA-CLAVICULAR REGION. d. Two arteries, the superior or short thoracic and the thoracica acromialis. e. The termination of the cephalic vein in the axillary. /. Two nerves, the anterior thoracic, which descend from the brachial plexus below the clavicle, and cross in front of the axillary vessels to supply the pectoral muscles. This muscle lies between the clavicle and the first rib. It arises from the first rib by a short round tendon at the junction of the bone and cartilage in front of the costo- clavicular ligament, and is inserted into the groove on the under surface of the clavicle as far outwards as the coraco- clavicular ligament. Its nerve comes from the fifth and sixth cervical nerves. Its action is to depress the clavicle, and prevent its too great elevation. EELAT E POSI ^ n ^ e infra-clavicular space before us are the TION OF THE AXIL- great vessels and nerves of the axilla in the first LAKY VESSELS AND p ar t o f their course. They lie at a great depth from the surface. They are surrounded by a sheath of fascia, which descends with them beneath the clavicle. Their relations with regard to each other are as follows : The axillary vein lies in front of the artery, and rather to its thoracic side. The brachial plexus of nerves is situated above the artery, and on a posterior plane. The plexus consists of two, or some- times three, large cords, which result from the union of the anterior branches of the four lower cervical, and the first dorsal , nerves. The course 'and relations of the axillary artery will be examined subsequently. SUPERIOR These are two branches which arise from the THORACIC AND axillary artery in the first part of its course, above ACROMIO-THORACIC the pectoralis minor. The superior thoracic fre- ARTERIES. quently arises in common with the acromio-thoracic, and passing along the upper border of the pectoralis minor, descends between this muscle and the pectoralis major, supplying both and ana- stomosing with the intercostal and internal mammary arteries. The thoracica acromialis is given off just above the pectoralis minor, and shortly divides into three sets of branches : viz. two or three small thoracic branches to the serratus magnus and pectoral muscles ; the thoracica Jmmeraria, which descends with the cephalic vein, in the INFRA-CLAVICULAR REGION. 311 interval between the pectoralis major and deltoid, and ramifies in both ; and, lastly, the acromial branch, which passes over the coracoid process to the under surface of the deltoid, which it supplies, and communicates with the posterior circumflex, a branch of the axillary, and the supra- scapular, a branch of the subclavian. A constant though small branch, the clavicular, runs along the anterior aspect of the subclavius. All these arteries are accompanied by veins, which most frequently empty themselves into the cephalic, but occasionally into the axillary vein. The cephalic vein is one of the principal cuta- CEPHALIC VEIN. . , , ^ . , , neous veins of the arm. Commencing on the back of the thumb and forefinger, it runs up the radial side of the forearm, in front of the elbow-joint ; thence ascending along the outer edge of the biceps, it runs up the interval between the pec- toralis major and deltoid, pierces the costo-coracoid membrane, crosses over the axillary artery, and finally empties itself into the axillary vein. 1 ANTERIOR THO- These nerves come from the brachial plexus RACIC NERVES. below the clavicle to supply the pectoral muscles. There are generally two an external and an internal one for each pectoral muscle. The external, the more superficial, arises from the outer cord of the brachial plexus, passes over the axillary artery and vein, pierces the costo-coracoid membrane, and supplies the pectoralis major on its under aspect : it communicates with the next nerve by a filament which forms a loop on the inner side of the artery ; the internal, and smaller branch, comes from the internal cord, and descends between the axillary artery and vein (occasionally through the vein) to supply the pectoralis minor on its under surface. DIFFICULTY OF From this view of the relations of the axillary TYING THE FIRST artery in the first part of its course, some idea PABT OF THE AXIL- ma y \)Q fo rm ed of the difficulty of passing a ligature round it in this situation. In addition to its great depth from the surface, varieties sometimes occur in the position of the nerves and veins, which render the operation still 1 The cephalic vein, in some cases, runs over the clavicle to join the external jugular ; or there may be a communication (termed jugulo-cephalic) between these veins. 312 DISSECTION OF THE AXILLA. more embarrassing. For instance, the anterior thoracic nerves may be more numerous than usual, and form by their mutual communication a plexus around the artery. A large nerve is often seen crossing obliquely over the artery, immediately below the clavicle, to form one of the roots of the median nerve. The cephalic vein may ascend higher than usual, and open into the subclavian ; and as it receives large veins corresponding to the thoracic axis, a concourse of veins would be met with in front of the artery. Again, it is by no means uncommon to find a deep- seated vein, the supra-scapular, crossing over the artery to join the axillary vein. DISSECTION OF THE AXILLA. SEBACEOUS On the under surface of the skin of the axilla, GLANDS. near the roots of the hairs, are numerous sebaceous glands. They are of a reddish-brown colour, and rather larger than a pin's head. AXTLLABY This dense fascia, which lies immediately be- FASCIA. neath the skin of the axilla, is a continuation of the general fascia! investment of the muscles. It closes in and forms the floor of the cavity of the axilla. Externally, it is strengthened by fibres from the tendons of the pectoralis major and latissimus dorsi, and is continuous with the fascia of the arm ; internally, it is prolonged on the side of the chest, over the serratus magnus muscle ; in front and behind, it divides, so as to enclose between its layers the muscles which form the boundaries of the axilla. Thus the anterior layer encloses the two pectoral muscles, and is connected with the coracoid process, the costo-coracoid ligament, and the clavicle ; the posterior layer encloses the latis- simus dorsi, and passes backwards to the spine. A subcutaneous artery, sometimes of considerable size, is often found in the substance of the axillary fascia. It generally arises from the brachial, or from the lower part of the axillary artery, and runs across the floor of the axilla towards the lower edge of the pecto- -ralis major. It is not a named branch, but should be remembered, BOUNDARIES OF THE AXILLA. 313 as it would occasion much, haemorrhage if wounded in opening an abscess. DISSECTION AND Reflect the axillary fascia, to display the CONTENTS OF THE boundaries and the contents of the axilla. The AXILLA. dissection of this space is difficult, and must be done cautiously. Bear in mind that the trunk blood-vessels and nerves run through the upper and outer part of the axilla ; that the long thoracic artery runs along the anterior border, and the subscapular artery along the posterior. Commence dissecting, therefore, in the middle; break down with the handle of the scalpel the loose connective tissue, fat, and lymphatic glands, which occupy the cavity. You will soon discover some cutaneous nerves coming out between the ribs, and then crossing the axillary space. These nerves are the posterior lateral cutaneous brandies of the intercostal nerves ; they perforate the intercostal spaces be- tween the digitations of the serratus magnus, midway between the sternum and the spine, and divide into anterior and posterior branches. The anterior turn over the pectoralis major, to supply the skin on the front of the chest and the mammary gland. The posterior pass backwards over the latissimus dorsi, and are distri- buted to the skin covering this muscle and the scapula. INTEECOSTO- The posterior lateral branch of the second inter- HUMERAL NEBVES. costal nerve requires a special description. It is larger than the others, and is called the intercosto-lmmeral because it supplies the integuments of the arm. It comes through the second intercostal space, traverses the upper part of the axilla, where it receives a branch of the lesser internal cutaneous nerve (nerve of Wrisberg), and, piercing the fascia, terminates in fila- ments, which are distributed to the skin on the inner side and back of the arm, as low as the internal condyle. The correspond- ing branch of the third intercostal is also an intercosto-lmmeral nerve. It receives a branch from the second, and runs a similar course. The distribution of these nerves accounts for the pain down the arm which is sometimes experienced in pleurisy. BOUNDABIES OF The axilla is a conical space, of which the apex. THE AXILLA. i s beneath the clavicle, and the base between the pectoralis major and the latissimus dorsi. Obviously it varies in ./ 314 PECTORALIS MINOR. capacity according to the position of the arm to the side. On the inner side, it is bounded by the four upper ribs, with their corre- sponding intercostal muscles and the serratus magnus ; on the outer, by the humerus, covered by the coraco-brachialis and biceps ; in front, by the pectoral is major and minor ; behind, by the latis- simus dorsi, teres major, and subscapularis. Its anterior and posterior boundaries converge from the chest, so that the axilla becomes narrower towards the arm. With a full view of the axilla before you, bear in mind that pus may burrow under the pectoral muscles, or under the scapula, or that it may run up beneath the clavicle and point in the neck, if the abscess be allowed to remain unopened. AXILLARY LYMPH- The axillary glands form a continuous chain, ATIC GLANDS. beneath the clavicle, with the cervical glands. They are from ten to twelve in number, of a reddish-brown colour, and variable size. Most of them lie near the axillary vessels ; others are embedded in the loose tissue of the axilla ; sometimes one or two small ones are observed along the lower border of the pectoralis major. They are supplied with blood by a branch thoracica alaris of the axillary artery, and by branches from the thoracic and subscapular arteries. These glands receive the lymphatics from the arm, from the front and side of the chest, and from the outer half of the mam- mary gland. It is these glands which frequently become enlarged in cancer of the mammary gland. From these glands the efferent lymphatics pass along with the subclavir.n artery and terminate, on the right side, in the right lymphatic duct ; and, on the left side, in the thoracic duct. Now cut through the pectoralis maior, about DISSECTION. A the middle, and turn the inner part of the muscle towards the sternum, and the outer part towards the arm. The pectoralis minor is thus exposed, together with the ramifications of the short and long thoracic arteries. Preserve the arteries, as far as possible, in connection with the main trunks. PECTOBALIS This triangular muscle arises from the third, MINOK. fourth, and fifth ribs, near the costal cartilages, and from the thick fascia over the intercostal spaces. The fibres AXILLARY ARTERY. 315 run obliquely upwards and outwards, and converge to a strong tendon, which is inserted into the anterior surface of the coracoid process. The tendon is connected to that of the coraco-brachialis and biceps by a strong fascia, which forms a protection for the subjacent axillary vessels and nerves. The action of this muscle is to draw the scapula downwards and forwards. Its nerve is derived from the internal anterior thoracic. Having examined the muscles which form the anterior boundary of the axilla, we pass now to the course and relations of the axillary artery and its branches. To have a clear view, reflect the subclavius from its insertion, and cut the pectoralis minor through its middle. AXILLABY AR- This artery, the continuation of the subclavian, TERY, ITS COURSE takes the name of axillary at the outer border of AND RELATIONS. ^g g rs ^ j-j^ j^ then passes downwards and out- wards, through the upper part of the axilla, beneath the two pec- toral muscles, and along the inner border of the coraco-brachialis, as far as the lower border of the tendon of the teres major, beyond which it is continued under the name of the brachial. Its course is divided for convenience of description into three parts : the first lies above the pectoralis minor ; the second behind that muscle ; and the third below it. In the first part of its course, the artery is covered by the pec- toralis major and the costo-coracoid membrane, the subclavius, and is crossed by the cephalic and acromio-thoracic veins. On its inner side, and slightly in front, is the axillary vein ; on its outer side is the brachial plexus of nerves ; behind it, are the first intercostal space, the second digitation of the serratus magnus, and the pos- terior thoracic nerve (external respiratory of Bell). In the second part of its course, it lies behind the pectoralis major and minor; on its inner side is the axillary vein, still slightly anterior, but separated from the artery by the inner cord of the brachial plexus ; on its outer side is the outer cord of the brachial plexus ; and behind it, is the posterior cord of the plexus, and also a quantity of loose connective tissue which separates it from the subscapularis muscle. The inner head of the median nerve is often in front of the artery in this part of its course. 316 AXILLARY ARTERY. In the third part, in front of the artery, are the pectoralis major, the two roots of the median nerve, converging like the letter V ; and lower down is the skin and the fascia of the arm ; on the outer FIG. 75. DIAGRAM OF AXILLA. 1. Axillary artery. 8. Superior prof unda a. 2. Brachial artery. 9. Posterior thoracic nerve. 3. Thoracica humeraria a. 10. Long subscapular n. 4. Superior thoracic a. 11. Median n. 5. Subscapular a. 12. Cephalic vein. 6. Dorsalis scapulae a. 13. Muscujp-cutaueous n. 7. Posterior circumflex a. 14. Teres major. side are the coraco-brachialis, the musculo-cutaneous and median nerves ; on the inner side are the axillary vein, the ulnar, and the BRANCHES OF THE AXILLARY ARTERY. 317 two internal cutaneous nerves ; behind it are, in succession, the subscapularis, the latissimus dorsi, the teres major, and the musculo-spiral and circumflex nerves. BRANCHES OF The number and origin of these branches often THE AXILLARY vary, but their general course is in most cases ARTERY. similar, and they usually arise in the following order : a. The superior thoracic arises above the pectoralis minor, and divides into branches, which have been already described (p. 310). b. The acromial thoracic also arises above the pectoralis minor, and gives off numerous branches already described (p. 310). c. The alar thoracic, variable in its origin, supplies the lymphatic glands and the connective tissue of the axilla. PLAN OF THE BRANCHES OF THE AXILLARY ARTERY. 1. Thoracic axis, giving off 2. Short thoracic. 3. Thoracica acromialis. 4. Thoracica humeraria. 5. Long thoracic. 6. Subscapular. 7. Dorsalis scapula?. 8. Anterior circumflex. 9. Posterior circumflex. d. The inferior or long thoracic artery (external mammary) runs along the lower border of the pectoralis minor to the side of the chest. It supplies the mammary gland, the serratus maggus and pectoral muscles, and maintains a free anastomosis with the short thoracic, internal mammary, and intercostal arteries. e. The subscapular is the largest branch of the axillary it arises opposite the lower border of the subscapularis, and, after running a short' course of about an inch and a half, divides into an anterior and posterior branch. The anterior branch runs along the anterior edge of the subscapu- 318 BRANCHES OF THE AXILLARY ARTERY. laris towards the lower angle of the scapula. Its numerous branches supply the subscapularis, latissimus clorsi, serratus magnus, and teres major, and anastomose with the intercostal and thoracic arteries, and with the posterior scapular (a branch of the subclavian). The posterior branch (dorsalis scapulae) runs to the back of the scapula, through a triangular space, bounded in front by the long head of the triceps; below, by the teres major ; and, above, by the subscapu- laris and teres minor (diagram, p. 318). It gives off a small branch which enters the subscapular fossa beneath the subscapularis, supplying it, and anastomosing with the suprascapular and posterior scapular arteries. On the back of the scapula it divides into two branches : one FIG. 77. 1. Subscapularis. 2. Teres major. 3. Long head of triceps. 4. Square space for post. circumflex a. and n. 5. Triangular space for dor- salis scapulas a. 6. Space for musculo-spiral n., and superior pro- funda a. DIAGRAM OF THE ORIGINS OF THE TRICEPS. runs in the groove on the axillary border of the scapula, lying beneath the teres minor, and ramifies in the infraspinous fossa between the bone and the infraspinatus ; the other runs down between the teres minor and major on their dorsal aspects, and passes to the inferior angle of the scapula, anastomosing with the posterior and suprascapular arteries. The subscapular vein empties itself into the axillary vein. f. The posterior circumflex artery arises from the back of the axillary artery, and is as large as the subscapular, close to which it is given off ] or both may arise by a common trunk from the axillary. It passes backwards, with its corresponding veins and nerve, through a quadri- lateral space, bounded above by the subscapularis and teres minor, below by the teres major, externally by the neck of the humerus, and BRACHIAL PLEXUS OF NERVES. 319 internally by the long head of the triceps (fig. 77). It then winds round the back of the neck of the humerus, and is chiefly distributed to the under surface of the deltoid. Besides the deltoid, the posterior circumflex artery supplies the long head of the triceps, the head of the humerus, and the shoulder- joint. It inosculates above with the acromio- thoracic and suprascapular arteries, below with the ascending branch of the superior profunda (a branch of the brachial), and in front with the anterior circumflex artery. Should you not find the posterior circumflex artery in its normal position, look for it (as a branch of the brachial) below the tendon of the teres major. g. The anterior circumflex artery, much smaller than the posterior, runs in front of the neck of the humerus, above the tendon of the latissimus dorsi. It passes directly outwards beneath the coraco- brachialis and short head of the biceps, close to the bone, and terminates in the under surface of the deltoid, where it inosculates with the posterior circumflex. The anterior circumflex artery sends a small branch which runs with the long tendon of the biceps up the groove of the humerus, and is called, on that account, the bicipital artery. It supplies the shoulder- joint and the neck of the humerus. If the axillary were tied below the pectoralis minor, the colla- teral circulation would be established by the suprascapular, and its branches anastomosing with the subscapular, the dorsalis scapulae, and the posterior circumflex ; the posterior scapular with the dor- salis scapulas and subscapular arteries. 1 The axillary vein is formed by the continuation upwards of the basilic vein, and extends from the lower border of the teres major to the outer border of the first rib. It receives the venae comites of the brachial artery near the lower border of the subscapularis. It receives the subscapular and the other veins corresponding to the branches of the axillary artery, with the exception of the circumflex, which usually join either the subscapular or one of the venae comites. The axillary near its termination also receives the cephalic vein. 1 The axillary artery varies much as to the branches it gives off : occasionally (1 in 33) it gives off the radial artery ; more rarely (1 in 72) it gives off the ulnar ; and more rarely still (1 in 506) it gives off the interosseous artery. BRACHIAL PLEXUS OF NERVES. The axillary vein in the upper part of its course lies in front of the artery, and close to its sternal side ; in the lower two-thirds of its course, the vein lies still to the sternal side of the artery, but is separated from it by some of the nerves of the brachial plexus. AXILLARY OR This plexus is formed by the anterior trunks of BRACHIAL PLEXUS the four lower cervical and first*dorsal nerves, and receives also a small communicating branch from FIG. 78. OF NERVES. THE BRACHIAL PLEXUS OF NERVES. c 4-8. The five lower cervical nerves. D 1. The first dorsal nerve. 9. The rhomboid nerve to rhomboidei major and minor. 10. The supra-scapular nerve to supra and infra spinati. 11. The nerve to the subclavius. 12. Outer anterior thoracic nerve to pectoralis major. 13. Inner anterior thoracic nerve to pectoralis minor. 14, 15, 16. The sutscapular nerves to subscapu- laris, latissimus clorsi, and teres major. 17. Lesser internal cuianeous nerve. 18. Musculo-cutaneous nerve. 19. Musculo- spiral nerve. 20. Median nerve. 21. Circumflex nerve to deltoid and teres minor. 22. Ulnar nerve. 23. Internal cutaneous nerve. 24. External respiratory nerve of Bell, or posterior thoracic. the fourth cervical nerve. The plexus is broad at the lower part of the neck, where it emerges between the anterior and middle scalene muscles ; but it gradually contracts as it descends beneath BRACHIAL PLEXUS OF NERVES. 321 the clavicle into the axilla, and on a level with the coracoid process distributes its large branches to the upper limb. The arrangement of the cervical nerves in the formation of the plexus is variable, often not alike on both sides. 1 The most fre- quent disposition is this the fifth and sixth cervical unite at the outer border of the scalenus medius to form an upper cord ; the eighth and the first dorsal form between the scaleni muscles a lower cord ; the seventh cervical runs alone, as a middle cord, for a short distance. Each of these nerves divides, just external to the outer border of the scalenus medius, into an anterior and a posterior branch ; the anterior branches given oif from the fifth, sixth, and seventh cervical form the outer cord of the plexus ; the anterior branches given off from the eighth cervical and the first dorsal form the inner cord ; while the posterior branches of all the nerves viz., the fifth, sixth, seventh, eighth cervical, and the first dorsal unite to form the posterior cord. At first these cords are placed on the outer side of the axillary artery, but behind the pectoralis minor they are situated one on the outer side of, one on the inner side of, and one behind, the axillary artery. The brachial plexus gives off some branches above the clavicle, which were dissected with the neck (p. 125). Below the clavicle, it gives off the following : From the outer cord proceed an anterior thoracic branch, the musculo-cutaneous, and the outer head of the median ; from the inner cord proceed the inner anterior thoracic nerve, the inner head of the median, the ulnar, the internal cutaneous, and the lesser internal cutaneous ; from the posterior cord proceed the three subscapular nerves, the circumflex, and the musculo-spiral. The anterior thoracic nerves have been described (p. 311). SUBSCAPULAR The three subscapular nerves are found on the NEKVES. surface of the subscapularis. They come from the posterior cord of the brachial plexus, and supply, respectively, the latissimus dorsi, teres major, and subscapularis. The nerve to the latissiinus dorsi (long subscapular nerve) runs with the anterior 1 Frequently the second dorsal nerve sends upwards a communicating filament to the first dorsal nerve. (Journal of Anatomy, vol. xi. p. 539.) 322 LATISSIMUS DORSI. branch of the subscapular artery to the lower border and inner surface of the muscle. The nerve to the teres major is either a branch of the preceding, or comes separately from the posterior cord. It lies nearer to the hunierus than the long subscapular. It gives off also a small branch to the anterior border of the subscapularis. The nerve to the subscapulans arises from the posterior cord, higher than the others, and enters the muscle not far from its upper border in company with a small artery. CIRCUMFLEX The circumflex nerve accompanies the posterior NERVE. . circumflex artery. This large nerve comes from the posterior cord, and, after giving 1 a small filament to the shoulder- joint, passes, with its companion artery, through the quadrilateral space (p. 318) to the under surface of the deltoid. Here the nerve divides into an upper and a lower branch. The upper supplies the anterior part of the deltoid and the skin over it ; the lower supplies the back part of the deltoid, and gives the nerve to the teres minor, 1 upon which nerve sometimes a little gangliform swelling can be seen : it enters the under- aspect of the middle of this muscle. After furnishing these muscular branches, the nerve turns round the posterior border of the deltoid,, and diverges in filaments which supply the skin over the back of this muscle and over the long head of the triceps. LATISSIMUS This broad, flat muscle forms the posterior mar- DORSI. gin of the axilla. It arises from the external lip of the crest of the ilium, from an aponeurosis attached to the spinous processes of the six lower dorsal, of all the lumbar, and of the sacral vertebrae and their supraspinous ligament, and by fleshy digitations from the three or four lower ribs, interdigitating with those of the external oblique ; in some cases, as it passes over the inferior angle of the scapula, it has an additional origin from the angle. Its fibres converge from this large origin, and the muscle is inserted into the bottom of the bicipital groove of the humerus by a broad flat tendon, which curves round the lower border of the teres major. The axillary vessels and nerves lie upon the tendon close to its in- 1 This branch to the teres minor is said to be constant in all mammalia that have been examined in reference to this point. MUSCLES ATTACHED TO THE SCAPULA. 323 sertion. Its nerve is the long subscapular branch from the poste- rior cord of the brachial plexus, and it enters the muscle close to its anterior border, in company with a large branch of the subscapular artery. This muscle lies behind, and to the inner side of the latissimus dorsi, is closely connected with it, and assists in forming the posterior boundary of the axilla. It arises from the oval surface on the dorsal aspect of the lower angle of the scapula, and from the fibrous septa between it and the teres minor and infraspinatus, and is inserted by a broad flat tendon, about two inches in length, behind the latissimus dorsi, into the posterior margin of the bicipital groove of the humerus. The tendon extends below that of the latissimus dorsi, and a bursa or sac, lubricated with serum, intervenes between the two tendons. The action of this and the preceding muscle is to draw the humerus inwards and backwards. Its nerve is the middle subscapular, and lies along the dorsalis scapulae artery. This muscle arises from the posterior two-thirds of the subscapular fossa of the scapula, with the exception of the angles, neck, and the posterior border, and from the intermuscular septa attached to the bony ridges. Its fibres converge to a strong tendon, which passes under the axillary vessels and nerves, over the inner side of the shoulder-joint, and is inserted into the lesser tuberosity of the humerus, and into the neck of the humerus for an inch below it. The tendon of the muscle is intimately connected with the capsular ligament of the shoulder-joint, and between the base of the coracoid process and the tendon is a bursa, which communicates with the joint. Its action is to rotate the humerus inwards, and when the arm is raised to draw it to the side. Its nerves come from the upper and middle subscapular nerves. SEEKATUS This muscle covers the side of the chest like a MAGNUS. girth. It arises from the front of the outer surfaces of the eight upper ribs by nine slips or digitations, the second rib having two. Its fibres converge, and are inserted into the posterior border of the scapula in the following manner : the first two digitations are attached into the upper angle of the Y 2 324 DISSECTION OF THE UPPER ARM. scapula ; the third and fourth digitations along nearly the whole length of the posterior border ; the remainder are inserted into the inferior angle. Its action is to draw the scapula forwards ; but of this more hereafter. It is supplied by the following nerve, which is seen on its outer surface. POSTERIOR THO- ^ n ^ s nerve supplies the serratus magnus only. EACIC OK EXTEE- It comes from the fifth and sixth cervical nerves ; NAL BESPIRATORY a nd, after passing through the scalenus medius, NEBVE OF BELL. rnng 1^^ the axillary vessels, along the outer surface of the serratus magnus, each digitation receiving a sepa- rate filament. 1 DISSECTION OP THE UPPEK ARM. SURFACE In front of the upper arm may be distinguished MAEKING. the long prominence of the biceps muscle, and lower down at the bend of the elbow its tendon may be easily felt. The bend of the elbow, in muscular subjects, presents a triangular depression, with its boundaries formed on the inner side by the pronator teres, and on the outer side by the supinator longus. Superficially in this space the subcutaneous veins can be recog- nised, of which a fuller description will be entered into later on. On the inner side of the elbow, the internal condyle of the humerus is very prominent, and behind this, is the olecranon ; between these is a hollow in which may be felt the ulnar nerve. The olecranon is situated nearer the internal than the external condyle, which is visible on the outer side ; below this, is a dimple which corresponds with the head of the radius. Continue the incision down the inner side of the arm as far as two inches below the elbow, and then make a transverse incision from the inner to the outer side of the forearm. Reflect the skin, and trace out the cutaneous nerves, and the numerous veins in front of the elbow. 1 It may be asked why this nerve is called the external respiratory. It was so named by Sir C. Bell, who considered the serratus magnus as the external respira- tory muscle, co-operating with the diaphragm or internal respiratory muscle. CUTANEOUS NERVES OF THE ARM. 325 CUTANEOUS NERVES. On the inner side of the arm are the intercosto- humeral, the internal cutaneous branch of the musculo-spiral, the internal cutaneous, and the lesser internal cutaneous (nerve of Wrisberg) nerves ; on the outer side are the cutaneous branches of the circumflex, the external cutaneous FIG. 79. 1. Acromial branches Vperfi 2. Clavicular vica branches J of the su- perficial cer- 1 plexus. 3. Cutaneous branches of the circumflex nerve. 4. Branches of the internal cutaneous nerve. 5. External cutaneous branch of the mus- culo-spiral nerve. 6. Internal cutaneous nerve. 7. Its posterior cutaneous branch. 8. The cutaneous branch of the mnsculo-cutaneous nerve. DISTRIBUTION OF CUTANEOUS NERVES TO THE FRONT OF THE SHOULDER AND ARM. branches of the musculo-spiral, and lower down is the musculo- cutaneous nerve. The filaments of the intercosto-Jmmeral nerves (p. 313) descend along the inner and posterior part of the arm as far as the olecranon, and communicate with the internal cutaneous branch of the musculo-spiral nerve. The internal cutaneous nerve perforates the fascia, with the basilic vein about the middle of the arm, and divides into an anterior and a 326 CUTANEOUS NERVES OF THE ARM. posterior branch ; the anterior passes down in front of the arm (as a rule beneath the median basilic vein), and supplies the skin as far as the wrist, communicating with a cutaneous branch of the ulnar nerve ; the posterior winds round to the back of the forearm behind the internal condyle as far as the wrist, and communicates above the elbow with the nerve of Wrisberg, and above the wrist with the dorsal branch of the ulnar nerve. The lesser internal cutaneous (nerve of Wrisberg) perforates the FIG. 80. Basilic vein . . . . IK I lp Cephalic vein. Median basilic vein . . -H/fSf-' X^C^BL Median cephalic vein. Deep median vein . _ Median vein. SUPERFICIAL VEINS AND NEKVES AT THE END OF THE LEFT ELBOW. fascia about the lower third of the arm, and supplies the skin over the internal condyle and the olecranon. This nerve, as it lies close to the axillary vein, communicates with the first or second intercosto-humeral nerve. The internal cutaneous branch of the rmisculo- spiral nerve pierces the fascia, and supplies the skin of the inner and posterior aspect of the middle of the arm as far as the olecranon. The c^ltaneous branches of the circ^^.mflex nerve pierce the fascia over VEINS IN FRONT OF THE ELBOW. 327 the insertion of the deltoid, and supply the skin of the upper half of the arm on its outer side. The external cutaneous branches of the musculo- spiral nerve are two in number : the upper and smaller accompanies the cephalic vein in the lower half of the arm ; the lower may be traced down the outer and back part of the forearm nearly as far as the wrist, where it joins the posterior branch of the musculo-cutaneous nerve. On the outer side of the tendon of the biceps, the cutaneous branch of the musculo-cutaneous nerve perforates the fascia, and divides into many filaments, which supply the skin of the outer part of the fore- arm. DISPOSITION or Attention should now be directed to the dis- VKINS IN FKONT OF position of the veins in front of the elbow. In THE ELBOW. cleaning these veins, take care not to divide the branches of the internal and external cutaneous nerves which pass over and under them. The following is the ordinary -arrangement of the superficial veins at the bend of the elbow (fig. 80). On the outer side is the radial ; on the inner side is the ulnar vein, formed by the junction of the anterior and posterior ulnar cutaneous veins ; in the centre is the median, which divides into two branches, the external of which, uniting with the radial to form the cephalic vein, is called the median cephalic ; the internal, uniting with the ulnar to form the basilic, is named the median basilic. Near its bifur- cation, the median vein communicates by a branch (mediana pro- funda) with the deep veins which accompany the arteries of the forearm. Trace the cephalic vein up the arm. It runs along the outer border of the biceps to the groove between the pectoralis major and the deltoid, and dipping down between these two muscles, terminates in the axillary vein immediately above the pectoralis minor. The basilic vein, the largest of the veins of the upper arm, ascends along the inner side of the arm with the internal cutaneous nerve. Near the middle of the arm, it perforates the fascia, and empties itself either into the internal vena comes of the brachia. artery, or into the axillary vein. 328 MyscuLAR FASCIA OF THE ARM. RELATION OF ^ ne principal branches of the cutaneous nerves THE CUTANEOUS pass beneath the veins : that is to say, as a rule, NEKVES AND VEINS the internal cutaneous passes behind the median basilic vein, and the external cutaneous behind the median cephalic : but it should be remembered that many small filaments cross in front which are exposed to injury in venesection. EELATION OF Since the median basilic vein is larger than the MEDIAN BASILIC median cephalic, and, on account of the strong VEIN TO BKA- fascia beneath, more easily compressible, it is usually chosen for venesection; its position, there- fore, in reference to the brachial artery, becomes important. The vein is only separated from the artery by the semilunar fascia, derived from the tendon of the biceps. This fascia is in some subjects remarkably thin. Sometimes the artery lies above the fascia, in contact with the vein. In choosing, therefore, this vein for venesection, there is a risk of wounding the artery ; hence the practical rule, to bleed either from the median cephalic, or from the median basilic above the situation where it crosses the brachial artery. LYMPHATIC Immediately above the internal condyle, in the GLANDS. neighbourhood of the basilic vein, we find one or two small lymphatic glands. Others may be found higher up along the inner side of the arm. A gland is occasionally met with at the bend of the elbow ; but never below this joint. These little glands are the first which are liable to become tender and enlarged after a poisoned wound of the hand. MUSCULAR The fascia which invests the muscles of the FASCIA AND ITS upper arm is a continuation of the fascia of the CONNECTIONS. trunk and the axilla. This membrane varies in density: thus it is thin over the biceps, stronger on the inner side of the arm, to protect the brachial vessels and nerves, and strongest over the triceps. At the upper part of the arm it is connected with the coracoid process and the clavicle ; it is strengthened at the axilla by an expansion from the tendons of the pectoralis major and latissimus dorsi ; posteriorly, it is attached to the spine of the scapula. The fascia surrounds the brachial vessels with a THE BICEPS. 329 sheath, and furnishes partitions which separate the muscles from each other. Of these partitions, the most marked are, the external and internal intermuscular septa, which divide the muscles on the anterior from those on the posterior surface of the upper arm. These septa are attached to the condyloid ridges of the humerus and to the condyles. The internal intermuscular septum, the stronger of the two, begins at the insertion of the teres major, and is connected with tendinous insertion of the coraco-brachialis ; it separates the triceps extensor from the brachialis anticus, to both of which it affords attachment to their muscular fibres. It is pierced by the ulnar nerve and the inferior profunda and anastomotic arteries. The external intermuscular septum commences from the insertion of the deltoid, and separates the brachialis anticus, the supinator longus, and the extensor carpi radiali& longior in front, from the triceps extensor behind, to all of which muscles it affords attachment. It is pierced by the musculo-spiral nerve and the superior profunda artery. At the lower part of the upper arm, the fascia is remarkably strong, especially where it covers the brachialis anticus, and the brachial vessels, and is continued over the muscles on the inner side of the forearm. At the back of the elbow, the fascia is attached to the tendon of the triceps, and the olecranon. Now remove the fascia corresponding to the incisions through the skin, in order to see the muscles on the front of the arm namely, the biceps, the coraco- brachialis, and the brachialis anticus. The long rounded muscle in front is the biceps ; the muscle attached with it to the coracoid process is the coraco-brachialis ; and the broad flat muscle covering the lower end of the humerus is the brachialis anticus. The biceps, as its name implies, arises by two heads a long and a short. The short head arises from the tip of the coracoid process of the scapula, by a thick, flat tendon in common with a slender muscle on its inner side, called the coraco-brachialis. The long head arises from the upper border of the glenoid fossa of the scapula and the glenoid ligament, by a long, rounded tendon, which, traversing the shoulder-joint, passes over the head of the humerus ; there pierces the capsular ligament, 330 THE BICEPS. and descends in the groove between the two tuberosities. The tendon is retained in the groove by a fibrous bridge derived from the capsule of the joint, and connected with the tendon of the pec- toralis major. Divide this bridge, and see that the synovial mem- brane of the joint is reflected round the tendon, and accompanies it for about two inches down the groove, thus forming a synovial fold. The object of this is to facilitate the play of the tendon, and to carry little arteries (from the anterior circumflex) for its supply. The two heads unite about the middle of the arm, and form a single muscle, which terminates on a strong flat tendon of considerable length ; this dips down into the triangular space at the bend of the elbow, and, after a slight twist upon itself, is inserted into the posterior part of the tubercle of the radius. The anterior part of the tubercle, over which the tendon plays, is crusted with cartilage,, and a bursa intervenes to diminish friction. The most internal fibres of the muscle are inserted into a strong broad aponeurosis, which is prolonged from the inner border of the tendon to the fascia on the inner side of the forearm. This aponeurosis, called the semilunar fascia of the biceps, .protects the brachial vessels and the median nerve at the bend of the elbow. The action of the biceps is twofold. 1. It is a flexor of the forearm. 2. It is a powerful supinator of the forearm, in conse- quence of its insertion into the posterior part of the tubercle of the radius. Its power of supination is greatest when the forearm is half bent, because its tendon is then inserted at a right angle. Why does the long tendon pass through the shoulder-joint ? It acts like a strap, and confines the head of the hunierus in its proper centre of motion. 1 But for this tendon, the head of the bone, when the deltoid acts, would be pulled directly upwards and strike against the under surface of the acromion. When the tendon is ruptured, or dislocated from its groove, a man can move his arm backwards and forwards, but he cannot raise the smallest weight. 2 The 1 Another action of the long tendon of the triceps would seem to be that of an internal rotator of the humerus when that bone is rotated externally. The marked prominence of the internal tuberosity and the groove on its outer aspect would favour this view. 2 See a preparation in the Museum of St. Bartholomew's Hospital. BKACHIALIS ANTICUS. 331 biceps is supplied with blood by a branch from the brachial, which runs into the middle of its inner side, and divides into ascending and descending branches. Its nerve comes from the musculo- cutaneous. COEACO- This thin muscle is situated at the upper part BKACHIALIS. o f the arm, and runs parallel to the inner border of the short head of the biceps. It arises by fleshy fibres from the point of the coracoid process, in common with the short head of the biceps, and from a fibrous septum which lies between them. The muscle descends backwards and outwards, and terminates on a flat tendon, which is inserted into the inner side of the middle of the humerus, between the brachialis anticus and the inner head of the triceps. Its action is to draw the humerus forwards and in- wards e.g. in bringing the gun up to the shoulder. It is supplied by a branch from the musculo-cutaneous nerve which pierces it. Concerning the coraco-brachialis, remember : 1 . That the mus- culo-cutaneous nerve runs through it; 2. That its inner fleshy border is the guide to the axillary artery in the last part of its course ; 3. That the brachial artery lies upon its flat tendon of in- sertion, and can here be effectually compressed by the finger or the tourniquet. The coraco-brachialis and biceps are covered at their upper part by the deltoid and pectoralis major. The head of the humerus rolls beneath the coraco-brachialis and short origin of the biceps ; and a large bursa is interposed between these muscles and the tendon of the subscapularis, which covers the head of the bone. BRACHIALIS This broad muscle covers the lower half of the ANTICCS. humerus, and is partially concealed by the biceps. Between the two muscles is the musculo-cutaneous nerve, which supplies them both. It arises from the humerus by a fleshy digitation on either side of the tendon of the deltoid ; from the lower half of the front and inner surfaces of the bone, and from the intermuscular septa. The muscle, becoming thicker and broader, covers the front of the cap- sule of the elbow-joint, to which it is more or less attached, and terminates on a tendon, which is inserted in a 'pointed manner into the anterior surface of the coronoid process of the ulna. Its 332 BRACHIAL AETERY. action is to bend the forearm. Its nerves come from the musculo- cutaneous', and it usually receives in addition a small branch from the musculo-spiral. Now examine the course and relations of the brachial vessels and nerves. COURSE AND BE- Th brachial artery the continuation of the IATIONS or THE axillary takes its name at the lower border of BRACHIAL ARTERY. fo e teres ma j O r. It runs down the anterior and the inner side of the arm, along the inner border of the coraco- brachialis and biceps, to about an inch below the elbow, where it divides, near the coronoid process of the ulna, into the radial and ulnar arteries. Thus its direction corresponds with a line drawn from the deepest part of the axilla to the middle point between the condyles of the humerus. In the upper part of its course it lies on the long and inner heads of the triceps (from the long head it is separated by the musculo-spiral nerve and superior profunda artery) ; in the middle, it lies on the tendon of the coraco-brachialis ; in the lower part, on the brachialis anticus. In front of the artery are the internal cutaneous nerve, the median basilic and basilic veins ; the median nerve, which crosses obliquely over the artery, being on its outer side near the axilla, and on its inner side near the elbow ; and lastly, the artery is more or less overlapped, in the first part of its course, by the coraco- brachialis, lower down by the fleshy belly of the biceps ; the inner borders of these muscles, in their respective situations, being the best guides to the artery. On the outer side of the artery are, the median nerve, the coraco- brachialis, and biceps. On the inner side are, at first, the ulnar nerve, the internal cutaneous nerves ; and, below, the median nerve. The artery is accompanied by two veins (vence comites) and the median nerve, all of which are invested in a common sheath of fascia. The ulnar nerve runs along the inner side of the artery as far as the middle of the arm. Below this point, the nerve leaves the BRANCHES OF THE BRACHIAL ARTERY. 333 artery, and passes through the internal intermuscular septum to get behind the internal condyle. About the middle of the humerus, the artery lies for nearly two inches on the tendon of the coraco-brachialis, and is so close to the bone that it can be effectually compressed, provided the pressure be made in the proper direction namely, outwards. Here, too, it is crossed by the median nerve. At the bend of the elbow the artery is crossed by the seinilunar fascia from the biceps. It enters a triangular space, bounded by the pronator radii teres internally, and by the supinator radii longus externally. It sinks into this space, with the tendon of the biceps to its outer side, and the median nerve to its inner ; all three rest upon the brachialis anticus! To compress the artery here, pressure should be made directly backwards. Opposite the coronoid process of the ulna it divides into the radial and ulnar arteries. Two veins, of which the internal is the larger, lie in close con- tact with the brachial artery, and communicate at frequent intervals by transverse branches. Near the axilla they join and form the axillary vein. BRANCHES OF The brachial artery gives off four branches, all BKACHIAL ARTERY, from its inner side : namely, the superior profunda, the inferior profunda, the nutrient artery, and the anastomotica magna. It also distributes muscular branches to the coraco- brachialis and biceps, which are given off from its outer side. a. The profunda superior arises from the inner and back part of brachial artery, immediately below the tendon of the teres major. 1 It winds round the back of the humerus, between the outer and inner heads of the triceps, accompanied by the musculo-spiral nerve, and, a little above the middle of the arm, divides into two branches, which run for some distance on either side of the nerve. One of these runs in the substance of the triceps muscle, with the nerve to the anconeus, as far as the olecranon, and anastomoses with the posterior ulnar recur- rent, the interosseous recurrent, and anastomotica magna arteries : the other branch accompanies the musculo-spiral nerve to the outer side of 1 If the profunda be not in its usual place, look for it above the tendon of the latissimus dorsi, where it will probably be given off from a common trunk with the posterior circumflex. 334 BRANCHES OF THE BRACHIAL ARTERY. the arm, where it perforates the external intermuscular septum. It then descends deep in the interval between the brachialis anticus and supinator radii longus, and terminates in numerous ramifications, some of which pass in front of the external condyle, others behind it, to inosculate with the radial and interosseous recurrent arteries. Fia. 81. Superior profunda . . . , Interosseous recurrent . .. Radial recurrent . . . . Posterior interosseons . . Inferior profunda. Anastomotica magna. Anterior ulnar recurrent. Posterior ulnar recurrent. Common interosseous. Anterior interosseous. PLAN OF THE CHIEF BRANCHES OF THE BRACHIAL ARTERY AND THE ARTERIAL INOSCULATIONS ABOUT THE RIGHT ELBOW-JOINT. Before its division, the superior profunda sends several branches to the deltoid, coraco-brachialis, and the triceps, some of which inosculate with the circumflex. These assist in establishing a collateral cir- culation when the brachial artery is ligatured above the origin of the profunda. b. The profunda inferior arises from the brachial, opposite to the BRANCHES OF THE BRACHIAL ARTERY. 335 insertion of the coraco-brachialis, or sometimes by a common trunk with the superior profuiida. It runs with the ulnar nerve on the inner head of the triceps (which it supplies), passes through the internal intermuscular septum, and then descends to the interval between the internal condyle and the olecranon, inosculating with the posterior ulnar recurrent and anastomotica magna arteries. It also sends a small branch down in front of the internal condyle to anastomose with the anterior ulnar recurrent. c. The nutrient artery of the humerus arises sometimes from the brachial, sometimes from the inferior profunda. It pierces the tendon of the coraco-brachialis, runs obliquely downwards through the bone, and in the medullary canal divides into ascending and descending branches, which anastomose with the nutrient vessels of the bone derived from the periosteum. d. The anastomotica magna arises from the inner side of the brachial, about two inches above the elbow, runs tortuously inwards transversely across the brachialis anticus, and divides into branches, some of which pass in front of the internal" condyle, anastomosing with the anterior ulnar recurrent artery ; another passes behind the internal condyle by piercing the intenial intermuscular- septum, and anastomoses with the inferior profunda and posterior ulnar recurrent arteries ; and one branch forms an arch, above the olecranon fossa, with the superior profunda. e. Numerous mitscular branches arise from the outer side of the brachial artery : one of these, the bicipital, more constant than the rest, supplies the biceps ; another runs transversely beneath the coraco- brachialis and biceps, over the insertion of the deltoid, supplying this muscle and the brachialis anticus- The two veins which accompany the brachial artery are continuations of the deep radial and ulnar veins. The internal is usually the larger, and generally receives the veins corresponding to the principal branches of the artery. In their course they are connected at intervals by trans- verse branches either in front of, or behind the artery. Near the subscapularis, the vena comes externa crosses obliquely in front of the axillary artery to join the vena comes interna, which then takes the name of axillary. Now trace the great nerves of the upper arm, which proceed from the brachial plexus near the tendon of the subscapularis : 336 NERVES OF THE UPPER ARM. namely, the median, the musculo-cutaneous, the ulnar, and the musculo-spiral nerves. The median nerve, so called from the course it takes along the front of the arm and the forearm, arises by two roots, which converge in front of the axillary artery (p. 321). The external root is derived from the outer cord, in com- mon with the musculo-cutaneous ; the internal from the inner cord, in common with the ulnar and internal cutaneous. In its course down the arm, the nerve is situated at first on the outer side of the brachial artery, between it and the coraco-brachialis ; about the middle of the arm the nerve crosses obliquely over (in some cases under) the vessel, so that at the bend of the elbow it is found on the inner side of the artery, lying upon the brachialis anticus, and covered by the semilunar fascia from the biceps. 1 As a summary of the distribution of the median nerve, we may say that it supplies the two pronators and all the flexors of the forearm (except the flexor carpi ulnaris and the ulnar half of the 1 I have observed the following varieties relating to the median nerve, and its course in regard to the artery. a. The roots may be increased in number by one on either side of the artery ; or the internal root may be deficient. b. They may vary in their position with regard to the artery : both may be situated behind the vessel ; or one behind, and the other in front of it. c. The nerve, formed in the usual manner, may be joined lower down by a large branch from the external cutaneous ; such a case presents a junction of two large nerves in front of the brachial artery, in the middle of the arm. d. The nerve in many cases crosses under, instead of over the artery. e. The nerve sometimes runs parallel and external to the artery ; or it may run parallel to, and in front of, the artery. In one hundred arms the relative position of the nerve to the artery in its course down the arm was as follows : In 72, the nerve took the ordinary course. 20, the nerve crossed obliquely under the artery. ,, 5, the nerve ran parallel and superficial to the artery. ,, 3, the nerve ran parallel and external to the artery. These varieties of the median nerve are of practical importance, for this reason : whenever in the operation of tying the brachial artery, we do not find the nerve in its normal position, we may expect to find some irregular distribution of the arteries e.g. a high division of the brachial, or even, which I have often seen, a ' vas aberrans ' coming from the upper part of the brachial, and joining either the radial or ulnar arteries. MUSCULO-CUTANEOUS AND ULNAE NERVES. 337 flexor profundus digitorum) ; the muscles of the ball of the thumb, the two radial lumbricales, both sides of the thumb, fore and middle fingers, and the radial side of the ring finger, on their palmar aspect. MORCULO-CUTA- This nerve (often called the external cutaneous NEOUS NERVE. or perforans Casserii) arises in common with the external root of the median, from the external cord of the brachial plexus behind the pectoralis minor, and is situated on the outer side of the axillary artery. It perforates the coraco-brachialis obliquely, and then runs down between the biceps and the bra- chialis anticus to the outer side of the arm. A little above the elbow-joint, between the tendon of the biceps and the supinator radii longus, the nerve pierces the deep fascia and becomes subcu- taneous ; then passing under the median cephalic vein, it divides into an anterior and a posterior branch, for the supply of the inte- guments of the forearm. The musculo-cutaneous nerve, in the upper part of its course, sends branches to the coraco-brachialis and the short head of the b'iceps, and, as it descends between the biceps and the brachialis anticus, it supplies both. Consequently, if the nerve were divided in the axilla, the result would be inability to bend the arm. 1 This nerve also sends small filaments to supply the elbow-joint. This nerve arises from the inner cord of the ULXAB NERVE. . . . brachial plexus, m common with the internal cuta- neous and the inner head of the median. It descends along the inner side of the brachial artery, as far as the insertion of the coraco-brachialis. The nerve then diverges from the artery, run- ning obliquely over the inner head of the triceps, perforates the internal intermuscular septum, and runs with the inferior profunda artery, behind the internal condyle. 1 In some instances the musculo-cutaneous nerve descends on the inner side of the coraco-brachialis without perforating the muscle ; in these cases it often sends a larger branch than usual to the median nerve. The trunk of the musculo-cutaneous nerve may come from the median at any point between the axilla and the middle of the arm. In some subjects the nerve is absent ; all its branches are then supplied by the median, which is larger than usual. Such anomalies are easily explained by the fact of the two nerves having a common origin. Z 338 MUSCULO-SPIRAL NERVE. The distribution of the nerve is to the elbow-joint, to the flexor carpi ulnaris, to half the flexor profundus digitornm, to all the in- terosseous muscles of the hand, to both sides of the little finger, to the ulnar side of the ring finger, on their dorsal and palmar aspects, to the muscles of the ball of the little finger, to the wrist-joint, to the two ulnar lumbricales, and, lastly, to the adductor pollicis, and the inner head of the flexor brevis pollicis. Previous to the examination of the musculo-spiral nerve, we should examine the great muscle which occupies the whole of the posterior part of the humerus viz. the triceps extensor cubiti. TRICEPS EXTEN- This muscle has three distinct origins, named, SOB CUBITI. from their position, the external, the internal, and the middle or long heads (p". 318). The middle or long head arises by a flat tendon from the inferior border of the scapula, close to the glenoid cavity, and in connection with the glenoid and capsular ligaments. The external head arises from the humerus, beginning in a pointed form immediately below the insertion of the teres minor, from the posterior surface between this and the musculo- spiral groove, and from the external intermuscular septum. The internal head arises from the humerus below the insertion of the teres major, from the posterior surface of the bone below the mus- culo-spiral groove, and from the internal intermuscular septum. The three heads unite, near the middle of the arm, to form a single fleshy mass, which covers the posterior part of the elbow-joint, and is inserted by a thick tendon into the summit and sides of the ole- cranon. There is a bursa between the tendon and the olecranon, which is sometimes multilocular. Each head is supplied by a separate branch from the musculo-spiral nerve. 1 MUSCULO-SPIBAL This, the largest of the brachial nerves, arises, NEKVE. i n common with the circumflex, from the posterior cord of the axillary plexus (p. 320). It descends at first behind the axillary artery, and then behind the brachial artery ; it subsequently winds obliquely round the posterior part of the humerus, between the external and internal heads of the triceps, in company with the superior profunda artery. About the lower third of the outer side 1 The subanconcus, a small muscle situated beneath the triceps, will be described later on. DISSECTION OF THE FRONT OF THE FOREARM. 339 of the arm, the nerve perforates the external intermuscular septum, and then runs deeply embedded between the brachialis anticus and the supinator radii longus. The nerve gives off branches on the inner side of the humerus, to the inner and long heads of the triceps, and the internal cuta- neous branch. ; on the back of the humerus, to the external head of the triceps and the anconeus ; on the outer side of the humerus, to the supinator radii longus. the extensor carpi radialis longior, and the brachialis anticus (usually) ; lastly, after perforating the septum, it gives off the upper and lower external cutaneous branches. A little above the elbow-joint the nerve divides into its two principal branches the radial, which accompanies the radial artery along the forearm, and the posterior interosseous, which perforates the supinator brevis, and supplies the muscles on the back of the forearm. To sum up the muscular distribution of this nerve, we may say that it supplies all the extensors of the forearm, wrist, thumb, and fingers ; and all the supinators except one namely, the biceps (supplied by the musculo-cutaneous nerve). DISSECTION OF THE FRONT OF THE FOREARM. SURFACE The front of the forearm presents, at the bend MARKING. o f the elbow, a triangular depression, from which there extends down to the wrist a groove which corresponds to the radial artery ; on the inner side is another groove, increasing in depth towards the wrist, indicating the course of the ulnar artery. The head of the radius can be easily felt on the outer side, below the external condyle of the humerus, and in the lower third the bone becomes again defined, terminating below in the styloid process, beyond which is the prominence of the tubercle of the scaphoid. The border of the ulna can be felt on the inner side of the forearm, in the lower half, and it ends at the wrist in an ill-defined styloid process, which does not descend as low as the corresponding pro- cess of the radius. The lower part of the forearm presents, an inch z 2 340 CUTANEOUS VEINS AND NERVES OF THE FOREARM. beyond the wrist-joint, a transverse furrow, which corresponds with the border of the annular ligament. Prolong the incision down to the wrist, and, at DISSECTION. . . . its termination, make another transversely. Re- flect the skin, and dissect the subcutaneous veins and nerves. CUTANEOUS On the inner side is the anterior ulnar vein, VEINS. which commences on the front of the wrist, and is then continued upwards on the inner side of the forearm as far as the elbow, where it is joined by the posterior ulnar vein to form the common ulnar vein. This vein communicates with the median vein by numerous branches (p. 326). The veins on the back of the hand commence at the extremi- ties of the fingers, run up between the knuckles, and unite on the back of the hand, forming an arch with its concavity upwards. The posterior ulnar vein arises from this arch by a branch (vena salvatella) situated over the fourth interosseous space, and runs up on the back of the forearm, towards the inner condyle, to join the anterior ulnar vein. The radial vein, situated on the outer side of the forearm, com- mences on the back of the hand from the venous arch, runs up the radial side of the front of. the forearm to the elbow, where, after receiving the median cephalic, it becomes the cephalic vein. Running up in front of the middle of the forearm is the median vein ; it communicates in the. forearm with the radial and ante- rior ulnar veins, and near the bend of the elbow it is joined by a deep branch mediana profunda after which it divides into two branches, an outer or median cephalic, which joins the cephalic, and an inner or median basilic, which joins the basilic (fig. 80). CUTANEOUS On the radial side of the forearm, as low down NEBVES. as the wrist, are found the terminal filaments of the anterior branch of the musculo-cutaneous nerve, which, about the middle of the forearm, sends a posterior branch backwards to supply the posterior and lower part of the forearm as low as the wrist, communicating with the radial and external cutaneous branch of the musculo-spiral. At the lower part of the front of the forearm, one or more of these filaments are situated over the radial artery, and one branch passes to the palm to supply DEEP FASCIA OF THE FOREARM. 341 the skin over the muscles of the ball of the thumb ; it commu- nicates with the palmar branch of the median and with the radial nerve. In front of the upper part of the forearm are some filaments of the external cutaneous branch of the musculo-spiral nerve ; on the outer and back part of the forearm, near the elbow, the lower external cutaneous branch of the musculo-spiral runs down as far as the wrist to supply the skin. At the lower third of the radial side of the forearm, the radial nerve becomes superficial, and turns over the radius to supply the back of the hand and fingers. On the ulnar side the anterior division of the internal cuta- neous nerve descends as far as the wrist ; its posterior branch passing to the back of the forearm to supply it as far as the middle. Near the styloid process of the ulna, the dorsal branch of the ulnar nerve perforates the fascia to reach the back of the hand. DEEP FASCIA OP The muscles of the forearm are enveloped by a THE FOKEAEM. dense shining aponeurosis, continuous with that of the arm. Its thickness increases towards the wrist, that the tendons, in this situation, may be kept in their position. It is composed of fibres which cross each other obliquely, and is attached, above, to the condyles of the humerus and olecranon ; internally, to the ridge on the posterior part of the ulna. At the back of the wrist, it forms the posterior annular ligament, and in front, it is continuous with the anterior annular ligament. Above, the fascia is strengthened by fibres from the tendons of the biceps and brachialis anticus. The aponeurotic expansion from the inner edge of the tendon of the biceps is exceedingly strong. It braces the muscles on the inner side of the forearm, and interlaces at right angles with the fibres of the fascia attached to the internal condyle. The under surface of the fascia gives origin to the mus- cular fibres in the upper part of the forearm, and furnishes septa which separate the muscles, and form surfaces for their origin. The fascia is perforated at various parts for the passage of the cutaneous vessels and nerves of the forearm. Remove the fascia from the muscles by incisions corresponding to those for reflecting the skin ; 342 MUSCLES OF THE FOREARM. taking care of the cutaneous branches of the median and ulnar nerves close to the wrist. TRIANGLE AT At the bend of the elbow is a triangular space, THE ELBOW. with its base towards the humerus ; on the inner side this space is bounded by the pronator teres ; on the outer, by the supinator radii longus. In it are the following objects which must be carefully dissected: 1. In the centre is the brachial artery (with its companion veins) dividing into the radial as its outer, and into the ulnar as its inner branch ; 2, on the outer side of the artery is the tendon of the biceps ; 3, on the inner side is the median nerve ; 4, the musculo-spiral nerve on the outer side is partly concealed by the supinator longus ; 5, the radial recurrent artery > 6, the anterior ulnar recurrent ; 7, the common interos- seous branch of the ulnar artery ; 8, the vena mediana profunda. MUSCLES OF The muscles of the forearm are arranged in two THE FOBEARM. groups : one, consisting of supinators and exten- sors, is attached to the outer condyloid ridge and condyle; the other, consisting of pronator and flexors, is attached to the inner condyle. The inner group should be examined first. They arise by a common tendon, and are arranged in the following order : pronator teres ; flexor carpi radialis ; palmaris longus ; flexor sub- limis digitorum, and flexor carpi ulnaris. PRONATOR This muscle forms the inner boundary of the RADII TERES. triangular space at the elbow. It arises by two heads ; one, from the anterior surface of the internal condyle, from the common tendon, from the fascia of the forearm, and from the septum between it and the flexor carpi radialis ; the other, by a small tendinous origin from the inner border of the coronoid pro- cess of the ulna. From these two origins, between which the median nerve passes, the muscle proceeds obliquely downwards and outwards across the forearm, and is inserted by a flat tendon into a rough surface on the outer and back part of the middle third of the radius. In amputating the forearm, it is very desir- able to save the insertion of this muscle, that the stump may have a pronator. its nerve comes from the median. FLEXOR CARPI This muscle, situated on the ulnar side of the EADIALIS. preceding muscle, arises by the common tendon MUSCLES OF THE FOREARM. 343 from the internal condyle, from the intermuscular septa, and from the fascia of the forearm. The fleshy fibres terminate a little above the middle of the forearm, in a flat tendon, which runs in a FIG. 82. 1. Biceps. 2. Brachialis anticus. 3 Sapinator longus. 4. Pronator radii teies. 5. Flexor carpi radialis. 6. Palmaris longus. 7. Flexor carpi ulnaris. 8. Flexor sublimis digitorum. 9. Flexor longus pollicis. 10. Extensor ossis metacarpi and the primi internodii pollicis. 11. Triceps. 12. Radial artery. 13. Ulnar artery. DIAGRAM OF THE MUSCLES OF THE FRONT OF THE FOREABM. separate sheath outside the anterior annular ligament of the wrist, passes through a groove in the os trapezium, bridged over by fibrous tissue and lined by a synovial membrane, and is inserted into the base of the metacarpal bone of the index finger. The outer border 344 MUSCLES OF THE FOEEARM. of its tendon is the guide to the radial artery in the lower half of the forearm. Its nerve comes from the median. 1 PALMARIS This slender muscle arises from the common LONGUS. tendon at the internal condyle, from the inter- rnuscular septa, and from the fascia of the forearm. About the middle of the forearm it terminates in a flat tendon, which de- scends along the middle of the forearm to the wrist, lying upon the flexor sublimis digitorum ; it then passes over the anterior annular ligament, and is continued into the palmar fascia. This muscle is a tensor of the palmar fascia. 2 Its nerve comes from the median. FLEXOK CARPI This muscle arises by two heads : one from the ULNARIS. internal condyle, the common tendon, and the intermuscular septum ; the other from the inner edge of the olecranon : these two origins form an arch, under which the ulnar nerve and the posterior ulnar recurrent artery pass. It also arises from the upper two-thirds of the posterior edge of the ulna, through the medium of the aponeurosis, which is common to this muscle, the flexor profundus digitorum, and the extensor carpi ulnaris. The tendon appears on the radial side of the muscle, about the lower third of the forearm, and receives fleshy fibres on its ulnar side as low as the wrist. It is inserted into the pisiform bone, and thence by a strong tendon into the unciform and the base of the fifth metacarpal bone. Its nerve comes from the ulnar. The tendon of the flexor carpi ulnaris is the guide to the ulnar artery, which lies close to its radial side, and is overlapped by it. As it passes over the annular ligament, the tendon furnishes a fibrous expansion to protect the ulnar artery and nerve. FLEXOR SUBLI- This muscle has three distinct origins, and is MIS DIGITORUM. situated beneath those previously mentioned, so 1 A muscle is not infrequently found beneath this muscle, called by Mr. Wood the flexor carpi radialis brevis, or profundus. It arises from the front of the radius above the pronator quadratus, and is inserted into the base of the meta- carpal bone of the middle finger. (Journ. of Anat. and Phys., p. 55, Nov. 1866.) '* The palmaris longus is absent in about one out of ten subjects. The situa- tion of its muscular portion is subject to variety ; sometimes occupying the middle, sometimes the lower third of the forearm. The tendon is in some instances wholly inserted into the anterior annular ligament. MUSCLES OF THE FOREARM. 345 that, in order to expose it fully, the preceding muscles should be reflected, by cutting them through the middle, and turning the ends upwards and downwards. The longer origin takes place from the internal condyle, from the internal lateral ligament, the com- mon tendon, and the intermuscular septa ; the second origin takes place from the coronoid process of the ulna above the pronator teres ; the third origin, by tendinous and fleshy fibres from the oblique ridge on the front of the radius, extending from the tubercle to about an inch below the insertion of the pronator teres. This, called its radial origin, is partly concealed by the pronator teres. The muscle, thus formed, passes down the middle of the forearm, and divides into four distinct muscular slips : from these, four tendons arise, which pass beneath the annular ligament, arranged in two pairs ; the tendons of the middle and ring fingers being placed over those of the fore and little fingers. The tendons pass through the palm to the fingers, where they diverge and split to allow the passage of the deep flexor tendons, and are inserted into the sides of the second phalanges where they will be subse- quently traced. Its action is, therefore, to bend the second joint of the fingers. The muscles described as arising from the internal condyle are all supplied by the median nerve, except the flexor carpi ulnaris, which is supplied by the ulnar. Having finished the superficial muscles on the inner side of the forearm, notice one of those on the outer side, named supi- nator radii longus, before tracing the vessels and nerves of the forearm. SUPINATOB This muscle forms the external boundary of the RADII LONGUS. triangular spac"e at the bend of the elbow. It arises by fleshy fibres from the upper two-thirds of the external condyloid ridge of the humerus, commencing a little below the insertion of the deltoid, and from the external intermuscular septum. The muscular fibres terminate about the middle of the forearm in a flat tend.cn, which is inserted into the outer side of the base of the styloid process of the radius. The inner border of the muscle is the guide to the radial artery which lies between this muscle and the flexor carpi radialis. It supinates the hand, but 346 RADIAL ARTERY. acts much more powerfully as a flexor of the forearm. It is supplied by the musculo-spiral nerve. The radial artery, the smaller division of the brachial, runs down the radial side of the forearm to the wrist, where it turns over the external lateral ligament of the carpus, beneath the extensor tendons of the thumb, and sinks into the angle between the first and second metacarpal bones to form the deep palmar arch. Thus, its course corresponds with a line drawn from the middle of the bend of the elbow to the front of the styloid process of the radius. In the upper third of the forearm, the artery lies deep between the pronator teres on the inner and the supinator longus on the outer side ; the fleshy border of the latter overlaps it in muscular subjects. In the lower two-thirds of the forearm the artery is more superficial, and is placed between the tendons of the supi- nator longus on the outer and the flexor carpi radialis on the inner side. In its course, it lies successively on the following : first, upon the tendon of the biceps ; secondly, upon the supinator radii brevis ; thirdly, upon the insertion of the pronator teres ; fourthly, upon the radial origin of the flexor sublimis ; fifthly, upon the flexor longus pollicis ; sixthly, upon the pronator quadratus, and lastly, upon the lower end of the radius. The artery then turns round the outer side of the wrist-joint, lying upon the external lateral ligament, and covered by the tendons of the extensores ossi metacarpi, and primi internodii pollicis, some cutaneous veins and branches of the radial nerve ; next, it lies upon the trapezium ; it is then crossed by the extensor secundi internodii pollicis ; and, lastly, passing between the two heads of the first dorsal interosseous muscle, it enters the palm to form the deep palmar arch. It is accompanied by two veins, which communicate at frequent inter- vals, ard join the venae comites of the brachial artery at the bend of the elbow. In the middle third of its course the artery is accompanied by the radial nerve (a branch of the musculo-spiral), which lies to its outer side. Below this point, the nerve leaves the artery, and passes, under the tendon of the supinator longus, to the back of the hand. BRANCHES OF THE RADIAL ARTERY. 347 Thus, in the situation where the pulse is usually felt, the radial nerve no longer accompanies the artery ; nevertheless, the vessel is accompanied by a branch of the musculo-cutaneous (or external cutaneous), which lies superficially to it. The radial artery sends off in the forearm the following branches, besides offsets, which supply the muscles on the outer side of the forearm a. The radial recurrent is given off just below the elbow ; it ascends upon the supinator brevis, between the supinator longus and the bra- chialis anticus, to supply the long and short supinators and the two radial extensors. It runs up with the musculo- spiral nerve, and forms a delicate inosculation with the superior profunda (p. 333). b. The muscular branches which are given off to the muscles on the outer side of the forearm. c. The arteria superficialis voice, arises from the radial, about, half an inch, or more, above the lower end of the radius : it runs over the anterior annular ligament, above, or through, the origin of the muscles of the ball of the thumb, into the palm of the hand, where it sometimes inosculates with the superficial branch of the ulnar, and completes the superficial palmar arch. 1 d. The anterior carpal artery is a small branch of the radial, which arises close to the lower border of the pronator quadratus, and then runs beneath the tendons, and supplies the anterior surface of the synovial membrane and bones of the carpus, anastomosing with the anterior interosseous, the anterior carpal branch of the ulnar, and the recurrent carpal branch of the deep palmar arch. At the wrist it gives off e. The posterior carpal artery, which runs beneath the extensor tendons,' and joins the corresponding branch of the ulnar to form an arch ; it also anastomoses with the anterior interosseous artery on the back of the wrist. The radial nerve, a branch of the musculo-spiral, is given off above the bend of the elbow, deep 1 There is great variety in the size and origin of the superficialis volse ; some- times it is very large, arises higher than usual, and runs to the wrist parallel with the radial ; sometimes it is very small, terminating in the muscles of the thumb ; or it may be absent. 348 ULNAR ARTERY. between the supinator radii longus and brachialis anticus ; it descends on the outer side of the radial artery, covered by the supinator radii longus. In the upper third of the forearm, the nerve is at some distance from the artery ; in the middle third, it approaches nearer to it, lying to its outer side j but in the lower third, the nerve leaves the artery, passes underneath the tendon of the supinator longus, perforates the deep fascia on the outer side of the forearm, and becomes subcutaneous. It then divides into two branches : an outer, the smaller, which supplies the skin of the ball of the thumb, and communicates with the anterior branch of the musculo-cutaneous nerve ; and an inner, which generally supplies both sides of the dorsal aspects of the thumb, of the index and middle fingers, and of the radial side of the ring finger. This artery, the larger of the two divisions of the brachia], comes off below the elbow, runs obliquely inwards along the ulnar side of the forearm to the wrist, passes over the annular ligament near the pisiform bone, and, enter- ing the palm, forms the superficial palmar arch, by inosculating with the superficialis volas. In the upper half of its course the artery describes a gentle curve with the concavity towards the radius, and lies deep beneath the superficial layer of muscles, namely, the pronator teres, flexor carpi radialis, palmaris longus, and flexor sublimis digitorum. It is also crossed in its upper part by the median nerve. In the lower part of its course it comes nearer the surface, and descends between the flexor sublimis and flexor carpi ulnaris, of which the tendon partially overlaps it at the wrist. The artery lies for a short distance on the brachialis anticus ; in the remainder of its course it lies on the flexor profundus digitorum. The ulnar nerve is at first separated from the artery by a con- siderable interval : about the middle of the forearm it joins the artery, and accompanies it in the rest of its course, lying close to its inner side. Both pass over the anterior annular ligament of the carpus, lying close to the pisiform bone, the nerve being nearer to the ulnar side and a little behind the artery. A strong expansion from the tendon of the flexor carpi ulnaris protects them in this exposed situation. BRANCHES OF THE ULNAR ARTERY. 349 Observe that the ulnar artery, in the lower third of its course, lies under the radial border of the tendon of the flexor carpi ulnaris, which is the surgical guide to the vessel. The artery is accompanied by two veins, which join the venas comites of the brachial. The ulnar artery gives off the following branches in the fore- arm : a. The anterior and posterior ulnar recurrent arteries arise imme- diately below the elbow-joint, sometimes by a common trunk. The anterior passes upwards between the brachialis anticus and the pronator teres, and inosculates with the inferior profunda and anastomotica magna. The posterior, the larger, ascends between the flexor sublimis and the flexor profundus digitorum, to the space between the internal condyle and the olecranon : it then passes up between the two heads of the flexor carpi ulnaris, where it inosculates with the inferior profunda, the anastomotica magna, and, above the olecranon, with the posterior interosseous recurrent (p. 333). b. The common interosseovis artery is about half an inch long. It arises from the ulnar, just below the tubercle of the radius, and soon divides into the anterior and posterior interosseous, which we shall examine presently. c. The 'muscular branches which supply the muscles on the ulnar side of the forearm. d. The carpal branches are given off just above the pisiform bone : the posterior carpal runs beneath the tendon of the flexor carpi ulnaris and the extensor tendons, and forms, with the corresponding branch of the radial artery, an arch, from which are usually given off the second and third dorsal interosseous arteries : these anastomose with the per- forating arteries. The anterior carpal runs in front of the carpus, beneath the flexor tendons, supplies the synovial membrane and the ligaments, and anastomoses with the anterior carpal from the radial. This nerve runs behind the internal condvle, ULNAK NEKVE. , . . . a " . between two origins of the flexor carpi ulnaris. In its course down the ulnar side of the upper part of the forearm, the nerve is still covered by this muscle, and lies upon the flexor profundus digitorum. About the middle of the forearm, the nerve joins the ulnar artery, and runs along its inner side over the anterior annular ligament into the palm. 350 ULNAR AND MEDIAN NERVES. The ulnar nerve gives off the following branches : a. The articular branches to the joint are given off to it, immediately behind the elbow. b. The muscular branches are distributed to the flexor carpi ulnaris and the ulnar half of the flexor profundus digitorum, and are given off from the ulnar a short distance below the elbow. c. A cutaneoiis branch is given off about the middle of the forearm, one filament of which, called the palmar ctitaneous branch, accompanies the ulnar artery to the palm, and communicates with branches from the median nerve. d. The dorsal cutaneous branch, of considerable size, is given off from the ulnar about two inches above the styloid process of the ulna to pass to the back of the hand. It crosses under the tendon of the flexor carpi ulnaris, pierces the deep fascia, and, immediately below the styloid process of the ulna, appears on the back of the hand, where it divides into branches which supply the back of the little finger, and half the ring : here also it sends a branch which communicates with the corre- sponding branch of the radial nerve. e. Articular branches are also distributed to the wrist-joint. This nerve, at the bend of the elbow, lies on the inner side of the brachial artery and beneath the bicipital fascia. It then passes between the two heads of origin of the pronator teres, and descends along the middle of the forearm, between the flexor sublimis and the flexor profundus digitorum. At the lower part of the forearm, it becomes more superficial, lying above the wrist between the outer tendon of the flexor sublimis and the inner border of the tendon of the flexor carpi radialis ; beneath, or to the ulnar side of the palmaris longus, and having in front of it the skin and deep fascia ; it then enters the palm beneath the anterior annular ligament, and divides into five branches for the supply of the thumb, both sides of the fore and middle fingers, and the radial side of the ring finger. Immediately below the elbow, the median nerve sends off: a. The musctdar branches to the pronator teres, and to all the flexor muscles of the forearm, except the flexor carpi ulnaris and the ulnar half of the flexor profundus, which are supplied by the ulnar nerve. DEEP MUSCLES OF THE FOREARM. 351 6. The anterior interosseous nerve, also a branch of the median, runs with the anterior interosseous artery on the interosseous membrane, lying on its radial side, between the flexor longus pollicis and flexor profundus digitorum : it supplies both these muscles and the proiiator quadratus. c. The palmar cutaneoiis branch is given off from the median before it passes beneath the annular ligament. This branch passes over the ligament, and divides into numerous filaments to supply the skin of the palm and the ball of the thumb, communicating with the cutaneous palmar branches of the ulnar, the external cutaneous, and the radial nerves. Now reflect the superficial layer of muscles, to see those more deeply seated. Preserve the prin- cipal vessels and nerves. The deep-seated muscles are, on the ulnar side, the flexor digi- torum profundus ; and, on the radial side, the flexor longus pollicis ; beneath both, near the wrist, lies a transverse muscle, the pronator quadratus. On the interosseous membrane, between the first two named muscles, run the anterior interosseous artery and nerve. FLEXOK PRO- This is the thickest muscle of the forearm. It FTJNDUS DIGITO- arises from the upper two-thirds of the anterior EUMg surface of the ulna, surrounding the insertion of the brachialis anticus above, from the same extent of its internal surface, from the aponeurosis attached to the posterior edge of the ulna, and from the ulnar two-thirds of the interosseous membrane. About the middle of the forearm the muscle is inserted into four flat tendons, of which only that which goes to the index finger is separate from the others above the wrist. These tendons lie upon the same plane, and pass beneath the annular ligament, under those of the superficial flexor, into the palm, where they diverge to pass to their respective fingers. On the first phalanx of the fingers, the tendons of the deep flexor perforate those of the super- ficial, and are inserted into the bases of the third or ungual pha- langes. It derives its nerves from the interosseous branch of the median and from the ulnar. FLEXOR LONGUS This muscle is situated on the front surface of POLLICIS. the radius, outside the preceding. It arises from the front surface of the radius, between the tubercle and the oblique 352 ANTERIOR INTEROSSEOUS ARTERY. ridge above, and the pronator quadratus below, and from the inter- osseous membrane. 1 Its tendon, which begins on the ulnar side of the muscle, proceeds beneath the annular ligament to the base of the last phalanx of the thumb. Its nerve comes from the inter- osseous branch of the median. PRONATOR This square muscle arises from the lower fourth QUADRATUS. o f the ulna and from a strong aponeurosis which covers its anterior surface ; its fibres pass, some transversely, some obliquely outwards, and are inserted into the lower fourth of the anterior surface and the outer border of the radius. It pronates the radius on the ulna. Its nerve proceeds from the interosseous branch of the median. . ANTERIOR Nearly on a level with the insertion of the INTEROSSEOUS biceps, the ulnar artery gives off from its outer ARTERY. g ^ e ^he common interosseous, which runs back- wards for about an inch, and divides into the anterior and posterior interosseous. The anterior interosseous artery runs down on the interosseous membrane, lying deeply between the flexor profundus digitorum and flexor longus pollicis. At the upper edge of the pronator quadratus it divides into two branches ; one of which, the smaller, passes beneath the muscle, supplies it and the front of the carpal bones, communicating with the anterior carpal arteries from the radial and ulnar ; the other, the more important, perforates the interosseous membrane, and helps to supply the muscles on the back of the forearm . A branch, the arteria comes nervi mediani, proceeds from the anterior interosseous. It lies in close contact with the nerve, sometimes in its very centre : though usually of small size, it may be as large as the ulnar artery itself, and, in such cases, it passes under the annular liga- ment with the nerve to join the palmar arch. This is interesting, because it helps to explain the recurrence of haemorrhage from a wound in the palm, even after the radial and ulnar arteries have been tied. The anterior interosseous artery gives off branches to the muscles on each side ; also the mitrient arteries which enter the radius and ulna, near the centre of the forearm, to supply the medullary membrane ; these arteries pass upwards towards the elbow. 1 Sometimes by a slip from the coronoid process. DISSECTION OF THE PALM OF THE HAND. ANTERIOR IN- ^his nerve is a branch of the median ; it gene- TEROSSEOUS rally runs close to the radial side of the artery, NEEVE - and supplies the flexor longus pollicis, half the flexor profundus digitorum, and the pronator quadratus. DISSECTION OF THE PALM OF THE HAND. SURFACE On the ulnar side of the palm of the hand is MARKING. a round long eminence, hypothenar, which corre- sponds with the muscles of the ball of the little finger ; and on the radial side, placed obliquely over the metacarpal bone of the thumb, is another eminence, thenar, which is caused by the muscles of the ball of the thumb. Between the two eminences, at the wrist, is a slight depression, corresponding 'with the middle of the annular ligament, and which broadens out towards the fingers. The palm of the hand, about an inch from the clefts of the fingers, presents a transverse furrow, which corresponds with the meta- carpo-phalangeal articulations, with the distal limit of the synovial sheaths of the flexor tendons, with the divisions of the palmar fascia into its four processes, and with the transverse metacarpal ligament. The superficial palmar arch may be indicated by a line drawn from the cleft of the extended thumb across the palm ; the deep palmar arch lies half an inch nearer the annular ligament. Make a vertical incision along the centre of the palm, and a transverse one along the bases of the fingers ; from this transverse cut continue vertical incisions along the front of the fingers, and reflect the skin ; taking care not to remove a small cutaneous muscle the palmaris brevis situated over the ball of the little finger, and also two small cutaneous branches of the median and ulnar nerves, which are found in the fat of the palm. Observe how closely, in the centre of the palm, the skin adheres to the palmar fascia beneath it. On the ball of the little finger and the distal ends of the metacarpal bones, the subcutaneous structure is composed of a dense filamentous tissue, which con- tains numerous pellets of fat, forming an elastic pad. A similar A 'A 354 PALMAR FASCIA. padding protects the palmar surfaces of the fingers. These cushions on the ends of the fingers defend them in the powerful actions of the hand; they are also useful in subservience to the nerves of touch. The palm is supplied with nerves by three small branches the palmar branch of the median passes in front of the anterior annular ligament to the centre of the palm ; the palmar branch of the ulnar supplies the inner aspect of the hand; and the ante- rior branch of the musculo-cutaneous nerve is distributed to the skin over the thenar eminence. The terminal branches of these cutaneous nerves communicate with each other. PALMAEIS This small cutaneous muscle is situated on the BEEVIS. inner side of the palm. It arises from the inner edge of the central palmar fascia and the annular ligament, and is inserted into the skin on the ulnar border of the palm. Its use is to support the pad on the inner edge of the palm : it acts power- fully as we grasp; it raises the inner edge of the palm, and deepens the hollow of it, forming the so-called ' cup of Diogenes.' It is supplied by the ulnar nerve. This fascia has a silvery lustre, and, in the centre of the palm, is remarkably dense and strong. It is divided into three portions : a central, by far the strongest ; an external, covering the muscles of the thumb ; and an internal, covering the muscles of the little finger. From the deep surface of the fascia two septa dip down, and divide the palm into three separate compartments ; one for the ball of the thumb, a second for that of the little finger, and a third for the centre of the palm. The fascia is formed by a prolongation from the anterior an- nular ligament. It is also strengthened by the expanded tendon of the palmaris longus. The central portion of the fascia is triangular, with the apex at the wrist. About the middle of the palm it splits into four portions, which are connected by transverse tendinous fibres, extending completely across the palm, and corresponding pretty nearly to the transverse furrow of the skin in this situation. Examine any one of these four portions of the fascia, and you will find that it splits into two strips which embrace the corre- PALM OF THE HAND. 355 spending flexor tendons, and are intimately connected with the transverse metacarpal ligament. The effect of this is that the flexor tendons of each finger are kept in place in the palm, by a fibrous ring. Between the four divisions of the palmar fascia the digital vessels and nerves emerge, and descend in a line with the clefts between the fingers. In the hands of mechanics, in whom the palmar fascia is usually very strong, we find that slips of it are lost in the skin at the lower part of the palm, and also for a short distance along the sides of the fingers. The chief use of the palmar fascia is, to protect the vessels and nerves from pressure, when anything is grasped in the hand. It also confines the flexor tendons in their proper place. Beneath the interdigital folds of the skin, there are aponeurotic fibres to strengthen them, constituting what are called the trans- verse ligaments of the fingers. They form a continuous ligament across the lower part of the palm, in front of the digital vessels and nerves. Cut through the palmar fascia at its attachment to the anterior annular ligament, and reflect it towards the fingers, so as to expose the vessels, nerves, and tendons in the palm. The vessels lie above the nerves, and the tendons still deeper. There is an abundance of loose connective tissue to allow the free play of the tendons. When suppuration takes place in the palm, it is seated in this tissue. Reflect for a moment what mischief is likely to ensue. The pus cannot come to the surface through the dense palmar fascia, or on the back of the hand ; it will, therefore, run up into the carpal bursa under the annular ligament, and make its way deep amongst the tendons of the forearm. SUPERFICIAL The ulnar artery, having passed over the annular PALMAK AECH. ligament, near the pisiform bone, describes a curve across the upper part of the palm, beneath the palmar fascia, to- wards the thumb, and, gradually diminishing in size, inosculates with the superficialis volse, and very commonly with a branch from the arteria radialis indicis, to form the superficial palmar arch. The curve of the arch is directed towards the fingers, its greatest A A 2 356 SUPERFICIAL PALMAR ARCH. convexity descending as low as a horizontal line drawn across the junction of the upper with the middle third of the palm. In its passage over the annular ligament, the artery lies in the furrow, between the pisiform and unciform bones, and is protected FIG. 83. Kadial artery Superficialis volae . Arteria magna pollicis .... Radialis indicia . . Ulnar artery. Ulnaris profunda. DIAGRAM OF THE SUPERFICIAL AND DEEP PALMAR ARCHES. 1, 2, 3, 4. Interosseous branches. by an expansion from the tendon of the flexor carpi ulnaris to the palmaris longus. The ulnar nerve lies close to the inner side of the artery, both being covered by the palmaris brevis. In the palm, the artery rests for a short distance upon the muscles of the ULNAR NERVE IN THE PALM. 357 little finger, then it lies upon the superficial flexor tendons and the divisions of the ulnar and median nerves, and is covered by the palmar fascia. Immediately below the pisiform bone, the ulnar artery gives off the ulnaris profunda, which sinks deeply into the palm, between the origins of the abductor and flexor brevis minimi digiti, to form the deep palmar arch, by joining the terminal branch of the radial artery. It is accompanied by the deep branch of the ulnar nerve. From the concavity of the arch small recurrent branches ascend to the carpus, and inosculate with the other carpal branches of the radial and ulnar arteries. Four digital arteries arise from the convexity of the arch. They supply all the digits, except the thumb and the radial side of the index finger. The first descends over the muscles on the inner side of the palm, to the ulnar side of the little finger, along which it runs to the apex. The second, third, wad fourth descend nearly vertically between the tendons, in a line with the clefts between the fingers, and, about half an inch above the clefts, each divides into two branches, which proceed along the opposite sides of the fingers nearly to the end of the last phalanges, where they unite to form an arch with the convexity towards the end of the finger ; from this arch numerous branches supply the papillae at the tip of the finger. In the palm of the hand the digital arteries, before they divide, are joined by branches from the corresponding palmar interosseous arteries (branches of the deep palmar arch) (fig. 83). The digital arteries freely communicate, on the palmar and dorsal aspect of the fingers, by transverse branches, which supply the joints and the sheaths of the tendons. Near the ungual phalanx, a considerable branch passes to the back of the finger, and forms a network of vessels which supply the matrix of the nail. ULNAR NEBVE The ulnar nerve passes over the annular liga- IN THE PALM. ment into the palm, on the inner side of the ulnar artery, and a little behind it. It lies in the groove between the pisiform and unciform bones, so that it is perfectly secure from pressure. Immediately below the pisiform bone, the nerve divides into a superficial and a deep palmar branch. The deep branch supplies the muscles forming the ball of the little finger, and 358 MUSCLES OF THE BALL OF THE THUMB. accompanies the ulnaris profunda artery into the palm, to supply all the interosseous muscles, the two ulnar lumbricales, and it ends in branches which are distributed to the first dorsal interosseous, the adductor pollicis, and the inner head of the flexor brevis pollicis : it moreover sends filaments which ascend to supply the wrist-joint, and others which descend to the metacarpo-phalangeal joints. The superficial branch sends filaments to the palmaris brevis, to the skin on the inner side of the palm, and then divides into two digi- tal nerves, one for the supply of the ulnar side of the little finger, the other for the contiguous sides of the little and ring fingers. This branch also communicates with the median nerve behind the superficial palmar arch. All the digital branches run along the sides of the fingers to their extremities superficial to their corre- sponding arteries. ANTEEIOB AN- This exceedingly strong and thick ligament con- KULAB LIGAMENT fines the flexor tendons of the fingers and thumb, OF THE CARPUS. an( j f as t ens together the bones of the carpus. It is attached, externally, to the tuberosity of the scaphoid and the ridge on the trapezium ; internally, to the pisiform and unciform. Its upper border is continuous with the aponeurosis in front of the wrist ; its lower is connected with the palmar fascia ; its anterior surface receives the expanded tendon of the palmaris longus, and gives origin to most of the muscles of the ball of the thumb and little finger. Now proceed to the muscles composing the ball of the thumb and the little finger. The dissection of them requires considerable care. MUSCLES OF The great strength of the muscles of the ball of THE BALL OF the thumb is one of the distinguishing features of THE THUMB. fae numan hand. This strength is necessary in order to oppose that of all the fingers. In addition to its strength, the thumb enjoys perfect mobility. It has no less than eight muscles namely, an abductor, an opponens, two flexors, three extensors, and an adductor. ABDUCTOB This is the most superficial. It is a thin, flat POLLICIS. muscle, and arises from the ridge of the os trape- zium and the annular ligament. It passes forwards and outwards, MUSCLES OF THE BALL OF THE LITTLE FINGER. 359 and is inserted by a flat tendon into the radial side of the base of the first phalanx of the thumb. Its action is to draw the thumb away from the fingers. Its nerve comes from the median. Reflect it from its insertion to expose the following : OPPONENS This muscle arises from the front of the os tra- POLLICIS. pezium beneath the abductor, and from the annular ligament, and, passing forwards and outwards, is inserted into the whole length of the radial side of the metacarpal bone of the thumb. The action of this powerful muscle is to oppose the thumb to all the fingers. Its nerve comes from the median. Reflect it from its insertion, to expose the following : FLEXOR BBEVIS This muscle has two origins, between which POLLICIS. runs the tendon of the flexor longus pollicis : one, the superficial, from the annular ligament and trapezium ; the other, the deep, from the trapezoid, os magnum, the bases of the second and third metacarpal bones, and the sheath of the tendon of the flexor carpi radialis. It is inserted by two strong tendons into the base of the first phalanx of the thumb ; the superficial tendon being connected with the abductor pollicis, and the deep one with the adductor pollicis. A sesamoid bone is found in each of the tendons. The tendons of insertion of this muscFe are separated by the long flexor tendon of the thumb and the arteria magna pollicis. Its action is to bend the first phalanx of the thumb. The superficial portion is supplied by the median nerve ; the deep, by the ulnar. ADDUCTOR POL- This triangular muscle arises from the palmar LICIS. aspect of the shaft of the metacarpal bone of the middle finger ; its fibres converge and are inserted, along with the deep or inner portion of the flexor brevis pollicis, into the base of the first phalanx of the thumb and the internal sesamoid bone. Its action is to draw the thumb towards the palm, as when we bring the tips of the thumb and little finger into contact. It is supplied by the deep branch of the ulnar nerve, which also supplies the deep head of the flexor brevis pollicis. The other muscles of the ball of the thumb are supplied by the median nerve. MUSCLES OF THE The muscles of the little finger correspond in BALL OF THE some measure with those of the thumb. Thus LITTLE FINGER. there is an abductor, a flexor brevis, and an op- 360 MUSCLES OF THE BALL OF THE LITTLE FINGER. ponens minimi digiti. All derive their nerves from the deep branch of the ulnar. ABDUCTOB This, the most superficial of the muscles of the MINIMI DIGITI. little finger, arises from the pisiform bone, and from the tendinous expansion of the flexor carpi ulnaris : it is in- serted by a flat tendon into the inner side of the base of the first phalanx of the little finger. Its action is to draw this finger from the others. Its nerve comes from the deep branch of the ulnar. FLEXOR BBEVIS This slender muscle may be considered as a por- MINIMI DIGITI. tion of the preceding, to the radial side of which it is situated. It arises from the apex of the unciform bone and annular ligament, and is inserted with the tendon of the abductor into the base of the first phalanx of the little finger. Its action is similar to that of the abductor. Nerve from deep branch of ulnar. Between the origins of the abductor and flexor brevis minimi digiti, the deep branch of the ulnar artery and nerve sinks down to form the deep palmar arch. OPPONENS The last two muscles must be reflected from MINIMI DIGITI. their insertion, to expose the opponens minimi digiti. It arises from the unciform process and the annular liga- ment, and is inserted along the ulnar side of the shaft of the meta- carpal bone of the little finger. Its action is to draw this bone, the most moveable of all the metacarpal bones of the fingers, towards the thumb. Thus it greatly strengthens the grasp of the palm. Nerve from deep branch of ulnar. Cut vertically through the anterior annular ligament, and observe that, with the carpal bones, it forms an elliptical canal, with the broad diameter transversely. This canal is lined by a synovial membrane which is reflected loosely over the tendons. Superficial to the ligament pass the palmaris longus, the ulnar artery and nerve, the fibrous expansion from the flexor carpi ulnaris covering these vessels and nerve, and the palmar branch of the median and ulnar nerves ; beneath it pass the superficial and deep flexor tendons of the fingers, the long flexor tendon of the thumb, and the median nerve. The tendon of the flexor carpi radialis does not run with the other tendons, but is contained in a distinct sheath, lined by a separate synovial mem- MEDIAN NERVE IN THE PALM. 361 brane, formed, partly by the annular ligament, and partly by the groove in the trapezium. MEDIAN NERVE In its passage under the annular ligament, the IN THE PALM. median nerve is enveloped in a fold of synovial membrane, and lies upon the flexor tendons. Here it becomes enlarged and flattened, and of a pinkish colour, and divides into two nearly equal parts : the external gives a recurrent branch to the muscles of the ball of the thumb namely, to the abductor pollicis, the opponens pollicis, and the outer head of the flexor brevis pollicis, and then terminates in three digital nerves, two of which are distributed to the thumb, and the third to the radial side of the index finger ; the internal gives digital branches which supply the ulnar side of the forefinger, both sides of the middle finger, and the radial side of the ring finger. The two nerves to the thumb proceed, one on each side of the long flexor tendon, to the last phalanx : the outer one being connected with a terminal filament of the radial. The third digital nerve runs along the radial side of the index finger. The fourth descends towards the cleft between the index and middle fingers, and subdivides into two branches, which supply their opposite sides. The fifth is joined by a filament from one of the ulnar digital nerves, and then subdivides above the cleft between the middle and ring fingers, to supply their opposite sides. Two small branches are given off from the third and fourth digital nerves, to supply the two radial lumbricales ; the two ulnar being supplied by the ulnar nerve. About an inch and a quarter above the clefts between the fingers, each digital nerve subdivides into two branches, between which the digital artery passes and bifurcates lower down : therefore a vertical incision down the cleft would divide the artery before the nerve. In their course along the fingers and thumb, the nerves lie superficial to the arteries, and nearer to the flexor tendons. About the base of the first phalanx each nerve sends a dorsal Twancli, which runs along the back of the finger nearly to the extremity, communicating with the dorsal branches derived from the radial and ulnar nerves. 1 Near the ungual phalanx another dorsal or 1 Upon the cutaneous nerves of the hands and feet are little bodies, termed, after 362 FLEXOR TENDONS AND THEIR SHEATHS. ungual branch is distributed to the skin around and beneath the matrix of the nail. Each digital nerve terminates in the cushion at the end of the finger in a brush of filaments, with their points directed into the papillas of the skin. FLEXOK TEN- Immediately below the annular ligament the DONS AND THEIE tendons separate from each other : near the meta- SHEATHS. carpal joints they pass in pairs, through strong fibrous rings (p. 355) formed by the divisions of the palmar fascia. Below the metacarpal joint, the two tendons for each finger enter the sheath, theca, which confines them in their course along the phalanges. It is formed by a strong fibrous membrane, which is attached to the ridges on the phalanges, and converts the groove in front of these bones into a complete canal, exactly large enough to contain the tendons. The density of the sheath varies in par- ticular situations, otherwise there would be an obstacle to the easy flexion of the fingers. To ascertain this, cut open one of the sheaths along its entire length ; you will then see that it is much stronger between the joints than over the joints themselves. Through these sheaths inflammation, commencing in the integu- ments of the finger, may readily extend to the synovial membrane of the tendon. In cases of whitlow, when pus forms in the theca, the incision should be made deep enough to lay open this fibro-osseous canal, without which the incision will be of no use. It is obvious that the incision should be made down the centre of the finger, to avoid the digital nerves and arteries. If this opening be not timely their discoverer, corpuscles of Pacini. Some of them will be found, by carefully examining the trunk of a nerve, or one of its smaller branches, in the subcutaneous tissue at the root of a finger. Each corpuscle is about T ^th of an inch long, and is attached by a slender fibre-cellular pedicle to the nerve upon which it is situated ; through the pedicle, a single primitive nerve-fibril passes into the corpuscle. The corpuscle itself is composed of a series of concentric capsules, varying from twenty to fifty in number, and separated by intervals containing fluid : and the nerve- fibril terminates by a dilated extremity in a central cavity, which exists in the axis of the corpuscle. Their function is unknown. These bodies are found in many other situations, viz., in the solar plexus, the pudic nerves, the intercostal nerves, the cutaneous nerves of the arm and neck, the infra-orbital nerve, the sacral plexus, and in nerves supplying the periosteum. They can be best examined in the mesentery of the cat. FLEXOK TENDONS IN THE PALM. 363 made, the flexor tendons are likely to slough, and the finger becomes stiff. 1 But what protects the joints of the fingers where the flexor tendons play over them ? Look into an open sheath, and you will see that in front of the joints the tendons glide over a smooth fibro-cartilaginous structure called the palmar ligament. To facilitate the play of the tendons, the interior of the sheath, as well as the tendons, is lined by a synovial membrane, of the extent of which it is important to have a correct knowledge. With a probe you may ascertain that the synovial membrane is reflected from the sheath upon the tendons, a little above the metacarpal joints of the fingers that is, nearly in a line with the transverse fold in the skin in the lower third of the palm. Towards the distal end of the finger, the synovial sheath stops short of the last joint, so that it is not injured in amputation of the ungual phalanx. And now notice how the tendons are adapted to each other in their course along the finger. The superficial flexor, near the root of the finger, becomes slightly grooved to receive the deep flexor ; about the middle of the first phalanx it splits into two portions, through which the deep flexor passes. The two portions reunite below the deep tendon so as to embrace it, and then divide a second time into two slips, which interlace with each other, and are inserted into the sides of the second phalanx. The deep flexor, having passed through the opening of the superficial one, is inserted into the base of the last phalanx. 2 1 On closer inspection it will be observed that the sheath is composed of bands of fibres, which take different directions, and have received distinct names. The strongest are called the ligamenta vaginalia. They constitute the sheath over the body of the phalanx, and extend transversely from one side of the bone to the other. The ligamenta cruciata are two slips,, which cross obliquely over the tendons. The ligamenta annularia are situated immediately in front of the joints, and may be considered as thin continuations of the ligamenta vaginalia. They consist of fibres, which are attached on either side to the lateral ligaments of the joints, and pass transversely over the tendons. 2 In the Museum of the College of Surgeons, a preparation is put up which shows a beautiful piece of animal mechanics concerning the flexor tendons ; namely, that in its passage along the phalanges, the deep flexor forms, at the first phalanx, a kind of little patella for the superficial one ; but, at the second phalanx, the superficial flexor lies deeper than the other, and forms a little patella for it. This increases the leverage in each case. 364 LUMBRICALES. In what way are the tendons supplied with blood ? Raise and separate the tendons, and you will see that slender but very vas- cular folds of synovial membrane (yincula.' tendinurn) run up from the phalanges and convey blood-vessels to the tendons. The tendon of the flexor longus pollicis lies on the radial side of the other tendons beneath the annular ligament. It passes between the two portions of the flexor brevis pollicis and the two sesamoid bones of the thumb, enters its proper sheath, and is inserted into the base of the last phalanx. Its synovial sheath is prolonged from the large bursa of the flexor tendons beneath the annular ligament, and accompanies the tendon down to the last joint of the thumb ; consequently the sheath is injured in amputation of the last phalanx. BUKSAL SAC OF A large and loose synovial sac (bursa of the THE CAKPTJS. carpus) facilitates the play of the tendons beneath the anterior annular ligament. It lines the under surface of the ligament and the groove of the carpus, and is reflected in loose folds over the tendons. It is prolonged up the tendons for an inch and a half, or two inches, and forms a cul-de-sac above the liga- ment. Below the ligament the bursa extends into the palm, and sends off prolongations for each of the flexor tendons, which accom- pany them down to the middle of the hand. You will understand that, when the bursa is inflamed and distended by fluid, there will be a bulging above the annular ligament, and another in the palm, with perceptible fluctuation between them ; the unyielding liga- ment causing a constriction in the centre. 1 These four slender muscles, one for each finger, are attached to the deep flexor tendons in the palm. All of them arise by fleshy fibres from the radial side and palmar surface of the deep tendon of their corresponding finger : the third and fourth also arise from the adjacent sides of two ten- dons. Each terminates in a broad thin tendon which passes over 1 In only one subject have we seen an instance in which this bursa communi- cated with the wrist-joint. It communicates always with the synovial sheath of the long flexor of the thumb, in most cases with that of the flexors of the little finger, and but rarely with that of the index, middle, and ring fingers. For this reason, inflammation of the theca of the thumb or little finger is more liable to be attended with serious consequences than either of the others. RADIAL AKTERY IN THE PALM. 365 the radial side of the first joint of the finger, and is inserted, by a broad expanded aponeurosis, into the extensor tendon on the dorsal aspect of the first phalanx of the finger. Their action is to bend the metacarpo-phalangeal joint of the fingers. Being inserted near the centre of motion, they can move the fingers with great rapidity. As they produce the quick motions of the musician's fingers, they were called by the old anatomists fidicinales. The two ulnar lumbricales are supplied by the deep branch of the ulnar nerve ; the two radial by the third and fourth digital branches of the median nerve. Now cut through all the flexor tendons, and re- move the deep fascia of the palm, to see the deep arch of arteries and its branches. 1 BRA HE F artery, sinking into the space between THE KADIAL AR- the first and second metacarpal bones, and between TERY IN THE the two heads of the abductor indicis, enters the PALM * palm between the inner head of the flexor brevis and the adductor pollicis, and gives off three branches the arteria princeps pollicis, the radialis indicis, and the palmaris profunda, which unites with the deep ulnar artery to form the deep arch. The arteria princeps pollicis runs behind the deep head of the flexor brevis pollicis and in front of the abductor indicis (first dorsal inter- osseous), close along the metacarpal bone of the thumb : in the interval between the lower portions of the flexor brevis pollicis, the artery divides into two digital branches, which proceed one on either side of the thumb, and inosculate at the apex of the last phalanx. Their distribution and mode of termination are like those of the other digital arteries. The arteria radialis indicis runs between the abductor indicis and adductor pollicis, along the radial side of the index finger to the end, where it forms an arch with the other digital artery, a branch of the ulnar. Near the lower margin of the adductor pollicis, the radialis indicis generally receives a branch from the princeps pollicis, and gives a branch to the superficial palmar arch. The palmaris profunda may be considered as the continuation 1 The course and relations of the radial artery as it winds round the wrist will be described in the dissection of the back of the hand. 366 MUSCLES OF THE BACK CONNECTED WITH THE ARM. of the radial artery. It enters the palm between the inner head of the flexor brevis and the adductor pollicis, and, running upon the bases of the metacarpal bones, inosculates with the deep branch of the ulnar artery, thus completing the deep palmar arch. From the concavity of the arch small recurrent branches ascend to supply the bones and joints of the carpus, inosculating with the other carpal arteries. From the convexity of the arch three or four small branches, called palmar interosseous (fig. 83, p. 356), descend to supply the interosseous muscles, and near the clefts of the fingers communicate with the digital arteries. These palmar interosseous branches are sometimes of consider- able size, and take the place of one or more of the digital arteries, ordi- narily derived from the superficial palmar arch. Three branches, called perforating, pass between the upper ends of the metacarpal bones to the back of the hand, and communicate with the carpal branches of the radial and ulnar. DEEP BRANCH This nerve sinks into the palm with the ulnaris OP THE ULNAR profunda artery, between the abductor and flexor NERVE - brevis minimi digiti. It then runs with the deep palmar arch towards the radial side of the palm, and terminates in the adductor pollicis, in the inner or deep head of the flexor brevis pollicis, and in the first dorsal interosseous. Between the pisiform and unciform bones, the nerve gives a branch to each of the muscles of the little finger. Subsequently it sends branches to each inter- osseous muscle and to the two inner lumbricales. The tendon of the flexor carpi radialis in the palm must now be followed to its insertion into the base of the second metacarpal bone. The dissection of the remaining muscles of the palm, called, from their position, interossei, must be, for the present, postponed. MUSCLES OF THE BACK CONNECTED WITH THE AEM. Make an incision down the middle of the spine DISSECTION from the occiput to the sacrum ; another, from the last dorsal vertebra upwards and outwards to the acromion ; and a CUTANEOUS NERVES OF THE BACK. 367 third, from the sacrum along the crest of the ilium ; then reflect the skin outwards from the dense subcutaneous tissue, in which will be found the following cutaneous nerves. CUTANEOUS These are derived from the posterior divisions of NERVES OF THE the spinal nerves, and correspond, generally, to the JBACK - number of the vertebrae. The posterior primary branches, much smaller than the anterior, divide, between the transverse processes, into external and internal branches, with the exception of the suboccipital, the fourth and fifth sacral, and the coccygeal nerves. POSTERIOR The posterior primary branches of the cervical BRANCHES OF THE nerves (except the first *) divide into external and CERVICAL NERVES, internal branches : the external are distributed solely to some of the muscles of the neck, and which will be dis- sected later on ; the internal, larger than the external, are distri- buted in the following manner : the second, or the great occipital nerve, perforates the complexus, and ramifies on the back of the scalp with the occipital artery ; the third, fourth, and fifth nerves, after sending branches to the multifidus spinae, semi-spinalis, and the complexus, emerge through the trapezius close to the spinous processes, and there pass transversely across that muscle to supply the skin over it ; the branch of the third cervical nerve sometimes sends a branch to the back of the scalp ; 2 the branches of the sixth, seventh, and eighth are small, and are situated beneath the semi- spinalis, to which they are distributed. POSTERIOR The external branches become superficial between BRANCHES OF THE the longissimus dorsi and the ilio-costalis, and sup- DORSAL NERVES. p] v these muscles and the other divisions of the erector spinse ; the six lower supply cutaneous nerves in the line of the angles of the ribs. The internal branches, as to the upper six dorsal, emerge between the multifidus spinae and semi-spinalis, and passing horizontally outwards, end in branches to the skin close to the spinous processes ; that from the second ramifies over the spine 1 This nerve has already been described in the dissection of the suboccipital triangle (p. 290). 2 The internal branches of the first, second and third cervical nerves form a communication beneath the complexus, which is called by Cruveilhier the posterior cervical plexus. 368 NERVES OF THE BACK. of the scapula ; the six lower do not become cutaneous, but ter- minate in the multifidus spinae. POSTERIOR The external brandies from the first, second, and BRANCHES OF THE third lumbar nerves perforate the ilio-costalis and LUMBAR NERVES. ^he l a tissimus dorsi, and then descend over the crest of the ilium, supplying cutaneous branches to the gluteal region ; the fourth supplies the erector spinse without becoming cutaneous ; the fifth sends down a branch to communicate with the first sacral nerve. The internal brandies are small, and end in the multifidus spinse. POSTERIOR T ne Vernal brandies of the upper three sacral BRANCHES OF THE nerves form a series of loops with themselves, and SACRAL NERVES. a } go w ^] 1 th e i as ^ lumbar above and the fourth sacral below ; they pass to the superficial surface of the great sacro- sciatic ligament, where they form another series of loops, from which filaments are distributed to the skin after piercing the gluteus maximus. The internal brandies of the three upper sacral nerves are distributed to the multifidus spinge. The posterior branches of the fourth and fifth sacral nerves do not divide into external and internal branches, but form a loop, the lower one being joined with the coccygeal nerve. COCCYGEAL The posterior division of this nerve, after being NERVE. joined by a branch from the last sa.cral, is distri- buted to the posterior aspect of the coccyx. The trapezius and latissimus dorsi, which form the first layer of muscles, must now be .cleaned by putting them on the stretch, and reflecting the connective tissue which covers them ; they should then be dissected in the course of their fibres. Alone, this muscle is triangular ; with its fel- TRAPEZIUS low, it presents a trapezoid form. It arises from the inner fourth, more or less, of the 'superior curved line of the occiput, from the ligamentum nuchas, 1 from the spinous processes 1 The ligamentum nuchae is, in man, only a rudiment of the great elastic liga- ment which supports the weight of the head in quadrupeds. It extends from the spine of the occiput to the spines of all the cervical vertebra, except the atlas ; otherwise it would impede the free rotation of the head. In the giraffe this liga- FIG. 84. 369 a, n, Small occipital nerve from the cervical plexus ; 1, external muscular branches of the first cer- vical nerve and union by a loop with the second ; 2, the rectus capitis posti- cus major, with the great occipital nerve passing round, the short muscles and piercing the corn- plexus ; the external branch is seen to the outside ; 2', the great occi- pital ; 3, external branch of the posterior primary division of the third nerve ; 3', its internal branch, or third occipital nerve ; 4', 5', 6', 7', 8', internal branches of the several corresponding nerves on the left side ; the external branches of these nerves proceeding to muscles are displayed on the right side : d 1 to d 6, and thence to d!2, ex- ternal muscular branches of the posterior primary divisions of the twelve dorsal nerves on the right side ; d 1', to d 6', the in- ternal cutaneous branches of the six upper dorsal nerves on the left side; d T to d 12', cutaneous branches of the six lower dorsal nerves from the ex- ternal branches ; I, I, ex- ternal branches of the pos- terior primary branches of several lumbar nerves on the right side piercing the muscles, the lower descending over the glu- teal region ; /', I', the same more superficially on the left side ; s, , on the right side, the issue and union by loops of the posterior primary divisions of four sacral nerves ; i', s 1 , some of these distributed to the skin on the left side. DIAGRAM OF THE CUTANEOUS NERVES OF THE BACK. (Quain.) B B 370 TRAPEZIUS. of the seventh cervical, and all the dorsal vertebrae, and from their supraspinous ligament. The fibres converge towards the shoulder. The upper pass downwards and outwards, and are inserted by fleshy fibres into the external third of the clavicle ; the middle pass transversely outwards into the inner border of the acromion and the superior lip of the spine of the scapula; the lower pass upwards and outwards, and terminate in a thin tendon, which plays over the triangular surface at the back of the scapula, and is inserted into the beginning of the spine. The insertion of the trapezius exactly corresponds to the origin of the deltoid, and the two muscles are connected by a thin aponeurosis over the spine and acromion. If both the trapezius muscles be exposed, observe that, between the sixth cervical and the third dorsal vertebrae, their origin presents an aponeurotic space of an elliptical form (p. 371, fig. 85). The structures covered by the trapezius are : the splenius, the complexus, the levator anguli scapulas, the rhomboidei minor and major, the supraspinatus, a small part of the infraspinatus, the serratus posticus superior, the vertebral aponeurosis, the latissimus dorsi, the ilio-costalis, the spinal accessory nerve, and the super- ficialis colli artery. The fixed point of the muscle being at the vertebral column, all its fibres tend to raise the shoulder. The deltoid cannot raise the humerus beyond an angle of ninety degrees : beyond this, the elevation of the arm is principally effected by the rotatory move- ment of the scapula. The trapezius is in strong action when a weight is borne upon the shoulders ; again, its middle and inferior fibres act powerfully in drawing the scapula backwards, as in pre- paring to strike a blow. If both muscles act, they draw the head backwards ; if one only acts, it draws the head to the same side. It is supplied by the nervus accessorius and the deep branches of the cervical plexus, and by the superficialis colli artery. LATISSIMUS This broad flat muscle occupies the lumbar and DOBSI. lower dorsal regions, and thence extends to the arm, where it forms part of the posterior boundary of the axilla. It arises from the posterior third of the external lip of the crest ment is six feet long, and as thick as a man's forearm. Professor Quekett states that when divided it shrinks at least two feet. SUPERFICIAL MUSCLES OF THE BACK. FIG. 85. 371 THE SUPERFICIAL MUSCLES 372 LATISSIMUS DORSI. of the ilium, from the spinous processes of the two upper sacral, all the lumbar and the six lower dorsal vertebrae, and their supra- spinous ligament, by a strong aponeurosis ; and, lastly, from the three or four lower ribs by fleshy slips, which interdigitate with those of the external oblique muscle of the abdomen. All the fibres converge towards the axilla, where they form a thick muscle, which curves over the inferior angle of the scapula, and is inserted by a broad, flat tendon into the bottom of the bicipital groove of the humerus. The upper fibres are inserted into the lowest of the groove, the lower fibres into the upper part. The tendon is about two inches broad, and lies in front of, and higher than that of the pectoralis major and of the teres major, from which it is separated by a large lursa. 1 It is supplied mainly by the long subscapular nerve, .also by the posterior branches of the dorsal and lumbar nerves. The latissimus dorsi draws the humerus inwards and back- wards; rotating it also inwards. It co-operates with the pectoralis major in pulling any object towards the body : if the humerus be the fixed point, it raises the body, as in climbing. The object of the muscle arising so high up the back is, that the transverse fibres of the muscle may strap down the inferior angle of the scapula. It sometimes happens that the scapula slips above the muscle : this displacement is readily recognised by the unnatural projection of the lower angle of the bone, and the impaired move- ments of the arm. 2 The muscle covering the latissimus dorsi is thetrapezius above; those lying beneath it are, a small part of the rhomboideus major, of the infraspinatus, and of the teres major, the serratus posticus inferior, the spinalis dorsi, the longissimus dorsi, the ilio-costalis, and the external intercostals. Between the base of the scapula, 1 The latissimus dorsi frequently receives a distinct accessory slip from the inferior angle of the scapula. 2 We have seen several instances of this displacement. There is great pro* jection of the inferior angle of the scapula, especially when the patient attempts to raise the arm. He cannot raise the arm beyond a right angle, unless firm pres- sure is made on the lower angle of the scapula, so as to supply the place of the muscular strap. Whether the scapula can be replaced or not, a firm bandage should be applied round the chest. SPINAL ACCESSORY NERVE. 373 the trapezius, and the upper border of the latissimus dorsi, a tri- angular space is observed when the arm is raised, in which the lower fibres of the rhomboideus major and part of the sixth in- tercostal space are exposed. Immediately above the crest of the ilium, between the free margins of the latissimus dorsi and external oblique, there is, also, an interval in which a little of the internal oblique can be seen. LUMBAB OB This dense shining aponeurosis of the back VERTEBRAL (sometimes termed the aponeurosis of the latissi- APONEUROSIS. mus d ors i) forms the posterior part of the sheath of the erector spinas. It is pointed above, where it is continuous with the deep cervical fascia, broader and stronger below. It consists of tendinous fibres, which are attached internally to the spines of the dorsal, all the lumbar and sacral vertebrae ; exter- nally, to the angles of the ribs ; and inferiorly it is blended with the tendons of the serratus posticus inferior and latissimus dorsi. When suppuration takes place in the loins, constituting a lumbar abscess in connection with spinal disease, the pus is seated beneath this aponeurosis, and is therefore tardy in coming to the surface. Reflect the trapezius from its insertion. On its DISSECTION under surface see the ramifications of its nutrient artery, the superficialis colli, a branch of the posterior scapular. A large nerve, the spinal accessory, enters its under surface near the clavicle, and divides into filaments, which, reinforced by fila- ments from the third and fourth cervical nerves, are distributed to the muscle as far as its lower border. SPINAL ACCES- This nerve, the eleventh cerebral nerve, arises ,SOBY NERVE. by two roots the accessory and the spinal por- tions : the former from the medulla oblongata, the latter from the spinal cord. The accessory portion, the smaller, arises by four or five filaments from a grey nucleus in the floor of the fourth ventricle, below the origin of the pneumogastric nerve ; the spinal portion arises from the lateral part of the cervical portion of the spinal cord by several filaments, some of which arise as low as the sixth cervical vertebra, and which may be traced into the grey matter of the anterior horn. Formed by the union of these roots, the nerve -enters the skull through the foramen magnum, and leaves it again, 874 RHOMBOIDEI. with the accessory portion, through the foramen jugulare. These portions communicate external to the skull ; but while the acces- sory root joins the vagus, the spinal portion, in the main, runs behind the internal jugular vein, traverses obliquely the upper third of the sterno-mastoid muscle, and crosses the posterior triangle of the neck to the trapezius, which it supplies (p. 74). In front of the trapezius it is joined by branches from the third, fourth, and fifth cervical nerves, together with which it communicates with the posterior branches of the spinal nerves. The trapezius should now be cut through the middle, and the inner half turned inwards towards the spine, the outer half over the clavicle and the spine of the scapula. Beneath the trapezius we have to examine the second layer, consisting of three muscles connected with the scapula ; namely, the levator anguli scapulae, the rhomboideus major and minor. The scapula should be adjusted so as to stretch their fibres. LEVATOR This muscle is situated at the back and side of ANGULI SCAPULA. the neck. It arises by four tendons from the posterior tubercles of the transverse processes of the four upper cervical vertebrae. The muscular slips to which the tendons give rise form a single muscle, which descends outwards along the side of the neck, and is inserted into the posterior border of the scapula between its spine and superior angle. Its action is to raise the posterior angle of the scapula ; as, for instance, in shrugging the shoulders. Its nerve comes from the fifth cervical, and by fila- ments from the external series of the deep cervical plexus, which come from the third and fourth cervical nerves. BHOMBOIDEUS These flat muscles extend from the spinous MAJOR AND processes of the vertebrae to the base of the scapula. MlNOK< They often appear like a single muscle. The rhomboideus minor, the higher of the two, arises by a thin apo- neurosis from the spinous processes of the last cervical and the first dorsal vertebrae, and is inserted into the base of the scapula oppo- site its spine. The rhomboideus major arises by tendinous fibres from the spinous processes of the four or five upper dorsal vertebras and the supraspinous ligament, and is inserted by fleshy fibres into the base of the scapula between its spine and inferior angle ;. SUPRASCAPULAR ARTERY. 375 the larger number of the fibres being inserted into a tendinous arch, which is chiefly attached to the inferior angle. The action of these muscles is to draw the scapula upwards and backwards. They are the antagonists of the serratus magnus. The nerve of the rhomboid muscles (posterior scapular) is a branch of the fifth cervical. It passes outwards beneath the lower part of the levator anguli scapulae, to which it sends a branch, and is lost in the under surface of the rhomboidei. This muscle extends from the scapula to the OMO-HYOIDEUS. , . -, -, . , , -. os hyoides, and consists 01 two long narrow mus- cular portions, connected by an intermediate tendon beneath the sterno-mastoid. The posterior portion only can be seen in the pre- sent dissection. It arises from the upper border of the scapula, close behind the notch, and from the transverse ligament above the notch. Thence the slender muscle passes forwards across the lower part of the neck, beneath the sterno-mastoid, where it changes its direc- tion and ascends nearly vertically, to be attached to the os hyoides at the junction of the body with the greater cornu (p. 79). Thus the two portions of the muscle form, beneath the sterno-mastoid, an obtuse angle, of which the apex is tendinous, and of which the angular direction is maintained by a layer of fascia, proceeding from the tendon to the first rib and the clavicle. Its action is to depress the os hyoides. Its nerve comes from the descendens noni and the communicantes noni (p. 110). SUPRASCAPDLAR This artery (transversalis hunieri), a branch of ARTERY. the thyroid axis (p. 121), runs behind andparalle 1 with the clavicle, over the lower end of the scalenus anticus and subclavian artery, and beneath the sterno-mastoid and omo-hyoid muscles, to the upper border of the scapula, where it usually passes above the ligament bridging over the notch. It ramifies in the supraspinous fossa, supplying the supraspinatus, and then passes under the acromion to the infraspinous fossa, where it inosculates freely with the dorsalis scapulas, a branch of the subscapular. It sends off a. The inferior sterno-mastoid artery -to the sterno-mastoid and contiguous muscles ; b. the siipra-a,cromial branch, which ramifies upon the acromion, anastomosing with the other acromial arteries 376 POSTERIOR SCAPULAR NERVE. derived from branches of the axillary ; c. a small subscapular branch to the fossa of the same name ; d. articular arteries to the shoulder- joint ; and, lastly, e. the infraspinotis branch, which anastomoses with the dorsalis scapulae. The suprascapular vein terminates either in the subclavian or in the external jugular. The suprascapular nerve, a branch of the fifth and sixth cer- vical nerves, runs with the corresponding artery, and, after pass- ing through the suprascapular notch, is distributed to the supra- spinatus and infraspinatus. In the supraspinous fossa, this nerve sends a small articular branch to the shoulder-joint ; in the infra- spinous fossa it gives off two branches to the infraspinatus, and some to the shoulde'r-joint. POSTERIOR This artery is one of the divisions of the trans- SCAPDLAR versa! is colli, but comes very frequently from the ARTERY. subclavian in the third part of its course (p. 121). It runs across the lower part of the neck, above, or between the nerves of the brachial plexus, towards the posterior superior angle of the scapula. Here it pursues its course along the posterior border of the scapula beneath the levator angulis capulse and the rhomboidei, anastomosing with branches of the suprascapular and subscapular arteries, and with branches from the intercostal arteries. The corresponding vein joins the external jugular or the subclavian. Divide the rhomboid muscles near their inser- tion, and trace the artery to the inferior angle of the scapula, where it terminates in the rhomboidei, serratus magnus, and latissimus dorsi. Numerous muscular branches arise from the posterior scapular. The superftcialis colli (the other division of the transversalis colli) is given off near the upper angle of the scapula for the supply of the trapezius, which it enters together with the spinal accessory nerve. Divide and reflect the latissimus dorsi below the inferior angle of the scapula, and draw the scapula forcibly outwards, to have a more perfect view of the extent of the serratus magnus than was seen in the axilla. The abundance of connective tissue in this situation is necessary for the play of the scapula on the chest. SERRATUS MAGNUS. 377 SEEEATUS . This broad, thin, flat muscle intervenes between MAGNUS. the scapula and the ribs. It arises by nine fleshy digitations from the eight upper ribs, each rib giving origin to one, and the second to two, and from the fascia covering the correspond- ing intercostal spaces. The four lower digitations correspond with those of the external oblique muscle of the abdomen. The fibres pass backwards and outwards and are arranged in three fasciculi ; the upper portion arises from the first and second ribs and the fascia between them, and is inserted into the triangular surface in front of the upper angle of the scapula ; the middle portion arises from the second, third, and fourth ribs, and is inserted into the inner lip of the vertebral border between the first and third por- tions ; the third portion arises from the fifth, sixth, seventh, and eighth ribs, and is inserted into the smooth surface in front of the inferior angle; this last portion consists of four serrations, and are those which interdigitate with the external oblique. This is the most important of the muscles which regulate the movements of the scapula. It draws the scapula forwards, and thus gives additional reach to the arm ; it counteracts all forces which tend to push the scapula backwards ; for instance, when a man falls forwards upon his hands, the serratus magnus sustains the shock, and prevents the scapula from being driven back to the spine. Supposing the fixed point to be at the scapula, some anatomists ascribe to it the power of raising the ribs ; hence Sir Charles Bell called it the external respiratory muscle, the internal respiratory muscle being the diaphragm. The nerve which supplies it is a branch of the fifth and sixth cervical nerve : it descends along its outer surface, distributing a filament to each digitation of the muscle (p. 126). Divide the serratus magnus near the scapula, and remove the arm by sawing through the middle of the clavicle, cutting through the axillary vessels and nerves. These should be tied to the coracoid process. After the removal of the arm, examine the precise insertions of the preceding muscles. 378 DISSECTION OF THE MUSCLES OF THE SHOULDER. DISSECTION OF THE MUSCLES OF THE SHOULDEB. DISSECTION. The remainder of the skin over the shoulder is to be reflected, and in the subcutaneous tissue are found the cutaneous vessels and nerves. Some pass down over the shoulder, others ascend over the deltoid, emerging from beneath its lower border. The acromial branches come from the third and fourth cervical FIG. 86. 1. Supra-aoromial br. of the cervical nerves. 2. Ascending and descend- ing brs. of the circum- flex n. 3. 4. Cutaneous brs. of the musculo-cutaneous u. 5. Internal cutaneous br.of musculo-spiral n. 6. Intercosto-humeral brs. 7. Filaments of the lesser internal cutaneous n. 8. Posterior cutaneous br. of internal cuta- neous n. 9. Branch of internal cu- taneous n. CUTANEOUS NEEVES OF THE LEFT SHOULDER AND ARM. (POSTERIOR VIEW.) nerves, and descend over the acromion (fig. 86) in front of, and behind, the deltoid. The cutaneous branch of the circumflex nerve comes out beneath the posterior border of the deltoid, and supplies the skin over the posterior and outer two-thirds of the THE DELTOID. 379 muscle ; others perforate the muscle, each accompanied by a small artery. Notice the strong layer of fascia upon the surface of the deltoid, which extends from the aponeurosis covering the muscles on the back of the scapula, and is continuous with the fascia of the arm. It dips down between the fibres of the muscle, dividing it into large bundles. This fascia is to be removed, by putting the deltoid on the stretch, and reflecting it in the direction of its fibres, begin- ning from the front. The fascia will be seen to be continuous in front with the fascia covering the pectoralis major: above, it is attached to the clavicle and spine of the scapula ; behind, it is continuous with that over the infraspinatus. The large muscle which covers the shoulder- joint is named deltoid, from its resemblance to the Greek A reversed. It arises from the external third of the anterior border of the clavicle, from the apex and outer border of the acro- mion, and from the lower border of the spine of the scapula down to the triangular surface at its root. This origin, which corresponds to the insertion of the trapezius, is tendinous and fleshy everywhere, except at the commencement of the spine of the scapula, where it is simply tendinous, and connected with the infraspinous aponeu- rosis. The muscular fibres descend, the anterior backwards, the posterior forwards, the middle perpendicularly ; all converge to a tendon which is inserted into a rough surface on the outer side of the humerus, a little above the middle of the shaft. The insertion of the tendon extends one inch and a half along the humerus, and terminates in a y-shaped form, the origin of the brachialis anticus embracing it on either side. Sometimes a few fibres of the pecto- ralis major are connected with its front border. The muscular bundles composing the deltoid have a peculiar arrangement : a peculiarity arising from its broad origin and its narrow insertion. It consists in the interposition of tendons between the bundles for the attachment of the muscular fibres. The annexed woodcut shows this arrangement better than any description. The action of the muscle is not only concentrated upon one point, but its power is also greatly increased by this arrangement. 380 STRUCTURES COVEKED BY THE DELTOID. FIG. 87. ACTION OF THE It raises the arm ; but it cannot do so beyond DELTOID. an angle of ninety degrees. The elevation of the arm beyond this angle is effected through .the raising of the shoulder by the trapezius and serratus magnus. Its anterior fibres draw the arm forwards ; its posterior, backwards. This powerful muscle is sup- plied with blood by the anterior and posterior circumflex, the thor- acica humeraria, the thoracica acro- niialis, all from the axillary artery ; also by the deltoid branch of the brachial. Its nerve is the circum- flex. The rotundity of the shoulder is due, not so much to the deltoid as to the upper end of the humerus. When the head of the humerus is dislocated into the axilla, the fibres of the muscle run vertically to their insertion ; hence the flattening of the deltoid, and the greater pro- minence of the acromion. It is below the deltoid that an ununited fracture of the humerus is most commonly met with, owing to the muscle displacing the upper fragment. Reflect the deltoid from its origin, and turn it downwards. Observe the ramifications of the cir- cumflex nerve and the anterior and posterior circumflex arteries on its under surface ; notice also the large bursa between it and the tendons inserted into the great tuberosity of the humerus. PAKTS COVERED The structures seen on reflecting the deltoid are BY THE DELTOID. as follows : the bursa already alluded to, the cora- coid process, the coraco-acromial ligament, the origins of the biceps and coraco-brachialis, the insertions of the pectoralis minor and major, the long head of the biceps, the insertions of the supra- spinatus, infraspinatus, and teres minor, the long and external ANALYSIS OF THE DELTOID. DISSECTION. CIRCUMFLEX NERVE. 381 heads of the triceps, the circumflex vessels and nerve, and the neck and upper part of the humerus. BUBSA UNDER The large bursa under the deltoid extends for THE DELTOID, OR some distance beneath the acromion and the coraco- SUB-ACROMIAL. acromial ligament, and covers the tendons attached to the great tuberosity of the humerus. It communicates, very rarely, with the shoulder-joint. Its use is to facilitate the move- ments of the head of the bone under the acromial arch. POSTERIOR This artery is given off from the axillary in the CIRCUMFLEX third part of its course ; it runs behind the surgical ARTERY. neck of the humerus, through a quadrilateral open- ing, bounded above by the subscapularis and teres minor ; below, by the teres major ; externally, by the neck of the humerus ; and internally, by the long head of the triceps (p. 318). Its branches terminate on the under surface of the deltoid, anastomosing with the anterior circumflex, acromial thoracic, and suprascapular arteries. From the posterior circumflex, a branch descends in the sub- stance of the long head of the triceps, to inosculate with the supe- rior profunda : this is one of the channels through which the circulation would be carried on, if the axillary were tied in the last part of its course. CIRCUMFLEX This nerve, a branch of the posterior cord of the NERVE, axillary plexus, runs with the posterior circumflex artery, through the same quadrilateral space, and then divides into two branches an upper and a lower. The upper branch winds round the neck of the humerus, and supplies the anterior part of the deltoid, and gives off cutaneous branches to supply the skin over its lower part. The lower branch sends a filament to the teres minor, one or two to the integuments over the shoulder at its pos- terior part, and terminates in the substance of the deltoid. It also distributes an articular filament, which enters the shoulder-joint in front, below the subscapularis. The proximity of this nerve to the head of the humerus ex- plains the occasional paralysis of the deltoid, after dislocation or fracture of the humerus. The nerve is liable to be injured, if not actually lacerated, by the pressure of the bone. In the summer of 1840, a man was admitted into the hospital with a severe injury 382 TERES MAJOR AND MINOR. to the shoulder, and died of delirium tremens. On examination the humerus was found broken high up, the capsule of the joint opened, and the circumflex nerve torn completely across. 1 * A strong aponeurosis covers the muscles of the dorsum of the scapula, and is firmly attached to the spine and borders of the bone. At the posterior edge of the deltoid, it divides into two layers, one of which passes over, the other under, the muscle. Remove the aponeurosis, so far as it can be done without injury to the muscular fibres which arise from its under surface. INFBA- This triangular muscle arises by fleshy fibres from SPINATUS. the posterior two-thirds of the infraspinous fossa, by tendinous fibres from the ridges on the fossa, and from the apo- neurosis which covers it. The fibres converge to a tendon, which is at first contained in the substance of the muscle, and then proceeds, over the capsular ligament of the shoulder-joint, to be inserted into the middle depression on the greater tuberosity of the humerus. Its nerve comes from the suprascapular. This long narrow muscle is situated below the infraspinatus, along the inferior border of the scapula. It arises from the dorsum of the scapula close to the inferior border, and from the intermuscular septa between it and the infraspinatus above and the teres major below. The fibres ascend outwards parallel with those of the infraspinatus, and ter- minate in a tendon, which passes over the capsular ligament of .the shoulder-joint, and is inserted into the lowest depression on the great tuberosity of the humerus, and by muscular fibres into the bone below it. It is supplied by a branch of the circumflex nerve, which enters the muscle at its lower border, and it has (usually) a small ganglion-like enlargement upon it. The action of the infraspinatus and teres minor is to rotate the humerus outwards, and when the arm is raised it draws the humerus downwards and backwards. This muscle is closely connected with the latis- TEEKS MAJOR. . . . . simus dorsi, and extends from the inferior angle of the scapula to the humerus, contributing to form the posterior boundary of the axilla. It arises from the flat surface on the dorsal 1 See preparation in Museum of St. Bartholomew's Hospital. SUBSCAPULARIS. 383 aspect of the inferior angle of the back of the scapula, from its inferior border, and the intermuscular septa, and terminates upon a flat tendon, nearly two inches in breadth, which is inserted into the inner edge of the bicipital groove of the humerus, behind and a little lower than the tendon of the latissimus dorsi. Its action is to draw the humerus backwards and downwards when the arm is raised, and to rotate it slightly inwards. It is supplied by the middle subscapular nerve, which enters it on its axillary aspect. A bursa is found in front of, and another behind, the tendon of the teres major ; the former separates it from the latissimus dorsi, the latter from the bone. g UPEA . This muscle arises from the posterior two-thirds SPINATUS. of the supraspinous fossa, and from its aponeurotic covering. It passes under the acromion, over the capsular liga- ment of the shoulder-joint, and is inserted by a strong tendon into the superior depression on the greater tuberosity of the humerus. To see its insertion, the acromion should be sawn off near the neck of the scapula. Its action is to assist the deltoid in raising the arm. It is supplied by two branches derived from the supra- scapular nerve. This triangular fleshy muscle occupies the sub- SUBSCAPULARIS. ~\ C TM- f 4/L il scapular fossa. It arises from the posterior three- fourths of the fossa, except the posterior border and angles which give attachment to the serratus magnus, and from three or four tendinous septa attached to the oblique bony ridges on its surface. The fibres, passing upwards and outwards, converge towards the neck of the scapula, where they terminate upon three or four tendons, which are concealed amongst the muscular fibres, and are inserted into the lesser tuberosity of the humerus and into the bone for an inch below the tuberosity. Its broad insertion is closely con- nected with the capsule of the shoulder-joint, which it completely protects upon its inner side. Its action is to rotate the humerus inwards, and, when the arm is raised, draws it downwards. The nerves which supply it come from the long and middle subscapular nerves. The coracoid process, with the coraco-brachialis and short head of the biceps, forms an arch, under which the tendon of the sub- 384 ARTERIES OF THE SCAPULA. scapularis plays. There are several bursce about the tendon. One r of considerable size, on the upper surface of the tendon, facilitates its motion beneath the coracoid process and the coraco-brachialis : this sometimes communicates with the large bursa under the del- toid. Another is situated between the tendon and the capsule of the joint, and almost invariably communicates with it. DIAGRAM OF ARTERIES OF SCAPULA. 1. Suprascapular artery. 2. Posterior circumflex a. 3. Infraspinous br.of suprascapular a. 4. Dorsalis scapulas a. 5. Posterior scapular a. 6. Subclavian a. DISSECTION. Now reflect the muscles from the surfaces of the scapula, to trace the arteries which ramify upon it. CONTINUATION Tllis artei 7> a branch of the thyroid axis, runs OF SUPRASCAPU- under and parallel with the clavicle, and passes LAR ARTERY AND above, the notch of the scapula, into the supra- spinous fossa; it sends a branch to the supra- NERVE. TRICEPS. 385 spinatus, another to the shoulder-joint, and then descends behind the neck of the scapula into the fossa below the spine, where it inosculates directly with the dorsalis scapulge. Its branches ramify upon the bone, and supply the infraspinatus and teres minor (fig. 88). The suprascapular nerve passes most frequently through the notch of the scapula, accompanies the corresponding artery, sup- plies two branches to the supraspinatus and one to the shoulder- joint ; it then enters the infraspinous fossa, to terminate in the infraspinatus. DOKSALIS This artery, after passing through the triangular SCAPTJUE AKTEEY. space (p. 318), curves round the inferior border of the scapula, which it grooves, to the infraspinous fossa, where it ascends close to the bone, and anastomoses with the supra- and posterior scapular arteries. Another branch of the subscapular artery runs between the teres minor and major towards the inferior angle of the scapula, where it anastomoses with the posterior scapular artery (fig. 88). The several communications about the scapula between the branches of the subclavian and axillary arteries would furnish a large collateral supply of blood to the arm, if the subclavian were tied above the clavicle (p. 122). If the skin has not been reflected from the back of the arm, it should now be done. In the sub- cutaneous tissue will be seen the internal cutaneous branch of the musculo-spiral nerve, which supplies the skin as low down as the olecranon. On the inner side of this branch is the intercosto- humeral nerve, supplying the skin as far as the lower third of the arm. The nerve of Wrisberg also supplies the lower third of the arm ; and on the outer side for the same distance is the external cutaneous branch of the musculo-spiral nerve. The fascia is now to be removed, when the triceps will be exposed,, forming the only muscle on the back of the arm. TKICEPS EXTEN- This muscle', which arises by three distinct SOP. CUBITI. heads, and was only partially seen in the dissec- tion of the upper arm (p. 338), should now be thoroughly ex- amined. The long head arises immediately below the glenoid c c 386 TRICEPS. cavity of the scapula, by a strong flat tendon, which is connected with the capsular and glenoid ligaments of the shoulder-joint. The external head arises from, the posterior part of the humerus, below the insertion of the teres minor, as far as the musculo-spiral groove, from the outer border of the humerus, and the external intermuscular septum. The internal head arises from the posterior part of the humerus, below the teres major and the musculo-spiral groove, as far as the olecranon fossa ; it has an additional origin from the internal intermuscular septum, and from the internal border of the humerus. The precise origin of these heads from the humerus may be ascertained by following the superior profunda artery and musculo-spiral nerve, which separate them. The three portions of the muscle terminate upon a broad tendon, which covers the back of the elbow-joint, and is inserted into the summit and sides of the olecranon ; it is also connected with the fascia on the back cf the forearm. The effect of this connection is that the same muscle which extends the forearm tightens the fascia which gives origin to the extensors of the wrist and fingers. The same holds good in the case of the biceps, and its semilunar expansion in the fascia of the forearm. Between the tendon and the olecranon is a bursa, commonly of small size, but sometimes so large as to extend upwards behind the capsule of the joint. This bursa must not be mis- taken for the subcutaneous one, which is situated between the skin and the olecranon, and is so often injured by a fall on the elbow. By dividing the triceps transversely a little DISSECTION. above the elbow, and turning down the lower portion, it will be seen that some of the muscular fibres terminate upon the capsular ligament of the joint. They have been described as a distinct muscle, under the name of the subanconeus ; their use is to draw up the capsule, so that it may not be injured during extension of the arm. The subanconeus is in this respect analo- gous to the subcrureus muscle of the thigh. Observe the bursa under the tendon, and the arterial arch formed upon the back part of the capsule by the superior profunda and the anastomotica magna (fig. 89, p. 396). DISSECTION OF THE BACK OF THE FOREARM. 387 Trace the continuation of the superior profunda artery (p. 333) and musculo-spiral nerve round the posterior part of the humerus. They lie in a slight groove on the bone, 1 between the external and internal heads of the triceps, and are protected by an aponeurotic arch, thrown over them by the external head of the triceps. After supplying the muscles, the artery continues its course along the outer side of the arrn between the brachialis anticus and supinator radii longus, and inosculates with the radial recurrent. It gives off a branch, which runs down between the triceps and the bone, and inosculates, at the back of the elbow, with the anastomotica magna and posterior interosseous recurrent. The musculo-spiral nerve which accompanies the artery sends branches to supply the three portions of the triceps, the supinator radii longus, and ex- tensor carpi radialis longior. 2 It then divides into the posterior interosseous and radial nerves. The small nerve must be made out which runs down in the substance of the triceps, accompanied by a branch from the superior profunda artery, to supply the anconeus. The cutaneous branches of the musculo-spiral nerve have been already dissected (p. 326). DISSECTION OF THE BACK OF THE FOEEAEM, SUBCUTANEOUS Remove the skin from the back of the forearm, BUBS,E. hand, and fingers, and make out the subcutaneous bursa over the olecranon. It is of considerable size, and, if dis- tended, would appear nearly as large as a walnut. Another bursa is sometimes found a little lower down upon the ulna. A sub- cutaneous bursa is generally placed over the internal condyle, another over the external. A bursa is also situated over the sty- loid process of the ulna; this sometimes communicates with the sheath of the extensor carpi ulnaris. Small bur see are sometimes developed in the cellular tissue over each of the knuckles. 1 It is worth remembering that the nerve may be injured by a fracture of the humerus in this situation, and even by too tight bandaging ; the result being paralysis of the extensor muscles of the forearm. 2 The brachialis anticus usually receives a branch from the musculo-spiral nerve. c c 2 o88 FASCIA OX THE BACK OF THE FOREARM. The cutaneous veins, from the back of the hand and forearm r join the venous plexus at the bend of the elbow (see p. 327). CUTANEOUS ^^ e cutaneous nerves of the back of the fore- NEEVES OF THE arm, are derived from the external cutaneous BACK OF THE branches of the musculo- spiral, from branches of the internal cutaneous, and of the external cuta- neous nerves. The greater number of these nerves may be traced down to the back of the wrist. n ^ 6 ^ aC ^ ^ tne NEKVES ON THE BACK OF THE the subjacent tendons by an abundance of loose HAND AND connective tissue, in which are large veins, and FINGERS. branches of the radial and ulnar nerves. The doi'sal branch of the ulnar nerve passes beneath the tendon of the flexor carpi ulnaris, pierces the fascia just above the wrist-joint, runs over the posterior annular ligament of the wrist, and divides upon the back of the hand into filaments, which supply both sides of the back of the little finger, the ring finger, and the ulnar side of the middle, finger. The radial nerve passes obliqitely beneath the tendon of the supinator longus, perforates the fascia about two inches above the wrist-joint, and subdivides into filaments, which supply both sides of the back of the thumb and forefinger, and the radial side of the middle finger. 1 The radial nerve commonly gives off, on the back of the hand, a branch which joins the nearest branch of the ulnar. FASCIA ON BACK The fascia on the back of the forearm is com- OF FOREARM. posed of fibres interlacing and stronger than that upon the front of the forearm. It is attached to the condyles of the humerus and to the olecranon, and is strengthened by an expansion from the tendon of the triceps. Along the forearm it is attached to the ridge on the posterior part of the ulna. Its upper third gives origin to the fibres of the muscles beneath 1 The relative share which the radial and ulnar nerves take in supplying the fingers varies. Under any arrangement the thumb and each finger has two dorsal nerves, one on either side, of which the terminal branches reach the root of the nail. They supply filaments to the skin on the back of the finger, and have fre- quent communications with the palmar digital nerves. In some instances one or more of the dorsal nerves do not extend beyond the first phalanx : their place is then supplied by a branch from the palmar nerve. SHEATHS FOR THE EXTENSOR TENDONS. 389 it, and divides them by septa, to which their fibres are also attached. POSTERIOR This ligament should be considered as a part of ANNULAR LIGA- the fascia of the forearm, specially strengthened MENT> by oblique aponeurotic fibres on the back of the wrist, to confine the extensor tendons. These fibres are attached to the outer margin of the radius, and thence pass obliquely in- wards to the inner side of the wrist, where they are connected with the pisiform and cuneiform bones. They pass below the styloid process of the ulna, to which they are in no way attached, otherwise the rotation of the radius would be impeded. SEPARATE From the deep surface of the posterior annular SHEATHS FOR ligament, processes are attached to the ridges on EXTENSOR the back of the radius, so as to form six distinct fibro-osseous sheaths for the passage of the ex- tensor tendons. Commencing from the radius, the first sheath contains the tendons of the extensor ossis metacarpi and the extensor primi internodii pollicis ; the second, the tendons of the extensor carpi radialis longior and brevior ; the third, the tendon of the extensor secundi internodii pollicis ; the fourth, the tendons of the extensor indicis and the extensor communis digitorum ; the fifth, the tendon of the extensor minimi digiti ; and the sixth, the tendon of the extensor carpi ulnaris. All the sheaths are lined by synovial membranes, which extend nearly to the insertions of their tendons. Occasionally, but not often, one or more of them com- municate with the wrist-joint. The fascia of the metacarpus consists of a thin fibrous layer, continued from the posterior annular ligament. It separates the extensor tendons from the subcutaneous veins and nerves, and is attached to the radial side of the second metacarpal bone, and the ulnar side of the fifth. The fascia must be removed from the muscles, without injuring the muscular fibres which arise from its under surface. Preserve the posterior annular ligament. The following superficial muscles are now exposed, and should be examined in the order in which they are placed, proceeding from the radial to the ulnar side: 1. The supinator radii longus 390 SUPERFICIAL MUSCLES ON THE BACK OF THE FOREARM. SUPERFICIAL (already described, p. 345). 2. The extensor carpi MUSCLES ON THE radialis longior. 3. The extensor carpi radialis BACK OF THE brevior. 4. The extensor communis digfitorum. ff 5. The extensor minimi digiti. 6. The extensor carpi ulnaris. 7. The anconeus. A little below the middle of the forearm, the extensors of the wrist and fingers diverge from each other, leaving an interval, in which are seen the three extensors of the thumb namely, the ex- tensor ossis metacarpi pollicis, the extensor primi internodii pollicis, and the extensor secundi internodii pollicis. The two former cross obliquely over the radial extensors of the wrist, and pass over the lower third of the rad.ius ; the latter emerges from under the radial border of the extensor communis digitorum, and then passes over the insertions of the tendons of the radial extensors of the wrist. Between the second and third extensors of the thumb, we observe a part of the lower end of the radius, which is not covered either by muscle or tendon. This subcutaneous portion of the bone is immediately above the prominent tubercle in the middle of its lower extremity, and, since it can be easily felt through the skin, it presents a convenient place for examination in doubtful cases of fracture. EXTENSOR This muscle is partly covered by the supinator CARPI KADIALIS radii longus. It arises from the lower third of LONGIOR. fa e r ^g e leading to the external condyle of the humerus, and from the intermuscular septum. It descends along the outer side of the forearm, and terminates 'about the middle, in a flat tendon, which passes beneath the extensor ossis metacarpi and primi internodii pollicis, traverses a groove on the outer and back part of the radius, lined by a synovial membrane, and is inserted into the radial side of the carpal end of the metacarpal bone of the index finger. Previous to its insertion, the tendon is crossed by the extensor secundi internodii pollicis. It is supplied by a branch from the musculo-spiral nerve. EXTENSOR This muscle arises from the external condyle CARPI EADIALIS by the tendon common to it and the other ex- BREVIOR. tensors, from the intermuscular septa, from the external lateral ligament of the elbow-joint and the aponeurosis EXTENSOR COMMUNIS DIGITORUM. 391 covering the muscle. The muscular fibres terminate near the lower third of the forearm, upon the under surface of a flat tendon, which descends, covered by that of the extensor carpi radialis longior, beneath the three extensors of the thumb. The tendon traverses a groove on the back of the radius, on the same plane with that of the long radial extensor, but lined by a separate synovial membrane, and is inserted into the radial side of the base of the metacarpal bone of the middle finger. A bursa is generally found between the tendon and the bone. Its nerve comes from the posterior interosseous. EXTENSOB This muscle arises from the common tendon DIGITORUM attached to the external condyle, from the septa COMMDNIS. between it and the contiguous muscles, and from its strong fascial covering. A little below the middle of the fore- arm, the muscle divides into three tendons, which pass, together with the extensor indicis, beneath the posterior annular ligament, through a groove on the back of the radius lined by synovial membrane. On the back of the hand the tendons become broader and flatter, and diverge from each other towards the metacarpal joints of the fingers, where they become thicker and narrower, and give off, on each side, a fibrous expansion, which covers the sides of the joint. Over the first phalanx of the finger, each tendon again spreads out, receives the expanded tendons of the lumbricales and interossei muscles, and divides at the second phalanx into three portions, of which the middle is inserted into the upper end of the second phalanx ; the two lateral, reuniting over the lower end of the second phalanx, are inserted into the upper end of the third. 1 Its nerve comes from the posterior interosseous. The oblique aponeurotic slips which connect the tendons on the back of the hand are subject to great variety. The tendon of the index finger is commonly free ; it is situated on the radial 1 The extensor tendons are inserted into the periosteum ; but the flexor tendons are inserted into the substance of the bone. This accounts for the facility with which the former will tear off the bones in cases of necrosis, while the latter will adhere so tightly as to require cutting before the phalanx can be removed. It pro- bably also explains the great liability to necrosis which is so frequently observed in cases of thecal abscess. 392 EXTENSOR CARPI ULNARIS. side of the proper indicator tendon, and becomes united with it at the metacarpal joint. The tendon of the middle finger usually receives a slip from that of the ring. The tendon of the ring finger generally sends a slip to the tendons on either side of it, and, in some cases, entirely furnishes the tendon of the little finger. Thus the ring finger does not admit of independent extension. The muscle is not only a general extensor of the fingers, but can extend some of the phalanges independently of the rest : e.g. it can extend the first phalanges while the second and third are flexed ; or it can extend the second and third phalanges during flexion of the first. EXTENSOR This long slender muscle, situated on the ulnar MINIMI DIGITI OE side of the common extensor, arises from the com- AUEICULAKIS. mon tendon from the external condyle, and from the septa between it and the contiguous muscles. Its slender tendon runs separately beneath the annular ligament immediately behind the joint between the radius and ulna, in a special sheath lined by synovial membrane. On emerging from the annular liga- ment, the tendon splits into two, which pass obliquely to the little finger. At the first joint of the little finger, the outer tendon is joined by that of the common extensor, and both expand upon the first and second phalanges, terminating in the same manner as the extensor tendons of the other fingers. Its nerve comes from the posterior interosseous. EXTENSOR This muscle arises from the common tendon CARPI ULNARIS. from the external condyle, from the septum be- tween it and the extensor minimi digiti, from the fascia of the forearm, and from the aponeurosis attached to the posterior ridge of the ulna common to this muscle, the flexor carpi ulnaris, and the flexor profundus digitorum. The fibres terminate upon a strong, broad tendon, which traverses a distinct groove on the back of the ulna, close to the styloid process, and is inserted into the posterior aspect of the carpal end of the metacarpal bone of the little finger. Below the styloid process of the ulna, the tendon passes beneath the posterior annular ligament, over the back of the wrist, and is confined in a very strong fibrous canal, which is attached to the DEEP MUSCLES ON THE BACK OF THE FOREARM. 393 back of the cuneiform, pisiform, and unciform bones, and is lined by a continuation from the synovial membrane in the groove of the ulna. The action of this muscle is to extend the hand, and incline it towards the ulnar side. It is supplied by the posterior inter- osseous nerve. In pronation of the forearm, the lower articular end of the ulna projects between the tendons of the extensor carpi ulnaris and the extensor minimi digiti. A subcutaneous bursa is sometimes found -above the bone in this situation. This small triangular muscle is situated at the outer and back part of the elbow. It is covered by a strong layer of fascia, derived from the tendon of the triceps, and appears like a continuation of that muscle. It arises by a ten- don from the posterior part of the external condyle of the humerus, and is inserted into the triangular surface on the upper fourth of the outer part of the ulna. Part of the under surface of the muscle is in contact with the capsule of the elbow-joint. Its action is to assist in extending the forearm. Its nerve comes from the musculo- spiral. To expose the deep layer of muscles, detach from DISSECTION. ^, , -11,1 j- v the external condyie the extensor carpi radians brevior, the extensor communis digitorum, the extensor minimi digiti, and the extensor carpi ulnaris ; and, after noticing the ves- sels and nerves which enter their under surface, turn them down. The deep-seated muscles, with the posterior interosseous artery and nerve, must be dissected. The muscles exposed are: 1. The ex- DEEP SEATED tensor ossis metacarpi pollicis. 2. Extensor primi MUSCLES ON THE internodii pollicis. 3. Extensor secundi inter- BACK OF THE nodii pollicis. 4. Extensor indicis or indicator. POREAKM. 5 The supinator ra( jii brevis. They are all sup- plied by branches from the posterior interosseous nerve. EXTENSOR This muscle lies immediately below the supinator Ossis METACARPI brevis, and ayises from the posterior surface of the POLLICIS. ulna below the supinator brevis, from the posterior surface of the middle third of the radius, and from the interosseous membrane. The muscle passes obliquely downwards and outwards, crosses the radial extensors of the wrist about three inches above 394 EXTENSORS OF THE THUMB. the carpus, and terminates in a tendon, which passes along a common groove with the extensor primi internodii pollicis, lined by synovial membrane, on the outer part of the lower end of the radius, and is inserted into the base of the metacarpal bone of the thumb, and frequently also by a tendinous slip into the trapezium. EXTENSOR This, the smallest of the deep muscles, arises PKIMI INTERNODII from the posterior surface of the radius, below the POLLICIS. preceding, and from the interosseous membrane. It descends obliquely in company with the preceding muscle, turns over the radial extensors of the wrist, and terminates upon a tendon which passes beneath the annular ligament, through the groove on the outer part of the radius, and is inserted into the radial side of the base of the first phalanx of the thumb. EXTENSOR This muscle covers part of the origin of the SECUNDI INTER- preceding muscle, and arises from the posterior NODII POLLICIS. surface of the ulna, below the extensor ossis meta- carpi pollicis, and from the interosseous membrane. The tendon receives fleshy fibres as low as the wrist, passes beneath the annu- lar ligament in a distinct groove on the back of the radius, crosses the tendons of the radial extensors of the wrist, proceeds over the metacarpal bone and the first phalanx of the thumb, and is inserted into the base of the last phalanx. The tendons of the three extensors of the thumb may be easily distinguished in one's own hand. The extensor ossis metacarpi and primi internodii pollicis cross obliquely over the radial artery, where it lies on the external lateral ligament of the carpus ; the extensor secundi internodii pollicis crosses the artery just before it sinks into the palm, between the first and second metacarpal bones, and is a good guide to the vessel. The action of the three extensors of the thumb is implied by their names. EXTENSOR This muscle arises from the posterior surface of INDICIS, OK INDI- the ulna, below the extensor secundi internodii CATOB - pollicis, and slightly from the interosseous mem- brane. The tendon passes beneath the posterior annular ligament, in the same groove, on the back of the radius, with the tendons of the extensor digitorum communis. It then proceeds over the back POSTERIOR INTEROSSEOUS ARTERY. 395 of the haad to the first phalanx of the index finger, where it is united to the ulnar border of the common extensor tendon. By the action of this muscle the index finger can be extended indepen- dently of the others. Reflect the anconeus from its origin, to expose DISSECTION. , , ,, . n the following muscle SUPINATOR This muscle embraces the upper third of the EADH BKEVIS. radius. It arises from the external condyle of the humerus, from the external lateral ligament of the elbow-joint, from the orbicular ligament surrounding the head of the radius, from an oblique ridge on the outer surface of the ulna below the insertion of the anconeus, by fleshy fibres from the triangular ex- cavation below the lesser sigmoid notch of the ulna, and from the aponeurosis covering the muscle. The muscular fibres tarn over the neck and upper part of the shaft of the radius, and are inserted into the upper third of this bone, as far forwards as the ridge lead- ing from the tubercle to the insertion of the pronator teres. The muscle is traversed obliquely by the posterior interosseous nerve, which sends a branch to it, and its upper part is in contact with the capsule of the elbow-joint. It is a powerful supinator of -the forearm, some of its fibres acting at nearly a right angle to the axis of the radius. POSTERIOR This artery comes from the ulnar by a common INTEHOSSEOUS trunk with the anterior interosseous (p. 352), and ARTERY. supplies the muscles on the back of the forearm. It passes between the oblique ligament and the interosseous membrane, and appears, at the back, between the supinator radii brevis and the extensor ossis metacarpi pollicis. After supplying branches to all the muscles in this situation, the artery descends, much diminished in size, between the superficial and deep layer of muscles to the wrist, where it inosculates with the carpal branches of the anterior interosseous, and the posterior carpal branches of the radial and ulnar arteries. The largest branch of this artery is the interosseoiis recurrent. It ascends beneath the supinator brevis and the anconeus to the space between the external condyle and the olecranon, where it inosculates with the branch of the superior profuiida which descends in the sub- 396 POSTERIOR IXTEROSSEOUS NERVE. stance of the triceps, with the posterior ulnar recurrent artery, and with the anastomotica magna. In the lower part of the back of the forearm, a branch of the anterior interosseous artery is seen passing through the inter- osseous membrane to reach the back of the wrist. FIG. 89. 1. The superior profunda. 2. The anastomotica magna. 3. The posterior ulnar recur- rent. 4. The posterior I interosseous I its ascending and descend- ing branches. 5. The termination of the an- terior interosseous. 6. The posterior carpal arch. DIAGKAM SHOWING THE ANASTOMOSES OF ABTEKIES AT THE BACK OF THE ELBOW AND WBIST JOINTS. POSTEBIOB INTEBOSSEOUS NEBVE. The nerve which supplies the muscles on the back of the forearm is the posterior interosseous, one of the divisions of the musculo-spiral. It passes obliquely through the supinator radii brevis, and descends, lying on the lower fibres of this muscle, the extensores ossis meta- carpi and primi internodii pollicis, and beneath the superficial extensors. It then, much diminished in size, passes under the RADIAL ARTERY ON THE BACK OF THE WRIST. 397 extensor secundi internodii pollicis, on the interosseous membrane, as far as the posterior annular ligament, where it presents a gan- giiform enlargement. Between the superficial and deep layer of muscles, it sends to each a filament, generally in company with a branch of the posterior interosseous artery. It sends a branch to the extensor carpi radialis brevior, and supplies the supinator brevis in passing through its substance. The supinator radii longus and the extensor carpi radialis longior are supplied by distinct branches from the musculo-spiral nerve. After the posterior interosseous nerve descends beneath the extensor secundi internodii pollieis, it lies in the interosseous membrane, beneath the extensor digitorum communis and the indicator. At the back of the wrist, beneath the annular ligament, it forms the gangliform enlargement from which filaments are sent to the carpal and metacarpal joints. DISSECTION ^ e dial artery is continued over the external RADIAL AETEKY lateral ligament of the carpus, beneath some fila- ON THE BACK OF ments of the radial nerve, cutaneous veins, and THEWKIST. ^e extensor tendons of the thumb, to the proximal part of the interval between the first and second meta- carpal bones, where it dips down between the two origins of the abductor indicis, and, entering the palm, forms the deep palmar arch. In this part of its course it is accompanied by a filament of the musculo-cutaneous nerve ; observe also that the tendon of the extensor secundi internodii pollicis passes over it immediately before it sinks into the palm. It supplies in this part of its course the following small branches to the back of the hand : a. Posterior carpal artery. This branch passes across the carpal bones, beneath the extensor tendons. It inosculates with the termina- tion of the anterior interosseous artery, and forms an. arch beneath the extensor tendons, with a corresponding branch from the ulnar artery. The carpal arch sends off small branches, called the dorsal interosseous, which descend along the third and fourth interosseous spaces from the arch just mentioned, beneath the extensor tendons, and inosculate near the carpal ends of the metacarpal bones with the perforating branches from the deep palmar arch. b. The first dorsal interosseous artery is generally larger than the 398 INTEROSSEOUS MUSCLES. others. It passes forwards, beneath the extensors of the thumb, on the second interosseous space to the cleft between the index and middle fingers, communicating here with a perforating branch of the deep palmar arch ; and terminates in small branches, some of which proceed along the back of the fingers, others inosculate with the palmar digital arteries. c. The dorsalis indicis, a branch of variable size, passes over the first interosseous muscle along the radial side of the back of the index finger. d. The dorsales pollicis are two small branches which arise from the radial opposite the head of the first metacarpal bone, and run along the back of the thumb, one on either side. They are often absent. These dorsal interosseous arteries supply the extensor tendons and their sheaths, the interosseous muscles, and the skin on the back of the hand, and the first phalanges of the fingers. Remove the tendons from the back, and from the palm, of the hand : observe the deep palmar fa'scia which covers the interosseous muscles. It is attached to the ridges of the metacarpal bones, forms a distinct sheath for each interosseous muscle, and is continuous inferiorly with the transverse metacarpal ligament. On 'the back of the hand the interosseous muscles are covered by a thin fascia, which is attached to the adjacent borders of the metacarpal bones. TEANSVEKSE This consists of strong bands of ligamentons METACAEPAL fibres, which pass transversely between the distal LIGAMENT. extremities of the metacarpal bones. These bands are intimately united to the fibre-cartilaginous ligament of the metacarpal joints, and are of sufficient length to admit of a certain degree of movement between the ends of the metacarpal bones. Remove the fascia which covers the interosseous DISSECTION. , -, , ,-, 111 muscles, and separate the metacarpal bones by dividing the transverse metacarpal ligament. A bursa is fre- quently developed between their digital extremities. INTEKOSSEOUS These muscles, so named from their position, MUSCLES. extend from the sides of the metacarpal bones to the bases of the first phalanges and the extensor tendons of the fingers. In each interosseous space (except the first, in which DORSAL INTEROSSEI. 399 there is only an abductor) there are two muscles, one of which is an abductor, the other an adductor, of a finger. Thus there are .seven in all : four of which, situated on the back of the hand, are called dorsal ; the remainder, seen only in the palm, are called palmar. 1 They are all supplied by the ulnar nerve. DORSAL Each dorsal interosseous is a bipenniform INTEROSSEI. muscle, and arises from the opposite sides of two contiguous metacarpal bones (fig. 90). From this double origin the fibres converge to a tendon, which passes between the meta- FIG. 90. FIG. 91. DIAGRAM OF THE FOUR DORSAL IN- TEROSSEI, DRAWING FROM THE MIDDLE LINE. DIAGRAM OF THE THREE PALMAR INTER- OSSEI, AND THE ADDUCTOR POLLICIS, DRAWING TOWARDS THE MIDDLE LINE. carpal joints of the finger, and is inserted into the side of the base of the first phalanx, and by a broad expansion into the extensor tendon on the back of the same finger. The first dorsal interosseous muscle (abductor indicis) is larger than the others, and occupies the interval between the thumb and fore-finger. It arises from the proximal half of the ulnar side of the first metacarpal bone, and from the entire length of the radial side of the second : between the two origins, the radial artery 1 If we consider the adductor pollicis as a palmar interosseous muscle, there would be four palmar and four dorsal all supplied by the ulnar nerve. 400 PALMAR INTEROSSEI. passes into the palm. Its fibres converge on either side to a tendon, which is inserted into the radial side of the first phalanx of the index finger and its extensor tendon. The second dorsal interosseous muscle occupies the second meta- carpal space. It is inserted into the radial side of the first phalanx of the middle finger and its extensor tendon. The third and fourth, occupying the corresponding metacarpal spaces, are inserted, the one into the ulnar side of the middle, the other into the ulnar side of the ring finger. If a line be drawn longitudinally through the middle finger, as represented by the dotted line in fig. 90, we find that all the dorsal interosseous muscles are abductors from that line ; conse- quently, they separate the fingers from each other. PALMAR INTER- It requires a careful examination to distinguish OSSEOUS. this set of muscles, because the dorsal muscles protrude with them into the palm. They are smaller than the dorsal, and each arises from the lateral surface of only one meta- carpal bone that, namely, connected with the finger into which the muscle is inserted (fig. 91). They terminate in small tendons, which pass between the metacarpal joints of the fingers, and are inserted, like those of the dorsal muscles, into the sides of the first phalanges and the extensor tendons on the back of the fingers. The first palmar interosseous muscle arises from the ulnar side of the second metacarpal bone, and is inserted into the ulnar side of the index finger. The second and third arise, the one from the radial side of the fourth, the other from the radial side of the fifth metacarpal' bone, and are inserted into the same sides of the ring and little fingers. The palmar interosseous muscles are all adductors to a line drawn through the middle finger (fig. 91). They are, therefore, the opponents of the dorsal interosseous, and move the fingers towards each other. 1 . 1 The interossei, probably, also assist the flexors of the ringers when the latter are slightly flexed at their metacarpo-phalangeal joints. M. Duchenne believes that, in addition to their usually ascribed function of abduction, adduction, and supplemental flexion at the nietaearpo-phalangeal articulation, the interossei act STERNO-CLAVICULAR LIGAMENTS. 401 The palmar and dorsal interossei are supplied by filaments from the deep branch of the ulnar nerve. DISSECTION OF THE LIGAMENTS. STEENO-CLAVI- The inner end of the clavicle articulates with CUIAB JOINT. the comparatively small and shallow excavation on the upper and outer part of the sternum, and is an arthrodial joint. The security of the joint depends upon the great strength of its ligaments. There are two synovial membranes, and an intervening fibre-cartilage. The anterior sterno-clavicular ligament (fig. 92) consists of a strong broad band of ligamentous fibres, which pass obliquely downwards and inwards over the front of the joint, from the inner end of the clavicle to the anterior surface of the sternum. The posterior sterno-clavicular ligament extends over the back of the joint, its fibres passing downwards and forwards from the back of the clavicle to the back of the sternum in a similar manner to the anterior. The interclavicular ligament connects the clavicles directly. It extends transversely along the notch of the sternum, and has a broad attachment to the upper border of each clavicle. Between the clavicles it is more or less attached to the sternum, so that it forms a curve with the concavity upwards. The three ligaments just described are so closely connected as extensors of the second and third phalanges ; the common extensor tendons acting only as extensors of the first phalanges. (Physiologie des Mouvements <&c., 1867.) The action of the lumbricales in extending the second and third phalanges (even if they are not the chief factors of this movement) must not be lost sight of, for in a case, recorded in St. Barttiolomew' 's Hospital Reports, 1881, in which the ulnar nerve had been divided a short distance above the wrist-joint, the first phalanges of the ring and little ringers were bent (extended) upon their articu- lating metacarpal bones, the second and third phalanges being flexed at obtuse angles upon their proximal phalanges : the index and middle fingers being normal. I attribute this condition to paralysis of the two ulnar lumbricales and not to loss of power of the interossei. I have seen about a dozen instances of division of the ulnar nerve, and in all of them the same condition of the little and ring fingers has existed. D D 402 STEENO-CLAVICULAR LIGAMENTS. that, collectively, they form for the joint a complete fibrous capsule of such strength that dislocation of it is rare. The costo-clavicular or rhomboid ligament connects the clavicle to the cartilage of the first rib. It ascends obliquely outwards and backwards from the cartilage of the rib to a rough surface beneath the sternal end of the clavicle. Its use is to limit the elevation of the clavicle. There is such constant movement between the clavicle and the cartilage of the first rib that a well-marked bursa is com- monly found between them. FIG. 92. DIAGRAM OF THE STEBNO-CLAVICULAK LIGAMENTS. 1. Interclavicular ligament. 2. Anterior sterno-clavicular ligament. 3. Costo-clavicular ligament. 4. Interarticular fibro-cartilage. Interarticular fibro-cartilage. To see this, cut through the rhomboid, the anterior and posterior ligaments of the joint, and raise the clavicle. It is nearly circular in form, and thicker at the circumference than the centre, in which there is sometimes a perforation, and divides the articulation into two cavities. In- feriorly, it is attached to the cartilage of the first rib, close to the sternum ; superiorly, to the upper part of the clavicle and the inter clavicular ligament. Its circumference is inseparably con- nected with the anterior and posterior ligaments. 1 1 Interarticular fibro-cartilages (menisci) also exist in the following joints : acromio-clavicular, temporo-maxillary, knee, and wrist joints. Professor Hum- phry has shown that interarticular cartilages augment the variety of movements in a joint, permitting for instance that of rotation in the knee-joint, in addition to that of extension and flexion, which otherwise would be the only possible ones. SCAPULO-CLAVICULAR JOINT. 403 The joint is provided with two synovial membranes : one between the articular surface of the sternum and the inner surface of the nbro-cartilage ; the other between the articular surface of the clavicle and the outer surface of the nbro-cartilage. This interarticular nbro-cartilage is a structure highly elastic, without admitting of any stretching. It equalises pressure, breaks shocks, and also acts as a ligament, tending to prevent the clavicle from being driven inwards towards the mesial line. Observe the relative form of the cartilaginous surfaces of the bones : that of the sternum is slightly concave in the transverse, and convex in the antero-posterior direction ; that of the clavicle is the reverse. The form of the articular surfaces and the ligaments of a joint being known, it is easy to understand the movements of which it is capable. The clavicle can be moved upon the sternum in a direction either upwards, downwards, backwards, and forwards ; it also admits of circumduction. These movements, though limited at the sternum, are considerable at the apex of the shoulder. 1 SOAPULO- The outer end of the clavicle articulates with LAVICULAH the acromion, and is connected by strong liga- JOINT - ments to the coracoid process of the scapula. The clavicle and the acromion articulate with each other by two flat oval cartilaginous surfaces, of which the planes slant inwards, and the longer diameters are in the antero-posterior direction. It is an arthrodial joint. The superior acromio-clavicular ligament, a broad band of par- allel ligamentous fibres, strengthened by the aponeurosis of the 1 Professor Humphry, in describing the movements of this joint, in his valuable work ' On the Human Skeleton,' says, ' The movements attendant on elevation and depression of the shoulder take place between the clavicle and the interarticular ligament, the bone rotating upon the ligament on an axis drawn from before back- wards through its own articular facet. When the shoulder is moved forwards and backwards, the clavicle, with the interarticular ligament, rolls to and fro on the articular surface of the sternum, revolving, with a slightly sliding movement, round an axis drawn nearly vertically through the sternum. In the circumduction of the shoulder, which is compounded of these two movements, the clavicle revolves upon the interarticular cartilage, and the latter, with the 'clavicle, rolls upon the sternum.' n n 2 404 CONOID AND TRAPEZOID LIGAMENTS. trapezius, extends from the upper surface of the acromion to the upper surface of the clavicle. The inferior acromio-clavicidar ligament, of less strength, ex- tends along the under surface of the joint from bone to bone. An interarticular fibro-cartilac/e is . sometimes found in this joint : but it is incomplete, and seldom extends lower than the upper half. There is only one synovial membrane. Coraco-clavicidar ligament. The clavicle is connected to the coracoid process of the scapula by two strong ligaments the conoid and trapezoid, which, being continuous with each other, should be considered as one. The trapezoid ligament is the more anterior and external. Quadrilateral in shape, it arises from the (portions of -. T~ 5. Tendon of biceps. /; -:, -^s^^m^i||ifc^gjg^ thecoraco- W^^T 6< Ca P sular ligament of clavicular ^.^jBF^"^^? the shoulder-joint, ligament. ^H^^U^r^^. ""Hj^" " ~*"" 7. Coraco-humeral liga- 3. Suprascapular or trans- M^^- I^KS^^ ment. verse ligament. ^ /^B 8. Foramen in the capsu- 4. Coraco-acromial liga- \r~~um^k IE- 6 lar ligament for the ment. /*> J|r//.^^^B snbscapnlaris tendon. ANTEEIOK VIEW OF THE SCAPULO-CLAVICULAE LIGAMENTS, AND OF THE SHOULDER-JOINT. back of the upper surface of the coracoid process, and ascends obliquely backwards and outwards to the oblique line on the under aspect of the clavicle, near its outer end. The conoid ligament, triangular in form, is situated behind the trapezoid ligament to the posterior border of which it is attached. It is fixed at its apex to the root of the coracoid process, ascends nearly vertically, and is attached by its base to the clavicle. The coraco-clavicular liga- ments fix the scapula to the clavicle, and prevent undue rotation of the scapula. When the clavicle is fractured in the line of the attachment of the coraco-clavicular ligament, there is little or no displacement of the fractured ends, these being kept in place by the ligament. THE SHOULDER-JOINT. 405 LIGAMENTS OF These are two : the coraco-acromial or triangular THE SCAPULA, ligament, attached by its apex to the tip of the acromion process, and by its base to the outer border of the coracoid process ; it is separated from the upper part of the capsule of the shoulder-joint by a large bursa ; and the transverse or cora- coid ligament, which passes across the suprascapular notch, con- verting it into a foramen. The suprascapular vessels pass over the foramen, the suprascapular nerve through it. SHOULDER- The articular surface of the head of the humerus, JOINT. forming rather more than one-third of a sphere, moves upon the shallow glenoid cavity of the scapula, which is of an oval form, with the broader end downwards, and the long diameter nearly vertical. The security of the joint depends, not upon any mechanical contrivance of the bones, but upon the great strength and number of the ligaments and tendons which surround and are intimately connected with it. It is an enarthrodial, or ball-and- socket joint. To admit the free motion of the head of the humerus upon the glenoid cavity, it is requisite that the capsular ligament of the joint be loose and capacious. Accordingly, the head of the bone, when detached from its muscular connections, may be separated from the glenoid cavity to the extent of an inch or more, without laceration of the capsule. This explains the elongation of the arm observed in some cases in which effusion takes place into the joint ; also in cases of paralysis of the deltoid. The capsular ligament is attached above, round the circumference of the glenoid cavity; below, round the anatomical neck of the humerus. It is strongest on its upper aspect, weakest and long- est on its lower. It is strengthened on its upper and posterior part by the tendons of the supraspinatus, infraspinatus, and teres minor ; its inner part is strengthened by the broad tendon of the subscapularis and the coraco-humeral ligament ; its lower part, by the long head of the triceps. Thus the circumference of the capsule is surrounded by tendons on every side, excepting a small space towards the axilla. If the humerus be raised, it will be found that the head of the bone rests upon this unprotected portion of the capsule, between the tendons 406 THE SHOULDER- JOINT. of the subscapularis and the long head of the triceps : through this part of the capsule the head of the bone is first protruded in dislo- cations into the axilla. At the upper and inner side of the joint, a small opening is observable in the capsular ligament, through which the tendon of the subscapularis passes, so that the synovial membrane of the joint communicates with the bursa under the tendon of this muscle. A second opening exists in the lower part of the front of the capsular ligament, where the tendon of the biceps emerges from the joint. A third opening occasionally exists between the joint, and a bursa under the tendon of the infraspinatus muscle. The upper and inner surface of the capsule is strengthened by a strong band of ligamentous fibres, called the coraco-humeral or accessory ligament. It is attached to the root of the coracoid pro- cess, expands over the upper surface of the capsule, with which it is inseparably united, and, passing downwards and outwards, is attached to the greater tuberosity of the humerus. Open the capsule to see the tendon of the long head of the biceps. It arises by a rounded tendon from the upper margin of the glenoid cavity, and is continuous with the glenoid ligament ; becoming slightly flattened, it passes over the head of the humerus, descends through the groove between the two tuberosities, and, after piercing the capsular ligament of the shoulder-joint, it passes along the bicipital groove, being retained in situ by an aponeurotic prolon- gation from the tendon of the pectoralis major. It is loose and moveable within the joint. It acts like a strap, keeping down the head of the bone when the arm is raised by the deltoid, and then might be considered as taking the part of a ligament of the joint. The tendon of the biceps, strictly speaking, does not perforate the synovial membrane of the joint. It is enclosed in a tubular sheath, which is reflected over it at its attachment to the glenoid cavity, and accompanies it for two inches down the groove of the humerus. During the earlier part of foetal life, it is connected to the capsule by a fold of synovial membrane, which subsequently disappears. The margin of the glenoid cavity of the scapula is surrounded THE SHOULDER-JOINT. 407 by a fibre-cartilaginous band of considerable thickness, called the glenoid ligament. This not only enlarges, but deepens the cavity. Superiorly, it is continuous on either side with the tendon of the biceps ; inferiorly, with the tendon of the triceps : in the rest of its circumference it is attached to the edge of the cavity. The cartilage covering the head of the humerus is thicker at the centre than at the circumference. The reverse is the case in the glenoid cavity. The synovial membrane lining the under surface of the capsule, is reflected around the tendon of the biceps, and passes with it in the form of a cul-de-sac down the bicipital groove. On the inner side of the joint it always communicates with the bursa beneath the tendon of the subscapularis. . There is also a large bursa situated between the capsule and the deltoid muscle, which does not communicate with the joint. The muscles in relation with the joint are : above, the supra- spinatus ; behind, the infraspinatus and teres minor ; below, the long head of the triceps ; internally, the subscapularis ; and, inside the joint, the long head of the biceps. The shoulder-joint is an enarthrodial joint, and has a more ex- tensive range of motion than any other joint in the body ; it is what mechanics call a universal joint. It is capable of motion forwards and backwards, of adduction, abduction, circumduction, and rotation. The various movements are limited chiefly by the surrounding muscles and by atmospheric pressure, for the capsule is so lax as to offer no obstacle to the freedom of movement in any direction. The amount of rotation which the head of the humerus is capable of, is to the extent of a quarter of a circle. The movements of which the shoulder-joint is capable are effected by the following muscles : thus Extension is effected by the posterior fibres of the deltoid, latis- simus dorsi, teres major, and (when the arm is raised) by the infra- spinatus and teres minor. Flexion, by the anterior fibres of the deltoid, coraco-brachialis, and the pectoralis major (slightly). Abduction, by the deltoid and the supraspinatus. Adduction, by the pectoralis major, latissimus dorsi, teres major, 408 THE ELBOW-JOES'T. coraco-brachialis ; and (when the arm is raised) by the sub- scapular is. Rotation inwards, by the subscapularis, latissimus dorsi, and teres major. Rotation outivards, by the infraspinatus and the teres minor. The elbow-joint is a ginglyruus or hinge-joint. The larger sigmoid cavity of the ulna is adapted to the trochlea upon the lower end of the humerus, admitting only of flexion and extension ; while the shallow excavation upon the FIG. 94. ELBOW-JOINT. . External lateral liga- CL ment. 6. Orbicular or annular ligament. c. Part of internal la- teral ligament. d. Radius, removed from the annular ligament. LIGAMENTS OF THE ELBOW-JOINT. head of the radius admits not only of flexion and extension, but of central rotation, upon the rounded articular eminence (capitellum) of the humerus, and of peripheral rotation at the superior radio- ulnar articulation. The joint is secured in front and behind by anterior and posterior ligaments, and laterally by two strong lateral ligaments. No ligament is attached to the head of the radius, otherwise its" rotatory movement would be impeded. The head is simply sur- rounded by a ligamentous collar, called the annular ligament, within which it freely rolls in pronation and supination of the hand. SUPERIOR RADIO-ULNAR ARTICULATION. 409 The anterior ligament consists of broad thin ligamentous fibres, attached above to the front of the humerus, above the coro- noid fossa, below to the coronoid process of the ulna and to the orbicular ligament, and continuous on each side with the lateral ligaments. Some of the fibres cross each other at right angles. The posterior ligament is composed of thin loose fibres attached above to the margin of the olecranon fossa, below to the border of the olecranon, and spread over the posterior aspect of the joint. The internal lateral ligament is triangular, and is divided into two portions, an anterior and a posterior. Its anterior part is attached to the front of the internal condyle of the humerus : from this point the fibres radiate, and are inserted along the inner mar- gin of the coronoid process of the ulna. The posterior part is also triangular, and passes from the back part of the internal condyle to the inner border of the olecranon. A band of fibres extends transversely from the olecranon to the coronoid process, across a notch observable on the inner side of the sigmoid cavity : through this notch small vessels pass into the joint. The external lateral ligament is attached to the external condyle of the humerus, and is in intimate connection with the common tendon of the extensors. The fibres spread out as they descend, and are interwoven with the annular ligament surrounding the head of the radius. The preceding ligaments, collectively, form a continuous cap- sule for the joint. SUPEEIOE The orbicular or annular ligament of the radius BADIO-ULNAB forms about three-fourths of a ring. Its ends are AKTICULATION. attached to the anterior and posterior borders of the lesser sigmoid cavity of the ulna, and is broader in the middle than at either end. Its lower border is straight ; its upper border is convex, and connected with the anterior and external lateral liga- ments. With this sigmoid cavity it forms a complete collar, which encircles the head, and part of the neck, of the radius. The lower part of the ring is narrower than the upper, the better to clasp the neck of the radius, and maintain it more accurately in position. Synovial membrane of the elboiv-joint. Open the joint by a transverse incision in front, and observe the relative adaptation of 410 INTEROSSEOUS MEMBRANE. the cartilaginous surfaces of the bones. The synovial membrane lines the interior of the capsule, and forms a cul-de-sac between the head of the radius and its annular ligament. It is widest and loosest under the tendon of the triceps. Where the membrane is reflected from the bones upon the ligaments, there is more or less adipose tissue, particularly in the fossas on the front and back part of the lower end of the humerus. The only movements permitted between the humerus and the ulna are those of flexion and extension, both of which are limited by the ligaments and tendons in front of and behind the joint, and probably not by the coronoid and olecranon processes. The head of the radius is most in contact with the capitellum of the humerus during semiflexion and semipronation ; and it is kept, by the strong orbicular ligament which surrounds the neck of the radius, from being dislocated forwards by the biceps. The movement at the superior radio-ulnar articulation is that of rotation in the lesser sigmoid cavity of the ulna, forming an example of a lateral gin- glymus or diarthrosis rotatoria. It is by this rotation of the head of the radius, that the hand is carried through an extensive range of pronation and supination ; for it is articulated only to the lower end of the radius, the ulna being excluded by the interarticular fibre-cartilage from taking any share in the movement at the wrist- joint. INTEBOSSEOUS This is an aponeurotic septum, stretched be- MEMBRANE. tween the interosseous ridges of the radius and ulna, of which the chief purpose is to afford an increase of surface for the attachment of muscles. The septum is deficient above, beginning about an inch below the tubercle of the radius, and thus permits free rotation of that bone. Its fibres extend obliquely downwards from the radius to the ulna. It is perforated in its lower third by the anterior interosseous vessels. The name of round or oblique ligament is given to a thin band of fibres, which extends obliquely between the bones of the fore- arm in a direction contrary to those of the interosseous membrane. It is attached, superiorly, to the front surface of the ulna, near the outer side of the coronoid process ; inferiorly, to the radius imme- diately below the tubercle. Between this ligament and the upper INFERIOR RADIO-ULNAR ARTICULATION. 411 border of the interosseous membrane is a triangular interval through which the posterior interosseous artery passes to the back of the forearm. A bursa intervenes between the oblique ligament and the insertion of the tendon of the biceps. The use of this ligament is to limit supination of the radius. INFERIOR This joint is a lateral ginglynius, and is formed RADIO-ULNAR by the inner concave surface of the lower end of ARTICULATION. fa e ra C 4| 5 RECTO-VESICAL POUCH. 501 upper half of the rectum. Some of these structures will now be described, while others can be better dissected in the side view of the pelvis. COURSE OF The rectum enters the pelvis on the left side of THE EECTUM. the sacrum, and, after describing a curve corre- sponding with the concavity of the sacrum, terminates at the anus. In the first part of its course it is loosely connected to the back of the pelvis by a peritoneal fold, called the meso^ectum : between the layers of this fold, the superior hsemorrhoidal vessels, the continu- ation of the inferior mesenteric, with nerves and lymphatics, runs to the bowel. The rectum does not take this course in all cases ; sometimes it makes one, or even two lateral curves. In some rare cases it enters the pelvis on the right side instead of the left. Since these variations from the usual arrangement cannot be ascertained during life, they should make us cautious in the introduction of bougies. 1 EECTO-VESICAL Whilst the parts are still undisturbed, introduce POUCH. the finger into the recto-vesical peritoneal pouch (fig. 116). This is a cul-de-sac formed by the peritoneum in pass- ing from the front of the rectum to the lower and back part of the bladder. In the adult male, the bottom of this pouch is about one inch distant from the base of the prostate gland ; 2 therefore part of the under surface of the bladder is not covered by peritoneum ; and since this part is in immediate contact with the rectum, it is practicable to tap the distended bladder through the front of the bowel without injuring the peritoneum. The operation has, of late years, been revived, and with great success. 3 It is easily done, and not attended with risk, provided all the parts be in their regular position. But this is not always the case. It sometimes happens that the peritoneal pouch comes down nearer to the prostate than usual we have seen it in actual contact with the gland ; so that, in such a case, it would be impossible to *. * In old age the rectum has sometimes a zigzag appearance immediately above the anus. These lateral inclinations are probably produced by the enormous dis- iensions to which the bowel has been occasionally subjected. 2 The bottom of the pouch is from three to four inches distant from the anus. 3 See a paper in the Med. Chir. Trans, vol. xxxv. by Mr. Cock. 502 PELVIC VISCERA. .tap the bladder from the rectum without going through the peri- toneum. In children the peritoneum comes down lower than it does in the adult, because the bladder in the child is not a pelvic viscus. The recto-vesical pouch is permanent. But there is another peritoneal pouch on the front part of the bladder, which is only produced when the bladder is distended. To produce it, the bladder should be blown up through one of the ureters. The FIG. 116. Peritoneum in dot- ted outline. Ureter. Vas deferens. Vesicula seminalis.. Symphysis pubis Corpus cavernosum penis Glans penis . . . Corpus spongiosum urethras . . . . Bulb of corp. spon- giosum . . . . Cowper's gland with duct Membranous part of urethra sur- rounded by com- pressor muscle. Prostate gland . DIAGRAM OF THE RELATIVE POSITION OF THE PELVI VISCERA. bladder soon fills the pelvis, and then, rising into the abdomen,, occasions the pouch between it and the abdominal wall. At first the pouch is shallow, but it gradually deepens as the bladder rises. If the bladder be distended half-way up to the umbilicus, which is commonly the case when it has to be tapped, we find that the bottom of the pouch would be about two inches from the symphysis pubis (fig. 116). Within this distance from the symphysis, the bladder may be tapped in the linea alba, without risk of wounding the peritoneum. Thus, the surgeon has the choice of two situations in which he may tap the bladder above the os pubis, or from the CONTENTS OF THE FEMALE PELVIS. 503 rectum. Which of the two be more appropriate, must be decided by the circumstances of the case. FALSE LIGAMENTS The reflections of the peritoneum from the OF THE BLADDEB. pelvic walls to the bladder constitute the false ligaments of the bladder, and they can be best examined before the viscera are disturbed, although they will be described when the bladder itself is dissected. The two posterior pass forwards from the sides of the rectum to the back of the bladder, forming the lateral boundaries of the deep recto-vesical pouch. Each contains within its duplicature the ob- literated hypogastric artery, the ureter, together with some vessels and nerves. The two lateral pass inwards from the sides of the pelvis to the sides of the bladder. The superior passes upwards from the summit of the bladder to the back of the anterior abdominal wall, covering the urachus and the obliterated hypogastric arteries. CONTENTS OF The relative positions of the pelvic viscera in THE FEMALE the female should now be examined, leaving the PELVIS. special description till a later stage. GENERAL ^e u t erus i g interposed between the bladder in POSITION OF THE front, and the rectum behind. From each side of UTERUS AND ITS ft a broad fold of peritoneum extends transversely APPENDAGES. to ^ gide of the pelvis, dividing that cavity into an anterior and a posterior part. These folds are called the broad ligaments of the uterus (fig. 135, p. 571). On the posterior surface of the ligament are the ovaries, one on each side. They are com- pletely covered by peritoneum, and suspended to the ligament by a small peritoneal fold. Each ovary is attached to the uterus by a cord termed the ligament of the ovary. Along the upper part of the broad ligament we find between its layers a tube about four inches long, called the Fallopian tube, which conveys the ovum from the ovary into the uterus. For this purpose, one end of it terminates in the uterus, while that nearer to the ovary expands into a wide mouth, furnished with prehensile fringes fimbrice which, like so many tentacles, grasp the ovum as soon as it escapes from the ovary. One of these fimbriae is attached to the ovary. Lastly, there 504 PELVIC VISCERA IN THE FEMALE. run up to the ovary, between the layers of the broad ligament, the ovarian vessels, which arise from the aorta in the lumbar region, like the spermatic arteries in the male, because the ovaries are originally formed in the loins. On the anterior surface of the broad ligament, on either side between its layers, is the round ligament of the uterus. This cord proceeds from the fundus of the uterus, anterior to the Fallopian tube, through the inguinal canal, like the spermatic cord in the FIG. 117. Urethra surround ed by its compres sor muscle . . Vagina Rectum Peritoneum in dotted outline. VERTICAL SECTION THROUGH THE FEMALE PELVIC VISCERA. male, and terminates in the mons Veneris. Besides one or two small blood-vessels, it contains muscular fibres analogous to those of the uterus ; these increase very much in pregnancy, so that, about the full term, the cord becomes nearly as thick as the end of the little finger. In early life, the round ligament receives a cover- ing from the peritoneum, which advances in a tubular form into the inguinal canal. It corresponds to the processus vaginalis of DISSECTION OF THE MALE PERINEUM. 505 the peritoneum in the male. It is called the canal of Niick, and is generally obliterated in the adult. It is sometimes the seat of an inguinal hernia. RELECTIONS From the front of the rectum the peritoneum is OF THE PERI- reflected on to a small part of the posterior wall of TONZUM. the vagina, thus forming what is called the recto- vaginal pouch. From the vagina the peritoneum is continued over the posterior surface, but only about half-way down the front of the uterus ; thence it is reflected over the posterior surface of the bladder, on to the wall of the abdomen. Laterally, it is reflected from the uterus to the sides of the pelvis, forming the broad liga- ments (p. 571). In cases of ascites the fluid might distend the recto-vaginal pouch, and bulge into the vagina, so that it would be practicable to draw it off through this channel. FIG. 118. DISSECTION OF THE MALE PERINEUM. Before dissecting the perineum, it is expedient first to examine the osseous and ligamentous boundaries of the lower aperture of the pelvis. Looking at the male pelvis (with the ligaments pre- served), we observe that this aperture is of a lozenge shape ; that it is bounded in front by the pubic arch and the sub- pubic ligament; laterally, anteriorly, by the rami of the os pubis and ischium, and the tuberosity of the ischium, posteriorly, by the great sciatic ligament ; and behind, by the tip of the coccyx. This space, for convenience of de- scription, is subdivided into two by a line drawn from one tuber ischii to the other. The anterior forms a nearly equilateral triangle, of which the sides are from three to three and a half inches long ; and, since it transmits the urethra, it is called DIAGRAM OF THE FRAMEWORK OF THE PERINEUM. 506 DISSECTION OF THE MALE PERINEUM. the uretkral region of the perineum. The posterior, containing the anus, is called the ischio-rectal or anal region (fig. 118). 1 The subject should be placed in the usual position for lithotomy,, with a block placed beneath the pelvis. A full-sized staff should now be passed into the bladder, the rectum moderately distended with tow, and the scrotum raised by means of hooks. A central ridge, named theraphe, extends from the anus, along the perineum, scrotum, and under surface of the penis. Between the tuberosities of the ischia and the anus are two depressions, one on each side, marking the ischio-rectal fossce, which are found immediately be- neath the skin, filled with more or less fat. In the lateral opera- tion of lithotomy, the incision should commence at a point midway between the anus and the posterior fold of the scrotum, close to the left side of the raphe ; it should be carried downwards and outwards to a point midway between the tuber ischii and. the anus. In the bilateral operation, the incision is semilunar, the horns being made on either side between the tuber ischii and the anus, equidistant from these points respectively ; while the centre of the incision runs about three-quarters of an inch above the anus. At the anus the skin becomes finer and more delicate, forming a gradual transition towards mucous membrane : during life it is drawn into wrinkles by the permanent contraction of the cutaneous sphincter. Moreover, the skin at the margin of the anus is provided with numerous minute glands, 2 which secrete an unctuous substance to facilitate the passage of the fasces. When this secretion becomes defective or vitiated, the anal cutaneous folds are apt to become excoriated, chapped, or fissured ; and then defalcation becomes very painful. At the margin of the anus a thin white line can be distinguished, indicating, not only the junction of the skin with the mucous mem- 1 The dimensions of the lower outlet of the pelvis are apt to vary in different subjects, and the lithotomist must modify his incision accordingly. 2 These glands are the analogues of the anal glands in some animals, e.g. the dog and the beaver. They are found not only about the anus, but also in the sub- cutaneous tissue of the perineum, a fact for the demonstration of which we are. indebted to the late Professor Quekett. They are large enough to be seen with the naked eye. ISCHIO-RECTAL FOSSAE. 507 brane, but also the linear interval between the external and internal sphincters. 1 The skin should be reflected, by making an in- DISSECTION cision along the raphe, round the margin of the anus to the coccyx. Two others must be made on each side at right angles to the first, the one at the upper, and the other at the lower end of it. The skin of the perineum must then be reflected SUBCUTANEOUS outwards with much care, otherwise the superficial TISSUE. sphincter ani may be reflected with the skin. In reflecting the skin, notice the characters of the subcutaneous struc- ture. 2 Its characters alter in adaptation to the exigencies of each part. On the scrotum the fat constituent of the tissue is entirely absent ; while the connective tissue element is most abundant, and during life elastic and contractile. But, towards the deeper part FAT IN ISCHIO- of the anus, the fat accumulates more and more, BECTAL Fossa:. an d on either side of the rectum it is found in the shape of large masses, filling up what would otherwise be two deep hollows in this situation namely, the ischio-rectal fossce. These fossae are pyramidal, with their bases towards the skin, and their apices at the divergence of the obturator internus and levator ani. They are about two inches in depth, and much deeper posteriorly than in front. This accumulation of fat on each side of the anus permits the easy distension and contraction of the lower end of the bowel during and after the passage of the fseces. Over the tuberosities of the ischia are large masses of fat, separated by tough, fibrous septa, passing from the skin to the bone, so as to make an elastic padding to sit upon. Occasionally, too, there are one or more large Inirsce, interposed between this padding and the bone. So much respecting the general characters of the subcutaneous tissue of the perineum. Some anatomists describe it as consisting of three, four, or even more layers, but in nature we do not find it 1 Hilton, Lectures on Eest and Pain, p. 280. 2 The probable thickness of this subcutaneous tissue is a point which ought ta be determined by the lithotomist in making his first incision. Its great thickness in some cases explains the depth to which the surgeon has to cut in letting out pus from the ischio-rectal fossa. 508 CUTANEOUS VESSELS AND NERVES OF THE PERINEUM. so. It may, indeed, be divided into as many layers as we please, according to our/ skill in dissection ; but this only complicates what is, in itself, simple. The external sphincter ani must now be cleaned, care being taken not to remove any of its fibres, which are intimately connected with the skin. Posteriorly, the lower border of the gluteus maximus must be displayed, and the Vessels and nerves crossing the perineum, towards the anus, care- fully dissected. 1 EXTERNAL The external sphincter of the anus is elliptical, SPHINCTER ANI. and is composed of a thin layer of striped mus- cular tissue about an inch in breadth. It arises from the tip of the coccyx and the ano-coccygeal ligament. The muscular fibres surround the anus, and are inserted in a pointed manner in the tendinous centre of the perineum, in conjunction with the trans- versus perinei, the accelerator urines, and the levator ani (p. 510). It is called the external sphincter, to distinguish it from a deeper and more powerful band of muscular fibres which surrounds the last inch or more of the rectum, and is situated next to the mucous membrane. CUTANEOUS ^h cutaneous vessels and nerves of the peri- VESSELS AND neum come from the internal pudic artery and NEKVES. nerve, and chiefly from that branch of it called the superficialis perinei. This will be traced presently. The external or inferior hcemorrhoidal arteries cross transversely through the ischio-rectal fossa, from the ramus of the ischium to- wards the anus. They come from the pudic (which can be felt on the inner side of the ischium), and, running inwards, divide into numerous branches, which supply the rectum, levator ani, and sphincter ani. The nerves which accompany the arteries come from the pudic nerve, and supply the sphincter ani and the skin of the perineum. The fourth sacral nerve emerges through the coccygeus close to the tip of the coccyx, and, through its hcemorrhoidal or perineal 1 Radiating outwards from the margin of the anus is a thin stratum of involuntary muscular fibres, called the corrugator cutis ani, which by its action produces the radiating ridges of skin from the anus. SUPERFICIAL FASCIA OF THE PERINEUM. 509 branch, supplies the external sphincter and the skin of the perineum between the coccyx and the anus. The inferior pudendal nerve comes through the muscular fascia of the thigh, a little above the tuber ischii, and ascends, dividing into filaments, which supply the front and outer part of the scrotum and perineum. It is a branch of the lesser sciatic nerve, and com- municates in front with the posterior branch of the superficial perineal nerve. SUPERFICIAL The subcutaneous fascia of the perineum is FASCIA OP THE composed of a superficial and a deep layer. The superficial layer contains more or less fat, and is continuous with that of the scrotum, the thighs, and the posterior part of the perineum. The deeper layer is a stratum of consider- able strength, and is best demonstrated by blowing air beneath it with a blow-pipe ; its connections are as follows : It is attached on each side to the anterior lip of the ramus of the os pubis and ischium superficial to the crus penis ; traced forwards, it is directly continuous with the tunica dartos of ,the scrotum ; traced backwards, at the base of the urethral triangle, it is reflected beneath the transversus perinei muscle, and joins the deep perineal fascia or triangular ligament. These connections explain why urine, effused into the perineum, does not make its way into the ischio-rectal fossae, or down the thighs, but passes readily forwards into the connective tissue of the scrotum, penis, and groins. Remove the fascia to see the muscles which cover the bulb of the urethra and the crura of the penis. The bulb of the urethra lies in the middle of the perineum, and is covered by a strong muscle, called accelerator urinse. The crura penis are attached, one to each side of the pubic arch, and are covered each by a muscle, called erector penis. A narrow slip of muscle, called transversus perinei, extends on either side from the tuber ischii to the tendinmis centre of the perineum. This point is about one inch and a quarter in front of the anus, and serves for the attachment of muscular fibres from all quarters of the perineum. Thus the muscles of the perineum describe on each side a 510 SUPERFICIAL FERINE AL VESSELS AND NERVES. triangle, of which the sides are formed by the accelerator u rinse and the crus penis respectively, and the base by the transversus perinei. Across this triangle run up from base to apex the super- ficial perineal vessels and nerves. External to the ramus of the ischium is seen the inferior pudenda! nerve, a branch of the lesser sciatic. FIG. 119. Triangular liga- ment . .] I. . Tendinous centre of the perineum Transversus peri- nei Ischio-rectal fossa . . Superficialis - perinei a. 7' External hie- ,'/ morrhoid u. and n. MUSCLES, WITH SUPERFICIAL VESSELS AND NERVES, OF THE PERINEUM. SUPERFICIAL superficial perinea! artery lies beneath the PERINEAL VESSELS deep layer of the superficial perineal fascia, and AND NERVES. comes from the internal pudic as it runs up the ACCELERATOR URIN.E. 511 inner side of the tuber ischii. Though the main trunk cannot be seen, it can be easily felt by pressing the finger against the bone. The artery comes into view a little above the level of the anus, passes up usually in front of the transversus perinei muscle, and gets to the perineal triangle lying to the inner side of the erector penis. It distributes branches to all the muscles, and is finally lost on the scrotum. The only named branch is called transversalis perinei (fig. 119). This is given off near the base of the triangle, and runs transversely inwards with the transversus perinei muscle towards the central tendon of the perineum, where it anastomoses with its fellow. It is necessarily divided in the first incision in lithotomy, and deserves attention, because it is sometimes of con- siderable size. The artery is accompanied by two veins, which are frequently dilated and tortuous^ especially in diseased conditions of the scrotum. The nerves, two in number, are derived from the internal pudic, follow the course of their corresponding arteries, and give off similar branches. They not only supply the skin of the perineum and scrotum, but each of the perineal muscles. ACCELERATOR This muscle embraces the bulb of the urethra, UKIN^:. and is composed of two lateral symmetrical halves. It arises from a fibrous median raphe beneath the bulb, and from the tendinous centre of the perineum. Starting from this origin, the fibres diverge, and are inserted as follows : The upper ones proceed on either side round the corpus cavernosum penis, like the branches of the letter V, and are fixed on its dorsal surface, in front of the erector penis, and expanding also into a broad apo- neurosis, which covers the dorsal vessels of the penis ; the middle completely embrace the bulb and adjacent part of the corpus spongiosuiii like a ring, and meet in an aponeurosis on the upper surface of the urethra ; the lower are fixed to the anterior surface of the deep perineal fascia, often called the triangular ligament (fig. 120).' Thus, the entire muscle acts as a powerful compressor of the 1 This muscle is called also the ejaculator urince or the bulbo-cavernosus. 512 MUSCLES OF THE PEKINEUM. bulb, and expels the last drops of urine from this part of the urethra. 1 By dividing the muscle along the middle line and turning back each half, its insertion, as above described, can be clearly made out. ERECTOR This muscle is moulded upon the crus of the PENIS. penis. It arises by musculo-tendinous fibres from the inner surface of the tuber ischii, from the crus itself, and from the ramus of the os pubis ; the fibres ascend, completely covering the crus, and terminate on a strong aponeurosis, which is inserted FIG. 120. Corpus cavernosum Corpus spongi Upper fibres Middle fibres Lower fibres Tendinous centre of peri- neum COWPERS TRIANGULAR L 'CAMENT DIAGRAM TO SHOW THE ACCELERATOR URIN/E IN PROFILE. into the external and inferior aspect of the crus penis. The action of this muscle is to compress the root of the penis, and so, by pre- venting the return of the venous blood, contributes to the erection of the organ. 2 THANSVERSUS This muscle is of insignificant size, and some- PERINEI. times absent. It arises from the inner aspect of the tuber ischii, and proceeds forwards and inwards towards the 1 The oniddle fibres assist in the erection of the corpus spongiosum, and the upper fibres in that of the penis : the former by compressing the bulb, the latter by compressing the dorsal vein. 2 This muscle is sometimes called the ischio-cavernosus. MUSCLES OF THE PERINEUM. 513 central point of the perineum, where it is blended with the muscle of the opposite side, with the fibres of the accelerator urinaD in front, and with the external sphincter behind. This muscle with its artery is divided in lithotomy. Cms penis . . . Cms penis with its artery cut through . . , Ramus. of the os pubis . . . . Artery of the bulb Co wper's gland. . Pudic artery . . . Tuber ischii . . . PIG. 121. DIAGRAM TO SHOW THE TRIANGULAR LIGAMENT OF THE URETHRA OR DEEP PEKINEAL FASCIA. The deep transversus perinei is a small muscle occasionally present ; it arises more deeply from the pubic arch than the super- ficial muscle, and passes inwards behind the bulb to the central tendon. L L 514 TRIANGULAR LIGAMENT. The next stage of the dissection consists in reflecting and removing the accelerator urinas from the bulb of the urethra, the erectores penis with the crura penis from the rami of the os pubis PIG. 122. Compressor urethra Membranous part of the urethra surrounded by its compressor muscle. Prostate gland . . Anterior fibres the levator aui of DIAGRAM OF THE PARTS BEHIND THE ANTERIOR LAYER OF THE TRIANGULAR LIGAMENT OF THE URETHRA. (The anterior fibres of the levator ani are hooked down to show part of the prostate ; the rest is tracked by a dotted line.) and ischium, and the transversi perinei muscles. This done, the triangular ligament or deep perinecd fascia is fairly exposed. TRIANGULAR LIGAMENT. 515 TRIANGULAR Understand that the triangular ligament of the LIGAMENT OF THE urethra and the deep perineal fascia are synony- URETHRA. mous terms. The triangular ligament, shown in fig. 122, is a strong fibrous membrane stretched across the pubic arch. It is about an inch and a half in depth, with the base directed backwards. It con- sists of two layers an anterior and a posterior. The anterior layer is firmly attached on each side to the posterior lip of the rami of the os pubis and ischium, beneath the crus penis ; superiorly i.e., towards the symphysis of the os pubis it is connected with the subpubic ligament ; inferiorly, it does not present a free border, but is connected to the tendinous centre of the perineum, and is continuous with the deep layer of the superficial perineal fascia which curves backwards under the transversus perinei muscle, and with the ischio-rectal or anal fascia (p. 509). The anterior layer of the triangular ligament is perforated about one inch below the symphysis pubis for the membranous part of the urethra. The aperture through which the urethra passes does not present a distinct edge, because the ligament is prolonged forwards over the bulb, and serves to keep it in position. It also presents apertures for the transmission of the dorsal vein, and outside this for the pudic arteries and nerves. The posterior layer cannot at present be seen. It belongs, strictly speaking, to the obturator prolongation of the pelvic fascia, and slopes somewhat backwards from the anterior layer so as to leave an interval between them, in which are found structures which will be presently described. POINTS OF SUR- The triangular ligament is very important GICAL INTEREST. surgically for these reasons : 1. Here we meet with difficulty in introducing a catheter, unless we can hit off the right track through the ligament. The soft and spongy tissue of the bulbous part of the urethra in front of the ligament readily gives way if force be used, and a false passage results. 2. By elongating the penis, we are much more likely to hit off the proper opening through the ligament. 3. When, in retention of urine, the urethra gives way anterior L L 2 516 PARTS DIVIDED IN LATERAL LITHOTOMY. to this ligament, it is this which prevents the urine from travelling into the pelvis. Its connection with the superficial permeal fascia prevents the urine from getting into the ischio-rectal fossae : nor can the urine make its way into the thighs. The only outlet for it is into the connective tissue of the scrotum and penis. 4. When suppuration or extravasation of urine takes place behind the ligament, the pus is pent up and should be speedily let out ; if not, it may find its way into the connective tissue of the pelvis, and may burst into the urethra or the rectum. 5. The ligament is partially cut through in lithotomy. PARTS DIVIDED The parts divided in the lateral operation of IN LATERAL lithotomy are : the skin, the superficial fascia, the LITHOTOMY. ^ transverse perineal muscle, vessels and nerve, the inferior haemorrljioidal vessels and nerves, the inferior fibres of the accelerator urinse, the anterior fibres of the levator ani, the tri- angular ligament (anterior layer), the compressor urethras, the membranous and prostatic parts of the urethra, and a small portion of the prostate. PARTS TO BE The incision in lateral lithotomy should not AVOIDED. be made too far forwards, for fear of wounding the artery of the bulb ; nor too far inwards, for fear of injuring the rectum ; nor too far outwards, for fear of cutting the pudic artery. The anterior layer of the triangular ligament BETWEEN THE must now be cut away to see what lies between LAYERS OF THE its two layers. These parts are shown in fig. 122 ; TRIANGULAR namely : 1 , the membranous part of the urethra, surrounded by, 2, the compressor urethras muscle ; 3, Cowper's glands and their ducts ; 4, the pudic artery and its branch, the artery of the bulb ; the artery of the crus and the dorsal artery of the penis being given off in front of the anterior layer ; 5, the pudic nerve and its branches ; 6, the dorsal vein of the penis ; 7, the subpubic ligament. To obtain the best perineal view of the com- pressor urethrae muscle, cut through the spongy part of the urethra about three inches above the end of the bulb, and dissect it from the corpus cavernosum. Thus, the upper fibres PUDIC ARTERY AND ITS BRANCHES. 517 of the constrictor will be exposed ; to see the lower, it is only necessary to raise the bulb. The most perfect view, however, of the muscle is obtained by making a transverse section through the rami of the ossa pubis, so as to get at the muscle from above, as shown in fig. 123. COMPRESSOR OB This muscle consists of transverse fibres which CONSTRICTOR surround and support the whole length of the URETHRA. membranous portion of the urethra in its passage between the two layers of the triangular ligament. It arises from the ramus of the os pubis on either side for about half an inch ; from thence its fibres pass, some above, some below the urethra, along the whole length of its membranous part. It forms a com- plete muscular covering for the urethra between the prostate and the bulb. It is chiefly through its agency that we retain the urine. This muscle is the chief cause of spasmodic stricture of the urethra. 1 Besides this muscle, the membranous portion of the urethra is surrounded by involuntary circular muscular fibres, placed beneath the compressor urethras, and continuous with the muscular fibres of the bladder. COWPER'S These small glands are situated, one on either GLANDS. side, immediately behind the bulb between the two layers of the triangular ligament, in the substance of the compressor urethrae. Their size is about that of a pea, but it varies in different individuals. They are compound racemose glands, consisting of several lobules firmly connected together by cellular and some muscular tissue. From each a slender duct runs forwards, and, after a course of about one inch, opens obliquely into the floor of the bulbous part of the urethra (fig. 120). They furnish a secretion accessory to generation. PUDIC ARTERY The internal pudic artery is a branch of the AND ITS anterior division of the internal iliac. It leaves BRANCHES. ^e p e i v j s through the great sciatic foramen be- tween the pyriformis and coccygeus muscles, above the sciatic artery, winds round the spine of the ischium, re-enters the pelvis 1 The compressor urethrse was first accurately described and delineated by Santorini (septemdec. tabulas), and afterwards by Muller in his monograph (Ueber die organ. Nerv. der mannlich. Geschlechtsorgane). 518 INTERNAL PUDIC ARTERY. through the lesser sciatic foramen, and then runs along the inner side of the tuber ischii, between the layers of the obturator fascia, up towards the pubic arch. About an inch and a half above the tuber ischii, the trunk of the pudic artery can be felt ; but we Catheter . . . . Dorsal nerve of the penis Dorsal artery of tlie pnnis . . . Dorsal vein of the penis Anterior layer of triangular liga- ment Ramus of os pnbis cut through . . Posterior layer of triangular liga- ment : part of the pelvic fascia. FIG. 123. DIAGRAM OF THE RELATIONS OF THE COMPRESSOR URETHRA SEEN FROM ABOVE. cannot see it, nor draw it out, for it is securely lodged in a fibrous canal formed by the obturator fascia. It subsequently pierces the posterior layer of the triangular ligament, runs along the inner INTERNAL PUDIC ARTERY. 519 margin of the ramus of the os pubis, and lastly, piercing the anterior layer of the triangular ligament, it divides into the artery of the corpus cavernosum and the dorsal artery of the penis. In the present dissection we find the artery between the two layers of the triangular ligament, where it gives off the artery of the bulb of the urethra, and then pierces the triangular ligament (fig. 121). Taken in order, the branches of the pudic artery as seen in this dissection are : a. The external hwmorrhoidal the superficial perineal, and the transverse perineal branches have already been described (pp. 508, 510). b. The artery of the bulb is of considerable size, and passes trans- versely inwards between the two layers of the triangular ligament ; it runs inwards through the substance of the compressor urethras, and before it enters the bulb divides into two or three branches. It also sends downwards a small branch to Cowper's gland. From the direction of this artery it will at once strike the attention that there is great risk of dividing it in lithotomy. If the artery run along its usual level, and the incision be not made too high in the perineum, then indeed it is out of the way of harm. But, supposing the reverse, the vessel must be divided. This deviation from the normal distribution is met with about once in twenty subjects, and there is no possibility of ascertaining this anomaly beforehand. c. The artery of the corpus cavernosum, one of the terminal branches, ascends for a short distance near the pubic arch, and soon enters the crus, running forwards in its cavernous structure by the side of the septum pectiniforme. d. To see the dorsal artery of the penis, the crus should be dissected from its attachment to the symphysis pubis. The artery pierces the suspensory ligament, and can be traced upon the clorsurn of the penis down to the glans. It forms a complete arterial circle with its fellow round the corona glandis, and gives numerous ramifications to the papillae on the surface. The veins corresponding with the branches of the pudic artery terminate in the pudic vein, with the exception of the dorsal vein of the penis. This vein is of large size and results from the union of two small veins in front of the dorsum of the penis which receive the blood from the glans, the corpus spongiosum, and the prepuce. 520 ISCHIO-RECTAL FOSSA. The vein runs along the middle of the dorsum, pierces, first, the suspensory ligament, and then the triangular ligament under the symphysis, and divides into two branches which open into the prostatic plexus. The pudic nerve comes from the lower part of PUDIC NERVE. . , . the sacral plexus, and corresponds, both in its course and branches, with the artery. It gives off, close to its origin, (a) the external or inferior hcemorrhoidal, which communi- cate in front with the superficial perineal and inferior pudendal nerves ; (>) the perineal which accompanies the superficial perineal artery, and divides into a posterior and an anterior branch ; the former runs to the front of the; ischio-rectal fossa, distributing branches to the sphincter and tjae skin in front of the anus ; the latter lies in front of the preceding, and supplies the scrotum and under aspect of the penis ; both communicate with each other and with the inferior pudendal nerve ; (c) muscular lyranclies to the transversus perinei, the accelerator urines, the erector penis, and the compressor urethrse ; (d) the dorsal nerve, which is the main trunk of the nerve, runs with the pudic artery, and with it pierces the posterior, and then the anterior layer of the triangular ligament ; then perforating the suspensory ligament of the penis, it ac- companies the dorsal artery on its outer side, along the dorsum of the penis to the glans. In its passage it supplies the integuments of the penis, and sends off one or two branches into the corpus cavernosum. This part of the penis also receives filaments from the sympathetic system. ISCHIO-BECTAL This is the deep hollow, on each side, between FOSSA. the anus and the tuber ischii. When all the fat is removed from it, observe that it is lined on all sides by fascia. Introduce the finger into it to form a correct idea of its extent and boundaries. Externally, it is bounded by the tuber ischii and the fascia covering the obturator internus muscle ; internally, by the rectum, levator ani and coccygeus ; posteriorly, by the gluteus maximus ; anteriorly, by the transversus perinei. The fossa is crossed by the external haamorrhoidal vessels and nerves. These deep spaces on each side of the rectum explain the great size which abscesses in this situation may attain. The matter can DISSECTION OF THE FEMALE PEEINEUM. 521 be felt only through the rectum. Nothing can be seen outside. Perhaps nothing more than a little hardness can be felt by the side of the anus. These abscesses should be opened early ; else they form a large cavity, and may burst into the rectum, and result in a fistula. DISSECTION OF THE FEMALE PEKINEUM. The pudenda in the female consist of folds of the integument, called the labia. Between these is a longitudinal fissure which leads to the orifices of the urinary and genital canals. The pubic region is generally surmounted by an LABIA MAJOEA. * % , J ^ . *., accumulation ot tat, called mons venens, which is covered with hair. From this, two thick folds of skin descend, one on either side, constituting the labia majora, and gradually diminish in thickness towards the perineum. Their junction, about an inch above the anus, is called the posterior commissure, orfrcenulum labiorum, within which is a transverse crescentic fold, the fourclietie : it is generally torn in the first labour. Between the fourchette and the posterior commissure is an oval depression, called the fossa navicularis. The inner layer of the skin of the labium is thinner, softer, and more like mucous membrane than the outer ; for this reason, whenever pus forms in the labium, the abscess bursts on the inner side. Where the labia are in contact, they are provided with small sebaceous glands, of which the minute ducts are observable on the surface. They are the analogues of the scrotum in the male, and occasionally contain extruded ovaries, forming a hernia of the ovary. 1 In form and structure the clitoris resembles the penis on a diminutive scale, being about an inch and a half long. It has, however, no corpus spongiosum, or urethra. Like the penis, it is attached to the sides of the pubic arch by two crura (fig. 124, p. 524), each of which is grasped by its special erector ditoridis. The crura are continued forward like 1 See paper on ' Hernia of the Ovary,' St. Bartholomew's Hospital Reports, vol. xviii. 522 DISSECTION OF THE FEMALE PERINEUM. the corpora cavernosa of the male, and unite to form the body of the organ, which is surmounted by a small ylans. It has also, like the penis, a suspensory ligament. The glans is provided with extremely sensitive papillee, and covered by a little prepuce. Its dorsal arteries and nerves are large in proportion to its size, and have precisely the same course and distribution as in the penis. Its internal structure consists of a plexus of blood-vessels, which freely communicate with those of the labia minora ; for one cannot be injected without the. other. LABIA MINORA By separating the external labia, two small and OK NYMPHS. thin folds of mucous membrane about an inch and a half in length, are exposed, x ^one on either side, termed labia minora. These folds converge anteriorly, and form a covering for the clitoris, called preputium clitoridis ; posteriorly, they are gradu- ally lost on the inside of the labia majora. They, unlike the labia majora, do not contain fat, but are composed of minute veins. Between the nymphse and about the clitoris are a number of seba- ceous glands. Between the labia minora, and below the clitoris, is an angular depression called the vestibule, at the back of which is the meat-its urinarius. Immediately below this is the vagina, of which the orifice is partially closed in the virgin by a thin fold of mucous membrane called the hymen. The hymen is a thin fold of mucous membrane which, in the virgin, extends across the lower part of the entrance of the vagina, about half an inch behind the four- chette. In most instances its form is crescent-shaped, with the concavity upwards. There are several varieties of hymen : some- times there are two folds, one on either side, so as to make the entrance of the vagina a mere vertical fissure ; ! or there may be a septum perforated by several openings, hymen onbriformis, or by one only, hymen circularis. Again, there may be no opening at all in it, and then it is called hymen imperforatus. Under this last condition no inconvenience arises till puberty. The menstrual discharge must then necessarily accumulate in the vagina : indeed, 1 Such a one may be seen in the Museum of the College, Phys. Series No. 2843. DISSECTION OF THE FEMALE PERINEUM. 523 the uterus itself may become distended by it to such an extent as even to simulate pregnancy. 1 When the hymen is ruptured, it shrivels into a few irregular eminences, called carunculce myrtiformes. The presence of the hymen is not necessarily a proof of vir- ginity, nor does its absence imply the loss of it. Cases are re- lated by writers on midwifery in which a division of the hymen was requisite to facilitate parturition. In Meckel's Museum, at Halle, are preserved the external organs of a female in whom the hymen is perfect even after the birth of a seven-months' child. BARTHOLIX'S Between the orifice of the vagina and the erector OB DUVEBNEY'S clitoridis is imbedded in the loose tissue on either GLANDS. s [^ e a sma u gland, 2 which corresponds to Cowper's gland in the male. Each is about half an inch in length. Its long slender duct runs forwards and opens on the inner side of the nympha external to the hymen. In cases of virulent gonorrhoea these glands are apt to become diseased, and give rise to the formation of an abscess in the labium, very difficult to heal. A smooth channel, called the vestibule, three- quarters of an inch in length, leads from the clitoris down to the orifice of the urethra. This orifice, meatus urinarius, is not a perpendicular fissure like that of the penis, but rounded and puckered, and during life has a peculiar dimple- like feel, which assists us in finding it when we pass a catheter. You should practise the introduction of the catheter in the dead subject, for the operation is not so easy as might at first be ima- gined, provided the parts are not exposed. The point of the fore- finger of the left hand should be placed at the entrance of the vagina, and the meatus felt for ; when the catheter, guided by the finger, slips, after a little manoeuvring, into the urethra. The canal is about one inch and a half in length, and runs along the upper wall of the vagina. The two canals are in such close apposition that you can feel the urethra imbedded in the vagina like a thick cord. The urethra is slightly curved with the concavity upwards ; but for all practical purposes it may be con- 1 See Burn's Midwifery. 2 See Tiedemann, Yonder Duverneyschen Driisen des Weibs. Heidelberg, 1840. 524 DISSECTION OF THE FEMALE PERINEUM. sidered straight. Its direction, however, is not horizontal. In the unimpregnated state it runs nearly in the direction of the axis of the outlet of the pelvis ; so that a probe pushed on in the course of the urethra would strike against the promontory of the sacrum. But, after impregnation, when the uterus begins to rise out of the pelvis, the bladder is more or less raised also in con- sequence of their mutual connection ; therefore the urethra, in the latter months of utero-gestation, acquires a much more perpendi- cular course. The female urethra is provided with a compressor muscle, similar, in origin and arrangement, to that which surrounds the membranous part of the urethra in the male. It also passes through the triangular ligament. The prostate gland is wanting, FIG. 124. 1. Meatus urinarius. / j%C2a^^. \ 3 - Bulb ^ vagina. 2. Vagina. /^~r*sF*lV\ \ 4 - Clitoris with its two crura. BULB OF THE VAGINA but there are minute glands scattered around the neck of the bladder. In consequence of the wider span of the pubic arch, and the more yielding nature of the surrounding structures, the female urethra is much more dilatable than the male. By means of a sponge-tent, it may be safely dilated to admit the easy passage of the fore-finger into the bladder. Advantage is taken of this great dilatability in the extraction of calculi from the bladder. The mucous coat of the urethra is pale and arranged in longi- tudinal folds, and is lined by squamous epithelium, which changes to the spheroidal variety near the bladder. Next to the mucous coat is a layer of elastic and non-striped muscular fibres inter- mixed. The muscular tissue is arranged in two layers an outer, consisting of circular fibres, and an inner of longitudinal fibres. 1 Taken from an injected preparation in the Mus6e Orfila, at Paris. DISSECTION OF THE SIDE VIEW OF THE PELVIS. 525 Externally there is a plexus of veins bearing a strong resemblance to erectile tissue. The vagina is the canal which leads to the uterus ; at present, only the orifice of it can be seen. It is surrounded by a sphincter muscle, easily displayed by removing the integument. The muscle is about three-fourths of an inch broad, and connected with the cutaneous sphincter of the anus in such a manner that they together form something like the figure 8. On each side of the orifice of the vagina, between the mucous membrane and the sphincter, is a plexus of tortuous veins, termed the bulb of the vagina, from its analogy to the bulb of the urethra in the male. This vaginal bulb is about an inch long and extends across the middle line between the meatus urinarius and the clitoris, as shown in fig. 124. The description of the perineal branches of the pudic vessels and nerves, given in the dissection of the male perineum, applies, mutatis mutandis, to the female, excepting that they are propor- tionably small, and that the artery which supplies the bulb of the urethra in the male is distributed to the bulb of the vagina in the female. ANATOMY OF THE SIDE VIEW OF THE PELVIC VISCERA. To obtain a side view of the pelvic viscera, the left innominate bone should be removed thus : Detach the peritoneum and the levator ani from the left side of the pelvis, cut through the external iliac vessels, the obturator vessels and nerve, and the nerves of the lumbar plexus ; then saw through the os pubis about two inches external to the symphysis, and cut through the sacro-iliac symphysis ; now draw the legs apart, and saw through the base of the spine of the ischium ; after cutting through the pyriformis, the great sacro-sciatic ligament, the great and small sciatic nerves, and the gluteus maximus muscle, the innominate bone can be easily detached. This done, the rectum 526 SIDE VIEW OF THE PELVIC VISCEEA. should be distended with tow, and the bladder blown up through the ureter. A staff should be passed through the urethra into the bladder, and a block placed under the sacrum. The reflection of the peritoneum as it passes from the front of the rectum to the lower part of the bladder (forming the recto- vesical pouch), and thence over the back of the bladder to the wall of the abdomen, has been already described. You see where the FIG. 125. Peritoneum in clotted out- line. . . . Corpus cavern- osum penis . Triangular ligament . . Prostate VERTICAL SECTION THROUGH THE PERINEUM AND PELVIC VISCEEA. (The arrows point out where the bladder can be tapped.) distended bladder is bare of peritoneum, and that it can be tapped either through the rectum or above the pubes without injury to the serous membrane, as shown by the arrows in fig. 125. FALSE LIGA- ^ ne peritoneal connections of the bladder are MENTS OF TUB called its false ligaments ; false in contradistinction BLADDER. to the true, which are formed by the fascia of the SIDE VIEW OF THE PELVIC VISCERA. 527 pelvis, and really do sustain the neck of the bladder in its proper position. The false ligaments are five in number, two posterior, two lateral, and one superior. The posterior are produced by two peritoneal folds, one on either side the recto-vesical pouch ; the two lateral, by reflections of the peritoneum from the sides of the pelvis FIG. 126. '<_ Iliac fascia covering iliacus. Pelvic fascia dividing. Obturator fascia covering obtu- rator interims. Recto-vesical layer covering levator ani. Anal fascia. TRANSVERSE SECTION OP THE PELVIS, TO SHOW THE REFLECTIONS OF THE PELVIC FASCIA. (AFTEB GEAY.) to the sides of the bladder; the superior. fa produced by the passage of the peritoneum from the front of the bladder to the abdominal wall. These have been already described (p. 503). To expose the pelvic fascia, the peritoneum PELVIC FASCIA. , * ' r . . must be removed from that side of the pelvis which has not been disturbed : in doing so, notice the abundance of loose connective tissue interposed between the peritoneum and 528 PELVIC FASCIA. the fascia, to allow the bladder to distend with facility. When- ever urine is extravasated into this loose tissue, it is sure to pro- duce the most serious consequences ; therefore in all operations on the perineum, it is of the utmost importance not to injure this fascia. The pelvic fascia is a thin but strong membrane, and constitutes the true ligaments of the bladder and the other pelvic viscera, sup- porting and maintaining them in their proper position. Examine, first, to what parts of the pelvis the fascia is attached ; secondly, the manner in which it is reflected on the viscera. Beginning, then (fig. 126), we see that, in front, the fascia is continuous with the transversalis fascia, and laterally with the iliac fascia, and that superiorly it is attached to the body of the os pubis, to the brim of the pelvis, and to the side of the bone just above the attachment of the obturator internus, close to the obturator foramen and the great sciatic notch. Here it becomes gradually thinner, covers the pyriformis and the sacral plexus, and is gradually lost on the front of the sacrum. Traced forwards, we find that it is attached to the bone along the upper border of the obturator internus, and, as it passes for- wards over the obturator foramen, completes the canal through which the obturator vessels pass to the foramen ; anteriorly, it is attached to the posterior surface of the lower part of the symphysis pubis. From this attachment the fascia descends as far as a line drawn from the spine of the ischium to the pubic symphysis, where it forms a dense white line which marks the division of the fascia into two layers, an outer, the obturator, and an inner, the recto-vesical fascia. It also serves for the attachment of a consider- able part of the middle portion of the levator ani. The obturator fascia, the outer layer, is the continuation of the pelvic fascia, and descends on the inner surface of the obturator internus, forming at the same time a sheath for the pudic vessels and nerve, the nerve being the lowest. It is attached to the pubic arch, to the tuberosity of the ischium, and to the margin of the great sacro-sciatic ligament. It is continuous in front, below the symphysis pubis, with the corresponding layer of the opposite side, and here forms the posterior layer of the triangular ligament. From this fascia is derived the iscJiio-^fectal or anal fascia, which PELVIC VISCERA IN THE MALE. 529 lines the under or perineal surface of the levator ani, and is subse- quently lost upon the side of the rectum. The recto-vesical fascia descends on the upper or internal surface of the levator ani, and invests the bladder, prostate, and rectum. From the symphysis pubis it is reflected over the prostate and the neck of the bladder to form, on either side of the symphysis, two well-marked bands the anterior true ligaments of the bladder. From the side of the pelvis it is reflected on to the side of the bladder, constituting the lateral true ligaments of that viscus, and encloses the prostate and the vesical plexus of veins. A prolonga- tion from this ligament encloses the vesicula seminalis, the lower layer of which passes between the bladder and the rectum, to join its fellow from the opposite side. The continuation of the recto- vesical fascia covers the remainder of the upper surface of the levator ani as far as its attachment to the rectum, where it is reflected round this tube. GENERAL ^^ e P 6 ^ viscera are so surrounded by veins POSITION OF THE and loose areolar tissue, that he who dissects them PELVIC VISCERA for the first time will find a difficulty in discovering IN THE MALE. ^eir definite boundaries. The rectum runs at the back of the pelvis, and follows the anterior curve of the sacrum and ooccyx. The bladder lies in front of the rectum, immediately behind the symphysis pubis. At the neck of the bladder is the prostate gland through which the urethra passes. In the cellular tissue, between the bladder and the rectum, there is, on each side, a convoluted tube, called the vesicula seminalis, and on the inner side of each vesicula is the seminal duct or vas deferens. Before describing these parts in detail, it is necessary to say a few words about the large tortuous veins which surround them. VESICO-PRO- Beneath the pelvic fascia surrounding the pro- STATIC PLEXUS state and the neck of the bladder are large and OF VEINS. tortuous veins, which form the prostatic and the vesical plexuses. They empty themselves into the internal iliac. In early life they are not much developed, but as puberty approaches they gradually increase in size, and one not familiar with the anatomy of these parts would hardly credit the size which they sometimes attain in old persons. They communicate freely behind M M 530 VESICO-PROSTATIC PLEXUS OF VEINS. with the inferior heemorrhoidal plexus, or veins about the anus, and they receive the blood returning from the penis through the large veins which pass under the pubic arch. If, in lithotomy, the incision be carried beyond the limits of FIG. 127. SIDE VIEW OF THE PELVIC VISCERA. (Taken from a Photograph.) 1. External sphincter. 2. Internal sphincter. 3. Levator ani cut through. 4. Accelerator urinte. 5. Membranous part of the urethra, sur- rounded by compressor muscle. 6. Prostate gland. 7. Vesicula seminalis. 8. Ureter. 9. Vas deferens. 10. Crus penis divided. 11. Triangular ligament. 12. Superficial perineal fascia. 13. Rectum. th e prostate, the great veins around it must necessarily be divided ; these, independently of any artery, are quite sufficient to occasion serious haemorrhage. RELATIONS OF THE RECTUM. 531 RECTUM AND The rectum is about eight inches long. It is a ITS RELATIONS. continuation of the sigmoid flexure of the colon, enters the pelvis at the left sacro-iliac articulation, describes a curve corresponding to the sacrum and coccyx, and terminates at the anus. The rectum also inclines from the left side to the middle line, and before its termination, the bowel turns downwards so that the anal aperture is dependent. Although it loses the sacculated appearance, it is not throughout of equal calibre and its capacity becomes greater as it descends into the pelvis ; immedi- ately above the sphincter, it presents a considerable dilatation, the ampulla (fig. 125). This dilatation is not material in early life, but it increases as age advances. Under such circumstances the rectum loses altogether its cylindrical form, and bulges up on either side of the prostate and the base of the bladder. For this reason the rectum should always be emptied before the operation of lithotomy. The rectum is conveniently divided into three portions, the upper, the middle, and the lower. The upper portion is about three inches and a half in length, and extends as low as the third bone of the sacrum, to which bone it is connected by a fold of peritoneum, termed the meso-rectum. In this fold, the terminal branch of the inferior mesenteric artery with its vein runs down to supply the bowel. This portion of the rectum has behind it, the sacral plexus of nerves, the pyriformis, and some branches of the left internal iliac artery ; in front, it has the bladder and the recto-vesical pouch. The middle portion comprises three inches in length, and is continuous with the lower portion at the tip of the coccyx. It is connected posteriorly to the sacrum and coccyx by loose connective tissue, and is covered by peritoneum only in front in the upper part, which forms the recto-vesical pouch. It has in front, the fundus of the bladder, the vesiculae seminales, the vasa deferentia and the prostate ; while in the female it is closely connected to the posterior wall of the vagina. The lower portion comprises the lowest inch and a half of the rec- tum. It is entirely destitute of peritoneum, and is supported by the levatores ani, the larger portions of which are inserted into its side ; it has also surrounding it, the internal, and lastly the external sphincters. M M 2 532 DIGITAL EXAMINATION OF THE RECTUM. There is a considerable interval between it and the membranous portion of the urethra in the male, and the vagina in the female. DIGITAL T ne relations of the front part of the rectum EXAMINATION OF that, namely, included between the recto-vesical THE KECTUM. pouch and the anus are most important. If the fore-finger be introduced into the anus, and a catheter into the urethra, the first thing felt through the front wall of the bowel is the membranous part of the urethral[n L g7l25). It lies just within the sphincter, and is about ten lines in front of the gut. About one and a half or two inches from the anus the finger comes upon the prostate gland ; this is in close contact with the gut, and is readily felt on account of its hardness ; by moving the finger from side to side we recognise its lateral lobes. Still higher up, the finger goes beyond the prostate, and reaches the trigone of the bladder : the facility with which this can be examined depends, not only upon the length of the finger and the amount of fat in the perineum, but upon the degree of distension of the bladder ; the more distended the bladder, the better can the prostate be felt. These several relations are practically important. They explain why, with the finger in the rectum, we can ascertain whether the catheter is taking the right direction whether the prostate be enlarged or not. We might even raise a stone from the bottom of the bladder so as to bring it in contact with the forceps. The rectum is supplied with blood by the superior, middle, and inferior haemorrhoidal arteries. The superior comes from the in- ferior mesenteric (p. 473) ; the middle from the anterior division of the internal iliac artery, and the inferior from the pudic artery. The superior haemorrhoidal veins join the inferior mesenteric, and consequently the portal system ; the middle and the inferior heemorrhoidal veins join the internal pudic, and thence the internal iliac vein. They are very large and form loop-like plexuses about the lower part of the rectum. Having no valves, they are liable to become dilated and congested from various internal causes ; hence the frequency of hsemorrhoidal affections. This viscus, being a receptacle for the urine, BLADDER. ., . . -. -.. , ,, must necessarily vary in size, and accordingly the nature of its connections and coats is such as to permit this POSITION OF THE BLADDER. 533 variation. When contracted, the bladder sinks into the pelvis behind the pubic arch, and is completely protected from injury. But, as it gradually distends, it rises out of the pelvis into the abdomen, and, in cases of extreme distension, may reach up to the umbilicus. 1 Its outline can then be easily felt through the walls of the abdomen. The form 2 of the distended bladder is oval, and its long axis, if prolonged, would pass superiorly through the um- bilicus, and inferiorly through the end of the coccyx. The axis of a child's bladder is more vertical than that of the adult ; for in FIG. 128. 1. Ureter. 2. Vas deferens. 3. Vesicula semimli* 4. Trigone. 5. Prostate. POSTERIOR VIEW OF THE BLADDER. children the bladder is not a pelvic viscus. This makes lithotomy in them so much more difficult. 1 When the bladder is completely paralysed it becomes like an inorganic sac, and there seems to be no limit to its distension. Hall found, in a drunkard, the bladder so dilated that it would hold twenty pints of water. (Elem. Phys. art. Vesica.) Frank saw a bladder so distended as to resemble ascites, and evacuated from it twelve pounds of urine. (Oratio de Signis Morbomm, &c. &c. Ticini, 1788.) W. Hunter, in his Anatomy of the Gravid Uterus, has given the representation of a bladder distended nearly as high as the ensiform cartilage. 2 In all animals with a bladder, the younger the animal the more elongated is the bladder. This is indicative of its original derivation from a tube, i.e. the uraclius. In the infant, the bladder is of a pyriform shape, as it is, permanently, in the quadruped ; but as we assume more and more the perpendicular attitude, the weight of the urine gradually makes the lower part more capacious. 534 THE BLADDER. The quantity of urine which the bladder will hold without much inconvenience varies. As a general rule, it may be stated at about a pint. Much depends upon the habits of the individual ; but some persons have, naturally, a very small bladder, and are obliged to empty it more frequently. In young persons the lowest part of the bladder is the neck, or that part which joins the prostate. But as age advances, the bottom of the bladder gradually deepens 7 so as to form a pouch behind the prostate. In old subjects, particularly if the prostate be enlarged, this pouch becomes deep, micturition becomes tedious, and the bladder cannot completely empty its contents. It some- times happens that a stone in the bladder is not felt ; the reason of which may be that the stone, lodged in such a pouch below the level of the neck of the bladder, escapes the detection of the sound. Under these circumstances, if the patient be placed on an inclined plane with the pelvis higher than the shoulders, the stone falls out of the pouch, and is easily struck. The bladder is divided into a summit, a body, a base, and a neck. The summit is its highest part, and to it is attached a thin fibrous cord, the urachus, which passes up to the umbilicus, and is the obliterated remains of a canal connecting the foetal bladder with a sac external to the foetus, called the allantois. The body on its anterior aspect is not covered with peritoneum, and is in relation with the symphysis pubis, the triangular liga- ment, and the obturator internus ; posteriorly, it is covered with peritoneum, and is in relation in the male with the rectum, and in the female with the uterus ; laterally, it is only covered with peri- toneum behind, and is in relation with the obliterated hypogastric arteries, the vasa deferentia, and ureters. The base is the lowest part of the bladder resting upon the middle portion of the rectum, and is only slightly covered behind with peritoneum ; below, it is in contact with the vesiculae seminales and vasa deferentia, which latter pass forwards as far as the prostate ; the reflection of the peritoneum posteriorly with the vasa defe- rentia converging towards the front, forms a triangular space through which the bladder is tapped in cases of retention of urine. URETER AND VAS DEFERENS. 535 The neck is the narrow portion where the urethra begins, and its direction is downwards and forwards. It is embraced by the prostate gland. The ureter l is about seventeen inches long, and conveys the urine from the kidney to the bladder. In the dissection of the abdomen (p. 477), it was seen descending alccg the psoas muscle, behind the spermatic vessels, and crossing the common iliac artery into the pelvis. Tracing it downwards, in the posterior false ligament of the bladder, below the obliterated hypogastric artery, we find that it runs along the side of the bladder, external to the vas deferens, and enters it about an inch and a half behind the prostate, and about two inches from its fellow of the opposite side (fig. 128). It perforates the bladder very obliquely, so that the aperture, being valvular, allows the urine to flow into, but not out of it. The narrowest part of the ureter is at the vesical orifice ; here, therefore, a calculus is more likely to be arrested in its progress than at any other part of the canal. This tube, about twenty-four inches in length, conveys the seminal fluid from the testicle into the prostatic part of the urethra. Taking its origin at the lower part of the globus minor behind the testis, it ascends at the back part of the testis and epididymis, along the back of the spermatic cord through the inguinal canal into the abdomen ; then, leaving the cord at the inner ring, it curves round the deep epigastric artery, then crosses over the external iliac vessels, and descends into the pelvis on the side of the bladder, gradually approaching nearer the middle line. Before it reaches the prostate, it passes be- tween the bladder and the ureter ; then, becoming very sacculated, it runs forwards internal to the vesicula seminalis, and is joined by the duct of this vesicle. The common duct thus formed, ductus communis ejaculatorius, terminates in the lower part of the pro- static portion of the urethra (fig. 128, p. 533). In point of size and hardness, the vas deferens has very much the feel of whipcord, 2 its canal not being more than ^th of an inch in diameter. 1 From ovpfca, I pass urine. * The description in the text assumes the bladder to be distended. But when 536 THE PROSTATE. These are situated, one on either side, between SEMINALES. the base of the bladder and the rectum, and serve as reservoirs for the fluid secreted by the testes, and also secrete themselves a fluid accessory to that of the testicles (fig. 127). Each is a tube, but so convoluted that it is like a little sacculated bladder. When rolled up, the tube is about two and a half inches long, and a quarter of an inch in breadth ; unrolled, it would be more than twice that length, and about the size of a small writing quill. Several caecal prolongation's proceed from the main tube, after the manner of a stag's horn. The vesiculee seminales do not run parallel, but diverge from each other, posteriorly, as far as the reflection of the recto-vesical peritoneal pouch, like the branches of the letter V ; and each lies immediately on the outer side of the vas deferens, into which it opens. The vesiculge seminales contain a brownish-coloured fluid,. presumed to be in some way accessory to the function of gene- ration. 1 PEOSTATE The prostate gland 2 is situated at the neck of GLAND. the bladder, and surrounds the first part of the urethra (fig. 127). In the healthy adult it is about the size and shape of a chestnut. Its apex is directed forwards as far as the deeper layer of the triangular ligament. It is surrounded by a plexus of veins (p. 529), and is maintained in its position by the pelvic fascia (p. 529). Its upper surface is about three-quarters of an inch below the symphysis pubis ; its apex is about one inch and a half from the anus ; the base is about two and a half. Above the prostate are the pubo-prostatic or anterior ligaments of the bladder, with the dorsal vein of the penis between them ; below, and in contact with it, is the rectum ; on each side of it is the levator ani ; in front of it are the membranous part of the urethra (surrounded by its compressor muscle), and the triangular the bladder is empty, the vas deferens runs down upon the side of the pelvis. In this course it may be seen, through the peritoneum, crossing 1, the external iliac vessels ; 2, the remains of the umbilical artery ; 3, the obturator artery and nerve ; 4, the ureter. 1 The vesiculffi seminales are imperfectly developed till the age of puberty. In a child three years of age they can hardly be inflated with the blowpipe. 2 From irpoiffT-qui, to stand before. URETHRA BENEATH THE PUBIC ARCH. 537 ligament; behind, are the neck of the bladder and the vesiculse seminales with the ejaculatoiy ducts. The transverse diameter is about one inch and a half; the vertical is about half an inch less. But the gland varies in size at different periods of life. In the child it is imperfectly developed : it gradually grows towards puberty, and generally increases in size with advancing age. To ascertain the size and condition of the prostate during life, the bladder should be at least half full : the prostate is then pressed down towards the rectum, and readily within reach of the finger. The urethra is a canal about eight inches in ANATOMY OF & THE URETHRA length, and leads from the bladder to the end of IN ITS PASSAGE the penis. It is divided into three portions the prostatic, the membranous, and the spongy. At present only the relations of the membranous part, which comprises that part of the canal between the prostate and the bulb, can be examined. The urethra in this part is the narrowest part of the canal, and measures three-quarters of an inch on its upper surface, and one-half on its lower surface, in conse- quence of the encroachment of the bulb. In its passage under the pubic arch, it is surrounded by the compressor urethree, and below it are Cowper's glands. It traverses the two layers of the triangu- lar ligament, and is about an inch below the symphysis pubis, from which it is separated by the dorsal vessels and nerves of the penis, and by some connective and muscular tissue ; it is nearly the same distance above the rectum ; it is not, however, equidistant from this portion of the intestine at all points, because of the downward bend which the rectum makes towards the anus. 1 The membranous part of the urethra in children is very long, owing to the smallness of the prostate at that period of life ; it is also composed of thin and delicate walls, and lies close to the rectum. In sounding a child, therefore, it is very necessary not to use violence, else the instrument is likely to pass through the coats of the urethra and make a false passage. 1 If a clean vertical section were made, we should see that the two canals form the sides of a triangular space, of which the apex is towards the prostate. This is sometimes called the recto -urethral triangle. 538 LEVATOR ANI AND COCCYGEUS. This muscle supports the anus and lower part of the rectum like a sling ; and, with the coccy- geus and compressor urethras, forms a muscular floor for the cavity of the pelvis. To see the muscle, the pelvic fascia must be reflected from its upper surface. It arises in front, from the posterior aspect of the os pubis near the syinphysis ; behind, from the inner surface of the spine of the ischium ; and,, between these bones, from the ten- dinous line which marks the division , of the pelvic fascia into the obturator and recto-vesical layers (p. 527). From this long origin the fibres descend inwards towards the middle line, and are inserted thus the anterior, the longest, passing under the prostate, meet their fellow in the middle line of the perineum in front of the anus (forming the levator prostatce), joining the fibres of the transversus perinei and the external sphincter at the central tendon of the perineum; the middle, the most numerous, are inserted into the side of the rectum ; the posterior are inserted, partly into the coccyx, and partly into the median raphe between the coccyx and the anus, and meet their fellow beneath the rectum. The levator ani is supplied by the inferior hasmorrhoidal, the two lower sacral, and the coccygeal nerves. The action of the levatores ani is to retract the anus and the rectum after it has been protruded in defagcation by the combined action of the abdominal muscles and the diaphragm. This muscle is placed behind the levator ani, and should be regarded as a continuation of that muscle. It is triangular in shape, and arises by its apex from the spine of the ischium and the lesser sacro-sciatic ligament, gradually spreads out, and is inserted into the side of the lower part of the sacrum and the coccyx. Its posterior fibres are in relation with the pyriformis, its anterior fibres are continuous with the levator ani. This muscle is supplied by the two lower sacral and the coccygeal nerves. At this stage of the dissection, the bladder should be. drawn downwards, and the branches of the internal iliac artery and the sacral plexus clearly displayed on the right side, by carefully clearing away the prolongations of the pelvic fascia which surround them. INTERNAL ILIAC ARTERY. 539 INTERNAL ILIAC ARTERY AND BRANCHES. From the division of the common iliac artery, the internal iliac descends into the pelvis, and, after a course of about an inch and a half, divides, opposite the great sacro-sciatic notch, into two large branches, an anterior and a posterior (fig. 129). The artery lies upon the lumbo- sacral cord, the pyriformis muscle, the external and internal iliac veins ; the ureter, enclosed in the posterior false ligament of the bladder, passing in front : the psoas lies to its outer side at the commencement of its course. FIG. 129. MEU PUD SAC LAT . PLAN OF THE BRANCHES OF THE INTERNAL ILIAC ARTERY. The posterior division gives off the ilio-lumbar, lateral sacral, and gluteal arteries ; the anterior gives off the superior vesical, obturator, inferior vesical, middle hgemorrhoidal, sciatic and pudic ; also the uterine and vaginal in the female. Such is their usual order; but these branches, though constant as to their general distribution, vary as to their origin. The branches of the posterior division are a. The ilio-lumbar is analogous to the lumbar branches of the aorta. It ascends beneath the psoas and the external iliac vessels to get to the superficial surface of the iliacus. Here it divides into an iliac and a lumbar branch ; the iliac branch supplies branches to the iliacus, a branch to the diploe of the ilium, and a large branch along the iliac crest, which finally inosculates with the deep 540 BRANCHES OF THE INTERNAL ILIAC ARTERY. circumflexa ilii, the epigastric, the gluteal, and the external cir- cumflex arteries ; the lumbar branch supplies the psoas and the quadratus lumborum, and anastomoses with the last lumbar artery ; it distributes a small branch to the cauda equina, through the foramen between the last lumbar and first sacral vertebrae. b. The lateral sacral, usually two in number, an upper and a lower, descend in front of the sacral foramina, and inosculate on the coccyx with the middle sacral artery ; the upper enters one of the upper sacral foramina, and, after supplying the structures in the sacral canal, emerges on the back through one of the posterior foramina and supplies the muscles in the neighbourhood, anasto- mosing with the gluteal artery ; the lower descends in front of the pyriformis, supplying branches to this muscle, the bladder, and rectum, and others which enter the anterior sacral foramina for the supply of the cauda equina, and finally emerge through the posterior sacral foramina to end in the muscles and skin of the back : this branch inosculates with the middle and lateral sacral arteries and the gluteal. c. The gluteal is the largest branch. It passes immediately out of the pelvis through the great sciatic notch, above the pyriformis muscle, and then divides into a superficial and deep branch ; the former passes beneath the gluteus maximus ; the latter passes between the gluteus medius and minimus, and then divides into two branches, one running along the upper attached border of the gluteus minimus, the other passing obliquely across the same muscle as far as the great trochanter, to anastomose with the external circumflex artery. These will be dissected with the gluteal region. The anterior division gives off a. The superior vesical artery which comes off from the unoblite- rated portion of the hypogastric, and supplies the upper part of the bladder. It gives off the middle vesical artery, which supplies the base of the bladder and the vesicula seminalis ; a small branch, the deferential, which accompanies the vas deferens to the testis and inosculates with the spermatic artery ; and smaller branches to the ureter. b. The inferior vesical artery which ramifies on the under surface of BRANCHES OF THE INTERNAL ILIAC ARTERY. 541 the bladder, the vesiculae serninales, and the prostate, anastomosing with branches of the corresponding artery of the other side. c. The middle hcemorrhoidal artery which usually arises in con- junction with the preceding, and supplies the rectum, inosculating- with the other hgemorrhoidal arteries. d. The obturator artery which runs along the side of the pelvis, below the corresponding nerve, to the upper part of the obturator foramen, through which it passes to be distributed to the muscles of the thigh. In the pelvis it lies between the peritoneum and the FIG. 130. VIEW OF THE DIFFERENT DIRECTIONS WHICH AN ABNORMAL OBTURATOR ARTEHY MAY TAKE. (SEEN FROM ABOVE.) A. 1. Gimbernat's ligament. 2. Femoral ring. 3. Abnormal obturator artery. 4. External iliac vein. 5. External iliac artery. 6. Diminutive obturator artery arising from its normal source. B. 1. Gimbernat's ligament. 2. Abnormal obturator artery. 3. Femoral ring. 4. External iliac vein. 5. External iliac artery. 6. Diminutive obturator artery. pelvic fascia, and gives off a small branch to the iliacus, which anastomoses with the ilio-lumbar; a vesical branch, which passes backwards to supply the bladder ; and another, the pubic branch, which ramifies on the back of the os pubis, and inosculates with the corresponding branch of the deep epigastric artery and with its fellow of the opposite side. External to the pelvis it divides into an external and internal branch, which respectively skirt the outer and inner margins of the obturator foramen. The obturator artery does not, in all subjects, take the coursa above stated, since, in one case in three and a half, it arises from the 542 BRANCHES OF THE INTERNAL ILIAC ARTERY. deep epigastric, and in one out of seventy-two cases it has its origin by a branch from the obturator joining a branch from the epigastric. It may arise from the external iliac near the crural arch, or by a short trunk in common with the epigastric. 1 Under these circumstances, in order to reach the obturator foramen, it generally descends on the outer side of the femoral ring. Instances, however, occasionally occur, where it makes a sweep round the inner side of the ring ; so that three-fourths of the ring, or, what comes to the same thing, of the neck of a femoral hernia, would in such a case be surrounded by a large artery. 2 e. The sciatic artery is the larger of the two branches into which the anterior trunk divides. It proceeds over the pyriformis and the sacral plexus, to the lower border of the great sciatic notch, through which it passes out of the pelvis between the pyriformis and coccygeus to the buttock, where it runs with the great sciatic nerve between the great trochanter and the ischial tuberosity. It gives off small muscular branches in the pelvis to the pyriformis, coccygeus, and levator ani ; vesical branches to the bladder, prostate, and vesiculae seminales; and hcemorrhoidal branches to the rectum. /. The internal pudic artery supplies the perineum, scrotum and penis. In the pelvis it usually lies above the sciatic, and rests upon the pyriformis and sacral plexus, having the rectum to its inner side. It passes out of the pelvis through the great sciatic foramen, below the pyriformis and above the coccygeus, crosses over the spine of the ischium, and re-enters the pelvis through the lesser foramen. It then ascends on the inner side of the obturator internus towards the pubic arch, where it gives branches to the several parts of the penis. In its passage on the inner side of the 1 In most subjects a small branch of the obturator ascends behind the ramus of the os pubis to inosculate with the epigastric. The variety in which the obturator arises in common with the epigastric is but an unusual development of this branch. The branch derives additional interest from the fact, that after ligature of the external iliac it becomes greatly enlarged, and carries blood directly into the epigastric. See a case in Med. Chir. Trans, vol. xx. 1836. 2 The Museum of St. Bartholomew's Hospital contains two examples of double femoral herniae in the male, with the obturator arising on each side from the epi- gastric. In three out of the four ruptures the obturator runs on the inner side of the mouth of the sac. BRANCHES OF THE INTERNAL ILIAC ARTERY. 543 obturator muscle it is enclosed in a strong tube of fascia, formed by the obturator fascia, and is situated about one inch and a quarter above the tuberosity of the ischium. It now ascends under cover of the ascending ramus of the ischium, where it pierces that part of the pelvic fascia which forms the posterior layer of the triangular ligament, and continues its course close to the ramus of the os pubisj between the two layers of the ligament, the anterior layer of which it pierces, and then divides into the artery of the corpus cavernosum and the dorsal artery of the penis. Throughout its course it is accompanied by the pudic nerve and veins. The branches of the pudic artery were described in the dissection of the perineum (p. 517). The pudic artery, however, sometimes takes a very different course. Instead of passing out of the pelvis, it may run by the side of the prostate gland to its destination ; or, one of the large branches of the pudic may take this unusual course, while the pudic itself is regular, but proportionably small. Anatomists are familiar with these varieties, and a winter session rarely passes without meeting with several examples of them. It need hardly be said that lithotomy, under such conditions, might be followed by a large hemorrhage. The 'middle- sacral artery is a small branch of the abdominal aorta at its point of bifurcation. It descends in front of the body of the fifth lumbar vertebra, the sacrum, and the coccyx. In its course it gives off small branches to the rectum, to the anterior sacral foramina, and it finally inosculates on the sacrum and the coccyx with the lateral sacral arteries. It gradually becomes smaller as it passes down and terminates near the tip of the coccyx in a small body about the size of a pea, called the coccygeal or Lusclika's gland, which has been previously described (p. 486). Respecting the veins in the pelvis, they correspond with the arteries, and empty themselves into the internal iliac vein. The remarkable plexus of veins about the prostate, neck of the bladder, and rectum, has been described (p. 529). NERVES OF Those which proceed from the spinal cord should THE PELVIS. be examined first, afterwards those derived from the sympathetic system. 544 SACRAL PLEXUS OF NERVES. SACRAL Five sacral nerves proceed from the spinal cord NERVES. through the anterior sacral foramina. The upper four, from their large size, at once attract observation ; but the fifth is small : it perforates the coccygeus muscle, supplying it and the skin over the coccyx. SACRAL The anterior divisions of three upper sacral PLEXUS. nerves, and part of the fourth, with the lumbo- sacral cord, form the sacral plexus. The grea^jnerves of this plexus lie on the anterior surface of the pyriformis, covered by the pelvic fascia, which separates it from the branches of the internal iliac vessels and the pelvic viscera. The large cords, diminishing in size from above downwards, converge from the sacral foramina to the great sacro-sciatic foramen, where they coalesce to form a broad flat cord, which passes out of the pelvis beneath the pyri- formis muscle, for the supply of the flexor muscles of the inferior extremity. Before describing the branches of the sacral plexus, it will be best to trace those sacral and coccygeal nerves which do not enter into the formation of the sacral plexus. The lower part of the fourth sacral nerve lies on the coccygeus muscle, and divides into muscular and visceral branches, sending a filament downwards to join the fifth sacral nerve. It distributes branches to the pelvic viscera, and muscular twigs to the levator ani, the coccygeus, and sphincter, the latter of which also furnishes a small cutaneous filament to the skin between the bone and the anus. The fifth sacral nerve emerges between the sacrum and the coccyx, pierces the coccygeus, and lies on its anterior surface. It is joined by a twig from the fourth sacral, and, after running a short distance, pierces the coccygeus again, and is distributed to the skin over the back of the coccyx. It communicates with the coccygeal nerve, and supplies the coccygeus muscle. The coccygeal nerve, not easily found, emerges through the end of the sacral canal, and comes forwards through the coccygeus, be- tween the first and second pieces of the coccyx. It pierces the great sacro-sciatic ligament, and, after receiving the communicating twig from the fifth sacral nerve, it passes backwards to supply SACRAL PLEXUS AND ITS BRANCHES. 545 the integument over the back and side of the coccyx. The com- munications between these three last nerves are sometimes described as the coccygeal plexus. The muscular branches of the sacral plexus are as follows : a. Muscular branches, distributed to the pyriformis, the gemelli, the quadratus femoris, and the obturator internus. The nerve to FIG. 131. LUMBt 12. N. of pyriformis. 13. N. of gemellus superior. 14. N. of gemellus inferior. 15. N. of quadratus femoris. 16. N. of gluteus maximus. 17. Long pudendal n. 18. Cutaneous n. of the but- tock. 19. N. of the long head of the biceps. 20. N. of semi-tendinosus. 21. N. of semi-membrano- sus. 22. N. of short head of the biceps. 1, 2, 3, 4, 5. Sacral nil. 6. Superior gluteal n. 7. Great sciatic n. 8. Lesser sciatic n. 9. Pudicn. 10. N. of obturator internes. 11. N. of levator ani. PLAN OF THE SACRAL PLEXUS AND BEANCHES. the obturator internus is given off from the anterior aspect of the plexus (sometimes from the pudic), leaves the pelvis through the great sciatic foramen with the pudic artery, winds with it round the ischial spine, and re-enters the pelvis with the artery to reach the inner aspect of the obturator internus ; it distributes a small twig to the gemellus superior. The branch to the quadratus femoris is derived from the plexus near the preceding nerve ; it N N 546 SACRAL PLEXUS AND ITS BRANCHES. passes down, beneath the gemelli and obturator internus, to enter the anterior or deep aspect of the quadratus femoris, lying between this muscle and the capsule of the hip-joint : it sends off a small twig to the inferior gemellus, and another to the hip-joint. &. The superior fjluteal nerve proceeds from the lumbo-sacral cord and the first sacral nerve, leaves the pelvis through the great sacro-sciatic foramen with the gluteal artery, above the pyriformis, and there divides into two branches : the upper passes along the iliac attachment of the gluteus minimus, supplying it and the gluteus medius ; the lower accompanies the lower branch of the gluteal artery, and supplies the glutei medius and minimus and the tensor fasciae femoris. c. The pudic nerve runs with the pudic artery, and is contained in the same sheath of the obturator fascia ; it divides into two branches the perineal nerve, and the dorsal nerve of the penis ; the former accompanies the superficial perineal artery, and supplies cutaneous branches and muscular branches to the external sphincter, the accelerator urinse, the transversus perinei, the erector penis, and the compressor urethras ; the dorsal nerve accompanies the last part of the pudic artery, and, after piercing the anterior layer of the triangular ligament and the suspensory ligament, runs along the dorsum of the penis external to the dorsal artery, and is dis- tributed to the glans and the prepuce. d. The small sciatic nerve is formed by the junction of two branches from the sacral plexus, and passes through the great sacro-sciatic foramen below the pyriformis, and then divides into two branches : one, a motor the inferior gluteal supplies the gluteus maximus ; the other, a sensory, supplies cutaneous branches to the back of the thigh and leg, to the skin over the gluteus maximus, and to the perineum and scrotum. These will be dis- sected later on with the lower extremity. e. The great sciatic nerve is the large nerve-cord which passes along the back of the thigh beneath the gluteus maximus and the hamstring muscles, and will be dissected at a later stage. PELVIC SYM- From the lumbar region the sympathetic nerve PATHETIC PLEXUS, descends into the pelvis along the inner side of the anterior sacral foramina. In this part of its course its ganglia THE BLADDER, PROSTATE, URETHRA, AND PENIS. 547 vary in number from four to five. The nerves of opposite sides unite in front of the coccyx, where they form the ganglion impar. The arrangement of the sympathetic nerves in the pelvis is similar to that in the abdomen, each ganglion receiving a branch from the ganglion above and another from the. ganglion below. The external branches communicate with the sacral nerves, one probably going to, and the other coming from, the spinal nerves ; the internal branches pass partly to join the pelvic plexus, and partly to the plexus around the arteria sacra media. The pelvic plexuses are two in number, and are situated one 011 each side of the rectum, being derived from the hypogastric plexus, which passes downwards between the common iliac arteries into the pelvis, reinforced by filaments from the second, third, and fourth sacral nerves and ganglia. The visceral branches are exceedingly delicate, and cannot be traced unless the parts have been previously hardened in spirit. They accompany the arteries supplying the respective organs, and are the inferior hcemorrhoidal plexus to the rectum ; the vesical plexus to the sides and base of the bladder, and secondary plexuses to the vas deferens and vesicula seminalis ; the prostatic plexus to the prostate, the vesicula seminalis, and the cavernous structure of the penis ; and, in the female, the vaginal plexus to the vagina and its erectile tissue, and the uterine plexus to the neck and lower part of the body of the uterus, running between the layers of the broad ligament. It also distributes numerous filaments to the fundus of the uterus and the Fallopian tubes. STEUCTUEE OF THE BLADDEE, PEG STATE, UEETHEA, AND PENIS. It is assumed that the parts have been collectively taken out of the pelvis, and that the partial peritoneal covering of the bladder has been removed. The bladder, in a fairly dilated condition, measures about five inches in length and three in breadth, and when moderately full will contain about a pint of urine. N N 2 548 STRUCTURE OF THE BLADDER. STRUCTURE OF The bladder is composed of a partial peritoneal THE BLADDER. C0 at, a muscular, and a mucous ; between the last two there is a layer of connective tissue, which is called the cellular coat. The serous or peritoneal coat invests the posterior, lateral, and superior surfaces of the bladder : it is absent on the anterior and inferior aspect. The muscular coat is situated beneath the serous, and consists of unstriped muscular fibres, which interlace with each other in all directions. Their general arrangement is as follows : An outer, or longitudinal, layer arises from the pubo-prostatic ligaments, the upper half of the circumference of the prostate and the neck of the bladder, and thence its fibres spread out longitudinally over the summit of the bladder, pass round its posterior aspect and base, to be inserted into the prostate in the male, and the vagina in the female. This layer is especially marked on the anterior and pos- terior surfaces of the bladder. There are also some lateral longi- tudinal fibres which pass backwards from the sides of the prostate and interlace in all directions. Between these is a thin layer of circular fibres, especially developed near the neck and the com- mencement of the urethra, where they form a sphincter sphincter vesicce. Towards the sides of the bladder the two sets of fibres have a less definite arrangement and form a kind of network : these, therefore, are the weakest parts of the bladder, and more liable to the formation of pouches. 1 The development and colour of the muscular fibres depend upon how far the subject has suffered from irritation of the bladder, or any obstruction to the expulsion of the urine. The cellular coat loosely connects the muscular with the mucous coat, and is firmly adherent to the latter. 1 These pouches arise in the following manner : A portion of mucous mem- brane is protruded through one of the muscular interstices, so as to form a little sac. This is small at first, but gradually increases in size, because, having no muscular coat, it has no power of emptying itself ; generally speaking, several such sacs are met with in the same bladder ; and they sometimes contain calculi. If a calculus, originally loose in the bladder, happen to become lodged in a pouch by the side of it, a sudden remission of the symptoms may ensue. This explains our occasional inability to detect its presence at each examination with the sound. BLADDER AND URETHRA. FIG. 132. 549 Prostate gland . . _ Membranous part of the urethra . . . Ureter. Orifice of ureter. Uvula. Caput gallinaginis. Orifice of seminal duct. Cowper's gland. Bulb of urethra. Crus penis. Orifice of the duct of Cowper's gland. One of the lacunae. Corpus cavernosum penis. Glans penis. BLADDER AND URETHRA, LAID OPEN BY AN INCISION ALONG THE UPPER SURFACE. * N N 3 550 STRUCTURE OF THE BLADDER. The bladder must be laid open by an incision along its front, to examine its interior. In a recently contracted bladder, the mucous membrane is disposed in irregular folds, which disappear when the bladder is distended. In a healthy state, it is pale ; when inflamed, it becomes of a bright red. Under the microscope, its surface is seen to be studded with mucous follicles. These follicles secrete the thick ropy mucus in inflammation of the bladder. The mucous coat is loosely connected with the subjacent mus- cular layer, except at the trigone of the bladder, where it is firmly adherent. The epithelium is composed of flattened polyhedral cells of the transitional variety, and beneath these there have been described by Klein a layer of large club-shaped cells arranged at right angles to the surface. When the interior of the bladder is examined, there is seen immediately behind the urethra a triangular smooth surface, the apex being at the urethra. This surface is called the trigonum vesicce, and is paler and smoother than the vesical mucous mem- brane elsewhere ; laterally, it is bounded by ridges extending from the urethra to the orifices of the ureters, the base being between the two ureters. This space corresponds with another one already described, external to the bladder, and which is bounded laterally by the vesiculae seminales, and behind by the reflection of the peritoneum. It is more richly provided with blood-vessels and nerves than the rest of the bladder, and is endowed with more acute sensibility. This is why a stone is more painful when the bladder is empty ; and in the erect, than in the recumbent posi- tion. The vesical orifice of the urethra is situated at the lower and anterior part of the bladder, not at the most dependent part, which forms the pouch behind the orifice, in which urine is apt to accu- mulate in old persons. It appears small and contracted in the fresh bladder, but, if the little finger be introduced into it, it will dilate considerably. Immediately behind the orifice there is, in some bladders, a slight elevation called the uvula. It is composed of a portion of the mucous membrane raised up by an accumulation of the prostatic and submucous tissue, but is rarely of sufficient size ARTEKIES AND NERVES OF THE BLADDER. 551 to interfere with the passage of the urine. This elevation must be distinguished from enlargement of the third or middle lobe of the prostate. The orifices of the ureters are situated about an inch and a half behind the urethra, and about two inches apart. These tubes per- forate the coats of the bladder obliquely, and slant towards each other, standing out in relief under the mucous membrane. 1 A slight ridge proceeds from the orifice of each ureter to the neck of the bladder, looking like a continuation of the ureter itself. If the mucous membrane be removed from these ridges, we find that they are produced by muscular fibres. Sir Charles Bell, 2 who first drew attention to them, believed them to be of use in regulating the orifices of the ureters, and named them the muscles of the ureters. The bladder is supplied with blood by the superior, middle, and inferior vesical arteries. The superior conies from the unobliterated portion of the hypogastric; the middle, from the superior vesical or the internal iliac ; the inferior, from the anterior division of the internal iliac or the pudic. Small branches are also distributed to the bladder by the obturator and sciatic arteries. The veins of the bladder form large plexuses around its neck, sides, and base, and empty themselves into the internal iliac veins. The lymphatics follow the course of the veins. Its nerves are derived from the hypogastric and sacral plexuses ; the former is chiefly distributed to the top, the latter to the neck and the bottom of the bladder. Having already examined the form, size, and PROSTATE relations of the prostate (p. 536), we have now to make out its lobes. There are two lateral lobes presenting on their 1 This slanting of the ureters serves all the uses of a valve. The urine enters the bladder, drop by drop, but cannot return, because the internal coat is pressed against the other side of the orifice, so as to stop it. When the bladder becomes thickened, in consequence of difficulty in passing urine, it sometimes happens that the ureters lose their valvular direction, so that the urine, when the bladder contracts, is partly forced back up the ureters : the result is, that they become dilated, and the pelvis of the kidney also. 2 Med. Chir. Trans, vol. iii. He says : ' These muscles guard the orifices of the ureters by preserving the obliquity of the passage, and pulling down the extremities of the ureters according to the degree of the contraction of the bladder generally.' 552 PROSTATE GLAND. upper and lower surfaces a median longitudinal furrow, the lower groove terminating behind in a deep cleft ; and a third or middle lobe. 1 The middle one is pyriform in shape, unites the lateral lobes, and is situated between them and the urethra. In health, it does not appear like a separate lobe; but when abnormally enlarged, it projects toward the cavity of the bladder, and acts like a bar at the mouth of the urethra. Make a longitudinal incision through the upper surface of the prostate to expose the urethra. This canal runs rather nearer to its upper than its lower surface, and is not of the same calibre throughout. This part of the urethra is about an inch and a quarter long, and about four lines in diameter. It forms a sinus in the interior of the prostate, described by anatomists as the sinus of the prostate, into which the ducts of the prostate open. Along the floor of the sinus is a longitudinal ridge, about three-quarters of an inch in length, broad and elevated behind, but gradually fading in front. This is called the crest of the urethra, and the most prominent part of it is named the veru montanum, or caput gallinaginis, from its supposed resemblance to the head of a wood- cock. On each side of this prominence the common ejaculatory ducts open (p. 549). Immediately in front of the caput gallinaginis, in the middle line, is a small opening which will admit a probe. It leads back- wards into a little cul-de-sac or pouch in the substance of the prostate. This pouch is described as the analogue of the uterus, and called the utriculus or sinus pocularis. It is also called the uterus masculimis. It is of a pyriform shape, running backwards and upwards with the narrowest part at the orifice, and its length is about three lines. It ascends between the lateral lobes of the 1 Attention was first attracted to this middle lobe, in England, by Sir Everard Home, whose account of it is published in the Philos. Trans, for 1806. The pre- paration made by Sir Everard in illustration is preserved in the Museum of the Eoyal College of Surgeons in London, Physiol. Series, No. 2583 A. But the anatomy and effect of the enlargement of this part of the prostate gland is not a discovery of modern times. It was accurately described by Santorini in 1739, and subse- quently by Camper, and is alluded to by Morgagni in the third book of his Epistles. Dr. Messer in the 43rd vol. of the Med. Chir. Trans, has shown that, in subjects over sixty, the middle lobe is enlarged in 20 per cent. PROSTATE GLAND. 553 prostate, and beneath the middle ; its coats are comparatively thick with some muscular tissue enclosed in them, and it is lined with squamous epithelium. The minute orifices of the ducts are seen opening into the floor of the prostatic sinus. The substance of the gland is permeated by the divisions and subdivisions of the ducts. They are not visible to the naked eye, but if traced out with the microscope, they are seen to terminate in blind sacculated extremities, upon which the capillaries ramify in rich profusion. 1 STRUCTURE OF The prostate is surrounded by a firm capsule of THE PROSTATE. fibrous tissue, and is composed of muscular as well as glandular tissue. Nearly two-thirds of it is made up of un- striped muscular fibres, which constitute the stroma of the gland, and have the following arrangement : externally, beneath the cap- sule, they form a thick layer, continuous behind with the external muscular layer of the bladder ; and in front they are arranged in a circular manner round the urethra at its vesical orifice, so as to form in conjunction with the vesical muscular tissue, a sphincter ; the next layer forms a dense interlacing stratum, in the meshes of which is found the glandular tissue ; the deepest layer consists of a thick layer of circular fibres, blending posteriorly with the in- ternal vesical muscular layer, and continuous in front with those of the membranous part of the urethra. The anterior part of the prostate is chiefly muscular ; posteriorly, the glandular elements predominate. The glandular tissue consists of numerous tubular alveoli, which open into elongated excretory ducts lined with columnar epithelium. The alveoli are connected together by connective tissue, associated with fibrous prolongations from the capsule of the gland, and with the muscular tissue. The excretory ducts are from twelve to twenty in number, and open into the prostatic sinus in the floor of the urethra. 2 The prostate is remarkable for its dilatability. 1 This was first demonstrated by the late Mr. Quekett. The same anatomist has also discovered that the secreting cells of the gland contain calculi of micro- scopic minuteness. He finds them, almost without exception, in the prostate at every period of life. For further detail concerning them, consult the article ' Prostate ' in Todd's Cyclopcedia. 2 In the ducts of the prostate we often find small calculi, of a brown colour, 554 VESICUL.E SEMINALES. If a small incision be made through the anterior part of the gland, the base being left entire, the gland may be dilated by the finger sufficiently to allow the extraction of even large calculi. Any change in the dimensions of the prostate affects the canal which runs through it, and more or less obstructs the flow of urine. If the entire gland be uniformly enlarged, the length of the prostatic urethra is increased ; if the enlargement preponderate at one part more than another, then the canal will deviate more or less from its natural track, and assume a more angular or a lateral curve according to the part enlarged. When the middle lobe becomes enlarged, there arises, at the neck of the bladder, a growth which will, in proportion to its size, more or less obstruct the passage of the urine. In the efforts made to introduce a catheter into the bladder, it sometimes happens that the end of the instru- ment is pushed through this hypertrophied lobe. The prostate is supplied with arteries from the internal pudic, the inferior vesical, and the hoemorrhoidal ; its veins form a plexus, the prostatic, around the gland, receiving in front the dorsal vein of the penis, and ending behind in the internal iliac vein: its nerves are derived from the hypogastric plexus, and are inter- spersed with ganglion cells ; the lymphatics pass to the internal iliac glands. VESICUI^E The external appearance of these bodies, each SEMINALES. of which consists of a tube coiled upon itself, has been already described (p. 536). Respecting their structure, we find that they have an external or connective-tissue cottt derived from the recto-vesical fascia ; a middle or muscular, consisting of super- ficial fibres arranged transversely, and of deep fibres arranged longitudinally, and continuous with those of the urethra; and an internal or mucous, which is lined by a scaly epithelium, and pre- sents a honeycombed structure, not unlike that of the gall-bladder. The duct emerges from the anterior part of the vesicula, and joins at an acute angle the vas deferens behind the prostate, to form the common ejaculatory duct (p. 535). Its arteries come from the consisting of phosphate of lime. Cases are sometimes met with in which these calculi by degrees attain a considerable size, and distend the prostate into a sac, which, when examined by the rectum, feels not unlike a bag of marbles. THE URETHRA. 555 inferior vesical and middle hsemorrhoidal ; its veins pass to the internal iliac vein, and its nerves are derived from the hypo- gastric plexus. The function of these bodies is twofold they act as reservoirs for the semen, and secrete a fluid accessory to generation. COWPEB'S The glands of Cowper have been examined in GLANDS. s if u i n ^ ne dissection of the perineum (p. 517). They are placed close to the urethra, one on either side, imme- diately behind the bulb and between the two layers of the tri- angular ligament. They consist of a number of lobules united by firm connective tissue, and their collective size is somewhat larger than a pea. Each pours its secretion by a minute duct, about an inch long, into the bulbous part of the urethra. The use of these glands is analogous to that of the vesiculse seminales and the prostate namely, to pour into the urethra a fluid accessory in some way to generation. They are found in all mammalia, and in some, e.g. the mole, they increase in size periodically with the testicle. The urethra is the canal which extends from the bladder to the end of the penis, and serves not only as the outlet for the urine, but to transmit the secretion of the testicles and the several glands accessory to generation. It varies in length from eight to nine inches, and is divided into three portions, according to the different structures by which it is surrounded in different parts of its course. The first inch and a quarter is surrounded by the prostate gland, and is called the prostatic portion (p. 530) ; the next three-quarters of an inch which passes under the pubic arch, is surrounded by the com- pressor urethrae, and is termed the membranous portion (p. 530) ; the remainder of its course, about six inches in length, is contained in the corpus spongiosum, and is called the spongy portion. The length of the urethra will vary much in different subjects, and according to the condition of the penis. The direction of the urethra, when the penis hangs flaccid, is like the letter S reversed; but if the penis be held straight, the canal forms only one curve through the pubic arch, with the con- cavity upwards. The degree of this curvature varies at different 556 THE URETHRA. periods of life. In the child, the bladder being more an abdominal than a pelvic viscus, the curve forms part of a much smaller circle than in the adult ; but it gradually widens as age increases, and catheters are shaped accordingly. 1 However, the parts, when in a sound state, will yield sufficiently to admit the introduction of a straight instrument into the bladder. A straight staff is some- times used in lithotomy. In its contracted state, the sides of the urethra are in close apposition ; the appearance it presents on a transverse section differs in the different parts of its course. Through the glans it is flattened vertically ; through the prostate it is crescentic, with its convexity upwards, owing to the veru montanum. But throughout the rest of its course the canal exhibits on section the appearance of a transverse slit (fig. 133). FIG. 133. TRANSVERSE SECTIONS OF THE URETHRA. A. Through the prostate. B. Through the corpus spcmgiosum. c. Through the glans penis. The urethra must be laid open from end to end along its roof, to see that the canal is not of uniform calibre throughout. The external orifice is the narrowest and the least dilatable part ; so that the urine may be expelled in a jet. Therefore, any instru- ment which will enter the meatus ought to pass into the bladder, if there be no stricture. The junction of the membranous with the bulbous part is almost as narrow. The prostatic portion of the urethra has been described with the 1 The sharper curve of the urethra in the child was well known to Camper. ' In recenter natis, vesica basi sua elatius sita, pedetentim descendit, unde neces- sario sequitur curvaturam urethras majorem esse in junioribus quam in adultis.' Demon. Anat. Patlwl. lib. ii. p. 13. THE URETHRA. 557 prostate (p. 552) ; the membranous portion with the anatomy of the side view of the pelvic viscera (p. 537). The. spongy portion, so termed because it is surrounded by the erectile tissue of the corpus spongiosum, is about six inches long. That part of it running through the bulb is called the bulbous por- tion, and is the most dilatable part of the urethra except the pro- static. In the centre of the glans penis the canal widens into a sinus termed fossa navicularis ; its termination, at the meatus urinarius, is the most contracted part of the urethra. The most dilatable part of the urethra is the prostatic. Even the narrowest parts of the canal must admit of considerable dila- tation, since calculi of from three to four lines in diameter can pass through it. The common ejaculatory ducts open into the prostatic part of the urethra, by the side of the veru montanum. The ducts of Cowper's glands open into the bulbous part. Besides these glands, a number of ducts open into the urethra, proceeding from small glands situated in the submucous tissue. These ducts, called the glands ofLittre, or lacunae, are large enough to admit a bristle, and run in the same direction as the stream of the urine. Most of them are on the lower surface of the urethra ; but one, called lacuna macjna, is on the upper surface, about one inch and a half down the canal. The urethra is composed of three coats a mucous, muscular, and erectile. The mucous coat is continuous posteriorly with that of the bladder, and it sends down prolongations into the various ducts which open into it. It is arranged in longitudinal folds in the membranous and spongy portions, and is lined by columnar epithe- lium except near the glans, where there are papilla3, covered with squamous epithelium ; this, therefore, is the most sensitive part. Beneath the mucous membrane is a double layer of unstriped muscular tissue, the superficial fibres being arranged longitudinally, the internal fibres circularly. The superficial fibres are continuous with those of the bladder, the external fibres of which surround the spongy portion of the urethra, being placed between it and its fibrous capsule ; the deeper fibres of the bladder pass forwards surrounding the prostatic urethra, and subsequently the spongy 558 THE PENIS. urethra, immediately beneath the mucous membrane. Between the mucous and muscular coats is a layer of areolar tissue, the submucous tissue. The erectile coat, a thin stratum of erectile tissue derived from the corpus spongiosum, extends from this body round the mem- branous and the prostatic portions of the canal. Lastly, the urethra is provided with a closely-set network of lymphatic vessels, which has been demonstrated by quicksilver in- jections. 1 They run from behind, forwards, and join the lymphatics of the glans penis. Eventually, their contents are transmitted down the great trunks on the dorsum penis to the inguinal glands. This explains the pathology of a bubo. The penis is a pendulous organ through which runs the urethra, for three-fourths of its course ; it consists of a root, a body, and the glans penis. The root is the broadest part, and is connected by two crura to the rami of the pubic bones ; its dorsum being supported by a strong elastic suspensory ligament, which is attached to the symphysis pubis. The body is cylindrical, consisting of the two corpora cavernosa and the corpus spongiosum. The glans is the expanded extremity which presents at its apex the orifice of the urethra, and at its base where it is attached to the body there is a deep circular groove, the cervix, the elevated margin in front being called the corona glandis. In these situations are a number of minute sebaceous glands, glandulce Tysonii odoriferce, which secrete a sebaceous substance, called srnegma preputii. The surface of the glans has no sebaceous glands, but is covered with minute vascular papillae, endowed with keen sensibility by the dorsal nerves of the penis. The skin of the penis is remarkably thin and extensible, and connected to the body of the organ by loose areolar tissue, destitute of fat. At the extremity the skin forms the prepuce, or foreskin, for the protection of the glans ; 2 and the thin fold which 1 Panizza, Osscrvazioni antropo-zootom. &c., Pavia, 1830. This anatomist has also displayed by injections an extremely fine network of lymphatics which covers the glans penis. The interstices of this network are smaller than the diameter of the tubes. 2 When the foreskin is, from birth, so tight that the glans cannot be uncovered, such a state is called a congenital phymosis. This condition occasions no incon- THE PENIS. 559 passes from the under surface of the glans to the prepuce is called frcenum preputii. The skin, altered in character, is reflected over the glans, to which it is intimately adherent, and at the orifice of the urethra is continuous with the mucous membrane. The bulk of the penis consists of two parallel cylindrical bodies, of erectile structure, named from the appearance of their interior corpora cavernosa. In a groove along their under surface is lodged a third cylindrical body, the corpus spongiosum, composed of vascular spongy tissue, through which runs the urethra ; an expansion of this at the end of the organ forms the glans. These structures, then the corpora cavernosa and the corpus spongiosum together form the penis ; though the corpus spongiosum appears closely united t'o the corpora cavernosa, yet it is quite distinct from them, as shown in the transverse section (fig. 134). CORPORA The corpora cavernosa, placed side by side, con- AVERNOSA. stitute more than two-thirds of the bulk of the penis. Each commences posteriorly by a gradually tapering portion, called the cms penis, which is attached along a groove in the rami of the ischium and os pubis, where it is embraced by the erector penis (p. 512). The two crura converge, come into appo- sition at the root of the penis, prior to which each presents an enlargement, less in man than in some animals, called the bulb of the corpus cavernosum; they then run together, side by side, to form the body of the organ. Anteriorly, each terminates in a rounded extremity, received into a corresponding depression in the glans, to which it is connected by fibrous tissue. A section through the corpus cavernosum shows that its interior is composed of a delicate reticular structure, surrounded by a white fibrous and elastic coat, from half a line to a line in thickness, and is separated from its fellow by a fibrous septum called the septum pectiniforme. The septum pectiniforme is a median vertical partition between venience in childhood, but is apt, after puberty, to become troublesome and painful, so that it may become necessary to slit up the prepuce and set the glans at liberty. In persons who have a tight foreskin, it sometimes happens that, when the glans has been uncovered, the prepuce cannot be again drawn over it : this is called a paraphymosis. The neck of the glans becomes tightly girt ; great distension and inflammation are the consequences unless the foreskin be reduced. 560 THE PENIS. the two corpora cavernosa ; it is only complete near the root of the penis ; along the rest of the organ there are vertical slits in it, giving it the appearance of a comb : hence its name. Through the intervals in this partition the blood-vessels of the two corpora cavernosa communicate freely with each other. The fibrous investment is thick and strong, and consists of longitudinal bundles of white fibrous tissue, intermingled with yellow elastic fibres. From the interior of the fibrous coat numerous delicate septa, trabeculce, pass into the interior of the corpus cavernosum, intersecting each other in all directions, divid- ing it up into a multitude of small spaces. This trabecular tissue consists of fibrous lamellae with elastic and some non-striated 1. Corpus cavernosum. 2. Corpus spongiosum urethras. 3, Dorsal vein. 4, 4. Dorsal arteries. 5, 5. Dorsal nerves. TRANSVERSE SECTION THROUGH THE PENIS. muscular tissue. The spaces, lined by a layer of flattened epithe- lium cells, similar to that of veins, communicate freely with each other, as may be readily ascertained by blowing air into the penis ; they are smaller, and their component septa thicker at the circum- ference than in the centre of the corpora cavernosa, at the root than towards the glans. Each corpus cavernosum thus consists of innumerable spaces mainly occupied by dilated venous sinuses, from which the blood is conveyed by the dorsal vein, the prostatic plexus, and the pudendal veins. When the penis is flaccid, these spaces are empty ; when it is erect, they are distended with blood. The arteries of the corpora cavernosa come from the branches of the pudic (p. 519), which enter the inner side of each crus, at its bulbous enlargement, and proceed forwards near the septum, distributing numerous ramifications. These are supported in the THE PENIS. 561 middle of the fibrous trabeculas, and end, some in capillaries which convey their blood at once into the intertrabecular spaces ; others in tendril-like prolongations with dilated extremities which project into the spaces, called helicine arteries by Miiller, and which open directly into the cavities of the veins by funnel-shaped orifices. The helicine arteries are absent near the glans, and are best marked at the root of the penis. The peculiar appearance which they present when distended with injection is due to the fact that they are bound down to the trabecular tissue by fibrous bands. The blood from the intertrabecular spaces of the penis returns, partly through veins which pass out on the upper surface of the penis into the dorsal vein (which joins the prostatic plexus), partly through the deep veins which leave the inner side of each crus, and the bulb, to join the internal iliac. CORPUS The corpus spongiosum is the erectile tissue SPONGIOSUM. which surrounds the urethra as it runs along the penis. It commences in the middle of the perineum, anterior to the triangular ligament, in a bulb-like form the bulb and at the end of the penis it expands to form the glans penis. It receives posteriorly an expansion from the triangular ligament, and presents a median groove, marking its development from two lateral halves. The urethra does not pass through the middle of the spongy body, but runs nearer to its upper surface. The bulb hangs more or less pendulous from the urethra, and is surrounded by the accelerator urinse muscle (p. 512). In old persons it extends lower down than in children, and is, consequently, more exposed to injury in lithotomy. The corpus spongiosum has a fibrous coat resembling very much the external fibrous investment of the corpus cavernosum, but it is thinner, whiter, and composed of more elastic tissue. The reticular structure is also finer, and the cavernous meshes smaller, and arranged in a longitudinal direction. Plain muscular fibres sur- round the urethra, and they are also found in considerable amount in the external fibrous coat. Its interior consists of erectile tissue, composed of a plexus of minute tortuous veins, lined by a single layer of flattened endo- o o 562 THE FEMALE PELVIC VISCERA. tlielial cells, and which communicate very freely with each other.. This is easily demonstrated by injecting the dorsal vein of the penis with wax. In this way, we not only fill the spongy body, but also the glans, and the large veins which form the plexus round the corona glaiidis. The veins return the blood ; some by small veins, which emerge from the glans and collect on the dorsal surface to form the dorsal vein ; others pass into the dorsal vein, either through the corpora cavernosa, or by curving round the sides of the corpora cavernosa ; but by far the larger number join the prostatic and the pudic veins,, communicating also with the subcutaneous veins of the penis and the scrotum. The nerves of the penis are the pudic and its superficial perinea! branch. The largest branches run along the dorsum to the surface of the glans ; a few only enter the eTectile tissue of the organ. The pudic nerve and its branch supply the skin and the mucous mem- brane. Some of the filaments distributed to the glans have con- nected with them Pacinian bodies, and some end in simple and compound end-bulbs. The erectile tissue is supplied by numerous filaments proceeding from the Jiypogastric plexus. The lymphatics consist of a superficial and a deep set ; the super- ficial, proceeding from the glans and the integument of the penis, join the inguinal glands. The lymphatics of the glans communicate freely all round it : this explains why a venereal sore on one side sometimes affects the inguinal glands on the other. The deep lymphatics from the corpora cavernosa and the corpus spongiosum pass beneath the pubic arch and join the lymphatics of the pelvis. DISSECTION OF THE FEMALE PELVIC VISCEKA. SIDE VIEW OF After the removal of the left innominate bone, THE FEMALE as described in the dissection for the side view of PELVIC ORGANS. ^Q ma l e pelvic viscera, the vagina, rectum, and bladder should be moderately distended, the two former with tow, the latter with air. This done, the reflections of the peritoneum must be traced, the description of which will be found in the dis- THE URETHRA. 563 section of pelvic viscera from above (fig. 117). After this, clean off the peritoneum, and make out the pelvic fascia and its prolongations. To the description of the fascia already given in the dissection of the male pelvis (p. 528) nothing need be added, except that from the side of the pelvis it is re- flected over the side of the .vagina and the uterus, as well as the bladder. It is this fascia which in great measure supports the uterus in its proper level in the pelvis. When, from any cause, the fascia becomes relaxed, there is a liability to prolapsus uteri. LEVATOR ANI. For the description of this muscle, see p. 538. The female bladder is broader transversely, and, upon the whole, more capacious than the male. The vesical plexus of veins is not so large, and there are no vasa deferentia or prostate gland. The short urethra has a constrictor muscle, as in the male, and is supported in a similar manner by the pelvic fascia. y ENOUS Though the veins round the neck of the bladder PLEXUS ABOUT are comparatively small in the female, attention THE VAGINA. should be directed to the plexus of large veins which surround the vagina. They communicate freely with the veins about the rectum, and empty themselves into the internal iliac. Their congestion in pregnancy sufficiently accounts for the dark colour of the vagina and the external organs, and the frequent occurrence of haemorrhoidal tumours. 1 These veins must be re- moved, with the connective tissue in which they are embedded, before a clear view of the parts can be obtained. The urethra has already been described (p. 523). UEETHEA ... But, in the side view of the parts, we have the opportunity of observing how closely the bladder and urethra are connected to the upper wall of the vagina ; and we can understand how, in cases of protracted delivery, it sometimes happens that the contiguous coats of the bladder and the vagina give way, and that 1 During pregnancy, varicose tumours may form even in the vagina. In the Berlin Med, Zeitung, 1840, No 11, a case is related of a woman who, at the sixth month, bled to death from the bursting of a large vein in the vagina. Other cases of the kind are related by Siebold. o o 2 564 THE VAGINA. a fistulous communication remains between them, through which urine constantly dribbles. It is necessary to slit open the whole of the vagina along the side, to obtain a clear idea of the manner in which it embraces the lower end of the uterus, and of the extent to which the neck of the uterus projects into it. The length of the vagina, in the unimpregnated adult, is, on an average, about four inches on its anterior wall, and between five and six along its posterior wall, owing to its curved direction. It may be more, or less ; the difference in each case depending upon the depth of the pelvis, the stature and age of the individual. The vagina, however, is never so long that we cannot, during life, feel the neck of the uterus projecting at the top of it, higher up, or lower down, according to circumstances. For instance, it is a little lower down in the erect than in the recumbent position ; again, in the early months of utero-gestation, the uterus descends a little into the vagina, so that this canal becomes shorter : the reverse holds good when the uterus begins to rise out of the pelvis. The axis of the vagina is slightly curved with the concavity upwards ; it corresponds with the axis of the outlet of the pelvis. The width of the vagina is not uniform throughout. The narrowest part is at the orifice ; it is also a little constricted round the neck of the uterus. The widest part is about the middle : here a transverse section through it presents the appearance of a broad horizontal fissure. If, therefore, you would insert the bivalve speculum with the least amount of pain, the blades of the speculum should be vertical when introduced into the orifice, and afterwards turned horizontally. STRUCTURE OF The vagina consists of a mucous coat, of a THE VAGINA. muscular coat, and of an external coat of erectile tissue. The mucous membrane is of a pale rose colour, continuous above with that of the uterus, and below with the integument of the labia majora. It is rough and furrowed, especially near the orifice, and it presents two longitudinal ridges columnce rugarum which run, one along the anterior, the other along the posterior wall. From each side of these proceed a series of transverse ridges rugae THE UTERUS. 565 with rough margins directed forwards. They are well-marked in virgins, but repeated parturition and increasing age gradually smooth them down. The use of the vaginal rugge is to excite the sensibility of the glans in coition. They themselves alsd possess keen sensibility, being richly endowed with papillae. The mucous membrane is provided with numerous papillae, conical in shape, and covered with a thick lining of squamous epithelium. In the subrnucous tissue, which is very loose, there is a good deal of mus- cular tissue, with a considerable venous plexus, forming a kind of erectile tissue ; in it, also, are found an abundant supply of muci- parous glands, which increase in size and number towards the uterus. The muscular coat is arranged in two layers, a longitudinal and a circular, between which there may be demonstrated a number of interlacing fibres passing from one to the other layer. The longi- tudinal fibres are continuous with the superficial muscular fibres of the uterus, while the latter are chiefly aggregated at the orifice of the vagina, forming a kind of sphincter muscle, which is continuous with the external sphincter ani. Superiorly, the vagina is inti- mately attached to the neck of the uterus, while to the rectum it is but loosely connected. The erectile tissue found in the connective tissue forms the chief strength of the vagina, being about one-twelfth of an inch in thick- ness. If this coat be minutely injected, we find that it is composed mainly of a plexus of veins surrounded with numerous fasciculi of unstriped muscular fibres. The uterus is the hollow muscular organ which UTEKUS. . . receives the ovum, retains it for nine months to bring it to maturity, and then expels it by virtue of its muscular walls. Its situation and peritoneal connections have been described (p. 503). Its axis slants forwards, so that, upon the whole, the axis of the vagina and uterus describes a curve nearly parallel to the axis of the pelvis. The uterus, then, is so situated that it is ready to rise out of the pelvis into the abdomen after the embryo has attained a certain size. The uterus in the unimpregnated state is pyriform, or rather tri- angular with the angles rounded, and is somewhat flattened antero- posteriorly. It is retained in its position by the broad and round 566 THE UTERUS. ligaments, and measures about three inches in length, two in its broadest part, and one inch thick in its upper part, and weighs from an ounce to an ounce and a half; but there is a variety in this respect, arising from age, the effect of pregnancy, and other causes. For convenience of description the uterus is divided into the fundus, the body, and the cervix. The fundus is applied to the broadest part, which lies above the level of the Fallopian tubes, and is completely invested by peritoneum. The body is the central part, and gradually narrows down to the cervix. Its lateral margins are nearly straight, and give attach- ment, respectively from above downwards, to the Fallopian tube, the round ligament, the ligament of the ovary, and the broad ligament ; its anterior surface is flat, and for full three-fourths of its extent is covered with peritoneum ; its posterior surface is convex, and is entirely invested with peritoneum. The cervix is the lower narrow part which projects into the vagina. The vagina is very closely attached round the neck of the uterus ; observe that it is attached higher up behind than in front. At the free end of the cervix there is a transverse slit, the os uteri, bounded in front by the anterior lip, behind by the posterior lip. Postponing for the present the examination of the interior of the vagina and the uterus, let us pass on to the vessels and nerves of these organs. UTERINE AND The uterus is supplied by the uterine arteries VAGINAL AKTEEIES. derived from the internal iliac, and also by the ovarian arteries ; the vagina by the vaginal arteries from the same source ; and the ovaries by the ovarian arteries (which correspond to the spermatic arteries in the male) given off from the abdominal aorta just below the renal arteries. The uterine artery proceeds from the anterior division of the internal iliac, towards the neck of the uterus, between the layers of the broad ligament, and then ascends tortuously by the side of the uterus, giving off numerous branches to it, which anastomose freely with each other, and with a small branch from the ovarian artery. The fundus of the uterus is mainly supplied with branches from the ovarian arteries. STRUCTURE OF THE UTERUS. 567 The vaginal artery ramifies along the side of the vagina, and distributes branches to the lower part of the bladder and the rectum. The veins, of large size, corresponding with the arteries, form the uterine sinuses and the vaginal plexuses, which empty them- selves into the internal iliac vein. NEKVKS OF THE The nerves of the uterus are derived from the UTEBUS. third and fourth sacral nerves, from the hypogastric and ovarian plexuses (p. 495). They accompany the blood-vessels in the broad ligament to the neck of the uterus, and ascend with them along its sides. Some small filaments continue with the vessels, and form around them plexuses, upon which minute ganglia are found. 1 But most of the nerves soon leave the vessels, and, subdividing, sink into the substance of the uterus, chiefly about its neck and the lower part of its body. A branch may be traced passing up to the fundus of the uterus, and another to the Fallopian tube. The nerves of the uterus enlarge during pregnancy like the arteries. Surgically speaking, the os uteri may be said to have no nerves ; for it is insensible to the cautery and to the knife. The lymphatics of the uterus are small in its unimpregnated state, but greatly increase in size when it is gravid. Those from the fundus and the ovaries proceed with the ovarian vessels to the lumbar glands ; thus explaining the affection of these glands in ovarian diseases. Those from the body and the lower part of the uterus accompany the uterine arteries, and join the glands in the pelvis ; some, however, run with the round ligament to the groin ; hence, in certain conditions of the uterus the inguinal glands may be affected. The uterus, vagina, Fallopian tubes, and the ovaries should now be collectively removed from the pelvis for the purpose of examining their internal structure. The structure of the vagina has been already described (p. 564). STRUCTUKE OF Before the uterus is laid open, examine the THE UTERUS. shape of that portion of the neck which projects into the vagina. The back part of the cervix appears to project 1 Beck, Philosophical Transactions for 1846. 568 STRUCTURE OF THE UTERUS. into the vagina more than the front; but this arises from the vagina being attached higher up posteriorly. If the vagina were cut away from the cervix, the anterior lip of the uterus would appear to project a trifle more than the posterior. For thi& reason, as well as on account of the natural slope forwards of the uterus, the front lip is felt first in an examination per vaginam. 1 The length, however, and the general appearance of the vaginal part of the cervix vary according to the age ; it is also consider- ably altered by parturition. In the adult virgin it is smooth and round, and projects about half an inch; its mouth is a small transverse fissure. But after parturition it loses its plumpness, the lips become flaccid and fissured, and the mouth larger than it was before. 2 The uterus must now be laid open by a longitudinal incision, to examine its interior. In doing so, observe the thickness of its walls, which is greatest towards the fundus. Before coming into the proper cavity in the body of the uterus, slit up a long narrow canal which leads up into it through the neck. This canal, which is about an inch in length, is not of the same dimensions through- out : it is dilated in the middle, and gradually narrows towards each end. The upper end which leads into the body of the uterus,, is called os internum ; the lower end, which leads into the vagina, os externum. The passage is called the canal of the cervix. It O / remains unchanged in pregnancy for some time after the cavity in the body has expanded, but gradually disappears with the increas- ing size of the embryo. The shape of the cavity in the body of the uterus is triangular, 1 This is the only way to reconcile the discrepancies one meets with in anatomical works, respecting the comparative length of the lips of the uterus. Krause, Weber, Busch, and others, say the anterior is the longer ; Mayer, Meckel, Quain, and others, the posterior. 2 Instances are recorded in which the neck of the uterus is preternaturally long. It has been known to project even as much as an inch and a half into the vagina. In such cases it gradually tapers, and terminates in a very narrow mouth. This is said to be one cause of sterility, and it is recommended either to dilate the mouth, or to cut off a portion of the neck. In support of this opinion, it is stated that Dupuytren was once consulted by a lady on account of barrenness : finding the neck of the uterus unusually elongated, he removed a portion of it, and shortly the lady became pregnant. (Hyrtl, Handbuch der top. Anatom.) STRUCTURE OF THE UTERUS. 569 with the apex towards the cervix. In a virgin uterus the cavity is very small, and its sides are convex ; but in a uterus which has borne many children, the cavity has lost the convexity of its sides, and has increased in capacity. Each angle at the base is some- what prolonged, and leads to the minute opening of the Fallopian tube. This prolongation of the angles is noticed more or less in different females, and is the last indication of the two horns of the uterus in some orders of mammalia. The interior of the uterus is smooth at the fundus; but the reverse at the cervix. Here there is a central longitudinal ridge, both in front and behind (as in the vagina) ; from these, other closely set oblique ridges curve off laterally, like the branches of a palm-tree, called arbor vitce uterina. The roughness produced by these ridges occasions an impression as though we were touching cartilage when a sound is introduced into the uterus. The neck of the uterus is provided with small muciparous glands, of which the minute ducts open in the furrows between the ridges referred to. The secretion of these glands is glairy, albuminous, and slightly alkaline. Soon after impregnation, the secretion becomes so firm as to plug the mouth of the uterus, but shortly before and during parturition it is poured out in great quantity, to facilitate the passage of the child. It happens occa- sionally that one or more of the ducts of these glands becomes obstructed, and then dilate into small transparent vesicles, which gradually rise to the surface and burst. 1 The walls of the uterus consist of an outer serous coat derived from the peritoneum, an inner mucous lining, and an intermediate layer of unstriped muscular tissue. The serous coat has been already described. The muscular coat forms the greater part of the thickness of the walls of the uterus, and consists of non-striped or involuntary muscular fibres, chiefly aggregated at the fundus, less so at the junction of the Fallopian tubes. The texture of these fibres is very close, and interwoven together with blood-vessels, nerves, lymphatics, and connective tissue ; so that in the unimpregiiated 1 These were first described by Naboth, and supposed to be true ova : hence their name, ovula Nabothi. (De Sterilitate Mulierum. Lips., 1707.) 570 STRUCTURE OF THE UTERUS. uterus it is almost impossible to trace thein.t In the impregnated condition it is less difficult to trace them, and we can make out that the fibres are arranged in three layers an external, a middle, and an internal. 1 The external layer, placed immediately beneath the peritoneum, is thin, and its fibres, beginning as longitudinal at the cervix, run transversely round the uterus, some of them being continued in an oblique direction over the body into the broad ligaments ; these are continued on to the Fallopian tubes, the round ligaments, and the ligaments of the ovaries. A band of longitudinal fibres passes from the anterior surface of the uterus round the fundus to its posterior aspect, beneath the recto-uterine folds of the peritoneum. The middle layer runs in all directions, having no definite arrangement of its fibres. The internal layer is composed mainly of concentric circles which surround the orifices of the Fallopian tubes ; .at the cervix its fibres are arranged transversely, forming a sphincter. It is this layer which forms the thickest stratum and is closely connected with the mucous membrane ; it is called the muscularis mucosa. Upon the whole, the collective disposition of the muscular layers is such as to exert equal pressure on all sides, when called into action. At the same time that they expel the foetus, the muscular fibres perform another very important function : they close the large venous sinuses consequent upon the great increase in the amount of blood during pregnancy. Therefore, little haemor- rhage accompanies the expulsion of the placenta, provided it have been attached to the fundus or the side of the uterus. But every- one knows the danger of what is called 'placenta prcevia. Here, the placenta, placed entirely or partly over the orifice of the uterus, is attached to a part of the organ which must of necessity expand during labour ; and every uterine contraction increases, instead of checking, the bleeding. For the same reason, paralysis of the muscular fibres in immediate connection with the placenta, be it where it may, is likely to be a source of serious haemorrhage in parturition. 1 In the unimpregnated uterus the muscular fibres are about T j 5 th of an inch in length ; in the gravid uterus they increase to ^th of an inch. FALLOPIAN TUBES. 571 The mucous membrane of the uterus is more delicate and softer than that of the vagina, with which it is continuous, and is closely united to the subjacent tissue. The greater part of it is lined by a columnar ciliated epithelium, but that which lines the lower part of the cervix is squamous, like that of the vagina. Examined with a lens, the mucous membrane lining the body of the uterus is seen to be covered with minute follicles or tubes (uterine glands) arranged at right angles to its surface. These tubes pass outwards in a more or less spiral manner, some of them appearing branched and dilated at their extremities. They become greatly developed shortly after impregnation, and take an impor- tant part in the formation of the membrana decidua. The arrangement of the mucous membrane in the cervix has been already described (p. 569), when the uterus was laid open to expose its cavity. FALLOPIAN The Fallopian tiibes or oviducts are situated, one TUBES. on each side, along the upper free border of, and enclosed by, the broad ligament of the uterus, and convey the ovum FIG. 135. DIAGRAM OF THE UTERUS, ITS BKOAD LIGAMENTS, THE OVABIES AND FALLOPIAN TUBES. (SEEN FROM BEHIND.) 1. Uterus. 2. Ovary, with its ligaments. 3. Fallopian tube. 4. Fimbriated extremity of Fallopian tube. 5. 5. Broad ligament. 6. Vagina. from the ovary to the uterus (fig. 135). They are about four inches in length : one end, the ostium internum, opens by a minute orifice into the upper angle of the cavity of the uterus ; the other 572 THE OVARIES. terminates in a wide, funnel-shaped mouth, the ostium abdominale, surrounded by fringe-like processes called the fimbrice. This ter- mination of the Fallopian tube is called its fimbriated extremity, 1 and its canal opens into the peritoneal cavity, so that thus the cavity of the peritoneum in the female communicates through the uterus and the vagina indirectly with the exterior. The fim- briated extremity extends about an inch beyond the ovary, and, by floating it in water, one or two of the fimbriee may be seen con- nected with the outer end of the ovary. If the Fallopian tube be opened from the dilated end, and a probe introduced into it, you will find that the tube runs very tortuously at first, then straight into the uterus, gradually contracting in size, so that the uterine orifice scarcely admits a bristle. The free end of the tube com- municates with the cavity of the peritoneum. This is the only instance where a mucous membrane is directly continuous with a serous one. It explains how the embryo may escape into the peritoneal cavity ; though this is an extremely rare occurrence. It also explains what is said to have occurred : namely, the escape of the fluid in dropsy through the Fallopian tubes. In a well- injected subject, the Fallopian tubes are seen to be well supplied with blood from the ovarian arteries. The coats of the Fallopian tube are three an external serous coat derived from the perito- neum ; a middle muscular coat, consisting of plain muscular fibres ; an external layer, longitudinal, and an internal layer, circular, both being continuous with those of the uterus ; and an internal mucous coat arranged in longitudinal folds, especially at the ovarian end, and covered with a columnar ciliated epithelium. The ovaries (called by Galen, testes muliebres, being the analogues of the testes in the male) are two oval bodies situated between the two layers of the broad liga- ment of the uterus, in its posterior part. They are connected on their inner side to the uterus by a thin cord, called the ligament of the ovary, and at their outer end they are usually attached to one of the fimbrise of the Fallopian tube by fibrous tissue. The ovaries are of whitish colour, with the long axis transverse, flattened from 1 The fimbriated extremity is sometimes called the morsus diaboli, since it embraces in a peculiar way the ovary during sexual excitement. STRUCTURE OF THE OVARIES. 573 above downwards, and in females who have not often menstruated, their surface is smooth and even ; in after-life, they become puckered and scarred by the repeated escape of the ova. The position of the ovaries is described by Professor His as being nearly vertical, and he states that the Fallopian tube curves round the outer to the lower border of the ovary, so that the fimbriated extremity lies beneath the ovary, with its fimbrise directed upwards ; thus the ova on their escape from the ovary fall into the Fallopian tube. 1 The ovary is about an inch and a half long, three-quarters of an inch wide, and about half an inch thick ; its weight being from one to two drachms. It consists of a dense soft stroma, imbedded in which are numerous small vesicles (Graqfian vesicles'), muscular tissue, blood-vessels and nerves, the organ being invested by a serous covering. The serous layer covers the ovary, but does not present the ordinary features of a peritoneal investment, for the covering is dull and not shining, and the epithelium consists of a single layer of columnar cells which are the remains of the germ epithelium, from which the ova and the other cells in the Graafian vesicles have been originally developed. 2 The stroma composes the substance of the ovary, and consists of some connective tissue associated with a large amount of spindle- shaped cells, resembling in their appearance unstriped muscle-cells. It contains also elastic tissue, and is abundantly supplied with blood-vessels, which are larger at the hilum of the ovary, diminish- ing in size towards its surface. The outer part of the stroma is much condensed, so as to give a white appearance to the organ ; this has been described as a proper fibrous coat, the tunica albuginea ovarii, but which does not actually exist as a separate layer. If a section be made through the ovary, you will find that im- bedded in the stroma are a large number of small transparent vesicles, which are more abundant at the circumference of the ovary, while in the central part there are comparatively few, it being com- posed almost entirely of the stroma. 1 His, ' Lage der Eierstocke,' Archiv f. Aiiai., 1881. 2 Waldeyer, Eierstock u, Ei, Leipzig, 1870; and in Strieker's Hatidbuch, 1871. 574 STRUCTURE OF THE OVARIES. The transparent vesicles just alluded to are the Graafian follicles, or the ovisacs, which contain the ova. 1 In the outer part or cortical layer of the stroma of the ovary may be observed a large number of closely set minute vesicles, about Yo~o^ n f an inch in diameter, more numerous in the ovaries of young children and in some animals. In the central part or medullary portion of the stroma are seen larger and less numerous vesicles, the largest being placed most deeply ; but these, as they become mature, gradually make their way towards the surface, probably by absorption, and when fully developed measure from ^-th to -^th of an inch in diameter. One, or perhaps more than one, Graafian vesicle ruptures at each menstrual period, and the little ovum it contains escapes from the vesicle, and is either grasped by, or falls into the fimbriated end of the Fallopian tube, and is thus conveyed into the uterus. The ruptured vesicle from which the ovum has escaped becomes filled with blood, and subsequently also with an exudation from its walls, so as to constitute a reddish-yellow substance, called the corpus luteum, which persists for a while, and then degenerates into a small stellate fibrous cicatrix. The Graafian vesicles are very numerous, especially in the young subject, the smaller ones being the most numerous, their average diameter being about y^-th of an inch. 2 External to the larger vesicles there can be distinguished a membrana propria or basement membrane; internal to this, the stroma becomes altered so as to constitute a distinct wall to the follicle. Within this, and lining the wall of the vesicle, there is a layer of nucleated cells, called the membrana granulosa, which surrounds a transparent albuminous fluid in which the ovum or germ is contained. The vesicle, as it approaches the surface of the ovary, developes an additional layer of granular cells, called the discus proligerus, within which the ovum is imbedded, lying usually towards the free surface of the ovary. The ramifications of the ovarian artery through the ovary are remarkable for their convolutions ; they run in parallel lines, as in 1 So called after De Graaf, a Dutch anatomist, who discovered them in 1672, and believed they were the true ova. 2 It has been computed that in the ovaries of a child at birth there are no less than 70,000 Graafian follicles. THE LIVER. 575 the testicle. Its nerves are derived from the ovarian plexus, which comes from the renal. The ovarian veins form, like the spermatic veins, near the ovary, the pampiniform plexus, and then terminate, the right in the inferior vena cava, the left in the renal vein. The parovarium, or the organ of jRosenmuller, is the remains of a foetal structure situated in the broad ligament, between the Fallopian tube and the ovary. It consists of a series of convoluted closed tubules, lined with epi- thelium, converging from beneath the Fallopian tube to the ovary. At their ovarian end the tubules are separate, but at their broader end they are joined by a longitudinal tube running parallel to the lower border of the Fallopian tube. It is the vestige of a foetal structure, and is the analogue of the epididymis in the male, and is connected at its uterine end with the remains of the Wolffiaii duct. DISSECTION OF THE ABDOMINAL VISCEEA. The liver is the largest glandular organ in the THE LIVER . . body, and in the adult weighs from fifty to sixty ounces. It serves for the secretion of the bile, and moreover alters some of the constituents of the blood in its passage through the organ. Its diameter in the transverse direction is from ten to twelve inches ; from before backwards it measures from six to seven inches, and its greatest thickness, which is at its back, is about three inches. Its surface is entirely covered with peritoneum, except a small part behind, which is connected to the diaphragm and the upper part of the right kidney by cellular tissue, and again in the hollow which lodges the gall-bladder. The upper surface is smooth and convex in adaptation to the diaphragm, and is marked by a fold of peritoneum running from behind forwards, dividing this surface into two unequal lobes, a right and a left, the right being the larger. The fold of peri- toneum is the suspensory or broad ligament. The under surface is concave and irregular, and is divided into a right and left lobe by the longitudinal fissure. 576 THE LIVE The posterior border is thick and round, having attached to it the coronary ligament. The anterior border is thin and sharp, and presents a notch indicating the division into a right and left lobe ; the notch lodges the round ligament, which is the remains of a foetal structure, the umbilical vein. There is also to the right side of the notch, a slight groove corresponding to the base of the gall-bladder. The right border is thick and round, the left is flat and thin. The under surface is irregular, and is marked by five fissures which map out the five lobes (fig. 136). They are, the longitudinal fissure, the fissure for the ductus venosus, the fissure for the gall-bladder, the fissure for the inferior vena cava, and the transverse fissure. The relative position of these fissures (the liver being in sitii) may be best impressed on the memory by comparing them collectively to the letter H. The transverse fissure represents the cross-bar of the letter ; the longi- tudinal fissure and the fissure for the ductus venosus represent the left bar ; the fissures for the gall-bladder and the vena cava make the right bar. The longitudinal fissure divides the right from the left lobe, and contains the round ligament, which is the remains of the um- bilical vein in the foetus. It is deeper in front than behind, and is not infrequently bridged over by liver tissue, constituting the pons hepatis. The fissure for the ductus venosus is the continuation backwards of the longitudinal fissure to the posterior border of the liver, and contains a fibrous cord, which is the obliterated remains of what was in the foetus the ductus venosus. The fissure for the gall-bladder is a shallow depression to the right of the longitudinal fissure, and lodges the gall-bladder. The fissure for the inferior vena cava runs obliquely backwards and joins at an acute angle the fissure for the ductus venosus at the posterior border of the liver. It begins close to the right extremity of the transverse fissure, and is not uncommonly surrounded by hepatic tissue. The transverse or portal fissure, about two inches in length, unites the other fissures, and transmits the large vessels which enter the LOBES OF THE LIVER. 577 LOBES. liver in the following order : in front is the hepatic duct, behind is the vena portee, and between them the hepatic artery. The lobes of the liver, five in number, are also seen on its under surface. The riglit lobe, much larger than the left, is separated from it by the longitudinal fissure on its under aspect, and by the falciform ligament on its upper surface. Its superior surface is smooth and convex, somewhat quadrilateral in shape ; on the under surface it is marked by three fissures the transverse, and those for the gall-bladder and vena FIG. 136. 1. Longitudinal fis- sure. 2. Continuation of the longitudi- nal fissure (for the ductus ve- nosus). 3. Transverse fis- sure. 4. Gall-bladder. 5. Vena cava in its groove. 6. Right lobe. 7. Left lobe. 8. Lobulus Spigelii. 9. Lobulus cauda- tus. 10. Lobulus quad- ratus. DIAGRAM OF THE UNDER SURFACE OF THE LIVER. cava. It has also on its under surface two shallow fossae : the anterior (impressio colica) is for the hepatic flexure of the colon ; the posterior (impressio renalis) for the right kidney and the supra- renal capsule. The left lobe is the smaller; its upper surface is smooth and convex, its lower is concave and rests on the stomach. The remaining lobes may be considered as forming parts of the right lobe, and are the lobulus Spigelii, the lobulus caudatus, and the lobulus quadratus. The lobulus Spigelii is a prominent quadrilateral lobe, placed between the transverse fissure and the fissures for the ductus p P 578 STRUCTURE OF THE LIVER. venosus and vena cava; behind the transverse fissure it is con- nected to the right by a ridge, the lobulus caudatus. The lobulus caudatus, which passes obliquely forwards and to the right, separating the fissure for the vena cava from the transverse fissure. The lobulus quadratics is a square lobe situated between the gall- bladder, the longitudinal and the transverse fissures. This lobe is occasionally connected to the left lobe by a bridge of hepatic sub- stance arching over the longitudinal fissure, and alluded to before as the pons hepatis. The liver has five ligaments, of which the coronary, the right and left lateral, and the falci- form are reflections of the peritoneum ; the fifth is the round liga- ment, placed in the anterior free border of the falciform ligament in the longitudinal fissure ; it consists of the remains of the umbilical vein of the foetus. The ligaments have been already described (p. 455). The vessels which pass to and from the liver are five also in number : the hepatic artery, the vena portae, the hepatic veins, the hepatic duct, and the lymphatics. The consideration of these is deferred till we have examined the capsule of the liver. The fibrous coat surrounds the liver, and is best seen on those parts of it not covered with peritoneum. This coat is connected on the surface of the gland to the areolar tissue which surrounds the lobules, but does not send down partitions to form a framework for the interior. It is continuous, at the transverse fissure, with the sheath of loose areolar tissue, called Glissoris capsule, which surrounds the vessels as they enter that fissure, and encloses them in a common sheath in their ramifications through the liver. The interlobular connective tissue is exceedingly delicate : hence the great liability of the liver to be lacerated by external violence, and consequent haemorrhage into the peritoneal cavity. The liver consists of an aggregation of small LOBULES. , polyhedral masses, called lobules, about the size or a millet seed, which range from ^th to ^th of an inch (1 to 2 millimetres) in diameter. These lobules are more or less distinctly STRUCTURE OF THE LIVER. 579 marked out by septa of areolar tissue, and in a transverse section have the appearance of mosaic pavement (fig. 137) ; but in a per- pendicular section they somewhat resemble an oak leaf (fig. 138). Each lobule is mapped out by, and separated from, the adjacent lobules by delicate connective tissue, in which runs a plexus of vessels interlolndar plexus consisting of branches of the portal From this plexus passes inwards into the lobule a fine vein. capillary network, whose branches converge to the centre of the lobule and end in a single vein, the intralobular vein, which, in its FIG. 137. . Interlobular vein. 6. Intralobular or cen- tral vein. TRANSVERSE SECTIONS OF THREE LOBULES OF THE LIVER, MAGNIFIED TO SHOW THE PORTAL VENOUS PLEXUS. (After Kiernan.) turn, opens into the sublolular vein, and thence into the hepatic vein. With the interlobular plexus run the biliary ducts. The lobules themselves consist of a minute plexus of blood-vessels, ducts, and cells liepatic cells which latter fill up the spaces between the ramifications of the vessels. It will facilitate the un- derstanding of the different hepatic vessels, if it be borne in mind, (1) that the portal vein, hepatic artery, and hepatic duct ramify together from first to last, enclosed in a common sheath of con- nective tissue, called Glisson's capsule ; (2) that the hepatic veins run alone from first to last, and terminate in the inferior vena cava as it passes under the liver. p p 2 580 STRUCTURE OF THE LIVER. The portal vein enters the transverse fissure of the liver, ac- companied by the entering hepatic artery and the emerging right and left hepatic ducts, which as before stated are surrounded in the liver by a common sheath called Glisson's capsule. In the liver, the portal vein ramifies between the lobules and gives off numerous branches, called interlobular or peripheral veins, which pass between the lobules and communicate freely with each other. These receive the vaginal and capsular veins which convey the blood from the corresponding branches of the hepatic artery. The interlobular plexus of veins gives off a minute capillary network, which penetrates into the interior of the lobule, and converges to- wards the centre of the lobule to' open directly into a single central vein called the intralobular vein. The capillaries which compose this network run in a nearly parallel direction from the circumference to the centre of the lobule, and communicate freely with each other by small transverse branches. The intervals between the branches of the capillary network is very small, varying from y^-g-th to -^-^th of an inch, while the vessels themselves are comparatively large, F ^ . being about ^o^th of an inch in diameter. The intralobular vein re- turns the blood from the centre of the lobule, and opens immediately into a sublobular vein, larger or smaller as the case may be, upon which the lobule is sessile (fig. 138). The sublobular veins, increasing in size, empty themselves into the LONGITUDINAL SECTIONS OF THE n 7 , , i . smaller fiepaUc veins ; these unite to- LOBULES OF THE LIVER. LOBULAB VEINS SEEN JOINING THE form the main hepatic trunks, usually SUBLOBULAK. , , , , , three in number, one each from the- right and left lobes and the lobulus Spigelii. These hepatic veins open into the inferior vena cava, as this vessel passes to the posterior border of the liver. The hepatic artery, entering the transverse fissure of the liver, divides and subdivides with the portal vein and biliary ducts, and ramifies with them between the lobules. The artery distributes branches vaginal branches whilst within the portal canals which STRUCTURE OF THE LIVER. 581 supply the coats of the hepatic vessels and Glisson's capsule ; also capsidar branches to the fibrous coat of the liver which appear on the surface of the liver in stellate plexuses ; and interlobular branches which accompany the corresponding veins and pass into the lobules to join the capillary network which leads to the radicles of the intralobular vein. The interior of each lobule that is, the space left between the several vessels is filled by the hepatic cells. They are of spheroidal or polyhedral shape, with a diameter varying from ^y^-th to -3-5 -0th of an inch, and have no cell-wall. They consist of a granular sub- stance of a light yellow tinge, containing one or more distinct nuclei having a highly refracting nucleolus. In some cases the cells contain fat globules ; when these accumulate in large quanti- ties, they constitute what is called a fatty liver. The office of the hepatic cells is to separate the bile from the blood, and, when filled with bile, to discharge their contents into the biliary ducts. The biliary ducts are the channels through which the bile is conveyed into the hepatic ducts. They commence as minute passages bile canaliculi which are. formed between and around the hepatic cells, and then pass outwards to the circumference of the lobule, where they open into the bile-ducts between the lobules. 1 Here they form a plexus interlobular which opens into ducts which run with the hepatic artery and portal vein in the portal canals ; eventually these join with other ducts to form the right and left hepatic ducts, which leave the transverse fissure of the liver, and, after a course of about an inch, unite to form a single duct, the common hepatic duct. The lymphatics of the liver are arranged in two sets : super- ficial and deep. The superficial may be divided into those on the upper convex surface, and those on the under aspect ; the lymph- atics on the convex surface are : (1) those which run back- wards between the layers of the falciform ligament, and then pass through the diaphragm behind the ensiforin cartilage to enter the 1 The biliary ducts between the lobules are lined with a short columnar epi- thelium, resting on a basement membrane ; but it is doubtful whether the bile- canaliculi are very minute ducts, or whether they are not simple intercellular passages between the hepatic cells. 582 FUNCTIONS OF THE LIVER. anterior mediastinal glands, and thence to the right lymphatic duct ; (2) those which pass forwards over its anterior margin to the under aspect, to enter the glands in the gastro-hepatic omen- turn ; (3) those which run to the right lateral ligament, and then either pierce the diaphragm to join the anterior mediastinal glands, or pass inwards to open into the thoracic duct at its commence- ment ; and (4) those which run to the left lateral ligament, which, after piercing the diaphragm, open into the anterior mediastinal glands. The lymphatics on the under aspect are arranged as follows : (1) those on the right side of the gall-bladder open into the lumbar glands ; (2) those surrounding the gall-bladder accom- pany the hepatic artery to join the glands in the gastro-hepatic omentum ; (3) those on the left side enter the glands on the lesser curve of the stomach and the oesophagus. The deep lymphatics originate partly in the connective tissue between the lobules, and there accompany the hepatic artery and portal vein and duct to the transverse fissure, to join the lymphatic glands on the lesser curve of the stomach and behind the pancreas ; some lymphatics also accompany the branches of the hepatic veins. The nerves of the liver are derived from the pneumogastric, chiefly the left, and from the hepatic plexus which comes from the coeliac plexus. These plexuses enter the liver at the transverse fissure, surround the hepatic artery and the portal vein, and accompany these vessels in their ramifications through it. The ultimate termination of these nerves is not known. The functions of the liver may be thus briefly expressed : 1. It renders the albuminous matter (albuminose), brought to it by the portal vein, capable of being assimilated. 2. It forms a substance, glycoyen, easily converted into sugar, which passes into the hepatic veins, and, being consumed, helps to maintain animal heat. 3. It secretes the bile, which assists in converting the chyme into chyle, and reducing it into a state fit to be absorbed by the lacteals. 4. The bile acts as a natural aperient. 5. The bile is an antiseptic, and probably prevents the decomposition of the food during its passage through the intestine. The gall-bladder, or reservoir for the bile, is GALL-BLADDER. . . , ,. , . 1-1, pyritorm in shape, and is confined in a slight STRUCTURE OF THE GALL-BLADDER. 583 depression on the under surface of the right lobe of the liver (p. 455). It is about four inches long, an inch in its broadest part, and is capable of holding about 1^ oz. of fluid. Its broadest part projects beyond the anterior margin of the liver, and it is maintained in its position by the peritoneum, which usually is con- tinued over it from the liver, but which may occasionally com- pletely invest it, so as to form a kind of mesentery. It is divided into a fundus, a body, and a neck. The fundus is its broadest part, and usually projects a little beyond the front border of the liver ; from this it gradually narrows, forming the body ; and this again still further contracts to form the neck, which makes a bend downwards, curving upon itself like the letter S. The neck ter- minates in a duct called the cystic duct, which, after a course of about an inch, joins the common hepatic duct at an acute angle (fig. 109, p. 467). The common duct thus formed, called the ductus communis choledochus, is about three inches long, and of the size of a crow-quill ; it opens into the inner side of the back of the descending part of the duodenum, after running very obliquely through the coats of the bowel. The gall-bladder consists of two coats, and of a partial peri- toneal covering which only completely surrounds the fundus. The middle coat consists of strong connective tissue, whose fibres interlace in all directions, and in which involuntary muscular fibres can be traced, running mainly in the long axis of the gall-bladder. The mucous coat can only be seen when the gall-bladder has been opened, which should now be done, by laying it open from the fundus to the neck. It is loosely connected to the middle coat, and it is gathered into ridges, which give it a honeycombed appearance, more or less tinged yellowish-brown by the bile. This appearance is most marked in the middle of the gall-bladder, where the surface is covered with polygonal ridges enclosing de- pressions, in which may be seen with a lens numerous openings leading down to mucous follicles. It is covered with columnar epithelium, which secretes an abundance of viscid mucus. At the bend of the neck of the gall-bladder, both its coats project very much into the interior, making the opening considerably narrower than it appears to be outside. In the cystic duct the mucous 584 STRUCTURE OF THE PANCREAS. membrane presents a series of folds, so arranged one after the other as to form a complete spiral valve. The probable use of this is to prevent the too rapid flow of the bile. The gall-bladder appears to serve mainly as a reservoir for the bile while digestion is not going on. The bile becomes during its sojourn in the gall- bladder very viscid and intensely bitter. The gall-bladder is supplied with blood from the cystic branch of the right hepatic artery ; its blood is returned by the cystic vein, which opens into the vena portse ; its nerves are derived from the cceliac plexus, which accompany the hepatic artery. The pancreas is a large gland belonging to the PANCKEAS. . *T . acmo-tubular class. It is placed transversely across the posterior wall of the abdomen, and measures from six to eight inches in length, about an inch and a half in breadth, and from half an inch to an inch in thickness ; its weight being usually from two to three and a half ounces. It presents for examination a head, a body, and a tail. The head, situated to the right side, is turned down, and is embraced by the descending and transverse portions of the duo- denum, the superior and inferior pancreatico-duodenal arteries run- ning between them. A considerable prolongation usually extends upwards from the posterior part of the gland, and reaches the lesser curve of the stomach : this constitutes sometimes a separate mass, and is then termed the lesser pancreas. The tail is the narrow end of the pancreas, which extends to the left as far as the hilum of the spleen. The body is convex in front, and is covered by the ascending layer of the transverse meso-colon. The pancreas has a posterior surface which is concave, and lies on the vena cava, the aorta, the crura of the diaphragm, the superior mesenteric artery and vein, the commencement of the vena portae, and the inferior mesenteric vein ; an upper border which is thick, and is in relation with the splenic artery and vein, the cceliac axis, the hepatic artery, and the first portion of the duodenum ; and a lower border which is thin, and is in relation with the superior mesenteric artery and vein, and on its left with the inferior mesenteric vein. The duct of the pancreas, called also the duct of Wirsung, passes STRUCTURE OF THE PANCREAS. 585 from left to right in the pancreas, nearer its lower than its upper border, and nearer its anterior than its posterior surface. Com- mencing at the tail by the junction of the smaller ducts, it receives, in its course to the right side, repeatedly, other ducts, and thus gradually increases in size until it reaches the head, where it usually receives a large branch from the lesser pancreas ; the large duct then curves downwards, and comes into relation with the common bile duct ; it then passes very obliquely through the coats of the de- scending duodenum on its posterior aspect, and then either opens separately, or in conjunction with the common bile duct, into this portion of the intestine. The structure of the pancreas resembles in most of its characters that of the salivary glands. The alveoli are tubular, frequently convoluted, and are lined by columnar epithelium, which leaves only a narrow lumen, which is often occupied by spindle-shaped cells called the centro-acinar cells. l The ducts are very constricted at their commencement from the alveolus, and are lined by short columnar epithelial cells, which become larger towards the termi- nation of the duct. The arteries of the pancreas are derived from the splenic, the superior and inferior pancreatico-duodenal branches, respectively, of the hepatic and the superior mesenteric arteries. The veins open into the splenic and superior mesenteric veins. The lymphatics end in the lumbar glands ; its nerves are derived from the solar plexus. The uses of the pancreatic fluid are : to convert the starchy matters into dextrine and grape sugar ; to emulsify (in conjunction with the bile) the fatty particles, and, by its alkaline salts, partly saponify the fatty acids, thus enabling them to be taken up by the lacteals ; and, lastly, to convert into peptones the albuminous and gelatinous substances of food. It is an alkaline fluid, very similar to that secreted in the salivary, glands, but contains no sulpho- cyanogen. The spleen is a very vascular sponge-like organ, and belongs to the class of ductless glands. 2 It varies in size according to the amount of blood in it, fluctuating in 1 Langerhans, Beitrage, &c., Berlin, 1869. 2 The other ductless glands are, the thyroid, thymus, and supra-renal capsules. 586 STRUCTURE OF THE SPLEEN. weight, consistently with health, between five and ten ounces. 1 It is of a reddish-blue colour, is more or less elliptical in shape, and, in its natural position, is placed with its long axis nearly vertical. It is about five inches in length, three to four inches in breadth, and from one to one and a half inch in thickness. Its outer surface is smooth and convex, and corresponds to the ninth, tenth, and eleventh ribs on the left side, being in relation with the under aspect of the diaphragm ; its inner surface is concave, and is adapted to the cardiac end of the stomach ; this surface is divided into a larger anterior and a smaller posterior portion by a vertical fissure the lulwn at the bottom of which are large openings, through which the vessels enter and emerge from the spleen. The borders are : an upper, thick and rounded ; a loiver, pointed ; a posterior, rounded ; and an anterior, also rounded, and often notched. As already mentioned, the spleen is connected to the stomach by the y astro-splenic omentum, and to the under aspect of the dia- phragm by the suspensory ligament. The spleen is invested with two coats a serous or peritoneal, and a fibro-elastic. The outer or serous coat entirely covers the organ, except at the hilum, from which it is reflected to the stomach ; it is thin and smooth, and is intimately connected to the subjacent fibrous coat. Itsfilro-elastic coat (tunica propria), thick and strong, not only covers the spleen, but sends inwards throughout its sub- stance fibrous bands (trabeculce), which interlace in all directions, and thus form an intricate network of what are termed trabecular spaces or areolce ; this coat consists of a strong, white, and elastic tissue, and is consequently exceedingly elastic to admit of the vary- ing size of the spleen ; it moreover contains more or less unstriped muscular fibres, so that it contracts faintly on the application of the galvanic current. Besides this, the trabeculse form sheaths and supports for the splenic vessels throughout their ramifications. The areolae, above described, are filled with what is termed the spleen pulp. This pulp is a soft reddish-brown substance, and, under the microscope, is seen to consist of connective-tissue 1 In ague and other forms of fever, it sometimes attains a weight of from 18 to 20 pounds ; it diminishes in weight after forty years of age, and is enlarged during and after digestion. STRUCTURE OF THE SPLEEN. 587 corpuscles, which, with their branched communicating processes, called the sustentacular cells of the pulp, make up a fine reticular tissue ; the interstices of which are filled with red and white blood- corpuscles. Thus the areolae are divided into a large number of smaller spaces by these sustentacular cells, and the white blood- cells contained within them are more numerous than in normal blood, especially in the neighbourhood of the Malpighian corpuscles. The cells have either one or more nuclei according to their size, and present distinct amoeboid movements. In these cells frequently small yellowish granules may be distinguished, which are probably derived from blood-cells, for they present all the characters of hsematin. Blood-corpuscles in all stages, from an unchanged disc to one of complete disintegration, may be seen ; and it has been shown by Klein that some of them present knob-like projections, as if from budding of small nuclei by a process of gemmation. The splenic artery enters the hilum of the spleen by several branches which ramify in its substance, ensheathed and supported by its fibrous framework. 1 The artery is remarkable for its large size, as compared with the organ to which it is distributed, and also for its serpentine course. The smaller branches leave the trabeculge, still invested by a sheath derived from the fibro-elastic coat of the spleen ; but, before they terminate in penicillate tufts, the sheath becomes changed into a thick investment of lymphoid tissue, which surrounds the smallest arterioles. The lymphoid tissue, which forms the sheath of the arterioles, is here and there dilated into oval enlargements, called the Malpighian corpuscles, varying in size from -^th to ^-th of an inch in diameter. These bodies are sometimes thickenings on the side of the arterioles, but more commonly they completely surround the vessels. They are visible in a fresh spleen, and look like white spots scattered through the dark pulp. There do not appear to be any definite boundaries between them and the reticular tissue ; their interior consists of a fine reticulum, denser at the circumference than at the centre, and is filled with lymphoid cells possessing amoeboid movements. The smaller arteries, after branching in all directions, enter the spleen 1 The ramifications of the splenic artery may be seen by washing away the pulp, and floating the flocculent -looking spleen in water. 588 STRUCTURE OF THE SPLEEN. pulp, and their lymphoid walls alter in character, presenting numerous branched processes which communicate with the branched cells of the sustentacular tissue. Through this connection they pour their blood directly into the pulp tissue, and thus into relation with the constituents of the pulp tissue, by which means it is sub- jected to important changes. The veins commence in the pulp tissue in the same way as the arteries, and are at first formed by the arrangement into rows of the connective-tissue corpuscles, which subsequently become spindle-shaped and overlap each other, so constituting a variety of endothelial lining to the venous passages. Assuming more the ordinary character of veins, they travel along the trabeculge like the arteries, but do not accompany them, and freely communicate with each other, and so far are unlike the arteries. The small veins present transverse lines or markings, caused by the encircling elastic fibres around the vessels of the sus- tentacular tissue of the spleen. After entering the trabecular tissue which forms sheaths for the veins, they gradually join and form four to six large veins, which leave the hilum to constitute the splenic vein. The lymphatics of the spleen are arranged in two sets a trabe- cular and a perivascular : the former originate in the trabeculae, and are connected with the lymphatics beneath the capsule ; the latter arise in the lymphoid tissue around the arteries, and subsequently run one on each side of the arteries, anastomosing frequently by transverse branches. The trabecular and peri vascular lymphatics join at the hilum, and run between the layers of the gastro-splenic omentum to the lymphatic glands. The nerves come from the solar plexus and the right pneumo- gastric nerve. The function of the spleen appears to be that of a great blood- gland, and thus concerned in the development of white corpuscles ; for the blood which is conveyed from the spleen contains a large excess of white corpuscles. The large number of red blood-cor- puscles, in various stages of disintegration, also points to another use of the spleen as the gland for the degeneration of red blood- cells into pigment, which is conveyed through the spleen to the liver to be used in the secretion of the bile. It is also presumed STRUCTURE OF THE KIDNEY. 589 that the gland elaborates the albuminous materials of food, and stores them up for a time before they pass into the circulation. The kidneys, two in number, are situated in the lumbar region, behind the peritoneum, imbedded in fat. The left, usually situated higher than the right, is gener- ally longer and somewhat heavier. Their colour is reddish-brown. Each is about four inches in length, two inches and a half in breadth, and one inch and a quarter in thickness. Each weighs about 4|- ounces in the male, and rather less in the female. The kidney presents for examination two surfaces, two borders, and an upper and a lower end. The anterior surface is convex and is covered with peritoneum, and looks somewhat outwards ; the posterior surface is rather flat- tened, and rests on the anterior layer of the lumbar aponeurosis and psoas magnus ; the outer border is convex and rounded ; the inner border presents, about its middle, a deep notch about an inch in length, the hilum, leading to a hollow in the kidney, the sinus, for the entrance and exit of the renal vessels and ureter, the nerves and lymphatics ; these have the following relations to one another : in front lies the renal vein ; behind is the ureter ; between them is the renal artery ; the upper end is large and thick, and looks upwards and inwards, and upon it rests its corresponding supra- renal capsule ; the lower end. smaller and flatter than the upper end, looks downwards and outwards. The kidney is surrounded by a thin fibrous capsule of thick connective tissue, to which it is loosely connected by areolar tissue and minute vessels, except at the hilum ; here it is reflected inwards and becomes continuous with the walls of the renal vessels and ureter. The capsule can be readily stripped oft when healthy, leaving the surface perfectly smooth. 1 A longitudinal section should be made through the kidney, from the outer to the inner border, to demonstrate the interior. This section displays two distinct parts an outer or cortical portion, and an inner or medullary portion. The cortical structure is deeper in colour than the medullary 1 Under the capsule there have been traced unstriped muscular fibres forming an incomplete layer. 590 STRUCTURE OF THE KIDNEY. FIG. 139. portion, and is soft and easily lacerated. It forms the external portion of the kidney to the extent of four to five lines, arching over the bases of the pyramids. It moreover sends down prolonga- tions between the pyramids as far as the sinus, forming the septula renum or the columns of Bertini. The cortical substance consists of convoluted and straight tubes, tubuli uriniferi, of little reddish granules called Malpinliian bodies, and of blood-vessels, nerves, and lymphatics (fig. 139). The medullary structure is composed of numerous conical masses, the pyramids of Malpiglii, having their bases directed to the surface, their sides in relation with the columns of Bertini, and their apices, termed papillm or mammillce, projecting into one of the calices of the ureter. The pyramids, of which there are from eight to sixteen, are surrounded by the cortical substance ; they are composed of minute straight tubules (which proceed from the cortical portion to end in the papillee), of looped tubes described by Henle, and of arteries and veins. 1 At the hilum is the dilated commencement of the ureter, called the pelvis of the kidney. It is funnel-shaped, and its broad part divides into thre.e principal channels, infundibula, an upper, middle, and lower, which again branch, and form from eight to twelve cup- 1 Each pyramid represents what was, in the early stage of the kidney's growth, a distinct and independent lobe. In the human subject the lobes gradually coalesce, and no trace of their primordial state remains, except the pyramidal arrangement of the tubes. But in the kidneys of the lower mammalia, of birds and reptiles, the lobes are permanently separate. SECTION OF THE KIDNEY. 1. Ureter. 2. Pelvis of the kidney. 3. 3, 3. Papilte. STRUCTURE OF THE KIDNEY. 591 like excavations, called calicos. Into each of these calices one, sometimes two or more papillae project. Between the calices the branches of the renal artery ascend to ramify in the kidney, lying imbedded in fat. The pelvis and the calices are composed of three layers an external fibrous layer continuous with the reflected part of the capsule into the sinus ; a middle or muscular, consisting of longitudinal and circular fibres, the former extending nearly as far as the calices, the latter encircling the calyx round the papillas; and an interned or mucous coat reflected over the papillae. STRUCTURE OF With a lens, each papilla may be seen to be THE KIDNEY. studded with minute apertures, which are the termi- nations of the tubuli uriniferi. These apertures open into the bottom of about twenty shallow depressions on a papilla, called foveola;. The orifices are from -j-Jpo th to ^-^th of an inch in diameter. These tubes as they pass out into the pyramidal structure run straight, bifurcate repeatedly at very acute angles, their subdivisions running parallel, and reach the bases and sides of the pyramids, from which they pass into the cortical substanca, greatly increased in number. These, termed the straight or collecting tubes, pass into the cor- tical substance still as straight tubes, the central ones passing nearly to the surface, the outer ones being very short, and only run a short distance into the cortex, so that they are arranged as a series of cones, with their apices to the surface of the organ. These bundles are called the pyramids of Ferrein, or the medullary rays, and receive on each side the curved extremities of the con- voluted tubes. We find the cortical substance is arranged between and around these medullary rays, which, from the intricate arrange- ment of its tubes, receives the name of the labyrinth of the cortex. Each .uriniferous tubule commences in a dilated extremity, termed the Malpighian capsule, in which is enclosed an arterial vascular tuft, the Malpighian tuft, of about p^th of an inch in diameter, and is visible to the naked eye as a minute red point. At the point of union of the tubule with the capsule, it presents a narrow portion, called the neck, beyond which the tubule becomes convoluted for a considerable distance, forming the first or proximal convoluted tube (fig. 140, 2). As it descends towards the medullary ray, the tubule becomes nearly straight, but having a slight spiral tendency : 592 STKUCTURE OF THE KIDNEY. this portion of the tube is termed the spiral tubule (Schachowa). The tubule now enters the medullary portion, narrowing very sud- denly in its calibre, and descends towards the apex of the pyramid, constituting the descending limb of Henle's loop (3). The tubule here bends upon itself, forming a loop, the loop of Henle, and ascends to 1. Malpighian capsule. 2. First or proximal con- voluted tubule. 2 b . Second or distal con- voluted tubule. 3. Descending limb of Henle's loop. (Between 2 and 3 the tube is called the spiral tubule of Schachowa.) 4. Ascending limb of Henle's loop. 5. Irregular tubule. FIG. 140. 6. Collecting tube (Between 2 and 6 the tube is called the curved or junctional tubule.) 6, 7, 8. Different portions of the collecting or straight tube. a. Apex of pyramid. b. Base of pyramid. c. Cortical portion. DIAGRAM OP THE COURSE AND ARRANGEMENT OF THE URI NIFEROUS TUBES. re-enter the cortical substance as the ascending limb of Henle's loop (4), which is larger than the descending limb. On passing out of the medullary ray of the cortical portion, the tubule becomes irregu- larly dilated, and takes the name of the irregular tubule (5) ; this is continued on into another convoluted portion, called the second or distal convoluted tubule (2 b ), which, before entering the straight tube, STRUCTURE OF THE KIDNEY. 593 becomes much narrowed and curved, called the curved or junctional tubule. We have thus traced the straight tubes from their ter- mination at the papillae to their commencement at the pyramids of Ferrein, and have also traced the convoluted tubules from their origin in the Malpighian capsules to their junction with the com- mencement of the straight tubes. The tubuli uriniferi consist of a basement membrane lined with epithelium, which varies in the different parts of the tubuli. The capsule is lined with flattened cells, having oval nuclei ; the neck has cubical epithelium ; the first convoluted tubule is lined with polyhedral epithelium, presenting numerous rod-like processes, resting at one end on the basement membrane, while the other extends towards the lumen of the tubule, 1 and thus presents the appearance of striation ; the spiral tubule of Schachoiva has similar epithelium ; the descending limb is lined with flattened epithelium, like that in the capsule ; the ascending limb presents epithelium similar to that found in the first convoluted and spiral portion of the tubule, although smaller and with shorter rod-like processes ; the irregular tubule is furnished with the rod-like cells of unequal length, which, however, render the lumen more uniform ; the second convoluted tubule has epithelium somewhat like that of the first convoluted tubule, but having long cells with large nuclei, and possessing high refractive properties ; the curved or junctional tiibide has a large lumen, and is lined by angular or fusiform cells with short processes ; the collecting or straight tubes are lined with cubical epithelium, which in the larger tubes becomes distinctly columnar. The renal artery enters the hilum between the pelvis and the renal vein. It shortly divides into four or five branches, which pass outwards between the papillae, and then enter the cortical portion between the pyramids. From these there pass to each Malpighian pyramid two branches, which ascend along its sides as far as its base, distributing in their course small vessels which pass to the Malpighian capsules. At the base of the pyramid they form arches, and make a bend from which two sets of branches are given off, the iuterlobular arteries and the arteriolas rectae. 1 Heidenhain, Archiv /. mikr. Anatom. x., 1873. Q Q 594 STRUCTUKE OF THE KIDNEY. a. Artery. v. Vein, or efferent vessel. c. Capsule. d. Urinary tube. The interlobular arteries pass off at right angles between the medullary rays, and then run amongst the convoluted tubes, some to enter the Malpighian capsules, and others to reach the surface and supply the capsule, ending in the stellate veins beneath the capsule. The arteriole which passes to the Malpighian capsule is termed the afferent vessel, and, entering the dilated extremity of the uriniferous tube, breaks up into a number of convoluted capillary ves- sels, constituting the glomerulus of Malpighi. The blood is returned from the glomerulus by a small efferent vein, which emerges from the capsule close to the entrance of the artery. This vein, after a short course, breaks up, like an artery, into a dense network of capillaries, which ramify over the convoluted tubules. Some of the veins from the lower glomeruli break up into straight vessels, and then pass from the medullary rays into the pyramid (fig. 141). The arteriolce rectce are destined for the supply of the Malpi- ghian pyramids, entering them at their bases, and then pass down- wards to their apices, where they join the venous plexuses. The Malpighian bodies are small red granular masses about i^o-th of an inch in diameter, and are only found in the cortical substance. Each is composed of the dilated commencement of a uriniferous tube forming the Malpighian capsule, containing within it a coil of small blood-vessels called the Malpighian tuft or glomer- ulus. The capsule is composed of a homogeneous membrane, and is pierced by a small artery, afferent vessel, which enters it oppo- site the commencement of the urinary tubule. In the capsule the artery breaks up into a coil of minute blood-vessels, glomerulus, and returns its blood by a vein, efferent vessel, which emerges from the capsule close to where the artery entered (fig. 141). The capillary plexus within the capsule is surrounded by the epithe- lium lining the interior of the capsule. 1 1 Histologists differ with respect to the disposition of the epithelium over the glomerulus : some assert that it has no epithelial covering, but that it hangs loose STKUCTURE OF THE SUPRA-RENAL CAPSULES. 595 The renal veins return, the blood from three sources : from the veins situated beneath the capsule and those corresponding to the interlobular arteries which pass between the medullary rays, and at the bases of the Malpighian pyramids join the venae rectae ; the venae rectae return the blood from the arteriola3 rectae, and begin in plexuses at the apices of the pyramids, they then pass outwards between the tubuli recti, and join the interlobular veins to form the proper renal veins; these pass down along the sides of the Malpighian pyramids, accompanied by their corresponding arteries, and in their course to the sinus receive the efferent veins from the adjacent cortical substance. At the sinus they communicate freely with each other and join to form the renal vein. The nerves, about fifteen in number, forming the renal plexus, are derived from the lesser and smallest splanchnic nerves, the solar plexus, and the semilunar ganglion. The lymphatics, consisting of a deep and a superficial set, pass to the lumbar glands. SUPRA-RENAL These bodies, situated at the top of the kidneys, CAPSULES. belong to the class of ductless glands. They are of yellow-ochre colour: the right is triangular, and resembles a cocked hat ; the left is more almond-shaped and rather the larger of the two. They measure about an inch and a half in their long diameter, about three-quarters in breadth, and two or three lines in thickness; they weigh from one to two drachms. The gland is surrounded by connective tissue and fat, and is invested by a thin fibrous covering, which sends down partitions into the interior through furrows on their surface. A perpendicular section shows that it consists of a firm exterior or cortical part, and of an interior or medullary substance, soft and pulpy. The cortical portion is of a yellow colour and forms the principal part of the organ. It consists of parallel columns arranged per- pendicularly to the surface, due to the capsule sending processes within the capsule ; some, that the tuft is completely invested with epithelium, except where the afferent and efferent vessels pass in ; others, again, that only that portion of the glomerulus which looks towards the neck of the tubule is covered with epithelium. Q Q 2 596 STRUCTURE OF THE SUPRA-RENAL CAPSULES. into the interior of the gland, which communicate at frequent intervals by transverse bands. There are thus formed numerous spaces which communicate with each other ; the spaces at the surface are smaller, while 'those towards the centre are longer ; the section through the cortex gives the appearance of a fine network, the external portion taking the name of the zona glomemdosa, the internal portion that of the zona reticularis, the intermediate portion that of the zona fasciculata. The reticular tissue is made up of fibrous tissue with longitudinal bundles of unstriped muscular tissue. The interspaces are occupied by granular, polyhedral cells, from a ^ O th to yi^Vo^ f an inch, which do not fill the spaces, so that between them and the walls of the spaces there are intervals, believed to be spaces which communicate with the lymphatics in the trabecular tissue. The medullary portion varies in colour according to the amount of blood contained in it, being sometimes of a dark-brown colour, sometimes nearly. white. Not infrequently the medullary part is converted into a cavity, but this is probably a post-mortem change. It consists of a plexus of minute veins, supported by the delicate areolar tissue containing muscular fibres, and presents a reticular aspect. Among these are numerous granular and branched cells. 1 The arteries to the gland are conveyed along the trabecular tissue, and, after supplying the gland-tissue, converge to the centre, where the blood is returned into the venous plexuses in the medullary portion. They are derived from the abdominal aorta,, the phrenic and the renal arteries. The vein begins in the centre as a single vessel, and joins, on the right side, the inferior vena cava, and on the left side the left renal vein. The lymphatics terminate in the lumbar glands. The nerves are derived from the solar and renal plexuses, and in them are found numerous ganglia. They are distributed chiefly to the medullary portion. 2 Of late years the minute structure and functions of the supra-renal capsules have been much investigated, 1 The medullary cells are stained a deep brown colour on the addition of bichromate ofjpotash, the cortical cells being scarcely affected by it. 2 Luschka states that the branched granular cells of the medullary portion are connected with the nerve-fibres. THE STOMACH. 597 in consequence of the discovery, made by Dr. Addison, of the close relation which exists between certain diseases in these bodies and a brown discoloration of the skin. Their precise function is still unknown. STOMACH AND The alimentary canal is composed of four coats : INTESTINES. a serous, a muscular, a submucous, and a mucous. First, is the serous or peritoneal coat, described at p. 459. Secondly, under the serous is a muscular coat, upon which the chief strength of the canal depends. It consists of two distinct strata of plain muscular fibres ; the outer stratum is longitudinal, the inner cir- cular. This arrangement not only makes the bowel stronger, but regulates its peristaltic action, for the longitudinal fibres, by their contraction, tend to shorten and straighten the tube, while the circular fibres contract upon and propel its contents to greater advantage. Connecting this coat and the mucous, is a layer of areolar tissue called the submucous coat, in which the arteries break up before entering the mucous membrane. The mucous is the most complicated of all the coats, for it presents different characters in different parts, according to the functions which it has to perform. The stomach should be moderately distended STOMACH. ... , . , . -..-, ' , . to see its size, which varies in different subjects according to the habits of the individual. When distended, an average stomach would be about ten or twelve inches in length, and four in depth and width ; its weight is stated to be about four and a half ounces. It is conical in shape ; the left part forms a large bulge called the cardiac or splenic end ; and on the right side where the food passes out, it becomes small and contracted, and is called the pyloric end. The stomach presents for examination two surfaces, two borders, two ends, and two orifices. The anterior surface is convex, and looks upwards and forwards; the posterior surface looks downwards and backwards. The upper border or the lesser curvature is concave and short, and extends from the oesophagus to the pylorus ; it is connected to the liver by the gastro-hepatic omentum. The lower border or the greater curvature is convex, and affords attachment to the great omentum. 598 STRUCTURE OF THE STOMACH. The left end is the larger, and is called the cardiac or splenic end ; it bulges out to the extent of two or three inches to the left of the entrance of the oesophagus, and is called the great cul-de-sac or fundus. The right end is narrow, and makes a double bend: near the first it bulges into a pouch, called the antrum pylori, or the small cul-de-sac. The cesophageal or cardiac orifice^ situated at the highest part of the stomach, is on the left, and receives the O3sophagus ; the pyloric orifice is continued on into the duodenum, and is narrow, being guarded by a musculo-mucous ring, the pylorus. 1 The stomach is connected at its borders by peritoneal folds extending to neighbouring structures : thus, its lesser curve is con- nected with the transverse fissure of the liver by the gastro-hepatic or lesser omentum ; its cardiac end is connected with the hilum of the spleen by the gastro-splenic omentum ; to the left of the O3sophagus it is connected with the diaphragm by the gastro-phrenic ligament ; to its greater curve is attached the great omentum, which is continuous on the left side with the gastro-splenic omentum. The pylorus is the narrow circular ring, composed of circular muscular fibres and mucous membrane, through which the food passes into the duodenum. The serous and longitudinal muscular fibres take no part in its formation, being continued over it on to the duodenum. The stomach consists of four coats : serous, muscular, submucous and mucous. The serous or peritoneal coat covers the surface of the stomach, except at the borders where the peritoneum is continued as omenta to other organs ; it is along these borders that the vessels run. The muscular coat can be seen when the serous coat is removed > The fibres are of the unstriped variety, and arranged in three layers : an external or longitudinal, a middle or circular, and an internal or oblique. 1 The position of the stomach within the abdomen and its relations with sur- rounding structures are matters of much dispute. Dr. Lesshaft has come to the conclusion that the stomach is nearly vertical, so that its fundus touches the diaphragm. (See Lancet, March 11, 1882, p. 406.) His, and most anatomists, are of opinion that the long axis is placed obliquely from left to right within the, abdomen. STRUCTURE OF THE STOMACH. 599 The longitudinal fibres are continuous with the longitudinal fibres of the oesophagus, and spread out over the stomach, being most numerous along the curvatures of the stomach : they are at the pyloric end continuous with the longitudinal fibres of the duodenum. The circular filrres are well-marked about the middle of the stomach, but are most abundant at the pylorus, where they form a powerful sphincter. The oblique fibres are scattered over the sides of the stomach, and are most distinct at the entrance of the oesophagus, crossing obliquely from left to right and from right to left. They are con- tinuous with the well-marked circular fibres of the oesophagus. The submucous coat serves to connect the muscular with the mucous coats. It consists of areolar tissue, and permits the muscular and mucous coats to move freely on each other, and allows the blood-vessels to ramify minutely before they enter the mucous membrane. When the stomach is laid open from the cesophageal to the pyloric orifice, the mucous membrane is seen to be thick, of pale pink or straw colour, and is gathered into longitudinal folds rugce which disappear when the stomach is distended. If a portion of the mucous membrane be examined under the microscope, its surface will be seen to be mapped out into small hexagonal pits or alveoli, surrounded by ridges, giving it a honey- combed appearance. The pits vary from j-J-^th to ^-Q-th of an inch in diameter. At the bottom of them are a number of minute apertures, the orifices of the gastric follicles. In a perpendicular section, the follicles are arranged in parallel lines at right angles to the surface, and terminate in blind sacculated ends set in the submucous tissue. The entire thickness of the mucous membrane is made up of these tubular glands. The follicles consist of two kinds, mucous and peptic glands. Tubular in shape, they have a basement membrane lined with epithelium, and average about -^th of an inch long, and -j-Jpoth of an inch in diameter. The mucous glands are found over the whole surface, but are most numerous at the pyloric end of the stomach. They are composed of tubes, each consisting of two or three short tubules, opening into a common 600 STRUCTURE OF THE STOMACH. duct, which itself opens into the bottom of an alveolus. They are lined with columnar epithelium continuous with that lining the mucous membrane. The peptic glands are also found over the entire surface of the mucous membrane, and consist of tubules with branched csecal extremities opening into a common duct, which is, however, shorter than that of a mucous gland. They are lined with columnar epithelial cells, called the central cells, and are supposed to be concerned in the secretion of the gastric juice; these cells become, at the neck of the gland, much shorter and more granular. The lumen of the gland is very small, but is somewhat larger at the free and the cascal ends than in the middle. Towards the lower part or fundus of the gland there are found spheroidal and granular cells between the epithelium and the basement membrane, called parietal cells. In the stomachs of young children there is a large amount of lymphoid tissue found between the gastric glands. It is aggre- gated into small masses in the mucous membrane, and resembles in many respects the solitary glands of the intestine, although not so well defined. The mucous membrane of the stomach is lined by columnar epithelium, which also extends into the glands. A thin layer of unstriped muscular tissue (musctflaris mucosee) is found between the mucous membrane and its submucous tissue, varying in amount and in the number of its layers. The glands of the stomach are richly supplied with blood, which is derived from the gastric, the vasa brevia, the right and left gastro- epiploica, and the pyloric arteries. The arteries form a stratum of minute inosculations in the submucous tissue, in which the closed ends of the tubes are set ; from this stratum, the capillary plexuses run up between the tubes to the surface of the stomach, where they again form a larger capillary plexus and form the hexagonal spaces before alluded to. The veins, corresponding to the pyloric and gastric arteries, end in the vena portse ; those corresponding with the vasa brevia and the epiploic arteries open into the splenic vein. The lymphatics enter the glands along the lesser and greater curvatures of the stomach, and may be divided into a superficial and a deep set. STRUCTURE OF THE SMALL INTESTINE. 601 The nerves are derived from the pneumogastrie nerves and from the solar plexus. SMALL The small intestine, consisting of the duodenum, INTESTINE. jejunum, and ileum, forms a tube averaging twenty feet in length, which gradually lessens in calibre until it opens into the caecum. The duodenum is about twelve fingers' breadth in length (whence its name) ; the jejunum l comprises two-fifths, the ileum 2 three-fifths, of the remaining part of the small intestine. As regards their external characters, the duodenum and jejunum are more vascular than the ileum, and feel thicker in consequence of the peculiar arrangement of their mucous membrane ; but there are no defined limits between the different portions of the intestinal canal. Its coats are four in number : serous, muscular, submucous, and mucous. The serous coat consists of peritoneum, and forms a complete investment, except in the case of the descending and transverse portions of the duodenum, which are only covered in front. The muscular coat consists of an outer longitudinal layer and an inner circular thicker layer, which, however, becomes thinner towards the end of the ileum. The submucous coat connects the muscular and mucous coats ; immediately beneath the mucous membrane there is a very thin layer of non-striped muscular fibres, termed muscularis mucosce. The mucous coat can only be seen when the intestine is cut open from the upper end, and is composed of the following strata : the muscularis mucosae, a layer of retiform tissue with lymph corpuscles, with blood-vessels and nerves ; and, lastly, a layer of columnar epithelium. When the intestine is laid open we see that the mucous mem- brane is arranged in close transverse folds, called valvulce conni- ventes or valves of Kerkring. These differ from other folds in the alimentary canal e.g. in the oesophagus and stomach in that they are not obliterated when the tube is distended. Each fold extends about one-half or two-thirds round the intestine, but they are not all of equal size, and are about one-third of an inch in depth. They 1 Ftoaijejunus, empty. 2 From tfattv, to roll or twist. 602 STRUCTURE OF THE SMALL INTESTINE. commence immediately below the opening of the biliary and pan- creatic ducts, and are most developed in the duodenum and the upper part of the jejunum. Below this part of the tube they gradually decrease in size, and become wider apart, till they finally disappear near the middle of the ileum. The use of the valvulas conniventes is to increase the extent of surface for the absorption of chyle; to prevent the food passing too rapidly through the intestine, and for secretion. If a portion of small intestine be washed and placed in water, the surface of the mucous membrane appears like the soft fur or pile upon velvet. This appearance is produced by small processes called" villi. These are extremely vascular projections of the mucous membrane, about a fourth of a line in length, and are so numerous that a square line contains from forty to ninety of them. 1 Their size, however, and their number, bear a direct ratio to those of the valvulse conniventes. Under the microscope a villus is seen to consist of an outstanding process of the mucous mem- brane, covered by a layer of columnar epithelium, which rests upon a basement membrane. Each villus is furnished with an artery which forms a network of inosculations in it, and then returns its blood by a single vein. Down its middle runs a lacteal or absorb- ing vessel, which commences in a closed end near the summit of the villus, where it is surrounded by a layer of pale non-striped muscular fibres proceeding from the muscularis mucosee. This is surrounded by a plexus of capillaries, external to which is the basement membrane supporting columnar epithelium. Forming the matrix of the villus is a fine network enclosing large flattened cells with oval nuclei and lymph cells. INTESTINAL There are four kinds of glands 2 in the small in- GLANDS. testine, called the glands of Lieberkiihn, Brunner, Peyer, and the solitary glands. The first and last are distributed over the whole tract of the intestinal mucous membrane ; the other two over particular parts. 1 Krause estimates the total number of villi at four millions. '' A satisfactory examination of the intestinal glands can be made only in specimens quite recent, taken from young persons who have died suddenly, or from a rapidly fatal disease. STRUCTURE OF THE SMALL INTESTINE. 603 The simple follicles or crypts of Lieberlcuhn, 1 the most numerous of all, are minute tubes with blind ends, very thickly distributed over the small and the large intestines. Under the microscope, their orifices are seen between the villi, like so many minute dots. They vary in depth from -J^-th to ^th of a line, and about ^kh of a line in diameter ; their walls consist of a delicate basement or endothelial membrane, and are lined with columnar epithelium. The duodenal or glands of Brunner 2 are found only in the duo- denum and a small part of the beginning of the jejunum. They are just visible to the naked eye, and may be seen by removing the muscular coat. Their structure exactly resembles the round compound glands of the mucous membrane of the mouth. The glands of Peyer 3 (glandulce agminatce) abound most in the ileum, and are seen most distinctly in children. They are arranged in groups, from twenty to forty in number, on that part of the in- testine most distant from the attachment of the mesentery. These groups are from half an inch to three inches long, of an oval form, and increase in size and number towards the lower part of the ileum. If a group be examined by dissecting away the muscular coat, you find that it is composed of a number of small oval vesicles, like Florence flasks, imbedded in the submucous tissue. They are composed of masses of lymphoid tissue, of about three-fourths of a line in diameter, and contain an opaque greyish fluid. No excretory ducts have been traced from these vesicles, but they are supposed to discharge their contents by rupture of their capsules. Between the vesicles are found Lieberkiihn's follicles ; and the sur- face of the patches is covered with villi. These glands are liable to be ulcerated in typhoid fever. They diminish in number and size with old age. The solitary glands are scattered over all parts of the small and large intestines. They consist of the same lymphoid structure as- the glands of Peyer, and only differ from them in being solitary instead of being aggregated into groups. 1 J. N. Lieberkiihn, Diss. de Fabric, et Actione Villorum Intestin. ten., 1782. 2 J. C. Brunner, Gland. Duoden. sen Pancreas Secundarium, 1715. 3 Peyer, De Glandulis Intestinorum, 1682. These glands were first described by Neheniiah Grew, in 1681. 604 STRUCTURE OF THE LARGE INTESTINE. The lymphatics consist of two sets those of the muscular, and those of the mucous coats ; the latter receive those from the villi, at the base of which they form a minute plexus, and, after piercing the muscular coat, join with the former, which are chiefly found between the longitudinal and the circular layers of muscular fibres. The nerves are derived from the superior mesenteric plexus, and accompany the superior mesenteric artery and its branches, between the layers of the mesentery; after reaching the intestinal walls the nerve-filaments separate from the arteries. They then pierce the external longitudinal muscular fibres, and form a very minute gangliated plexus Auerliaclis plexus or plexus mesentericus which distributes filaments to the muscular layer of the entire intestinal canal. From this plexus numerous branches perforate the internal circular muscular layer, and unite to form a largely gangliated plexus Meissner's plexus in the submucous tissue. The inter- muscular plexus probably supplies the muscular coat and regulates the peristaltic action of the bowel ; the submucous plexus determines the calibre of the blood-vessels. LARGE The principal external characters of the large INTESTINE. intestine are that it is pouched or sacculated, and that it has attached to it little pendulous portions of fat covered by peritoneum, called appendices epiploicce. The pouches (sacculi) are produced by a shortening of the longitudinal muscular fibres, and by their being collected into three bands, about half an inch wide, nearly equidistant from each other. One of these bands corre- sponds with the attached part of the circumference of the bowel ; another with the front part ; a third with its concavity. If at any given part the three bands be divided, the pouches immediately disappear. In a colon moderately distended and dried, we observe that the mucous membrane forms numerous ridges or incomplete septa (see fig. 142) : they correspond to the grooves on the external surface of the bowel, and disappear, like the sacculi, when the longitudinal bands are divided. The rectum differs from the rest of the large intestine in that its longitudinal muscular fibres are not collected into bands, but distributed equally over its whole circumference. Moreover, both the longitudinal and circular fibres are of considerable strength, like STRUCTURE OF THE LARGE INTESTINE. 605 those of the oesophagus, as one might expect from the particular functions which these parts of the alimentary canal have to perform. For an inch and a half, or thereabouts, above the anus, the circular fibres are remarkably developed, and constitute the internal sphincter am. The mucous membrane of the large intestine differs considerably from that of the small. There are neither valvulse conniventes nor 1. Ileum. 2. Csecumorcaput'COli. 3. Appendix vermi- formis. SECTION THKOUGH THE JUNCTION OF THE LARGE AND SMALL INTESTINE, TO SHOW THE ILEO-C-ECAL VALVE. villi, but the glands of Lieberkiihn and the lymphoid follicles may i be seen studding the mucous membrane. The follicles are more abundant in the caecum and in the appendix vermiformis than in any other part of the alimentary canal. The blood-vessels present the same hexagonal arrangement on the surface as that of the stomach. That the mucous membrane of the large intestine may be temporarily used as a substitute for the stomach is proved by the fact of persons having been nourished for many weeks solely by injections. The mucous membrane is lined throughout with columnar epithelium. ILEO-C,ECAL At the junction of the small with the large VALVE, intestine the mucous membrane is folded so as to 606 STRUCTURE OF THE LARGE INTESTINE. form a valve : but it is not a perfect one, as is proved by pouring water into the large intestine, or by the occasional vomiting of in- jections. The arrangement of the valve is best examined in a dried preparation. The opening is a transverse fissure like a button- hole ; and the two flaps are arranged like an upper and a lower eyelid. The upper lid of the valve projects more than the lower, so that the contents of the ileum drop naturally down into the caput coli, where they are apt to collect and form hard lumps. The flaps of the valve consist of mucous membrane and the circular fibres of the ileum. The longitudinal fibres of the ileum are continued directly on to the caecum : if these be divided, the ileum can be drawn out, and the valve disappears. 1 FOLDS IN THE In many subjects we observe that transverse or BECTUM. oblique folds of the mucous membrane project into the rectum. These cannot be seen to advantage unless the bowel be hardened by alcohol in its natural position. Three, more pro- minent than the rest, and half an inch, or thereabouts, in width, were first pointed out by Mr. Houston. 2 One projects from the upper part of the rectum, opposite the prostate gland ; another is situated higher up, on the side of the bowel ; while the third is still higher. When thickened or ulcerated, these folds are apt to occasion great pain and obstruction in defaecation. AKTEKIAL ^6 P resent opportunity is the best for review- SUPPLY OF THE ing the arterial supply of, and the anastomoses ALIMENTARY round, the alimentary canal, from the mouth to the anus. Part of the blood supply has been ex- amined in the dissection of the head and neck ; part in the dis- section of the oesophagus as it passes through the thorax ; and the* remainder in that of the abdomen. The following table represents the arteries in their order, beginning at the mouth : LOWER LIP Submental (deep branch). Mental. Inferior labial. Inferior coronary. 1 It is interesting to note that the surface of the valve, towards the ileum, is covered with villi ; not so the surface towards the large intestine. 2 Dublin Hospital Reports, vol. v. p. 163. ARTERIAL SUPPLY OF THE ALIMENTARY CANAL. 607 UPPER LIP CHEEK MOUTH, ROOF OF ... MOUTH, FLOOR OF, AND TONGUE EPIGLOTTIS PHARYNX (ESOPHAGUS, CERVICAL . (ESOPHAGUS, THORACIC . (ESOPHAGUS, ABDOMINAL STOMACH . DUODENUM Superior coronary. Buccal. Superior coronary (slightly). Facial. Transverse facial. Infra- orbital. Superior alveolar. Descending palatine. Ascending palatine. Pharyngeal br. of ascending pharyngeal. Artery of the fnenum. Ranine. Sublingual. Dorsales linguse. Tonsillar. Ascending palatine. Ascending pharyngeal. Superior laryngeal artery. Pterygo-palatine. Branches of ascending pharyngeal. Branches of ascending palatine. Superior thyroid. Superior thyroid. Inferior thyroid. Inferior thyroid. Thoracic aorta. Gastric. Left phrenic. Gastric. Left phrenic. Gastric. Pyloric. Gastro-epiploica dextra. Gastro-epiploica sinistra. Yasa brevia. Gastro-duodenalis. Pancreatico-duodenalis superior. Pancreatico-duodenalis inferior. 608 ARTERIAL SUPPLY OF THE ALIMENTARY CANAL. JEJUNUM Superior mesenteric. ILEUM Superior mesenteric. C^CUM Colic br. of ileo-colic. ASCENDING COLON . Colica dextra. TRANSVERSE COLON . Colica media. DESCENDING COLON . Colica sinistra. SIGMOID FLEXURE . . Sigmoid arteries. RECTUM Superior hsemorrhoidal (inferior mesenteric). Middle hsemorrhoidal (internal iliac). Inferior hsemorrhoidal (internal pudic). Arteria sacra media. 609 DISSECTION OF THE LOWER EXTREMITY. THE body must be placed on its back, with a block placed beneath the buttocks, and the thigh should then be slightly flexed and abducted. SURFACE The student, before commencing to reflect the MARKING. skin, should notice the irregularities of the surface which are produced by subjacent structures. The upper part of the thigh is marked off from the abdomen by a more or less well- marked curved furrow, having its convexity downwards. This furrow corresponds with Poupart's ligament, which is attached externally to the anterior superior iliac spine, and internally to the spine of the os pubis. The spine of the os pubis can, even in the fattest subject, be distinctly felt, and is a very valuable land- mark in the diagnosis between an inguinal and a femoral hernia ; for the aperture through which an inguinal hernia emerges is the external abdominal ring, situated above the spine ; the aperture through which a femoral hernia comes out is the saphenous open- ing, situated outside the spine. In front of the thigh is a large triangular depression corresponding with Scarpa's triangle, which has its base at. Poupart's ligament. This depression, which is best seen in thin subjects, contains the large vessels and nerves passing down to the leg, the femoral artery being nearly in the centre of the space : a furrow indicating the course of these vessels may be observed extending obliquely down the inner side of the thigh. About three or four inches below the anterior superior iliac spine, there is seen on the outer side of the thigh the well- marked prominence of the great trochanter, which is nearly on the same level as the spine of the os pubis. The sartorius can be seen passing obliquely inwards from the iliac spine, and crossing over the femoral vessels about four inches below Poupart's ligament ; in the latter two-thirds of its course it descends nearly vertically. R R 610 SUPERFICIAL FASCIA OF THE GROIN. The well-defined ridge, extending from the os pubis to the middle of the femur, when the thigh is abducted, is caused by the adductor longus muscle. The prominence in front of the knee is produced by the patella, to which is attached above, the tendon of the quadriceps muscle, and below, the ligamentum patellae, both of which can be distinctly felt. On each side of the patella is a deep depression, which leads on the outer side to a rounded prominence, the external condyle ; and on the inner to the internal condyle, the latter being the larger. The synovial membrane which lines the knee-joint usually extends about two fingers' breadth above the patella, and is a little higher on the inner than on the outer side of the joint. An incision should be made along the groin, extending from the anterior superior spine of the ilium to the spine of the os pubis ; another, from the middle of the first down the front of the thigh for about six inches. The skin only should be reflected, outwards and inwards, when the superficial fascia will be exposed. SUPERFICIAL The superficial fascia varies in thickness, ac- FASCIA. cording to the condition of the body. Like other superficial fasciae, it is divisible into two or more layers, be- tween which are situated the inguinal glands and the cutaneous vessels and nerves. The superficial layer is continuous with that of the abdomen, and becomes firmer below Poupart's ligament, to which, however, it is not connected ; the deeper layer is best marked in the upper part of the thigh, especially where it stretches across the saphenous opening, to the margins of which it is closely attached ; this portion is called the cribriform fascia, and is pro- truded forwards by a femoral hernia, forming one of its coverings ; this layer is also attached to Poupart's ligament. The superficial layer of this fascia should now be reflected, by searching for one of the subcutaneous veins (the internal saphena will do) which run between the upper and the deeper layers of the fascia. The cutaneous vessels can thus be traced, and come from the common femoral artery ; they are three in number, the super- ficial epigastric, the superficial external pudic, and the superficial circumflexa ilii arteries. The first ascends over Poupart's ligament to the abdomen (p. 612) ; the second crosses inwards towards the SUPERFICIAL ARTERIES OF THE GROIN. 611 ps pubis; the third passes outwards to the ilium. Each artery is accompanied by one, sometimes by two veins, which empty them- selves, either directly into the femoral, or into the great cutaneous vein of the thigh, called the saphena. SUPERFICIAL These glands are easily recognised, by their INGUINAL oval form and reddish-brown colour. There are GLANDS. ^ wo ge g . one gQ ^ runs parallel to Poupart's liga- ment, and receives the lymphatics from the skin of the penis, the scrotum, the perineum, the anus, the buttock, the lower part of the abdominal wall, and the upper and outer aspect of the thigh ; the outer and lower set lies along the saphena vein, chiefly around the saphenous opening, and receives the lymphatics frdm the foot, the leg, and the lower part of the thigh. This explains why in cancer of the scrotum and syphilitic disease of the penis the first set becomes enlarged ; and the second, in diseases of the lower ex- tremity. The lymphatic vessels which pass to and from the glands are small, and may escape observation, unless specially looked for. They all pass through the femoral ring into the abdomen, and eventually empty themselves into the receptaculum chyli. The glands mentioned in the preceding paragraph are all super- ficial. There are others, more deeply seated, close to the great vessels of the thigh : these are much smaller, and sometimes cannot be found. SUPERFICIAL The superficial epigastric artery comes through ARTERIES OF the fascia lata, sometimes through the saphenous THE GROIN. opening, half an inch below Poupart's ligament. It ascends over Poupart's ligament to pass to the subcutaneous tissue of the abdomen, as high as the umbilicus, and supplies the inguinal glands, and anastomoses with the deep epigastric and internal mammary arteries. Its further course is described at p. 423. The superficial circumfiexa ilii emerges through the fascia lata, runs parallel to Poupart's ligament towards the crest of the ilium, and ends in the subcutaneous tissue and inguinal glands. It anastomoses with the deep circumflex iliac, the gluteal, and the ascending branches of the external circumflex arteries. The superficial external pudic comes through th<^ saphenous B R 2 612 SUPERFICIAL ARTERIES OF THE GROIN. opening, crosses over the spermatic cord, and supplies the penis and scrotum in the male, and the labium in the female. This artery is usually divided in the operation for femoral hernia ; also in that for phymosis, since it runs along the penis to supply the FIG. 143. SUPERFICIAL VESSELS AND GLANDS OF THE GROIN. SAPHENOUS OPENING WITH THE CRIBRIFORM FASCIA. 1. Saphenous opening of the fascia lata. 2. Saphena vein. 3. Superficial epigastric artery. 4. Superficial circumflexa ilii artery. 5. Superficial pudic artery. 6. External abdominal ring. 7. Fascia lata of the thigh. prepuce. Arising directly from so large an artery as the femoral, it sometimes bleeds profusely ; for it is an admitted fact that when even a small branch, coming directly from a principal artery, is divided near its origin, it will sometimes pour out as much blood as if an opening were punched out of the trunk as large as the INTERNAL SAPHENA VEIN. 613 'area of the divided branch. 1 There is another pudic artery, called the deep or inferior external pudic : this runs between the fascia lata and the pectineus, supplying that muscle, the scrotum in the male, and the labium in the female. They both anastomose with branches of the internal pudic artery. The incision should be prolonged down the thigh, over the knee to the tubercle of the tibia. The skin must then be reflected, to expose the subcutaneous tissue over the whole of the front of the thigh. The cutaneous vessels and nerves should be looked for in the subcutaneous fat in the following situations : on the inner side are the inguinal branch of the ilio-inguinal nerve passing down through the external abdominal ring, internal to the saphenous opening ; lower down, are the two branches of the internal cutaneous nerve supplying the skin on the inner aspect of the thigh as far as the knee, the lower branch accompanying the internal saphena vein which ascends to pierce the saphenous opening ; there are also low down some filaments from the long saphena nerve ; on the front of the thigh there is found the crural branch of the genito-crural nerve, and lower down, as far as the knee are the middle cutaneous nerves ; on the outer side are seen filaments of the external cutaneous nerve. INTEBNAL This is the chief subcutaneous vein of the lower SAPHENA limb. Its roots, arising from the inner side of a VEIN< venous arch on the dorsum of the foot, unite into a single trunk, which ascends in front of the inner ankle, along the inner side of the leg, behind the knee, along the inner and front part of the thigh, where it passes through an opening the saphe- nous opening in the fascia lata, to join the femoral vein, imme- diately below the crural arch (fig. 143). In this long course it receives many tributary veins, some of which are often large, especially one which, coursing round the inner part of the thigh, is frequently as large as the main trunk. Just before its termination it is joined by the superficial veins, which accompany the arteries of the groin, already alluded to, p. 611. Like all J Mr. Listen had occasion to tie the external iliac artery for a supposed injury (by a pistol-ball) to the femoral. It was discovered, after the death of the patient, that the ball had injured only one of the superficial branches of the femoral about an inch from its origin. See his paper in the Med. Chir. Trans, vol. xxix., 1846. 614 CUTANEOUS NERVES OF THE THIGH. subcutaneous veins, it is provided with valves, chiefly where joined by other veins, to support the column of the blood. CUTANEOUS The distribution of the cutaneous nerves of the NEKVES. thigh varies considerably, but they are always found more abundantly on the inner than on the outer aspect of the thigh. The nerves are divided into external, middle, and internal. All directly or indirectly proceed from the lumbar plexus, and, perforating the fascia lata, divide in the subcutaneous tissue. a. The external cutaneous nerve is a branch of the second and third lumbar nerves. It enters the thigh beneath Poupart's liga- ment close to the anterior superior spine of the ilium. Here it divides into two branches, an anterior and a posterior. The anterior branch comes through the fascia lata about four inches below Poupart's ligament, and can be traced down the outer side of the thigh as far as the knee, giving off numerous branches. The posterior branch, after coming through the fascia lata, divides into filaments, which are distributed to the skin over the nates and the posterior part of the thigh. b. The middle cutaneous nerves, one or two in number, are given off by the anterior crural in the thigh. They pass through the sartorius about four inches below Poupart's ligament, perforate the fascia lata, and descend along the front and inner part of the thigh as far as the knee, distributing branches on either side ; some of which communicate with the long saphenous nerve. In its course along the front of the thigh it joins with the crural branch of the genito-crural and the internal cutaneous nerves. c. The internal cutaneous nerve, also a branch of the anterior crural, crosses obliquely over the sheath of the femoral artery. It then divides into two branches, an anterior and an internal ; the anterior branch comes through the fascia lata in the lower third of the thigh, where it terminates in two branches, one being distri- buted to the inner side of the knee, the other crossing over the patella to the outer side of the joint ; the internal branch perforates the fascia lata just above the knee-joint, after running down along the posterior border of the sartorius, and supplies the integument on the inner side of the leg. Whilst still beneath the fascia lata, FASCIA LATA. 615 the internal cutaneous nerve unites below the adductor longus in a plexiform manner with the long saphenous and obturator nerves. 1 d. The crural branch of the genito-crural nerve perforates the anterior layer of the sheath of the femoral vessels, comes through the fascia lata immediately below Poupart's ligament, and supplies the skin in front of the thigh. About two or three inches below the crural arch it usually communicates with the middle cutaneous nerve. It also distributes a few filaments to the femoral artery in its passage under the crural arch. e. The inguinal branch of the ilio-inguinal nerve, after emerging from the external abdominal ring, supplies the skin on the inner aspect of the upper third of the thigh. Remove the subcutaneous fat and the deeper layer of the superficial fascia, to examine the dense white fascia the fascia lata of the thigh. The use of this fascia is to cover the muscles of the thigh collectively, and to form separate sheaths for each ; so that it not only keeps them together, but maintains each in its proper position. A knowledge of these sheaths is important, because they interfere with the progress of deep-seated matter towards the surface, and cause it to burrow in this or that direction according to the part in which it forms. The fascia is not of equal strength all round the thigh. It is comparatively thin on the inner side ; exceedingly thick and strong down the outer side ; here, indeed, it has the appearance of a dense expanded aponeurosis, strapping down the vastus externus muscle, and is sometimes called the ilio-tibial band ; and it certainly per- forms the office of a tendon, for it gives insertion between its two layers to two powerful muscles namely, the tensor fasciae femoris, and the gluteus maximus (fig. 144). The fascia lata is attached to the margin of the bones which constitute the framework of the lower extremity. Beginning from above, its attachment can be traced from the posterior surface of the sacrum and coccyx, along the crest of the ilium, thence along 1 It is important to note that one, sometimes two, of these branches of the internal cutaneous crosses the sheath of the femoral artery, just where the sartorius begins to overlap it, and therefore at the spot where it is usually tied. See diagram, p. 628. 616 FASCIA LATA. FIG. 144. Poupart's ligament to the body of the os pubis and the linea ilio- pectinea, and along the rami of the os pubis and ischium. Pro- ceeding down the thigh, it penetrates on each side of the limb to the linea aspera, forming what are called the external and internal intermuscular septa ; the external one, the stronger, separates the vastus externus anteriorly from the short head of the biceps, both of which have origin from the fascia ; the internal one separates the vastus in- ternus in front from the adductor muscles behind. Below, it can be traced round the knee-joint, and is particularly strong, especially on the outer side, where it is attached to the head of the tibia and fibula, and forms the insertion of the tensor fascias femoris. The fascia lata is very strong over the gluteus medius the gluteal aponeiirosis, and at the upper border of the gluteus maximus divides into two layers, one superficial to the muscle, the other deep which separates this muscle from the deeper muscles, and becomes connected with the great sacro-sciatic ligament. The fascia lata also furnishes thinner sheaths for the separate muscles. There are numerous small apertures in the fascia, through which the cutaneous nerves and vessels are transmitted but the most important one is the large opening the saphenous opening through which the saphena vein passes to join the femoral. The part of the fascia situated ex- FASCIA ON THE OUT- ternal to the saphenous opening is termed the SIDE OF THE THIGH, iliac portion of the fascia lata ; that internal to it, 1. Tensor fascise femoris. the pubic portion. 2. Gluteus maximus. 3. Lower fibres of ditto. 4. Fascia lata. The iliac portion is attached to the crest of the ilium, to the whole length of Poupart's ligament, and, in conjunction with Gimbernat's ligament, to the linea ilio- pectinea ; from this attachment it arches downwards and outwards, its inner margin forming the outer falciform edge of the saphenous opening ; this border passes over the anterior sheath (formed by the transversalis fascia) of the femoral artery, and is seen to be SAPHENOUS OPENING. 617 continuous below with the pubic portion, which can be traced up- wards over the pectineus and adductor longus muscles, behind the posterior sheath (formed by the iliac fascia) of the femoral vessels, where it is connected with the sheath of the iliacus and psoas muscles and the fibrous structures of the hip-joint. Above, it is attached to the linea ilio-pectinea, to the body and the ramus of the os pubis. SAPHENOUS r -^ ne saphenous opening is an oval aperture in the OPENING IN THE fascia lata, immediately below the crural arch, on FASCIA LATA. foe j nner & {^ e o f the front of the thigh, through which the saphena vein passes to join the femoral. There is no FIG. 145. 1. Crural arch. 2. Saphenous opening of the fascia lata. 3. Saphena vein. 4. Femoral vein. 5. Gimbernat's ligament. 6. External abdominal ring. 7. Position of the in- ternal ring in dotted outline. DIAGBAM OF THE FEMOKAL RING AND THE SAPHENOUS OPENING. (The arrow is introduced into the femoral ring.) definite border to the saphenous opening until the fascia cribriform, which covers the opening and blends with its margin has been removed. It is situated just below the crural arch and external to the spine of the os pubis ; it is oval, with the long axis vertical, and is about one inch and a half long and an inch broad. Its border on the inner side is not defined ; for here the fascia lata ascends under the femoral vessels, and is continuous with the iliac fascia of the pelvis. 1 But the outer or iliac border is clearly defined. This 1 On the inner side of the femoral vessels the pubic portion of the fascia is attached to the linea ilio-pectinea. 618 CRIBRIFORM FASCIA. lies in front of the femoral vessels, is crescent-shaped, with the concave upper end towards the os pubis, and is called the falciform process, whilst its deeper fibres are known as Burns' ligament. The lower horn of the crescent curves under the saphena vein with a well-defined border, and on being traced upwards becomes less well marked until it is gradually lost in the fascia on the inner side of the opening. The upper horn, Hey's ligament, 1 arches over the femoral vein, and then descending slightly is continued unin- terruptedly into Gimbernat's ligament i.e. into that part of the crural arch which is inserted into the linea ilio-pectinea. The upper horn deserves especial attention, because it forms the upper boundary of the aperture through which a femoral hernia takes place; and, being chiefly concerned in the constriction of the rupture, must be divided for its relief. This may be easily ascer- tained by introducing the little finger under the crural arch, on the inner side of the femoral vein in other words, into the femoral ring (see the arrow in the diagram). Feel how the upper horn of the crescent would gird the neck of a hernia, and that its tension is greatly influenced by the position of the limb ; for if the thigh be bent and brought over to the other side, the tension of all the parts is materially lessened. 2 CKIBBIFOKM The cribriform fascia is so called because it is FASCIA. perforated with numerous apertures for the passage of the superficial vessels and lymphatics. It is a thin membranous covering over the saphenous opening, and is prolonged from the outer edge of the opening over the sheath of the femoral vessels, and adheres on the inner side to the fascia lata, over the pectineus muscle. Some anatomists describe this fascia as a portion of the deeper layer of the superficial fascia ; others consider it as a thin prolongation of the fascia lata itself across the opening. Its chief 1 This upper horn is sometimes called Hey's ligament, after the surgeon who first drew attention to it. (Observations in Surgery, by W. Hey, F.E.S. London, 1810.) 2 We must .always bear in mind that, though the crural arch and the fascia attached to it have received particular names, they are not, on that account, distinct and separate ; but all are intimately connected, and portions merely of one con- tinuous expansion. Thus all the parts are kept in a condition of mutual tension, which depends very much on the position of the thigh. PARTS CONCERNED IN FEMORAL HERNIA. 619 surgical importance is derived from the fact that it forms one of the coverings of a femoral hernia. The cribriform fascia must now be removed on one side so as to display the saphenous opening, which will appear as represented in fig. 145. ANATOMY OF THE PARTS CONCEENED IN FEMORAL HERNIA. The anatomy of the parts concerned in femoral hernia cannot be thoroughly understood without the assistance of special dissec- tions. The following demonstration therefore takes for granted that the student has the opportunity of seeing the parts, not only on their femoral, but also on their abdominal side. The different parts of the subject should be examined in the following order : a. The formation of the crural arch. b. The arrangement of the parts as they pass under the arch. c. The sheath of the femoral vessels. d. The crural canal and ring. e. The practical application of the subject. POUPAKT'S ^ ne lower border of the aponeurosis of the LIGAMENT OR external oblique muscle extends from the anterior CRURAL ARCH. superior spine of the ilium to .the spine of the os pubis, and forms over the bony excavation beneath the crural arch or Pouparfs ligament. (It is marked by the dark line in fig. 145.) The direction of the arch is at first somewhat oblique, but towards its inner half becomes nearly horizontal. In consequence of its intimate connection with the fascia lata of the thigh, the line of the arch describes a gentle curve with the convexity downwards. The arch is attached to the spine of the os pubis, and also for some distance along the linea ilio-pectinea (fig. 145). This additional attachment, called Gimbernafs ligament^ is of importance, for it is frequently the seat of stricture in femoral hernia. GIMBERNAT'S The best view of Gimbernat's ligament is ob- LIGAMENT. tained from within the abdomen ; it being only 1 Don Antonio de Gimbernat was a Spanish surgeon, who published, in 1793, A New Method of Operating for the Femoral Hernia. Madrid. 620 PARTS CONCERNED IN FEMORAL HERNIA. necessary to remove the peritoneum. It is that portion of the aponeurosis of the external oblique muscle which is inserted into the linea ilio-pectinea for about an inch in length. It is placed nearly horizontally in the erect posture, and is triangular with its apex at the os pubis and its base directed outwards. In front, it is continuous with the crural arch ; behind, it is inserted into the linea ilio-pectinea ; externally, it is continuous with the fascia lata through Hey's ligament (fig. 145). Its length is from three- quarters of an inch to one inch ; but it is usually longer in the male than in the female. On putting your finger into the femoral ring, you feel the sharp and wiry edge of this ligament : observe, too, that as the body lies on the table, the plane of the ligament is perpendicular, and therefore that it recedes from the surface. An incision should now be made through the fascia lata along the entire length of Poupart's ligament ; another also through the fascia vertically, from the anterior superior iliac spine down the thigh for about four inches ; and the fascia lata carefully dissected downwards and inwards from the subjacent structures. This will expose the structures as they pass under Poupart's ligament in their course down the thigh. ARRANGEMENT ^^ e crura ^ arcn transmits from the abdomen into OF THE PARTS the thigh (proceeding in order from the outer side) WHICH PASS UNDER the following objects shown in fig. 146 : 1. The THE ARCH. external cutaneous nerve. 2. The iliacus with the anterior crural nerve lying on it near its inner border. 3. The femoral artery resting on the psoas muscle. 4. The crural branch of the genito-crural nerve. 5. The femoral vein. 6. The crural sheath surrounding the femoral vessels, formed in front by the fascia transversalis, behind by the fascia iliaca. 7.The lymphatics passing upwards through the femoral canal. 8. The pectineus. These muscles and vessels fill up the space beneath the crural arch, except on the inner side of the femoral vein, where a space is left for the passage of the lymphatics : this is called the crural or femoral ring. The muscles are separated from the vessels by a strong vertical fibrous partition passing from the arch to the bone, which is nothing more than a continuation of the sheath of the psoas. The artery, too, PARTS CONCERNED IN FEMORAL HERNIA. 621 is separated from the vein by a similar, although a much weaker partition, and there is a third close to the inner side of the vein. These three partitions not only keep all the parts in their right place, but confine the arch down to the bone, and prevent its being uplifted by any protrusion between it and the muscles and vessels. This, coupled with the close attachment of the fascia iliaca to the crural arch, explains why a femoral hernia rarely takes place in any other situation than on the inner side of the femoral vein. 1 . 146. External cutaneous n. Iliacus Anterior crural n. . . . Psons. , ... Crural arch. External ring. Femoral ring. Femoral vein and artery. POSITION OF PAETS UNDER THE CKUEAL AECH (VERTICAL SECTION). SHEATH OF THE The femoral vessels descend beneath the crural FEMORAL VESSELS, arch, enclosed in a funnel-shaped membranous sheath. This sheath appears to be derived immediately from the arch itself, but it is really formed in front by a prolongation from the fascia transversalis of the abdomen. This prolongation, uniting with the continuation from the fascia iliaca (to join the fascia lata) behind the femoral vessels, forms a funnel, with the wide part 1 If the partitions from any cause yield, or become slack, then a rupture may descend in front of the vessels, or even (though this is rare) on the outer side of the artery. 622 PARTS CONCERNED IN FEMORAL HERNIA. uppermost, into which the femoral vessels enter. This is the funnel-shaped sheath of the femoral vessels. The fascia transversalis, descending over the femoral vessels, forms the front part of their sheath ; the hind part of the sheath is formed by the fascia iliaca, which runs down behind the vessels to join the pubic portion of the fascia lata. The sheath descends as low as the lower horn of the saphenous opening, where it is gradu- ally lost upon the external cellular coat (tunica adventitia) of the femoral vessels. The outer part of the sheath, in front, is perforated FIG. 147. 1, 1. Fascia transver- salis. 2. Internal ring. 3. Crural arch re- flected. 4. Sheath of the fe- moral vessels. 5. Saphena vein. DIAGRAM OF THE SHEATH OF THE FEMORAL VESSELS. by the crural branch of the genito-crural nerve, and the superficial arteries of the groin ; the inner part, by the saphena vein and some lymphatic vessels. The sheath of the femoral vessels is divided into three com- partments separated from each other by partitions : the outer is occupied by the femoral artery; the middle, by the femoral vein ; the inner is the crural canal, into which a femoral hernia descends. The deep crural arch is the thickened band of fibres connected with the front of the crural sheath; the fibres run in the same PARTS CONCERNED IN FEMORAL HERNIA. 623 direction as the crural arch, but quite independently of it, as shown in fig. 147; these bands He over the neck of the sac of a femoral hernia, and are often the seat of the stricture. Practically, the sheath is important for many reasons : 1. A femoral hernia descends within it. 2. It constitutes, therefore, one of the coverings, fascia propria, of the hernia. 3. It contains within its substance the deep crural arch, which not infrequently forms the stricture of a femoral hernia, and has, therefore, to be divided before the intestine can be returned. CKURAL CANAL The hollow under the crural arch is completely AND FEMORAL occupied by the. structures before mentioned, ex- RlNQ - cept for a small triangular space, forming the inner compartment of the femoral sheath, called the crural canal. The canal is on the inner side of the femoral vein, and is from a quarter to half an inch in length. Its base commences above in the femoral ring, and its apex ends below at the saphenous opening. In front, it has Poupart's ligament and the falciform process of the iliac portion of the fascia lata, and is formed by the fascia trans- versalis ; behind, it is formed by the fascia iliaca ; internally, it is formed by the junction of the fascia transversalis and the fascia iliaca, and is in relation with the base of Gimbernat's ligament; externally, it is separated from the femoral vein by the septum of fascia which divides the middle from the inner compartment of the crural sheath. The femoral ring is the upper opening of the crural canal, and is bounded, in front, by the superficial and deep crural arches ; behind, by the horizontal ramus of the os pubis, the pectineus, and the pubic portion of the fascia lata ; on the outer side, by the fascial septum separating it from the vein ; on the inner side, by the thin, wiry edge of Gimbernat's ligament, the conjoined tendon of the internal oblique and transversalis, the fascia transversalis, and the fibres of the deep crural arch. In the undisturbed con- dition of the parts there is no gap ; it is only a weak place, which, when a hernia escapes through it, feels like a ring : hence the name of femoral ring. 1 1 The femoral ring is naturally occupied by a little fat and cellular membrane, by lymphatic vessels, and often by a small lymphatic gland. But we have never 624 PARTS CONCERNED IN FEMORAL HERNIA. The femoral ring is surrounded on all sides by unyielding structures. This accounts for the little benefit afforded by the warm bath in cases of strangulation. Sir W. Lawrence was in the habit of saying that he never saw a strangulated femoral hernia where the warm bath was of any avail. PRACTICAL From what has been said, the student ought APPLICATTON OF now to understand 1, at what aperture a femoral THE SUBJECT. hernia escapes from the abdomen ; 2, the course which it takes, and its relations to the surrounding parts ; 3, the proper mode of attempting the reduction ; 4, the structure and arrangement of its coverings ; and, 5, the probable seat of stricture. The hernia escapes from the abdomen through the femoral ring that is, under the weak part of the crural arch, between the femoral vein and Gimbernat's ligament. Here is the mouth of the hernial sac, or that part of it which communicates with the abdomen. It descends for a short distance nearly perpendicu- larly, and projects as a small tumour in front of the pectineus muscle. Its progress downwards, however, is soon arrested, partly by the very close adhesion of the subcutaneous structures to the lower margin of the saphenous opening ; partly by the flexion of the thigh. Consequently, if the hernia increases in size, it usually rises over the crural arch, where the subcutaneous tissue offers less resistance ; and the bulk of the hernia extends outwards towards the ilium, assuming more or less of an oblong form, with the long axis parallel to the crural arch. Since, then, the body of the hernia forms a very acute angle with the neck, the right mode of attempting its reduction is, to draw it, first, down from the groin, and then to make pressure on it, backwards, in the direction of the femoral ring. COVERINGS OF The coverings of a femoral hernia are as fol- A FEMORAL lows : It first protrudes before it the peritoneum, HERNIA - technically called the hernial sac. 1 The sac is met with anything deserving the name of a diaphragm or membranous septum, such as is described by Cloquet as the septum crurale, and is, surgically, of no importance. 1 In some cases the fascia propria so much resembles the hernial sac, that it is not easy to distinguish between them. Generally speaking, they are separated by a small quantity of fat. PARTS CONCERNED IN FEMORAL HERNIA. 625 covered by more or less fat, according to the condition of the patient, called the siibperitoneal fat. It next pushes before it the sheath of the femoral vessels, which forms an investment more or less thick. In front of this is the cribriform fascia. Lastly, there is the subcutaneous tissue and skin. SEAT OF The seat of stricture is usually at the femoral STRICTURE. ring, and the position of the neighbouring blood- vessels indicates that the proper direction in which to divide the FIG. 148. VIEW OF THE DIFFERENT DIRECTIONS WHICH AN ABNORMAL OBTURATOR ARTERY MAY TAKE. (SEEN FROM ABOVE.) A. 1. Q-imbernat's ligament. B. 1. Gimbernat's ligament. 2. Femoral ring. 2. Abnormal obturator artery. 3. Abnormal obturator artery. 3. Femoral ring. 4. External iliac vein. 4. External iliac vein. 5. External iliac artery. 5. External iliac artery. 6. Diminutive obturator artery arising 6. Diminutive obturator artery. from its normal source. stricture is, either directly inwards, through Gimbernat's ligament, as recommended by Sir W. Lawrence, or upwards through Key's ligament, as recommended by Sir A. Cooper. 1 There is no risk of wounding an artery, supposing the vessels to take their ordinary course. But it occasionally happens (fig. 148), that the obturator artery runs above (in the recumbent position) the femoral ring ; in such a case, the neck of the sac would be encircled by a large 1 The operation recommended by Sir A. Cooper is that usually performed now ; because, if Gimbernat's ligament be divided, its cut edges often retract to such an extent, that no truss can possibly retain the hernia when the patient assumes the erect posture. S S 626 SARTORIUS. Hood- vessel. 1 From the examination of two hundred bodies, the chances are about seventy to one against this unfavourable dis- tribution. But the possibility of it has given rise to this rule in practice not to cut deeply in any one place through the stricture, but rather to notch it in several. By this proceeding we are much less likely to wound the abnormal artery, because it does not run at the base of Gimbernat's ligament, but about a line and a half from the margin of it. 2 Such is an outline of the anatomy of the parts concerned in a femoral hernia. The normal anatomy in each case being similar, it might be supposed that all operations for the relief of this kind of hernia would be straightforward and pretty much alike ; but this is very far from being the case : indeed, surgeons agree that they never operate without the expectation of meeting some peculiarity. The fascia must now be removed from the front of the thigh, without disturbing the subjacent muscles from their relative positions. The mass of muscles, on the inner side of the thigh, consists of the adductors ; that in the middle, of the extensors : the long thin muscle crossing obliquely in froi: from the outer to the inner side is the sartorius. In the middle are seen the femoral vessels, and the anterior crural nerve emerging beneath the crural arch. This, a narrow, flat muscle (fig. 149, i), arises SABTOBIUS. ,, ,, r ,, .,. -. from the anterior superior spine of the ilium, and from the ridge below to the extent of an inch. It passes obliquely like a strap over the front of the thigh towards the inner side ; and then descends almost perpendicularly on the inner side of the thigh as far as the knee, where it terminates in a flat tendon which expands, 1 The museum of St. Bartholomew's Hospital contains two examples of double femoral hernias in the male, with the obturator arising on each side from the epigastric. In three out of four herniae the obturator runs on the inner side of the mouth of the sac. * During the session of 1867-68 more than half a dozen instances occurred where the obturator artery was given off by a common origin with the epigastric artery. In all these cases, however, the artery passed close by the bone, that is, behind the sac, so that it would not have been injured in the operation for the relief of strangulation. SCARPA'S TRIANGLE. 627 and is inserted into the inner and front part of the tibia just below its tubercle. The tendon appears all the wider on account of its broad connection with the fascia of the leg, which extends as low as the internal malleolus. The broad insertion of this muscle lies anterior. to and covers the tendinous insertions of the gracilis and semi-tendinosus, and between them is a bursa. A large bursa l is interposed between the tendon and the internal lateral ligament. The chief action of the muscle is to fix the pelvis steadily on the thigh. 2 It first bends the leg upon the thigh, and then bends the thigh upon the abdomen. It crosses one leg over the other, as tailors sit when at work. If the leg be the fixed point, it will bend the trunk upon the thigh and rotate the pelvis inwards. Its nerve conies from the middle cutaneous branch of the anterior crural. SCARPA'S I n consequence of the oblique direction of the TRIANGLE. upper third of the sartorius, a triangle is formed, which has this muscle and the adductor longus for its two sides, and the crural arch for its base : the triangle is called Scarpa's. 3 Its floor is formed by the iliacus, the psoas, the pectineus, and the adductor longus, with sometimes the adductor brevis between the borders of the two latter muscles. The contents of this important space should be carefully displayed, and their relative positions well studied. This triangle contains all the parts which pass under the crural arch : namely, from without inwards, the external cuta- neous nerve, close to the anterior spine of the ilium ; the iliacus and psoas ; the anterior crural nerve and its divisions, especially the long saphenous nerve ; the crural branch of the genito-crural nerve, the common femoral artery with its two large divisions, the superficial femoral and the profunda, which run down, nearly parallel to each other, the latter being the more external and giving off the internal and external circumflex arteries ; the 1 In persons, females especially, who are in the habit of riding, this bursa sometimes becomes enlarged. 2 Hence the name given to it by Spigelius (De Corporis Hum. Fabric.), ' Quern ego sartorium musculum vocare soleo, quod sartores eo maxim utuntur, dum crus cruri inter consuendum imponunt.' 8 So called in compliment to the Italian anatomist who first tied the femoral in it for popliteal aneurism. s s 2 628 ADDUCTOR MUSCLES. femoral vein, joined by the proftmda vein and the internal saphena, and the pectineus muscle with the deep external pudic artery. The triangle is important in a surgical point of view, since it is in this Space that the femoral artery is usually ligatured for FIG. 149. 1. Sartorius. 2. Adductor longus. 3. External cutaneous n. 4. Iliacus internus. 5. Anterior crural n. 6. Femoral arterv. 7. Femoral vein. 8. Pectineus. 9. Long saphenous n. 10. Internal cutaneous n. 11. Nerve to vastns in- ternus. 12. Middle cutaneous n. DIAGRAM OF SCARPA's TRIANGLE. popliteal aneurism. The guide to the artery is the inner border of the sartorius. The situation at which this muscle crosses over the femoral artery, varies from one and a half to four and a half inches below Poupart's ligament; so that no rule can be laid down as to the exact situation where the artery disappears beneath the sartorius. The best way to find the inner border of the muscle during life, is to make the patient put it in action. ADDUCTOR A. strong group of muscles, called the adductors, MUSCLES. extends along the inner side of the thigh, from the pelvis to the femur. Their two most important actions are to co-operate in balancing the pelvis steadily on the thigh, as in ADDUCTOR MUSCLES. C29 standing on one leg ; and (if the fixed point be reversed) to draw- together or adduct the thighs, at the same time rotating the thigh externally. They are five in number, and are supplied, with one exception the pectineus by the same nerve, namely, the obtu- rator. They are termed, respectively, the gracilis, adductor longus, pectineus, adductor brevis, and adductor magnus. The innermost is the gracilis ; to clean it properly, it should be stretched by separating one thigh from the other. This long, flat muscle arises by a broad, ribbon- like tendon, two to three inches in breadth, from the os pubis close to the symphysis, and from the inner margin of the rami of the os pubis and ischium. It descends almost perpen- dicularly on the inner side of the thigh, and terminates in a thin round tendon which subsequently spreads out, and is inserted into the inner side of the upper part of the tibia below the tubercle, immediately behind the sartorius and above the semi-tendinosus. The tendon plays over the internal lateral ligament of the knee- joint, and there is a bursa common to it and the semi-tendinosus to diminish friction. This muscle assists in fixing the pelvis, and in adducting the thigh ; it further helps to bend the knee. Its nerve comes from the anterior division of the obturator. ADDUCTOR This triangular muscle lies between the gracilis LONGUS. and the pectineus, and arises by a round tendon from the front of the body of the os pubis below the crest. As it descends, the muscle becomes broader, and passing downwards, outwards, and backwards, is inserted by a broad aponeurosis into the middle third of the inner margin of the linea aspera of the femur. It forms with the sartorius the triangular space called Scarpa's triangle, above described. It rests upon the adductor brevis and magnus, the profunda vessels, and the anterior branches of the obturator vessels and nerve. It is supplied by the anterior division of the obturator nerve. This muscle lies on the same plane, but external to the adductor longus, from which it is separated by a slight interval, in which may be seen the adductor brevis and the anterior division of the obturator nerve. It arises from the liiiea ilio-pectinea, from the triangular surface of the os pubis in 630 COURSE AND RELATIONS OF THE FEMORAL ARTERY. front of the line, and from the fascial prolongation of Gimbernat's ligament covering the muscle; it passes downwards, outwards, and backwards, and is inserted into the upper part of the ridge leading from the lesser trochanter to the linea aspera. It lies upon the capsular ligament of the hip-joint, the adductor brevis, the ob- turator vessels and nerve, and the obturator externus. Its nerve comes from the anterior crural which runs under the femoral vessels to enter it close to its outer border ; sometimes also from the obturator, and the accessory obturator if present (p. 498). By separating the contiguous borders of the pectineus and the adductor longus, the adductor brevis is exposed with the anterior division of the obturator artery and nerve lying upon it. To obtain a complete view of it, the pectineus and adductor longus must be reflected from their origins and turned downwards. The obturator nerve supplies all the adductors. It leaves the pelvis through the upper part of the obturator foramen, and soon divides into an anterior and posterior branch : the anterior runs in front of the adductor brevis, and supplies the hip-joint, the adductor longus, the gracilis, and sometimes the adductor brevis and the pectineus ; the posterior runs behind the adductor brevis, and supplies it as well as the obturator externus, the adductor magnus,, and the knee-joint. The student should now, before the parts are disturbed, examine the femoral artery as it passes down along the centre of Scarpa's triangle : its further course will be described later on, as well as the branches which come off from it. COUBSE AND ^e f emora l artery is a continuation of the EELATIONS or external iliac. Passing beneath the crural arch THE FEMORAL a t a point midway between the spine of the ilium and the symphysis pubis, it descends along the front and inner side of the thigh. At the junction of the upper two-thirds with the lower third of the thigh, it passes through an opening in the tendon of the adductor magnus, and, entering the ham, takes the name of popliteal. A line drawn from the point indicated of the crural arch to the adductor tubercle on the internal condyle corresponds with the course of the artery. Its distance from the surface increases as it descends. Immediately under, and for ADDUCTOR MUSCLES. 631 a short distance below the crural arch, it is supported by the inner border of the psoas ; lower down it runs in front of the pectineus, but separated from it by the profunda vessels ; still lower down, it lies upon the adductor longus, and then upon the adductor magnus.. That part of the artery which extends from the crural arch to- the giving off of the profunda, is called the common femoral artery ; its continuation beyond the profunda is termed the superficial femoral ; and it is the latter vessel which is ligatured for aneurism of the popliteal artery. In the upper third of the thigh, the artery is situated in Scarpa's triangle, and is comparatively superficial, having in front the skin, superficial fascia and fat, inguinal glands, deep fascia, the fascia lata, the crural branch of the genito-crural nerve, and the sheath of the femoral vessels. About the middle third it is more deeply seated, and is covered in addition by the sartorius ; and lower down by a tendinous aponeurosis, which stretches from the adductor longus and magnus over to the vastus internus. This, which forms part of Hunter's canal, will be examined presently. The femoral artery in Scarpa's triangle lies upon the psoas, the two branches of the anterior crural nerve to the pectineus, the pro- funda vein, and the pectineus ; to its outer side it has the anterior crural nerve (separated from it by a few fibres of the ilip-psoas)^ the profunda artery, and the long saphena nerve ; to its inner side it has the femoral vein. ADDUCTOR This muscle arises from the front surface of the BREVIS. body of the os pubis below the spine, and from it& descending ramus for about an inch, between the gracilis and the obturator externus ; it widens as it descends outwards and back- wards, and is inserted behind the pectineus into the whole length of the ridge leading from the lesser trochanter to the linea aspera. Behind, it rests upon the posterior division of the obturator vessels and nerve, and the adductor magnus. Its nerve is derived from the obturator. By reflecting it from its origin, the following muscle is exposed. 1 1 Beneath the adductor brevis, and running parallel with the upper border of the adductor magnus, is seen the obturator externus. But the description of this muscle is deferred till the dissection of the external rotators of the thigh. 632 ADDUCTOR MUSCLES. ADDUCTOR This muscle arises from the lower part of the MAGNUS. descending ramus of the os pubis between the adductor brevis and obturator externus, from the margin of the ascending ramus of the ischium, and from the lower and anterior part of the tuberosity of the ischium. Its fibres spread out, and are inserted, behind the other adductors, into the lower part of the linea quadrati, into the ridge leading from the great trochanter to the linea aspera, also into the whole length of the linea aspera, and the ridge leading from it to the inner condyle ; while those fibres which arise from the tuberosity of the ischium pass vertically down- wards, and are inserted by a rounded tendon into the adductor tubercle on the inner condyle of the femur. Between the muscular fibres of the middle and lower thirds of the insertion of this muscle, the femoral artery passes to the back of the thigh. The upper fibres pass transversely outwards to their insertion, while the lower fibres descend nearly vertically. In front of the muscle are, the adductor longus and brevis, the vastus internus, the obturator nerve and artery, and the profunda artery ; above it, are the internal cir- cumflex artery, the obturator externus, and the quadratus femoris ; behind it, the biceps, semi-tendinosus and semi-membranosus, the great sciatic nerve, and the gluteus maximus. Its nerve comes from the posterior division of the obturator and the great sciatic. Observe that all the adductor muscles are inserted into the femur by flat tendons more or less connected. About the junction of the upper two-thirds with the lower third of the thigh, the femoral artery passes through an oval opening in the tendon of the adductor magnus. PSOAS MAGNUS These muscles have been fully described in the AND ILIACUS. dissection of the abdomen (p. 488). TENSOR FASCIA This muscle is situated at the upper and outer FEMORIS. p ar ^ o f the thigh. It arises from the anterior part of the external lip of the crest of the ilium, and from the surface below the anterior superior spine. It descends with a slight inclination backwards, and is inserted, at the junction of the upper with the middle third of the thigh, between two layers of the strong aponeurosis, generally described as part of the fascia lata, which is continued downwards to the head of the tibia, and is EXTENSOR MUSCLES. 633 called the ilio-tibial band (p, 616). l Its chief use is to fix the pelvis steadily on the thigh, and to rotate the thigh inwards ; in this last .action it co-operates with the anterior fibres of the gluteus medius, with which it is almost inseparably connected. Anyone may con- vince himself of this by placing his hand on the hip, and rotating the thigh inwards. Both these muscles are supplied by the same nerve the superior gluteal. To form an adequate idea of the strength, extent, and connec- tions of the aponeurosis on the outer side of the thigh, it should be separated from the vastus externus muscle upon which it lies. There is no difficulty in doing so, for it is united to the muscle by an abundance of loose connective tissue. 2 With a little persever- ance the aponeurosis can be traced to the linea aspera, the head of the tibia, and the fibula, completely protecting the outer side of the knee-joint. EXTENSOB ^ ie P ower ftd fleshy muscles occupying the front MUSCLES OB of the thigh, and situated between the tensor QUADBICEPS fasciae on the outer side, and the adductors on the XTENSOB. inner, are the extensors of the leg. One of them the rectus arises from the pelvis ; the other the triceps arises from the shaft of the thigh-bone by three portions, called, re- spectively, the crttreus, the vastus internus, and externus. All are .supplied by the anterior crural nerve. To see the origins of the rectus femoris, dissect between the origin of the sartorius and the tensor fascise ; in doing so, avoid injuring the branches of the external circumflex artery. R, ECTUS This bipenniform muscle arises from the pelvis FEMOBIS. by two strong tendons, which soon unite at an acute angle : one the straight tendon is round, and arises from the anterior inferior spine of the ilium ; the other the reflected tendon is flat, and comes from the rough surface of the ilium, just above the acetabulum. The muscle descends along the front of the 1 The deeper of these two layers runs up to be strongly connected with the tendon of the rectus and the front of the capsule of the hip-joint. 2 When this tissue becomes the seat of suppuration, the pus is apt to extend .all down the outside of the thigh, not being able to make its way to the surface by reason of the dense fascia. 634 EXTENSOR. MUSCLES. thigh, and is inserted into the common extensor tendon, which will be presently examined. The structure of this muscle is remark- able. A tendon runs down the centre, and the muscular fibres are inserted on either side of it, like the vane on the shaft of a feather. Notice also that the surface of the upper part of the rectus is apoiieurotic in front and muscular behind, while the reverse is seen at the lower part not far from its insertion. Its nerve comes from the anterior crural. 1 TRICEPS Ex- This mass of muscle invests like a cloak the TEXSOK. greater part of the front and sides of the shaft of the femur ; therefore, the whole of it cannot be seen without com- pletely dissecting the thigh. It consists of an outer, middle, and inner portion, called, respectively, the vastus externus, the crureus, and the vastus internus. The vastus externus arises by a strong glistening aponeurosis from the outer side of the base of the great trochanter, from the upper third of the anterior intertrochanteric ridge, from the rough line leading from the greater trochanter to the linea aspera external to the gluteus maximus, from the outer lip of the linea aspera nearly down to the external condyle, and also slightly from the external intermuscular septum. From this origin the fibres pass downwards,, forwards, and inwards, and end in a flattened tendon, which is. inserted into the outer border of the patella to form part of the common extensor tendon to be presently described. The vastus internus and crureus should be described as one muscle, for they are inseparably connected. They arise conjointly by an aponeurosis commencing a short distance below the inner two-thirds of the anterior intertrochanteric ridge, from the upper three-fourths of the front and inner surfaces of the shaft of the femur, from the entire length of the inner lip of the linea aspera, and from the internal intermuscular septum. The outer bundle of" muscular fibres the crureus passes vertically downwards ; the inner the vastus internus descends forwards and outwards, and both are inserted by a common aponeurosis into the upper and the 1 An accurate description of this muscle is given by W. E. Williams, Journ. of Anat. and Phys., vol. xiii. p. 204, in which he states that the reflected head of the rectus is its real origin, as it alone exists in early foetal life. EXTENSOR MUSCLES. 635 inner borders of the patella. The muscular fibres of the vastus internus extend lower than those of the vastus externus. A few of the deeper fibres of the crureus are inserted into the fold of the synovial membrane of the knee-joint which rises above the patella. These are described as a distinct muscle, under the name of the sub-crureus. Their use is to raise the synovial mem- brane, so that it may not be injured by the play of the patella. Since the triceps is connected to the lower part of the shaft of the femur only by loose connective tissue, there is nothing to prevent the distension of the synovial membrane, in cases of inflammation, to the extent of several inches above the patella. COMMON The tendon of the rectus, gradually expanding^ EXTENSOR becomes connected on its under surface with the TENDON. tendon of the crureus, and on either side with that of the vasti, and is firmly fixed into the upper part and sides of the patella. From this bone the common extensor tendon the lifja- mentum patellce descends over the front of the knee-joint, and is inserted into the rough part of the tubercle of the tibia. Besides this, the lower fibres of the vasti terminate on a sheet-like tendon, which runs wide of the patella on either side, and is directly inserted into the sides of the head of the tibia and fibula, so that the knee is completely protected all round. The patella is a large sesamoid bone, interposed to facilitate the play of the tendon over the con- dyles of the femur : it not only materially protects the joint, but adds to the power of the extensor muscles, by increasing the angle at which the tendon is inserted into the tibia. To facilitate the play of the extensor tendon there are two bursae. One is placed between the ligamentuni patellae arid the smooth part of the tubercle of the tibia, the other between the crureus and the lower part of the femur. This last is of consider- able size. In early life it is, as a rule, distinct from the synovial membrane of the knee-joint ; but after a few years a wide commu- nication frequently exists between them. ACTION OF The extensor muscles of the thigh are among THE EXTENSOR the most powerful in the body. Great power of extending the knee is one of the essential con- ditions of the erect attitude. Without it, how could we rise from 636 BUKSA OVER THE PATELLA. the sitting position ? When erect, how could we walk, run, or spring ? The rectus, by taking origin from the pelvis, gains a double advantage : it acts upon two joints simultaneously, bending the thigh while it extends the knee, as when we advance the leg in walking ; it also contributes to balance the pelvis on the head of the thigh-bone, and thus prevents the body from falling backwards. We cannot have a better proof of the power of the extensor muscles than when the patella is broken by their sudden contraction an injury which sometimes happens when a man, slipping backwards, makes a violent effort to recover his balance. BUKSA OVER The skin over the patella is exceedingly loose, THE PATELLA. and in the subcutaneous tissue is a bursa of con- siderable size. Since this bursa is apt to enlarge and inflame in females who are in the habit of kneeling at their work, it is gener- ally called the housemaid's bursa. The bursa is not seated precisely over the patella, but extends some way down the ligamentum patellse ; indeed, in some cases it is entirely confined to this liga- ment. This corresponds with the position of the tumour which the bursa occasions when enlarged. Generally speaking, in subjects brought for dissection, the wall of the bursa is more or less thickened, and its interior intersected by numerous fibrous cords, remnants of the original cellular structure altered by long-continued friction. Again, the wall of the bursa does not always form a complete sac ; sometimes there is a wide opening in it ; this explains the rapidity with which inflammation, in some cases, extends from the bursa into the surrounding areolar tissue. Below the bursa is a layer of fascia lata, and under this is a network of arteries. The immediate covering of the bone, or what may be called its periosteum, is a strong expansion derived from the extensor tendon. This is interesting for the following reason : in ordinary fractures of the patella from muscular action the ten- dinous expansion over it is torn also ; the ends of the bone gape widely, and never unite except by ligament. But in fractures from direct mechanical violence, the tendinous expansion, being entire, maintains the fragments in apposition, so that there is commonly a bony union. The remaining part of the femoral artery can now be examined after the sartorius has been cut through near its middle, and both HUNTER'S CANAL. 637 ends reflected. This part of its course corresponds to the middle third of the thigh, and is contained in Hunter's canal. FEMORAL ^ n f ron ^ of the artery are the skin, superficial ARTERY IN and deep fascias, the long saphena vein, the sarto- HUNTER'S CANAL. r i u g } the long saphenous nerve, and the aponeurotic layer forming the anterior boundary of Hunter's canal : to its outer side, are the femoral vein and the vastus internus ; to its inner side> are the adductor longus, the adductor magnus and the sartorius ; Iteliind it, are the adductor longus, the femoral vein, and the ad- ductor magnus. The artery and vein lie close together, and are enclosed in a common sheath, HUNTER'S In the middle third of the thigh, the femoral CANAL. artery is contained in a tendinous canal l beneath the sartorius, called Hunter's canal. This canal at its upper part is rather indistinct ; but it gradually becomes stronger towards the opening in the tendon FIG. 150. of the adductor magnus. Its boundaries are formed by the tendons of the muscles be- tween which the artery runs. On the inner side are the tendons of the adductor longus and magnus ; on the outer side is the tendon of the vastus internus ; in front the canal SECTION THROUGH is completed by an aponeurotic expansion HUNTER'S CANAL. thrown obliquely across from the adductors i. vastus internus. , j. i. i .c i K A 2. Adductor longus. to the vastus internus, as shown in fig. 150. 3> Apraeurwis thrown acnw. In a horizontal section the canal appears trian- gular. The adaptation of this shape to the exigencies of the case is manifest when we reflect that the muscles keep the sides of the triangle always tight, and thereby prevent any compression of the vessels. Hunter's canal contains not only the femoral artery and vein, but the internal saphenous nerve. The vein lies behind and to the outer side ; the nerve crosses over the artery from the outer to the inner side. 1 Called Hunter's canal, because it was in this part of its course that John Hunter first tied the femoral artery for aneurism of the popliteal, in St. George's Hospital, A.D. 1785. The particulars of this interesting case are published in the Trans, for the Improvement of Med. and Chir. Knowledge. 638 BRANCHES OF THE FEMORAL ARTERY. A ligature can be placed around the artery, in the upper third of the thigh, with comparative facility ; not so easily in the middle third. The artery is tied for an aneurism of the popliteal, just where the sartorius begins to overlap it, for three reasons : (1) it is more accessible ; (2) the coats of the artery at this distance are less likely to be diseased ; (3) the origin of the profunda is suffi- ciently far off to admit of the formation of a clot. An incision, beginning about three inches below the crural arch, should be made about three inches long over the line of the artery. The muscular fascia should be divided on a director to the same extent. Then, by gently drawing aside the inner border of the sartorius, the artery is seen enclosed in its sheath with the vein. An open- ing should be made into the sheath, which must be carefully separated from the artery to an extent sufficient to allow the passage of the aneurismal needle. The needle should be turned round the artery from within outwards, great care being taken not to injure the vein. The nerves to be avoided are the long saphenous, which runs along the outer side of the artery, and the internal cutaneous which crosses obliquely over it. Having already traced the superficial branches of the femoral artery in the groin, namely, the superficial epigastric, the external pudic, and the superficial circumflexa ilii (p. 611), we pass on now to the profunda. PKOFUNDA The profunda femoris, the chief branch of the AKTEBY AND femoral, is the proper nutrient artery of the BRANCHES. muscles of the thigh, and is considered as a division, rather than a branch, of the common femoral artery. It is given off from the outer and back part of the femoral, from one and a half to three inches below the crural arch, lying to the outer side of the artery for about two inches, and then runs down behind the femoral till it reaches the tendon of the adductor longus ; here the profunda passes behind the adductor, and piercing the adductor magnus as a small branch, is finally lost in the hamstring muscles. 1 1 The point at which the profunda is given off below the crural arch varies very much even in the two limbs of the same body. We have measured it in 19 bodies, or 38 femoral arteries. It varied from half an inch to 3 inches. In 22 cases the profunda came off between H and 2 inches ; in 9 this distance was exceeded ; in 7 this distance was less. BRANCHES OF THE PROFUNDA FEMORIS. 639 In most subjects the profunda, for a short distance after its origin, lies rather on the outer side of the femoral and on a deeper plane, on the iliacus : in this situation it might be mistaken for the super- ficial femoral itself indeed, such an error has occurred in practice. It soon, however, gets behind the femoral, and lies upon the pecti- neus, the adductor brevis and magnus ; it is separated from the femoral artery, at first, by their corresponding veins ; lower down, by the adductor longus. The branches of the profunda generally arise in the following order : (1) the internal circumflex ; (2) the external circumflex ; (3) the perforating. The internal circumflex is given off from the inner and back part of the profunda, and then sinks deeply into the thigh between the psoas and pectineus. At the lower border of the obturator externus it divides into two branches : one the ascending supplies the muscles in its neighbourhood, namely, the pectineus, psoas, adductors, gracilis, and obturator externus, anastomosing with the obturator artery ; the other the descending passes down to behind the adductor brevis to supply it and the adductor magnus ; the continuation of the artery called the transverse, will be seen in the dissection of the back of the thigh, between the adductor magnus and the quadratus femoris. This latter sometimes gives off a small branch to the hip-joint, which runs through the notch in the acetabulum to the ligamentum teres ; it afterwards inosculates with the sciatic, the external circumflex and superior perforating arteries, forming the crucial anastomosis. The external circumflex artery comes off from the outer side of the profunda, runs transversely outwards beneath the sartorius and rectus between the branches of the anterior crural nerve, and then subdivides into three sets of branches, ascending, transverse, and descending. The ascending run up to the outer side of the ilium, beneath the tensor fascife and gluteus medius, supply these muscles, and inosculate with the termi- nal branches of the gluteal and deep circumflex iliac arteries. The transverse pass directly outwards over the crureus, then enter the vastus externus, and get between the muscle and the femur. They inosculate with the sciatic, the internal circumflex, the gluteal, and the perforating arteries. The descending, two or more in number, of considerable size, run down between the rectus and crureus, and supply both these muscles : one branch, larger than the rest, runs down in the substance 640 BKANCHES OF THE PROFUNDA FEMORIS. of the vastus externus, along with the nerve to that muscle, and inos- culates with the superior articular branches of the popliteal. The perforating branches of the profunda are so named because they pass through the adductors to supply the hamstring muscles. There are generally four. The first passes between the pectineus and the adductor brevis, then pierces the adductor magnus, and communicates with the FIG. 151. 1. Crural arch. 2. Internal iliac. 3. Superficial femoral. 4. Profuuda. 5. Internal circumflex. 6. External circumflex. 7. First perforating. 8. Second ditto. 9. Third ditto. 10. Gluteal. 11. Obturator. 12. Sciatic. 13. A.nastomotica mag PLAN OF THE INOSCULATIONS OF THE CIRCUMFLEX ARTERIES. internal and external circumflex, the sciatic and second perforating arteries. The second, the largest, passes through the tendons of the adductor brevis and magnus, divides into an ascending and a descending branch, which anastomose respectively with the first and third perfora- ting arteries. It usually furnishes the nutrient artery of the femur. The third, given off below the adductor brevis, passes through the tendon of the adductor magnus. The fourth, or terminal branch, passes ARTERIAL INOSCULATIONS. 641 through the tendon of the adductor magnus, and supplies the hamstring muscles, and inosculates with the perforating and articular arteries. They not only supply the hamstring muscles namely, the biceps, semi- tendinosus, and semimembranosus but, the vastus externus, and even the gluteus maximus. The perforating arteries inosculate with one another, with the internal and external circumflex, and with the sciatic arteries. Muscular branches, from four to seven in number, are distributed by the superficial femoral to the sartorius and the vastus internus. The anastomotica magna arises from the femoral artery just before it leaves its tendinous canal. It emerges through the canal, and runs in front of the tendon of the adductor magnus, in company with the long saphenous nerve to the inner side of the knee. Here it divides into two branches : one, the superficial, accompanies the saphenous nerve beneath the sartorius, and is subsequently distri- buted to the skin ; the other, the deep, enters the vastus internus, ramifies over the capsule, and communicates with the other articular arteries. 1 ARTERIAL If the common femoral were tied above the INOSCULATIONS. origin of the profunda, how would the circulation be carried on ? The gluteal, the ilio-lumbar, and the circumflex iliac communicate with the ascending branch of the external cir- cumflex ; the obturator and sciatic communicate with the internal circumflex (see fig. 151) ; the arteria comes nervi ischiatici com- municates with branches from the lower perforating and popliteal arteries. Again, how is the circulation maintained when the super- ficial femoral is tied below the profunda ? The descending branch of the external circumflex and the perforating branches of the pro- funda communicate with the articular branches of the popliteal and the tibial recurrent. 2 ANTERIOR T ne anterior crural nerve is the largest branch CRURAL NERVE. of the lumbar plexus (p. 498). It comes from the 1 In its course down the thigh the femoral artery gives off a branch of con- siderable size for the supply of the vastus internus. We may trace this branch through the substance of the vastus down to the patella, where it joins the network of vessels on the surface of that bone. 2 Read the account of the dissection of an aneurismal limb by Sir A. Cooper, Med. Chir. Trans, vol. ii., 1811. T T 642 ANTERIOR CRURAL NERVE. third and fourth lumbar nerves, also by a small fasciculus from the second. It passes beneath the crural arch, lying in the groove between the iliacus and psoas, about a quarter of an inch to the outer side of the artery, and soon divides into branches, some of which are cutaneous, but the greater number supply the extensor muscles of the thigh. The cutaneous branches, already described (p. 614), and the long saphenous 'nerve, are given off from the superficial part of the trunk ; the muscular from the deep part. The long saphenous nerve, the largest of the cutaneous branches,, descends close to the outer side of the femoral artery, and enters the tendinous canal with it in the middle third of the thigh. In the canal it crosses over the artery to its inner side. The nerve leaves the artery just before it becomes popliteal, and then runs in company with the anastomotica magna to the inner side of the knee, where it becomes superficial, between the gracilis and the sartorius. In the middle third of the thigh it gives off a small branch which communicates beneath the fascia lata with the internal cutaneous and obturator nerves ; and lower down another branch is distributed to the skin over the patella. Its further relations will be seen in the dissection of the leg and foot. The imiscular branches are to be traced to the sartorius, rectus, crureus, and subcrureus ; the branch to the vastus externus accompanies the descending branch of the external circumflex artery, and sends a filament to the knee-joint ; that to the vastus internus runs parallel with, but external to, the long saphenous nerve, and supplies filaments to the knee-joint. One branch, often two, passes under the femoral artery and vein to enter the anterior surface of the pectineus. The obturator nerve, also a branch of the lumbar plexus, arising from the second, third, and fourth lumbar nerves (p. 498), supplies the adductor muscles. It enters the thigh through the upper part of the obturator foramen above the corresponding artery, and im- mediately divides into two branches, of which one passes in front of, the other behind, the adductor brevis. The anterior branch subdivides for the supply of the gracilis, the adductor longus, and sometimes the adductor brevis and pectineus ; it, moreover, sends a filament to the hip-joint ; another to the femoral artery ; and a third forms a plexiform communication at the lower border of the adductor longus with the internal cutaneous and long saphenous nerves. The posterior branch supplies the obturator externus, the DISSECTION OF THE FRONT OF THE LEG. 643 adductor brevis and magnus. In some bodies you can trace a fila- ment of this nerve through the notch of the acetabulum into the hip-joint, and another, which runs near the popliteal artery, into the back part of the knee-joint. We have frequently seen cutaneous branches from the obturator on the inner side of the thigh. This is interesting practically, since it helps to explain the pain often felt on the inner side of the knee in disease of the hip-joint. The accessory obturator nerve, when present, comes either from the obturator nerve or from the third and fourth lumbar nerves. Descending, it runs between the horizontal ramus of the os pubis and the pectineus, and supplies a branch to this muscle, also a fila- ment of communication to the anterior branch of the obturator, and a third branch to the hip-joint. The obturator artery, after passing through the foramen, divides into two branches, an internal and an external, which form a circle round the obturator membrane. These supply the external obtu- rator and adductors of the thigh, and inosculate with the internal circumflex artery (p. 640). The latter branch sometimes gives off the small artery to the ligamentum teres of the hip-joint. DISSECTION OF THE FBONT OF THE LEG. SURFACE About an inch below the patella is the promi- MABKING. n ent tubercle of the tibia, to which the ligamentum patellae is attached ; on each side of this is a depression, filled with more or less fat. About the same distance below the outer tubero- sity of the tibia is the head of the fibula, situated far back, and to it can be traced the tense tendon of the biceps. The crest of the tibia- is easily felt in front, commencing above at the outer tuberosity r and passing down nearly vertically, gradually inclining to the inner side so that it is continuous below with the front of the internal malleolus. Internal to the crest is the subcutaneous internal surface of the tibia, and externally is the interval between the tibia and the fibula, which is filled up by the extensor muscles. The lower fourth of the fibula is subcutaneous, ending in a well-marked prominence, the external malleolus, which, it should be observed, T T 2 644 CUTANEOUS VEINS AND NERVES OF THE LEG. descends lower than the internal malleolus. The student should notice well the tendons which surround the ankle-joint, which are easily recognisable under the skin : thus, behind, the tendo Achillis stands out prominently, having a deep depression on each side ; on the outer side, the tendons of the peronei, longus and brevis, are felt, the latter being the anterior. Running round the inner ankle we can only feel the tibialis posticus close to the tibia, and next to it the flexor longus digitorum ; in front of the ankle, but bound down by the anterior annular ligament, can be felt, from within outwards, the strong tendon of the tibialis anticus, the extensor proprius hallucis, and the long extensor of the toes with the peroneus tertius. The foot should be turned inwards, and fixed in this position. An incision must be made from the knee, down the front of the leg, over the ankle, along the top of the foot to the great toe ; a second, at right angles to the first, on either side of the ankle ; a third, across the bases of the toes. Reflect the skin from the front and sides of the leg and foot. CUTANEOUS Having traced the internal saphena vein (p. 613) VEINS AND to the inner side of the knee, follow it down the NEEVES. inner side of the leg, in front of the inner ankle l to the dorsum of the foot. On the dorsum of the foot notice that the principal veins form an arch, with the convexity forwards, as on the back of the hand. This arch receives the veins from the toes. From the inner side of the arch the internal saphena originates ; from the outer side, the external saphena. The latter vein commences on the outer side of the arch on the dorsum, runs behind the external ankle, along the outer border of the tendo Achillis up the back of the calf of the leg, between the two heads of the gastrocnemius, and finally pierces the deep fascia at the lower part of the popliteal space, to join the popliteal vein. The external saphenous nerve accompanies this vein, as the long saphenous nerve does the internal saphena vein. LONG SAPHE- The skin on the inner side of the leg is supplied NOUS NERVE. by the long or internal saphenous nerve (p. 642). 1 The French commonly bleed from the internal saphena vein as it crosses over the inner ankle, this being a convenient and safe place for venesection. MUSCULAR FASCIA AND ANNULAK LIGAMENTS. 645 It becomes subcutaneous on the inner side of the knee, between the gracilis and sartorius. Here it meets the saphena vein, and ac- companies it down the leg, distributing its branches on either side, till it is finally lost on the inner side of the foot and the great toe. The largest branch curves round the inner side of the knee, just below the patella, to supply the skin in this situation. It pierces the sartorius close to the knee, and forms with branches from the internal, middle, and external cutaneous nerves, the plexus patellce. The internal cutaneous nerve supplies the skin of the upper and inner aspect of the leg, and joins the internal saphenous nerve. The skin on the front and outer parts of the upper half of the leg is supplied by cutaneous brandies from the external popliteal or peroneal nerve ; the skin of the lower half by its external cutaneous branch, as follows : EXTERNAL Cu- This branch of the peroneal nerve comes through TANEOUS BBANCH the fascia about the lower third of the outer side OF THE PERONEAL o f the leg ; and, descending over the front of the ankle, divides into two. Trace them and you will find that the inner and smaller supplies the inner side of the great toe, and the contiguous sides of the second and third toes ; towards its termination it communicates with the long saphenous and an- terior tibial nerves. The outer distributes branches to the outer side of the third toe, both sides of the fourth, and the inner side of the fifth toe, and joins the short or external saphenous nerve. The outside of the little toe is supplied by the external saphenous nerve, which runs behind the outer ankle with the corresponding vein. The contiguous sides of the great and second toes are supplied by the termination of the anterior tibial nerve. 1 MUSCULAR This is remarkably thick and strong. Besides FASCIA AND AN- its general purpose of forming sheaths for the NULARLiGA- muscles, and straps for the tendons, it gives origin, as in the forearm, to muscular fibres; so- that it cannot be removed near the knee without leaving the muscles ragged. The fascia, continuous above with the fascia lata, 1 Such is the most common distribution of the nerves to the upper surface of the toes. But deviations from this arrangement are frequent. 646 THE ANNULAR LIGAMENTS. is attached to the head of the tibia and the fibula : it is connected on the inner side with the expanded tendons of the sartorius, gracilis, and semi-tendinosus ; on the outer side with that of the biceps : consequently, when these muscles act, it is rendered tense. Following it down the leg, you find that it is attached to the edge of the tibia, and that it becomes stronger as it approaches the ankle, to form the ligaments which confine the tendons in this situation. Of these ligaments, called annular, there are three, as follows : a. The anterior annular ligament extends obliquely across the front of the ankle-joint, and confines the extensor tendons of the ankle and toes. It consists of two converging straps one oblique, the other horizontal, which join, and are continued on as a common band, like the letter H< placed transversely : the upper or oblique binds down the tendons in front of the lower end of the tibia ; the lower or oblique the tendons which lie over the tarsus. The common band is attached to the external malleolus, cuboid, and os calcis ; it is continued horizontally inwards for a short distance, and in front of the ankle splits into two fasciculi : the upper or oblique -ascends to be attached to the tibia ; the lower or horizontal passes inwards to be attached to the internal malleolus, the scaphoid, and the internal cuneiform. Beneath the upper fasciculus, enclosed in two synovial sheaths, run the tibialis anticus on the inner side, and the extensor longus digitorum and peroneus tertius on the outer side ; the extensor proprius hallucis and the anterior tibial vessels lying behind the ligament, but not having any synovial sheath. Beneath the lower fasciculus are three synovial sheaths an inner one for the tibialis anticus, a middle one for the extensor proprius hallucis, and an outer one for the extensor longus digi- torum and peroneus tertius. It is the strain of this ligament which occasions the pain in sprains of the ankle. b. The external annular ligament extends from the outer malleolus to the os calcis, and confines the tendons of the peronei muscles, which are enclosed in a common synovial sheath. c. The internal annular ligament is a strong fasciculus of ill- defined fibrous tissue which extends from the inner malleolus to the os calcis, where it becomes continuous with the plantar fascia MUSCLES ON THE FRONT OF THE LEG. 647 and the tendinous origin of the abductor hallucis. It binds down the flexor tendons of the foot and toes, and, as these pass round the inner ankle, it forms three compartments, each lined with a separate synovial sheath one each for the tibialis posticus, the flexor longus digitorum, and the flexor longus hallucis. Remove the fascia, leaving enough of the annular ligaments to retain the tendons in their places. MUSCLES ON The muscles on the front of the leg are : (1) THE FRONT OF the tibialis anticus ; (2) the extensor longus digi- THE LEG. torum and peroneus tertius ; (3) the extensor proprius hallucis. TIBIAUS The tibialis anticus arises by fleshy fibres from ANTICUS. the external tuberosity and the upper two-thirds of the outer side of the shaft of the tibia, from the interosseous membrane, from the fascia which covers it, and from the inter- muscular septum which separates it from the extensor longus digitorum. About the lower third of the leg the fibres terminate on a strong flat tendon, which descends obliquely over the front of the ankle, through the innermost compartment of the anterior annular ligament, to the inner side of the foot ; here it becomes a little broader, and is inserted into the internal cuneiform bone and the base of the metatarsal bone of the great toe. The synovial mem- brane, which lines the sheath of the tendon beneath the anterior annular ligament, accompanies it to within an inch of its insertion ; consequently, it is opened when the tendon is divided for club-foot. The action of this muscle is to draw the foot upwards and inwards. 1 When the foot is the fixed point, it assists in balancing the body at the ankle. Its nerve comes from the anterior tibial. EXTENSOR This muscle lies along the fibular side of the LONGUS DIGI- preceding. It arises from the external tuberosity -TORUM. O f t ne tibia, from the upper three-fourths of the anterior surface of the shaft of the fibula, from the interosseous membrane, from the fascia of the leg and the intermuscular septa. Its fibres terminate in a penniform manner upon a long tendon, .situated on the inner side of the muscle : this tendon descends in 1 It is generally necessary to divide this tendon in the distortion of the foot inwards called talipes varus. 648 MUSCLES ON THE FRONT OF THE LEG. front of the ankle and divides into four slips, which pass to the four outer toes. They diverge from each other, and are inserted into the toes thus : On the base of the first phalanx, each tendon (except that of the little toe) is joined on its outer side by the cor- responding tendon of the extensor brevis, and a little further on by a fibrous expansion from the interosseous and lumbrical muscles. The united tendons then expand, cover the dorsal surface of the first phalanx, and at the articulation between this and the second phalanx, split into three fasciculi ; the middle one is inserted into- the base of the second phalanx, the two lateral ones, running on and reuniting, are inserted into the base of the third phalanx. Its nerve comes from the anterior tibial. Immediately below the ankle the anterior annular ligament forms a pulley through which the tendon of this muscle plays. It is like a sling, of which the two ends are attached to the os calcis, while the loop serves to confine the tendon. The play of the ten- don is facilitated by a synovial membrane, which is prolonged for a short distance along each of its four divisions. Besides its chief action, this muscle extends the ankle-joint. 1 PEKONEUS This is a portion of the preceding. Its fibres TEETIUS. arise from the lower fourth of the anterior surface of the shaft of the fibula, the interosseous membrane, and the intermuscular septum between it and the peroneus brevis, and ter- minate on their tendon like barbs on a quill. The tendon passes through the same synovial pulley with the long extensor of the toes, and, expanding considerably, is inserted into the tarsal end of the metatarsal bone of the little toe. It is not always present. It is supplied by a branch of the anterior tibial nerve. This muscle extends the foot and draws the outer border of the foot upwards. The peroneus tertius and the tibialis anticus are important muscles in progression. They raise the toes and foot from the ground. Those who have lost the use of these muscles are obliged to drag the foot along the ground, or to swing the entire limb outwards in walking. 1 There is often a large bursa between the tendon of the extensor longus digi- torum and the outer end of the astragalus. This bursa sometimes communicates with the oint of the head of the astragalus. COURSE AND RELATIONS OF THE ANTERIOR TIBIAL ARTERY. 649* EXTENSOR This muscle lies partly concealed between the PEOPKIUS tibialis anticus and the extensor longus digitorum.. HALLUCIS. j^ ar { ses from rather more than the middle third of the anterior surface of the fibula, and from the interosseous membrane. The fibres terminate in a penniform manner on the tendon, which runs over the ankle, between the tendons of the tibialis anticus and the extensor longus digitorum, along the top of the foot to the great toe, where it is inserted into the base of the last phalanx. It has a special pulley beneath the horizontal portion of the anterior annular ligament, lined by a synovial mem- brane, which accompanies it as far as the metatarsal bone of the great toe. It is supplied by the anterior tibial, a branch of the peroneal nerve. Now examine the course, relations, and branches of the ante- rior tibial artery. Since it lies deeply between the muscles, it is necessary to separate them from each other : this is easily done by proceeding from the ankle towards the knee. COURSE AND ^e an t er i r tibial artery is one of the two KELATIONS OF THE branches into which the popliteal divides at the ANTERIOR TIBIAL lower border of the popliteus. It comes at first ARTERY. horizontally forward about 1 inch below the head of the fibula, between the two heads of the tibialis posticus, above the interosseous membrane, and then descends, lying in rather more than the first half of its course upon the interosseous membrane, afterwards along the front of the tibia. It runs be- neath the anterior annular ligament over the front of the ankle, where it takes the name of the dorsal artery of the foot. Thus, a line drawn from the head of the fibula to the interval between the first and second metatarsal bones would nearly indicate its course. In the upper third of the leg it lies deeply between the tibialis anticus and the extensor longus digitorum ; in the lower two-thirds, between the tibialis anticus and the extensor proprius hallucis. In front of the ankle the artery is crossed by the-extensor proprius hallucis, and lies between the tendon of this muscle and the inner tendon of the extensor longus digitorum. The artery is accompanied by the anterior tibial nerve (a, branch of the peroneal), which runs for some distance upon its 650 ANTERIOR TIBIAL ARTERY. fibular side, then in front of it, and lower down is again situated on its outer side. It is accompanied by two veins, one on each side, which communicate at intervals by cross branches. The branches of the anterior tibial are as follows : a. The recurrent tibial branch ascends close by the outer side of the head of the tibia, through the tibialis anticus, to the front of the knee- joint, where it inosculates with the other articular arteries derived from the popliteal, and with the anastomotica magna. b. MiLscular branches, in its course down the leg, and others which pierce the interosseous membrane, and communicate posteriorly with branches of the posterior tibial and peroneal arteries. c. The malleolar branches, external and internal, ramify over the ankle : the external, descending beneath the tendon of the extensor longus digitorum and peroneus tertius, ramifies on the external malleolus, inosculating with the anterior peroneal and the tarsal arteries ; the internal passes beneath the extensor proprius hallucis and the tibialis anticus, and anastomoses with the posterior tibial, with its internal calcanean branch, and with the internal plantar artery. They supply the joint, the articular ends of the bones, and the sheaths of the tendons around them. EXTENSOR This muscle is situated on the dorsum of the BEEVIS DIGI- foot, beneath the long extensor tendons of the TOEUM. toes. It arises from the outer part of the os calcis, from the external calcaneo-astragaloid ligament, and from the anterior annular ligament. The fibres run obliquely over the foot, and terminate in four tendons, which pass forwards to the four inner toes. The inner one and the largest is inserted by an expanded tendon into the base of the first phalanx of the great toe; the others join the fibular side of the long extensor tendons to be inserted with them into the second and ungual phalanges. The tendon to the great toe crosses over the dorsal artery of the foot. It is supplied by a branch of the anterior tibial nerve. D OKSAL This artery, the continuation of the anterior ABTEKY OF tibial, runs over the instep to the back of the . THE FOOT. interval between the first and second metatarsal bones, where it divides into two branches one, the dorsalis hal- lucis, runs along the dorsal aspect and the first interosseous space ; the other, the communicating, sinks into the sole and joins the DORSAL ARTERY OF THE FOOT. 651 deep plantar arch. On the dorsum of the foot the artery lies upon the astragalus, the scaphoid, and the internal cuneiform bones, .separated however from them by their dorsal ligaments ; in front, the artery has the skin, superficial and deep fascise, the venous arch across the dorsum, and the innermost tendon of the short extensor of the toes ; on its outer side, it has the extensor longus digi- torum and the anterior tibial nerve ; on its inner side, the extensor proprius hallucis. The dorsal artery gives off the following branches : a. The tarsal branch arises near the scaphoid bone, passes outwards in an arched direction beneath the extensor brevis digitorum towards the outside of the foot, supplies the bones and joints of the tarsus, and inosculates with the external malleolar, the peroneal, the metatarsal, .and the external plantar arteries. 6. The metatarsal branch generally runs towards the outside of the foot, in front of and parallel with the tarsal artery, beneath the short extensor tendons, near the bases of the metatarsal bones, and gives off the three outer dorsal interosseous arteries. These pass forwards over the corresponding interosseous muscles, supply them, and then sub- divide to supply the contiguous sides of the upper surfaces of the toes. The outer interosseous branch, in addition to giving off a branch to the fourth interosseous space, gives off a small branch to the outer side of the little toe. They receive, at the back of each interosseous space, the posterior perforating branches of the plantar arch, and at the front of each interosseous space they receive the anterior perforating branches from the plantar digital arteries. c. The dorsalis halhicis is, strictly speaking, the artery of the first interosseous space. It is the continuation of the dorsal artery of the foot, after it has given off the communicating branch to the sole, and runs forwards to supply digital branches to the sides of the great toe, the inner side of the second toe. PEKONEI These muscles are situated on the outer side of MUSCLES. the fibula, and are named, respectively, peroneus longus and brevis. PERONEUS This arises from the head and the outer surface LONGUS. of the fibula along its upper two-thirds, from the deep fascia which covers it, and the intermuscular septa. The fibres terminate in a penniform manner upon a tendon, which runs 652 PERONEAL NERVE. with the peroneus brevis, in a groove behind the external malleolus,, then along the outer side of the os calcis, and, lastly, through a groove on the under surface of the os cuboides deep into the sole. It crosses the sole obliquely forwards and inwards, and is inserted into the tarsal end of the metatarsal bone of the great toe, and usually into the internal cuneiform bone. In its course through these several bony grooves the tendon is confined by a fibrous sheath, lined by a synovial membrane. In removing the meta- tarsal bone of the great toe, if possible, leave the attachment of this tendon, which is usually inserted by means of a sesamoid bone. Its nerve comes from the peroneal. PERONEUS This muscle lies beneath the preceding. It BREVIS. arises from the lower two-thirds of the outer sur- face of the fibula, internal to the preceding muscle, and from the intermuscular septa. It terminates on a tendon which runs be- hind the external malleolus, through the same sheath with the peroneus longus, then proceeds along the outside of the foot, and is inserted into the dorsal surface of the tarsal end of the metatarsal bone of the little toe. On the outside of the os calcis there is a ridge which separates the tendons of the peronei. Each has a dis- tinct sheath. The short tendon runs above, the long one below the ridge. Its nerve is from the musculo-cutaneous branch of the peroneal nerve. The action of the peronei is to raise the outer side of the foot. 1 ' This movement regulates the bearing of the foot in progression, so- as to throw the principal part of the weight on the ball of the great toe. Its action is well exemplified in skating. Again, supposing the fixed point to be at the foot, they tend to prevent the body from falling on the opposite side, as when we balance ourselves on one leg. PEBONEAL Near the inner side of the tendon of the biceps OB EXTEBNAL flexor of the leg, is a large nerve, the external POPLITEAL NERVE, popliteal or peroneal, a branch of the great sciatic. By reflecting the upper part of the peroneus longus, you will find that this nerve runs round the outer side of the fibula immediately 1 In distortion of the foot outwards, called talipes valgus, it is generally neces- sary to divide the tendons of the peronei. DISSECTION ' OF THE GLUTEAL REGION. 653 below its head, and, piercing the origin of the peroneus longus, divides into two main branches the anterior tibial and the rnus- culo-cutaneous nerves. It gives off several branches as follows : 1. Articular branches, two in number to the knee-joint, which pass in with the external articular arteries, and a third which accompanies the tibial recurrent artery. 2. Cutaneous branches, two or more, supply the skin on the back and outer aspect of the leg, and one, the communicans peronei, which joins the external saphenous to supply the dorsal aspect of the outer side of the little toe : this will be seen later on in the dissection of the back of the leg. 3. The anterior tibial, which accompanies the corresponding artery and supplies the muscles between which it runs namely, the tibialis anticus, extensor longus digitorum, extensor proprius hallucis, and peroneus tertius; also the extensor brevis digitorum. 4. The musculo-cutaneous (p. 645), which comes through the fascia between the peroneus longus and the extensor longus digitorum. 5. Branches, which supply the peronei, longus and brevis, muscles. If, then, the peroneal nerve were divided in the popliteal space, the result would be paralysis of the tibialis anticus, the extensors of the toes, long and short, and all the peronei. DISSECTION OF THE GLUTEAL EEGION. The body having been placed on its face, the pelvis is to be raised to such a height by blocks beneath it, that the lower ex- tremities hang down over the end of the table. Then rotate the thighs inwards as much as possible, and cross them. SURFACE The bony prominences are very marked and MASKING. prominent : they are, on the outer side, the great trochanter, and, on the inner, the posterior superior spine of the ilium, the spines of the sacral vertebrae, which are continued on to the coccyx. Between the latter bone and the great trochanter is the rounded tuberosity of the ischium, which in the erect position is covered by the gluteus maximus, but is uncovered by it when the femur is flexed. Notice a transverse curved fold of the skin extending 654 CUTANEOUS NERVES OF THE GLUTEAL REGION. from the coccyx to the base of the great trochanter, which does not, as it might be thought, correspond with the lower border of the glutens maximus, which is much lower. This fact is im- portant to bear in mind in operations for stretching the great sciatic nerve, for the relief of sciatica or other affections of the nerve or its branches. The buttock is convex towards its inner part, and in health presents on its outer side a hollow behind the great trochanter, which usually becomes lost in hip-joint disease. The back of the thigh is convex, and, towards its lower part, it presents a flattening, corresponding to the lozenge-shaped hollow of the popliteal space, so that the tendons and muscles form- ing its boundaries can be easily distinguished. The incision through the skin should commence at the coccyx, and be continued in a semicircular direction along the crest of the ilium. Another incision should be made from the coccyx down- wards and outwards for about six inches below the great trochanter. In reflecting the skin, notice the thick cushion which the sub- cutaneous adipose tissue forms over the tuberosity of the ischium, and the peculiar manner in which the fat is enclosed in meshes formed by dense connective tissue. A large bursa is often formed between this cushion and the bone. CUTANEOUS These are derived from the following sources : NERVES. Branches from the posterior divisions of the first and second lumbar nerves descend over the crest of the ilium, near the origin of the erector spinge, to supply the skin over the gluteus maximus as far as the great trochanter (fig. 84, p. 369). Branches from the posterior branches of the three upper sacral nerves pass downwards and outwards to supply for a short dis- tance the integument over the sacrum and coccyx. The lateral branch of the twelfth dorsal nerve descends vertically over the crest of the ilium, near to its anterior part, and supplies the integument of the front of the gluteal region. The iliac branch of the ilio-hypogastric nerve passes over the crest of the ilium, between the posterior branches of the lumbar nerves and the preceding nerve, and supplies for a short distance the skin of the buttock. The external cutaneous nerve distributes cutaneous branches GLUTEUS MAXIMUS. 655 to the lower and outer part of the buttock over the great tro- chanter. Cutaneous branches from the lesser sciatic nerve proceed upwards from beneath the lower border of the gluteus maximus to supply the skin over the lower part of this muscle. GLUTEAL Three powerful muscles are situated in the MUSCLES. region of the buttock, one above the other, named, according to their size, the gluteus maximus, medius, and minimus. The fascia covering the gluteus maximus is comparatively thin r posteriorly, where it is attached to the sacrum, coccyx, and ilium ; but anteriorly it is very dense and glistening, and gives origin to the fibres of the gluteus medius, and lower down becomes continuous with the fascia lata. GLUTEUS This is the largest muscle of the body, and is MAXIMUS. covered by a fascia, which sends prolongations inwards deeply between the muscular bundles. Its great size is characteristic of man, in reference to his erect position. Its texture is thick and coarse. It arises from the posterior fifth of the crest of the ilium, and from the rough surface below it, from the lower part of the sacrum, the coccyx, and the great sacro- sciatic ligament. The fibres descend obliquely forwards, and are inserted thus : The anterior two-thirds terminate on a strong broad aponeurosis which plays over the great trochanter, and joins the fascia lata on the outside of the thigh (p. 616) ; the remaining third is inserted into the femur, along the gluteal ridge leading from the linea aspera to the base of the great trochanter. This muscle extends the thigh-bone upon the pelvis, and is therefore one of those most concerned in raising the body from the sitting to the erect position, and in maintaining it erect. It propels the body in walking, running, or leaping, and rotates the thigh outwards. It is supplied with blood by the gluteal and sciatic arteries ; with nerves from the lesser sciatic, and the sacral plexus. w , The gluteus maximus should be reflected from \Y HAT IS SEEN BENEATH its origin. The best way is to begin at the front THE GLUTEUS border, which overlaps the gluteus medius. The MAXIMUS. dissection is difficult, and he who undertakes it *656 GLUTEI MUSCLES. for the first time is almost sure to injure the subjacent parts. The numerous vessels which enter its under surface must be divided before the muscle can be reflected. This having been accomplished, the following objects will be exposed : The muscle covering the ilium is the gluteus medius. At the posterior border of this are the several objects which emerge from the pelvis through the great sciatic notch namely, the pyriformis muscle, above which is the trunk of the gluteal vessels and nerve, and below which are the greater and lesser sciatic nerves, the arteria comes nervi ischiatici, the long pudendal nerve, the sciatic vessels, the pudic vessels and nerve, the nerve to the obturator internus, and the coccygeus. Coming through the lesser sciatic notch, is the tendon of the obturator internus, and attached to it are the gemelli muscles, one above, the other below it. Ex- tending from the tuber ischii transversely outwards to the great trochanter is the quadratus femoris, and, below this, is seen the upper part of the adductor magnus. The origins of the semi-mem- branosus, biceps, semi-tendinosus," and of the adductor magnus, from the tuber ischii, are also seen ; as well 'as the great sacro- sciatic ligament, which passes upwards to the sacrum, and is pierced by the coccygeal branch of the sciatic artery. The great trochanter is exposed, together with a small portion of the vastus externus; and where the tendon of the gluteus maximus plays over the trochanter major, there is a large bursa, simple or multi- locular. Lastly, the side of the sacrum, the coccyx, part of the crest of the ilium, the tuberosity of the ischium, are brought into view. GLUTEUS This muscle, covered behind by the gluteus MEDIUS. maximus, and in front by the fascia lata, arises from the surface of the ilium, between the crest and the upper curved line ; also from the strong fascia which covers it towards the front. The fibres converge to a tendon, which is inserted into the oblique line on the upper and outer surface of the great tro- chanter : some of the anterior fibres in immediate connection with the tensor fascise terminate on the aponeurosis of the thigh. Between its insertion and the bone is a bursa. Reflect the gluteus medius to see the third gluteal muscle. GLUTEAL VESSELS AND NERVES. 657 The line of separation between them is marked by a large branch of the gluteal artery. GLUTEUS This muscle arises from the surface of the ilium MINIMUS. below the upper and lower curved lines, and as far back as the margin of the great sacro-sciatic notch. Its fibres pass over the capsule of the hip-joint, and converge to a tendon which is inserted into a depression on the front part of the great trochanter, a bursa being interposed. This muscle and the pre- ceding are supplied by the superior gluteal nerve, a branch of the lumbo-sacral cord. The chief action of this and the preceding muscle is to assist in balancing the pelvis steadily on the thigh, as when we are standing on one leg ; with the fixed point at the ilium, they are abductors of the thigh. The anterior fibres of the gluteus medius co-operate with the gluteus minimus and the tensor fasciae in rotating the thigh inwards. GLUTEAL Th e gluteal artery is the largest branch of the in- VESSELS AND ternal iliac (p. 540). Emerging from the pelvis NERVES. through the great sciatic foramen between the pyriforrnis and the gluteus medius, it divides into two large branches for the supply of the gluteal muscles. Of these, the superficial proceeds forwards between the gluteus maximus and medius, both of which they supply, and eventually anastomose with the poste- rior sacral and sciatic arteries ; the other the deep after a short course, divides into two branches : one the superior curves for- wards along the origin of the gluteus minimus, towards the anterior part of the ilium, to anastomose with the ascending branches of the external circumflex and the circumflex iliac arteries ; the other the inferior branch crosses obliquely over the gluteus minimus towards the insertion of this muscle, and anastomoses with the external and internal circumflex arteries. The nerve which accompanies the gluteal artery is the superior gluteal nerve, a branch of the lumbo-sacral cord. It passes out above the pyriformis, and divides into two branches a superior and an inferior branch ; the superior branch accompanies the corre- sponding branch of the gluteal artery, and supplies the gluteus medius and minimus ; the inferior branch accompanies the inferior branch of the gluteal artery, and distributes filaments to the gluteus U U 658 EXTERNAL ROTATORS OF THE THIGH. medius and minimus, and the tensor fasciee femoris. In some sub- jects it sends a branch to the gluteus maximus ; but this muscle is chiefly supplied by the lesser sciatic nerve. A surgeon ought to be able to cut down and tie the gluteal artery as it emerges from the pelvis. The following is the best rule 1 for finding it : Draw a line from the posterior superior spine of the ilium to the trochanter major, rotated inwards. The junction of the upper with the middle third of this line lies over the artery as it emerges from the upper border of the great sciatic notch. Now examine the series of muscles which rotate the thigh out- wards namely, the pyriformis, the obturator internus, the gemelli, the quadratus femoris, and the obturator externus. This muscle lies immediately below and parallel with the lower fibres of the gluteus medius. It arises within the pelvis by three fleshy fasciculi from the second, third, and fourth segments of the front surface of the sacrum between the foramina for the sacral nerves, from the margin of the great sacro- sciatic notch, and from the great sacro-sciatic ligament. The fibres, passing horizontally outwards, converge to a tendon, which is inserted into the upper border of the great trochanter. Its nerve comes from the sacral plexus. Its action is that of an abductor and an external rotator of the femur ; and, if the femur be the fixed point, it steadies the pelvis on the femur, and when the pelvis has been drawn backwards it will bring it forwards. OBTUBATOR This muscle, of which little more than the ten- INTERNUS. don can b e seen at present, arises within the cavity of the pelvis, from the inner surface of the ischium, bounded pos- teriorly by the margin of the great sacro-sciatic notch and the articular surface for the sacrum, and superiorly by the brim of the true pelvis ; from the obturator membrane, and the obturator fascia ; in front, from the inner surface of the descending ramus of the os pubis and the ascending ramus of the ischium. The fibres are directed backwards and outwards, and terminate on four tendons which converge towards the lesser sacro-sciatic notch ; pass through 1 The operation of tying the gluteal artery was first performed by John Bell. See his Principles of Surgery, vol. i. p. 421. EXTERNAL ROTATORS OF THE THIGH. 659 the foramen of the same name at nearly right angles, as round a pulley, and then unite into a single tendon to be inserted into the top of the great trochanter, in front of the pyriformis. Divide the tendon about three inches from its insertion, to see the four tendons which play over the smooth cartilaginous surface on the inner side of the tuberosity of the ischium. There is a large synovial bursa to diminish friction. The nerve to this muscle comes from the sacral plexus (sometimes from the pudic) within . the pelvis ; it emerges from the great sacro-sciatic foramen, winds round the spine of the ischium, and re-enters the pelvis through the lesser sacro-sciatic foramen to supply the muscle on its inner surface. The action of this muscle is to rotate the femur outwards ; but, in the sitting position, it loses this action, and becomes an abductor of the thigh. Between the capsule of the hip-joint and the tendon, a synovial bursa is commonly found, which not infrequently communicates with the bursa placed between the tendons and the tuberosity of the ischium. These small muscles are accessory to the obtu- rator internus, and are situated, one above, the other below it. The gemellus superior, the smaller of the two, and occasionally absent, arises from the outer surface of the spine of the ischium ; the gemellus inferior from the upper and back part of the tuberosity of the ischium. Their fibres, attached to the tendon of the obturator internus, are inserted with it into the upper border of the great trochanter. The nerves to these muscles come from the sacral plexus ; that to the superior gemellus from the lower part of the plexus ; that to the inferior gemellus comes out through the great sacro-sciatic foramen, passes beneath the superior gemellus and obturator internus to enter the muscle on its deep aspect ; this branch also distributes a filament to the quadratus femoris, and another to the hip-joint. QUADRATUS This quadrilateral muscle arises from the ridge FEMOKIS. on the outer border of the tuber ischii. Its fibres run horizontally outwards, and are inserted into the back of the great trochanter, into the greater part of the linea quadrati. The lower border of the quadratus femoris runs parallel with the upper edge of the adductor magnus ; in fact, it lies on the same plane. v u 'l 660 EXTERNAL ROTATORS OF THE THIGH. Between these muscles is generally seen a terminal branch of the internal circumflex artery. Its nerve, as previously described, comes from the sacral plexus, and enters its deep surface. OBTURATOR 1 se e this muscle, reflect the quadratus femoris EXTERNUS. from its origin. It arises from the outer surface of the body of the os pubis, from the front surface of the rami of FIG. 152. 12. N. of pyriformis. 13. N. of gemellus superior. 14. N. of gemellus inferior. 15. N. of quadratus femoris. 16. N. of gluteus maximus. 17. Long pudendal n. 18. Cutaneous n. of the but- tock. 19. N. of the long head of the biceps. 20. N. of semi-tendinosus. 21. N. of semi-membrano- sus. 22. N. of short head of the biceps. 1, 2, 3, 4, 5. Sacral nn. 6. Superior gluteal n. 7. Great sciatic n. 8. Lesser sciatic n. 9. Pudic n. 10. N. of obturator iuternus. 11. N. of levator ani. PLAN OF THE SACRAL PLEXUS AND BRANCHES. the os pubis and ischium, which form the inner border of the ob- turator foramen, from the inner two-thirds of the outer surface of the obturator membrane, and from the tendinous arch over the obturator vessels. Its fibres converge to a tendon which runs horizontally outwards over a groove on the ischium, and, running across the back of the hip-joint, is inserted into the deepest part of the trochanteric fossa of the femur. Its nerve is a branch of the GREAT SCIATIC NERVE. 661 posterior division of the obturator nerve. This muscle has in front of it, the adductor longus and brevis, the pectineus, the psoas and iliacus, the neck of the femur, and the capsular ligament ; above it are, the capsular ligament and the inferior gemellus ; beloiv it are, the adductor magnus and quadratus femoris ; behind it are, the obturator membrane and the quadratus femoris. GREAT SCIATIC This large nerve, formed by the union of the NEKVE. last lumbar and the four upper sacral nerves (fig. 152), is the largest nerve in the body, being three-quarters of an FIG. 153. 1. Gluteus medius. i&MHnMM 6 ' Great s i atic nerve. 2. Pyriformis. /JPf^HI OK\ "' Q uadratus femoris. 3. Lesser sciatic nerve. 3 f . '^C^^^^^Bmj 8 ' Gluteus ma* 1 "* 1118 - 4. Obturator interims, * \ f^T-J- /'-/^f/NjiSsf' 9- The semitendinosus with the two gemelli. / i jjj^f. ggf 1JF- &nd biceps> 5. Coccygeus. U *^ Wi.Mi^- * 10 - Adductor magnus. DEEP MUSCLES OF THE OLUTEAL REGION. inch in breadth, and supplies all the flexor muscles of the lower extremity and the extensors of the foot. Emerging from the pelvis through the great sacro-sciatic foramen below the pyriformis, it descends over the external rotator muscles of the thigh, along the interval between the tuber ischii and the great trochanter, but rather nearer to the former ; so that, in the sitting position, the nerve is protected from pressure by this bony prominence. The nerve does not descend quite perpendicu- larly, but rather obliquely forwards upon the adductor magnus, parallel with the great sacro-sciatic ligament, and below the middle of the thigh divides into the internal popliteal and the peroneal (or 662 SCIATIC NERVES AND AETERY. external popliteal). It is accompanied by a branch of the sciatic artery, called the comes nervi ischiatici. 1 The nerve distributes branches to the hamstring muscles and the adductor magnus, and sends two or more small branches to the hip-joint which pierce the posterior part of the capsular ligament. SMALL SCIATIC This comes from the lower part of the sacral NERVE, plexus. It leaves the pelvis below the pyriformis, with the great sciatic nerve, but on the inner side of it, and in company with the sciatic artery. It descends behind the gluteus maximus, and becomes cutaneous at its lower border. The mus- cular branches which it gives off are one or more inferior gluteal which enter the under surface of the gluteus maximus near its lower border. All its other branches are cutaneous, and are divided into an ascending and internal group : the ascending branches turn round the lower border of the gluteus maximus, and supply the skin of the buttock ; the internal branches supply the skin on the inner and posterior aspect of the thigh in its upper part, and one branch, larger than the rest, called the inferior pudendal, turns inwards to- wards the perineum to supply the skin of that region and the scro- tum, communicating with the inferior heemorrhoidal and superficial perineal nerves. The continued trunk runs down the back of the thigh beneath the muscular fascia, as low as the upper part of the calf with the external saphenous vein, supplying the skin all the way down, and communicates with the short saphenous nerve. This, one of the terminal branches of the internal iliac, courses along the inner aspect of the sacral plexus and pyriformis, behind the pudic artery, while this vessel is still within the pelvis. It emerges from the pelvis between the pyriformis and coccygeus, and is then seen in the gluteal region coming out between the pyriformis and superior gemellus. It then descends between the tuber ischii and the great trochanter, along the inner side of the great sciatic nerve. It gives off: (1) within 1 The arteria comes nervi ischiatici runs generally by the side of the nerve, but sometimes in the centre of it. This artery becomes one of the chief channels by which the blood reaches the lower limb after ligature of the femoral. See in the Museum of the Boyal College of Surgeons a preparation in which the femoral was tied by John Hunter fifty years before the man's death. PUDIC ARTERY AND NERVE. 663 the pelvis, branches to the muscles which form the muscular floor of the pelvis, to the rectum, the bladder, prostate and vesiculee seminales ; (2) external to the pelvis, it gives off: a, a coccygeal branch, which runs inwards through the great sacro-sciatic liga- ment, then ramifies in the gluteus maximus, and on the back of the coccyx ; b, the comes nervi ischiatici, which accompanies the great sciatic nerve for a short distance, and then enters its sub- stance ; c, the inferior gluteal branches, which enter the gluteus FIG. 154. 1. Gluteal artery and nerve. 2. Pudic artery and nerve, and nerve to obtu- rator interims. 3. Great sacro-sci- atic nerve. 4. Sciatic artery. 5. Internal circum- flex artery. C. The first perfo- rating artery. THE ARTERIES OF THE GLUTEAL REGION. maximus ; d, articular branches, which pierce the posterior capsule of the hip-joint ; e, muscular branches to the several external rotators and the hamstring muscles, and which inosculate with the external and internal circumflex, gluteal, obturator, and first perforating arteries. PUDIC ABTERT The course of this artery and nerve has been AND NERVE. fully described (p. 542). Observe now that they pass over the spine of the ischium, accompanied by the nerve to the obturator internus, and that in a thin subject it is possible to com- press the artery against the spine. The rule for finding it is this : 664 POPLITEAL SPACE. rotate the foot inwards, and draw a line from the top of the great trochanter to the base of the coccyx ; the junction of the inner with the outer two-thirds gives the situation of the artery. 1 POPLITEAL I* i g advisable to examine the popliteal space at SPACE : ITS this stage of the dissection, in order that the various BOUNDARIES. parts may be carefully made out with as little dis- turbance as possible of their mutual relations. SUBFACE The popliteal space is a lozenge-shaped hollow MARKING. at the back of the knee-joint, extending as high as the junction of the middle with the lower third of the femur, and as low as the upper sixth of the tibia. The hollow is most apparent when the knee is flexed, as then the tendinous boundaries stand out in bold relief; it is almost lost when the leg is extended. The tendon on the outer side is that of the biceps, diverging to the head of the fibula ; on the outer side, and below, are the plantaris and outer head of the gastrocnemius, which are not well defined ; on the inner side, above, we can feel three tendons in the following order from within outwards the semitendinosus, the semimem- branosus, and the gracilis ; below, on their inner side, is the inner head of the gastrocnemius. The upper angle of this space is formed by the diverging biceps and semitendinosus ; the lower angle by the converging heads of the gastrocnemius. Passing from above downwards in the middle of the space, and in the following order, are the internal popliteal nerve, the popliteal vein and artery ; and along the inner border of the biceps can be felt the external popli- teal nerve. Filling up the hollow is a quantity of soft fat, with some lymphatic glands, and on the bone rest the articular arteries. A vertical incision must be made along the middle of the ham, extending from six inches above, to three inches below the knee : transverse incisions should be made at each extremity of the vertical, so that the skin may be conveniently reflected. In doing so, care must be taken to preserve the cutaneous branch of the lesser sciatic nerve, which descends over the space to the back of the leg. 1 Mr. Travers succeeded in arresting haemorrhage from a sloughing ulcer of the glans penis by pressing the pudic artery with a cork against the spine of the ischium. POPLITEAL SPACE. 665 The muscular fascia covering the space is very strong, and strengthened by numerous transverse fibres. It is pierced by the posterior saphena vein, which passes in to join the popliteal vein. The fascia having been reflected, the muscles and tendons con- stituting the boundaries of the popliteal space are to be cleaned. The boundaries of the space can now be seen to be formed, as before stated, above, by the divergence of the hamstring muscles to reach their respective insertions ; below, by the converging heads of the gastrocnemius : its shape is therefore that of a lozenge. Above, it is bounded on the inner side by the semitendinosus, semimem- branosus, gracilis, and sartorius ; on the outer side, by the biceps ; below, it is bounded, on the inner side by the internal head of the gastrocnemius ; on the outer, by the external head of this muscle and the plantaris. The space is occupied by a quantity of fat, which permits the easy flexion of the knee ; and in this fat ate found the popliteal vessels and nerves, in the following order : nearest to the surface are the nerves ; the artery lies close to the bone, the vein being superficial to the artery (fig. 155). GKEAT SCIATIC Along the outer border of the semimembranosus, NERVE. and covered by the long head of the biceps, is the great sciatic nerve, which, after giving off branches to the three great flexor muscles and the adductor magnus, divides, about the lower third of the thigh (higher or lower in different subjects), into two large nerves the peroneal or external popliteal and the internal popliteal. The peroneal nerve runs close by the inner side of the tendon of the biceps, 1 and subsequently in the groove between this muscle and the outer head of the gastrocnemius, towards the head of the fibula. As it passes round the joint it gives off two articular branches to the outer side of the knee, which accompany the external superior and inferior articular arteries, and a recurrent articular branch, which runs with the recurrent tibial artery to the front of the knee. It supplies also two or three cutaneous brandies 1 The nerve is, therefore, very liable to be injured in the operation of dividing the outer hamstring. In the diagram, the nerve is not near enough to the tendon, their connections having been severed. 666 POPLITEAL SPACE. to the posterior and outer surfaces of the leg, as far as its middle third. The communicans peronei (fig. 155) is a small branch given off as the nerve passes over the gastrocnemius ; it crosses the outer head of this muscle and joins the external saphenous, which runs Fio. 155. Semitendinosus. Semimembranosus. Gracilis. Sartorius. Inner haid of gastrocne- mius. LEFT POPLITEAL SPACE. down the back of the calf, and behind the external malleolus, to supply the outer side of the foot and little toe. Below the head of the fibula we have already traced the division of the peroneal into the anterior tibial, and the musculo-cutaneous nerves (p. 652). The internal popliteal nerve, the larger of the two divisions of the great sciatic nerve, accompanies the popliteal artery, and, at the POPLITEAL SPACE. 667 lower border of the popliteus, it is continued under the name of the posterior tibial. The nerve in the popliteal space lies superficial to and rather external to the artery, and gives off four or five muscular branches which supply the two heads of the gastrocnemius, the plan- taris, the soleus, and the popliteus ; three articular branches, two accompanying the internal superior and inferior articular arteries, the third piercing the back of the capsule accompanied by the azygos artery ; and the short or external saphenous, which descends in the groove between the two heads of the gastrocnemius, is joined about the middle of the leg by the communicans peronei, and then, run- ning down behind the outer malleolus in company with the external saphena vein, is distributed to the outer side of the foot and the little toe. The continuation of the internal popliteal nerve, as posterior tibial, supplies all the flexor muscles on the back of the leg and the sole of the foot. POPLITEAL By clearing out all the fat, we observe that the VESSELS. popliteal vessels enter the ham through an aperture in the adductor magnus, and descend close to the back part of the femur, and the back of the knee-joint. At first they are partially overlapped (in muscular subjects) by the semimembranosus ; in- deed the outer border of this muscle is a good guide to the artery in the operation of tying it. The popliteal artery lies upon the tri- angular surface at the back of the lower third of the femur ; then, upon the ligamentum posticum Winslowii ; and, lastly, upon the popliteus, at the lower border of which it divides into the anterior and posterior tibial. Superficial to the artery are the semimembranosus, a consider- able amount of fat, the gastrocnemius, the plantaris, the soleus, the popliteal vein, and the internal popliteal nerve ; internally., it has the semimembranosus, the internal condyle of the femur, and the inner head of the gastrocnemius ; externally, it has the biceps, the external condyle, the outer head of the gastrocnemius, and the plantaris. The artery gives off the external and internal superior articular arteries ; lower down, the external and internal inferior articular arteries, the superior and inferior muscular branches, the azygos, and cutaneous branches. The description of these branches of the 668 DISSECTION OF THE BACK OF THE THIGH. popliteal will deferred till later, until the muscles of the calf have been reflected. The articular branches which come from the popliteal are given off at right angles to that vessel ; and besides these it gives off the sural which supply the muscles of the calf, and the azygos artery ; close to the vessel is the articular branch of the obturator nerve which supplies the knee-joint. The popliteal vein lies superficial to the artery, and rather to its outer side. It receives the short saphena vein. Its coats are remarkably thick, and on transverse section resemble those of an artery of a similar size. LYMPHATIC Two or more lymphatic glands are situated one GLANDS. on each side of the artery. They deserve atten- tion, because, when enlarged, their close proximity to the artery may communicate a pulsation which might be mistaken for an aneurism. DISSECTION OF THE BACK OF THE THIGH. The incision should be continued along the remainder of the back of the thigh, and the skin reflected. The fat should be removed, and the cutaneous branches derived from the external and internal cutaneous nerves, and the small sciatic, should be carefully sought out. CUTANEOUS ^ ^ e s ^^ n on ^ ne middle of the back of the thigh NERVES AND is supplied by the small sciatic nerve, which runs VEINS, down beneath the deep fascia as far as the middle third ; then pierces it, and runs down as far as the middle third of the calf, distributing branches on each side. On the outer side, a few cutaneous branches from the posterior division of the external cutaneous nerve supply the skin as far as the middle third ; on the inner side are small branches from the small sciatic and the internal cutaneous nerves as low as the knee-joint. The subcutaneous veins at the back of the thigh are very small ; here they would be liable to pressure. But near the popliteal space there is a vein, called the external or short sapliena. It comes up BACK OF THE THIGH. 669 the back of the calf, and joins the popliteal vein after perforating the strong fascia covering the space. MUSCULAR Respecting this, remark that its fibres run FASCIA. chiefly in a transverse direction, that it becomes stronger as it passes over the popliteal space, and that here it is connected with the tendons on either side. Remove it, to examine the powerful muscles which bend the leg, called the hamstrings. HAMSTKING There are three of these, and all arise by strong MUSCLES. tendons from the tuber ischii. One, the biceps, passes downwards and outwards to be inserted into the head of the fibula ; the other two namely, the semitendinosus and semi- membranosus descend inwards and are inserted into the tibia. The divergence of these muscles towards their respective inser- tions occasions the space termed the popliteal, which is occupied by soft fat, the popliteal vessels, nerves, and lymphatic glands. This muscle has two origins, a long and a short. The long head arises, by a strong tendon, from the back part of the tuber ischii in common with the semitendino- sus ; the short head, by fleshy fibres, from the outer lip of the linea aspera of the femur between the vastus externus and the adductor magnus, and from the external intermuscular septum : this origin begins at the linea aspera, just below the insertion of the gluteus maximus, and continues nearly down to the external condyle. It joins the long head of the muscle, and both terminate on a common tendon, which is inserted into the outer side of the head of the fibula, by two portions separated by the external lateral ligament of the knee-joint. It also gives off a strong expansion to the fascia of the leg. The tendon covers part of the external lateral ligament of the knee-joint, and a small bursa intervenes. The biceps is not only a flexor of the leg, but rotates the leg, when bent, outwards. It is the muscle which in chronic disease of the knee dislocates the leg outwards and backwards, and at the same time rotates it outwards. Each head of the biceps is supplied by the great sciatic nerve. The short head is sometimes supplied by the peroneal. SEMITEN- This arises, in common with the biceps, from DINOSUS. the back part of the tuber ischii by muscular 670 HAMSTRING MUSCLES. fibres and also from the inner border of the tendon of the biceps for about three inches. The muscle passes downwards and inwards, and terminates in the middle of the thigh in a long round tendon, which rests upon the semimembranosus, and is inserted into the upper part of the inner surface of the tibia by an expanded tendon, below the tendon of the gracilis, and behind that of the sartorius. Like them, it plays over the internal lateral ligament of the knee, and is provided with a bursa. Its nerve comes from the great sciatic. The semitendinosus sends off from the lower border of its tendoo a very strong fascia to cover the leg, which is attached along the inner edge of the tibia. The middle of the muscle is usually intersected by an oblique tendinous line. SEMIMEM- This muscle arises from the upper and outer BKANOSUS. facet on the back of the tuber ischii above and external to the two preceding, by means of a strong flat tendon, which extends nearly half-way down the thigh. This tendon de- scends obliquely under the biceps and semitendinosus, and termi- nates in a bulky muscle, which lies on a deeper plane, and more internal than the others, and is inserted by a thick tendon into the posterior and inner part of the internal tuberosity of the head of the tibia. In connection with the insertion of this tendon, notice, (1) that from its inner side a strong fasciculus is prolonged forwards under the internal lateral ligament of the knee, and that a bursa intervenes between them ; (2) that from its outer and posterior part it sends a strong prolongation upwards and outwards to the back part of the external condyle of the femur, forming the principal portion of the ligamentwn posticum Winslowii, which covers the back of the knee-joint ; (3) that a dense fascia proceeds from its lower border, and binds down the popliteus ; (4) that it is intimately connected with the semilunar cartilages of the joint, so as to keep them in place during its movements. Its nerve comes from the great sciatic. A great bursa is almost invariably found between the semi- membranosus and the inner head of the gastrocnemius, where they rub one against the other. It is generally from one and a half to two inches long. The chief point of interest concerning it is, that HAMSTRING MUSCLES. 671 FIG. 156. it occasionally communicates with the synovial membrane of the knee-joint, not directly, but through the medium of another bursa beneath the inner head of the gastrocnemius. From an examina- tion of 150 bodies, it appears that this communication exists about once in five times ; and it need scarcely be said that the proportion is large enough to make us cautious in in- terfering with this bursa when it becomes enlarged. 1 ACTION OF THE These muscles produce HAMSTRING two different effects, ac- MUSCLES. cording as their fixed point is at the pelvis or the knee. With the fixed point at the pelvis, they bend the knee; with the fixed point at the knee, they take a very important part in maintaining the body erect. For instance, if, when standing, the body be bent at the hip, and the muscles in question be felt, it will be found that they are in strong action, to prevent the trunk from falling forwards : they, too, are the chief agents concerned in bringing the body back again to the erect position. In doing this, they act upon a lever of the first order, as shown in fig. 156 ; the acetabulum being the fulcrum r, the trunk w, the weight to be moved, and the power P at the tuber ischii. To put the action of the muscles of the thigh on the pelvis in the clearest point of view, let us suppose we are standing upon one leg : the bones of the lower extremity represent a pillar which supports the weight of the trunk on a ball-and-socket joint ; the weight is nicely balanced on all sides, and prevented from falling 1 When the bursa in question becomes enlarged, it occasions a fluctuating swelling of greater or less dimensions on the inner side of the popliteal space. The swelling bulges out, and becomes tense and elastic when the knee is extended, and vice versa. As to its shape, it is generally oblong ; but this is subject to variety, for we know that the bursas, when enlarged, are apt to become multilocular, and to extend between the muscles where there is the least resistance. 672 DISSECTION OF THE BACK OF THE LEG. by four groups of muscles. In front, are the rectus and sartorius ; on the inner side, the adductors ; on the outer side, the gluteus medius and minimus; behind, the hamstrings and gluteus maximus. When the knee is semi-flexed, the semimembranosus can also rotate the leg inwards, thus assisting the popliteus ; the biceps can also in the same position of the knee rotate the leg slightly outwards. The hamstring muscles are supplied with blood by the perfo- rating branches of the profunda, which come through the tendon of the adductor magnus close to the femur, and by muscular branches from the popliteal artery. Their nerves are derived from the great sciatic. GREAT SCIATIC This nerve descends from the gluteal region NERVE. upon the adductor magnus, and, after being crossed by the long head of the biceps, runs along the outer border of the semimembranosus down the popliteal space. The great sciatic divides into its two terminal divisions at a variable distance from its exit through the great sciatic foramen, sometimes high up, occasionally lower down than usual. The further course of this nerve has already been described (p. 665). Deferring the course, relations, and branches of the popliteal artery till this vessel is exposed throughout its whole course, pass on now to the dissection of the calf. DISSECTION OF THE BACK OF THE LEG. SURFACE The back of the leg gradually narrows from MARKING. above downwards so as to form a long cone ; the upper half is convex and fleshy, corresponding to the gastrocnemius and the soleus muscles ; the lower half suddenly diminishes, so that the posterior borders of the tibia and fibula can be easily felt extending to their respective malleoli. In a well-developed subject with not much fat the two heads of the gastrocnemius can be seen through the skin, the inner head being the broader and lower of the two ; the tendon into which they are inserted (tendo Achillis) rapidly narrows to be attached to the posterior and upper part of BACK OF THE LEG. 673 the tuberosity of the os calcis. On the inner and outer sides of the lower part of this tendon there is a well-defined vertical groove ; bounded laterally by the tibia and fibula. In cases of synovial disease of the ankle-joint these grooves are lost, so that instead of a depression there is a convexity. In these grooves can be felt the tendons passing round the ankle behind the malleoli ; on the inner side are the tibialis posticus, flexor longus digitorum, and flexor longus hallucis ; on the outer side are the peronei longus and brevis. Continue the incision down the centre of the calf to the heel, where a transverse incision must also be made. The skin should now be reflected, taking care of the subcutaneous veins and nerves. SHORT OR The large vein seen in the middle of the back POSTERIOR of the leg is called the short or posterior saphena. SAPHENA VEIN j^ commences on the outer side of the dorsum of the foot, ascends behind the outer ankle, where it has a communi- cation with the deep veins, and then runs up the calf between the two bellies of the gastrocnemius, receiving numerous veins in its course, and being guarded by several valves. It eventually passes through the muscular fascia, and joins the popliteal vein. CUTANEOUS The back of the leg is supplied by cutaneous NERVES. nerves : in the middle, above, by the small sciatic nerve, and below, by the short or external saphenous ; on the outer side, by the communicans peronei ; and on the inner side, by branches from the internal saphenous nerve. SHORT OR The short scuplienous nerve ! is derived from EXTERNAL the internal popliteal nerve (fig. 155), and passes .SAPHENOUS NERVE. ,j own beneath the deep fascia between the two heads of the gastrocnemius to the middle of the calf, where it pierces the fascia. Here it is joined by a branch from the peroneal nerve (communicans peronei) ; it then descends with the short saphena vein, usually on its fibular side, and is finally distributed to the outer side of the foot and the little toe. 1 This nerve is sometimes called the communicans poplitei, and does not take the name of short saphenous nerve till its junction with the communicans peronei LAYER Having traced the principal vessels and nerves, OF MUSCLES. divide them with the flexor tendons near the os calcis, and turn them down towards the toes, to expose the deep muscles in the sole. These are, the flexor brevis and adductor hallucis, the flexor brevis minimi digiti, and the transversalis pedis. FLEXOR BREVIS This muscle arises by a pointed tendon from the HALLUCIS. cuboid bone, and from the fibrous prolongation of the tibialis posticus into the external cuneiform It proceeds along the metatarsal bone of the great toe, and divides into two portions, which run one on each side of the long flexor tendon, and are in- serted by tendons into the sides of the first phalanx of the great toe. The inner tendon is inseparably connected with the abductor hallucis, the outer with the adductor hallucis. In each tendon there is a sesamoid bone. These bones not only increase the strength of the muscle, but, both together, form a pulley for the free play of the long flexor tendon ; so that in walking the tendon is not pressed upon. Its nerve comes from the internal plantar (fig. 160, fc). ADDUCTOR This very powerful muscle arises from the bases HALLUCIS. of the second, third and fourth metatarsal bones, and from the sheath of the peroneus longus. Passing obliquely forwards and inwards across the foot, it is inserted through the ex- ternal sesamoid bone into the outer side of the base of the first phalanx of the great toe together with the inner head of the flexor MUSCLES OF THE SOLE OF THE FOOT. 691 brevis. This muscle greatly contributes to support the arch of the foot. Like the adductor of the thumb, it should be considered as an interosseous muscle. Its nerve is derived from the external plantar (fig. 160, i). FLEXOR BBEVIS This little muscle rests on the fifth metatarsal MINIMI DIGITI. bone, and arises from the base of the fifth meta- a. Abductor hallucis. 6. Plexor brevis digitorum. c. Abductor minimi digiti. d. Tendon of pero- neus longus. , n. Flexor longus hallucis. /. Tendon of flexor longus digito- rum. d g. Flexus accesso- rius. h. Flexor brevia minimi digiti. t - . Adductor hallucis. i. Flexor brevis hallucis. /. Interossei. m. Transversalis pedis. o. Tibialis postious. VIEW OF THE THIRD LAYER OF MUSCLES OF THE FOOT. tarsal bone and the sheath of the peroneus longus ; it proceeds for- wards along the bone, and is inserted into the outer side of the base of the first phalanx of the little toe. It is supplied by the external plantar nerve (fig. 160, Ti). 692 INTEROSSEI PEDIS. TRANSVERSALIS This slender muscle runs transversely across the PEDIS. distal ends of the metatarsal bones. It arises by little fleshy slips from- the inferior metatarso-phalangeal ligaments of the three outer toes, and the transverse ligament of the meta- tarsus, and is inserted into the outer side of the first phalanx of the great toe with the adductor hallucis, of which it ought to be considered a part. Its nerve comes from the external plantar (fig. 160, m). The fourth layer of muscles consists of the interossei. These muscles are arranged nearly like those in the hand. They occupy the intervals between the metatarsal bones, and are seven in number, four being on the dorsal aspect of the foot, three on the plantar. The four dorsal interossei arise each by two heads from the contiguous sides of the metatarsal bones, and are inserted into the bases of the first phalanges, and into the aponeurosis of the extensor communis digitorum on the dorsurn of the toes. The first is inserted into the inner side of the second toe ; the remaining three into the outer sides of the second, third, and fourth. The plantar interossei, three in number, arise from the inner sides and under surfaces of the third, fourth, and fifth metatarsal bones, and are inserted respectively into the inner sides of the bases of the first phalanges of the third, fourth, and fifth toes, and into the aponeurosis of the common extensor tendon. The use of the interosseous muscles is to draw the toes to or from each other, and they do the one or the other according to the side of the phalanx on which they act. Now, if we draw a longi- tudinal line through the second toe, we find that all the dorsal muscles draw from that line, and the plantar toivards it. This is the key to the action of them all. A more detailed account of these muscles is given in the dissection of the hand (p. 399). Be- tween the tendons of the interossei, that is, between the distal ends of the metatarsal bones, there are bursae which facilitate movement. They sometimes become enlarged and occasion painful swellings between the roots of the toes. The flexor brevis minimi digiti, the transversalis pedis, and all the interossei, are supplied by the external plantar nerve. Now trace the tendons of the peroneus longus and tibialis LIGAMENTS OF THE PELVIS. 693 posticus. The tendon of the peroneus longus is the deepest in the sole. It runs through a groove in the cuboid bone obliquely across the sole towards its insertion into the outer side of the base of the metatarsal bone of the great toe and into the internal cuneiform bone ; not infrequently it has a fasciculus of attachment into the second metatarsal bone. It is confined in a strong fibrous sheath, lined throughout by synovial membrane. The tendon of the tibialis posticus may be traced over the internal lateral ligament of the ankle, and thence under the head of the astragalus to the tuberosity of the scaphoid, and the internal cuneiform bones. Prolongations are sent off to the cuneiform bones, to the cuboid, to the sustentaculum tali, and to the bases of the second, third, and fourth metatarsal bones. Observe that the tendon contributes to support the head of the astragalus, and that for this purpose it often contains a sesamoid bone. This is one of the many provisions for the maintenance of the arch of the foot. DISSECTION OF THE LIGAMENTS. sacrum i g united to the last lumbar ver- L IENTS OF THE PELVIS WITH tebra in the same manner as one vertebra is to THE FIFTH LUMBAR another viz., by the prolongation of the anterior and posterior common ligaments, the interver- tebral fibro-cartilage, the ligamenta subflava, supra- and inter- spinous ligaments, and the capsular ligaments. The student should, therefore, refer to the description of the ligaments of the spine (p. 295). The ilio-lumbar ligament is very strong, and extends directly outwards from the tip of the transverse process of the last lumbar vertebra to the crest of the ilium (fig. 162). The lumbo-sacral ligament varies much in its extent and attach- ment, and passes from the anterior and lower border of the trans- verse process of the fifth lumbar vertebra to the lateral part of the base of the sacrum ; the fibres as they descend obliquely out- wards become frayed out, joining in part the anterior sacro-iliac ligament. 694 SACRO-ILIAC ARTICULATION. LIGAMENTS OF The sacrum is connected with the coccyx by THE SACRUM AND means of an anterior and a posterior sacro-coc- COCCYX. cygeal ligament and by an intervertebral fibro- cartilage. The posterior sacro-coccygeal ligament is a flattened fasciculus of fibres extending from the lower margin of the sacral canal to the posterior surface of the coccyx : this ligament closes in the inferior termination of the sacral canal. The anterior sacro-coccygeal ligament is a thin band of fibres passing along the front of the sacrum to the coccyx. The intervertebral disc is a thin layer of fibro-cartilage, firm in the centre, thinner laterally and in front and behind, with occa- sionally a synovial membrane. Laterally, there are some irregular strands of fibres, the lateral ligaments, which extend from the lower lateral part of the sacrum to the transverse process of the coccyx. The segments of the coccyx are in early life separated by interposed fibro-cartilages, which subsequently ossify ; they have in front and behind a continuation of the anterior and posterior common ligaments. The innominate bones are connected to each other in front, con- stituting the symphysis pubis ; posteriorly, to the sacrum, forming the sacro-iliac symphysis. SACEO-ILIAC This articulation is an example of that form ARTICULATION. o f amphiarthrodial joints where the surfaces are covered with fibro-cartilage, with an incomplete synovial mem- brane. The articulation is formed between the auricular surfaces of the lateral portions of the sacrum and ilium. The anterior part of the bones forming this articulation is incrusted with articular cartilage, of which the shape is like that of the ear. Later in life these two surfaces are more or less connected by thin interarticular transverse fibres, so that the interval between them is very irre- gular, and frequently contains yellow, viscid material. In front of the articulation there is the anterior sacro-iliac ligament, and behind, the posterior sacro-iliac ligament. The anterior sacro-iliac ligament consists of thin ligamentous fibres passing in front of the sacrum and ilium. SACRO-ILIAC LIGAMENTS. 695 The posterior sacro-iliac ligament is composed of fibres much stronger and more marked, which pass behind the articulation. It consists of two portions : the upper, or horizontal, extends from the upper two transverse tubercles of the sacrum, and is attached to the rough surface of the ilium above the auricular surface; the lower, or oblique, is a well-marked fasciculus of fibres, the oblique sacro-iliac ligament, passing from the posterior superior spine to the third segment of the sacrum. SACBO- SCIATIC These are two strong ligaments passing from LIGAMENTS. the sacrum to the ischium. FIG. 161. Great sacro - sciatic ligament. . . . Lesser sacro - sciatic ligament. . . . Ilio-femoral or acces- sory ligament of the hip-joint. The great sacro-sciatic ligament is triangular and thick ; but narrower in the middle than at either extremity. Its base is broad, and is attached to the posterior inferior iliac spine, and to the sides of the sacrum and coccyx ; rapidly narrowing, it descends obliquely outwards towards the tuberosity of the ischium, where it again expands to be attached to the inner margin of this bone. This attached portion is continued upwards for some distance as a prolongation, the falciform process, into the inner margin of the ramus of the ischium, where it becomes continuous with the obturator fascia, forming a protection for the pudic vessels and nerve. 696 PUBIC SYMPHYSIS. The lesser sacro-sciatic ligament lies in front of the preceding ligament, and, like it, is triangular, though smaller and shorter. It passes from the sides of the sacrum and coccyx to the spine of the ischium, where it narrows considerably. The attachments of the sacro-sciatic ligaments to the sacrum and coccyx are more or less blended, and they not only serve to connect the bones, but also, from their great breadth, contribute to diminish the lower aperture of the pelvis. PUBIC STM- This is formed by the union of the pubic bones, PHYSIS. in front, by means of an interposed piece of fibro- cartilage. It is an amphiarthrodial articulation, and is secured by the following ligaments : The anterior pubic ligament consists of several layers of irre- gular superficial fibres which run obliquely and decussate with each other, and of deeper fibres which pass transversely across from one bone to the other, and are connected with the fibre-cartilage. The posterior pubic ligament consists of fibres, less distinct than the anterior, which connect the two pubic bones posteriorly. The superior pubic ligament passes across the upper surface of the pubic bones. The subpubic ligament is very strong, and extends between the rami of the pubic bones, beneath the fibro-cartilage with which it is blended ; it rounds off the pubic arch, and is situated between the two layers of the triangular ligament. The intermediate fibro-cartilage is composed of two layers of car- tilage, each attached to the inner border of the body of the os pubis by a number of nipple-like processes fitting in to corresponding depressions on the bony surface. Between these cartilaginous plates there is a thick stratum of fibrous and fibro-elastic tissue. In the middle line at the upper and back part is usually a smooth cavity lined with epithelium. The cartilage acts as a buffer, and breaks the force of shocks passing through the pelvic arch. LIGAMENTS OF This joint is secured by the form of the bones, THE HIP-JOINT. a nd by the strength of the powerful muscles which surround it. Although an enarthrodial or ball-and-socket joint, its range of motion is somewhat limited ; the disposition of its ligaments restricts its range of motion to those directions only HIP-JOINT. 697 which are most consistent with the maintenance of the erect attitude, and the requirements of this part of the skeleton. The ligaments of the hip-joint are the capsular, the ilio- femoral, the ligamentum teres, the cotyloid, and the transverse. CAPSULAB The capsular ligament is attached above to the LIGAMENT. circumference of the acetabulum, a little external to the margin, also to the transverse ligament, and by a few fibres to the outer margin of the obturator foramen ; below, to the anterior intertrochanteric ridge in front ; above, to the root of the great trochanter, and to the middle of the neck behind, about half an inch above the posterior intertrpchanteric ridge. The anterior and upper part of the capsular ligament is very thick and strong, composed chiefly of longitudinal fibres with a few deeply seated circular fibres, which are concealed by the superficial longi- tudinal bands.. The posterior aspect of the capsular ligament is represented by a few sparsely scattered fibres. The front part of the ligament is rendered exceedingly strong by several accessory ligaments, one of which, called the ilio-femoral ligament, extends from the anterior inferior iliac spine, and from a depression above the acetabulum, and then divides like the two arms of the inverted letter ^ : one, the inner and vertical, passes to the base of the lesser trochanter ; the outer, to the upper part of the ante- rior intertrochanteric line. In addition, there is at the lower and back part a broad ligament, the ischio-capsular ligament, whose fibres extend from the ischium to the inner part of the joint, close to the lesser trochanter ; and a third accessory ligament, the pubo- femoral, consists of the thin fibres converging from the ilio-pectineal eminence, and the margin of the obturator foramen to the front and inner part of the capsular ligament. The ilio-femoral ligament is very strong, and serves as a strap to prevent the femur being extended beyond a certain point, and limits rotation inwards and outwards. The capsule is in relation, in front, with the iliacus and psoas muscles, from which it is separated by a synovial bursa. This bursa occasionally communicates by a rounded aperture with the synovial cavity of the hip-joint. Open the capsule to ascertain its great thickness in front, and '698 LIGAMENTS OF THE HIP-JOINT. its strong attachment to the bones. This exposes the cotyloid ligament and the ligamentum teres. LIGAMENTUM The ligamentum teres is exposed by drawing the TEKES. head of the femur out of the socket. This lisa- O ment is somewhat flat and triangular. Its base, which is bifid, is attached, below, to the borders of the notch in the acetabulum, where it becomes continuous with the transverse ligament ; its FIG. 162. Ilio-ltimbar ligament . Posterior sacro-iliac ligament VERTICAL SECTION THROUGH THE HIP. apex, to the fossa in the head of the femur. To prevent pressure on it, and to allow free room for its play, there is a gap at the bottom of the acetabulum. This gap is not crusted with cartilage like the rest of the socket, but is occupied by soft fat. The liga- mentum teres is surrounded by the synovial membrane. An artery runs up with it to the head of the femur. It is a branch of the obturator, and enters the acetabulum through the notch at the lower part. LIGAMENTS OF THE HIP-JOINT. 699 The chief use of the ligamentum teres is to assist in steadying the pelvis on the thigh in the erect position. In this position, the ligament is vertical and quite tight (fig. 162); it therefore pre- vents the pelvis from rolling towards the opposite side, or the thigh from being adducted beyond a certain point. Another purpose served by this ligament is to limit rotation of the thigh, both inwards and outwards. COTYLOID The cotyloid ligament is an annular piece of LIGAMENT. fibro-cartilage which is attached all round the margin of the acetabulum. Its circumference is thicker than its free margin, which is very thin, so that on a transverse section the cartilage is triangular. Both its surfaces are covered with synovial membrane, and its attachment to the margin of the acetabulum is effected by oblique fibres passing from without inwards, and inter- lacing in all directions at an acute angle. The ligament is thicker above and behind than elsewhere ; it thus deepens the socket, and embraces the head of the femur like a sucker. It extends over the notch at the lower part of the acetabulum, being attached to a TRANSVERSE ligament, the transverse, which passes across the LIGAMENT. notch, and thus converts it into a foramen. Be- neath the transverse ligament some of the vessels and nerves pass into the joint to supply it. SYNOVIAL . The synovial membrane extends from the carti- MEMBBANE. laginous border of the head, round the neck as far as the attachment of the capsular ligament, on the inner surface of which it is reflected as far as the margin of the acetabulum. Thence it passes over the superficial surface of the cotyloid ligament, curves round its inner sharp border so as to line its deeper surface ; it then covers the osseous surface of the acetabulum, and is finally con- tinued as a tubular sheath over the ligamentum teres to the head of the femur. The synovial membrane, it will be seen, extends down to the base of the neck of the femur in front, but only two-thirds behind. Between the bottom of the acetabulum, as far as the cotyloid notch, and the synovial membrane, is a collection of fat and connective tissue called the gland of Havers. The ligaments of the hip-joint are so arranged that, when we stand ' at ease/ the pelvis is spontaneously thrown into a position 700 MOVEMENTS AT THE HIP-JOINT. in which its range of motion is the most restricted ; for the acces- sory ligaments of the capsule prevent it from being extended beyond a straight line, and the ligamentum teres prevents its rolling towards the opposite side. This arrangement economises muscular force in balancing the trunk. The atmospheric pressure is, of itself, sufficient to keep the limb suspended from the pelvis, supposing all muscles and liga- ments to be divided. When fluid is effused into the hip-joint, the bones are no longer maintained in accurate contact ; and it some- times happens that the head of the femur escapes from its cavity, giving rise to a spontaneous dislocation. The movements at the hip-joint are those of flexion, extension, abduction, adduction, rotation, and circumduction. The flexors are, the ilio-psoas, the sartorius, the pectineus, the adductor longus and brevis, the gluteus medius and mini- mus. The extensors are, the gluteus maximus, the biceps, semi- tendiiiosus, and the semimembranosus. The abductors are, the upper fibres of the gluteus maximus, the gluteus medius and minimus, the pyriformis, and, when the joint is flexed, the obturator internus and the two gemelli. The adductors are, the three adductors, the pectineus, the gra- cilis, and the sartorius. The external rotators are, the ilio-psoas, the three adductors, the pectineus, the gluteus maximus, the posterior fibres of the gluteus medius, the obturator externus and internus, the gemelli, the quadratus femoris, the pyriformis, and the sartorius. The internal rotators are, the tensor fasciae femoris, the anterior fibres of the gluteus medius, and the gluteus minimus. Circumduction is effected by the successive action of the different muscles in the order of their attachment into the femur. The muscles in immediate relation, with the hip-joint are, in front, the iliacus and psoas ; on the outer side, the reflected tendon of the rectus, the gluteus minimus ; behind, the pyriformis, gemel- lus superior, obturator internus, gemellus inferior, obturator ex- ternus, and quadratus femoris ; on the inner side, the pectineus and obturator externus. LIGAMENTS OF THE KNEE-JOINT. 701 LIGAMENTS OP The knee-joint is a ginglymus or a hinge-joint, THE KNEE-JOINT. and the bones entering into its formation are, above, the condyles of the femur, below, the head of the tibia, and in front, the patella. Looking at the skeleton, one would suppose that it was very insecure ; but this insecurity is only apparent, the joint being surrounded by powerful ligaments, and a thick capsule formed by the tendons of the muscles which act upon it. First examine the tendons concerned in the protection of the knee-joint. In front is the ligameiitum patellae ; on each side are the tendons of the vasti ; on the outer side, in addition, it is strengthened by the strong ilio-tibial band ; on the inner side there are also the tendons of the sartorius and gracilis ; at the back of the joint are the tendons of the gastrocnemius and plantaris, with the semimembranosus and semitendicosus, in addition, on its inner part, and the tendons of the popliteus and biceps on its outer part. It deserves to be mentioned that the weakest part of the articulation is near the tendon of the popliteus, which arises within the joint : here, therefore, pus or fluid formed in the popliteal space may make its way into the joint, or vice versa. The ligaments of the joint may be divided into those outside the joint and those within it. Those outside the joint are, the ligamentum patellae, the internal lateral, the two external lateral, the posterior ligament, and the capsular ligament. Those within the joint are, the two crucial, the two semilunar fibro-cartilages, the transverse, the coronary, the ligamenta alaria, and the ligamentum mucosum. LIGAMENTCM The ligamentum patellce is a strong, thick, liga- PATELL^E. mentous band, about three inches long, extending from the lower border of the patella to the tubercle of the tibia. Beneath it, is found a considerable amount of fat, which separates the ligament from the joint, and in fat people forms a prominent elastic mass on each side of the ligament. There is a synovial bursa between the ligamentum patellae and the tuberosity of the tibia. INTERNAL This is a broad, flat band, which extends from LATERAL the inner condyle of the femur to the inner tube- LIGAMENT. rosity and the inner aspect of the shaft of the 702 LIGAMENTS OF THE KNEE-JOINT. FIG. 163. tibia (fig. 163). A few of the deeper fibres are attached to the inner semilunar cartilage, and serve to keep it in place. The inferior internal articular artery, and part of the tendon of the semimembranosus, pass underneath this ligament. In the several motions of the joint, there is a certain amount of friction between the ligament and the head of the tibia, and consequently a small bursa is interposed. EXTERNAL The long external LATERAL lateral ligament is a LIGAMENTS. strong round band which extends from the outer condyle of the femur to the outer part of the head of the fibula. This ligament sepa- rates the two divisions of the tendinous insertion of the biceps. Beneath it pass the tendon of the popliteus and the inferior external articular artery. The short external lateral ligament is situated posterior to, and runs parallel with, the preceding ligament ; it passes from the posterior and outer part of the condyle of the femur to the tip of the styloid process of the fibula ; the tendon of the popliteus also lies beneath it. POSTERIOR This, which is generally called the ligamentum LIGAMENT. posticum Winslowii, covers the whole of the pos- terior surface of the knee-joint, and consists of two portions one formed by a broad flat band of vertical fibres passing from the posterior surface of the femur between and above the condyles to the posterior part of the tuberosity of the tibia ; the other con- sists of an oblique tendinous expansion from the semimembranosus (p. 670), which passes upwards and outwards from the internal tuberosity of the tibia to the back of the outer condyle of the femur. It is pierced by numerous blood-vessels to supply the knee-joint, chiefly by the azygos artery and a branch from the DIAGRAM OF THE SEMILUNAR CARTILAGES AND LATERAL LI- GAMENTS OF THE KNEE. 1. Internal lateral ligament. External ditto. LIGAMENTS OF THE KNEE-JOINT. 703 obturator nerve (p. 643). This ligament not only closes and protects the joint behind, but prevents its extension beyond the perpendicular. CAPSULAR The capsular ligament occupies the intervals LIGAMENT. between the other ligaments, and so completes the fibrous investment of the joint. It is materially strengthened by fibrous expansions from many of the tendons in connection with the articulation. The joint should be opened above the patella. Observe the great extent of the fold which the synovial membrane forms above this bone. 1 It allows the free play of the bone over the lower part of the femur. The fold extends higher above the inner than the outer condyle, which accounts for the form of the swelling produced by effusion into the joint. CRUCIAL The crucial ligaments, so named because they LIGAMENTS. cross like the letter X, extend from the mesial side of each condyle to the head of the tibia. The anterior or external ligament, the smaller, ascends from the inner part of the fossa in front of the spine of the tibia, backwards and outwards to the inner and back part of the external condyle. It is attached to the tibia close to the anterior termination of the external semilunar cartilage. The posterior or internal ligament, best seen from behind, ex- tends from the back of the fossa behind the spine of the tibia, and from the posterior termination of the external semilunar cartilage, upwards, forwards, and inwards to the front of the inner condyle. The direction of this ligament is more vertical than the anterior one. j T Between the condyles and the articular surfaces LAB OK SEMI- of the tibia are two incomplete rings of fibro- LUNAK FIBKO- cartilage, shaped like the letter C. They serve CARTILAGES. ^ The movements which take place between the articulations are those of flexion, extension, abduction, and adduction. PHALANGEAL These articulations have the same kind of liga- ARTICULATIONS. ments as the preceding, and the movements are also nearly identical. 715 DISSECTION OF THE BRAIN. BEFORE passing on to the examination of the Jprain, the student MEMBRANES should study the arrangement, the structure, and OF THE BRAIN. foe uses of the three membranes by which the brain is enveloped. The most external one, the dura mater, has been described (p. 8). The second, or intermediate one, is a serous membrane, termed the arachnoid ; the third, the pia mater, is a vascular layer, and is in contact with the encephalon. ARACHNOID The arachnoid membrane, 1 the second invest- MEMBRANE. ment, constitutes the smooth polished membrane covering the surface of the brain, and is exposed after the removal of the dura mater. This tunic was formerly considered by anato- mists to be an example of an ordinary serous membrane, and was described as consisting of two layers an external or parietal, which lined the inner surface of the dura mater, and an internal or visceral, which was reflected over the brain. It is now regarded as consisting of one layer only viz., the one which envelopes the brain ; the under aspect of the dura mater being covered only with a layer of flattened epithelium cells. The cavity which was formerly described as the cavity of the arach- noid, is now called the subdural space, and contains a very limited amount of fluid. The arachnoid membrane is a colourless and transparent layer, and is spread uniformly over the surface of the brain, from which it is separated by the pia mater. It does not, like the pia mater, dip down into the furrows between the convolutions of the brain, and it is more or less connected with the pia mater by delicate connective tissue, the subarachnoid. On account of its extreme a spider's web ; elSos, form. 716 SUBARACHNOID SPACES. tenuity, and its close adhesion to the pia mater, the two membranes cannot be readily separated ; but there are places, especially at the base of the brain, termed subarachnoid spaces, where the arachnoid membrane can be seen distinct from the subjacent pia mater. The two membranes can be artificially separated by blowing air beneath the arachnoid with a blow-pipe. SUBAEACHNOID Wherever the arachnoid membrane is separated SPACES AND FLUID, from the pia mater, a serous fluid (cerebro-spinal) intervenes, contained in the meshes of a very delicate areolar tissue. The spaces between these membranes are termed subarachnoid, and are very manifest in some places. For instance, there is one well- marked space in the longitudinal fissure, where the arachnoid does not descend to the bottom, but passes across the edge of the falx cerebri, a little above the corpus callosum. At the base of the brain, there are two of considerable size : one, the anterior sub- arachnoid space, is situated between the anterior border of the pons Varolii, the middle, and the anterior cerebral lobes ; the other, the posterior subarachnoid space, is placed between the cerebellar hemi- spheres and the medulla oblongata. The fluid in the subarach- noid space communicates with the fluid of the general ventricular cavities of the brain through an aperture (foramen of Magendie) in the fourth ventricle, close to its lower boundary ; and also through an opening, on each side, behind the glosso-pharyngeal nerves. In the spinal cord, also, there is a considerable interval containing fluid between the arachnoid and the pia mater. The purpose of this fluid is, not only to fill up space, as fat does in other parts, but mechanically to protect the nerve-centres from the violent shocks and vibrations to which they would otherwise be liable. The brain, therefore, may be said to be supported in a fluid, which insinuates itself into all the inequalities of the surface, and surrounds in fluid sheaths all the nerves as far as the foramina through which they pass. This fluid sometimes escapes through the ear, in cases of fracture through the base of the skull, involving the meatus auditorius internus and the petrous portion of the temporal bone. The arachnoid is supplied with filaments from the motor root of the fifth, the facial, and the spinal accessory nerves. PIA MATER. 717 The cerebro-spinal fluid varies in amount from two drachms to two ounces. It is a clear, limpid fluid, slightly alkaline, contain- ing 98 - 5 parts of water, and 1*5 parts of solid matter. The cere- bro-spinal fluid of the encephalon and that of the spinal cord communicate. This, the immediate investing membrane of the PIA MATER brain, is extremely vascular, and composed of a minute network of blood-vessels held together by delicate con- nective tissue. It covers the cerebral surface, and dips into the fissures between the convolutions, forming a double layer. From its internal surface numerous vessels pass off at right angles into the substance of the brain. 1 The pia mater sends a prolongation through the transverse fissure into the lateral and third ventricles, forming the velum interpositum and the choroid plexuses, and also another along the roof of the fourth ventricle, forming the tela cJwroidea inferior. Upon the surface of the cerebellum, the pia mater is thinner, not so vascular, and only sends prolongations down the larger sulci ; on the pons Varolii and the medulla, the membrane is more fibrous and much less vascular than elsewhere. The pia mater is supplied with nerves by the third, fifth, sixth, facial, glosso-pharyngeal, pneumogastric, spinal -accessory, and sympathetic nerves, which chiefly accompany the blood-vessels forming the pia mater. ARTERIES OP The brain is supplied with blood by the two THE BRAIN. internal carotid and the two vertebral arteries. INTERNAL This artery enters the skull through the carotid CAROTID. canal in the temporal bone, and ascends very tor- tuously, by the side of the body of the sphenoid, along the inner wall of the cavernous sinus. It appears on the inner side of the anterior clinoid process, and, after giving off the ophthalmic, divides into an anterior and middle cerebral, posterior communicating and anterior choroid arteries. a. The anterior cerebral artery is given off from the internal carotid at the inner end of the fissure of Sylvius. It passes forwards and in- wards to reach the longitudinal fissure between the hemispheres, curves 1 Owing to these vessels, the pia mater, when placed in water, presents a floccu- lent, woolly appearance, and hence it is sometimes called tomentum cerebri. 718 ARTERIES OF THE BRAIN. round the front part of the corpus callosum, then runs backwards over its upper surface (under the name of the artery of the corpus callosum), and terminates in branches which anastomose with the posterior cerebral arteries." The anterior cerebral arteries of opposite sides run side by side, and supply the olfactory lobes, the optic nerves, the frontal lobes, FIG. 170. Olfactory bulb . . . Second pair or optic nerves Locus pert oratus anticus. Tractus options . . Crus cerebri . . . Third pair of nerves Fourth pair of nerves Fifth pair of nerves . Sixth pair of nerves . Pyramid Olive . Vertebral artery . . Anterior spinal a. Anterior cerebral a. Lamina cinerea. Middle cerebral a. Tuber cinereum. Mammillary body. Locus perforates medius. Posterior cerebral a. Superior cerebellar a Pons Varolii. Inferior cerebellar a. Seventh ) pair of Eighth. J nerves. Tenth }P*"* Eleventh J nerves - .Twelfth pair of nerves. Cerebellum. the anterior perforated spaces, and the corpus callosum. At the base of the brain, as they enter the longitudinal fissure, they are connected by a short transverse branch, called the anterior communicating artery (fig. 170). 6. The middle cerebral artery, the largest branch of the internal ARTERIES OF THE BRAIN. 719 carotid, runs outwards deeply within the fissure of Sylvius, and divides into many branches distributed to the anterior and middle lobes. Near its origin it gives off a number of small arteries, which pierce the locus perforatus anticus to supply the corpus striatum. c. The posterior cotiimunicating artery, unequal in size usually on the two sides, proceeds directly backwards to join the posterior cerebral ; thus establishing at the base of the brain the free arterial inosculation called the circle of Willis. d. The anterior choroid artery, a small branch of the internal carotid, arises external to the posterior communicating artery. It runs back- wards, and enters the fissure at the bottom of the middle horn of the lateral ventricle, to terminate in the choroid plexus of that cavity. It supplies, in addition, the hippocampus major and the corpus fimbriatuin. VERTEBRAL This artery, a branch of the subclavian in the AKTEKY. first part of its course, enters the foramen in the transverse process of the sixth cervical vertebra, and ascends through the transverse processes of the cervical vertebrae. It then winds backwards along the arch of the atlas, and enters the skull through the foramen by perforating the posterior occipito-atlantal ligament and the dura mater. It then curves round the medulla oblongata between the hypoglossal nerve and the anterior root of the first cervical nerve. At the lower border of the pons Varolii the two arteries unite to form a single trunk the basilar which is lodged in the groove on the middle of the pons, and bifurcates at its upper border into the posterior cerebral arteries. Each vertebral artery, before joining its fellow, gives off : a. Lateral spinal branches, which enter the spinal canal, to supply the spinal cord and its membranes, and the bodies of the cervical vertebrae. 6. Muscular branches to the deep muscles of the neck, which ana- stomose with the occipital and deep cervical arteries. c. A posterior meningeal branch, distributed to the posterior fossa of the skull. d. Anterior and posterior spinal arteries, which are given off im- mediately before the vertebral arteries join to form the basilar, run along the median fissures of the front and the back surfaces of the spinal cord, and anastomose with the spinal branches of the ascending cervical arteries. 720 ARTERIES OF THE BRAIN. e. The jwsterior inferior cerebellar artery, sometimes a branch of the basilar, but more frequently of the vertebral, passes backwards between the spinal-accessory and the pneumogastric nerves, to the under surface of the cerebellum. It divides into two branches : an outer, which ramifies on the lower surface of the cerebellum as 1 far as its outer border ; and an inner, which passes to the vallecula between the two hemispheres, and supplies branches to the fourth ventricle. The basilar artery, formed by the junction of the two vertebral, in its course along the pons, gives off on each side : a. Transverse branches which pass outwards on the pons : one, the internal auditory, enters the meatus auditorius internus with the audi- tory nerve, to be distributed to the internal ear on each side. b. The anterior inferior cerebellar, which supplies the front part of the lower surface of the cerebellum, and anastomoses with the other cerebellar arteries. c. The superior cerebellar arteries, given off near the bifurcation of the basilar, are distributed to the upper surface of the cerebellum, and anastomose with the inferior cerebellar ; branches are supplied to the pineal body, the valve of Vieussens, and the velum interpositum. d. The posterior cerebral arteries are the two terminal branches into which the basilar artery divides. They run outwards and backwards, in front of the third cranial nerve, and wind round the crura cerebri to the under surface of the posterior cerebral lobes, where they divide into numerous branches for the supply of the brain, anastomosing with the anterior and middle cerebral arteries. Shortly after their origins they receive the two posterior communicating arteries from the internal carotids. Each gives off small branches to the posterior perforated space, and also the small posterior choroid artery, which, passing beneath the posterior border of the corpus callosum and fornix, is distributed to the velum interpositum and choroid plexus. CIECLE OF This important arterial inosculation (fig. 170) WILLIS. takes place between the branches of the two in- ternal carotid and the two vertebral arteries. It is formed, laterally, by the two anterior cerebral, the two internal carotid, and the two posterior communicating arteries ; in front, it is completed by the anterior communicating artery ; behind, by the two posterior cere- bral. The tortuosity of the large arteries before they enter the THE CEREBRAL CIRCULATION. 721 brain serves to mitigate the force of the heart's action ; and the circle of Willis provides a free supply of blood from other vessels, in case any accidental circumstance should stop the flow of blood through any of the more direct channels. 1 PECULIARITIES Besides the circle of Willis, there are other OF THE CEREBRAL peculiarities relating to the circulation of the CIRCULATION. blood in the brain : namely, the length and tor- tuosity of the four great arteries as they enter the skull ; their passage through tortuous bony canals ; the spreading of their rami- fications in a very delicate membrane, the pia mater, before they enter the substance of the brain ; the minuteness of the capillaries, and the extreme thinness of their walls; the formation of the venous sinuses (p. 10), which do not accompany 'the arteries; the chordae Willisii in the superior longitudinal sinus ; the absence of valves in the sinuses; and the confluence of no less than six sinuses, forming the torcular Herophili, at the internal occipital protuberance. GENERAL DIVI- F -"^ ie mass of nervous substance contained within SIGN OF THE the cranial cavity, comprised under the common BRAIN, term brain (encephalon), is divided into four parts. The cerebrum forms the largest portion, and occupies the whole of the upper part of the cranial cavity ; its base resting on the an- terior and middle fossae and the tentorium cerebelli. It is con- nected with the pons Varolii by two white nerve-masses, the crura cerebri, and with the cerebellum by two white cords, the crura cerebelli. The cerebellum, or smaller brain, occupies the space between the tentorium cerebelli and the inferior occipital fossae. The pons Varolii is the quadrilateral mass of white fibres which rests upon the basilar process of the occipital bone. The medulla 1 In many of the long-necked herbivorous quadrupeds a provision has been made in the disposition of the internal carotid arteries, for the purpose of equalising the force of the blood supplied to the brain. The arteries, as they enter the skull, divide into several branches, which again unite and form a remarkable network of arteries, called by Galen, who first described it, the ' rete mirabile.' The object of this evidently is to moderate the rapidity with which the blood would otherwise enter the cranium in the different positions of the head, and thus preserve the brain from those sudden influxions to which it would under other circumstances be continually exposed. 3A 722 MEDULLA OBLONGATA. oblongata is the portion below the pons, which is continuous below with the spinal cord and rests upon the lower part of the basilar process of the occipital bone. The result of a large number of observations shows that the weight of the brain averages in males 49^ oz., and in females about 44 oz. ; although it has been known to weigh as much as 64 oz., as in the case of Cuvier's brain, and as little as 23 oz., in the case of an idiot's brain. The following are the weights of the various portions of the encephalon which have been carefully collated by Dr. J. Reid. 1 MALE FEMALE oz. drs. oz. drs. Cerebrum 43 15J 38 12 Cerebellum 54 4 12 Pons and medulla oblongata . . . 15| 1 OJ Total 50 3 44 8J The average specific gravity of the brain is about 1036 : that of the white matter being 1040, and that of the grey 1034. The relative proportion of the amount of white to grey matter is, 64 per cent, of white substance to 36 per cent, of grey matter. The weight of the encephalon varies greatly in different sub- jects, and although its weight seems to bear some proportionate relation to the intellectual power, yet in many instances there appears to be no such definite relation. The brain weight gradually increases up to the age of forty, when it attains its maximum ; after this period the weight decreases at the rate of one ounce for every additional ten years of life. MEDULLA OBLONGATA. The medulla oblongata is that part of the cerebro-spinal axis which is placed below the pons Varolii, and is continuous with the spinal cord on a level with the upper border of the atlas. It is slightly pyramidal in shape, with the broad part above. It lies on the basilar groove of the occipital bone, and descends obliquely 1 Reid, London and Edinburgh Monthly Journal of Medical Science, April 1843. MEDULLA OBLONGATA. 723 backwards through the foramen magnum. Its posterior surface is received into the fossa (vallecula) between the hemispheres of the cerebellum. It is about an inch and a quarter in length, three quarters of an inch at its broadest part, and half an inch in thick- ness. In front and behind, the medulla is marked by a median fissure, the anterior and posterior median fissures, which are the continuations of the median fissures of the spinal cord. The anterior ends, below the pons Varolii, in a cul-de-sac, termed the foramen ccecum, and is occupied by a process of pia mater. The FIG. 171. 1. Gasserian ganglion. 2. Motor root of the fifth n. 3. Third n. 4. Arciform fibres. C. Crus cerebri. P. V. Pons Varolii. P. Anterior pyramid. O. Olive. B. Bestiform tract or body. 5. Sensitive root of the fifth n. 6. Sixth n. 7. The seventh and eighth nerves. 8. The ninth, tenth, and eleventh nerves. 9. Twelfth or hypoglos- saln. DIAGRAM OF THE FRONT SURFACE OF THE MEDULLA OBLONGATA. posterior runs along the floor of the fourth ventricle as a shallow median groove. The surface of the medulla is marked out on each side into four longitudinal columns, which receive the following names, from before backwards : the anterior pyramids, the lateral tracts and the olivary bodies, the restiform bodies, and the posterior pyramids. The anterior pyramids are two columns of white matter, narrow 3 A 2 724 MEDULLA OBLONGATA. below, but increasing gradually in breadth as they ascend towards the pons. At this part they become constricted, and may be traced through the pons into the crura cerebri. The fibres of which they are in the main composed are derived from the anterior columns of the spinal cord, and consist therefore of motor fibres. On separating the pyramids about an inch below the pons, bundles of nerves are seen decussating across the anterior fissure (fig. 171). This de- cussation, which consists of three or four bundles on each side, involves only the inner fibres of the pyramid; the outer fibres ascend through the pons without crossing. The decussating fibres are the continuations upwards of the deep fibres of the lateral pyramidal tract and the lateral columns of the cord, which here come forwards to the surface, and push aside the anterior pyramids. Thus it will be seen that the thickness of the anterior pyramids is mainly due to these decussating bundles ; that the fibres on the outer side of the pyramids are those continued upwards from the anterior column of the cord ; and that the inner part is made up of the fibres of the lateral tract of the opposite side. This decussation explains the phenomenon of cross paralysis, i.e. when one side of the brain is injured, the loss o motion is manifested on the opposite side of the body. 1 The olivary bodies are the two oval eminences situated on the outer side of the upper part of the anterior pyramids, from which they are separated by a shallow depression. They do not ascend quite as high as the pons, for there is a deep groove between them. They consist externally of white matter ; and at their lower part, some white fibres maybe observed arching round from the anterior median fissure, constituting the arciform fibres of Rolando. In the groove between the anterior pyramids and these bodies are seen the fasciculi of the hypoglossal nerve emerging from the medulla, and in the groove behind the olive emerge the roots of the glosso- pharyngeal, the pneumogastric, and spinal-accessory nerves. The lateral tracts, situated on the outer side of the anterior pyramids, are the continuations upwards of the lateral columns of 1 The phenomenon of cross paralysis of sensation is explained by the fact, made out by Brown-S6quard, that the paths of sensory impressions cross each other in the grey matter of the cord. MEDULLA OBLONGATA. 725 the spinal cord. As described, the greater number of their fibres pass across the anterior median fissure to the opposite anterior pyramid ; but some ascend as far as the lower border of the olivary body, where they divide, a few passing in front of, but the larger part passing behind this body in their course to the brain. The restiform 1 bodies are the broadest and thickest of the columns of the medulla. They are situated to the outer side and behind the lateral tracts and the olivary bodies. They are the continuations upwards of the posterior columns of the spinal cord, and as they ascend, they diverge and pass into the cerebellum, FIG. 172. DIAGRAM OF THE FOURTH VENTRICLE AND RESTIFORM BODIES. 1. Thalamus options. 4. Processus a cerebello ad testes. 2. Nates and testes, or corpora quadrigemina. 5. Restiform bodies diverging. 3. Origin of fourth nerve. 6. Origins of eighth or auditory nerve. constituting its inferior peduncles (fig. 172). Owing to this divergence, the grey matter of the medulla is exposed, so that the floor of the fourth ventricle (of which the restiform bodies and the posterior pyramids assist in forming the lateral boundaries) is mainly composed of grey matter. Near the commencement of each 1 From restis, a rope. 726 MEDULLA OBLONGATA. restiform body there is easily recognisable an eminence interposed between the restiform body and the groove which separates it from the lateral tract; this eminence, narrow at first, is known as the funiculus of Rolando, but it soon enlarges to form a considerable prominence, .called the tubercle of Rolando. The restiform body on a transverse section is wedge-shaped, and hence it is sometimes called the funiculus cuneatus ; near the level where the two bodies diverge, each presents an enlargement, known as the cuneate tuber- cle. The restiform bodies consist, as before said, of white fibres derived from the posterior and lateral columns of the cord ; in its interior is some grey matter continuous with that in the posterior part of the cord. The posterior pyramids (funiculi graciles) are two slender white columns on each side of the posterior median fissure, and are the continuations upwards of the posterior median columns of the spinal cord. Ascending, they diverge and thus form the apex of the fourth ventricle. At their point of separation the posterior pyramids enlarge, and form the clava ; after which they rapidly taper off, and run up on the inner side of the restiform bodies, which however they soon leave, and are continued upwards into the cerebrum, along the floor of the fourth ventricle. Emerging from the anterior median fissure may be noticed some superficial transverse white fibres, which cross over the anterior pyramids and the lower extremity of the olivary bodies ; these are known as the arciform fibres of Rolando (fig. 171), and they pass upwards to join the restiform body. They are probably connected with white fibres which run horizontally, constituting an imperfect septum between the two halves of the medulla, and may be seen when a longitudinal section is carefully made through its middle. The majority of these septal fibres enter the olivary bodies, and then emerging through the grey matter of the corpus dentatum, become continuous with the fibres of the restiform bodies and lateral tracts ; others pass out from the posterior fissure and wind round the restiform bodies. These latter fibres are the trans- verse strice, seen on the floor of the fourth ventricle, some of which form the roots of the auditory nerves. The lower portion of the fourth ventricle can now be seen, STRUCTURE OF THE MEDULLA. 727 bounded laterally by the diverging posterior pyramids and the restiform bodies, the floor being formed by the grey matter of the medulla. As only part, however, can be examined in the present stage, the full consideration of the fourth ventricle is deferred to a later stage in the dissection of the brain (p. 771). MINUTE STKUC- These are among the most complicated parts of TUBE OF THE the central nervous system. They contain white MEDULLA an d grey matter intermixed. The white matter consists, in part, of the continuation upwards of the longitudinal fibres of the cord ; in part, of horizontal fibres. ANTERIOB The anterior columns of the cord (fig. 173), PYBAMIDS. having reached the lower part of the medulla oblongata, are not continued straight through it, but diverge from each other, being reinforced by the deep fibres of the lateral columns, which here cross over and form the decussation of the anterior pyramids. In their further progress the fibres of the anterior columns are arranged thus : some of them run up and form the outer portion of their own pyramid ; some of them pass deeply beneath the pyramid to constitute the longitudinal fibres of the reticularis alba ; these fibres are continued upwards into the cerebrum : some ascend beneath the olive to join the restiform body and thence to the cerebellum ; another and larger fasciculus passes upwards and, after embracing the olive, reunites to form a single bundle ; this, joined by fibres (olivary fasciculus) from the olive, ascends under the name of the fillet of Reil, over the superior crus of the cerebellum, to pass to the corpora quadrigemina and the cerebral hemispheres (fig. 173). LATEBAI. The lateral columns on reaching the medulla TKACTS. are disposed of in three ways, as follows : some of its fibres, the internal, come forward between the diverging anterior columns, decussate in the middle line, and form part of the pyramid of the opposite side ; others, the external, ascend with the restiform body (or tract) to the cerebellum ; a third set, the middle, ascend beneath the olivary body, along the floor of the fourth ventricle (concealed by its superficial grey matter) as the fasciculus teres, and are continued along the upper part of the crus cerebri into the corpora quadrigemina and optic thalamus. 728 STRUCTURE OF THE MEDULLA. OLIVARY The olivary bodies are composed externally of BODIES. white matter ; but if a transverse section be made into them, their interior presents an undulating line of yellowish- brown colour, called, from its zigzag shape, the corpus dentatum or the nucleus of the olivary body. It forms an interrupted circle, incomplete at its upper and inner side, so that it allows the entrance of a bundle of white fibres olivary peduncle from the medulla behind the anterior pyramid. The peduncular fibres pass in various directions : some pass into the grey matter ; some pass through it and join the restiform body, under the name of the internal arcuate fibres ; and some passing between the fibres over the olivary body, come to the surface and curve round it, forming the external arcuate fibres. Two other isolated grey nuclei may be recognised in this transverse section, one on the inner side FIG. 173. 1. Anterior column. 2. Lateral column. 3. Posterior column. 4. Posterior median column of the spinal cord. 5. Anterior pyramid. 6. Eestiform body. 7. Posterior pyramid. 8. Fasciculus teres. 9. Inferior cms of the cere- bellum. 10. To the corpora quadri- gemina. 11. Crus cerebri. DIAGRAM OF THE COURSE OF THE FIBRES THROUGH THE MEDULLA OBLONGATA. of, and the other behind the corpus dentatum : these, called the accessor?/ olivary nuclei, are linear in shape, and are about a line in length; the root-fibres of the hypoglossal nerve pass between the inner nucleus and the corpus dentatum, to emerge between the anterior pyramid and the olivary body. EESTIFORM The posterior columns are continued upwards BODIES. under the name of the restiform bodies along the GEEY MATTER OF THE MEDULLA. 729 back of the medulla. At the apex of the fourth ventricle they diverge from each other and receive bundles of accessory fibres from the anterior pyramids and the lateral tracts, and are con- tinued partly into the cerebellum, forming its inferior crura, and partly as the fasciculi tereies along the floor of the fourth ventricle into the cerebrum. POSTERIOR The posterior pyramids are the continuations PYRAMIDS. upwards of the posterior median columns of the spinal cord ; and, like the restiform body, each divides into two fasciculi, one of which ascends and helps to form the inferior crus of the cerebellum, the other runs up with the fasciculus teres. SEPTUM OR The horizontal fibres in the medulla oblongata BAPH& were first accurately described by Stilling and Rolando, and subsequently by Clarke and others. Some of them form a septum and divide the medulla oblongata into symmetrical halves ; some run longitudinally and others obliquely. The fibres which run from the dorsal to the ventral surface of the medulla fibres rectos, pass outwards, in front, from the anterior median fissure, and are continuous with the superficial arched fibres of Rolando ; while, behind, they are continuous with the fibres of the fasciculi graciles and their grey nuclei. The longitudinal fibres run vertically and are derived from the arcuate fibres and the fibrse rectae which have altered their direction. The oblique fibres consist of the deep arcuate fibres which enter, or come out of the septum, and then pass to the outer part of the medulla. Some fibres, again, are transverse commissural fibres, and pass into the opposite anterior pyramid or the formatio reticularis, 1 and eventually assume a longitudinal direction. GREY MATTER Although in the lower part of the medulla the OF THE MEDULLA, grey matter in its interior is arranged in the same way as it is in the spinal cord, yet owing to the course of the de- cussating fibres of the lateral tracts which break up the anterior grey cornua in front, and to the diverging restiform bodies and posterior pyramids behind, the grey matter in the upper two-thirds 1 The formatio reticularis comprises the anterior and lateral parts of the medulla, and consists of intersecting fibres which cross each other at right angles, some being longitudinal and some transverse in their direction. 730 .GREY MATTER OF THE MEDULLA. of the medulla, becomes altered both in appearance and in arrange- ment. The grey matter of the anterior cornua soon loses its charac- teristic arrangement, as it becomes detached from the main part of the grey matter by the passage through it of bundles of the white fibres of the medulla. At the lower part of the olivary body, it is pushed backwards and outwards in consequence of the increase of the anterior pyramids and the olivary bodies, so as to lie in the lateral part of the medulla, just in front of the posterior horn, and constitutes a grey nucleus called the nucleus lateralis. The larger portion of the grey matter of the anterior cornu is inter- sected by white fibres and becomes broken up into an interlacement of fibres and nerve-cells, forming the formatio reticularis. The grey matter of the posterior cornua becomes largely in- creased in the upper part of the medulla. At first the posterior cornua are pushed outwards by the restiform bodies, and subse- quently by the posterior pyramids, so that they lie at right angles to the posterior median fissure. At the same time the caput cornu posterioris enlarges, and later on forms a prominent grey mass, the tubercle of Rolando, which becomes separated from the chief part of the grey matter by being intersected by transverse and longitudinal white fibres. Internal to the tubercle of Rolando, there are situated masses of grey matter in the restiform bodies and the posterior pyramids, constituting their nuclei. Higher up on a level with the middle of the olivary body, we find internal to the grey matter of the posterior pyramid (nucleus gracilis) the nuclei of origin of the two portions of the pneumogastric nerve, and of the hypoglossal nerve, the latter being nearest the middle line. The central canal gradually approaches the posterior surface of the medulla, and above the middle of it opens out to form the median groove in the floor of the fourth ventricle. On each side of the groove we find a collection of grey matter which enlarges in the upper part and constitutes the nucleus teres. The nuclei of the origins of the spinal accessory, the pneumo- gastric, and the glosso-pharyngeal nerves will be described subse- quently. .PONS VAEOLII. 731 PONS VAEOLII. The pons Varolii, or tuber annulare, is the convex eminence of transverse white fibres (fig. 171), which is situated at the base of the brain immediately above the medulla oblongata. It rests upon the basilar groove of the occipital and the sphenoid bones, and in its antero-posterior diameter measures rather more than an inch. Its upper margin is convex and well defined, and arches over the crura cerebri ; the lower, also well defined, is nearly straight, being separated from the medulla by a transverse groove. Laterally, the pons becomes narrower, in consequence of its transverse fibres being more closely aggregated ; these enter the' anterior and under part of the cerebellum, constituting its middle peduncle. Along the middle runs a shallow groove, broader in front than behind, which lodges the basilar artery. If the pia mater be removed, we observe how the superficial fibres pass transversely, to connect the two hemispheres of the cerebellum. Throughout the mammalia the size of the pons bears a direct ratio to the degree of development of the lateral lobes of the cerebellum ; therefore it is larger in man than in any other animal. 1 The pons consists of four layers of alternating transverse and longitudinal white fibres, intermingled with more or less grey matter, which is chiefly found on its upper surface, where it forms part of the floor of the fourth ventricle. The superficial layer of white fibres is transverse, connecting the cerebellar hemispheres ; the middle fibres pass transversely across, the inferior ascend slightly, while the superior pass back- wards and outwards to enter the cerebellum. The second layer consists of longitudinal fibres which are the continuation of the fibres of the medulla oblongata in their passage to the cerebrum. It is mainly composed of fibres derived from the anterior pyramids which pass up to form the superficial fibres, crusta, of the crura cerebri. 1 Birds, reptiles, and fishes have no pons, as there are no lateral lobes to the cerebellum. 732 THE CEREBRUM. The third layer is formed of transverse fibres, which from their peculiar arrangement take the name of trapezium ; the fibres in their course outwards pass round in front of the superior olivary nuclei, then across the fasciculi of the facial nerves, and lastly in front of the ascending roots of the fifth nerves to enter the middle peduncle of the cerebellum. The deepest and uppermost layer is composed of longitudinal nerve-fibres : those derived from the olivary fasciculi divide into two bundles, one ascending to the corpora quadrigemina, the other passing to the cerebrum ; and those derived from the lateral and posterior columns of the cord, which, with a fasciculus from the fillet, form the fasciculi teretes in the floor of the fourth ventricle, and pass upwards to form the tecjmenta, or deeper portions of the crura cerebri. The grey matter is chiefly aggregated at the posterior part of the pons, and varies in thickness in different sections. Thus a section through the middle of the pons will show the following nuclei of grey matter, beginning from the central groove and passing outwards ; a small intermediate portion of the facial nerve, the large nucleus of the sixth, the facial nerve, the large superior nucleus of the auditory nerve ; while below we notice the superior olivary nucleus, the nucleus of the facial nerve, and externally the grey substance of Rolando, enclosing the ascending root of the fifth nerve. The pons, like the medulla oblongata, has an imperfect median septum, composed of horizontal fibres, some of which at the anterior border surround the crura cerebri. THE CEKEBEUM. The cerebrum in man is so much more developed than the other parts of the encephalon that it completely overlies them, and forms by far the largest portion. It is oval in form, and convex on its external aspect. It is divided in the middle line into two symmetrical parts, termed the right and left hemispheres, by the deep longitudinal fissure, which is occupied by the falx cerebri THE CEREBRUM. 733 FIG. 174. (p. 9). 1 The cerebrum is composed of numerous parts certain internal ganglionic masses, the corpora striata, optic thalami, and corpora quadrigemina ; of commissural white fibres, the fornix, corpus callosum, and the commissures of the third ventricle ; of the pineal and pituitary bodies ; and, lastly, of the two lateral hemispheres, which overlie and conceal the parts pre- viously mentioned. The cerebrum rests upon the anterior and middle fossas of the base of the skull, and the tentorium cerebelli. There are three surfaces to each hemisphere : an external or convex ; an inner or median ; -viz., of DIAGRAM OF THE GENERAL DIVISIONS OF THE BRAIN. 1, 2, 3. Anterior, middle, and poste- rior lobes of the cerebrum. 4. Cerebellum. -, .,,... , T -i .-. ,. 5. Pons Varolii. and an inferior, interrupted by the nssure 6 . Medulla obiongata. of Sylvius. By widely separating the two hemispheres at the longitudinal fissure (the brain being in its natural position), we discover that they are connected in the middle by the transverse white com- missure, called the corpus callosum. In front of, and behind this mass, the longitudinal fissure extends to the base of the brain. The cerebral hemispheres, viewed from above, form an ovoid mass, broader in front than behind, and convex to correspond with the vault of the calvarium. Their surface is mapped out by tor- tuous eminences termed convolutions (gyri), separated from each other by deep furrows (sulci), which extend to a variable depth. Many of the sulci are occupied by large veins in their course to the sinuses ; others are filled with subarachnoid fluid. The convolu- tions are folds of the brain, and their outer surface consists of grey matter, so that the extent of the grey substance is thus very largely 1 Examples are occasionally met with, where the longitudinal fissure is not exactly in the middle line, the consequence of which want of symmetry is, that one hemisphere is larger than the other. Bichat (Recherches physiologiques sur la Vie ki la Mort, Paris, 1829) was of opinion that this anomaly exercised a deleterious influence on the intellect. It is remarkable that the examination of his own brain after death went to prove the error of his theory. 734 THE CEKEBRUM. increased ; the grey matter here is called the cortical substance. The interior of the convolutions consists of white nerve substance. The convolutions are not symmetrical on both sides, although they follow a somewhat similar arrangement. The number, arrange- ment, and depth of the convolutions vary somewhat in different individuals, and, to a certain extent, may be considered an index of the degree of intelligence. 1 The depth of the sulci between the convolutions varies in different brains, from an inch to half an inch ; hence it follows that two brains of equal size may be very unequal in point of extent of surface for the grey matter, and therefore in amount of intellectual capacity. Under the microscope the cortical layer is seen to con- sist of four layers two of grey alternating with two of white the external layer being always white. These layers are not equally thick in all situations, and in some parts six layers may be demon- strated, owing to the interpolation of a layer of white substance in the outer stratum : these are chiefly seen near the corpus callosum and in the occipital lobe. 2 Some of the sulci, from their depth, regularity, and early period of development, are termed the primary or interlobar fissures, and map out the surface of the cerebrum into five lobes. Of these sulci there are three : the fissure of Sylvius, the fissure of Rolando or central fissure, and the parieto-occipital fissure (fig. 175). The fissure of Sylvius is seen on the base of the cerebrum, where it receives the lesser wing of the sphenoid bone. It begins, outside the locus perforatus anticus, as a deep triangular depression valle- cula Sylvii and then curves outwards as a deep cleft to the external surface of the cerebrum ; it divides into two rami an ascending or 1 Those who wish to investigate the cerebral convolutions in their simplest form in the lower classes of mammalia, and to trace them through their successive development and arrangement into groups as we ascend to the higher classes, should consult Leuret, Anatomic compares du Systeme Nerveux consideree dans ses Rapports avec V Intelligence, Paris, 1839 ; also Foville, Traite de I'Anat. du Systeme Nerveux, &c., Paris, 1844. The convolutions of the human brain have been described by Ecker, On the Convolutions of the Human Brain, 1873 ; and by Turner, The Convolutions of the Human Brain topographically considered, Edin. 1866. 2 For an account of these laminae, see Lock'hart Clarke, Proceedings of the Royal Society, 1863. FISSURES OF THE CEREBRUM. 735 vertical, about an inch in length, and a posterior or horizontal ramus, which passes backwards and slightly upwards, and ends at the posterior third of the cerebrum by a bifid extremity. Within the fissure, near its commencement, a series of convolutions may be VIEW OF THE CONVOLUTIONS AND FISSUBES OF THE EXTERNAL SURFACE OF THE BRAIN (LEFT SIDE). A. Fissure of Rolando. B. Fissure of Sylvius. c. Inter-parietal fissure. P.O. Parieto-occipital fissure. e.m. Calloso-marginal fissure. p. Frontal lobe. p. Parietal lobe. o. Occipital lobe. T.S. Temporo-sphenoidal lobe. A.F. Ascending frontal convolution. A. p. Ascending parietal convolution. /ii/M/a- Superior, middle, and inferior frontal convolutions, separated by the superior and inferior frontal sulci. p lt p y Superior and inferior parietal convolu- tions, separated by the inter-parietal fissure. it O x 3- Superior, middle, and inferior occi- pital convolutions, separated by the occipital fissures. f,, t x t 3 . Superior, middle, and inferior temporo- sphenoidal convolutions, separated by the supe- rior and inferior temporo-sphenoidal fissures. seen deeply placed ; these are called the gyri operti, or the island of Reil. In the fork between the two rami of the Sylvian fissure are several convolutions, which have been termed by Broca the oper- eulum of the insula. The fissure of Rolando or central fissure (fig. 175, A) runs 736 FISSURES OF THE CEREBRUM. obliquely over the outer convex surface of the hemisphere. It commences close to the longitudinal fissure about its middle, from which it is separated by the marginal convolution. It then runs obliquely downwards and forwards, and terminates a little above FIG. 176. CONVOLUTIONS OF THE UPPEK SURFACE OF THE BRAIN. A. Fissure of Rolando. A.F. Ascending frontal convolution. A.P. Ascending parietal convolution. S.M. Supra-marginal convolution, below which is the angular gyrus. P.o/. Parieto-occipital fissure. F. Frontal lobe, p. Parietal lobe. o. Occipital lobe. f \ifafv Superior, middle and inferior frontal convolutions. PD P a . Superior and inferior parietal convolu- tions. O,, O 2) O 3 . Superior, middle and inferior occipital convolutions. C.mJ. Calloso-marginal fissure. the fork of the Sylvian fissure. As seen in fig. 176, the two fissures form a V-shape, failing to be joined at the angle. The fissure is formed, in early foetal life, by a large vein, which subse- quently atrophies, and is rarely bridged over. The pariet o-occipital fissure (fig. 178, P.O.) is seen on the median CONVOLUTIONS OF THE CEREBRUM. 737 surface of the hemisphere, towards its posterior part. It begins as a deep cleft on the median surface, about half an inch behind the corpus callosum, then ascends nearly vertically, and ends on the external aspect of the cerebrum, about an inch beyond the longitudinal fissure ; this latter portion taking the name of the external parieto-occipital fissure. The fissure of Sylvius is first seen about the middle of the third month of fcetal life, and is caused by the extension back- wards, and folding upon itself, of the mantle the fissure of Rolando begins to be developed about the fifth month ; and the parieto-occipital fissure between the third and fourth month of uterine life. The primary fissures form the boundaries of the various lobes of which each hemisphere is composed. The frontal lobe is that part of the front portion of the cere- brum, bounded behind by the fissure of Rolando, below by the anterior part of the fissure of Sylvius, and on the median plane by the calloso-marginal fissure. Its inferior part rests on the anterior fossa, and is called the orMtal surface, while its convex external surface is called the frontal surface. The convolutions on its frontal surface are four in number : The ascending frontal convolution (fig. 175, A.F.) which bounds, in front, the fissure of Rolando, and is usually connected above and below the fissure with the ascending parietal convolution ; the union below forming the opercidum, the union above part of the para- central lobule ; the upper and the lower union of these two convo- lutions thus shut off the fissure of Rolando from joining the fissure of Sylvius below, and the longitudinal fissure above. The superior, middle, and inferior frontal convolutions (fig. 1 75, jfj, / 2 , / 3 ) course nearly horizontally ; the superior runs along the margin of the longitudinal fissure, the inferior along the lower border of the lobe, arching over the ascending ramus of the Sylvian fissure ; the middle is placed between these. In front of the ascend- ing frontal convolution is a vertical fissure, prcecentral sulcus, which prevents the frontal convolutions joining the former convolution. The sulci which map out the frontal convolutions are two, the superior and inferior frontal sulci. 3B 738 CONVOLUTIONS OF THE CEREBRUM. On the orbital surface there is a deep sulcus, the trwadiate sulcus, whose rami pass forwards, outwards, and backwards, mapping this surface out into internal, anterior, and posterior orbital convolu- tions (fig. 177, 2V. 8.)- On this surface also we find the olfactory lobe, lodged in a deep cleft, the olfactory sulcus (fig. 177, Olf. s.), and although it will be described under the cranial nerves, it is strictly a cerebral lobe, for it is developed as a distinct outgrowth from the anterior cerebral vesicle ; moreover, in early foetal life it possesses a cavity continuous with the general ventricular cavity of the brain. The parietal lobe (fig. 175, P) is placed between the fissure of Rolando and the external parieto-occipital fissure, and is bounded below by the horizontal limb of the fissure of Sylvius, and by a line continued from it to meet one passing down from the parieto- occipital fissure. The convolutions of the parietal lobe are three : The ascend- ing parietal convolution is bounded in front by the fissure of Rolando, and runs parallel with the ascending frontal convolution in front, which it joins above and below the fissure. The superior parietal convolution (fig. 175, p) is placed above the interparietal fissure, and courses horizontally backwards ; posteriorly it runs beneath the parieto-occipital fissure, and is con- nected with the superior occipital convolution ; this is known as the first annectent convolution ; this convolution is also seen on the median surface of the cerebrum. The inferior parietal convolution lies below the interparietal fissure, and consists of two portions : one, the supra-marginal, lies in front of the posterior ramus of the Sylvian fissure ; the other, the angular gyrus, lies behind the fissure of Sylvius, and bends over the termination of the parallel sulcus ; the angular convolution is connected behind with the occipital con- volutions by the second and third annectent convolutions. The interparietal fissure ascends at first nearly vertically, and then runs horizontally backwards from the ascending parietal con- volution. The occipital lobe (fig. 175, o) consists of the posterior part of the hemisphere behind, bounded in front by the external parieto- occipital fissure, and by a line continued from it. CONVOLUTIONS OF THE CEREBRUM. 739 The convolutions on the external surface are three : The superior, middle, and inferior occipital convolutions (fig. 175, i> 25 O a) run near ty horizontally backwards, and are separated by the superior and inferior occipital fissures ; anteriorly these convo - lutions are continuous with the parietal and temporo-sphenoidal convolutions, through the four annectent yyri. The first three have been previously described ; the lowest or fourth connects the inferior occipital with the inferior temporo-sphenoidal convolution. FIG. 177. CONVOLUTIONS OF THE BASE OF THE CEREBKTTM. 0/r'.s. Olfactory sulcus. Tr.s. Tri-radiate sulcus. U. TJncinate convolution. Cal.f. Calcarine fissure. T,, TO, TV Superior, middle, and inferior temporo-spheuoidal convolutions. There is usually a small, shallow, vertical fissure, the transverse occipital, which passes down behind the external parieto-occipital fissure. On the median plane is the cuneate lobule, which forms part of the occipital lobe, and will be described further on. The temporo-sphenoidal lobe is bounded in front and above by 3 B 2 740 CONVOLUTIONS OF THE CEREBRUM. the fissure of Sylvius and its horizontal ramus, and forms that part of the hemisphere which occupies the middle cerebral fossa. The convolutions of this lobe are three : The superior temporo-splienoidal (fig. 178, ,) is bounded above by the horizontal ramus of the Sylvian fissure, and below by the parallel fissure ; it is continuous behind with supra-marginal and angular gyri. The middle temporo-splienoidal is joined behind to the angular gyrus and to the middle occipital convolution through the third annectent gyrus ; the inferior is connected with the inferior occipital convolution through the fourth annectent gyrus. There are three fissures running from before backwards, the superior temporo-splienoidal or parallel, the middle, and the inferior. The convolutions and fissures of the median and tentorial surfaces can only be properly examined by making an antero- posterior vertical section of the brain through the longitudinal fissure. As this would spoil the brain for future demonstration, the student is recommended to examine one in which this section has been already done. The fissures to be examined on this surface are the calloso- marginal, the internal parieto-occipital, the calcarine, the collateral, and the hippocampal or dentate. The convolutions are the prsecuneus, the cuneate, the uncinate, the marginal, the gyrus fornicatus, and the dentate. The calloso-marginal fissure commences beneath the rostrum of the corpus callosum, curves in front and round the genu, and then runs nearly parallel with the anterior two-thirds of the corpus callosum ; then, changing its direction, it ascends obliquely and terminates on the external aspect of the hemisphere, where it forms a deep notch immediately behind the fissure of Rolando. The internal parieto-occipital fissure passes nearly vertically downwards, and joins the calcarine fissure at an acute angle. The calcarine fissure begins close to the posterior border of the cerebrum, and then, running nearly horizontally forwards, is joined by the preceding fissure ; it terminates a little below the posterior border of the corpus callosum. It corresponds with the hippo- campus minor in the -posterior horn of the lateral ventricle. The collateral fissure (fig. 178, Gl.f.) is situated below the CONVOLUTIONS OF THE CEREBRUM. 741 calcarine fissure, and runs parallel with it. It separates the superior and inferior occipito-temporal convolutions, and causes the eminentia collaterals in the descending horn of the lateral ventricle. The liippocampal fissure takes its origin in the posterior part of the gyrus fornicatus, and, passing downwards and forwards, it ends by forming the notch in the uncinate gyrus. It corresponds to the hippocampus major. FIG. 178. CONVOLLTIONS AND FISSURES OF THE MEDIAN AND TENTOBIAL SUBFACES OF RIGHT HEMISPHERE. f.c. Corpus callosum. A.F. Ascending frontal convolution. A.i 1 . Ascending parietal convolution. P.O. Parieto-occipital fissure. p.c. Prsecuneus or quadrate lobe. c. Cuueus. c. Calcarine fissure. C7,/. Collateral fissure. G.F. Gyrus fornicatus. cm. Calloso-marginal fissure. fi. Superior frontal or marginal convolution. o.T. Optic thalamus. P. Pituitary body. tic. Dentate convolution. to t . Gyrus occipito-temporalis lateralis. to-, Gyrus occipito-temporalis medialis. The prcecuneus, or quadrate lobule (fig. 178, P.C.), is bounded in front by the calloso-marginal fissure, behind by the internal parieto-occipital fissure. It consists of numerous convolutions, and belongs to the parietal lobe. The cuneate lobule (fig. 178, c) is triangular in shape, and is situated between the converging internal parieto-occipital and calcarine fissures. It is part of the superior occipital convolution. The f/yr us fornicatus (fig. 178, G.F.) begins in front of the locus 742 BASE OF THE BRAIN. perforatus anticus, and winds round the corpus callosum, keeping close to its upper surface. It curves round its posterior free border, and is continuous below with the uncinate gyrus. Between this convolution and the corpus callosum is a well-marked furrow, which sometimes takes the name of the ventricle of the corpus callosum. The part of the convolution that forms the boundary of this ventricle is termed the lalnum cerelri. The dentate convolution (fascia dentata, fig. 1 78, dc) is the grey convolution lying in the dentate fissure, and takes its name from the notched appearance it presents, owing to the arrangement of the choroid arteries as they pass in through the fissure into the descending horn of the lateral ventricle. The uncinate gyrus (fig. 177, u) is the anterior part of the superior occipito-temporal convolution, which ends in a peculiar hook-like process at the front of the temporo-sphenoidal lobe. The inferior occipito-temporal convolution (fig. 178, /o 4 ) is situated between the collateral and the inferior temporo-sphenoidal fissures, and runs backwards to the posterior border of the cerebrum. The marginal convolution skirts the longitudinal fissure from the locus perforatus anticus as far as the termination of the calloso- marginal fissure. It is frequently indented by secondary furrows, and usually is joined to the gyrus fornicatus. The island of Reil, or the central lolte, lies deeply in the fissure of Sylvius, not far from its commencement. It is triangular in shape, the apex being close to the anterior perforated spot, and from it radiate outwards five or six short convolutions (gyri operti), which are separated from the operculum by a deep fissure. In the normal position of the brain, it forms the floor of the lenticular nucleus of the corpus striatum. It appears very early in foetal life, and is at first very prominent, but subsequently becomes closed in by the increasing development of the temporo-sphenoidal lobe. NOMENCLATURE ^e severa l objects seen at the base of the brain OF THE PARTS AT should now be examined, proceeding in order from THE BASE OF the front (fig. 170, p. 718). In this description the cerebral nerves are omitted. These will be examined hereafter. BASE OF THE BRAIN. 743 In front we notice the triangular frontal lobes, separated from each other by the longitudinal fissure, and bounded behind by the fissure of Sylvius. In the middle line, dividing the frontal lobes, is the longi- tudinal fissure. By gently separating these lobes, we expose the corpus callosum, or the great transverse commissure which con- nects the two hemispheres of the cerebrum. Continued backwards and outwards on each side from the corpus callosum to the fissure of Sylvius is a white band, the peduncle of the corpus callosum. Extending from the corpus callosum to the optic commissure is a thin grey layer, the lamina cinerea. Between the frontal and temporo-sphenoidal lobes is the fissure of Sylvius, which lodges the middle cerebral artery. The optic commissure, formed by the union of the two optic tracts, is seen in the middle line behind the lamina cinerea. At the root of the fissure of Sylvius is the locus perforatus anticus. 1 Immediately behind the optic commissure is a slight prominence of grey matter, the tuber cinereum ; from this descends a conical tube of reddish colour, the infundibulum, to the apex of which is attached the pituitary body. Behind the tuber cinereum are two round white bodies, the corpora albicantia. Posterior to these is the locus perforatus posticus, which is bounded behind by the pons, and laterally by the two diverging crura cere- bri, two round cords of white substance, which emerge from the anterior border of the pons. Winding round the outer side of each crus is a soft white band, the optic tract. Examine now in detail the various objects above enumerated, most' of which are shown in fig. ] 70. The longitudinal fissure is visible in front, where it separates the two frontal lobes, and, by lifting up the cerebellum, it can be seen behind dividing the temporo-sphenoidal lobes. It can be more satisfactorily examined later on. The lamina cinerea is a thin layer of grey substance, which runs backwards from the termination of the corpus callosum, and passes above the optic commissure to be connected with the tuber cinereum. Laterally it is continuous with the grey matter 1 Called 2>erforatm from its being perforated by a number of blood-vessels for the supply of the corpus striatum. 744 BASE OF THE BRAIN. of the two anterior perforated spots. If the lamina be torn, which is very easily done, an opening is made into the anterior part of the floor of the third ventricle. The olfactory lobe lies in its own sulcus on the orbital surface, nearer its mesial aspect. The optic commissure is placed immediately behind the lamina cinerea. It is formed by the junction in the middle line of the two optic tracts. From it the two optic nerves can be traced, running forwards and outwards. The locus perforatus anticus is a shallow triangular depression, placed to the inner side of the commencement of the fissure of Sylvius. It is bounded in front by the two diverging white roots of the olfactory lobe, and behind by the optic tract. It is com- posed partly of grey substance, and is continuous with the lamina cinerea on the inner side. Crossing it is seen a broad white band, the peduncle of the corpus callosum. This space is pierced by a number of small apertures for the transmission of small vessels to the corpus striatum ; hence its name. The tuber cinereum (fig. 170, p. 718) is a prominence of grey matter immediately behind the optic commissure, and in front of the corpora albicantia. It forms -part of the floor of the third ventricle, and from it a conical tube of reddish colour, the infundi- bulum, descends to the posterior lobe of the pituitary body. There is a large collection of grey matter on the outer side of the tuber cinereum, and internal to the optic tract, called the basal optic ganglion, from which fibres pass to the corresponding optic tract. The pituitary body occupies the sella turcica, is of a reddish- brown colour, and consists of two lobes. Of its two lobes the anterior, and larger, is concave posteriorly to receive the pos- terior lobe, and weighs from five to ten grains. The two lobes consist of different structure, and differ in their development ; the posterior is developed downwards from the third ventricle, and is hollow ; subsequently there is a large increase of connective-tissue structure and blood-vessels in it, so that the cavity is usually obliterated. The anterior is darker, and is surrounded by a con- nective-tissue capsule ; on section it resembles in structure the thyroid gland, being composed of reticular tissue, with numerous CRURA CEREBRI. 745 cavities filled with nucleated cells and granular matter ; it is originally developed as a prolongation from the ectoderm of the buccal cavity, from which it soon becomes isolated. The corpora albicantia (inammillaria) are two round white bodies, situated behind the tuber cinereum. Each is formed by the curl upon itself of the anterior crus of the fornix, called the bulb of the fornix, which then turns backwards and upwards to end in the optic thalamus. They contain within them some grey matter, and up to the seventh month of fetal life they form one mass. The locus perforates posticus (^pons Tarini) is a depression of grey matter placed between the diverging crura cerebri and behind the corpora albicantia. Its surface is penetrated by small vessels which supply the optic thalami. From its grey substance some white fibres emerge and turn round over the crura cerebri to enter the white medullary portion of the cerebellum. The crura cerebri (fig. 170) are the two rounded masses of white matter which emerge from the anterior border of the pons Varolii, and then pass forwards and outwards to enter the anterior and inner aspect of the temporo-sphenoidal lobes. Each is about three-quarters of an inch long, and is rather broader in front than behind. On the inner side the third nerve is seen emerging from a groove (oculo-motor) in the crus, which marks the division of the crus into two portions, an upper (dorsal) and larger called the tegmentum, and a lower or ventral, called the crusta. The optic tract curves round the anterior part of each crus, and is adherent to it by its anterior border. STRUCTURE OF These are composed of longitudinal fibres, de- THE CRUKA rived from the pyramids, from part of the lateral CEREBRI. an( j res tif orm columns of the medulla, and from the grey matter in the pons Varolii. If one of the crura be divided longitudinally, there is found in the middle of it a layer of dark- coloured nerve-substance, called locus niyer, which separates the crus into an upper and lower stratum of fibres. The lower stratum (crustci) is tough and coarse, and consists of the continuation of the fibres proceeding from the pyramid and the pons. The upper stratum (teymentmn) is much softer and finer in texture; it is 746 ORIGINS OF THE CRANIAL NERVES. composed of the fibres proceeding from the lateral and restiform columns ; also from the superior crus of the cerebellum. Tracing the fibres of the crus cerebri into the cerebral hemisphere, we find that its lower fibres ascend chiefly through the corpora striata, its upper fibres through the thalami optici. In passing through these ganglia, the crus receives a large addition to its fibres : these FIG. 179. Corpus striatnm. Thalamus opticus. Crus cerebri. Locus niger. Pons Varolii, denoted by transverse lines. Pyramid. Olive. Anterior columns. Lateral columns. Posterior columns. Corpora quadrigemina. Fillet of Reil. Superior crus of the cerebellum. Cerebellum. DIAGRAM OF THE COURSE OF THE FIBRES THROUGH THE MEDULLA AND PONS. branch out widely towards all parts of the hemisphere, in order to reach the cortical substance on the surface. ORIGIN OF THE The cerelral nerves are given off in pairs, named CEREBRAL the first, second, third, &c., according to the order NERVES. j n which they appear, beginning from the front. There are twelve pairs. Some are nerves of special sense as the ORIGINS OF THE CRANIAL NERVES. 747 olfactory, the optic, the auditory; others are nerves of common sensation as the larger root of the fifth, the glosso-pharyngeal, and the pneumogastric ; others, again, are nerves of motion as the third, the fourth, the smaller root of the fifth, the sixth, the facial, the spinal-accessory, and the hypoglossal. FIRST PAIK OB These (fig. 180, i) are from their early develop- OLFACTOBY ment outgrowths from the cerebral lobes, and not, strictly speaking, nerves. The nerve is triangular NERVES. FIG. 180. 1. Olfactory lobe. 2. Optic n. 3. Crus cerebri. 4. Section of cms to show locus niger. 5. Corpus geniculatuin externum. G. Corpus geniculatnm internum. 7. Corpora quadri- gemiiia. 8. Tlialamus options. 9. Tractus opticus. 10. Corpus callosum. DIAGKAM OFTHE OKIGINS OF THE OLFACTORY AND OPTIC NERVES. on section, the apex of the triangle being lodged in a straight farrow (olfactory sulcus) in the orbital surface of the frontal lobe. It pro- ceeds straight forwards, and terminates in the olfactory bulb, which lies on the cribriform plate of the ethmoid bone. The olfactory lobe is oval, of a reddish-grey colour, and very soft consistence, owing to the large amount of grey matter con- tained in it. It gives off from its under surface about twenty 748 ORIGINS OF THE CRANIAL NERVES. branches, which pass through the foramina in the cribriform plate. 1 For description of these, see p. 277. The nerve arises by three roots an outer and an inner, com- posed of white matter, and a middle, composed of grey (fig. 180, p. 747). The outer root passes backwards and outwards as a thin white line, along the outer side of the locus perforatus anticus, to the commencement of the fissure of Sylvius. Its deeper origin has been traced to a nucleus of grey matter in the anterior part of the temporo-sphenoidal lobe. The inner root passes backwards and inwards to the posterior extremity of the internal convolution of the frontal lobe, and thence may be traced to the gyrus fornicatus. The middle or (jrey root arises from the grey matter of the sulcus in which the nerve is lodged, and from the grey matter of the locus perforatus anticus in the fork between the two white roots ; this is called the tuber olfactorium. It contains white fibres in its interior, which have been traced to the corpus striatum. SECOND PAIR The optic tracts arise from the anterior lobes OK OPTIC. (iiates) of the corpora quadrigemina, the corpora geniculata, and the posterior part of the optic thalami (p. 747, fig. 180). They wind round the crura cerebri, with which they are connected by their anterior borders, and, after receiving some fibres from the basal optic nucleus (p. 744), join in the middle line to form the optic commissure. This commissure rests upon the sphenoid bone in front of the sella turcica ; and from it each optic nerve, invested by its fibrous sheath, passes through the optic foramen into the orbit and terminates in the retina. 1 The olfactory nerve and its ganglion, as stated above, are integral parts (the prosencephalic lobe) of the brain. What in human anatomy is called the origin of the nerve is, in point of fact, the crus of the olfactory lobe, and is in every way homologous to the crus cerebri or cerebelli. In proof of this, look at the enormous size and connections of the crus in animals which have very acute sense of smell. Throughout the vertebrate kingdom there is a strict ratio between the sense of smell and the development of the olfactory lobes. Again, in many animals, these lobes are actually larger than the cerebral, and contain in their interior a cavity which communicates with the lateral ventricles. According to Tiedemann, this cavity exists even in the human totus at an early period. ORIGINS OF THE CRANIAL NERVES. 749 At the commissure some of the nerve-fibres cross from one side to the other. This decussation affects only the middle fibres of the nerve; the outer fibres pass from one optic tract to the optic nerve of the same side ; the inner fibres pass from one optic tract round to the optic tract of the opposite side ; while in front of the commissure are fibres which pass from one optic nerve to its fellow (p. 754). THIED PAIR The apparent origin of the third nerve is from OK MOTOEES the inner side of the crus cerebri, immediately in OCULOKUM. front of the pons. Some of its roots, however, pass through the locus niger and the tegmentum of the crus, to reach a nucleus of large yellow cells beneath the iter a tertio ad quartum ventriculum, extending forwards as far as the posterior commissure, and behind as far as the nucleus of the fourth nerve (see below). It runs forwards through the cavernous sinus, and, passing through the sphenoidal fissure in two divisions, supplies all the muscles of the orbit except the superior oblique and the external rectus. FOUETH PAIE The fourth nerve has its deep origin from a OB TKOCHLEAR nucleus of grey matter in the floor of the aqueduct NEEVES. o f Sylvius, beneath the corpora quadrigemina, and almost continuous superiorly with the yellow nucleus of the third nerve. The nerve fibres then run backwards, upwards, and inwards in the lateral wall of the Sylvian aqueduct, and reach the anterior part of the valve of Vieussens, where they cross over to the opposite side. The nerve then emerges from the valve of Vieussens close to the middle line, and, winding round the crus cerebri, enters the orbit through the sphenoidal fissure and supplies the superior oblique. FIFTH PAIK OK The fifth nerve is the largest of all the cranial TRIGEMINAL nerves, and consists of two roots, a larger or sensory, and a smaller or motor. It has its appa- rent origin from the outer side of the pons Varolii, and a few of the transverse fibres of this body separate the two roots of the fifth. The motor or smaller root consists of fibres which take origin from an oval grey nucleus (motor nucleus) situated in the front part of the floor of the fourth ventricle, internal to its lateral boundary ; 750 ORIGINS OF THE CRANIAL NERVES. in their passage forwards the fibres are joined by filaments from the descending 1 root of the fifth, which arise from the grey matter in the lateral wall of the aqueduct of Sylvius, beneath the anterior lobes of the corpora quadrigemina. It also receives some fibres from the raphe. The sensory and larger root arises by fibres having their origin chiefly in the superior sensory nucleus, which is situated external to the motor nucleus, and partly by fibres known as the ascending fibres, which may be traced far down in the medulla from a mass of nerve-cells in connection with the grey tubercle of Rolando and its upward prolongation. The two divisions of the nerve proceed forwards over the apex of the petrous portion of the temporal bone ; here is developed, upon the sensory root, the Gasserian ganglion. The root then divides into three branches the ophthalmic, which passes through the sphenoidal fissure ; the superior maxillary, which passes through the foramen rotundum ; the inferior maxillary, which passes through the- foramen ovale. They all confer common sensation upon the parts they supply, which comprise the entire face and sides of the head. The small motor root passes beneath the ganglion, with which it has no con- nection, and accompanies the inferior maxillary division, to be dis- tributed to the muscles of mastication. SIXTH PAIK OB The sixth nerve emerges from the transverse ABDUCENTES. groove between the pons and the anterior pyramid (p. 718), with both of which it is connected. Its deep origin can be traced to an oval grey mass of nerve-cells in the fasciculus teres in the floor of the fourth ventricle, close to the median groove and in front of the transverse striae. The nerve fibres pass downwards from their origin through the pons parallel with the septum, and emerge from the transverse groove as before stated. It leaves the skull through the sphenoidal fissure, and, passing between the two heads of the external rectus, is distributed to this muscle. SEVENTH PAIR The facial nerve or portio dura (p. 718) has its OK FACIAL apparent origin from the groove between the pons NEKVES. an( j ^j ae restiform tract, and behind the olivary body. Its deep origin may be traced to an elongated mass of grey substance, placed deeply in the floor of the fourth ventricle, between the motor nucleus of the fifth and the transverse strias. ORIGINS OF THE CRANIAL NERVES. 751 From this origin its fibres run upwards, backwards, and inwards to the floor of the fourth ventricle, and wind round the nucleus of the sixth, so as to course superficial to it in the fasciculus teres. The nerve then makes a sharp bend upon itself, and passes downwards and outwards through the pons between the superior olivary nucleus and the ascending root of the fifth nerve. A small separate fasciculus of this nerve pars intermedia lies between it and the auditory nerve, and forms connections with both ; it arises from the lateral column of the cord. The nerve enters the meatus auditorius internus. For the further description of the portio dura, see p. 44. FIG. 181. a. Superior peduncles of the cerebellum. b. Eestiform tracts. c. Posterior pyramids. d. Fasciculus teres : ex- ternal to it is the superior fovea. e. Striie acusticae. /. Fasciculus teres. y. Tuberculum acusti- cum. h. Inferior fovea. i. Cerebellum. VIEW OF THE FLOOE OF THE FOURTH VENTRICLE. EIGHTH PAIR OK AUDITORY NERVES. The auditory nerve emerges from the same groove as the preceding nerve, and is situated immediately beneath it, being separated from it only by the pars intermedia. Its deep origin is principally from the inner auditory nucleus, situated in the floor of the fourth ventricle, under the tuberculum acusticum ; this nucleus extends from beneath the acoustic tubercle to the middle of the anterior half of the floor, passing beneath the transverse striaa ; on its inner side, below, is the vagal nucleus, on its outer side is the restiform body ; from this nucleus the fibres pass outwards, and, on curving round the restiform body, are joined by some filaments 752 ORIGINS OF THE CRANIAL NERVES. from the transverse striae. A few of the filaments of the auditory nerve come from another nucleus situated in front of the medullary striae and external to the preceding nucleus, and which gets larger as it passes upwards. These two bundles unite, and the nerve passes outwards and enters the meatus auditorius internus in com- pany with the portio dura. It divides at the bottom of the meatus into cochlear and vestibular branches, which are distributed to the internal ear. NINTH PAIR OB ^he fjlosso-plianjncjeal nerve arises apparently GLOSSO-PHARYN- by several filaments from the restiform body below GEAL NEKVES. fa & au( Jitory nerve. Its deep origin is from a nucleus in the inferior fovea of the fourth ventricle, continuous behind with the vagal nucleus, and covered in front by the inner auditory nucleus. The glosso-pharyngeal nerve passes through the middle compartment of the foramen jugulare, and is distri- buted to the mucous membrane of the pharynx and back of the tongue (p. 265). TENTH PAIR OB r ^ ne pneumogastric nerve arises from a grey PNETJMOGASTRIC nucleus (divided into two by a bundle of white NEKVES. fibres), which is placed between the glosso-pharyn- geal nucleus in front and the spinal-accessory nucleus behind, in the inferior fovea. The fibres, about twelve in number, pass through the medulla, and emerge from the restiform body, below the glosso-pharyngeal, and join to form a single nerve. This passes through the foramen jugulare, separated from the preceding by a septum of dura mater, and is distributed to the pharynx, larynx, the heart and lungs, the oesophagus and stomach. ELEVENTH PAIR The spinal accessory nerve is composed of two OR SPINAL ACCES- parts : an upper or accessory portion, which arises SORY NERVES. from the medulla below the vagus ; and a lower or spinal portion, which arises from the spinal cord. The accessory fibres may be traced to the grey nucleus, which is connected in front with the vagal nucleus, and lies close to the median sulcus of the fourth ventricle, extending to the apex of the calamus scrip- torius and along the side of the central canal ; the spinal portion may be traced below to the tractus intermedio-lateralis and anterior cornu, and above to the posterior cornu, arising by slender fila- DISSECTION OF THE BRAIN. 753 ments as low down as the fifth or sixth cervical vertebra. The spinal portion ascends behind the ligamentum denticulatum, through the foramen magnum, into the skull, and joins the accessory part. The nervus accessorius then passes through the foramen jugulare with the two preceding nerves ; its accessory portion joins the pneumogastric nerve, and its spinal portion supplies the sterno-mastoid and the trapezius. The course and distribution of this nerve have been described in the dissection of the head and neck. THE TWELFTH The liypoglossal nerve arises by several filaments OR HYPOGLOSSAL from the medulla, which emerge from the groove NEEVES. between the anterior pyramid and the olivary body. Its fibres may be traced to a long grey nucleus, which forms an eminence in the floor of the fourth ventricle, in front and to the inner side of the vagal nucleus. The filaments are collected into two fasciculi, which pierce the dura mater through two aper- tures and join in the anterior condylar foramen ; it is distributed to the muscles of the tongue and the depressor muscles of the os hyoides and larynx. DISSECTION OF The brain should now be laid on its base. We THE BRAIN. first notice a median fissure, separating the cere- brum into two symmetrical hemispheres : this is the longitudinal fissure. By gently separating the hemispheres we see that the fissure extends in front and behind to the base, but that in the middle there is at the bottom a white band of nerve-substance, which is the great transverse commissure of the cerebrum, and termed the corpus callosum, upon which are seen the two anterior cerebral arteries. Slice off the hemispheres to about half an inch above the level of the corpus callosurn. The cut white surface presents an oval appearance, and is called the centrum ovale minus. The white substance is surrounded by a tortuous layer of grey matter about one-eighth of an inch in thickness. This grey substance consists of four layers two of grey alternating with two of white, the most external layer being white. In some places, chiefly at the base of the brain, six layers have been demonstrated. The white substance is spotted with red dots (puncta vasculosa) these are due to the 3c 754 CORPUS CALLOSUM. escape of blood from the divided vessels. The corpus callosum is now seen to be overlaid on each side by the gyrus fornicatus ; the border is termed the labium cerebri, and the space between the gyrus and the corpus callosum is called the ventricle of the corpus callosum. Now slice off the hemisphere down to the level of the corpus callosum, when a section is made of the white substance, called the centrum ovale majus. The corpus callosum is now well exposed. FIG. 182. FIG. 183. J U' UPPER SURFACE OF CORPUS CALLOSUM. 1,1. Lineso transversae. 2. Raphe. 3, 3. Anterior cerebral a. DIAGRAM OF LAMINA CINEREA. 1. 1. Peduncles of corpus callosum. 2. Lamina cinerea. 3. Commissure of optic nerves. CORPUS This stratum of white substance, consisting of CALLOSUM. transverse commissural fibres, is the chief con- necting medium between the two hemispheres, and is called the great transverse commissure of the cerebrum ; and moreover, on each side forms the roof of the lateral ventricles. Its surface is slightly arched from before backwards ; it is about four inches long and one inch in its greatest breadth, which is behind. Tt is rather nearer to the front than to the back part of the brain, and CORPUS CALLOSUM. 755 it is thicker at the ends than in the middle, and thicker behind than in front. A shallow groove, called the raphe, runs along the middle of its upper surface (fig. 182) ; in a fresh brain, two longi- tudinal white tracts, named strice longitudinales or the nerves of Lancisi, run parallel to it ; and external to these again are two other longitudinal fibres, strice longitudinales later ales. The sur- face of the corpus callosum is marked by transverse lines which indicate the course of its fibres ; these are the linece transversce of FIG. 184. Foramen of Monro . Middle commissure . Anterior commissure Lamina cinerea . . Optic nerve Pituitary gland Infundibulum Tuber ciuereum Corpus matnmillare Locus perforatus posticus Pons Varolii Velum interposituTrc. Thalamus opticus. Pineal gland. Posterior commissure. Nates. Iter a tertio ad euar- tum ventriculum. Valve of Vieussens. Fourth ventricle. Arachnoid membra ne (reflected). Medulla oblongata VERTICAL SECTION THEOUGH THE CORPUS CALLOSUM, AND PARTS BELOW. the old anatomists. The anterior cerebral arteries proceed along the surface of the corpus callosum to the back of the brain. The anterior part of the corpus callosum turns downwards and backwards, forming a bend called its genu. The inferior part of this bend rostrum becomes gradually thinner and nar- rower, and terminates in two peduncles, which diverge from each other, and are lost, one in. each fissure of Sylvius. Between these 3 c 2 756 LATERAL VENTRICLES. crura is placed the lamina cinerea (fig. 180). The posterior part of the corpus callosum terminates in a thick, round border the splenium which is free, and beneath it the pia mater enters the interior of the ventricles. A satisfactory view cannot be obtained of the arch formed by the corpus callosum, of its terminations in front and behind, and of the relative thickness of its different parts, without making a perpendicular section through a fresh brain, as shown in the preceding figure. 1 Connected with the under surface of the posterior part of the corpus callosum is the fornix, which separates from it in front, the two structures being connected by a vertical septum the septum lucidum (fig. 184). LATEEAL A longitudinal incision should be made on each VENTKICLES. side through the corpus callosum about half an inch from its median raphe. Care must be taken not to cut too near the middle line, in order to preserve the delicate partition which descends from the under surface of the corpus callosum, and separates the ventricles from each other. Two cavities, called the lateral ventricles, will thus be exposed, one in each cerebral hemi- sphere, and they should afterwards be laid open throughout their whole extent. Their general form should be first examined ; then the several objects seen in them. The lateral ventricles are two serous cavities, one in each hemi- sphere of the brain. They are occasioned by the enlargement and folding backward of the cerebral lobes over the other parts of the central nervous axis. They contain a serous fluid, which, even in a healthy brain, sometimes exists in considerable quantity ; when greatly in excess it constitutes one form of the disease termed hydrocephalus. The ventricles are lined with ciliated epithelium, laid upon a layer of neuroglia (ependyma) ; a term which has been applied to that peculiarly delicate connective tissue found through- out the brain and spinal cord. The ventricles are crescentic in shape, with their backs towards 1 The corpus callosum Is more or less developed in all mammalia, but is absent in birds, reptiles, and fish. It has been absent in the human subject without any particular mental deficiency. See cases recorded by Eeil, Archiv filr die Phys. t. xi., and Wenzel, De penitiori Struct. Cereb. p. 302. LATERAL VENTRICLES, 757 each other. Each consists of a central part or body, and three horns or cornua, anterior, middle, and posterior, which extend, respectively, into the frontal, temporo-sphenoidal, and occipital lobes. The body, situated in the middle of the hemisphere, is triangular in shape, and is separated from its fellow by the septum FIG. 185. VIEW OF THE LATERAL VENTRICLES FROM ABOVE AFTER THE REMOVAL OF THE CORPUS CALLOSUM. 1. Corpus striatum. 6. Hippocampus major, with, the emi- 2. Optic thalamus. nentia collateralis behind it. 3. Taenia semicircularis. 7. The corpus callosum (cut through). 4. Fornix. 8. Fifth ventricle. 5. Hippocampus minor. 9. Pes Hippocampi. 10. Choroid plexus. lucidum. Its roof is formed by the corpus callosum (fig. 186, i) ; internally, it is bounded by the septum lucidum (fig. 184) ; on the floor, beginning from the front, are seen the corpus striatum, the tcenia semicircularis, the optic thalamus, the choroid plexus, and the corpus fimbriatum ofihefornix (fig. 185). 758 LATERAL VENTRICLES. The anterior horn' extends into the frontal lobe, and as it passes forwards it diverges slightly from its fellow of the opposite side. It is triangular in shape, its roof and anterior wall are formed by the corpus callosum, and it curves round the anterior extremity of the corpus striatum. The posterior horn can be traced into the occipital lobe, where it passes at first backwards and outwards, and then, narrowing to a point, converges towards its fellow. Its roof is formed by the fibres of the corpus callosum as they pass backwards and outwards FIG. 186. TBANSVEBSE VEKTICAL SECTION THEOUGH THE BEAIN. 1. Corpus callosum. 6. Corpus mammillare. 2. Lateral ventricle. 7. Choroid plexus. 8. Third ventricle. 8. Fornix. 4. Corpus striatum. 9. Pituitary gland. 5. Thalamns opticus. from the splenium ; on its floor are seen on the inner side an eminence, the hippocampus minor, and external to it a triangular flat surface, called the pes accessorim or eminentia collateralis. 1 The middle or descending horn runs into the temporo-sphenoidal 1 The posterior horns are not always equally developed in both hemispheres, and sometimes they are absent in one or both. In the carnivora, ruminantia, solipeda, pachydermata, and rodentia, the lateral ventricles are prolonged into the largely developed olfactory lobes. This is the case in the human fostus only at an early period. SEPTUM LUCIDUM. 759 lobe, descends towards the base of the brain, making a curve, at first backwards and outwards, then downwards and forwards, and lastly inwards : the initial letters of which make the memorial word ' bodfi.' Its roof is formed by the fibres of the corpus callosum, partly by the posterior narrow extremity of the corpus striatum, with the taenia semicircularis, and the rounded extremity of the optic thalamus. On its floor are the hippocampus major, a large rounded white eminence which follows the curve of the cornu ; the pes hippocampi, the expanded paw-like extremity of the former; the eminentia collateralis on the outer side of the hippo- campus major, and part of which is seen in the posterior horn ; the corpus fimbriatum of the fornix, attached to the anterior concave border of the hippocampus major; the fascia dentata, a crimped edge of grey matter under the corpus fimbriatum; the choroid plexus; and the outer part of the transverse fissure. The various structures seen in the body and horns of the lateral ventricle will be described later on, when they are fully exposed. APPEABANCE ^ a vertical transverse section is made across ON PERPENDICULAB the middle of the brain, the lateral ventricles SECTION. would appear as represented in fig. 186. Observe that the roof and the floor are almost in actual contact, unless separated by ventricular fluid. Together with the third or middle ventricle, their shape slightly resembles the letter T. Such a section shows well the radiating fibres of the corpus callosum, the fornix, and the velum interpositum beneath it ; also the beginning of the transverse fissure at the base of the brain, between the crus cerebri and the temporo-sphenoidal lobe. If the corpus callosum be slightly raised, a thin vertical median septum, septum lucidum, will be seen, extending from the under aspect of this body to the upper surface of the fornix. SEPTUM This is a thin and almost translucent partition LDCIDUM. which descends vertically in the middle line from the under surface of the corpus callosum, and separates the anterior part of the lateral ventricles from each other. It is attached above to the corpus callosum, below to the reflected part of the corpus callosum and fornix (fig. 184). It is not of equal depth through- out. Its broadest part is in front and corresponds with the knee 760 FIFTH VENTRICLE. of the corpus callosum. It becomes narrower behind, tapering to a thin point, where the corpus callosum and the fornix become continuous. The septum consists of two layers, which enclose a space called the fifth ventricle or the ventricle of the septum (fig. 185). Each layer consists of grey matter inside and of white matter outside ; the former representing the cortical, the latter the medullary substance of the brain. The cavity is not lined with epithelium, as is the case with those ventricles developed from the cerebral vesicles. 1 FIG. 187. DIAGBAM OF THE FOKNIX. (The arrow is passed through the foramen of Monro). 1, 1. Corpora striata. 2, 2. Thalami optici. 3, 3. Anterior crura of fornix bending down to join the corpora mammillaria. 4, 4. Posterior crura of the fornix joining the hip- pocampi. 5, 5. Choroid plexus. 6, 6. Hippocampi majores. 7. Corpus callosum cut through. 8. Ventricle of septum lucidum. Cut transversely through the corpus callosum about its middle, with the septum lucidum, and turn forwards the anterior half. In this way the ventricle of the septum will be exposed. By turning back the posterior half of the corpus callosum a view is obtained of the fornix. This proceeding requires care, or the fornix will be 1 The development of the septum lucidum commences about the fifth month of foetal life, and proceeds from before backwards, pari passu with the corpus callosum and the fornix. It is developed from the lower part of the great longitudinal fissure, but becomes shut off from it in the process of development. FORNIX. 761 reflected also, since these two arches of nerve-substance are here so closely connected. The fornix is a layer of white matter, extending in the form of an arch (whence its name) from before backwards, beneath the corpus callosum. It is the great longitudinal white commissure, and lies over the velum interposi- tum (fig. 187, p. 760). Viewed from above, it is triangular with the base backwards, and is called the body ; from its anterior narrow part are given off the two anterior crura, and from its posterior and outer part the two posterior crura. The body is the broad triangular part with the narrow portion in front. The posterior broad part is connected with the corpus callosum ; in front of this it arches downwards, so as to leave the corpus callosum, to which, however, it is still connected by the septum lucidum. Its lateral free edges rest on the choroid plexuses, and are seen on the floor of the lateral ventricles. The anterior pillars or crura proceed from the front narrow part of the body, one on each side of the mesial line. As they pass forwards the crura diverge slightly, and descend through a mass of grey matter in the sides of the third ventricle towards the base of the brain, where, making a sudden bend upon themselves, they form the corpora mammillaria, from which they may be traced backwards and upwards, each to the anterior nucleus of the optic thalamus of its own side. As they descend, the anterior crura are joined by the peduncles of the pineal body, by the tgenia semi- circularis, and by fibres from the septum lucidum. Immediately behind and below the anterior crura is a triangular passage, through which the choroid plexuses of opposite sides are continuous with each other. This aperture is called the for amen of Monro. Strictly speaking, it is not a foramen, but only an interval caused by the anterior crus arching over the groove between the corpus striatum and optic thalamus on each side ; it establishes a communication between the two lateral and third ventricles, and is in shape like the letter Y, the passage from each lateral ventricle passing down- wards and inwards, and meeting below, to be continued as a single passage for a short distance before opening into the third ventricle. 762 CORPUS STMATUM. The posterior pillars or crura are continued downwards and out- wards from the thickened free borders of the body of the fornix, and are at first connected to the under surface of the corpus callosum. Each leaves the body at the posterior and outer angle as a thin flat white band resting on the choroid plexus and the pulvinar of the optic thalamus, and, curving downwards and out- wards, becomes intimately connected with the concave border of the hippocampus major as far down as the pes hippocampi, gradually tapering to a point at its termination. The free border of the posterior crus is known as the tcenia hippocampi or the corpus fimbriatum ; and on raising this up we expose an indented layer of grey matter, the fascia dentata, which is the free border of the cortical substance of the cerebrum. 1 The fornix should now be cut through transversely, and its two portions reflected backwards and forwards respectively. On the under surface of the posterior portion are seen fibres, passing transversely, belonging to the corpus callosum, and forming what is termed the lyra. Between the fornix and the upper surface of the cerebellum is the transverse fissure, or fissure of Bichat, through which the pia mater enters the ventricles. The fissure extends from the middle downwards on each side to the base of the brain, as far as the end of the descending horn. It is of a horse-shoe shape, with the concavity directed forwards. The upper boundary of that part of the transverse fissure which extends into the middle horn is some- times called the free margin of the hemisphere. The contents of the lateral ventricles should now be examined more in detail. CORPUS The corpus striatum is so called because, when STKIATUM. cut into, it presents alternate layers of a white and grey substance. It is a large ovoid mass of grey substance, part of which forms an eminence in the body of the lateral ventricle (the intra ventricular portion), but the larger part (extra ventricular portion) is embedded in the white substance of the cerebrum. The 1 The fornix and septum lucidum are absent in fish ; they are merely rudi- mentary in reptiles and birds ; but all mammalia have them in greater or less perfection, according to the degree of development of the cerebral hemispheres. CORPUS STRIATUM. 763 intraventricular portion, called the nucleus caudatus, is pear-shaped, broad in front, and when traced backwards is found to taper gradually to a point on the outside of the optic thalamus (fig. 188). Its surface is of pinkish-grey colour, and is crossed by numerous small veins (yence corporis striati), which open into the vense Galeni. FIG. 188. V W OF THE LATERAL VENTKICLES AND THE VELUM INTEBPOSITUM AFTER BEFLECT1NG THE FOENIX. 1. Anterior horn. 2. Corpus striatum. 3. Tsenia semicircularis. 4. Optic thalamus. 5. Velum interpositum, with the vense Galeni. 6. Lyra. 7. The posterior half of the fornix turned backwards. 8. Hippocampus minor. 9. Hippocampus major. 10. Eminentia collateralis. 11. Fifth ventricle. 12. Choroid plexus. When a horizontal cut is made into it, it shows a thin layer of white substance covering a mass of grey streaked with white. The extrdventricular portion, or nucleus lenticularis, can only be seen on a horizontal section being made outwards ; the section reveals a 764 HIPPOCAMPUS MAJOR. biconvex mass of grey matter, separated from the nucleus caudatus by a broad band of white substance, the internal capsule, and cor- responds with the island of Eeil. Running parallel with the outer border of the nucleus lenticularis, but separated from it by a thin layer of white substance, the external capsule, is a wavy streak of grey matter, the claustrum, of variable thickness. Outside the claustrum is another layer of white matter, and then we see the indented convolutions of the island of Reil. If a vertical trans- verse section be made through the nucleus lenticularis, it appears triangular and intersected by two white lines, which divide it into three parallel grey bands. Beneath the lenticular nucleus is a mass of grey matter, called the nucleus amygdalce, which causes an elevation at the apex of the roof of the middle horn. T;ENIA SEMI- The tcenia semicircularis, or stria terminalis, is CIECULAEIS. a narrow semi-transparent band of longitudinal white fibres, which lies in the groove between the corpus striatum and the optic thalamus (fig. 188). In front, it is connected with the anterior crus of the fornix, and descends with it to the corpus mammillare ; it passes backwards and outwards, and behind it is lost in the white substance of the middle horn of the lateral ven- tricle. Several veins from the corpus striatum pass underneath the taenia semicircularis to join the vense Galeni. The upper surface of the taenia is firmer in structure than its deeper part, and is called the horny band of Tarinus. HIPPOCAMPUS The hippocampus major is an elongated convex MAJOR, eminence of grey matter, covered with white, and is situated in the posterior part of the descending horn. It extends to the bottom of the horn, following its curve, where it becomes somewhat expanded and indented on the surface, so as to resemble fehe paw of an animal, whence its name, pes hippocampi. Attached to the front concave border of the hippocampus is the posterior crus of the fornix. It corresponds to the hippocampal fissure, which itself is filled with grey matter, which forms the fascia dentata. HIPPOCAMPUS The hippocampus minor, called also calcar avis MlNOR - and ergot, is a rounded eminence, smaller than the preceding, occupying the inner curved wall of the posterior horn. VELUM INTEKPOSITUM. 765 It consists of white matter externally, and corresponds to the calcarine fissure. Between the hippocampus major and minor is a triangular smooth surface, called the pes accessorius, or eminentia collateralis, and is found in the posterior and the descending horns. This corresponds to the collateral fissure. VELUM INTER- The velum interpositum, which supports the POSITDM AND fornix, should now be examined. This is a layer CHOBOID PLEXUS. o f pj a ma ter, which penetrates into the ventricles through the transverse fissure, beneath the posterior border of the corpus callosum, as shown in fig. 184. The shape of this vascular membrane is like that of the fornix, and its borders project beneath that body and form the red convoluted fringes called the choroid plexuses. These plexuses consist almost entirely of tortuous rami- fications of minute blood-vessels, and are covered with vascular villi. The villi themselves are covered with large spheroidal epithelial cells. In front the plexuses communicate with each other through the foramen of Monro ; behind, they descend into the middle horns of the lateral ventricles, and become continuous with the pia mater at the base of the brain. From the under surface of the velum two small vascular processes are prolonged into the third ventricle, forming the choroid plexuses of that cavity. Along the centre of the velum run two large veins, called vence Galeni, which return the blood from the ventricles into the straight sinus. The velum interpositum, with the choroid plexuses, must now be removed to expose the following structures shown in diagram (p. 768) : 1. A full view of the optic thalamus. 2. Between the optic thalami is the third ventricle, a deep vertical fissure, situated in the middle line. 3. Behind the fissure is the pineal body, a vascular structure, about the size of a pea. From this body may be traced forwards two slender white cords, called its peduncles, or striae pineales one along the. inner side of each optic thalamus. 4. Passing transversely across the third ventricle are three coia- missures anterior, middle, and posterior, connecting the opposite sides of the brain. 5. Immediately behind the pineal body are four elevations, two on each side, called the corpora quadrigemina, or nates and testes. 6. These bodies are connected with the cere- 766 THALAMUS OPTICUS. bellum by two bands, one on each side, termed the processus a cerebello ad cerebrum. 7. Between these cords extends a thin layer of grey substance, called the valve of Vieussens, beneath which lies the fourth ventricle. THALAMUS This, called also the posterior cerebral ganglion, OPTICUS. is the convex oval elevation seen immediately behind the corpus striatum and taenia semicircularis. Superficially it is covered with a thin layer of white, but internally it is com- posed of grey substance. The under surface rests upon the tegmentum of the crus cerebri, and forms part of the roof of the middle horn of the lateral ventricle ; externally it is bounded by a broad band of white substance derived from the crusta, which forms the internal capsule, already described. Externally, the optic thalamus is bounded by the tgenia semicircularis ; superfi- cially, it is covered by the choroid plexus and the fornix ; inter- nally, it forms the lateral boundary of the third ventricle, and has, running along it, the peduncle of the pineal body; poste- riorly, it overlaps the sides of the corpora quadrigemina and forms a prominence in the roof of the middle horn, where it receives the crus cerebri. The upper surface of the thalamus is divided into two portions by an oblique shallow groove, passing from before backwards ; the anterior and outer portion forms a prominent convex surface, called the anterior tubercle, which is covered with the epithelium of the lateral ventricle ; the posterior and inner portion is pointed in front, and posteriorly enlarges to form a prominent rounded eminence, the posterior tubercle or pulvinar, and is not lined with epithelium. 1 Beneath the pos- terior part of the thalamus are two small oval eminences, termed the corpora geniculata, internum and externum. These consist -of small accumulations of grey matter, beneath the white ; the outer one being situated external to and above the internal, and to the outer side of one of the roots of the optic tract (fig. 180). From each of these bodies proceeds a white band to join the root just referred to, and from the junction of these three roots (brachia) the optic tract has its commencement. A narrow band of white 1 There is a triangular depression between the pulvinar and the peduncle of the pineal body, which has received the name of the trigonum habenulce* COMMISSURES OF THE THIRD VENTRICLE. 767 substance connects the external one with the nates, and a similar band connects the internal one with the testes. 1 THIRD The third ventricle is the long narrow fissure VENTRICLE. between the optic thalami, and reaches down to the base of the brain. Its roof is formed by the fornix and the velum interpositum, the under aspect of which is lined by the epithelium covering the general ventricular cavities, and is re- flected from the velum and choroid plexuses on to the optic thalami ; the floor, which increases in depth in front, is formed by certain parts at the base of the brain, found within the inter- peduncular space viz. the locus perforatus posticus, corpora mam- millaria, tuber cinereum, infundibulum, and lamina cinerea, all of which are best seen in a vertical section, as shown on page 755. In front, it is bounded by the anterior crura of the fornix and the anterior commissure ; laterally, by the optic thalami and the peduncles of the pineal body ; behind, by the posterior commissure and the iter a tertio ad quartum ventriculum, which is a long canal beneath the corpora quadrigemina, connecting the third with the fourth ventricle. Passing across the third ventricle are seen three COMMISSURES. . , , . . -. ,, -. commissures, the anterior, middle, and posterior. The middle commissure may be seen by gently separating the optic thalami, and is about half an inch in breadth. This is composed entirely of grey substance, and in most brains, owing to its softness, is generally torn before it can be examined. 2 The anterior commissure is a round white cord, which lies immediately in front of the anterior ANTERIOR. /. , f -, ,-, crura or the tornix, and connects the corpora striata. This commissure may be traced on each side, through the corpora striata, below the nuclei lenticulares, extending backwards far into the temporo-sphenoidal lobes. Situated immediately in 1 These bands are faintly marked in man, but are more apparent in the lower animals. 2 The soft commissure does not appear to be a very essential constituent part of the brain. It is not found before the ninth month of foetal life, and in seme instances, according to our observations, is never developed. Wenzel states that it is absent in about one out of seven subjects (De penitiori Struct. Cerebri Horn, et Brut. Tubingen, 1812). 768 THIRD VENTRICLE. front of, and rather below the pineal body, is another thin round white cord called the posterior Its fibres pass into the substance of the hemispheres and connect the optic thalami. Its fibres are derived from the fillet which comes from the tegmentum of the crus cerebri. FIG. 189. POSTERIOR. commissure. Corpus callosum cut through . . Ventricle of the septum lucidum . Corpus striatum Anterior crura of the fornix . . Anterior commissure Tsenia semicircularis Middle commissure Thalamus opticus Crura of pineal gland Posterior commissure Pineal gland Corp. quadrigemina Nates I Testes . Valve of Vieussens P rocessus a cerebello ad cerebrum . 8 E The third ventricle communicates with the lateral ventricles by the two openings of the foramina of Monro, with the fourth ven- tricle through the iter a tertio ad quartum ventriculum, and" in front of its floor by a conical cavity, iter ad infundibulum, with the infundibulum. The third ventricle is covered with an epithelial lining con- tinuous with that of the lateral ventricles through the foramina CORPORA QUADRIGEMINA. 769 of Monro ; after covering the walls of the third ventricle it lines the aqueduct of Sylvius to pass to the fourth ventricle. PINEAL BODY The pineal body (conarium) is a very vascular OE GLAND. oval body, situated immediately in front of the corpora quadrigemina (fig. 189). It is about the size of a cherry- stone, and is firmly connected with the under surface of the velum, and is apt to be separated from its normal position when that membrane is reflected. It is connected to the cerebrum by two white crura, the peduncles of the pineal body, which extend for- wards, one on the inner side of each optic thalamus along their upper margin, and terminate by joining the anterior crura of the fornix. The peduncles join together behind in front of the pineal body, and are connected with the front of the posterior commissure. The pineal body consists of numerous small follicles filled with cells, which are separated by connective tissue ; so that in struc- ture it much resembles that of the anterior lobe of the pituitary body. In its interior it contains, besides some viscid fluid, more or less gritty particles (acervulus cerebri), consisting of phosphate and carbonate of lime and phosphate of magnesia and ammonia. Be- sides the calcareous particles, these follicles contain corpora amy- lacea ; and, when abundant, this sabulous matter is found on the peduncles of the pineal body. The pineal body is larger in the female than in the male subject, and is largest of all in the child. It is found in all mammalia, birds, and reptiles, in the same typical position, but its functions are entirely unknown. CORPOBA QUA- The corpora quadrigemina are four round emi- DEIGEMINA. nences, situated two on each side, behind the pineal body, and are separated from each other by a crucial depres- sion. Though white on their surface, they contain grey matter in their interior for the purpose of giving origin to the optic tract. Laterally, they are continued outwards as two convex white cords, the anterior and posterior brachia. The anterior brachium passes between the corpora geniculata, and is continued on into the optic tract, of which it may be considered its direct root : the posterior brachium passes forwards and outwards, and is lost beneath the 3D 770 VALVE OF VIEUSSENS. corpus geniculatum internum. They are situated above the iter a tertio ad quartum ventriculum. The anterior pair are called the nates, and are larger and darker than the posterior pair, which take the name of testes. A more appropriate term for these bodies would be the optic lobes. 1 The corpora quadrigemina are developed very early in foetal life, and are at first only two in number, one on each side of the mesial line; but about the seventh month a transverse groove is apparent, thus mapping out the four bodies. 2 PBOCESSUS A B 7 gently drawing back the overlapping cere- CEEEBELLO AD bellum, two broad white cords are seen, which CEBEBKUM. -pass backwards, diverging from each other, from the optic thalami and the corpora quadrigemina to the cerebellum (fig. 189). These are the processus a cerebello ad cerebrum, or supe- rior peduncles of the cerebellum. They connect the cerebrum and cerebellum, and rest upon the crura cerebri. Below they pass to the inferior vermiform process and to the white matter within the corpus dentatum. VALVE OF The triangular space between the superior pe- VIEUSSENS. duncles is occupied by a thin layer of grey matter, which covers over the anterior part of the fourth ventricle. This layer is called the valve of Vieussens, or the anterior or superior medullary velum ; it is narrow in front and broad posteriorly, where it is connected with the central portion of the cerebellum. Along the mesial line of its upper surface there is an irregular ridge, the frcewuhem, which becomes lost towards its lower part ; the lower 1 Eminences homologous to the corpora quadrigemina are found in all verte- brate animals ; they are the mesocephalic lobes ; they always give origin to the optic nerves, and their size bears a direct relation to the power of sight. They are relatively smaller in man than in any other animal. In birds there are only two eminences, and these are very large, especially in those far-seeing birds which fly high, as the eagle, falcon, vulture, &c., who require acute sight to discern their prey at a distance. 2 On making a transverse vertical section through the nates, we find that there is a superficial thin layer of white fibres (stratum zonale) ; beneath this is a crescentic layer of grey matter (stratum cinereum) ; deeper than this is a thick biconvex mass of grey matter, with nerve filaments and nerve cells (stratum opticum) ; and lowest of all is an arched layer of white nerve fibres derived from the fillet (stratum lemnisci). FOURTH VENTRICLE. 771 part is overlapped by a corrugated lobule of grey matter from the anterior part of the cerebellum, and is called the linguetta laminosa. The third ventricle is connected with the fourth AD QUARTUM ^v a canal, large enough to admit a probe, which VENTBICULUM, runs downwards and backwards beneath the pos- OR AQUEDUCT terior commissure and the corpora quadrigemina. It is about half an inch in length, and its shape varies in different parts of its course : in the lower being T-shaped, and in the upper part shield-shaped, on transverse section. In its walls is a large amount of grey matter, in which are the nuclei of origin of the third, fourth, and upper part of the fifth cranial nerves. It is lined with ciliated columnar epithelium. This pas- sage, together with the third and fourth ventricles, are persistent parts of the central canal, which in early fcetal life extended down the middle of the cerebro-spinal axis. It subsequently becomes much encroached upon by the large increase of grey substance in the process of development. FOURTH The fourth ventricle is the space situated be- VENTRICLE. t n the cereba Hum behind and the posterior surface of the medulla oblongata and pons Varolii in front. It is the dilated portion of the primordial canal alluded to in the last paragraph. If viewed in a vertical section, as represented in the diagram (fig. 184), it appears triangular, with its base forwards ; but if seen from behind, it is a lozenge-shaped space, the long axis being antero-posterior (fig. 190). The upper wall or roof of the fourth ventricle is formed by the valve of Vieussens, and by the front of the inferior vermiform process, with the two amygdalae ; laterally it is bounded, in front by the processus a cerebello ad cerebrum, and behind by the diverging posterior pyramids and restiform bodies ; below, by the continua- tion of the arachnoid membrane on to the posterior surface of the spinal cord, in which there is an aperture called the foramen of Magendie ; in front its floor is formed by the medulla oblongata and pons Varolii. The pia mater is prolonged for a short distance into the lower part of the cavity, and forms the choroid plexus of the fourth ventricle. 772 FOURTH VENTRICLE. The anterior wall is diamond-shaped, pointed above and below, while laterally the space broadens out into an angular point, be- tween the cerebellum and the medulla, called the lateral recess. Below, the ventricle is bounded by the restiform bodies and poste- rior pyramids diverging like the branches of the letter V to form the inferior peduncles of the cerebellum ; the divergence of these cords, with the median furrow, was called by the older anatomists the calamus scriptorius, from its fancied resemblance to a writing pen. At the termination of the posterior pyramid there is a slight overhanging thickening, turning over the restiform body at the FIG. 190. -a. Processus a cerebello ad cerebrum. 6. Restiform bodies. c. Fasciculi graciles. d. Fasciculus teres, ex- ternally is the f ovea superior. e. Medullary strife. /. Fasciculus tores. g. Tuberculum acusti- cum. h. Fovea inferior. i. Cerebellum. FLOOR OF THE FOURTH VENTRICLE. lateral recess, of which it forms the lateral boundary ; it is called the ligula or tcenia. We find also a similar thickening, partly of the lining membrane and partly of nerve-matter, arching over the apex of the calamus scriptorius, known as the obex. 1 The floor, formed by the posterior surface of the medulla and pons, is marked by a median groove passing from the apex of the calamus scriptorius to the iter. It is divided into two portions, a lower and an upper, by some transverse white fibres called the strice acusticce or medullares, which emerge from the median groove and pass outwards over the inferior cerebellar peduncle to join part 1 Obex, a bar. STRUCTURE OF THE CEREBRUM. 773 of the roots of the auditory nerves. The lower part of the floor v on each side, is mapped out into three surfaces by a triangular depression, fovea inferior (fig. 190, /i), having its apex at the trans- verse strife, and its base below at the posterior pyramids. On the outer side of the fovea, there is a convex triangular surface, with its base upwards (fig. 190, g), called the tubercuhim acusticum; on the inner side of the fovea, and bounded internally by the median groove, is the rounded triangular surface which marks the com- mencement of the fasciculus teres. Towards the base of the infe- rior fovea there is a dark surface of grey matter called the ala cinerea, which becomes raised into an eminence (eminentia cinerea). The upper part of the fourth ventricle is that portion between the acoustic striee and the iter a tertio ad quartum ventriculum. The median groove is still continued upwards, although it becomes fainter, and on each side of it is the parallel rounded eminence, the fasciculus teres. Outside this fasciculus is a triangular depres- sion, the fovea superior ; and passing upwards under cover of the superior cerebellar peduncle, we notice a depression of grey sub- stance, called the locus cceruleus. The lower part of the fourth ventricle is developed from the metencephalic, the upper part from the epencephalic, portion of the posterior primary vesicle. 1 STRUCTURE OF The white substance of the cerebrum consists THE CEKEBKUM. o f medullated fibres, which are, as a rule, smaller than those in the spinal cord. The general arrangement of the fibres may be classified under three heads : 1 . The diverging or peduncular fibres. 2. The transverse commissural fibres; and, 3. The longitudinal fibres. The diverging or peduncular fibres are derived partly from the crusta, and partly from the tegmentum of the crus cerebri. Those from the crusta pass forwards and outwards between the nucleus caudatus and nucleus lenticularis with the internal capsule, and in 1 Tiedemann proposed to call the fourth ventricle the first, because in the foetus it is formed sooner than any of the others ; because it exists in all verte- brated animals, whereas the lateral ventricles are absent in all osseous fishes ; and because the ventricle of the septum lucidum is absent in all fishes, in reptiles, and in birds. 774 THE CEREBELLUM. front of these ganglia the fibres radiate outwards in all directions, called the corona radiata. Most of these fibres pass indirectly to the cortical portion of the cerebrum ; some proceed direct to the cortex, through the grey ganglionic structure, amongst which are the pyramidal tract, passing to the grey matter in the neighbour- hood of the fissure of Rolando, and the direct sensory tract to the cortex of the occipital lobe. The fibres from the tegmentum are joined by others from the processus a cerebello ad cerebrum, and the corpora quadrigemina, and pass under the optic thalamus, and probably through this body, and radiate outwards, joining the corona radiata to proceed to the temporo-sphenoidal, post-parietal, and occipital lobes. The transverse commissural fibres connect the two hemispheres, and are the corpus callosum, the anterior and posterior commissures. The longitudinal fibres consist of the fornix, the striae longitudi- nales of the corpus callosum, the taenias semicirculares, the gyrus fornicatus, the gyrus uncinatus, and the peduncles of the pineal body. THE CEBEBELLUM. The cerebellum is that portion of the encephalon situated in the occipital fossa, beneath the posterior lobes of the cerebrum, from which it is separated by the tentorium. It measures in its trans- verse diameter from three and a half to four inches, in its antero- posterior diameter two to two and a half inches, and two inches in its vertical diameter. Its form is ellipsoidal, with the long axis transverse. When the arachnoid membrane and the pia mater are removed, it is noticed that its surface is darker, and not arranged in tortuous convolutions like those of the cerebrum. It is covered externally with grey matter, and consists of a multitude of thin laminae disposed in a series of nearly parallel concentric curves, with the concavity forwards. By a little dissection it is easy to separate some of the laminae from each other, and to see that the intervening fissures increase in depth from the centre towards the circumference. THE CEREBELLUM. 775 The cerebellum consists of two lateral hemispheres united by an intermediate portion, the vermiform process, the upper aspect of which takes the name of the superior vermiform, process, the inferior that of the inferior vermiform process. Comparative anatomy proves that this is the fundamental part of the cere- bellum, the lateral masses not being developed in the vertebrate series until after the birds. In man the lateral masses form by far the largest part of the cerebellum. The two hemispheres on their under aspect are convex and separated from each other by a deep fossa, the vallecula-, and, FIG. 191. SUPERIOR SURFACE OF THE CEREBELLUM. i c s. Incisura cerebelli anterior. p i. The posterior inferior lobe. i cp. Incisura cerebelli posterior. hf. The great horizontal fissure. as or I q. The anterior superior or quad- I c. The lobulus centralis. rate lobe. m c. Monticulus cerebelli. p s. The posterior superior lobe. c i. Commissura simplex. behind, this is continued so as to form a deep notch between the posterior borders of the cerebellum. The upper surface is separated from the lower by a deep fissure named the great horizontal, which extends along the free border of each hemisphere. The upper surface of the cerebellum slopes on UPPER SURFACE. , .-, , ., , , . , ni ,. each, side, having a ridge along the middle line, called the superior vermiform process. This process presents three eminences, an anterior, middle, and posterior, which are named respectively, the lobulus centralis, the monticulus cerebelli, and the 776 THE CEEEBELLUM. commissura simplex. The hemispheres are separated posteriorly by a deep notch, the incisura cerebelli posterior, which receives the falx cerebelli; and anteriorly by a broader notch, the incisura cerebelli anterior, which lodges the pons Varolii. On this surface of the cerebellum are two lobes, one of which, the quadrate, is situated on its external and anterior aspect ; the other, the posterior or cres- centic, is placed along its posterior border. On the under surface of the cerebellum, its divi- UNDER SURFACE. ... , . , . sion into two hemispheres is clearly perceptible. The deep furrow between them is called the vallecula. The front part of it is occupied by the medulla oblongata. To examine the surface of the valley, the medulla must be raised, and the hemi- spheres separated from each other. Along the middle line of the vallecula is the inferior vermiform process, which is the under surface of the original part of the cerebellum. Traced forwards, this process terminates in the nodule, which projects into the fourth ventricle, and is called the laminated tubercle of Malacarne ; traced backwards, it ends in a small conical projection, called the pyramid ; between these is a tongue-like body, called the uvula, which is con- nected with the adjacent amygdalge by an indented grey ridge, named the furrowed band. Passing from the nodule to the flocculus is a thin valve-like fold of white matter, which together take the name of the posterior or inferior medullary velum. Its anterior crescentic margin is free, and its posterior is attached to the furrowed band. 1 To see this satisfactorily, the tonsils must be carefully separated from each other. Each hemisphere presents on its under surface certain secondary lobes, to which different names have been applied (fig. 192). That portion which immediately overlies the side of the vallecula is called the tonsil (amygdala) this is connected with the uvula by an indented layer of grey matter, called the furrowed band. At the anterior part of each hemisphere, near the middle line, is a little lobe named the flocculus or subpeduncular lobe. In addition to the amygdalae and flocculi, already mentioned, other lobes have been described on the under surface of the cere- bellum. Thus, there is the digastric lobe, situated external to the 1 These are sometimes called the valves of Tarini. THE CEREBELLUM. 777 amygdala ; and behind this are successively the slender and the posterior inferior lobes (fig. 192). PEDUNCLES OF The cerebellum is connected with the cerebro- THE CEREBELLUM, spinal axis by three peduncles or crura a superior, middle, and inferior. With the medulla oblongata it is connected by means of the restiform tracts; these are called the processus a cerebello ad medullam, or its inferior peduncles : with the cerebrum it is connected by means of the processus e cerebello ad cerebrum these are called its superior peduncles. The lateral portions of the pons constitute its middle peduncles. FIG. 192. INFERIOR SURFACE OF THE CEREBELLUM. A. The amygdala. fl. The flocculus. Bi. The biventral lobe. n. The nodule \ G. The slender lobe. u. The uvula ! situated in the vallecula. pi. The posterior inferior lobe. p. The pyramid > hf. The great horizontal fissure. INTERNAL To examine the internal structure of the cere- STRUCTURE. bellum, a longitudinal section must be made through the thickest part of one of its hemispheres. There is then seen in the centre a large nucleus of white substance, from which branches radiate into the grey substance in all directions, and upon which the grey cortical substance is deposited (laminai). The lamince, about twelve in number, have branches from them at right angles, secondary laminae ; and, from these again, tertiary 778 THE CEREBELLUM. FUNCTIONS. laminae. This racemose arrangement of the white matter in the substance of the grey has been likened to the branches of a tree deprived of its leaves, and is generally known as the arbor vitce. COKPUS DEN- In the centre of the white substance of each TATUM. hemisphere is a nucleus of grey matter, the cwpus dentatum, consisting of a zigzag line of yellowish-grey colour, incomplete at its upper and inner part, and enclosing within it some white substance. Prom its centre white fibres may be traced to the superior cerebellar peduncles and the valve of Vieussens. It is displayed either by a vertical or by a horizontal section. Respecting the function of the cerebellum, the deductions derived from comparative anatomy and physiological experiments render it probable that it is the co-ordinator of muscular movements e.g., in walking, flying, and swimming. The encephalon is originally developed from three primary vesicles, from which the following parts are, in the later stages, severally developed : j Cerebral hemispheres, corpora .Prosencephalon -j striata, corpus callosum, fornix, 1. Anterior \ lateral ventricles, olfactory lobe. vesicle /Optic thalami, pineal body, pitui- ^Thalamencephalon J tary body, third ventricle, optic 2. Middle vesicle 3. Posterior vesicle j Mesencephalon I Epencephalon \ Metencephalon (Corpora quadrigemina, crura cere- bri, aqueduct of Sylvius, optic nerve. [ Cerebellum, pons Varolii, front part j of the fourth ventricle. /Medulla oblongata, posterior part J of the fourth ventricle, auditory nerve. The component parts of the encephalon begin to be developed at different periods of foetal life, and the ages at which they severally begin to appear are given as follows : DEVELOPMENT FROM THE CEREBRAL VESICLES. 779 Metencephalon . Epencephalon : Mesencephalon . POSTERIOR VESICLE. Part Month Medulla oblongata . Third Restiform bodies . Third to fourth Anterior pyramids . Fifth Olivary bodies . . Sixth Strise acusticse . . After birth Cerebellum . . Second, end of Inf. cerebellar ped. . Third Middle . Fourth Corpus dentatum . Fourth Superior cereb. ped. . Fifth Valve of Vieussens . Fifth Lobes of cerebellum . Fifth Folia . . . . Sixth Flocculus . . . Seventh Post, medullary velum Seventh Amygdalae . . . Eighth MIDDLE VESICLE. Corpora quadrigemina Fourth Fillet . . . Fourth Corpora quadrig. : Vertical groove . Sixth Transverse Seventh Thalamencephalon Prosencephalon ANTERIOR VESICLE. Optic thalami Anterior commissure . Posterior commissure . Pineal body Optic tracts Peduncles of pineal body Middle commissure . Island of Reil . Corpora striata . Corpus callosum Second to third Third Third, end of Third to fourth Third to fourth Third to fourth Ninth 1 Earliest of all Third Third, end of 780 DISSECTION OF THE SPINAL CORD. Prosencephalon . (cont.) Part Fornix . Sulci, primitive : Fissure of Sylvius . Parieto-occipital Dentate . Calcarine Sulci, secondary : Rolando . Parallel . Interparietal . Calloso-marginal Collateral Frontal . Hippocampus major . Convolutions Convolutions develope rapidly . Septum luciclum Month Fourth to fifth Middle of third Third Third Third Fifth to sixth Fifth Sixth, end of Sixth, end of Sixth, end of Seventh Fourth to fifth Fourth to fifth Seventh to eighth Fifth The cerebral hemispheres enlarge at first slowly, but later they develope much more rapidly ; the extent to which they reach backwards in the various periods of intra-uterine life is as follows : To the optic thalami at third month, To the corpora quadrigemina at fourth month, To the greater part of cerebellum at sixth month, To the posterior border of cerebellum at seventh month. DISSECTION OF THE SPINAL COED. To examine, in situ, the spinal cord covered with its mem- branes, the arches of the vertebrae must be sawn through, and removed. It is then noticed that the cord does not occupy the whole cavity of the spinal canal. The dura mater does not adhere to the vertebras, and does not form their internal periosteum, as in the skull. Between the bones and this membrane, a space inter- SPINAL VEINS. 781 venes, which is filled with a soft reddish-looking fat, with watery cellular tissue, and the ramifications of a plexus of veins. SPINAL SYSTEM The spine is remarkable for the number of large OF VEINS. and tortuous veins which ramify about it, inside and outside the vertebral canal (fig. 193). They are : 1. The dorsi-spinal or posterior external veins, which form a tortuous plexus outside the spinous, transverse, and articular pro- cesses, and the arches of the vertebrae ; they communicate with corresponding veins above and below, and they send off branches, which pass through the ligamenta subflava and intervertebral foramina, and end in the plexus inside the vertebral canal. They join the vertebral veins in the cervical region, the intercostal in the dorsal, and the lumbar and sacral veins below. 1. Anterior external veins. 2. Dorsi-spinal veins. 3. Posterior longitudinal spinal veins. 4. Anterior longitudinal spinal veins. DIAGRAM OP THE SPINAL VEINS. (VERTICAL SECTION.) 2. The veins of the bodies of the vertebrce (vence basis verte- brarum), emerge from the backs of the bodies, and empty them- selves into the transverse vein connecting the two anterior longi- tudinal spinal veins. 3. The anterior longitudinal spinal veins, two in number, one on each side, are very large tortuous veins, which extend along the whole length of the spinal canal. They communicate by trans- verse branches, passing beneath the posterior common ligament, opposite the body of each vertebra, where they receive the venae basis vertebrarum. They are larger in the dorsal and lumbar regions, and communicate externally with the vertebral, the inter- costal, the lumbar, and the sacral veins. 782 SPINAL VEINS. 4. The posterior longitudinal spinal veins, like the anterior, run along the whole length of the spinal canal. They form a tortuous venous plexus, situated inside the vertebral arches, and communi- cate in front with the anterior longitudinal veins by cross branches at frequent intervals, and externally with the vertebral, intercostal, lumbar, and sacral veins by branches through the intervertebral foramina. The anterior and posterior longitudinal spinal veins are situ- ated between the spinal canal and the dura mater of the spinal cord, and are called the meningo-rachidian veins. 5. The medulli-spinal or proper veins of the spinal cord lie within the dura mater. They form a fine plexiform arrangement FIG. 194. 1. Anterior external veins. 2. Dorsi-spinal veins . 3. Posterior longitudinal spinal veins. 4. Anterior longitudinal spinal veins. 5. Internal veins of the body of the vertebra. 6. Lateral veins. DIAGBAM OF THE SPINAL VEINS. (TRANSVERSE SECTION.) of veins over both surfaces of the cord, and can with difficulty be injected from the other spinal veins. This complicated system of veins discharges itself through the intervertebral foramina in the several regions of the spine, as follows : In the cervical, into the vertebral veins; in the dorsal, into the intercostal veins; in the lumbar, into the lumbar veins. None are provided with valves : hence they are liable to become congested in diseases of the spine. The membranes of the spinal cord, though the same in number and continuous with those of the brain, differ from them in certain respects, and require separate notice. D M The dura mater of the cord is a tough fibrous membrane, like that of the brain, but does not MEMBRANES OF THE SPINAL CORD. 783 adhere to the bones, being separated from them by fat, loose areolar tissue, and the plexus of veins described above. Moreover, such adhesion would impede the free movements of the vertebra upon each other. It is attached firmly above to the margin of the foramen magnum, and by slender tissue to the posterior common ligament, and may be traced downwards as a sheath as far as the second bone of the sacrum, from which it is prolonged as a fibrous cord to the coccyx, where it becomes continuous with the periosteum. It forms a complete canal or bag (theca) which sur- rounds loosely the spinal cord, and is relatively larger in the cer- vical and lumbar regions than in the dorsal. On each side are two openings in the dura mater for the anterior and posterior roots of the spinal nerves, and the membrane is prolonged over the trunk of each spinal nerve. These prolongations accompany the nerves only as far as the intervertebral foramina, and are there blended with the periosteum. The inner surface of the dura mater is covered with a layer of polygonal cells, so that it is smooth and secerning ; this was formerly described as the parietal layer of the arachnoid membrane. Cut through the nerves which proceed from the spinal cord on each side, and remove the cord with the dura mater entire. Then lay it flat on the table and slit up the dura mater along the middle of the front of the cord to examine the arachnoid membrane. It will be seen that the functions of the dura mater of the cord are not identical with those of encephalon, since it does not form an internal periosteum to the bones of the spinal canal ; nor does it send in partitions to support the cord ; and it does not split to form venous sinuses. ARACHNOID The arachnoid membrane of the cord is a con- MEMBEANE. tinuation from that of the brain, and is reflected over the spinal nerves as they pass from the cord to the apertures in the dura mater. This membrane invests the cord, and is in contact by its superficial aspect with the dura mater, there being an interval between them called the siib-dural space, although in some situations they are more or less connected by connective- tissue bands. On its deeper surface it is in contact with the pia mater, but is loosely connected with it by delicate areolar tissue, 784 MEMBKANES OF THE SPINAL CORD. so that there is a considerable interval between them (siibaraclmoid space) , which is occupied by a transparent watery fluid (cerebro- spinal fluid) contained in the meshes of the subarachnoid tissue. The separation between the arachnoid and the pia mater varies in different parts, and is greatest in the lowest part of the cord. CEKEBBO- This cerebro-spinal fluid cannot be demonstrated SPINAL FLUID. unless the cord be examined very soon after death, and before the removal of the brain. 1 The nerves proceeding from the cord are loosely surrounded by a sheath of the arachnoid ; but this only accompanies them as far as the dura mater, where the two are continuous. The cerebro-spinal fluid of the cord com- municates with that of the brain, and also with the general ventricu- lar cavity through an aperture in the lower boundary of the fourth ventricle, called the foramen of Magendie. The pia mater of the cord is the protecting membrane which immediately invests it. It is very different in structure from that of the brain, since it does not constitute a membrane in which the arteries break up, but serves rather to support and strengthen the cord; consequently, it is much less vascular, more fibrous in its structure, and more adhe- rent to the substance of the cord. It sends down thin folds into the anterior and posterior median fissures of the cord, and is pro- 1 The existence and situation of the cerebro-spinal fluid were first discovered by Haller, Element. Phys. vol. iv. p. 87, and subsequently more minutely investigated by Magendie, Recherches Phys. et Cliniques sur le Liquide Cephalo-rachidien, in-4, avec atlas : Paris, 1842. This physiologist has shown that if, during life, the arches of the vertebrae are removed in a horse, dog, or other animal, and the dura mater of the cord punctured, there issue jets of a fluid which had previously made the sheath tense. The fluid communicates, through the fourth ventricle, with that in the general ventricular cavity. The collective amount of the fluid varies from 1 to 2 oz. or more. It can be made to flow from the brain into the cord, or vice versa. This is proved by experiments on animals, and by that pathological condi- tion of the spine in children termed spina bifida. In the later instance, coughing and crying make the tumour swell ; showing that fluid is forced into it from the ventricles. Again, if pressure be made on the tumour with one hand and the fontanelles of the child examined with the other, in proportion as the spinal swelling decreases so is the brain felt to swell up, accompanied by symptoms resulting from pressure on the nervous axis generally. See some remarks very much to the point by Sir George Burrows, On Diseases of the Cerebral Circulation, p. 50, 1846. LIGAMENTDM DENTICULATUM. 785 longed upon the spinal nerves, forming their investing membrane or ' neurilemma.' Along the anterior median fissure may be traced a well-marked fibrous band, formed by the pia mater, which has been named the linea splendens. Below the level of the second lumbar vertebra, the pia mater is continued as a slender filament, called the filum terminate, or central ligament, which runs down in the middle of the bundle of nerves into which the spinal cord breaks up. About the level of the third sacral vertebra it becomes continuous with the dura mater of the cord, and is then prolonged as far as the base of the coccyx. The spine of the third sacral vertebra marks the level to which the cerebro-spinal fluid descends in the vertebral canal. It is supplied with nerves from the sympathetic and from the posterior roots of the spinal nerves. LIGAMENTUM From each side of the FlG - !9 5 - DENTICULATUM. cord along its whole length there runs a fibrous band, ligamentum den- ticulatum, which gives off a series of pro- cesses to steady and support the cord. They are triangular, their bases being attached to the cord, and their points to the inside of the dura mater (fig. 195). There are from eighteen to twenty-two of them 0^1 each side, and they lie between the anterior and pos- DIAGRAM OF THE LIGA- terior roots of the spinal nerves. The first MENTUM DENTICULATUM. process passes between the vertebral artery i > < P" r !. mater \ J 2, 2, 2. Ligamentum denticuiatunu. and the hypoglossal nerve ; the last is found at the termination of the cord. It is composed of fibrous tissue, and is covered with nucleated cells continuous with the arachnoid membrane. 1 1 Vide Axel Key and Eetzius ; Max Schultze's Archives, 1873. 3E 786 THE SPINAL CORD. SPINAL CORD. The spinal cord (medulla spinalis) is that part of the cerebro- spinal axis contained in the vertebral canal, and is enclosed within a sheath of dura mater (theca vertelralis), which is separated from the canal by a plexus of veins and connective tissue. It is the con- tinuation of the medulla oblongata, and extends from the foramen magnum down to the lower border of the first lumbar vertebra, where it terminates in a conical point, conus medullaris, after having given off a large bundle of nerves, termed the cauda equina, for the supply of the lower limbs. It is from fifteen to eighteen inches in length, and is about an ounce and a half in weight. Its lower extremity from the conus medullaris is continued downwards as thin silvery cord, the filum terminate, which descends along the posterior aspect of the cauda equina. It passes down within the sheath as far as the second sacral vertebra, and then, piercing the dura mater, becomes attached to the periosteum of the canal at the back of the coccyx. 1 In its upper part, the filum terminale contains some grey nerve-substance. It is a prolongation of the pia mater of the cord, and in many subjects there is a continuation of, the central canal of the cord in its upper half. The cord is not of uniform dimensions throughout. It presents a considerable enlargement in the lower part of the cervical region ; another in the lower part of the dorsal, from which proceed the large nerves to the upper and lower limbs, respectively. The upper or cervical enlargement, which is the larger, extends from the third cervical to the first dorsal vertebra, and is largest at the sixth cervical vertebra ; the lower, or lumbar, extends from the 1 The explanation of this is, that, at an early period of foetal life, the length of the cord corresponds with that of the vertebral canal ; but after the third month, the lumbar and sacral vertebras grow away from the cord, in accordance with the more active development of the lower limbs. See Tiedemann, Anatomie und Bildungsgeschichte des Gehirns im Fcettis des Menschen, &c. ; Nuremberg, 1816. THE SPINAL CORD. 787 twelfth dorsal vertebra, and is largest opposite the last dorsal vertebra. 1 The cord is divided into two symmetrical halves by a median longitudinal fissure in front and behind (fig. 196). The anterior iissure is the more distinct and wider, and penetrates about one- third of the substance of the cord ; deeper in the lower than in the upper part of the cord. It contains a fold of pia mater, with many blood-vessels for the supply of its interior. At the bottom of this fissure is a transverse layer of white substance, named the anterior white commissure, connecting the two anterior halves of the cord. The posterior fissure is much less apparent than the anterior, and is better marked in the upper and the lower parts of the cord. It does not contain a fold of pia mater, but contains a thin septum of FIG. 196. DIAGRAM OF A TRANSVERSE SECTION THROUGH THE SPINAL CORD AND ITS MEMBRANES. 1. Dura mater. 4. Anterior root of spinal nerve. 2. Arachnoid membrane. 5, 5. Seat of sub-arachnoid fluid. 3. Ganglion on posterior root of 6. Posterior branch of spinal nerve. spinal nerve. 7. Anterior branch of spinal nerve. connective tissue with blood-vessels. It can be traced to a greater depth than the anterior, and reaches down as far as the posterior grey commissure of the cord. Besides the anterior and posterior fissures, is another superficial lateral groove, from which the posterior roots of the spinal nerves emerge ; this is termed the postero-lateral groove (fig. 196). This leads down to the posterior horn of the grey matter in the interior 1 In very early foetal life these enlargements do not exist, and only make their appearance with the development of the extremities. 3 E 2 788 THE SPINAL CORD. of the cord. There is sometimes described an antero-lateral groove, corresponding to the line whence the anterior roots of the spinal nerves emerge ; but this is not really a groove, although it serves to map out each half of the cord into three longitudinal portions : a posterior, a lateral, and an anterior column. On each side of the posterior median fissure, in the cervical region, is a slender column, called the posterior median column, which is separated from the pos- terior column by a shallow furrow. 1 The anterior column is continu- ous with the anterior pyramid ; the lateral column with the lateral tract of the medulla ; the posterior column with the restiform body ; and the posterior median column with the posterior pyramid. INTERNAL A transverse section through the cord (fig. 196) STKUCTUKE. shows that, externally, it is composed of white nerve-substance, and that its interior contains grey matter, arranged in the form of two crescents, with their backs to each other. Each crescent is placed in its corresponding half of the cord, and is con- nected with its fellow across the centre by a portion called the pos- terior or grey commissure. The posterior horns are long and narrow, and extend to the postero-lateral groove, where they are connected with the posterior roots of the spinal nerves. At their extremities they taper to a point, the apex cornu posterioris, and near their bases they present a constriction, the cervix cornu, beyond which they slightly enlarge to form the caput cornu. The outline of the grey matter of the posterior horns at their commencement is indefinite and frayed out, which is especially noticeable in the cervical region, and is called the processus reticularis ; at their apices the grey matter is semitransparent in appearance, and hence is known as the siibstantia gelatinosa. In the centre of the concavity of the posterior horn is a rounded projection, most marked in the upper dorsal region, termed the tractus intermedio-lateralis, the continuation of which has been traced upwards through the medulla oblongata. The anterior horns are short and thick, and come forwards towards the attachment of the anterior roots of the nerves, but do not reach the surface. Separating the grey commissure from the anterior median fissure is the anterior or white commissure. 1 The posterior median column is said by Foville to be present along the whole length of the cord. THE SPINAL CORD. 789 On making transverse sections through different regions of the spinal cord, the grey substance is seen to vary in shape and in amount : in the cervical region, the anterior cornua are thick and short, the posterior are long and slender ; in the dorsal, the anterior and posterior cornua are both thin ; in the lumbar, the anterior and posterior cornua are large and broad ; in the lower part of the cord the grey matter is arranged in a central mass. Running along the centre of the cord in its whole length is a minute canal, the central canal, just visible to the naked eye. Below, in the conus medullaris, it ends in a dilated cul-de-sac, of the shape of the letter T ; above, it opens out at the calamus scrip- torius into the fourth ventricle. It is lined with cylindrical ciliated epithelium. This central canal is interesting, as it is the remains of the cavity formed by the spinal cord at the earliest period of its development. 1 Thirty-one pairs of nerves arise from the spinal cord, namely eight in the cervical region, twelve in the dorsal, five in the lumbar, five in the sacral, and one in the coccygeal. Each nerve is formed by the junction of two series of roots, one from the front, which is the motor root, the other from the back of the cord, which is the sensory and larger root. The two roots pierce the dura mater separately and then converge to the corresponding intervertebral foramen to form a single nerve, com- posed of motor and sensory filaments. The filaments composing the posterior roots are finer, but their fasciculi are thicker and more numerous than the anterior. 2 They proceed from the postero-lateral fissure, and previous to their union with the anterior roots are collected into two bundles which pass through a ganglion. The ganglion is of an oval form, bilobate on its external extremity, and lies in the intervertebral foramen; each fasciculus of the posterior root enters the corresponding lobe of the ganglion. The ganglia of the first and second cervical nerves are placed upon the arches of the atlas and axis respectively; the ganglia of the sacral and coccygeal nerves are situated within The central canal is well seen in fishes, birds, and reptiles. * This does not apply to the first cervical nerve, in which the anterior root exceeds the posterior in size. 790 THE SPINAL CORD. the spinal canal. The anterior roots arise from the antero-lateral column, are smaller than the posterior roots, but like them divide into two fasciculi as they approach the ganglion on the posterior root. 1 The compound nerve formed by the junction of the two roots, external to the ganglion of the posterior, divides, outside the inter- vertebral foramen, into an anterior and a posterior (dorsal) branch. (See diagram, p. 787.) The fibres of the anterior roots, after entering the antero-lateral column, pass through the white fibres to enter the grey matter ; here they pass in all directions, the larger number passing upwards and downwards, and some decussating with corresponding filaments of the opposite side, through the anterior white commissure ; some also pass upward vertically through the lateral column. The fibres of the posterior roots enter the caput cornu posterioris through the postero-lateral groove, and then pass upwards and downwards in the grey matter, chiefly of the posterior horn, but some curve round to enter the anterior horn, while others pass to the opposite side through the posterior grey, commissure. VARIATION IN ^he direction and length of the roots of th-> THE LENGTH OF nerves vary in the different regions of the spine, THE BOOTS. owing to the respective parts of the cord from which they arise not being opposite to the foramina through which the nerves leave the spinal canal. In the upper part of the cer- vical region, the origins of the nerves and their point of exit are nearly on the same level ; therefore the roots proceed transversely, and are very short. Lower down, however, the obliquity and length of the roots gradually increase, so that the roots of the lower dorsal nerves are at least a vertebra higher than the fora- 1 The researches of Blandin, Anat. descript., t. ii., p. 648, 1838, have led him to establish the following relation between the respective size of the anterior and posterior roots of the nerves in the several regions of the spine : The posterior roots are to the anterior in the cervical region : : 2 : 1 u dorsal ,, :: 1 : 1 > ,, lumbar and sacral : : 1 : 1 This relation quite accords with the greater delicacy of the sense of touch in the upper extremity. THE SPINAL CORD. 791 mina through which they emerge. Again, since the cord itself terminates at the lower border of the first lumbar vertebra, the lumbar and sacral nerves must descend from it almost per- pendicularly through the lower part of the spinal canal. To this bundle of nerves the old anatomists have CADDAEQUINA. _ . given the name 01 cauda equina, irom its resem- blance to a horse's tail. To sum up briefly, it appears that the spinal cord consists of two symmetrical halves, separated in front and behind by a deep median fissure ; that the two halves are connected at the bottom of the anterior fissure by an anterior or white commissure, at the bottom of the posterior fissure by the posterior or grey commissure ; that each half of the cord is divided into three tracts or columns of longitudinal white nerve-fibres an anterior, a lateral, and a posterior the boundaries between them being the respective lines of origin of the roots of the spinal nerves ; that the interior of the cord contains grey matter disposed in the form of two crescents, placed with their convexities towards each other, and connected by a transverse bar of grey matter, which constitutes the posterior commissure. BLOOD-VESSELS The cord is supplied with blood by 1. The OF THE COED. anterior spinal artery, which commences at the medulla oblongata by a branch from the vertebral of each side, and then runs down the middle of the front of the cord. Other branches are derived from the vertebral, ascending cervical, inter- costal, and lumbar arteries, which pass through the intervertebral foramina, and assist in keeping up the size of this anterior artery. 2. The posterior spinal arteries, which proceed also from the vertebral, intercostal, and lumbar arteries, and ramify somewhat irregularly on the back of the cord. On the posterior part of the bodies of the vertebra3, the spinal arteries of opposite sides communicate by numerous transverse branches along the entire length of the spine, thus resembling the arrangement of its venous plexuses. FUNCTIONS OF The spinal cord performs, at least, three func- THE SPINAL COED, tions : 1. It is the general conductor of impres- sions to, and from, the brain. 2. It transfers impressions. 3. It 792 THE SPINAL CORD. is a centre of reflex action. Sensory impressions are conducted by the posterior roots of the spinal nerves to the cord, and are thence transmitted to the brain through the posterior columns and the grey matter of the cord. These impressions do not run up on the same side, for the fibres, immediately on entering the grey matter, cross over to the opposite side to reach the brain ; so that if the posterior column of the right side be divided, the left leg, and not the right, would be deprived of sensation. Motor impulses are conveyed along the antero-lateral columns and the grey matter in them, and carry the commands of the will from the brain to the muscles. The crossing of the motor fibres takes place in the medulla oblongata, at the decussation of the anterior pyramids, so that they run in the corresponding half of the cord as far as their point of decussation. Division, therefore, of one half of the cord below this point, causes paralysis of motion on the same side of the body. The cord is, moreover, concerned in the conduction of impressions to and from the vaso- motor centre of the medulla oblongata, which determines the varying conditions of the blood- vessels. The cord also transfers impressions : this is more manifest in disease than in health ; a well-marked example of transference is, that pain is felt at the knee in cases of disease of the hip-joint. The spinal cord has probably no power of originating impressions, in other words, it is not automatic. 793 DISSECTION OF THE EYE. SINCE the eye in the human subject cannot be obtained suffi- ciently fresh for anatomical purposes, the student should examine the eye of the sheep, bullock, or pig. The conjunctiva should be removed, together with the loose connective tissue which unites it to the sclerotic coat. The conjunctiva is the mucous membrane which covers the ocular surface of the eyelids and the anterior part of the globe. It presents different characters in the various situations over which it is reflected, and is described as the palpebral, the sclerotic, and the corneal portions. The palpebral portion is thicker than the other portions, is very vascular, and is provided with fine papillae abundantly supplied with nerves. 1 As described p. 30, it is continuous with the mucous membrane of the lachrymal sac through the canaliculi, and lines the Meibomian glands and the ducts of the lachrymal gland. The columnar epithelium which lines the palpebral conjunctiva be- comes at the margins of the eyelids more stratified and continuous with the flattened cells of the skin of the eyelid. It forms at the inner canthus a reduplicated fold, the plica semihinaris, and is reflected from the eyelids to the globe, its angle of reflection being called the fornix conjunctives, and the folds into which this is thrown are termed the superior and inferior palpebral folds. The sclerotic conjunctiva is loosely attached by submucous tissue to the sclerotic coat, so as not to impede the movements of the globe. It is thinner, and has no papillas. It is transparent and nearly colourless, except when inflamed ; it then becomes intensely vascu- lar, and of a bright scarlet colour. The arteries are derived from 1 These papilla were first described by Eble, Ueber den Bau und die Krarik- heitf.n der Bindehaut des Auges. 794 CONJUNCTIVA. the lachrymal and palpebral branches of the ophthalmic artery r and at the circumference of the cornea they form capillary loops which anastomose with each other. The lymphatics are well marked in the palpebral and sclerotic portions of the conjunctiva, and aj the margin of the cornea they rapidly diminish in size and become connected with the cell-spaces in the cornea. An abundant supply of nerves is distributed to the membrane ; their arrangement is in the form of plexuses as far as the margin of the cornea, where they terminate in ' end-bulbs,' described by Krause, resembling in many respects the central portion of Pacinian corpuscles. The corneal conjunctiva is composed chiefly of epithelium ar- ranged in layers, the deepest of which consists of columnar cells resting by their bases on the substantia propria of the cornea; superficial to these are two or three layers of polygonal cells, the deepest of which, called the fingered cells of Cleland, interdigitate with the columnar cells ; and on the surface there is a layer of flattened squamous epithelial cells. This portion of the conjunctiva cannot be separated by dissection in recent eyes, but it possesses the same acute sensibility as the rest of the conjunctiva. Changes produced by inflammation of the conjunctiva often involve the cornea and render its texture thick and opaque. 1 The eyeball is embedded in a large quantity of fat and delicate connective tissue ; and surrounding it in its posterior three-fourths is a serous membrane, the capsule of Tenon, which allows of its free movement in the orbit. The axes of the two eyeballs are nearly parallel with each other ; thus they do not correspond with the axes of the orbits, nor of the optic nerves which enter the globes on their nasal aspect. The human eye is nearly spherical, and consists of segments of two spheres: a large posterior one, which corresponds with the 1 The facts of comparative anatomy confirm this view. In the serpent tribe, which annually shed the skin, the front of the cornea comes off with the rest of the external surface of the body. In the eel the surface of the cornea is often drawn off in the process of skinning. In some species of rodents which burrow under the ground like the mole, the eye is covered with hair, like other parts. SCLEROTIC COAT. 795 sclerotic, and a small anterior one with the cornea. The antero- posterior and vertical diameters of the globe are equal, the trans- verse exceeding these by less than half a line. The convexity of the cornea varies in different persons and at different periods of life ; this is one cause of the varying degrees of near and far sight. COATS AND The globe is composed of three concentric coats, HUMOURS OF arranged one within the other, which enclose cer- THE EYE. tain transparent structures for the transmission of light. The external coat, consisting of the sclerotic and cornea, is fibrous, thick, and strong. The second coat, consisting of the clioroid, the iris, and the ciliary processes, is composed of blood- vessels, muscular tissue, and pigment cells, and is very dark in colour. The third coat, called the retina, consists of the expansion of the optic nerve for the reception of the impression of the waves of light. The bulk of the interior is filled with a transparent humour, called the vitreous body. Embedded in the front of this, and just behind the pupil, is the crystalline lens, for the purpose of concentrating the rays of light. In front of the lens is placed a moveable curtain, called the iris, to regulate the amount of light which shall be admitted through a central aperture, the pupil, to the fundus of the eye. The space in which the iris is suspended is filled with a fluid, termed the aqueous humour. The sclerotic coat is the white tough protecting SCLEROTIC COAT. , , . , . -. A _ coat ot the eye which serves to maintain the form of the globe. 1 It covers the posterior five-sixths of the globe, the remaining anterior one-sixth being completed by the cornea. It is of dense white colour, except in front, where the tendons of the recti and obliqui are inserted into it. The thickest part of the sclerotic coat is at the back of the globe (fig. 198) ; the thinnest is a short distance behind the cornea. 2 The back of the sclerotic is perforated by the optic nerve, which enters it about one-tenth 1 The sclerotic coat of the eye in fishes is of extraordinary thickness and density ; and in birds this coat is further strengthened by a circle of bony plates, fourteen or fifteen in number, arranged in a series round the margin of the cornea. Similar plates are found in some of the reptiles, and particularly in the fossil ichthyosauri and plesiosauri. 2 The greatest thickness posteriorly is about the ^th of an inch ; its thinnest in front is about the ^th of an inch. 796 SCLEEOTIC COAT. FIG. 197. of an inch on the inner or nasal side of the axis of vision. The sheath of the optic nerve becomes continuous with the sclerotic, where it perforates this coat. The optic nerve at its entrance into the sclerotic is much constricted, and instead of passing through a single aperture in this coat, it enters it through a number of minute apertures, so that this membrane forms a porous lamina, called the lamina cribrosa. In the centre of the lamina cribrosa is an opening (porus opticiis), larger than the rest, which transmits the arteria centralis retinas. Around the optic nerve the sclerotic is pierced by the ciliary arteries, veins, and nerves, for the supply of the choroid and iris. About a quarter of an inch from the cornea the sclerotic receives the insertions of the recti muscles ; here also it transmits the anterior ciliary arteries, which run forward along the tendons of these muscles, and form a vascular ring around the circumference of the cornea (fig. 197). The sclerotic is STRUCTUKE. _ ., composed ot con- nective tissue arranged in bundles, which run, some longitudinally, some transversely, and are inter- mingled with fine elastic fibres. The longitudinal fibres are the most external and abundant. Under the microscope numerous connective-tissue corpuscles may be seen filling cell-spaces, similar to those in the cornea but not so a,bundant, and containing pigment-granules. The inner surface of the sclerotic is of a dark brownish colour, due to the presence of a thin layer of connective tissue, lamina fusca, in which are found pigment-cells. This surface of the sclerotic is grooved for the pas- sage of the ciliary nerves, which run forward ifl a sort of lymph- space ; and it is, moreover, connected by filamentous tissue with the subjacent choroid coat. The cornea is the brilliant translucent coat which forms about the anterior one-sixth of the globe. It INSERTION OF THE RECTI MUSCLES WITH ANTERIOR CILIARY ARTERIES. CORNEA. THE CORNEA. 797 is nearly circular in shape, its diameter being nearly half an inch, and its thickness about -^kh. of an inch. The curve of the cornea forms part of a smaller circle than that of the sclerotic, so that it projects further forwards, varying in this respect in different eyes, and at different ages of life. It is firmly connected at its margin to the sclerotic, with the fibres of which it is continuous. The margin of the sclerotic is bevelled on the inside ; that of the cornea on the outside, so that the former overlaps the latter (fig. 198). To examine the cornea, it should be removed with the sclerotic Fia. 198. Hyaloid membrane Retina (dotted line) Choroid coat (black line) Sclerotic coat . . Cornea. Iris. Ciliary processes . CanalofSchlemm or Fontana. Ciliary muscle. DIAGRAM OF A VERTICAL SECTION OF THE EYE. 1. Anterior chamber filled with aqueous humour. 2. Posterior chamber. 3. Canal of Petit. coat. This should be done under water, by making a circular cut with scissors, about a quarter of an inch from the margin of the cornea. With a little care it will be easy to remove the outer coat of the eye without injuring the dark choroid coat, the ciliary muscle, or the iris. In the loose brown-coloured connective tissue between the sclerotic and the choroid are the ciliary nerves passing forwards to the iris ; their white colour makes them very con- spicuous on the dark ground. The cornea consists of four layers, which are not all composed of the same kind of tissue ; they STRUCTURE. 798 STRUCTURE OF THE CORNEA. are, from without inwards, the conjunctiva, the substantia propria or cornea proper, the posterior elastic lamina, and the epithelial lining. The conjunctiva is the most superficial layer, and consists of several strata of epithelial cells ; the deeper ones are columnar and placed vertically, the next consist of several layers of polygonal cells, and the most superficial ones are flattened scaly epithelium cells, with well-marked nuclei. The cornea proper or substantia propria consists of translucent connective tissue, upon which the thickness and strength of the cornea mainly depend. The fibres are arranged in laminae, about sixty in number. Those composing a lamina are arranged in a parallel direction, but the fibres of each layer cross at right angles those of each succeeding layer. The lamellae are connected to- gether by filaments passing from one to another, so that they are not perfectly separate from each other. The cornea proper in the recent subject presents no trace of structure, but it is only after death by means of lenses and reagents that these lamellaa can be satisfac- torily demonstrated. Between the lamellae are irregularly branched spaces, called the cell-spaces of the cornea, in which are lodged the corneal corpuscles, having outstanding processes, which communicate freely with each other in their own plane, and also with those of the planes on either side. These corpuscles correspond in shape to the spaces within which they lie. 1 In inflammation of the cornea they undergo considerable changes. Immediately below the conjunctiva, the cornea proper presents a different appearance to that of the main thickness of this layer, so that this has been described by some anatomists under the name of the anterior elastic lamina of Bowman. It presents, however, a definite fibrillar struc- ture, similar to that of the cornea proper, but is destitute of the corneal corpuscles and cells. The greatest thickness of the cornea proper is about -^g-th of an inch, and that of the anterior elastic lamina about j-gViyth f an inch. 1 If fluid be injected very gently into the cornea proper, there may be demon- strated a system of canals, called Rccklingliauseri' s canals, which are the commu- nications between the corneal corpuscles ; but if the fluid be injected more forcibly, it passes in the course of the fibres composing the various lamins of the cornea, which gives the appearance of a number of varicose and enlarged tubes crossing each other at right angles : these are termed 'Bowman's corneal tubes. STRUCTURE OF THE CORNEA. 799 The posterior elastic lamina, called also the membrane of Desce- met or Demours, is translucent, elastic, and brittle, and may be easily separated from the preceding lamina. It consists of a per- fectly structureless lamina, which, when peeled off, has a remark- able tendency to curl with the attached surface innermost. It is unaffected by boiling, or by the action of acids or alkalies, and is from ^-^L-Q-th to -^-J^-th of an inch in thickness. At the junction of this lamina with the sclerotic on its inner surface, it spreads out into a number of radiating tooth-like processes, the ligamentum pectinatum iridis, which are attached to the front of the circum- ference of the iris and to the sclerotic and choroid coats. The pro- cesses alone are covered with epithelial cells, and the intervals between the .processes form small spaces, the spaces of Fontana, which communicate freely with the fluid of the aqueous chamber. In the sclerotic coat, close to its junction with the cornea, is situated a small oval canal, lined with epithelium, termed the sinus circularis iridis or canal of Schlemm (fig. 198). Although, by some, it is considered a lymph-space, it is probably a venous sinus, for it can be injected from the arteries ; but it has probably some free communication with the fluid of the anterior chamber, as this fluid passes readily from the chamber into this sinus. 1 The epithelial lining -consists of a single layer of polygonal nucleated cells, and lines the inner surface of the posterior elastic lamina. They resemble those which line serous membranes generally. Arteries and nerves. In the healthy condition the cornea con- tains no blood-vessels, except at its circumference, where they form loops. Nor have any lymphatics been demonstrated in it. Its nerves, which are numerous forty to forty -five in number are derived from the ciliary nerves, and may be traced forwards to the fibrous portion of the cornea, where they lose their dark outline and become transparent, forming a fine plexus the primary plexus. This gives off minute filaments which ramify beneath the epithe- lium, constituting the secondary or sub-epithelial plexus. From 1 For further information on this point consult Leber, ArcMv f. Opth. 1878 ; Heisrath, Archiv f. Opth. xxvi. ; and Schwalbe, Graefe, and Saemisch's Handbook, 1874. 800 CHOROID COAT. this very minute varicose fibres run between the epithelial cells, forming the inira-epithelial plexus. Besides these plexuses, fila- ments are given off from the primary plexus to supply the cornea proper, and the filaments are said by some to be continuous with the anastomosing processes of the cell-spaces. After the removal of the sclerotic coat and the CHOEOID COAT. , . , ... ,, ,, cornea, which constitute the first tunic, we expose the second tunic, consisting of the choroid, the iris, and ciliary processes in front, and of the ciliary ligament and the ciliary muscle. The clioroid is the soft and flocculent tunic of the eye, recog- nised by its dark brown colour and great vascularity. It covers the posterior five-sixths of the globe, and is thickest posteriorly, where there is a circular aperture in it for the passage of the optic nerve. In front, the choroid passes beneath the ciliary muscle and ligament with which it is connected, and then extends forwards, terminating in a series of plaited folds, called the ciliary processes. It is connected with the sclerotic by delicate connective tissue, the lamina fusca, through which the ciliary vessels and nerves pass forwards (fig. 199) to the iris. Its inner surface is smooth, and is in contact with the retina, and when detached from it presents a layer of hexagonal pigmented cells, which are now recognised as forming a part of the retinal coat and as part of which it is originally developed . Under the microscope the choroid is seen to consist of two layers, an external and an internal. The choroid is covered externally by a connective tissue layer, similar to the lamina fusca of the sclerotic, and known as the lamina supra-choroidea ; it consists of connective tissue intermingled with elastic tissue, and embedded in the meshwork are pigment-cells and lymphoid cells. The contiguous surfaces of the lamina fusca and the lamina supra-choroidea are lined with squamous epithelium, having between them a more or less complete lymph-space, which is continuous with that of Tenon's capsule through the apertures in the sclerotic, through which the ciliary vessels and nerves pass. The external layer consists of the larger branches of the blood- vessels ; the arteries (short ciliary) running forwards between the CILIARY PROCESSSES. 801 veins, previous to dipping down to form the internal layer. The veins are arranged with great regularity in drooping branches (vence vorticosce) like a weeping willow (fig. 199), and converge to four or five nearly equidistant trunks, which, after running back- wards for a short distance, perforate the sclerotic not far from the entrance of the optic nerve, and empty themselves into the oph- thalmic vein. Between the veins there are interspersed numerous stellate pigment-cells which anastomose with neighbouring cells ; on the inner side of this layer the cells are absent. The internal layer is formed by the capillaries of the ciliary arteries and is called the tunica Ruyschiana, after the Dutch anato- FIG. 199. SCLEROTIC COAT REMOVED TO SHOW THE CHOROID, CILIARY MUSCLE, AND NERVES. mist Ruysch. The capillaries branch off from the choroid vessels in a radiating manner, and form the most delicate vascular net- work found in any tissue. It extends forwards as far as the retina, where the intervals become larger and the vessels freely communicate with those of the ciliary processes. This tissue has on its inner surface a transparent membrane, the membrane of Bruch, which rests on the pigmentary layer of the retina. CILIARY The ciliary p)-ocesses are the plaited folds formed PROCESSES. by the anterior part of the choroid, and may be best seen when the globe has been divided by a transverse vertical 3F 802 CILIARY MUSCLE. section into an anterior and a posterior half, the vitreous humour being left undisturbed. They are black, and consist of from sixty to seventy radiating folds arranged in a circle about three lines broad. These processes consist of longer and shorter folds, the former being the more numerous, and in the proportion of three to one of the latter. The longer fold is about yV^h f an i ncn i n length ; the smaller about -^th of an inch. One of the longer processes is seen in the diagram. The processes fit into corresponding folds of the suspensory ligament of the lens, and their free ends pro- ject for a short distance into the posterior chamber. The circum- ference of the processes are attached to the ciliary ligament ; their inner ends are free and rest upon the circumference of the lens. The vascular supply of the ciliary processes is most abundant and resembles in the main that of the choroid, except that the plexus is coarser, with its meshes arranged longitudinally. The arteries come chiefly from the ante- rior ciliary, and from the front vessels of the choroid ; and after breaking up into a fine plexus, they form loops which arch back- wards, to end in the smaller veins. Their dark colour is due to several layers of pigmented cells, which disappear, however, at the free ends of the processes. The ciliary muscle consists of unstriped mus- CILIABY MUSCLE. , , -. -. , cular fibres, and forms a muscular zone at the front of the choroid close to the junction of the sclerotic with the cornea. It arises by a thin tendon from the sclerotic close to the cornea, and near the spaces of Fontana. Thence some of its fibres radiate backwards, forming the meridional or radiating fibres, and are lost in the choroid behind the ciliary processes : some of the fibres form a circular muscle around the outer circumference of the iris, the circular ciliary muscle, which was formerly described as the ciliary ligament. Its action is to accommodate the eye to objects at various distances by compressing the lens and increasing the convexity of its anterior surface. 1 The iris is the contractile and coloured curtain suspended in the clear fluid which fills the space 1 Sir P. Crampton has noticed that this muscle is well developed in birds. In them, its muscles are of the striped variety, as are the circular fibres of the iris. IRIS. 803 between the cornea and the lens. The iris divides this space into two unequal parts, called the anterior and posterior chambers (fig. 198) ; these communicate with each other through a circular aperture in the centre of the iris, called the pupil, which is situated a little to the inner side of the iris. 1 . The circumference of the iris is nearly circular, and is immove- ably connected with the choroid, the ciliary muscle, and through the ligamentum pectinatum with the cornea. The diameter of the iris is about half an inch, and that of the pupil in man varies from the -JWth to the ^rd of an inch. % O o The colour of the iris varies in different subjects, and gives the peculiar tint and brilliancy to the eye. The colouring matter or pigment is contained in minute cells, pigment cells, lining the anterior and posterior surfaces of the iris, the posterior taking the name of uvea, from its grape-like colour. Pigmented cells are also found in the substance of the iris. The use of the iris is to regulate the amount of light which shall be admitted into the eye ; for this purpose its inner circum- ference is capable of dilating and contracting according to circum- stances, while its outer circumference is immoveably attached. When the iris is laid under water, and viewed STRUCTURE. . , , . P . ... , with a low magnifying power, it is seen to be composed of fine fibres converging from all sides towards the pupil ; many of them unite and form arches, leaving elongated interspaces, which are most marked towards the middle of the iris. In front of the iris is a thin layer of polyhedral cells, which is continuous with that covering the membrane of Descemet, but the cells are smaller and more granular. The stroma consists of connective tissue and cells. The fibres of the connective tissue are arranged longitudinally and circularly ; the longitudinal fibres radiate from the circumference towards the pupil, and between them are contained the blood-vessels and nerves ; the circular fibres are found at the circumference of the iris. Intermingled in the meshes of this connective tissue and 1 The size and shape of the pupil vary in different animals. In the bullock, sheep, horse, &c., it is oblong ; in carnivorous quadrupeds it is often a mere vertical slit during the day, but dilates into a large circle at night. 3 F 2 804 STRUCTURE OF THE IRIS. throughout its whole thickness are numerous and various-shaped pigment cells having anastomosing processes, like those of the choroid. They are chiefly found in the uvea, which is continuous with the pigmented layer of the retina. Upon the disposition of these pigment-cells depends the colour of the iris : in dark eyes, the pigment-cells are scattered throughout the thickness of the stroma ; in light eyes, only on its posterior surface. The muscular tissue is of the unstriped kind, and is arranged partly in a radiating, partly in a circular manner. The circular fibres, the sphincter, well marked, are collected on the posterior aspect of the pupillary margin, where they form a ring about -^th of an inch in width ; at the free margin of the iris they form a thick bundle, but become more frayed out towards the circum- ference. 1 The radiating fibres, the dilatator, converge towards the pupil, where they form arches and blend with the circular fibres. The pigment, as before described, is found in varying thickness and position, differing according to the colour of the iris. The arteries of the iris are derived from the two long and the anterior ciliary arteries. The long ciliary arteries perforate the sclerotic coat on each side of the optic nerve, and then run forwards between this tunic and the choroid to the ciliary muscle at the outer circumference of the iris. Each artery divides into an upper and a lower branch, which form with each other and the anterior ciliary arteries a vascular circle (circulus major) ; from this circle numerous small branches pass inwards and form another circle (circulus minor) of anastomosis, which terminates in the veins of the iris. The anterior ciliary arteries, five or six in number, are derived from the muscular and lachrymal branches of the ophthalmic artery, and ramify on the tendons of the recti muscles (p. 796), where they pierce the sclerotic about the -jVth of an inch behind the margin of the cornea. These vessels supply the ciliary pro- cesses and iris, and join the circulus major : it is from their en- largement that the red zone round the cornea is produced in inflammation of the iris. 1 The circular fibres of the iris in the bird are of the striped variety, and discernible without difficulty. RETINA. 805 The veins follow the same arrangement as the arteries, and communicate as stated (p. 799) with the canal of Schlemm. The nerves of the iris come from the nasal branch of the ophthal- mic nerve, and by twelve to fifteen branches from the lenticular ganglion. They pierce the sclerotic around the entrance of the optic nerve, and run forwards between the sclerotic and the choroid as far as the ciliary muscle. On the choroid they form a gangliated plexus which lies in connection with and among the blood-vessels. In the ciliary muscle the nerves form another plexus, from which numerous non-medullated fibrils are given off to terminate in the muscular tissue of the iris. The sphincter iridis is supplied through the motor root of the lenticular ganglion which is derived from the third nerve ; the dilatator iridis is supplied by the sympathetic system. MEMBBANA Until the seventh or eighth month of foetal PUPILLABIS. life, the pupil is closed by a transparent, vascular membrane, the membrana pupillaris, so that the anterior and posterior chambers are divided from each other by this membrane. Its vessels, derived from those of the iris and capsule of the lens, are arranged in loops which converge towards the centre of the membrane without joining each other. About the eighth month this membrane becomes gradually absorbed, so that at birth it is completely lost. To obtain a view of the retina, the choroid coat must be carefully removed while the eye is under water ; this should be done with the forceps and scissors on a fresh eye. When the choroid is thus removed, there will be seen on its inner surface a layer of pigmented cells, which has been already referred to as really the external layer of the retina, and not in any way part of the choroid coat. The optic nerve, having entered the interior of the globe through the sclerotic and the choroid, expands into the delicate nerve layer, called the retina, which forms the third tunic of the globe. The retina is in contact, externally, with the choroid ; internally, with the hyaloid membrane, which sepa- rates it from the vitreous ; and it extends forwards nearly to the posterior margin of the ciliary processes, where it terminates in a thin serrated border the or a serrata ; from this border a thin 806 STRUCTURE OF THE RETINA. membrane pars ciliaris retinae destitute of nerve fibres, is con- tinued forwards to the tips of the ciliary processes, and thence to the posterior surface of the iris. In passing through the coats of the eye, the optic nerve becomes gradually constricted and reduced to one-half of its diameter ; here it presents a round disc, called the porus options, in the centre of which may be seen the arteria centralis retinse. At this point, too, the nerve-substance projects slightly into the interior of the globe, forming a little prominence, to which the term colliculus nervi optici has been applied. This prominence is remarkable, in that it is insensible to the rays of light, and is hence called the ' blind spot.' The retina when fresh is nearly transparent, but soon it becomes of a pink milky tint. Precisely opposite the pupil, in the centre of the axis of vision, there is an oval yellow spot, macula lutea, in the retina, about ^-th of an inch in diameter, having a depression, fovea centralis, in the centre, and fading oft 7 gradually at the edges. Here vision is most perfect, so that it might be called the ' spot of light.' This central spot was believed by its discoverer, Sommering, to be a perforation ; but it is now ascertained to be due to the pigmentary layer of the retina showing through it. These appearances are lost soon after death, and are replaced by a minute fold, into which the retina gathers itself, reaching from the centre of the spot to the prominence of the optic nerve. 1 Although to the naked eye the retina appears a simple, soft, semi-transparent membrane, yet when examined under the microscope it is found to be most minutely and elaborately organised. It varies in thickness from the sV^ to ^6 -j-J-oth of an inch, being thickest behind, and gradually diminishes towards the front. It consists of eight layers, through which may be traced a considerable amount of extremely delicate connective tissue (fibres of Miiller), which con- stitutes a sustentacular tissue for the various strata, and is said to form for them two more or less continuous boundary layers, termed membrance limitantes, interna and externa, and which are classed by 1 In birds the retina has throughout the yellowish colour seen only at one par in the human eye. STRUCTURE OF THE RETINA. 807 some anatomists as two additional layers. The layers of the retina are as follows, beginning from within : 1. The layer of nerve-fibres. 2. The ganglionic layer. 3. The inner molecular layer. 4. The inner nuclear layer. 5. The outer molecular layer. 6. The outer nuclear layer. 7. The layer of rods and cones. 8. The pigmentary layer. The membranae limitantes are situated as follows : the internal stratum lies on the inner surface of the layer of nerve-fibres ; the external, between the outer nuclear layer and the layer of rods and cones. 1. The layer of nerve-fibres (fig. 200, i) is composed of the spread- ing out of the optic nerve-fibres, and of connective tissue cells. The nerve-fibres, consisting only of the axis-cylinders, run for- wards as a continuous layer to the ora serrata, partly arranged in bundles and partly in plexuses, and become connected with the nerve-cells of the next layer. The fibres are almost absent on the yellow spot. 2. The ganglionic layer (fig. 200, 2) is a stratum of spheroidal nerve-cells ; from the deeper part of each cell there is given off a single elongated process, which passes obliquely into the nerve-fibre layer, with which it becomes continuous ; from the outer side of the cell two or more processes are given off, which branch dichotomously and become at first embedded and then lost in the inner molecular layer. The ganglionic cells, which in the greater part of the stratum form a single layer, are at the yellow spot arranged eight or ten deep, and in its neighbourhood two or three deep. 3. The inner molecular layer (fig. 200, 3) is a granular stratum of considerable thickness which exhibits, under high powers, a reticu- lar structure, having small interstices filled probably with lymph. In it are found, the processes of the nerve-cells of the preceding layer, which pass outwards for a considerable distance ; some vari- cose filaments which pass inwards from the next layer ; and some Mullerian fibres which pass through this layer. Other cells, like 808 STRUCTUKE OF THE RETINA. those found in the nerve-fibre and ganglionic layers, are also found in this stratum, chiefly on its surfaces. 4. The inner nuclear layer (fig. 200, 4) contains three kinds of cells, and some fibres which belong to the Miillerian or connective tissue fibres of the retina. The first kind consists of oval bipolar cells FIG. 200. 8. Layer of pigment cells. 7. Layer of rods and cones. (Membrana Jacobi.) Membrana limitans ext. 6. Outer nuclear layer. 5. Outer molecular layer. 4. Inner nuclear-layer. 3. Inner molecular-layer. 2. Layer of nerve-cells. 1. Layer of nerve-fibres. Membrana limitans interna. DIAGBAM OF THE VARIOUS LAYERS OF THE RETINA. (AFTER SCHWALBE.) placed longitudinally, and having a distinct nucleus and nucleolus ; from the inner extremities of these cells there extend long vari- cose, thin processes which pass vertically downwards, without division, into the inner molecular layer, and are presumably con- nected with the processes of the ganglionic layer and thence with STRUCTURE OF THE RETINA. 809 the nerve-fibres ; from the outer extremities of the cells pass pro- cesses, thicker than the ones just described and not varicose, which pass to the next layer and there break up into numerous filamentous processes. The second kind of cells are small, granular, proto- plasmic cells, which are confined to the deeper part of this layer ; and the third kind, similar in their appearance, are disposed here and there in the most external stratum of the inner nuclear layer. The course which the Mtillerian fibres take through this layer will be described later on. 5. The outer molecular or internuclear layer (fig. 200, 5) resembles in most respects the inner molecular layer, but is much thinner. It contains, however, numerous flattened, branched cells, having well-marked nuclei and nucleoli, and whose fine branching pro- cesses exhibit varicosities in their course, resembling nerve-fibrils. Whether these are nerve-fibres or only the fibres of the sustentacular tissue is at present not determined ; but this layer, as well as those already described, is developed in the same manner as those of the brain, so that probably these fibres are nerve-fibrils. 6. The outer nuclear layer (fig. 200, e) consists of a thick stratum of nucleated cells, having outward and inward prolonga- tions, which may be recognised as connected respectively with the rods and cones of the next layer. The rod-granules are the most numerous, and each presents an oval cell, which has a well-marked transverse striation, due to the highly refracting substance being crossed by discs of a less refracting medium. There are usually two, one on each side of the middle of the cell. From this enlargement one varicose filament passes inwards and becomes connected with the outer molecular layer by a dilatation, from which numerous fila- ments pass inwards ; the other extremity is thicker, not varicose, and passes outwards towards the membrana limitans externa, where it becomes somewhat expanded, and then becomes continuous with a rod. The cone-granules are fewer, and each has an oval nucleated cell, which presents no transverse striation characteristic of the rod-granule. The cell is situated close to the membrana limitans externa, and rests upon a thick cone-fibre, much thicker than a rod-fibre, which enlarges as it approaches the outer molecular layer, upon which it rests by a pyramidal base. From this base numerous 810 STRUCTURE OF THE RETINA. fine processes are given off into the molecular layer : the outer extremity is very short and broad, and supports the base of a cone. 7. The layer of rods and cones, bacillary layer or Jacob's mem- brane (fig. 200, 7) is composed of minute cylindrical elements, arranged at right angles to the surface of the retina. The rods, the more numerous, are tapering processes running through the whole thickness of this layer, and, externally, are embedded to a greater or less depth in the pigmented layer, so that when viewed from without they have the appearance of mosaic pavement made up of round segments. Among the rods are intermingled nume- rous shorter, flask-shaped bodies called cones, which do not extend through more than half the thickness of this layer. Their outer extremities taper off towards the choroid ; their inner or broad ends, like the rods, rest upon the membrana limitans externa, and thence are connected with the outer nuclear layer. Each rod and cone consists of two segments of equal lengths : the inner, in the case of the cones, very broad and bottle-shaped, of the rods only slightly bulged ; the outer, fine and tapering off. The two segments vary in their microscopic appearance and in relations to reagents ; the outer segments of both have a transverse striation, and break up in the direction of this striation ; the inner segments are com- posed externally of longitudinal fibrillae, internally of finely granular homogeneous substance continuous with the rod or cone fibre. The inner segments are deeply stained by carmine, iodine, &c., the outer segments not by the same reagents, but are by osmic acid. The rods are absent at the yellow spot. 8. The pigmentary layer (fig. 200, 8) is usually described as forming part of the choroid coat, but it should both development- ally and physiologically be included as one of the layers of the retina. It consists of a single layer of hexagonal nucleated cells filled with pigment-granules, which are most numerous towards the margins of the cells. The surface of the cells which looks towards the choroid is smooth and destitute of pigment-granules, and it is here that the nucleus is situated; the surface towards Jacob's membrane is filled with pigment, which is not well defined, but runs down among the rods, so that their outer part is embedded among the pigment-cells. The use of the pigment is to absorb the STRUCTURE OF THE RETINA. 811 rays of light which pass through the retina, and thus prevent their being reflected. It serves the same purpose as the black paint with which the inside of optical instruments is darkened. Albinoes, in whom this layer has little or no pigment, are, consequently, dazzled by daylight and see better in the dusk. 1 The sustentacular tissue (Miillerian fibres) is a tissue which runs through the greater thickness of the retina, beginning at the so-called membrana limitans interna, and ending at the membrana limitans externa; but in neither of these two situations does it form a continuous layer, so that it cannot be classed under the layers forming the retina. These fibres are probably of the nature of a delicate connective tissue, which serves to sustain the various layers and their constituent elements. Each fibre begins by a broad conical base, on the deeper aspect of the layer of nerve- fibres (the bases of these fibres being more or less in connection with each other) ; it then passes through the layers of nerve-fibres and ganglionic cells, and, consequently, the inner molecular layer, gradually diminishing in thickness ; on reaching the inner nuclear layer it gives off thin filamentous processes which support the structures of this stratum, presenting here a lateral bulge with a well-marked nucleus. After passing through the outer molecular layer it reaches the outer nuclear layer, and then breaks up into filaments which join with fibrils from other Miillerian fibres, thus enclosing and supporting the cells and their prolongations of this layer. These filamentous offsets reach as far as the bases of the rods and cones, forming a bed on which they rest ; this is described as the membrana limitans externa. The structure of the macula lutea and fovea centralis. In the macula lutea, the nerve-fibres do not form a continuous layer ; the ganglionic layer consists of cells six to eight deep ; there are no rods ; the cones are longer and narrower than elsewhere ; and the outer nuclear layer has only cone-fibres. In the fovea centralis 1 In many of the nocturnal carnivorous quadrupeds, the inner surface of the choroid at the bottom of the eye presents a brilliant colour and metallic lustre. It is called the tapetum. By reflecting the rays of light a second time through the retina, it probably enables the animal to see better in the dusk. It is the cause of the well-known glare of the eyes of cats and other animals ; and the great breadth of the luminous appearance arises from the dilatation of the pupil. 812 AQUEOUS HUMOUK. there are no rods, and the cones are longer than in the macula ; and all the other layers are much thinned. At the margin of the fovea most of the layers are thicker than elsewhere. The structure of the ora serrata is much less complex than the other parts of the retina ; the layer of rods and cones dis- appear, the former first of all ; the ganglionic and nerve-fibre layers become thin and then cease ; the inner molecular layer loses much of its granular appearance, and is largely formed of sustentacular tissue, and then abruptly ceases; the inner and outer nuclear layers become thinner, and then gradually merge into a single layer, which is continued on to the pars ciliaris as a single stratum of columnar epithelial cells. The arteria centralis retince, after emerging through the porus opticus, divides into two branches an upper and a lower which then form a delicate network of blood-vessels throughout the nerve- fibre layer, penetrating as far as the inner nuclear layer, beyond which no capillaries can be traced. After maceration in water, the nervous substance can be removed with a camel's-hair brush, and then in an injected eye the network formed by the vessels can be distinctly seen. The arteries of the retina do not communicate directly with the choroidal vessels. AQUEOUS The aqueous humour consists of a few drops of HUMOUR. an alkaline clear watery fluid, which fills the space between the cornea and the lens. 1 The iris lies in it, and divides the space into two chambers of unequal size an anterior and a posterior. The posterior is much the smaller of the two ; indeed, the iris rests on the capsule of the lens, so that, strictly speaking, there is no interval between the opposed surfaces, except a triangular interval bounded by the attachment of the iris, the ciliary processes, and the zone of Zinn. This accounts for the frequent adhesions which take place during inflammation of the iris, between the iris and the capsule of the crystalline lens. 2 A delicate layer of epithe- lium covers the posterior surface of the cornea, but nothing like a continuous membrane can be demonstrated on the iris or the capsule 1 The solid constituent is mainly composed of chloride of sodium. 2 Some anatomists describe the anterior chamber as lined by a serous mem- brane called the membrane of the aqueous humour. VITREOUS BODY. 813 of the lens. The anterior chamber is remarkable for the rapidity with which it absorbs and secretes ; as is proved, in the one case, by the speedy removal of extravasated blood ; in the other, by the rapid reappearance of the aqueous humour after the extraction of a cataract. THE VITKEOUS ^ e v^ 1 " 60118 body is a transparent, gelatinous- BODY AND THE looking substance, which fills up nearly four-fifths HYALOID MEM- o f the interior of the globe (p. 797). It can be easily separated from the retina, except at the optic disc ; in front it presents a deep depression, in which the crystalline lens is embedded. It is surrounded, except in front, by a delicate transparent membrane the hyaloid membrane which forms a capsule for the vitreous body, and is sufficiently strong to keep it in shape after the stronger tunics of the eye have been removed. When the vitreous humour has been hardened in chromic acid it is rendered somewhat opaque, and presents, especially at its outer part, a lamellar appearance. It consists of a fluid contained in the meshes of a cellular structure, which communicate freely with each other ; for if any part of it be punctured, the humour gradually drains away. 1 If examined carefully, the lamellation is seen to be arranged concentrically, the layers, as they approach the centre, becoming less firm in consistence. The _, vitreous, moreover, on a transverse section, shows a radial striation, but whether this exists naturally, or is the result of post-mor- tem changes, or from chemical reagents, is not known. Running through the middle from before backwards is a small canal canal of Stilling about a line in diameter, which ABTEEIES OF THE RETINA. contains fluid, and is broader behind than in canal of Petit (inflated). front ; this in the foetus lodges a small branch Zone of zinn (-Derated). of the retinal artery, which ramifies on the back of the capsule of the lens. The hyaloid membrane surrounds the vitreous body, except in front, and passes from the anterior border of that body to the 1 This is composed mainly of water, with albuminate of soda and mucin. 814 CRYSTALLINE LENS. margin of the lens, forming the suspensory ligament of the lens, and known as the zone of Zinn. This is best exposed by removing the ciliary processes. It appears as a dark, radiating disc, and the surface is marked by prominent ridges, which correspond with the intervals between the ciliary processes (fig. 201). These intervals are in life filled with fluid, and perhaps with the vitreous. The hyaloid membrane, with the exception of the suspensory ligament, is a structureless membrane, but the ligament presents a structure consisting in part of longitudinal elastic fibres. Beneath the mem- brane, on its inner surface, are numerous granular nucleated cells, which exhibit amosboid movements. The ligament assists in main- taining the lens in its proper position, and is firmly connected with its capsule. , If the transparent membrane between the zone of Zinn and the margin of the lens be carefully punctured, and the point of a small blowpipe gently introduced, and air or fluid injected, we may succeed in inflating a canal which encircles the lens : this is the canal of Petit (fig. 201). It is about ji^th of an inch wide, triangular in section, and bounded in front by the suspensory ligament of the lens ; behind, by the vitreous body ; and its base, by the capsule of the lens. When inflated, it becomes sacculated, as in fig. 201, owing to the foldings on the front surface of the lens. CRYSTALLINE The crystalline lens (fig. 198) is a perfectly trans- LENS. lucent solid body, situated immediately behind the pupil, partly embedded in the vitreous body, and completely sur- rounded by a capsule equally translucent. It is convex on both sides, but more so behind. In early life it is nearly spherical and soft, but it becomes more flattened, firmer, and amber-coloured with advancing age. In the adult its transverse diameter is about one- third of an inch ; its antero-posterior, one-fifth of an inch. The capsule of the lens is a transparent, elastic, and brittle membrane. It resembles in structure the elastic layer of the cornea, and is much thicker in front than behind ; in front, it is in contact with the posterior surface of the iris ; behind, it rests in the depression of the vitreous body. The capsule in front is separated from the lens by a layer of polygonal nucleated cells, and, after STRUCTURE OF THE LENS. 815 death, a layer of fluid is interposed between the capsule and the lens, constituting the liquor Morgagni', behind, no such layer of epithelium exists. No vascular connection whatever exists between the lens and its capsule. 1 The lens protrudes directly the capsule is sufficiently opened. STBUCTUKE OF The minute structure of the lens can only be THE LENS. made out after being hardened. It is soft, almost gelatinous in consistence outside, but each successive concentric layer becomes more dense, so that the central part is hard, and constitutes the nucleus. It is seen to be divided into three equal parts, by three lines, which radiate from the centre to within one- third of the circumference. Each of these portions is composed of numerous concentric layers, arranged one within the other, like the coats of an onion. If any single layer be examined with the microscope, it is seen to be composed of fibres about 5 1 O th of an inch in thickness, running in a curved direction, and connected together by finely serrated edges. On a transverse section the lens- fibres are found to be hexagonal prisms, with very little connecting substance. Between the front of the lens and its capsule is a layer of flattened cells with well-marked excentric nuclei. The beautiful dove-tailing of the fibres of the lens was first pointed out by Sir David Brewster ; and to see it in perfection, one ought to examine the lens of the cod-fish. The function of the lens is to bring the rays of light to a focus upon the retina. 2 1 The vessel of the capsule of the lens is derived from the arteria centralis retinae, and in mammalia can only be injected in the foetal state. In the reptilia, however, the posterior layer of the capsule is permanently vascular. This small artery passes forwards through the canal of Stilling to the posterior part of the capsule of the lens, on which it radiates into numerous small branches, communi- cating with branches in the iris and pupillary membrane. 2 The lens contains about 60 per cent, of water, and 30 per cent, of albuminoids. 816 DISSECTION OF THE ORGAN OF HEARING. THE parts constituting the organ of hearing should be examined in the following order : (1) the outer cartilage or pinna ; (2) the meatus auditorius externus; which leads to (3) the tympanum or middle ear ; and (4) the labyrinth or internal ear, comprising the vestibule, cochlea, and semicircular canals, which contain the distribution of the auditory nerve. The pinna or auricle consists of yellow fibro- PlNNA. _ . . . . cartilage covered with integument, and is irre- gularly concave to receive the undulations of sound. It is unevenly oval, and presents on its external aspect numerous emi- nences and hollows, which have received the following names : The circumferential folded border is called the helix ; the ridge within it, the antihelix ; between these is a curved groove, called the fossa of the helix. The antihelix bifurcates towards the front, and encloses the fossa of the antihelix (fossa scaphoidea). The conical eminence in front of the meatus is termed the tragus, on which some hairs are usually found. Behind the tragus, and separated from it by a deep notch (incisura intertragica~), is the antitragus. The lobule is the soft pendulous part placed below the concha, and consists of fat and fibrous tissue. The deep hollow, which collects the vibrations of sound, and conveys them into the external meatus, is termed the concha. The pinna is composed of yellow fibro-cartilagfe, STEUCTUEE. , , -, .,, with some fat and connective tissue, covered with integument, and attached to neighbouring parts, partly by fibrous tissue and partly by muscles. The skin is very thin, intimately adherent to the subjacent cartilage, and provided with numerous sebaceous glands, found chiefly in the scaphoid fossa and the concha. MUSCLES OF THE PINNA. 817 The cartilac/e is a single, uneven plate of fibre-cartilage, which presents all the irregularities of the external ear. The cartilage is incomplete, for there is a deficiency behind the tragus at the bottom of the concha, which is filled up with fibrous tissue. It has a tubular prolongation inwards, which forms the external part of the meatus auditorius externus. The cartilage presents several fissures (fissures of Santorini) at the anterior part of the tubular prolongation, which are completed by fibrous tissue. In the front part of the pinna, where the helix makes its first bend, is a conical projection of cartilage, termed the process of the helix. The lobule, attached to the lower part of the pinna, is a rounded projection formed of fat and connective tissue ; it is this which enlarges with age and obesity of the subject. The ligaments are : the anterior liqament, broad LIGAMENTS. . ' and strong, which passes from the process of the helix to the root of the zygoma; the posterior ligament, which extends from the cranial surface of the. concha to the mastoid process of the temporal bone. There are also intrinsic ligaments which bridge over and fill up the deficiencies in the pinna. MUSCLES OF The muscles which move the cartilage of the THE PINNA. ear as a whole, have been described (page 3). Other small muscles extend from one part of the cartilage to an- other ; but they are so indistinct that, unless the subject be very muscular, it is difficult to make them out. The following six four on the front of the auricle and two behind it are usually described : (a) The musculus major helicis runs vertically along the front margin of the helix : it arises below from the process of the helix, and is inserted into the curve of the helix as it passes backwards. (6) The musculus minor helicis, an oblique muscle, lies over that part of the helix which is connected with the concha. (c) The musculus tragicus lies vertically over the outer surface of the tragus. (d) The musculus antitragicus passes transversely from the anti- tragus to the lower part of the tail-like process of the helix behind the lobule. 3G 818 MEATUS AUDITORIUS EXTERNUS. (e) The transversus auriculae is on the cranial aspect of the pinna ; it passes nearly transversely from the back of the concha to the prominence corresponding to the fossa of the helix. (/) The obliquus auris extends vertically from the cranial aspect of the concha to the convexity below it. The arteries of the pinna are derived from the posterior auri- cular, and from the auricular branches of the temporal and occipital. The veins empty themselves into the temporal vein. The nerves are furnished by the great auricular branch of the superficial cervical plexus, the auriculo-temporal branch of the inferior maxil- lary, the posterior auricular branch of the facial, and the auricular branch of the pneumogastric. MEATUS AUDI- This oval passage leads down to the membrana TOBIUS EXTEBNUS. tympani, and conveys the vibrations of sound to the tympanum. It is about an inch and a quarter in length ; its external opening is longest in its vertical direction : its termination is broadest in its transverse. The canal inclines at first upwards and forwards, and then curves a little downwards. 1 Its floor, ' . owing to the oblique direction of the membrana tympani, is a little longer than the roof. It is not of equal calibre throughout, the narrowest part being about the middle ; hence the difficulty of extracting foreign bodies which have passed to the bottom of the canal. It is formed, partly by a tubular continuation of the car- tilage of the pinna, partly by an osseous canal in the temporal bone. The cartilaginous portion is about half an inch long, and is firmly connected to the osseous portion. The cartilage is incom- plete at the upper and back part, and the interval is filled in with fibrous tissue. The osseous portion, about three-quarters of an inch in length, is narrower than the cartilaginous portion, and is curved forwards and inwards. Its outer extremity is rough for the attachment of the cartilage ; its inner presents a narrow groove, except at the upper part, for the insertion of the membrana tympani. The 1 To obtain a correct knowledge of the length and dimensions of the meatus, sections should be made through it in different directions, or a cast be taken of it in plaster-of -Paris. TYMPANUM. 819 lower and anterior wall of the osseous portion is formed by a semi- circular plate of bone, the tympanic plate, the outer border of which is thickened and is termed the external auditory process. The skin and the cuticle are continued? down the passage, and becoming gradually thinner, form a cul-de-sac over the membrana tympani. The outer portion is furnished with hairs and ceru- minous glands, which secrete the cerumen or wax, and are only found over the cartilaginous portion of the canal. Its arteries are derived from the posterior auricular, the internal maxillary and the temporal, all branches of the external carotid artery. Its nerves come from the auriculo-temporal branch of the inferior maxillary nerve. The tiimpanum, or middle ear, is an irregular TYMPANUM. . . . J , ' . cavity in the petrous part ot the temporal bone : having on its outer side the membrana tympani ; on its inner side the labyrinth ; behind, the mastoid cells ; in front, the carotid canal ; below, the wall of the jugular fossa. It is rather less than half an inch in its long diameter ; from -i-th to -^-th of an inch between its outer and inner boundaries ; and a quarter of an inch in its vertical direction. It is lined with mucous membrane and filled with air, which is freely admitted through the Eustachian tube ; so that atmospheric pressure is equal on both sides of the membrane. A chain of small bones, the ossicles, retained in their position by ligaments and acted upon by muscles, passes across it. The use of these bones is to communicate the vibrations of the membrana tympani to the labyrinth. For this purpose one end of the chain is attached to the membrane, the other to the fenestra ovalis. The tympanum is bounded by a floor, a roof, an outer, an inner, an anterior, and a posterior wall. Its roof is formed by a thin plate of bone corresponding with the anterior surface of the pars petrosa, which separates the tympanum from the cranial cavity. The floor, which is narrow, is formed by a thin plate, corre- sponding to the jugular fossa beneath : it is perforated in front by a small aperture for Jacobson's nerve. Its outer watt is formed mainly by the membrana tympani, and by a ring of bone which affords attachment to it; the latter is 3 Q 2 820 TYMPANUM. pierced by the fissura Glaseri (which gives passage to the processes gracilis of the malleus, the laxator tympani, and the tympanic branch of the internal maxillary artery), by the foramen chordse posterius, through which the chorda tympani enters the tympanum, and by the foramen chordae anterius, which is the commencement of the canal of Huguier, for the exit of the chorda tympani nerve. The inner -wall is vertical and uneven, and presents the fol- lowing objects, beginning from above: 1. A horizontal ridge, indicating the line of the aqueeductus Fallopii ; 2. The fenestra ovalis, a reniform opening, nearly horizontal, which leads into the vestibule, but is closed in the recent state by a membrane, to which is attached the base of the stapes ; 3. Below and in front of the fenestra ovalis is a convex bony prominence, the promontory ; it is occasioned by the first turn of the cochlea, and is marked by vertical grooves, in which lie the branches of the tympanic plexus of nerves ; 4. Below and behind this is the fenestra rotunda, which lies at the bottom of a conical depression and is overhung by a projection of bone, so that it cannot be seen, except when viewed obliquely ; it leads to the scala tympani of the cochlea, but is closed in the recent state by membrane ; 5. Immediately behind the fenestra ovalis is a small conical eminence, named the pyramid, in the summit of which is a small aperture, from which the tendon of the stapedius emerges ; within the pyramid at its base is a small aperture which leads to the aquaeductus Fallopii, and transmits a special filament from the facial nerve to the stapedius. The posterior wall presents three or four openings, one of them large, which lead to the mastoid cells, and convey air into them from the tympanum. The mucous membrane of the tympanum is continued into the mastoid cells through these openings. The anterior ivall is pierced by an aperture for the transmission of a small artery from the internal carotid. Into this wall open the Eustachian tube, and (in the dry bone) the canal for the tensor tym- pani, which are separated from each other by a bony septum, the processus cochleariformis. The Eustachian tube is partly osseous, partly cartilaginous : the cartilaginous portion has been described, p. 236 ; the osseous portion, about half an inch in length, opens into the lowest part of the anterior wall, and is lined with mucous MEMBRANA TYMPANI. 821 membrane continuous behind with that of the tympanum and in front with that of the pharynx. The canal for the tensor tympani terminates in the anterior wall above the Eustachian tube as a conical projection, in the apex of which is a small aperture for the tensor muscle ; this projection is frequently called the anterior pyramid. Lastly, a nerve called the chorda tympani (a branch of the facial) runs in an arched direction from the back to the front of the tympanum, and is covered with mucous membrane. MEMBRANA The membrana tympani is a thin semi-trans- TYMPANI. parent oval disc, which completely closes the bottom of the meatus auditorius externus. Its transverse diameter slightly exceeds its vertical, and its circumference is set in a bony groove, so that it is stretched, somewhat like the parchment of a drum, on the outer wall of the tympanum. 1 Its plane is not vertical, but slants from above downwards, forming, with the floor of the meatus, an angle of 55. It is slightly conical, the apex being directed inwards towards the tympanum, and between its layers is inserted the handle of the malleus which runs downwards and forwards to a little below the centre. It is composed of three layers ; an outer, formed by an extremely thin layer of true skin ; an inner, by the mucous membrane of the tympanum ; and a middle fibrous layer ; most of the fibres radiate from the attachment of the tip of the handle of the malleus in a bowed direction, so that the membrane is not a strict cone ; other fibres are annular, forming a circumferential ring close to the osseous ring ; these stretch over a notch in the upper part of the ring (notch of Rivini) so that the membrane is here flaccid and takes the name of the membrana flaccida. The arteries to the membrane are supplied from the tympanic branch of the internal maxillary, the stylo-mastoid branch of the posterior auricular, the Vidian, and the internal carotid. OSSICULA The three small bones in the tympanum are AUDITUS. named, after their fancied resemblance to certain implements, the malleus, incus, and stapes. They are articulated 1 The transverse diameter of the membrane is 0-37 inch ; its vertical diameter 822 OSSICULA AUDITUS. to each other by perfect joints, and are so placed that the chain somewhat resembles the letter Z. Their use is to transmit the FIG. 202. vibrations iof the membrana tympani to the membrane of the fenestra ovalis, and, through it, to the fluid contained within the vestibule. But they have another use, which would be incompatible with a single bone namely, to permit the tightening and relaxation of the membrane, and thus adapt it either to resist the impulse of a very loud sound, or to THE OSSICLES OF THE EIGHT TYMPANUM. favour a more gentle one. A. Malleus. B. incus. The malleus (fig. 202, A) or hammer bone, c. Stapes. It lies horizontally , c 7 7 i i and forms a right angle with consists of an upper part or head, which is the long process of the incus. SUS p e nded from the roof of the tympanum by the suspensory ligament, and articulates posteriorly with the incus. Below the head is a narrow constriction, the neck, which is con- tinued on into a long, somewhat curved, tapering process, the manubrium or handle : it is nearly vertical, and is attached along its whole length to the upper half of the membrana tympani, passing between its inner and middle layers. The processiis gracilis projects at a right angle below the neck, runs into the Glaserian fissure, and receives the insertion of the laxator tympani. The processus brevis is a stunted projection, situated at the junction of the processus gracilis and manubrium, and touches the membrana tympani ; it receives the insertion of the tensor tympani. The incus, or anvil bone (fig. 202, B), is shaped like a tooth, with two unequal widely separated fangs. Its broad part or body pre- sents a concavo-convex articulation in front for the head of the malleus ; its long process runs nearly parallel with the handle of the malleus, and articulates with the stapes through the intervention of a small bone, the os orbiculare, which, in adult life, forms part of the long process, but in foetal life is a separate bone ; its short process is directed horizontally backwards, and its point is fixed in a small hollow at the commencement of the mastoid cells. The stapes, or stirrup bone (fig. 202, c), lies horizontally. Its head articulates with the long process of the incus. Below the head is a constriction, the neck, which receives at its posterior part MUSCLES OF THE TYMPANUM. 823 the insertion of the stapedius. Two diverging cntra pass from the head to an oval plate of bone, the base, which is attached to the membrane covering the fenestra ovalis. The tympanic bones are maintained in their positions by various ligaments. The anterior ligament of the malleus passes from the head of this bone to the anterior wall of the tympanum ; the suspensory ligament descends from the roof of the tympanum outwards to the head of the malleus, and the posterior ligament of the incus passes from the short process to the posterior wall near the mastoid cells. The ossicles are connected by an imperfect capsular ligament, which passes from the long process of the incus to the head of the stapes; and by another which passes from the head of the malleus to the incus. The base of the stapes is attached to the margin of the fenestra ovalis by an annular ligament. The surfaces of the bones forming these two little joints are covered with cartilage. The joints have also synovial membranes. MUSCLES OF The muscles, by moving the tympanic bones, THE TYMPANUM. tighten or relax the membrana tympani. The tensor tympani runs in a canal above and parallel to the Eustachian tube, from the cartilaginous part of which it arises, as well as from the apex of the petrous portion of the temporal bone. It passes backwards, and terminates in a round tendon, which enters the front wall of the tympanum through a special bony canal, and, making a sharp bend outwards, is inserted into the root of the handle of the malleus. Its nerve comes from the otic ganglion. Its action is to draw inwards the head of the malleus, and thus render the membrane tense. The laxator tympani arises from the spinous process of the sphenoid, and the cartilaginous portion of the Eustachian tube, and is inserted into the neck of the malleus close to the root of the processus gracilis. It is supplied by a branch of the facial nerve. 1 Its action is to relax the membrana tympani. The stapedius arises from the hollow of the pyramid, and its 1 This is usually regarded as a muscle, and is described here as such ; no mus- cular fibres, however, can be traced in it, so that it is probably only ligamentous in structure a fact borne out in the lower animals. 824 TYMPANUM. tendon, emerging through the aperture in the apex, runs forwards to be inserted into the neck of the stapes. 1 Its nerve is derived from the facial. By its action it increases the tension upon the fluid in the vestibule. The mucous membrane of the tympanum is continuous with that of the pharynx. It covers the ossicles, muscles, and nerves, and is prolonged into the mastoid cells. The membrane is pale and thin, and lined with columnar ciliated epithelium, except on the pro- montory, the membrana tympani, and the ossicles, where there is only a single layer of flattened cells. A branch (chorda tympani) of the facial nerve enters the tym- panum through a foramen, foramen chordce posterius, at the base of the pyramid ; it then crosses the tympanum beneath the handle of the malleus and the long process of the incus, leaves the tympanum through a foramen, foramen chordce anterius, and then traverses a canal (canal of Huguier), which runs close to the Glaserian fissure. It eventually joins the submaxillary ganglion (p. 141). The arteries supplying the tympanum are : (1) the tympanic branch of the internal maxillary, which enters through the fissura Glaseri ; (2) the stylo-mastoid branch of the posterior auricular ; (3) small branches from the ascending pharyngeal, which enter with the Eustachian tube ; (4) branches from the interna Icarotid artery ; and (5) the petrosal branch of the arteria meningea media. The veins open into the middle meningeal and the pharyngeal veins. The mucous membrane is supplied with branches from the tympanic plexus, which is formed by filaments from the tympanic branch of the glosso-pharyngeal nerve, from the carotid sympathetic plexus, and from the large and small superficial petrosal nerves. This, in consequence of its complexity, is called INTEBNAL EAB. . , . * . . . , the labyrinth. It consists or cavities excavated in the most compact part of the temporal bone, and it is divided into three parts : a middle one, called the vestibule, being the common cavity in which all communicate ; an anterior, named, from its resemblance to a snail's shell, the cochlea ; and a posterior, 1 There is a little sheath, lined with synovial membrane, to facilitate the play of the tendon in the pyramid. VESTIBULE. 825 consisting of three semicircular canals ; it communicates externally with the tympanum by means of the fenestra ovalis and rotunda, and internally with the meatus auditorius internus. These cavities are filled with a clear fluid, called the endolymph, and contain a membranous expansion, the membranous labyrinth, upon which the filaments of the auditory nerve are expanded. The vestibule, or central chamber, is an irregular oblong cavity, about one-fifth of an inch in its widest part, which is at its antero-posterior and at its vertical diameters. On its outer wall is the fenestra ovalis, which is closed in the recent state by the base of the stapes ; on its inner wall, at FIG. 203. VESTIBULE. 1. The superior semicir- cular canaL 2. The posterior semicir- cular canal. 3. The external semicir- cular canal. 4. Common opening of the superior and posterior semicircular canals. 5. Aquasductus vestibuli. 6. Aquwductus cochleae. 7. Fovea hemi-elliptica. 8. Fovea hemispherica. 9. Scala tympani. 1 0. Scala vestibuli. OSSEOUS LABYKINTH OF THE EIGHT SIDE (S6mmering). (Two and a half times its natural size.) the front part, is a shallow round depression, the fovea hemispherica, which is perforated at its lower by numerous foramina, macula cribrosa, for the transmission of the filaments of the auditory nerve. Posteriorly, this pit is bounded by a ridge, the crista vestibuli, and in some subjects there is behind this eminence the opening of a small canal, called the aquceductus vestibuli. It leads to the pos- terior surface of the pars petrosa, and transmits a small vein. In the roof is a transverse oval depression, the fovea hemi-elliptica, which lodges the utricle ; posteriorly, the five openings of the semi- circular canals open into it ; and, in front, is a large opening through which it communicates with the scala vestibuli of the cochlea. 826 SEMICIRCULAR CANALS. SEMICIECULAB The semicircular canals, three bony canals, are CANALS. situated above and rather behind the vestibule. Each canal forms about two-thirds of a circle, is compressed laterally, and is about -^th of an inch in diameter. The canals are not of equal diameter throughout ; each presents at one end a dilatation termed the ampulla, about -j^th of an inch in diameter. This dilatation corresponds to a similar dilatation of the mem- branous sac, upon which the auditory nerve expands. The canals open at each extremity into the vestibule by five openings, since one of the apertures is common to the extremities of two canals. Each canal differs in its direction ; they are named accordingly superior, posterior, and external. The superior semicircular canal (fig. 203, i) is the most anterior of the three ; its direction is vertical, and runs across the petrous bone. It rises up higher than any other portion of the labyrinth, and its ampulla is at the outer and anterior extremity, and opens into the upper part of the vestibule ; its non-ampullated extremity opens by a common orifice with the posterior semicircular canal into the back part of the vestibule. The posterior semicircular canal (fig. 203, 2) is also vertical, and runs parallel to the posterior surface of the petrous bone, conse- quently at right angles to the preceding. It is the longest of the three canals, and its ampullated extremity is at the lower end, opening into the lower and back part of the vestibule. Its upper non-dilated' end joins with that of the superior semicircular canal. The external semicircular canal (fig. 203, 3), the shortest of the three, is horizontal in position, with the convexity of the arch diverted backwards ; it opens by its extremities directly into the back of the vestibule ; the ampulla is at the outer end and opens into the vestibule just above the fenestra ovalis. The cochlea is the most anterior part of the COCHLEA. . osseous labyrinth ; it very closely resembles a common snail's shell, and is placed nearly horizontally, so that its first coil is directed forwards and outwards, and corresponds with the promontory ; while its base corresponds to the bottom of the meatus^ auditorius internus, and is perforated by apertures for the transmission of the cochlear branches of the auditory nerve. The COCHLEA. 827 diameter of its base, and also of its height, is about the same, namely, a quarter of an inch. It consists of a gradually tapering spiral tube, which winds round a central pillar, called the modiolus or colnmella. The spiral canal is divided into two parallel tubes, scalce, by a delicate lamina, partly bony, partly membranous, which is called the lamina spiralis. In the dry condition this parti- tion is only partial ; but in the recent state it is completed by a membrane. The spiral canal (fig. 203, 9, 10) is about an inch and a half long, and about the -j^th of an inch in diameter, lessening as it approaches the summit. After making two turns and a half, it terminates at the apex of the cochlea in a rounded dome the cupola. The coil at the base is the widest, the second being a FIG. 204. 1. Scala tympani. 3. Lamina spiralis 2. Scala vestibuli. ^^^^A Br~* ossen< 4. Modiolus, or central pillar. J^^^ THE OSSEOUS COCHLEA. (MAGNIFIED FIVE TIMES.) very small one. The canal has in it three openings; thus it communicates with the vestibule by an oval opening; with the tympanum by the fenestra rotunda, but which in the recent state is closed by the membrana secundaria ; and, lastly, there is the aperture of the aquceductus cochlece, which transmits a small vein from the cochlea to the internal jugular vein. The modiolus or columella (fig. 204, 4) is the central pillar of the cochlea around which the spiral canal coils, and it passes from the base to the apex. It is of considerable thickness at its base, but gradually tapers towards the apex, where at the last half coil it terminates in a half funnel-shaped curved lamella, called the infundibulum. Here the partition disappears, and is called the helicotrema, so that the scalge vestibuli and cochleae communicate with each other in this situation. The interior of the modiolus is 828 COCHLEA. composed of cancellous bone, and is traversed by numerous canals, which transmit small vessels and nerves to the lamina spiralis. One of these canals, larger than the others, runs up the centre of the modiolus nearly to the apex, and transmits a small artery, the arteria centralis modioli. On making a vertical section through the cochlea, we observe that the spiral canal is divided into three tubes, termed scalce ; the lower and largest is the scala tympani (fig. 205, s T) ; the upper is the scala vestibuli (fig. 205, sv), which is subdivided by an oblique membrane to form an outer or third tube the scala media or canalis cochlece (fig. 205, D c). TheZamma spiralis (fig. 204, 3) is the projecting partition which divides the spiral canal into two tubes or scalse : is composed on the inner half, of bone lamina spiralis ossea and on the outer half of membrane membrana basilaris. The lamina spiralis ossea ends at the cupola in a hook-like process the Jiamulus. Winding round the modiolus, close to the attachment of the lamina spiralis ossea, is a small canal the canalis spiralis modioli which is filled by the gangliform swelling of the cochlear nerve, called the ganglion spirale. The osseous lamina spiralis is seen, on a vertical section, to be com- posed of two plates, between which the structure is spongy, and presents a number of small canals for the passage of the small fila- ments of the cochlear division of the auditory nerve, in their course to the membranous part of the lamina. On examining the membranous continuation of the lamina spiralis, it is seen, not far from its attachment to the osseous zone, to be thickened into an elongated crest the limbus lamince spiralis (fig. 205, 1 1 s) which overhangs a groove, called the sulcus spiralis (fig. 205, s s) ; the upper horn of the groove is called the labium vestibulare ; the lower, the labium tympanicwn. From the labium tympanicum, the basilar membrane is continued outwards to be attached to the outer wall of the canal, and thus completes the septum. At the point of attachment of the basilar membrane with the outer wall of the cochlea -may be seen a triangular projection, which, formerly described as a muscle (coclilearis muscle), is now recognised to be a collection of connective-tissue cells, and called the ligamentum spirale (fig. 205, 1 sp). The structure of the limbus COCHLEA. 829 consists of firm connective tissue, on the under part of which are found numerous cells. Close to the junction of the limbus with the basilar membrane are a series of regularly arranged apertures, look- ing upwards to the sulcus spiralis : these are oVoid apertures for the exit of branches of the cochlear nerve. The basilar membrane forms, at the base of the cochlea, but a small breadth of the septum, the broadest part being composed of bone ; but it gradually increases in breadth towards the cupola, where it constitutes nearly the entire septum. It consists of a, FIG. 205. DIAGRAMMATIC SECTION OF A COIL OF THE COCHLEA. (From Quaill.) 8 v. Scala vestibuli. r c. Rods of Corti. D c. Ductus coclilearis. m 6. Membrana basilaris. s T. Scala tympani. I s p. Ligamentum spirals. m is. Membrane of Reissner. s s. Sulcus spiralis. 1 1 s. Limbus laminse spiralis. g s. Ganglion spirale. m T. Membrana tectoria. firm, fibrillated tissue, which is probably formed, at any rate on its upper surface, of a structure closely resembling the organ of Corti. It has been stated that in the bony cochlea there is a partial septum dividing the spiral tube into two incomplete scalas. In the recent condition the basilar membrane completes the septum dividing the upper tube into an upper canal the scala vestibuli, and a lower, the scala tympani. The upper scala is subdivided by an oblique membrane, membrane of Reissner, into two canals an 830 COCHLEA. inner, the scala vestibuli, and an outer, the canalis cochlece, the scala media or the ductus cochlearis (fig. 205, D c). The canalis cochleae terminates at the helicotrema in a cul-de-sac ; inferiorly, it is con- nected with the saccule by a long narrow duct, called the canalis reuniens. The membrane of Reissner (fig. 205, M R), is the oblique mem- brane which separates the scala vestibuli and the canalis cochleas. It is a delicate, almost structureless, layer, composed of connective tissue, continuous with the periosteum lining the upper surface of the lamina spiralis. It is smooth on its vestibular surface, and is lined with flattened connective-tissue cells ; on its cochlear surface it is covered with squamous epithelium. The inner wall of the canalis cochlese is formed by the mem- brane of Keissner covered with pavement epithelium. The outer wall, the periosteum, is thickened by a quantity of retiform con- nective tissue lined with columnar epithelial cells. An increase of this tissue is seen a little above the ligamentum spirale as a conical eminence, in which runs a small vessel, the vas spirale; midway between the vas and the attachment of Reissner's mem- brane is another thickening, consisting also of numerous blood- vessels, stria vascularis, which form anastomosing loops. The lower wall is formed by the limbus spiralis and the basilar mem- brane ; upon the latter is placed the complex structure, called the organ of Corti. The organ of Corti, placed upon the upper surface of the mem- brana basilaris, presents a slight triangular elevation outside the limbus, and winds spirally throughout the cochlea, from its base to its summit. The central part of the organ (fig. 206, T c) consists of two sets, an inner and an outer, of slanting rods rods of Corti which rest against each other at their upper extremities, thus forming a triangular tunnel, called the unnel of Corti, filled in the recent state with endolymph. The inner and the outer rods are similar in structure, but differ in shape the inner are shorter, less oblique, and have the shape of the human ulna, the outer resemble a swan's head, the head being received into the concavity of the inner rod, the part resembling the bill looking horizontally outwards. Both have a broad nucleated base, and present a COCHLEA. 831 fibrillar appearance. The inner rods are more numerous than the outer. 1 On the inner side of the inner rods is a single row of broad epithelial cells tipped with stiff ciliated processes, called the inner hair cells ; and on the outer side of the outer rods, resting on cells which are placed on the basilar membrane, are four to six rows of FIG. 200. VERTICAL SECTION OF THE FIRST TURN OF THE COCHLEA, SHOWING THE MEMBRANOUS COCHLEA AND THE POSITION OF THE ORGAN OF CORTI. (AFTER WALDEYER AND QUIN.) similar cells, termed the outer hair cells (206, o c). The bases of the outer hair cells present on one side a rounded bulge, while from the other are long processes which pass downwards to be attached 1 According to Waldeyer, in the proportion of 6,000 of the inner to 4,500 of the outer rods. 832 MEMBRANOUS LABYRINTH. to the membrana basilaris. The outer rods are placed upon nume- rous fusiform nucleated cells, cells of Deiters, whose bases rest upon the basilar membrane, and whose summits taper off into fine long cubicular processes, phalangeal, which pass between the outer hair cells to be connected to the phalanges of the reticular lamina. The lamina reticularis is the net-like membrane surmounting the summits of the outer hair cells. It is an open network, of a fiddle-shape pattern, consisting of four rows of fiddle-shaped cells termed phalanges, through which the ciliated processes of the hair cells project. To these phalanges, as before stated, are attached the phalangeal processes of the cells of Deiters. The tectorial membrane (fig. 205, M T) is the only remaining membrane to be described, and lies above and parallel to the basilar membrane, but does not extend more than half-way over it. It is connected on its inner side -with the limbus spiralis, and is then continued outwards, overlying and resting upon the rods of Corti ; at its origin it is thin, subsequently it thickens, and then gradually tapers off to end in a free extremity. It is a strong, elastic mem- brane, distinctly fibrous, especially upon its inner and thicker part. MEMBRANOUS If the bony labyrinth just described be properly LABYRINTH. understood, there will not be much difficulty in comprehending the shape of the membranous labyrinth in its in- terior a structure supporting the ultimate ramifications of the auditory nerve. It has the general form and shape of the vestibule and the semicircular canals, although smaller, and it is separated from the osseous labyrinth by a quantity of fluid called peri- lymph or liquor Cotunnii, which is secreted by the delicate serous membrane lying in the bony labyrinth. The membranous labyrinth is a sac, contained partly in the vestibule and partly in the semicircular canals : that situated in the vestibule is termed the vestibular portion; that in the bony canals, the membranous semicircular canals. The sac in the vestibule is so constructed as to form two sacs of unequal size, which indirectly communicate with each other. 1 1 From the utricle there proceeds a small canal, which lies in the aqu^ductus vestibuli ; this is joined close to its commencement by a similar canal from the saccule ; thus forming the indirect communication above alluded to. MEMBRANOUS LABYRINTH. 833 The utricle or common sinus, the larger of the two, is oval and compressed laterally, and communicates with the five openings of the membranous semicircular canals. It is lodged in the fovea hemi-elliptica, and its wall is thickest (macula acustica) close to the crista vestibuli, where the branches from the auditory nerve enter it. The saccule, the smaller, is globular and flattened, and lies in the fovea hemispherica, in front of the utricle. It is connected with the membranous canal of the cochlea by a small short duct, termed the canalis reuniens. From the saccule there passes down- wards, along the aquaeductus vestibuli, a narrow prolongation, which terminates in a pyriform dilatation, saccus endolymphaticus ; this canal is joined, at an acute angle, by a short narrow canal from the front of the utricle, so that there is a communica- tion existing throughout the entire length of the membranous labyrinth. The utricle and the saccule contain on their inner wall a minute mass of calcareous matter in connection with nerve-ends, called by Breschet the otoliths or otoconia. They are crystals of carbonate of lime, and are present in the labyrinth of all mammalia. From their greater hardness and size in aquatic animals, there is reason to believe that they perform the office of rendering the vibrations of sound sharper and more distinct. 1 MEMBRANOUS ^h membranous semicircular canals present SEMICIRCULAR the same dilatations or ampullae as the bony ones CANALS. a t one gj^ and at this part they nearly fill their bony cases ; but in the rest of their extent the diameter of the membranous canal is not more than one-third to one-fifth that of the bony. At the ampullated extremity the sac is connected on its outer aspect by blood-vessels and nerves to the periosteum, forming on section a transverse projection, called the septum transversum or crista acustica, which forms a partial septum. The membranous semicircular canals consist of three layers, an 1 For a detailed description of the relation of the otoliths with the hair-like processes of the nerve-filaments, the student is referred to an article by Dr. Urban Pritchard in the Quarterly Journal of Microscopic Science, October 1876, entitled ' The Termination of the Nerves in the Vestibule, and Semicircular Canals of Mammals.' 3 H 834 AUDITORY NERVE. outer or fibrous layer, which is connected with the periosteum by blood-vessels, and contains irregular pigment-cells; a middle or tunica propria, clear and structureless ; and an inner or epithelial layer, which lines the inner space of the tunica propria. At the ampullae the epithelial layer is composed of the columnar variety, upon which are arranged cells of a spindle shape, having delicate ciliated processes (auditory hairs) projecting into the endolymph. The membranous labyrinth is protected, inside and out, by fluid. The fluid in the interior is termed the endolymph or liquor Scarpce, and the thin layer between it and the bone, the perilymph or liquor Cotunnii ; thus the delicate nervous membrane is placed between two layers of fluid. DISTRIBUTION The auditory nerve, or the eighth cranial nerve, OF THE AUDITOKY passes down the meatus auditorius internus, and, NEKVE - at the bottom of it, divides into an anterior and posterior branch, which, after breaking up into numerous fasciculi, are distributed to the cochlea and to the vestibule. The vestibular nerve divides into five branches, which proceed to the utricle, the saccule, and the three ampullae of the semi- circular canals, respectively : those for the utricle, and the superior and external semicircular canals enter the vestibule along the crista vestibuli ; that for the saccule enters through the fovea hemi- spherica, and that for the posterior semicircular canal is continued along a bony canal to its termination. The nerves to the semi- circular canals enter the ampullae by a forked swelling which corresponds to each septum transversum. The cochlear division of the auditory nerve is a short, thick branch, which breaks up into numerous filaments at the bottom of the meatus auditorius internus. These enter the canals in the base of the modiolus, and then arch outwards between the plates of the lamina ossea. In their course outwards between the plates, they pass through the spirally arranged ganglionic cord, ganglion spirale, beyond which they form a wide plexus. They are collected to- gether close to the free border of the osseous zone, forming a very minute nerve-plexus, whose filaments interlace freely ; they then AUDITORY NERVE. 835 enter the membranous zone to be connected with the inner hair-cells of the organ of Corti. 1 The vessels which supply the cochlea are from ten to twelve in number, and are derived from the auditory artery ; they, like the nerves, enter the bony canals of the modiolus, and then turn out- wards to ramify upon the osseous zone, supplying its periosteum. The plexus formed by these branches communicates with a vessel known as the vas spirale, which runs longitudinally in the liga- mentum spirale to the outer attachment of the membrana basilaris. The veins from the cochlea terminate in the superior petrosal sinus, having previously joined those of the vestibule and semicircular canals. i 1 Some anatomists describe filaments as passing between the rods of Corti to end in the outer hair-cells. 3 H 2 DISSECTION OF THE MAMMARY GLAND. THE form, size, position, and other external characters of the mammary gland in the female vary more or less in different persons. The longest diameter of the gland is in a direction upwards and outwards towards the axilla ; its thickest part is at the centre, and the fulness and roundness of the gland depend upon the amount of fat about it. Its deep surface is flattened in adaptation to the pectoral muscle, to which it is firmly connected by an abundance of areolar tissue. In its vertical direction the breast corresponds to the space between the third and sixth or seventh ribs ; in its lateral direction, to the space between the side of the sternum and the axilla, while the nipple corresponds to the fourth rib, or a little below it. It is enclosed by a fascia, which not only supports it as a whole, but penetrates into its interior, so as to form a framework for its several lobes ; hence it is that, in cases of mammary abscess, the matter is apt to be circumscribed, not diffused. The nipple (mammilla) projects a little below the centre; it is surrounded by a coloured circle, termed the areola ; this circle is of a rose-pink colour in virgins, but in those who have borne children of a dark brown. It begins to enlarge and grow darker about the second or third month of pregnancy, and these changes continue till parturition. The areola is abundantly provided with papilte, and with subcutaneous sebaceous glands, to lubricate the surface during lactation ; the areola as well as the nipple is destitute of fat. The gland itself consists of distinct lobes held together by firm connective tissue, and provided with separate lactiferous ducts. Each lobe divides and subdivides THE MAMMARY GLAND. 837 into lobules, and the duct branches out accordingly. 1 Traced to their origin, we find that the ducts commence in clusters of minute cells, and that the blood-vessels ramify minutely upon these cells ; altogether, then, a single lobe might be compared to a bunch of grapes, of which the stalk represents the main duct. The main ducts (galactophorous ducts) from the several lobes, from fifteen to twenty in number, converge towards the nipple, and, just before they reach it, become dilated into small sacs or ampullce, two or three lines wide ; after this they run up to the apex of the nipple, and, running parallel, terminate in separate orifices. The vesicles and the galactophorous ducts are lined with columnar epithelium, except at their orifices, where it becomes squamous. The arteries of the gland are derived from the long thoracic, the internal mammary, and the intercostals ; the nerves come from the anterior and lateral cutaneous branches of the intercostal nerves, and from the descending branches of the cervical plexus. The veins diverge from the nipple, and terminate in the axillary and internal mammary veins. The lymphatics run chiefly to the axillary glands, but some pierce the front of the intercostal spaces to join the anterior mediastinal glands. 1 It is observed, in some cases, that one or more lobules run off to a consider- able distance from the main body of the gland, and lie embedded in the subcu- taneous tissue. This should be remembered when it is necessary to remove the entire gland. 838 DISSECTION OF THE SCROTUM AND TESTIS. THE scrotum is a pouch of skin for the lodgment of the two testes. They are originally developed in the abdomen, and descend into the scrotum about the eighth month of intra-uterine life. In their descent they push before them certain coverings derived from the strata of the abdominal walls, through which they pass, and which constitute, with the layers of the scrotum, the coverings of the testes. The scrotum presents in the middle a ridge, the raphe, on each side of which it is corrugated into transverse folds or rucjce. It is divided by a dis- tinct septum into two lateral halves, of which the left is the longer. The scrotum consists of two layers, the integument and the dartos. The integument is of dark colour, thrown into transverse rugas, and provided with sebaceous glands and hairs. The dartos is a thin layer, consisting of muscular fibres of the involuntary kind, like those of the bladder and intestines. It serves to corrugate the loose and extensible skin of the scrotum, and in a measure to support and brace the testes. It is more abundant in the anterior than the posterior part of the scrotum. Beneath the dartos, and partly intermingled with it, is a large quantity of loose connective tissue, remarkable for the total absence of fat. Together with the dartos it forms a vertical partition between the testes, termed the septum scroti, which passes from the raphe to the under aspect of the penis, as far as its root. It is not a complete partition, since air or fluid will pass from one side to the other. The great abundance and looseness of this tissue explains the enormous swelling of the scrotum in cases of anasarca, and in cases where urine is extravasated into it in consequence of rupture or ulcer ation of the urethra. The coverings of the testes, in addition to these two layers of the THE SCROTUM AND TESTES. 839 scrotum, are the intercolumnar or spermatic fascia, derived from the pillars of the external abdominal ring, the cremasteric fascia, derived from the lower border of the internal oblique of the abdo- men, the infundibuliform fascia, derived from the fascia transver- salis ; and, lastly, the tunica vaginalis, derived from the parietal layer of the peritoneum. The spermatic fascia, cremaster muscle, and the infundibuli- form fascia have been described (pp. 427, 429, 436). Each of these coverings cannot be demonstrated under ordinary circumstances, because they are so blended together : but they can be shown when hypertrophied in the case of old and large herniae. The arteries supplying the tissues of the testis are the cremas- teric branch of the deep epigastric artery, the superficial and deep external pudic branches of the common femoral artery, and the superficial perineal branch of the internal pudic artery. The nerves are derived from the ilio-inguinal, the genital branch of the genito-crural, the superficial perineal nerves, and the inferior pudendal branch of the lesser sciatic nerve. The lymphatics pass to the inguinal glands. The testis is a gland of an oval shape with flattened sides, suspended obliquely in the scrotum by the spermatic cord, so that its upper end is directed forwards and outwards, its lower end in the reverse direction. The left is generally a little lower of the two. Each testis is from an inch and a half to two inches in length, an inch in breadth, and an inch and a quarter from behind forwards. Its weight is from six to eight drachms, but few organs present greater variations in size and weight, even in men of the same age ; generally speaking, the left is the larger. The front and sides of the testis are convex and smooth, and are covered with the visceral layer of the tunica vaginalis ; but the posterior surface is only partially invested, as there is here placed a long narrow body, termed the epididymis ; * this is not a part of the testis, but an appendage to it, formed by the convolutions of its long excretory duct. The epididymis consists of a larger upper end called the globv* 1 From SiSv/j.os, a testicle. 840 THE TESTIS. major (fig. 207, 5) and of a lower smaller end, the globus minor (fig. 207, 6), the two being connected together by the body. The globus major is connected with the testicle by radiating efferent ducts ; the globus minor is only connected with the organ by con- nective tissue and the tunica vaginalis. The upper and lower ends and the outer surface of the epididymis are covered with serous membrane, as is also the body, except at its anterior border, where the vessels enter and emerge. Situated between the globus major and the body of the testis are one or two small pedunculated bodies, called the hydatids of Morgagni they are formed by pouch- FIG. 207. 1. Mediastinum testis, con- taining the rete testis. 2, 2. Trabeculse. 3. One of the lobules. 4, 4. Vasa recta. 5. Coni vasculosi, forming the ' globus major ' of the epi- didymis. 6. Globus minor, or lower end of epididymis. 7. Vasdeferens. DIAGRAM OF A VERTICAL SECTION THROUGH THE TESTICLE. ings of the tunica vaginalis, and are filled with blood-vessels bound together by connective tissue. 1 A considerable quantity of unstriped muscular tissue exists at the posterior part of the epididymis and testis beneath the infundi- buliform fascia, and has been described by Kolliker as the inner muscular tissue. COVERINGS OP The testicle is invested by three coverings, which THE TESTICLE. are __i ^ A serous membrane, called the tunica vaginalis, to facilitate its movements. 2. A strong fibrous mem- 1 The largest, which lies upon the top of the testis, is stated to be the vestige of the Miillerian duct. THE TESTIS. 841 brane, called the tunica albuginea, to support the glandular struc- ture within. 3. A delicate vascular stratum, termed the tunica vasculosa, which consists of a layer of minute blood-vessels. The tunica vaginalis is a closed serous sac, one part of which, tunica vaginalis propria, adheres closely to the testis ; the other, tunica vaginalis reflexa, is the reflected portion, adherent to the inner surface of the infundibuliform fascia, and loosely surrounds the testicle. On opening the sac, it will be seen that the visceral layer completely covers the testicle, except behind, where the vessels and duct are situated (fig. 207) ; and that it covers the outer part of the epididymis in front and behind, forming here a pouch called the digital fossa. The parietal layer extends upwards for a variable distance upon the cord and below the testicle. The interior of the sac is smooth and polished, like all other serous membranes, and lubricated by a little fluid. An excess of this fluid gives rise to the disease termed hydrocele. The portion of the process of peritoneum between the internal abdominal ring and the upper part of the tunica vaginalis testis (the spermatic portion of the tunica vaginalis) becomes, in the process of development, converted into a fibrous cord, which may usually be recognised, but which is sometimes so atrophied as not to be recognised. The tunica vaginalis testis was originally derived from the peritoneum. In some subjects it still communicates with that cavity by a narrow canal, and is therefore liable to become the sac of a hernia (see diagram, p. 444). Such hernige are called con- genitala misleading term, since they do not necessarily take place at birth, but may occur at any period of life, even in very old age. 1 Sometimes the communication continues through a very contracted canal, open to the passage of fluid alone ; or the com- munication may be only partially obliterated, and then one or more isolated serous sacs are left along the cord. Such a one, when distended with fluid, gives rise to hydrocele of the cord. The tunica albuginea is a dense, white, inelastic membrane, 1 It would be a better term to call this lesion a hernia in the tunica vaginalis, denoting thereby its anatomical position ; at the same time implying a congenital arrest in development, and without limiting its occurrence to any age of life. 842 THE TESTIS. composed of white fibrous tissue, interlacing in every direction ; analogous to the sclerotic coat of the eye. It completely invests the testis, but not the epididymis. It is covered by the visceral layer of the tunica vaginalis, except behind and at the attachments of the epididymis. At the posterior part of the gland it penetrates into its substance for a short distance, and forms an incomplete vertical septum, termed, after the anatomist who first discovered it, corpus Highmorianum, and subsequently by Sir A. Cooper, mediastinum testis (fig. 208, 5). The mediastinum testis transmits the blood-vessels of the organ, and contains also the network of seminal ducts, called the FIG. 208. 1. Spermatic artery. 2. Vas deferens. 3. Deferential artery. 4. Epididymis. 5. Mediastinum testis. 6. 6. Cavity of tunica vaginalis. TRANSVERSE SECTION THROUGH THE LEFT TESTICLE. (The dots show the reflections of the tunica vaginalis.) rete testis, shown in the diagram (fig. 207). This septum gives off from its front and sides a number of diverging slender fibrous cords, trabeculce testis, 1 which traverse the interior of the gland, and are attached to the inside of the tunica albuginea. They serve to maintain the general shape of the testicle, to support the numerous lobules of which its glandular substance is composed, and to convey the blood-vessels into it. These septa, as well as the mediastinum from which they proceed, are readily seen on making a transverse section through the gland (fig. 208). 1 Kolliker has demonstrated unstriped muscular fibres upon the septa as well as the mediastinum. THE TESTIS. 843 The tunica vasculosa (pia mater testis) consists of a multitude of minute blood-vessels, formed by the ramifications of the spermatic artery, and held together by delicate areolar tissue. It covers the inner surface of the tunica albuginea, and gives off branches, which ran with the fibrous septa into the interior of the gland. Minute structure. When the testis is cut into, its surfaces become convex, and present a dirty fawn colour. The section is soft and pulpy, and is seen to consist of numerous lobules, between two hundred and fifty and four hundred in number, 1 of various sizes, the central being the larger, and contained in the compart- ments formed by the fibrous septa proceeding from the mediastinum testis. A few only of these lobules are shown in the diagram. These lobules are conical in shape, their bases being anterior and their apices at the mediastinum, and are bounded by the septa which pass from the mediastinum. They contain two or more minute con- voluted tubes, tubuli seminiferi, which may be easily unravelled, in consequence of their tough walls. Their number has been estimated to be between 800 and 900, and each has a length of about two feet and a diameter averaging y-^th of an inch. They commence either by communications with other tubes or by caecal extremities, and they frequently exhibit small bulgings in their course back- wards. The walls of the tubuli consist of a membrana propria, composed of several layers of flattened cells, and the walls are lined with several irregular layers of cells, between which may, under the microscope, be distinguished seminal filaments in various stages of development. The tubuli seminiferi are connected to- gether by a delicate interstitial tissue, the laminas of which are surrounded by flattened epithelioid cells, and between them are lymph-spaces in direct communication with the lymphatics of the testicle. In this intertubular tissue ramify the minute branches of the spermatic artery which surround the tubules. After pursuing a convoluted course, the tubules unite in front of the mediastinum into from thirty to fifty straight vessels, vasa recta, which penetrate the mediastinum testis, and these form an anastomosing plexus of seminal tubes, called the rete testis (fig. 207). This lies along the back of the gland. From the upper part of the 1 The larger estimate is that by Krause ; the smaller, that by Berres. 844 THE TESTIS. rete, its tubes converge to form twelve to fifteen tubes, termed vasa efferentia, which perforate the tunica albuginea, and convey the seminal secretion to the upper part of the epididymis. The vasa efferentia are at first straight, but ultimately form, a number of coils termed coni vasculosi, which collectively constitute the globus major of the epididymis. The coni vasculosi are about -g^th of an inch in diameter, and about six to eight lines long ; when unravelled they attain a length of six to eight inches. At the globus major the smaller tubes terminate in a single duct, the canal of the epididymis, which in its descent describes an extremely tortuous coil, constituting the body and globus minor of the epididymis. The length of the canal of the epididymis is, in its natural condition, about three inches, but when unravelled it is nearly twenty feet in length. The diameter of the canal at its commencement is about ^"th of an inch ; at the globus minor about -^th of an inch, after which it again increases in diameter. It is lined with columnar ciliated epithelium. The vas deferens begins at the lower part of the globus minor ; at first it is somewhat convoluted, but, as it ascends behind the epididymis, it becomes subsequently straight, and joins the other component parts of the cord. After passing through the inguinal canal, it enters the abdomen through the internal ring. It then winds round the outer side of the deep epigastric artery, and, after crossing over the external iliac artery and vein, it enters the pelvis, curves round the side and lower part of the bladder, and empties itself into the prostatic part of the urethra, after running a course of about two feet. Its course in the abdomen has been previously described (p. 535). In connection with the anterior aspect of the cord, just above the epididymis, are two or three small masses of convoluted tubes, which are known as the organ of Gir aides, or the par epididymis. They are lined with squamous epithelium, and are probably the remains of part of the Wolffian body. The vas aberrans is a small convoluted tubule, with a cascal extremity, found between the epididymis and the cord, and com- municating usually-with the canal of the epididymis. It is about an inch in length, but, when frayed out, varies from two to twelve SPERMATIC CORD. 845 inches in length. It, like the organ of Giraldes, is connected with a foetal structure the Wolffian body. The vas deferens consists of an external or connective-tissue coat ; a middle or muscular coat, composed of longitudinal and circular fibres intermingled with elastic tissue ; and an internal or mucous coat, arranged in longitudinal folds, and lined with columnar epithelium. It can always be recognised from the other constituents of the spermatic cord by its hard whipcord-like feel. SPEKMATIC The spermatic cord begins at the internal ring, CORD. traverses the inguinal canal, and extends to the testis, where its component parts pass to their respective desti- nations. It is composed of the spermatic vessels, nerves, and lymphatics ; of the vas deferens, with the deferential artery, a branch of the superior vesical ; of the cremaster muscle, and the cremasteric artery, a branch of the deep epigastric. The coverings of the cord have been described with the anatomy of the parts concerned in inguinal hernia (p. 439). The spermatic artery in its course along the cord becomes remarkably tortuous ; it enters the back part of the testicle, and breaks up into a number of fine ramifications, which spread out on the inner surface of the tunica albuginea. The spermatic veins leave the testis at its back part, and, as they ascend along the cord, become extremely tortuous and form a plexus, termed the pampiniform plexus. They lie in front of the vas deferens and unite to form a single vein, which on the right side opens into the inferior vena cava, and on the left side into the left renal vein. It is usually stated that these veins are destitute of valves ; and this fact is adduced as one of the reasons for the occurrence of varicocele. It is, however, certain that the larger veins do contain valves. The lymphatics of the testis pass through the lumbar glands ; hence these glands, and not the inguinal, become affected in malig- nant disease of the testis. The nerves of the testicle are derived from the sympathetic. They descend from the abdomen with the spermatic arteries, and come from the aortic and renal plexuses, with a few filaments from the hypogastric plexus, which surround the deferential artery 846 DESCENT OF THE TESTIS. (p. 540). This accounts for the ready sympathy of the stomach and intestines with the testicle, and for the constitutional effects of an injury to it. DESCENT OF The testicle is originally developed in the lumbar THE TESTIS. region, immediately below the kidney, and is loosely attached to the back of the abdomen by a fold of peritoneum, termed the mesorchium, along which its vessels and nerves run up to it, as to any other abdominal viscus. From the lower end of the gland a fibrous cord, termed the gubernaculum testis, 1 pro- ceeds to the bottom of the scrotum. There is no evidence to warrant the assumption that the gradual contraction of the guber- naculum effects the descent of the testis. The organ begins to descend from the lumbar region about the fifth month of foetal life, reaches the internal ring about the seventh, and about the ninth has entered the scrotum. Its original peritoneal coat is retained throughout; but as it enters the inguinal canal, the peritoneal lining of the abdomen is pouched out before it, and eventually becomes the tunica vaginalis reflexa. Immediately after the descent of the testis, its serous bag communicates with the abdomen, and in the lower animals continues to do so throughout life. 2 But in the human subject the canal of communication soon begins to close. It closes at the upper extremity first, 3 and the closure is generally complete in a child born at its full time. 4 This provides against the occurrence of ruptures, to which man, 1 Mr. Curling considers the gubernaculum testis to be a muscular cord. See his Observations on the Structure of the Gubernaculum, and on the Descent of the Testis in the Foetus : Medical Gazette, April 10, 1841. This is denied by Cleland, see Meclwnism of the Gubernaculum Testis, 1856. 2 According to Professor Owen, the African orang-outang (Simia troglodytes] is the only exception to this rule. In this animal it is interesting to observe that the lower extremities are more fully developed as organs of support, and there is a ligamentum teres in the hip- joint. 8 The frequency of hernia in the funicular portion of the vaginal process of the peritoneum hardly bears this out. 4 Camper has shown that the canal on the right side is nearly always open at birth, whereas that on the left is usually closed. This explains the greater fre- quency of hernia on the right side in children under one year old. Thus out of 3,014 cases of inguinal hernia seen at the City of London Truss Society under one year, 2,269 occurred on the right side, and 745 on the left ; or in the proportion of 3tol. DESCENT OF THE TESTIS. 847 owing to his erect position, is more exposed than animals. At the end of the first month after birth, the canal is entirely obliterated from the internal ring to the testis. Sometimes, however, this obliteration fails, or is only partial ; hence may arise congenital hernia, or hydrocele. The possible existence of a communication between the tunica vaginalis and the peritoneal cavity of the abdomen, is one reason, among many, why caution should be observed in treating hydroceles in children with stimulating injections. INDEX. ABD Abdomen, dissection of, 419 parts exposed on opening, 448 regions of, 419 superficial fascia of, 421 surface marking of, 419 Abdominal muscles, functions of, 433 ring, external, 427 internal, 436 walls, arteries of, 436 nerves of, 434 Abducens, nerve, 19, 60, 750 Accelerator urinte, 511 Acervulus cerebri, 769 Achillis, tendo, 675 Adami, pomum, 240 Adductor brevis, 631 longus, 629 magnus, 632 Ala cinerea, 773 Alimentary canal, anastomoses on, 606 length of, 454 Ampulla of semicircular canals, 826 of rectum, 531 Amygdala cerebelli, 776 Anal glands, 506 fascia, 528 Anastomoses, alimentary canal, 606 Angular artery, 40 vein, 41 Ani, sphincter, 508 levator, 538 Ankle-joint, ligaments of, 707 movements of, 709 Annular ligament of hand, 358 posterior ligament of forearm, 389 ligament of ankle, 646 Annulus ovalis, 200 Ansa hypoglossi, 85, 110 Antitragus, 816 ART Antihelix, 816 fossa of, 816 Aorta, abdominal, 481 arch, course of, 174 descending thoracic, 182 great sinus of, 176 relations of, 175 ascending part of, 176 descending part of, 177 transverse part of, 176 Aponeurosis, epicranial, 2 gluteal, 616 lumbar, 373 pharyngeal, 226, 230 supra-hyoid, 93 vertebral, 279, 373 Apparatus ligamentosus colli, 29& Aquseductus cochleas, 827 Fallopii, 268 Sylvii, 771 vestibuli, 825 Arachnoid membrane of brain, 715 cavity of, 8 of spinal cord, 783 Arantius, corpus of, 204 nodules of, 204 Arbor vite of cerebellum, 778 uterus, 569 Arch, crural, 426, 619 parts passing under, 620 deep, 622 Arm, upper, cutaneous nerves of, 325 musculo-cutaneous nerve of, 337 surface marking of, 324 Arnold's ganglion, 146 nerve, 6, 147 Arteries : acromial thoracic, 310 alar thoracic, 317 alveolar, 136 3l 850 INDEX. ART Arteries (continued) anastomotica magna of brachial, 335 femoral, 641 angular, 40 anterior cerebral, 717 ciliary, 804 communicating, 718 perforating, of foot, 689 peroneal, 682 spinal, 719 superior cerebellar, 720 tibial, 649 aorta, 174 abdominal, 481 branches of. 464 arch of, 175 ascending, 176 descending, 177 transverse, 176 descending thoracic, 182 articular, of knee, 668 auditory, 720, 835 auricular anterior, 128 posterior, 4 axillary, 315 azygos, 677 back, 291 fcasilar, 719 transverse of, 720 bicipital, 178 brachial, 332 brachio-cephalic, 178 of brain, 717 bronchial, 194, 224 buccal, 136 bulb, 519 calcanean internal, 682, 688 capsular, 581 carotid, common, 81, 179 external, 95 internal, 23, 144, 270, 717 carpal of radial, anterior, 347 posterior, 347 ulnar, anterior, 349 posterior, 349, 397 centralis modioli, 828 retinae, 58, 812 cerebellar, anterior superior, 720 posterior inferior, 720 superior, 720 cerebral anterior, 717 middle, 718 posterior, 720 cervical ascending, 120 superficial, 121, 376 ART Arteries (continued) transverse, 121 cervicis princeps, 107 profunda, 123 choroid anterior, 719 posterior, 720 ciliary anterior, 58 long, 58 short, 58 circle of Willis, 719, 720 eirculus major, 804 minor, 804 circumflex of arm, anterior, 319 posterior, 318, 381 thigh, external, 639 internal, 639 circumflexa ilii, deep, 438, 492 superficial, 423, 611 coccygeal, 663 coeliac axis, 466 colica dextra, 472 media, 472 sinistra, 473 comes nervi ischiatici, 663 mediani, 352 phrenici, 159 'communicating anterior, of tibial, 682, 718 posterior of tibial, 719 coronaria ventriculi, 466 coronary, 207 coronary, of lip, inferior, 40 superior, 40 corpus cavernosum, 519 cremasteric, 437 crico-thyroid, 96 cystic, 468 deep cervical, 123 external pudic, 613 palmar arch, 365 temporal, 135 deferential, 540 dental anterior, 136 inferior, 135 superior, 136 digital, of hand, 357 toes, 688 dorsalis hallucis, 651 indicis, 398 linguae, 106 pedis, 650 pollicis, 398 scapulae, 385 dorsal interosseous of hand, 397 of foot, 651 INDEX. 851 ART Arteries (continued) dorsal, of penis, 519 epigastric, deep, 437 superficial, 423 ethmoidal anterior, 58 posterior, 58 facial, 38, 98 femoral, 630 superficial, 631 deep, 638 frontal, 4, 59 gastric, 466 gastro-duodenalis, 468 gastro-epiploica dextra, 468 sinistra, 468 gluteal, 540, 657 inferior, 663 helicine, 561 hffimorrhoidal external, 508 middle, 541 superior, 473 hepatic, 467, 580 hyoid inferior, 96 superior, 106 hypogastric, 540 ileo-colic, 472 iliac common, 490 external, 492 internal, 539 ilio-lumbar, 539 inferior labial, 39 infraorbital, 48, 136 infraspinous, 121, 376 innominate, 178 intercostal, 190, 436 anterior, 159 collateral, 191 dorsal of, 191 superior, 122 interlobular, 581 interosseous, anterior, 352 common, of forearm, 349 of hand, 366 posterior, 395 recurrent, 395 intestini tenuis, 472 labial inferior, 39 superior, 40 lachrymal,- 58 laryngeal, superior, 96 lateral, of nose, 40 sacral, 540 spinal, 719 lingual, 105 long ciliary, 804 ART Arteries (continued) lumbar, 485 malleolar, 650 mammary, internal, 122, 159, 436 masseteric, 135 mastoid, 108 maxillary, external, 38 internal, 133 mediastinal, 159 meningea media, 134 parva, 16, 135 meningeal, 16 anterior, 16 middle, 16 posterior, 16, 107, 719 mental, 49 mesenteric, inferior, 473 superior, 472 metatarsal, 651 middle cerebral, 718 hffimorrhoidal, 541 sacral, 543 temporal, 128 vesical, 540 muscular, to eye, 59 musculo-phrenic, 159, 437 mylo-hyoid, 135 nasal, 59, 136 nutrient, of femur, 640 humerus, 335 obturator, 541, 643 pubic branch of, 541 occipital, 4, 107 cesophageal, 194 of gastric, 466 omental, 469 ophthalmic, 57 orbital, 134 ovarian, 485 palatine, ascending, 98, 143 descending, 136 palmar arch, deep, 365 superficial, 355 interosseous, 366 palmaris profunda, 365 palpebral, inferior, 59 superior, 59 pancreatic, 468 pancreatico-duodenal, inferior, 472 superior, 468 perforating, of hand, 366 foot, 689 thigh, 640 intercostal, 159 3 i 2 852 INDEX. ART Arteries (continued) pericardiac, 159 perineal, superficial, 510 transverse, 511 plantar, external, 688 internal, 687 peroneal, 681 anterior, 682 petrosal, 16, 134 pharyngeal, ascending, 109, 145 meningeal of, 109 pharyngeal, branches of, 145 phrenic, 482 popliteal, 667, 676 articular branches of, 677 branches of, 667 posterior communicating, 719 profunda inferior, 333 superior, 333, 387 princeps pollicis, 365 pterygoid, 136 pterygo-palatine, 136 pubic, of deep epigastric, 437 'obturator, 541 pudic, internal, 517, 542, 663 deep external, 613 superficial external, 423, 611 pulmonary, 194, 223 pyloric, 468 radial, 346 in palm, 365 at back of wrist, 397 recurrent, 347 radialis indicis, 365 ranine, 106 receptaculi, 23 rectum of, 532 renal, 484, 593 branches of, 594 sacral, lateral, 540 middle, 486, 548 scalp, of, 4 scapulas dorsalis, 318 scapular, posterior, 121, r 376 supra-, 121, 375 sciatic, 542, 662 septum of the, 40, 136 sigmoid, 473 spermatic, 484, 845 spheno-palatine, 136 spinal, anterior, 719 lateral, 120 posterior, 719 splenic, 468, 587 sternal, 159 ART Arteries (continued) sterno-mastoid, inferior, 121, 375- middle, 96 superior, 107 stylo-mastoid, 108 subclavian, left, 115, 179 right, 113 sublingual, 106 submaxillary, 98 submental, 98 subscapular, 317 superficialis volse, 347 supra-acromial, 121, 375 supra-orbital 4, 58 supra-renal, 484 supra-scapular, 121, 375 subscapular of, 121 sural, 678 tarsal, 651 temporal, 127 deep, 135 superficial, 4 testis, of, 839 thoracica-acromialis, 310 alaris, 317 longa, 317 superior, 310 thymic, 159 thyroid axis, 120 inferior, 120 superior, 96 tibial, anterior, 649 posterior, 681 recurrent, 650 tonsillar, 98 transverse cervical, 121 facial, 41 transversalis perinei, 511 tympanum, of, 824 ulnar, 348 anterior recurrent, 349 posterior recurrent, 349 ulnaris, profunda, 357 uterine 566 vaginal, 567, 581 vasa brevia, 468 vertebral, 119, 719 lateral spinal of, 120, 719 posterior meningeal of, 719 vesical, inferior, 540 middle, 540 superior, 540 Vidian, 136 Articulations, acromio-clavicular, 403 ankle, 707 INDEX. 853 ART Articulations (continued) astragalo-calcanean, 709 astragalo-scaphoid, 710 atlo-axoid, 300 calcaneo-cuboid, 711 calcaneo-scaphoid, 710 carpal, 413 carpo-metacarpal, 415 costo-sternal, 302 elbow, 408 hip, 696 interphalangeal, 418, 714 metacarpal, 416 metacarpo-phalangeal, 417 metatarsal, 713 metatarso-phalangeal, 714 occipito-atlantal, 298 pubic, 696 radio-carpal, 412 radio-ulnar, inferior, 411 superior, 409 sacro-coccygeal, 694 sacro-iliac, 694 sacro-vertebral, 693 scapulo-clavicular, 403 shoulder, 405 sterno-clavicular, 401 tarsal, 711 tarso-metarsal, 713 temporo-maxillary, 303 tibio-fibular, inferior, 707 superior, 706 trapezium and thumb, 415 wrist, 412 Aryteno-epiglottideus, 249 inferior, 251 superior, 251 Aryteno-epiglottidean folds, 244 Arytenoid cartilages, 242 Arytenoideus, 249 Atrium of auricle, 199 Auditory meatus, external, 818 nerve, 19, 751, 834 Auerbach's plexus, 604 Aurem attollens, 3 attrahens, 3 retrahens, 3 Auricle of ear, 816 Auricle of heart, right, 199 left, 205 muscular fibres of, 210 Auricular appendix, 199 artery, anterior, 128 posterior, 108 great, nerve, 68 BRA Auricular nerve, 147 posterior, 6, 108 nerve of pneumogastric, 6 vein, 4, 108 Auriculo-temporal nerve, 6, 128, 139 Axilla, dissection of, 312 Axillary artery, 315 ligature of, 311 fascia, 312 plexus of nerves, 320 vein, 319 Axis cosliac, 466 thyroid, 120 Azygos artery, 677 veins, 182, 183 Back, arteries of, 291 cutaneous nerves of, 367 muscles of, 278 nerves of, 289 Band, ilio-tibial, 615 Bartholin, duct of, 104 glands of, 523 Basilic vein, 327 Bell, nerve of, 324 Bertini, columns of, 590 Bichat, fissure of, 762 Biliary ducts, 581 Biceps of arm, 329, 406 thigh, 669 Bladder, 532 arteries of, 551 female, 563 ligaments of, 503, 526, 529 nerves of, 551 position of, 532 sphincter of, 548 structure of, 548 trigone of, 550 uvula of, 550 veins of, 551 Bochdalek, ganglion of, 260 Brachial artery, 332 plexus of nerves, 320 Brachialis anticus, 331 Braehio-cephalic artery, 178 veins, 172 Brain, 715 annectent gyri, 738, 739 arteries of, 717 ' central fissure of, 735 cornua of, 758 membranes of, 8, 715 removal of, 12 division of, 721 854 INDEX. BRA Brain (continued) fissures of, 734, 735 peculiarities of circulation in, 721 weight of, 722 Breasts, 836 Bronchi, 217 Bronchial arteries, 194, 224 lymphatic glands, 195 Bruch, membrane of, 801 Brunner's glands, 603 Buccal fascia, 37 glands, 38 Buccinator, 36 Bucco-pharyngeal fascia, 38 Burns' ligament, 618 Bursse, biceps, near tendon of, 406 of carpus, 387 over knuckles, 387 olecranon, 387 patella, 636 under coraco-acromial ligament, 381 coraco-brachialis, 331 deltoid, 381 gastrocnemius, 674 gluteus maximus, 656 medius, 656 gracilis, 629 latissimus dorsi, 372 ligamentum patellte, 701 obturator internus, 659 popliteus, 679 Sartorius, 627 semi-membranosus, 670 subscapularis, 384 teres major, 383 triceps, 386 tuberosity of ischium, 507 Crccum, 453 meso-Cfficum, 463 Calamus scriptorius, 772 Canal, crural, 623 femoral, 623 of Huguier, 824 Hunter, 637 inguinal, 438 of Niick, 505 Petit, 814 Schlemm, 799 Stilling, 813 Wirsung, 584 Canaliculus, 30, 33 Canalis reuniens, 833 spiralis modioli, 828 CER Canals, semicircular, 8 Canthi, 30 Capsule, Glisson's, 579 of Tenon, 51, 62, 794 Capsules, supra-renal, 595 Caput gallinaginis, 552 Cardiac nerves, of pneumogastric, 148 r 187 sympathetic, 151 plexus, deep, 196 superficial, 195 Carotid artery, common, 81, 179 ligature of, 82 difference of left, 83 external, 95 branches of, 96 internal, 144, 270, 717 curves of, 23 plexus, 23, 151 triangles, 76, 77 Carpal arteries, 397 Carpus, bursal sac of, 364 Cartilages, arytenoid, 242 cornicula laryngis, 242 cricoid, 241 cuneiform, 242 epiglottis, 242 of larynx, 240 of nose, 271 of pinna, 816 of trachea, 267 of Wrisberg, 242 tarsal, 32 thyroid, 240 Cartilago triticea, 240 Caruncula lachrymalis, 30 Carunculse myrtiformes, 523 Cava, vena, inferior, 486 superior, 173 Cavernous plexus, 23, 152 sinus, 14, 21 structures passing through, 21 Centrum ovale majus, 754 minus, 753 Cephalic vein, 311, 327 Cerebelli, falx, 9 tentorium, 9 Cerebellum, 774 inferior peduncles of, 772 middle peduncles of, 777 superior peduncles of, 770 structure of, 777 inferior vermiform process, 776 superior vermiform process, 775 INDEX. 855 CEB Cerebral circulation, peculiarities of, 721 Cerebri, falx, 9 Cerebro-spinal fluid, 716 of cord, 784 Cerebrum, 732 base of, 742 crura of, 745 development of, 778 hemispheres of, 733 labium of, 742 longitudinal fibres of, 774 peduncular fibres of, 774 structure of, 773 transverse fibres of, 774 ventricles of, 756, 760, 767, 771 Cervicalis ascendens artery, 120, 283 profunda, 123 superficialis, 121 Cervical fascia, 64 deep, 65, 69 glands, 88 plexus of nerves, 68 Cervicis princeps artery, 107 Cervical plexus, deep, 109 superficial, 67 Cervico-facial nerve, 46 Chambers of the eye, 812, 813 Check ligaments, 299 Chest, surface marking of, 305 Chorda tympani nerve, 141 ChordtE tendineas of ventricles, 203 vocales, 246 Willisii, 12 Choroid arteries, 719, 720 coat of eye, 800 plexus, 765 Chyli receptaculum, 184 Cilia, 31 Ciliary arteries, anterior, 58 long, 58 short, 58 muscle, 802 nerves, long, 56 processes, 801 Circular sinus, 14 Circulation, foetal, 213 Circulus major and minor, 804 Circumflex artery, anterior, 319 t posterior, 318, 381 nerve, 322, 381 Circumflex, external, 639 iliac artery, deep, 438 superficial, 611 internal, 639 COR Clitoris, 521 erector of, 521 glans of, 522 prepuce of, 522 Coccygeal gland, 486 Coccygeus, 538 Cochlea, 826 canal of, 828 columella of, 827 modiolus, 827 spiral canal, 827 Collateral circulation after ligature of axillary artery, 319 carotid, 83 iliac, external, 493 common, 491 innominate, 179 femoral, common, 641 superficial, 641 subclavian, 123 Colon, ascending, 454 descending, 454 transverse, 454 Columns of Bertini, 590 Columns, carneas, 202 rugarum, 564 Complexus, 285 Communicantes noni nerves, 110 Commissure, anterior, 767 great transverse, 754 middle, 767 of cord, 787 of labium, 521 optic, 749 posterior, 768 simplex, 776 Coni vasculosi testis, 844 Concha of ear, 806 Conjunctiva, 30, 793 Constrictors of pharynx, 228 Conus arteriosus, 202 medullaris, 786 Convolutions, dentate, 742 frontal, 737 occipital, 739 parietal, 738 temporo-sphenoidal, 740 uncinate or hippocampal, 742 Cord, spermatic, 439, 845 Cornea, 796 Cornicula laryngis, 242 Coronary arteries of heart, 207 inferior, 40 superior, 40 plexuses, 196 856 INDEX. COR Coronary sinus, 201, 208 Corpora albicantia, 745 quadrigemina, 769 Corpus, Arantii, 204 callosum, 754 ventricle of, 754 cavernosum penis, 559 dentatum cerebelli, 778 fimbriatum, 762 geniculatum, 766 Highmorianum, 842 luteum of ovary, 574 spongiosum, 561 striatum, 762 Corti, organ of, 830 rods of, 830 tunnel of, 830 Costo-coracoid membrane, 309 Cotunnii liquor, 832 Cotunnius, nerve of, 262 Cotyloid ligament, 699 Cowper's glands, 517 structure of, 555 Cranial nerves, dissection to expose, 16 exit of, 16 origin of, 746 Cremaster muscle, 429 Cribriform fascia, 618 Cricoid cartilage, 241 ligaments of, 241 Crista, acustica, 833 vestibuli, 825 Crucial anastomosis, 639 ligaments, 703 Crural arch, 619 deep, 622 canal, 623 nerve, anterior, 498, 641 Crusta of crus cerebri, 748 Crystalline lens, 814 Cuneiform cartilages, 242 Cuneus, 741 Cupola of cochlea, 827 Cuvier, duct of, 170 Cystic duct, 470 Dartos scroti, 838 Deglutition, mechanism of, 237 Deiters, cells of, 832 Deltoid muscle, 379 parts covered by, 380 Demours, membrane of, 799 CIS Dental artery, inferior, 135 superior, 136 nerve, inferior, 140 Descemet, membrane of, 799 Descent of testis, 846 Diaphragm, 477 arteries of, 480 central tendon of, 479 crura of, 478 functions of, 480 nerves of, 480 openings in, 479 Digastric muscle, 92 triangle and contents, 91 Diogenes, cup of, 354 Dissection of the : abdomen, 419 abdominal viscera, 575 axilla, 312 back, 278 muscles of, connected with arm, 366 brain, 715 to remove, 12 cavernous sinus, 21 cranial cavity, 8 digastric triangle, 91 epicranial region, 1 eye, 792 extremity, lower, 609 upper, 305 face, 24 femoral hernia, 619 foot, sole of, 683 forearm, back, 387 front, 339 gluteal region, 653 hand, 353 hearing, organ of, 816 heart, 198 inguinal hernia, 440 larynx, 238 leg, back of, 672 front of, 643 mammary gland, 836 maxillary nerve, superior, 258 neck, 63 nose, 271 orbit, 49 pelvis, side view of, 525 viscera of, 499 female, 562 perineum, male, 505 female, 521 pharynx, 224 INDEX. 857 DIS Dissection (continued) of the : pterygoid region, 131 scrotum, 838 shoulder muscles, 378 spinal cord, 780 submaxillary triangle, 91 supra-clavicular region, 75 temporal region, 127 testis, 838 thorax, 155 tongue, 253 Dorsal nerves, 192 Douglas, semilunar fold of, 429 pouch of, 460 Ducts, or duct, of - Bartholin, 104 biliary, 581 common bile, 470 hepatic, 581 Cowper's gland, 517 Cuvier, 170 cystic, 470, 583 galactophorous, 837 hepatic, 470 nasal, 275 pancreatic, 476, 585 parotid gland, 43 . prostate, 552 Eivinus, 104 Stenson's, 43 sublingual gland, 104 thoracic, 184 Wharton's, 140 Wirsung, 583 Ductus arteriosus, 195 communis choledochus, 470, 583 ejaculatorius, 535 venosus, fissure of, 576 Duodenum, course of, 450 relations of, 474 Dura mater, 8 nerves of, 9 processes of, 9 sinuses of, 10 spinal cord, 782 Duverney's glands, 523 Ear, 816 muscles, 3 intrinsic, 817 Eighth pair of nerves, 19, 146, 751 Ejaculatory ducts, 535 Elbow-joint, 408 synovial membrane of, 409 FAS Elbow-joint (continued) triangle, 342 veins in front of, 327 Eleventh nerve, 20, 149, 752 Eminence, hypothenar, 353 thenar, 353 Eminentia cinerea, 773 collaterals, 765 Endocardium, 210 Endolymph of labyrinth, 825, 834 Ependyma ventriculorum, 756 Epicardium, 210 Epicranial aponeurosis, 2 Epididymis, 839 Epiglottis, 242 cushion of, 245 ligaments of, 248 mucous folds of, 243 Eustachian tube, 236, 820 valve, 201 Eye, 797 lashes, 31 lids, 30 Exit of the cranial nerves, 16 Face, dissection of, 24 motor nerves of, 25 sensory nerves of, 23, 47 Facial artery, 38, 98 nerve, 19, 69, 267, 750 on face, 44 transverse artery, 41 vein, 40, 94 Fallopian tubes, 571 fimbriffi of, 572 Fallopii aquasductus, 45 Falx cerebelli, 9 cerebri, 9 Fascia, anal, 528 arm, 328 forearm, 341 back of forearm, 388 axillary, 312 buccal, 37 bucco-pharyngeal, 38 cervical, deep, 69 costo-coracoid, 309 cremasteric, 429 cribriform, 618 iliac, 487 infundibuliform, 436 intercolumnar, 427 intermuscular of arm, 329 853 INDEX. FAS Fascia (continued) ischio-rectal, 528 lata of thigh, 615 lumbar, 279 metacarpus, 389 muscular of arm, 328 obturator, 528 orbit, 51 palmar, 354 pelvic, 527 perineal, deep, 515 superficial, 509 pharyngeal, 226 plantar, 684 prevertebral, 70 psoas, 487 recto-vesical, 529 semilunar of biceps, 330 spermatic, 427 temporal, 130 transversalis, 435 Fasciculi graciles, 726 teretes, 773 Faucium isthmus, 232 Femoral artery, 630 in canal, 637 sheath of, 621 ring, 623 Fenestra ovalis, 820 rotunda, 820 Ferrein, pyramids of, 591 Fibro-cartilages, interarticular, lower jaw, 303 scapulo-clavicular, 404 semilunar of knee, 703 sterno-clavicular, 402 wrist, 411 Fifth cranial nerve, 18, 137, 258, 749 Filum terminale, 785 Fimbriae of Fallopian tube, 572 Fissures, Bichat, 762 calcarine of brain, 740 calloso-marginal of brain, 740 horizontal, 775 longitudinal, 753 palpebral, 30 parieto-occipital, 737 praecentral, 734 primary of brain, 734 Eolando, 736 Santorini, 817 sphenoidal, nerves in, 21 Sylvius, 734 triradiate, 738 Flocculus, 776 GAN Foetal circulation, 213 changes at birth, 215 Folds, ary-epiglottic, 244 glosso-epiglottic, 244, 254 Houston's, 606 hepato-renal, 459 rectal, 606 Follicles, Graafian, 574 Fontana, spaces of, 799 Foot, cutaneous nerve of sole, 684 Forearm, cutaneous nerves of, 340 back of, 388 deep fascia of, 341 fascia on back of, 388 Foramen chordae anterius, 824 posterius, 824 caecum of medulla, 723 Magendie, 716, 771 Monro, 761 ovale of heart, 200 quadratum, 480 Thebesius, 202 Winslow, 462 Fornix, 761 conjunctive, 30, 793 crura of, 761 Fossa, ischio-rectal, 507 Mohrenheim's, 64 navicularis of labia, 521 of urethra, 557 ovalis, 200 scaphoidea of ear, 816 Fourchette, 521 Fourth cranial nerve, 17, 53, 749 ventricle, 772 Fovea centralis of eye, 806 hemi-elliptica, 825 hemispherica, 825 inferior, 773 superior, 773 Frsenuluin, 770 labiorum, 521 Frontal artery, 4, 59 nerve, 52 Galactophorous ducts, 837 Galen, veins of, 14, 765 Gall-bladder, 582 duct of, 583 fissure for, 576 relations of, 455 structure of, 583 Ganglion of Andersch, 144 INDEX. 859 GAN Ganglion (continued) Arnold, 146, 263 Bochdalek, 260 cardiac, 196 cervical inferior, 154 middle, 153 superior, 151 diaphragmatic, 480 Gasserian, 18 geniculate of facial, 268 impar, 150, 547 jugular, 144, 265 lenticular, 59 Meckel's, 260 ophthalmic, 59 otic, 263 petrous, 144, 265 pneumogastric, root of, 146, 267 trunk, 267 semilunar, 477 spheno-palatine, 260 spirale, 828 submaxillary, 105 Wrisberg, 196 Gasserian ganglion, 18 Gastrocnemius, 674 Genito-crural nerve, 497 Gimbernat's ligament, 427, 619 Giraldes, organ of, 844 Glands, agminate, 603 anal, 506 Bartholin, 523 Brunner's, 603 buccal, 38 coccygeal, 486 Cowper's, 517 Duverney's, 523 Havers', 699 lachrymal, 53 Lieberkiihn, 603 lingual, 256 Littre, 537 . Luschka, 486 Meibomian, 33 molar, 38 parotid, 41 pineal, 769 pituitary, 744 prostate, 536 sublingual, 104 submaxillary, 94 thyroid, 85 tracheal, 218 Tyson, 558 uterine, 571 IIEA Glands, lymphatic axillary, 314 bronchial, 195 elbow, at, 328 femoral, 611 inguinal, 422, 611 intercostal, 193 lumbar, 481 mediastinal, anterior, 160 neck, deep, 89 superficial, 67 popliteal, 668 submaxillary, 99 Glandula socia parotidis, 43 Glandule concatenatas, 89 Pacchionii, 10 Glans clitoridis, 522 penis, 561 Glisson's capsule, 579 Globus major, 840 minor, 840 Glosso-epiglottic folds, 244 Glosso-pharyngeal nerve, 143, 265, 752 Glottidis rima, 245 Glottis, 245 muscles acting on, 250 Gluteal region, 654 Gluteus maximus, parts seen under, 655 nerve, inferior, 662 superior, 546, 657 Graafian follicles, 574 Groin, dissection of, 610 Gubernaculum testis, 846 Gyri operti, 742 Gyrus fornicatus, 741 Hamstring muscles, 671 Hamulus of cochlea, 828 Hand, dissection of palm, 353 surface marking, 353 Hasner, valve of, 275 Havers, gland of, 699 Heart auricle, left, 205 right, 199 cavities, thickness of, 212 chordae tendineas, 203 endocardium, 200 fibrous rings of, 209 lymphatics of, 208 muscular fibres of, 211 musculi papillares, 203 nerves of, 195 openings, size of, 207 860 INDEX. HBA Heart (continued) position of, 167, 198 valves of, 203 veins of, 208 ventricles, left, 206 right, 202 weight of, 198 Helicotrema, 827 Helix, 816 Henle, looped tubes of, in kidney, 592 Hepatic artery, 467 duct, 470 Hernia, congenital, 444 encysted, 445 femoral, 619 coverings of, 624 seat of stricture, 625 funicular, 445 infantile, 445 inguinal, anatomy of, 440 changes in old, 446 direct, 443 oblique, 442 position of cord in, 446 seat of stricture, 446 tunica vaginalis, 445 lumbar, 447 of ovary, 521 umbilical, 446 ventral, 447 Herophili, torcular, 15, 721 Hesselbach's triangle, 443 Hey's ligament, 618 Highmorianum, corpus, 842 Hilton's muscle, 251 Hip-joint, movements at, 700 Hippocampus, major, 764 minor, 764 Houston, valves of, 606 Huguier, canal of, 824 Humour, aqueous, 812 vitreous, 813 Hunter's canal, 637 Hyaloid membrane, 813 Hydatids of Morgagni, 840 Hymen, 522 varieties of, 522 Hypogastric plexus, 495 Hypoglossi ansa, 85, 110 Hypoglossal nerve, 20, 103, 150, 753 HyoideS os, 239 basi-hyal, 239 cerato-hyals, 239 ligaments of, 239 thyro-hyals, 239 IRI Ileo-csecal valve, 605 artery, 472 Ileum, course of, 450 Iliac artery common, 490 external, 492 internal, 539 ligature of, 493 fascia, 487 veins, 543 Iliacus, 489 Ilio-costalis, 282 lumbar artery, 539 tibial band, 615 Impressio colica, 577 renalis, 577 Incisura cerebelli anterior, 776 posterior, 776 Incus, 822 Infra-clavicular triangle, 309 Infundibuliform fascia, 436 Infundibulum of brain, 774 cochlea, 827 heart, 202 Inguinal region, 438 glands, 611 hernia, 440 nerves, 423 Infra-orbital artery, 48, 136 nerve, 47 Innominate artery, 178 veins, 172 Interarticular nbro-cartilages (See Fibro-cartilages) Intercarotic ganglion, 486 Intercolumnar fascia, 427 Intercostal arteries, 190 anterior, 159 collateral, 191 dorsal, 191 superior, 122 glands, 193 muscles, 189 nerves, 192 Intercosto-humeral nerves, 325 Internal ear, 824 Interpleural space, 162 Intervertebral fibre-cartilages, 296 Intestine, large, course of, 450 relations of, 453 structure of, 604 small, course of, 450 structure of, 601 Intumescentia gangliformis, 268 Iris, 802 IXDEX. 861 IRI Iris (continued) arteries of, 804 nerves of, 805 structure of, 803 Ischio-rectal fascia, 528 fossa, 507 boundaries of, 520 Iter a tertio ad quartum ventriculum, 771 ad infundibulum 768 Jacob's membrane, 810 Jacobson, nerve of, 266 Jaw, lower ligaments of, 142 Jejunum, course of, 450 Joints (See Articulations) Jugular ganglion, 265 vein, anterior, 67 external, 66 internal, 84 posterior external, 67 Kerkring, valves of, 601 Kidneys, 589 arteries of, 484, 593 capsule of, 589 cortical structure of, 589 lymphatics of, 595 medullary structure of, 590 nerves of, 593 pyramids of, 590 situation of, 457 tubuli uriniferi, 592 veins of, 484, 595 Knee-joint, arteries of, 677 ligaments of, 701 movements of 705 nerves of, 653 Labia majora, 521 minora, 422 Labial arteries, 39 nerves, 48 Labium cerebri, 754 tympanicum, 828 vestibulare, 828 Labyrinth of ear, 824 Lachrymal gland, 54 nerve, 53 sac, 33, 274 Lacunas of urethra, 557 Lacus lachrymalis, 30 LIG Lamina, anterior, of cornea, 798 posterior of cornea, 799 cinerea, 743 cribrosa, 796 fusca, 796 spiralis, 828 ossea, 828 supra-choroidea, 800 Laminated tubercle of cerebellum, 776 Lancisi, nerves of, 755 Larynx, 238 arteries, 251 cartilages, 240 male and female, 252 mucous membrane of, 243 muscles, 247 nerves, 251 situation of, 238 upper opening of, 244 ventricle of, 247 Laryngotomy, 90 Lateral sinuses, 13 ventricles, 756 Latissimus dorsi, 322, 370 Lawrence on femoral hernia, 624 Leg, dissection of, back, 672 front, 643 Lens, crystalline, 814 capsule of, 814 structure of, 815 suspensory ligament of, 814 Lenticular ganglion 59 Lieberkuhn's glands, 603, 605 Ligamenta alaria, 705 annularia, 363 vaginalia, 363 Ligaments of : accessory of shoulder, 406 acromio-clavicular, inferior, 404 superior, 403 ankle, anterior, 707 lateral external, 708 internal, 707 annular anterior of ankle, 646 external of ankle, 646 internal of ankle, 646 carpus anterior, 358 radius, 409 posterior of wrist, 389 anterior carpal, 413 common, 295 elbow, 409 wrist, 413 arcuate, external, 478 internal, 478 862 INDEX. LIG Ligaments (continued) astragalo-scaphoid, 710 atlo-axoid, anterior, 300 posterior, 300 bladder, false, 503, 526 true, 529 Burns', 618 calcaneo-astragaloid, external, 709 interosseous, 709 posterior, 709 calcaneo-cuboid, long, 711 short, 711 internal, 711 superior, 711 carpo-metacarpal, 415 dorsal, 415 palmar, 415 interosseous, 415 carpus, 413 central of cord, 785 check, 299 ciliary of eye, 802 common, anterior vertebral, 295 posterior vertebral, 295 conoid, 404 coraco-acromial, 405 clavicular, 404 . humeral, 406 coracoid, 405 coronary of knee, 704 liver, 576 costo-clavicular, 402 sternal, 302 transverse, 301 vertebral, 300 cotyloid, 699 crico-arytenoid, 242 crico-thyroid, 241 crucial of knee, 703 cruciata, 363 cruciform, 300 deltoid of ankle, 707 elbow, anterior and posterior, 409 lateral external, 409 internal, 409 falciform o'f Burns, 618 liver, 455 sacro-sciatic, 695 femoral (Key's), 618 gastro-phrenic, 459 Gimbernat's, 427, 619 glenoid, 407 of fingers, 417 Hey's, 618 hip, 696 LIG Ligaments (contimied) hyo-epiglottic, 243 hyoid bone, 239 ilio-femoral, 697 lumbar, 693 incus, 823 interarticular of ribs, 301 intercarpal, 414 interclavicular, 401 intermetatarsal, 713 interosseous of cuneiform bones, 712 interosseous of forearm, 410 leg, 707 tarsus, 709 interspinous, 295 intertransverse, 298 jaw, 303 knee, 701 latum pulmonis, 160 long calcaneo-cuboid, 711 lumbo-sacral, 693 metacarpal, 416 metacarpo-phalangeal, 417 metatarsal, 713 metatarso-phalangeal, 714 mucosum of knee, 705 malleus, 823 nuchae, 297 oblique of radius, 410 sacro-iliac, 695 occipito-atloid, 298 occipito-axial, 299 odontoid, 299 orbicular of radius, 409 ovary, 572 palpebral, 32 palmar, 363 patella, 635 phalangeal of hand, 418 foot, 714 plantar, long, 711 posterior, common, 295 of Winslow, 670, 702 Poupart's, 426, 619 pterygo-maxillary, 36 pubic, 696 sub-pubic, 696 pubo-femoral, 697 prostatic, 529 radio-carpal, 413 ulnar, 711 rhomboid, 402 round, of hip, 698 liver, 455 radius, 410 INDEX. 863 LIG Ligaments (continued) uterus, 439, 504 sacro-coccygeal, 694 sacro-iliac anterior, 694 posterior, 695 oblique, 695 sacro-sciatic, great, 695 lesser, 696 sacro-vertebral, 693 scapulo-clavicular, 403 shoulder-joint, 405 stellate, 300 sterno-clavicular, 401 stylo-hyoid, 143 stylo-maxillary, 70, 100 subpubic, 696 subflava, 296 supraspinous, 296 suspensory of lens, 814 liver, 455 penis, 558 iarso-metatarsal, 713 tarsus, 709 temporo-maxillary, 303 teres of hip, 698 thyro-arytenoid inferior, 246 superior, 245 thyro-epiglottic, 243 thyro-hyoid, 239 tibio-fibular inferior, 707 superior, 706 transverse, of fingers, 355 hip, 690 knee, 704 metacarpal, 398 metatarsal, 713 trapezoid, 404 triangular of abdomen, 427 perineum, 515 uterus, 503 Winslow, 670, 702 wrist, 412 Zinn, 61 Ligamenta subflava, 296 Ligamentum denticulatum, 785 mucosum, 705 nuchas, 297 patellae, 701 pectinatum iridis, 799 posticum Winslowii, 702 spirale, 828 suspensorium, 300 Ligula, 772 Limbus spiralis, 828 Linea alba, 432 LUX Linea (continued) semilunaris, 429 splendens, 785 transverse of fourth ventricle, 772 rectus, 431 Lingua frasnum, 253 dorsalis artery, 106 Lingual artery, 108 glands, 256 nerve, 104 Lithotomy, parts divided in, 516 parts to be avoided in, 516 Littre, glands of, 557 Liver, situation of, 455 arteries of, 580 cells of, 581 coats of, 578 ducts of, 581 fissures of, 576 functions of, 582 ligaments of, 578 lobes of, 577 lobules of, 578 lymphatics of, 581 nerves of, 582 plexus of, 579 structure of, 578 veins of, 579 Lobule of the ear, 816 paracentral, 737 Lobulus caudatus, 578 centralis, 775 quadratus, 578 Spigelii, 577 Locus cteruleus, 773 niger, 745 perforates anticus, 744 posticus, 745 Longitudinal sinus, inferior, 14 superior, 11 Lumbar aponeurosis, 373 arteries, 485 fascia, 279 hernia, 447 plexus of nerves, 496 Lumbricales of hand, 364 foot, 687 Lungs, 219 air-cells of, 223 arteries of, 224 infundibula of, 222 lobes of, 166 lymphatics of, 224 nerves of, 224 position and form of, 166 864 INDEX. LUX Lungs (continued) root of, constituents, 197 shape of, 219 structure of, 216 veins of, 224 Lunulas of valves, 205 Luschka, gland of, 486 Lymphatics, heart, 208 kidney, 595 liver, 581 lung, 224 pancreas, 585 parotid gland, 43 scalp, 8 spleen, 588 testis, 845 uterus, 567 Lymphatic glands, cervical deep, 88 superficial, 67 Lyra of fornix, 762 Macula acustica, 833 cribrosa, 825 lutea, 806 Magendie, foramen of, 716, 771 Malleus, 822 ligaments of, 823 Malpighi, pyramids of, 590 Malpighian bodies of kidney, 594 'spleen, 587 Mammary gland, 836 arteries of, 837 lymphatics of, 837 internal artery, 122, 159 Mammilla, 836 Marginal convolution, 742 Marshall, vestigial fold of, 201 Maxillary artery, external, 38 internal, 133 nerve, inferior, 19, 137 superior, 19, 259 vein, 137 Meatus auditorius externus, 818 of the nose, 273 urinarius, female, 523 Meckel's ganglion, 260 Median artery, 350 nerve, 336 in palm, 361 vein, 340 Mediastinum, 162 anterior, 163 middle, 164 posterior, 163, 181 MES Mediastinum (continued) superior, 164 Medulla oblongata, 722 anterior pyramid, 723 fissures of, 723 lateral tracts of, 724 nuclei of, 728, 730 olivary bodies, 724 fasciculus, 727 posterior pyramids, 726 restiform bodies, 725 septum of, 729 Medulli-spinal veins, 782 Meibomian glands, 33 Meissner's plexus of nerves, 604 Membrana basilaris, 828 fusca, 796 limitans of retina, 811 nictitans, 30 pupillaris, 803 sacciformis, 412 tectoria, 832 tympani, 821 arteries of, 821 flaccida, 821 secundaria, 827 Membrane, of aqueous humour, 812 arachnoid of brain, 715 spinal cord, 783 Bruch, 801 choroid, 800 Corti, 830 costo-coracoid, 309 crico-thyroid, 241 Demours, 799 Descemet, 799 hyaloid, 813 interosseous of forearm, 410 leg, 706 Jacob's, 810 Eeissner, 829 thyro-hyoid, 239 Schneiderian, 275 Membranes of brain, 8, 715 spinal cord, 783 Membranous labyrinth, 832 semicircular canals, 832 Meningeal arteries, 16 anterior, 16 middle, 16, 134 parva, 16 posterior, 16, 107 small, 135 Mesenteric artery, inferior, 473 superior, 472 INDEX. 865 MES Mesenteric veins, inferior, 474 superior, 470 Mesentery, 462 Meso-colon, ascending, 463- descending, 463 transverse, 462 sigmoid, 463 rectum, 463, 531 Mesorchium, 848 Metencephalon, 778 Mitral valves, 206 Modiolus of cochlea, 827 Mohrenheim's fossa, 64 Molar glands, 38 Monro, foramen of, 761 Mons Veneris, 521 Monticulus cerebelli, 775 Morgagni, sinus of, 229 hydatids of, 840 Morsus diaboli, 572 Motor oculi nerve, 60, 749 Mouth, muscles of, 25 Movements of spine, 298 Miiller, fibres of, 806 Multifidus spinae, 286 Muscles ': abdominal functions of, 433 nerves of, 434 abductor hallucis, 685 indicis, 399 minimi digiti manus, 360 pedis, 685 pollicis, 358 accelerator urinre, 511 accessorius ad sacro-lumbalem, 283 flexor, 686 adductor brevis femoris, 631 hallucis, 690 longus, 629 magnus, 632 pollicis, 359 anconeus, 393 antitragicus, 817 aryteno-epiglottideus, 249 inferior, 251 superior, 251 arytenoideus, 249 attollens aurem, 3 attrahens aurem, 3 azygos uvulae, 235 back of, 278 biceps of arm, 329 thigh, 669 bi venter cervicis, 285 MUS Muscles (continued) brachialis antieus, 331 buccinator, 36 cervicalis ascendens, 283 ciliary, 802 coccygeus, 538 eoehlearis, 828 eomplexus, 285 compressor naris, 34 sacculi laryngis, 251 urethrffi, 517 in the female, 524 coraeo-brachialis, 331 corrugator supercilii, 30 eremaster, 429 crico-arytenoideus lateralis, 249 posticus, 248 crico-thyroideus, 247 crureus, 634 dartos, 838 deltoid, 379 depressor alee nasi, 35 anguli oris, 27 labii inferioris, 27 diaphragm, 477 digastricus, 92 dilatator naris anterior, 35 posterior, 35 ejaculator urinae, 511 erector clitoridis, 521 penis, 512 spins, 281 external sphincter ani, 508 extensor brevis digitorum, 650 carpi radialis brevior, 390 longior, 390 carpi ulnaris, 392 communis digitorum, 391 indicis, 394 longus digitorum pedis, 647 minimi digiti, 392 ossis met. pollicis, 393 primi internodii pollicis, 394 secundi internodii pollicis, 394 proprius hallucis, 649 flexor accessorius, 686 brevis digitorum, 685 hallucis, 690 minimi digiti manus, 360 pedis, 691 pollicis, 359 carpi radialis, 342 ulnaris, 344 longus digitorum pedis, 669 pollicis, 351 3K 866 INDEX. MUS Muscles (continued) profundus digitorum, 351 proprius hallucis, 679 sublimis digitorum, 344 gastrocnemius, 674 gemellus inferior, 659 superior, 659 genio-hyoglossus, 102 hyoideus, 101 gluteus maximus, 655 medius, 656 minimus, 657 gracilis, 629 helicis major, 817 minor, 817 hyoglossus, 101 iliacus, 489 ilio-costalis, 282 indicator, 394 inferior constrictor of pharynx, 228 infra-spinatus, 382 intercostal, external, 189 internal, 190 interosseous of foot, 692 of hand, 399 interspinales, 287 intertransversales, 287 ischio-cavernosus, 512 kerato-cricoid, 248 latissimus dorsi, 322, 370 laxator tympani, 823 levator anguli oris, 36 scapulae, 374 ani, 538 female, 563 labii inferioris, 27 superioris alaeque nasi, 35 proprius, 35 menti, 27 palati, 234 palpebrse, 32, 54 prostatse, 538 levatores costarum, 287 lingualis, inferior, 257 superficial, 257 longissimus dorsi, 283 longus colli, 293 lumbricales manus, 364 pedis, 687 masseter, 129 of mastication, 129 middle constrictor of pharynx, 228 mouth, 25 multindus spiase, 286 MUS Muscles (continued) mylo-hyoideus, 99 nose, of the, 34 obliquus auris, 818 externus abdoniinis, 425 inferior oculi, 62 capitis, 289 internus abdominis, 428 superior oculi, 55 capitis, 289 obturator externus, 660 internus, 658 occipito-frontalis, 2 opponens digiti manus, 360 pollicis, 359 orbicularis oris, 25 palpebrarum, 28 omo-hyoid, 79, 375 palato-glossus, 235 pharyngeus, 235 palmaris brevis, 354 longus, 344 pectineus, 629 pectoralis major, 308 minor, 314 peroneus brevis, 652 longus, 651, 693 tertius, 648 plantaris, 674 platysnia myoides, 64 popliteus, 678 prevertebral, 293 pronator quadratus, 352 radii teres, 342 psoas magnus, 488 parvus, 489 pterygoideus externus, 131 internus, 132 pyramidalis, 432 nasi, 34 pyriformis, 658 quadratus femoris, 659 lumborum, 490 menti, 27 quadriceps femoris, 633 recti of the eye, 61 rectus abdominis, 431 capitis anticus major, 294 minor, 294 lateralis, 289 posticus major, 288 minor, 289 externus oculi, 61 femoris, 633 internus oculi, 61 INDEX. 8G7 MUS Muscles (continued) rectus inferior oculi, 61 sternalis, 307 superior oculi, 55 retrahens aurem, 3 rhomboideus major, 374 minor, 374 risorius, 25 rotatores spins, 286 sacro-lumbalis, 282 sartorius, 626 scalenus anticus, 111 medius, 111 posticus, 111 serni-mernbranosus, 670 semi-spinalis colli, 286 dorsi, 285 semi-tendinosus, 669 serratus magnus, 323, 377 posticus inferior, 278 superior, 278 soleus, 675 sphincter ani internus, 531 iridis, 804 vaginae, 525 vesicle, 548 spinalis dorsi, 284 splenius capitis, 281 colli, 281 stapedius, 823 sterno-cleido mastoideus, 71 hyoid, 77 thyroid, 77 stylo-glossus, 103, 142 hyoideus, 93 pharyngeus, 142 subanconeus, 386 subclavius, 310 subcostal, 190 subcrureus, 635 sublimis digitorum, 344 subscapularis, 323, 383 superior constrictor of pharynx, 228 supinator radii brevis, 395 longus, 345 supra-spinales, 287 supra-spinatus, 383 temporal, 130 tensor fascias femoris, 632 palati, 234 tarsi, 34 tympani, 823 teres major, 323, 382 minor, 382 NER Muscles (continued) thyro-arytenoideus, 250 epiglottideus, 251 hyoid, 79 tibialis anticus, 647 posticus, 680, 693 trachelo-mastoid, 283 tragicus of ear, 817 transversalis abdominis, 430 colli, 283 pedis, 692 transverso-spinalis, 285 transversus anriculaa, 818 perinei, 512 deep, 513 trapezius, 368 triangularis sterni, 158 triceps extensor cubiti, 338, 385 femoris, 634 of ureters, 551 uvulae azygos, 235 vastus externus, 634 internus, 634 zygomaticus major, 28 minor, 28 Musculi papillares, 203, 207 pectinati, 200 Musculo-spiral nerve, 338 Mylo-hyoid artery, 135 nerve, 99, 140 Nabothi ovula, 569 Nasal fossae, posterior openings, 232 duct, 275 muscles, 34 Naso-lobular nerve, 35, 56 Nates of brain, 770 Neck, central line of, 89 cutaneous nerves of, 67 dissection of, 63 lymphatics of, 67 surface marking of, 64 triangles of, 72 anterior, 76 carotid inferior, 76 superior, 77 digastric, 91 posterior, 76 submaxillary, 91 supra-clavicular, 75 Nerves : abducens oculi, 60, 750 accessory obturator, 643 acromial, 69, 307 868 INDEX. NER Nerves (continued) anterior crural, 498, 641 cutaneous of abdomen, 423 tibial, 653 Arnold's, 147 auditory, 751, 834 auriculo-parotidean, 68 temporal, 6, 128, 139 auricular branch of pneumogastric, 147 posterior, 6, 108 axillary, plexus of, 320 back, cutaneous of, 289 Bell, nerve of, 126, 324 brachial plexus, 124, 320 buccal branch of facial, 47 inferior maxillary, 138 calcaneo-plantar, 682 cardiac branch of pneumogastric, 148, 187 inferior, 154 middle, 154 superior, 153 carotid of glosso-pharyngeal, 263 spheno-palatine ganglion, 263 cervical, acromial branch of, 69, 307 posterior branches of, 367 superficial, 68 plexus, deep, 109 cervico-facial, 46 chorda-tympani, 141, 269, 824 ciliary, long, 56 short, 60 circumflex, 322, 381 clavicular, 69, 307 cochlear, 834 coccygeal, 544 posterior branch of, 368 communicans noni, 84, 110 communicans peronei, 653, 666 cornea, nerves of, 799 coronary anterior, 196 posterior, 196 cranial, exit of, 16 at base of skull, 265 origin of, 746 crural branch of genito-crural, 615 cutaneous of chest, 306 forearm, 340 neck, 67 thigh, 614, 668 external, 614 internal, 614 middle, 614 NER Nerves (continued) dental, anterior, 260 inferior, 140 posterior, 259 descendens noni, 84 dorsal, 192, 367 penis, 520 twelfth cranial, 423, 434, 753 dura mater, 9 eighth cranial, 19 origin of, 751 eleventh cranial, 20, 149, 752 external cutaneous, of musculo- spiral, 385 of peroneal, 645 of thigh, 498, 614 laryngeal, 98 plantar, 689 popliteal, 652 respiratory, of Bell, 126, 324 saphenous, 667, 673 superficial petrosal, 24, 269 facial, 6, 44 cervical branch of, 69 in skull, 267 origin of, 750 fifth cranial, 18 origin of, 749 sacral, 544 first cranial, 277, 747 origin of, 747 lumbar, 496 fourth cranial, 17, 53 pair, origin of, 749 sacral, 544 frontal, 5, 52 genital branch of genito - crural, 497, 615 genito-crural, 497 crural branch of, 497, 615 glosso-pharyngeal, 143, 265 carotid branches of, 144 lingual branches of, 144 origin of, 752 pharyngeal branches of, 144 tonsillar, 114 gluteal, inferior, 546, 657, 662 superficial, 657 superior, 657 great sciatic, 661, 665, 672 occipital, 6, 290 gustatory, 104, 140 hypoglossal, 20, 103, 150 origin of, 753 ilio-hypogastric, 414, 434, 496 INDEX. 869 NER Nerves (continued) ilio-inguinal, 424, 434, 496 inguinal branch of, G15 incisor, 140 inferior dental, 140 htumorrhoidal, 520 laryngeal or recurrent, 187 .maxillary, 19, 187 pudendal, 509, 611 infra-maxillary of facial, 47 orbital of facial, 46 of superior maxillary, 47 trochlear, 56 intercostal, 192 abdominal, 193 anterior cutaneous branches, 307 intercosto-humeral, 313, 325 lateral cutaneous of, 307 pectoral, 193 internal cutaneous, of arm, 325 thigh, 614 plantar, G89 popliteal, 666 branches of, 667 interosseous anterior, 353 posterior, 396 iris, 805 Jacobson's or tympanic, 266 labial, 48 lachrymal, 53 Lancisi, 755 kidney, 595 laryngoal, external, 98, 148 inferior, 148, 186, 252 inferior or recurrent, 148, 187 internal, 98, 148 recurrent, 148, 187 superior, 98, 148, 251 lateral cutaneous of abdomen, 423 lesser cutaneous of arm, 326 lingual, 104, 140 of glosso-pharyngeal, 144 long or inferior pudendal, 509 long saphenous, 642 liver, 582 lumbar, plexus of, 496 posterior branches of, 368 sympathetic, 494 lumbo-sacral, 544 malar branch of superior maxillary, 49,63 malar of facial, 46 maxillary inferior, 137 superior, 258 NER Nerves (continued) median, 336, 350 cutaneous branch of, 351 digital branches of, 361 in the palm, 361 mental, 49, 140 masseteric, 138 motor oculi, 60 origin of, 749 musculo-cutaneous, of arm, 337 foot, 653 spiral, 338, 341 mylo-hyoid, 140 hyoidean, 99 nasal, 48, 56 septal branch of, 66 superior, 262 upper, 262 naso-lobular, 35, 49, 56 palatine, 262 neck, cutaneous of, 67 nervi molles, 40 ninth cranial, 20, 143 origin of, 752 noni communicantes, 84, 110 obturator, 498, 642 accessory, 498 internus, 545 occipital, great, 6, 290 small, 6, 68 olfactory, 17, 277 origin of, 747 ophthalmic, 19 optic, 17, 67 origin of, 748 orbital branch of superior maxillary, 49, 63 malar branch of, 49, 63 palatine, anterior, 262 external, 262 nasal branches of, 262 naso-, 262 posteiior, 262 palpebral, 48 palmar branch of median, 354 of ulnar, 354 pancreas, 585 pars intermedia, 751 perinea!, 520 peroneal, 652, 665 external cutaneous branch of, 645 pea anserinus, 46 petrosal, external, 269 great, 263 870 INDEX. NER Nerves (continued) petrosal, small superficial, 266 pharyngeal of glosso-pharyngeal, 144 of pneumogastric, 147 phrenic, 110, 112 in chest, 180 plantar, external, 688 internal, 687 pneumogastric, 20, 146, 186, 266 auricular branch of, 6 in the chest, 186 course of, 186 origin of, 752 popliteal, external, 652 internal, 666 portio dura, 44 posterior auricular, 6, 45 branches of spinal, 289 interosseous, 396 scapular, 375 tibial, 682 thoracic, 126, 324 pterygoid, 138 pudendal, inferior or long, 509 pudic, 520, 546 pulmonary branches of pneumo- gastric, 187 radial, 347 recurrent or inferior laryngeal, 148, 187 rhomboid, 126 sacral, 544 fourth, 508 plexus, branches of, 545 posterior branches of, 368 saphenous, long, 642, 645 scalp, of, 4 second cranial, 17, 57 origin of, 748 cervical, 271 seventh cranial, 6, 44, 267 origin of, 750 shoulder, cutaneous of, 379 sixth cranial, 19, 60 origin of, 750 small occipital, 6, 68 sciatic, 546, 662 superficial petrosal, 23 in sphenoidal fissure, 22 spheno-ethmoidal, 58 spinal accessory, 74, 140, 373 origin of, 752 spinal, posterior branches of, 367 splanchnic, great, 189 NOS Nerves (continued) splanchnic, lesser, 189 smallest, 189 spleen, 588 sternal, 68, 307 subclavius, 125 suboccipital, 271 cutaneous branch of, 7 subscapular, 321 superior gluteal, 546, 657 maxillary, 19, 258 supra-clavicular, 68, 306 maxillary branch of facial, 47 orbital, 5, 47, 53 scapular, 126, 376 trochlear, 5, 47, 52 sympathetic, abdomen, 494 cervical, 150 in the chest, 188 in the pelvis, 546 temporal branch of superior max- illary, 6, 63 deep anterior, 138 posterior, 138 branches of facial, 6, 45 temporo-facial, 6, 45 malar, 6, 63 tenth cranial nerve, 20, 146, 186, 266 origin of, 752 testis, 845 third cranial nerve, 17, 60 origin of, 749 thoracic anterior, 311 posterior, 126, 324 tonsillar of glosso-pharyngeal, 144 trifacial, 47, 138, 258 trigeminal, origin of, 749 trochlear, of orbit, 52, 56 tympanic, 266, 269 twelfth cranial, 20, 103, 150 origin of, 753 ulnar, 337, 349 deep palmar branch of, 366 dorsal, cutaneous of, 350 in the palm, 357 deep, 366 uterus, 567 vestibular, 834 Vidian, 263 Wrisberg, 313, 326 Nervi molles, 40 Nodule of cerebellum, 776 Nose, arteries of, 40, 273, 276 cartilages of, 271 INDEX. 871 NOS Nose (continued) dissection of, 271 interior of, 273 meatus of, 273 mucous membrane of, 275 muscles of, 34 nerves of, 273, 277 septum of, 272 veins of, 276 Niick, canal of, 505 Nymphse, 522 Obex, 772 Obturator artery, 541, 643 abnormal, 541 externus, 660 fascia, 528 internus, 658 nerve, 498, 642 accessory, 498, 643 Obliquus externus, 425 inferior, 62, 289 internus, 428 superior, 55, 289 Occipital artery, 4, 107 sinus, 15 nerve, great, 6, 290 small, 6, 68 vein, 4, 108 Occipito-atloid ligaments, 298 axial ligaments, 299 frontalis, 2 Odontoid ligaments, 299 Oculi tendo, 28 tutamina, 30 CEsophageal arteries, 194 plexus, 187 (Esophagus, 185 structure of, 186 Olfactory bulb, 17 origin of, 747 nerves, 277 Omentum, gastro-colic, 463 hepatic, 464 splenic, 464 great, 463 cavity of, 460 lesser, 464 , Openings for aorta in diaphragm, 479 cava, vena, in diaphragm, 480 cesophageal in diaphragm, 479 of heart, 207 upper, of thorax, 157 Operculum, 735 PAN Ophthalmic artery, 57 ganglion, 59 nerve, 19 veins, 59 Optic nerve, 17, 57, 748 Ora serrata, 805 structure of, 812 Orbit, dissection of, 49 contents of, 51 fascia of, 51 nerves at back of, 22 periosteum of, 50 Organ of Corti, 830 Giraldes, 844 Kosenmuller, 575 Ossicula auditus, 821 ligaments of, 823 Ostium abdominale, 572 externmm of uterus, 568 internum of uterus, 568 internum of Fallopian tube, 571 Otic ganglion, 263 branches of, 265 Otoliths, 833 Ovaries, 572 arteries of, 485 position of, 573 structure of, 573 Oviducts, 571 Ovula of Naboth, 569 Ovum, 574 Pacchionian bodies, 10 Palate, glands of, 237 hard, 237 pillars of, 233 soft, 232 muscles of, 234 Palati circumflexus, 234 levator, 234 tensor, 234 velum pendulum, 232 Palatine artery, ascending, 98 descending, 136 Palmar arch, deep, 365 superficial, 355 profunda artery, 365 Palpebra, 30 cartilages of, 32 conjunctiva of, 30 Pampiniform plexus, 845 Pancreas, 584 duct of, 585 872 INDEX. PAN Pancreas (continued) functions of, 585 lesser, 584 lymphatics of, 585 position of, 457 relations of, 475 structure of, 585 vessels of, 585 Papilla lachrymalis, 30 Papillas circumvallatas, 254 filiformes, 255 fungiformes, 255 Parepididymis, 844 JParotid gland, 41 dnct, 43 relations of, 42 structure of, 44 structures in, 42 Parotidis glandula socia, 43 Parovarium, 575 Pars ciliaris retime, 806 Pecquet, cistern of, 184 Pectiniforme, septum, 559 Pedis dorsal artery, 650 Pelvic fascia,. 527 female viscera, 562 male viscera, 529 Pelvis, contents of female, 503 male, 500 side view of female, 499 male, 525 Penis, 558 bulb of, 561 artery of, 519 cervix of, 558 corona glandis, 558 corpus eavernosum, 559 artery of, 519 spongiosum, 561 eras, 559 dorsal artery of, 519 erector, 512 glans, 561 glanclulse Tysonii, 558 helicine arteries of, 561 lymphatics of, 562 nerves of, 520, 562 vessels of, 562 Perforating arteries of thigh, 640 Pericardium, 168 objects seen on opening, 170 structure of, 169 vestigial fold of, 170 Perilymph, 832 Perineum, female, 521 PLA Perineum (continued) male, 505 boundaries of, 505 cutaneous nerves of, 508 raphe of, 506 tendinous centre of, 509 triangular ligament of, 515 parts between, 516 surgery of, 515 Permeal arteries, superficial, 510 fascia, deep, 515 superficial, 509 transverse muscle, 512 deep muscle, 513 Peritoneum, 458 course of, 458 lesser cavity of, 460 parts covered by, 460 partially by, 460 jmcovered by, 460 Peroneal artery, 681 anterior, 682 nerve, 652, 665 Pes anserinus, 45 Petit, canal of, 814 Petrosal ganglion, 265- nerve lesser, 23, 263 superficial external, 24 small, 266 great, 23, 263 sinuses, inferior, 14 superior, 14 Peyer's glands, 603 Pharyngeal aponeurosis, 226, 230 artery, ascending, 109, 145 fascia, 226 veins, 109 venous plexus, 227 Pharynx, 224 constrictors of, 228 mucous membrane of, 231 openings into, 230 Phrenic nerve, 110, 112 in chest, 180 differences of, 180 Pia mater of brain, 717 spinal cord, 784 Pineal body, 769 peduncles of, 769 Pinna of ear, 816 ligaments of, 817 structure of, 816 muscles of, 817 Pituitary body, 744 Plantar artery, external, 688 INDEX. 873 PLA Plantar artery, internal, 687 nerve, external, 689 internal, 689 fascia, 684 Plantaris, 674 Platysma myoides, 64 Plexus of nerves, Auerbach's, 604 brachial, 124 cardiac, deep, 196 superficial, 195 carotid, 23, 151 cavernous, 23, 152 cervical, superficial, 68 deep, 110 coeliac, 495 coronary, anterior, 196 posterior, 196 diaphragmatic, 494 gastric, 495 guise, 186 hffimorrhoidal, 547 hepatic, 495 hypogastric, 495 lumbar, 496 Meissner's, 604 mesenteric, 604 inferior, 495 superior, 495 cesophageal, 187 ovarian, 495 patellar, 645 pelvic, 546 prostatic, 547 renal, 495 sacral, 544 spermatic, 495 splenic, 495 superficial cardiac, 195 supra-renal, 495 sympathetic of abdomen, 494 uterine, 547 vesical, 547 of veins, interlobular, 579 pampiniform, 845 pterygoid, 137 vaginal, 563 vesico-prostatic, 529 Pleura, 160 outlines of, 165 cavity of, 160 Plica semilunaris, 30 Pneumogastric nerve, 20, 146, 266, 752 in chest, 186 ganglia of, 267 auricular branch of, 6 PYR Pomum Adami, 240 Pons hepatis, 576 Tarini, 745 Varolii, 731 Popliteal artery, 667, 676 nerve, external, 652 internal, 666 space, 664 vein, 668, 678 Popliteus, 678 Porus opticus, 796, 806 Portal fissure, 576 Portio dura, 44, 750 mollis, 751 Pouch of Douglas, 505 recto -vaginal, 505 vesical, 501 Pouches, laryngeal, 247 Poupart's ligament, 426, 619 Precordial region, 167 Prepuce, 558 Prevertebral muscles, 293 fascia, 70 Processus cochleariformis, 820 Promontory of tympanum, 820 Prosencephalon, 778 Prostate, 536 arteries of, 554 lobes of, 551 lymphatics of, 554 nerves of, 554 position of, 536 relations of, 536 sinus of, 552 structure of, 553 veins of, 554 Psoas fascia, 487 magnus, 488 parvus, 489 Pterygo-palatine artery, 136 maxillary ligament, 36 region, 131 Pudendal, inferior, nerve, 509, 511 Pudenda, 521 Pudic artery, internal, 517, 542, 663 nerve, 520, 546 Pulmonary artery, 194, 223 nerves of pneurnogastric, 187 valves, 204 Pulmonis hilum, 166 Puncta lachrymalia, 30, 33 Pupil, 803 Pylorus, 598 Pyramid, anterior, of tympanum, 821 874 INDEX. PYR Pyramid (continued) posterior, of tympanum, 820 cerebellum, 776 Quadratus lumborum, 490 Kadial artery, 346 at back of wrist, 397 in palm of hand, 365 nerve, 347 vein, 340 Ranine artery, 106 vein, 106 Ranula, 142 Eeceptaculum chyli, 184, 481 Recess, lateral of fourth ventricle, 772 Recto-vaginal pouch, 505 Recto-vesical fascia, 529 pouch, 501 Rectum, 604 ampulla of, 531 arteries of, 532 course of, 501 digital examination of, 532 folds in, 606 relations of, 531 Rectus femoris, 633 Region, precordial, 167 Regions of abdomen, 419 Reil, fillet of, 727 island of, 735 Reissner, membrane of, 830 Restiform bodies, 725 Rete testis, 842 Retina, 805 arteria centralis of, 58 cones and rods of, 810 structure of, 806 Ribs, movements of, 303 Rima glottidis, 245 Ring, abdominal external, 427 internal, 436 femoral, 623 fibrous of heart, 209 Rivini, notch of, 821 Rivinus, ducts of, 104 Rolando, arciform fibres of, 726 fissure of, 735 funiculus of, 726 tubercle of, 726 Rosenmiiller, organ of, 575 Rugae of vagina, 564 Ruyschiana tunica, 801 SEP Sac, lachrymal, 33, 274 of omentum, 463 Saccule of vestibule, 833 Sacculus laryngis, 247 Sacro-lumbalis, 282 iliac articulation, 694 Santorini, cartilages of, 242 fissures of, 817 Saphena, external vein, 673 internal vein, 613 Saphenous, external nerve, 667 opening, 617 posterior vein, 673 Scala media, 828 tympani, 828 vestibuli, 828 Scalp, dissection of, 1 arteries of, 4 lymphatics of, 8 nerves of, 4 veins of, 4 Scaleni muscles, 111 Scapula artery, dorsalis, 318 Scapular artery, posterior, 121, 376 supra, 121, 384 vein, posterior, 121 Scarpa, liquor of, 834 triangle of, 627 Schlemm, canal of, 799 Schneiderian membrane, 275 Sciatic artery, 542, 662 nerve, great, 661, 665, 672 small, 546, 662 Sclerotic coat of eye, 795 structure of, 796 Scrotum, 838 dartos of, 838 lymphatics of, 839 septum of, 838 vessels of, 839 Semicircular canals, 826 Semilunar cartilages of knee, 703 ganglia, 477 valves, 204 Semimembranosus, 670 Semispinalis colli, 826 dorsi, 825 Semitendinosus, 669 Septum, artery of nasal, 40 auricularum, 200 lucidum, 759 pectiniforme, 559 scroti, 838 tongue, 258 transversum, 833 INDEX. 875 SEP Septum (continued) ventriculorum, 202 Serratus magnus, 323, 377 posticus inferior, 278 superior, 278 Seventh cranial nerve, 19, 267, 750 Sheath, axillary vessels, 309 femoral vessels, 621 rectus muscle, 432 Sheaths for extensor, tendons of hand, 389 Sheaths for flexor tendons of hand, 362 Shoulder, cutaneous nerves of, 378 joint, 405 movements of, 407 muscles in relation with, 407 synovial membrane of, 407 Sigmoid flexure of colon, 454 Sinus circularis iridis, 799 coronary, 208 Morgagni, 229 pocularis, 552 . prostaticus, 552 Sinus venous, cavernous, 14, 21 circular, 14 coronary of heart, 201 dura mater, 10 lateral, 13 longitudinal, inferior, 14 superior, 11 occipital, 15 petrosal, inferior, 14 superior, 14 straight, 14 transverse, 15 venosus, 199 Sinuses, great, of aorta, 176 Valsalva, 176 Sixth cranial nerve, 19, 60, 750 Small intestines, 601 Socia parotidis, glandula, 43 Scemmering, foramen of, 806 Solar plexus, 494 Soleus, 675 Space, interpleural, 162 popliteal, 664 subdural, 8 Spaces of Fontana, 799 subarachnoid, 716 Spermatic cord, 439, 845 arteries of, 439, 484 lymphatics of, 439 nerves of, 439 veins of, 439 STY Sphenoidal fissure, structures passing through, 21 Spheno-palatine artery, 136 ganglion, 260 branches of, 262 Spigelii lobulus, 577 Spinse rotatores, 286 Spinal-accessory nerve, 20, 74, 149, 373, 752 Spinal cord, 786 arteries of, 791 central canal of, 789 fissures of, 787 functions of, 791 membranes of, 783 structure of, 788 Spinal lateral artery from vertebral, 120 Spinal nerves, origin of, 789 Spine, ligaments of, 295 movements of, 298 Splanchnic nerves, 189 great, 189 lesser, 189 smallest, 189 Spleen, 585 artery of, 468, 587 functions of, 588 lymphatics of, 588 Malpighian corpuscles of, 587 nerves of, 588 omenta of, 586 pulp of, 586 relations of, 456 tunics of, 586 veins of, 469, 588 Splenium of corpus callosum, 756 Splenius capitis, 281 colli, 281 Stapedius, 823 Stapes, 822 Stenson's duct, 43 Sterno-mastoid muscle, 71 artery, middle, 96 superior, 107 parts beneath, 80 Stilling, canal of, 813 Stomach, 596 relations of, 449 structure of, 599 Straight sinus, 14 Striae acusticse, 772 laterales, 755 longitudinales, 772 medullares, 772 Stylo-glossus, 103, 142 876 INDEX. STY Stylo-hyoid ligament, 143 muscle, 93 Stylo-maxillary ligament, 70, 100 Subarachnoid fluid of brain, 716 of spinal cord, 784 spaces of, 716 Subclavian artery, left, 115, 179 right, 113 ligature of, 116 vein, 123 Subdural space, 8 Sublingual artery, 106 gland, 104 Suboccipital nerve, 7, 271 triangle, 289 Submaxillary ganglion, 105 gland, 94 triangle, 91 Subperitoneal fat, 438 Subscapular artery, 317 nerves, 321 Subscapularis, 323, 383 Sulci of brain, 733 Sulcus spiralis, 828 Supercilii corrugator, 329 Supra-clavicular nerves, 68 triangle, 75 Supra-renal capsules, 595 arteries of, 596 nerves of, 596 relations of, 457 structure of, 596 Supra-orbital artery, 4, 58 nerve, 5, 47, 53 Supra-scapular artery, 121, 375 nerve, 126, 376 vein, 121 Supra-trochlear nerve, 5, 47, 52 Supra-spinales, 287 Supra-spinous ligament, 296 Sylvius, aqueduct of, 771 fissure of, 734 Sympathetic nerves : cervical, 150, 153, 154 cranial, 151 lumbar, 494 nervi molles, 40 pelvic, 546 thoracic, 188 Symphysis pubis, 696 sacro-iliac, 694 Taenia, fourth ventricle, 772 hippocampi, 762 THY Tsenia semicircularis, 764 Tarsal cartilages and ligaments, 32 Tarsi, tensor, 34 Tarsus, synovial membranes of, 712 Tectorial membrane, 832 Tegmentum, 745 Temporal artery, 127 superficial, 4 deep, 128, 135 fascia, 130 . muscle, 130 nerves, deep, 138 veins, 128 superficial, 4 Temporo-facial nerve, 45 Temporo-maxillary ligaments, 303 Tendo Achillis, 675 palpebrarum, 28 Tenon, capsule of, 51, 62, 794 Tenth cranial nerve, 20, 146, 186, 752 Tentorium cerebelli, 9 Teres major, 323, 382 minor, 382 Testes cerebri, 770 muliebres, 572 Testis, 839 arteries of, 839 coverings of, 840 descent of, 846 gubernaculum, 846 lymphatics of, 845 mediastinum, 842 nerves of, 845 structure of, 843 Thalamencephalon, 778 Thalami optici, 766 Thebesii foramina, 202 valve, 201, 208 veins of, 208 Theca vertebralis, 783 Third cranial nerve, 17, 60, 749 Thoracic aorta, 175 Thoracic artery, alar, 317 long, 317 superior, 310 nerves, anterior, 311 posterior, 126, 324 Thoracic duct, 184, 481 Thoracico-acromialis artery, 310 Thorax, base of, 157 dissection of, 155 osseous measurements, 155 upper opening of, 157 Thymus gland, 157 INDEX. 877 THY Thyro-arytenoideus, 250 Thyro-epiglottideus, 251 Thyro-hyoid, 79 Thyroid artery, superior, 96 inferior, 120 vein, 98 cartilage, 240 gland, 85 arteries of, 87 lymphatics of, 87 nerves of, 87 structure of, 87 veins of, 87 Tibial artery, anterior, 649 posterior, 681 nerve, anterior, 653 posterior, 682 Tibialis anticus, 647 posticus, 680 Tomentum cerebri, 717 Tongue, 253 arteries of, 258 foramen, cfflcum of, 253 glands beneath, 256 mucous membrane of, 253 muscular fibres of, 257 nerves of, 258 papillae of, 254 raphe of, 253 septum of, 258 Tonsillar artery, 98 Tonsils, 235 Torcular Herophili, 15 Trachea, 216 cartilages of, 217 glands of, 218 mucous membrane of, 218 muscular fibres of, 218 relations of, 216 Tragus, 816 Transversalis fascia, 435 abdominis, 430 Trapezium of pons Varolii, 732 Trapezius, 368 Triangle, carotid inferior, 76 superior, 77 digastric, 91 elbow, 342 Hesselbach's, 443 infraclavicular, 309 neck, anterior, 76 posterior, 73 occipital, 73 Scarpa's, 627 subclavian, 75 URE Triangle (continued) submaxillary, 91 suboccipital, 289 supraclavicular, 75 Triangular ligament, of abdomen, 427 perineum, 515 Triangularis sterni, 158 Triceps extensor cubiti, 338, 385 femoris, 634 Tricuspid valves, 203 Trifacial nerve, 18, 749 Trigonum vesicse, 550 Trochlea of orbit, 55 Trochlearis nerve, 17, 749 Tube, Eustachian, 236 Fallopian, 571 Tuber annulare, 731 cinereum, 744 Tubercula quadrigemina, 769 Tuberculum acusticum, 773 Tubes, bronchial, 217 Tunica albuginea, 841 Euyschiana, 801 vaginalis, 841 vasculosa, 842 Tutamina oculi, 30 Twelfth cranial nerve, 20, 103, 753 Tympani laxator, 823 membrana, 821 tensor, 823 Tympanic nerve of facial, 269 glosso-pharyngeal, 266 Tympanum, 819 arteries of, 824 Tyson's glands, 558 Ulnar artery, 348 nerve, 337, 349 in palm, 357 deep, in hand, 366 veins, 340 Umbilical hernia, 446 Umbilicus, 432 Urachus, 447 Ureter, 535 course of, 535 muscles of, 551 orifices of, 551 Urethra, female, 523 male, 555 bulbous portion of, 557 fossa navicularis of, 557 lacuna of, 557 878 INDEX. URE Urethra (continued] male, membranous part of, 537 spongy part of, 557 structure of, 557 Uterus, 565 arbor vitro of, 569 arteries of, 566 cervix of, 568 glands of, 571 lymphatics of, 567 masculinus, 552 nerves of, 567 os of, 568 position of, 503 round ligament of, 504 structure of, 567 veins of, 567 Utricle of vestibule, 833 Utriculus, 552 Uvea, 803 Uvula of bladder, 550 cerebellum, 776 palate, 233 Uvula azygos, 235 Vagina, 525, 564 arteries of, 567 bulb of, 525 structure of, 564 venous plexus of, 563 Vagus nerve, 20, 146, 186, 752 Vallecula of cerebellum, 776 Vallum of tongue, 254 Valsalva, sinuses of, 176 Valve, coronary, 201 Eustachian, 201 Hasner, 275 ileo-csecal, 606 Kerkring, 601 Thebesius, 201, 208 Vieussens, 770 Valves, cardiac, position of, 171 aortic, 207 mitral, 206 pulmonary, 204 semilunar, 204 tricuspid, 203 Valvulse conniventes, 601 Varolii pons, 731 Vas aberrans, 844 deferens, 439, 535, 844 spirale, 835 Vastus externus, 634 internus, 634 VEI Veins : angular, 41 auricular, 108 axillary, 319 azygos, left upper, 183 major, 182 minor, 183 basilic, 327 median, 327 basi-vertebral, 781 brachial, 335 brachio-cephalic, 172 bronchial, 224 capsular, 580 cardiac, anterior, 208 great, 208 posterior, 208 cava, inferior, 486 superior, 173 cephalic, 311, 327 median, 327 circumflex iliac, 438 coronary, of heart, 208 of stomach, 469 dorsal of penis, 519 dorsi-spinal, 781 elbow in front of, 327 epigastric, 437 facial. 40, 94 femoral, 628 frontal, 4 of Galen, 14, 765 gastric, 469 haemorrhoidal, 474, 529 hepatic, 469, 580 iliac, common, 491 external, 492 internal, 529 inferior cava, 486 innominate, 172 intercostal, superior, 183 interlobular, 579 intralobular, 579 jugular anterior, 67 external, 66 internal, 84 posterior external, 67 kidney of, 484 lumbar, 486 mammary internal, 160 maxillary internal, 137 median, 340 deep, 340 medulli-spinal, 782 meningeal, 16 INDEX. 879 VEI Veins (continued) meningo-rachidian, 782 mesenteric inferior, 474 superior, 473 oblique, of Marshall, 201 occipital, 4, 108 ophthalmic, 59 pharyngeal, 109 phrenic, 484 popliteal, 668, 678 portal, 580 profunda femoris, 639 pudic, external, 613 internal, 543 pulmonary, 224 radial, 346 ranine, 106 rectum, 532 renal, 484, 595 sacra media, 486 salvatella, 340 saphenous external, 673 internal, 613 scalp of, 4 scapular posterior, 121 supra, 121 spermatic, 487, 845 spinal longitudinal anterior, 781 posterior, 782 posterior external, 780 splenic, 469, 588 subclavian, 123 sublobular, 579 supra-orbital, 4 renal, 484 scapular, 121 temporal, 128 superficial, 4 Thebesii, 208 thyroid superior, 98 tibial posterior, 682 tympanum of, 824 ulnar anterior, 340 posterior, 340 umbilical, 213, 215 uterine, 567 vaginal, 567 of liver, 580 vertebral, 120 Velum interpositum, 765 medullary anterior, 770 ZYG Velum (continued) medullary posterior, 776 pendulum palati, 232 Venae vorticosse, 801 Ventral hernia, 447 Ventricle of brain, fifth, 760 fourth, 771 lateral, 756 third, 767 Ventricle of heart, left, 206 right, 202 muscular fibres of, 211 Ventricle of larynx, 247 Vermiform process, inferior, 776 superior, 775 Vertebral aponeurosis, 279, 373 artery, 119, 719 ' Vincula tendinum, 364 Verumontanum, 552 Vesico-prostatic plexus, 529 Vesicula seminalis, 536 structure of, 554 vessels of, 554 Vestibule of ear, 825 vagina, 523 Vestigial fold of pericardium, 170 Vibrissffi, 276 Vidian artery, 136 nerve, 263 Vieussens, valve of, 770 Vitreous body, 813 Vocal cords, inferior or true, 246 superior or false, 245 Wharton's duct, 141 Willis, circle of, 720 cords of, 12 Winslow, foramen of, 462 posterior ligament of, 670 Wirsung, canal of, 476, 585 Wrisberg, cartilages of, 242 ganglion of, 196 nerve of, 326 Wrist-joint, synovial membranes of, 416 triangular fibro-cartilage of, 411 Zinn, ligament of, 61 zone of, 814 Zygomaticus major, 28 minor, 28 Sfoltiswoode & Co., Printers, New-street Square, London. \ CATALOGUE JANUARY, 189.. 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Ballou. Veterinary Anat. i.oo Heath. Practical, yth Ed. 5.00 Holden. Dissector. Oil-cloth, 4.50 Osteology. - - 600 Landmarks. 4th Ed. 1.25 Macalister's Text-Book. 816 lllus. Clo. 7.50; Sh. 8.50 Potter. Compend of. 4th Ed. 117 Illustrations. - i.oo Sutton. Ligaments. - 1.25 ATLASES AND DIAGRAMS. Bentley & Trimens. - 90.00 Flower. Of Nerves. - 3.50 Heath. Operative Surgery. 12.00 Marshall's Phys. and Anat. Diagrams. $40.00 and 60.00 Savage. Pelvic Organs. 12.00 BRAIN AND INSANITY. Bucknill and Tuke. Psycho- logical Medicine. - - 8.00 Gowers. Diagnosis of Dis- eases of the Brain. New Ed. 2.00 Lewis, (Bevan). Mental Diseases. ... 6.00 Mann's Psychological Med. 5.00 Wood. Brain and Overwork. .50 CHEMISTRY. See Technological Books. Allen. Commercial Organic Analysis. 2d Ed. Volume I. 4.50 Volume II. - - 5.00 Volume III. Parti. 4.50 Bartley. Medical. - 2.50 Bloxam's Text- Book. 7th Ed. 4.50 Bowman's Practical. - 2.00 Groves and Thorp. Chemi- cal Technology. Vol. I. Fuels 7.50 Holland's Urine, Poisons and Milk. - ... LOO Leffmann's New Compend. i.oo , Progressive Exercises, i.oo Muter. Pract. and Anal. 2.00 Richter's Inorganic. 3d Ed. 2.00 Organic. - - 3.00 Smith. Electro-Chem. Anal, i.oo Stammer. Problems. - .75 Sutton. Volumetric Anal. 5.00 Symonds. Manual of. 2.00 Tidy. Modern Chem. zd Ed. 5.50 Trimble. Analytical. 1.50 Valentin. Qualt. Anal. 7th Ed. 3. Watts. (Kowne's) Inorg. 2. ^ (Fowne's) Organ. Wolff. Applied Medical. Woody. Essentials of. CHILDREN. Chavasse. Mental Culture of. i.oo Day. Diseases of. - - 3.00 Dillnberger. Women and. 1.50 Goodhart and Starr. 3 oo; 811.3.50 Hale. Care of. - .75 Hatfield. Compend of. i.oo Meigs. Infant Feeding and Milk Analysis. . i.oo Meigs and Pepper's Treatise. 5.00 Money. Treatment of. - 3 oo Osier. Cerebral Palsies of. 2.00 Smith. Wasting Diseases of. 3.00 Clinical Studies. - 2.50 Starr. Digestive Organs of. 2.25 Hygiene of the Nursery, i.oo 25 2.25 i.oo 1-25 CLINICAL CHARTS. Davis. Obstetrical. Pads, $ .50 Griffiths. Graphic. .50 Temperature Charts. " .50 COMPENDS And The Quiz-Compends. Ballou. Veterinary Anat. i.oo Brubaker's Physiol. $th Ed. i.oo Hox and Gould. The Eye. i.oo Hatfield. Children. - i.oo Horwitz. Surgery. 3d Ed. i.oo Hughes. Practice. 2 Pts. Ea. i.oo Landis. Obstetrics. 4th Ed. i.oo Leffmann's Chemistry. 3d Ed. i.oo Mason. Electricity. - i.oo Morris. Gynaecology. - i.oo Potter's Anatomy, 4th Ed. i.oo Materia Medica. sthEd. i.oo Roberts. Mat. Med. and Phar. 2.00 Stewart, Pharmacy. 2d Ed. i.oo Warren. Dentistry. - i.oo DEFORMITIES. Churchill. Face and Foot. 3.50 Coles. Of Mouth. - 4.50 Prince. Orthopaedics. - 4.50 Reeves. " - 2.25 Roberts. Club-foot. - .50 DENTISTRY. Barrett. Dental Surg. - 1.25 Blodgett. Dental Pathology. 1.75 Flagg. Plastic Filling. - 4.00 Fillebrown. Op. Dent. lllus. 2.50 Gorgas. Dental Medicine. 3.50 Harris. Principles and Prac. 7.00 Dictionary of. - 6.50 Heath. Dis. of Jaws. - 4.50 Lectures on Jaws. Bds. i.oo Leber and Rottenstein. Caries. Paper 75; Cloth 1.25 Richardson. Mech. Dent. 4.50 Sewell. Dental Surg. - 3.00 Stocken. Materia Medica. 2.50 Taft. Operative Dentistry. 4.25 , Index of Dental Lit. 2.00 Talbot. Irregularity of Teeth. 3.00 Tomes. Dental Surgery. 5.00 Dental Anatomy. 4.00 Warren's Compend of. - i.oo White. Mouth and Teeth. .50 DICTIONARIES. Cleveland's Pocket Medical. .75 Gould's New Medl. ^ Lea., 3-25; 54 M. Thumb Index. 4.25 Harris' Dental. Clo. 6.50; Shp. 7.50 Longley's Pronouncing - i.oo Maxwell. Terminologia Med- ica Polyglotta. - - 4.00 Treves. German English. 3.75 DIRECTORY. Medical, of Philadelphia, 2.50 EAR. Burnett. Hearing, etc. .50 Jones. Aural Surgery. - 2.75 Pritchard. Diseases of. 1.50 ELECTRICITY. Althaus' Text Book. - 6.00 Mason's Compend. - i.oo EYE. Arlt. Diseases of. - - 2.50 Fox and Gould. Compend. i.oo Gower's Ophthalmoscopy. 5.50 Harlan. Eyesight. .50 Hartridge. Refraction. 4th Ed. 2.00 Higgins. Practical Manual. 1.75 Handbook, - .50 Liebreich. Atlas of Ophth. 15.00 Macnamara. Diseases of. % Meyer and Fergus. Com- plete Text-Book, with Colored Plates. 270 lllus. Clo. 4.50; 811.5.50 Morton. Refraction. 3d Ed. i.oo Ophthalmic Review. Monthly. - 3.00 Swanzy's Handbook. 3d Ed. 3.00 FEVERS. Collie, On Fevers. - 2 50 Welch. Enteric Fever. 2.00 HEADACHES. Day. Their Treatment, etc. 1.25 HEALTH AND DOMESTIC MEDICINE. Bulkley. The Skin. - .50 Burnett. Hearing. - .50 Cohen. Throat and Voice. .50 Dulles. Emergencies. 3d Ed. .75 Harlan. Eyesight. - .50 Hartshorne. Our Homes. Hufeland. Long Life. - Lincoln. Hygiene. Osgood. Dangers of Winter. Packard. Sea Air, etc. Richardson's Long Life. Tanner. On Poisons. - White. Mouth and Teeth. Wilson. Summer and its Dis. .50 Wilson's Domestic Hygiene, i.oo Wood. Brain Work. - .50 HEART. Fothergill. Diseases of. 3.50 HISTOLOGY. See Microscope and Pathology. HYGIENE. Frankland. Water Analysis, i.oo Fox. Water, Air, Food. 4.00 Lincoln. School Hygiene. .50 Parke's (E.) Hygiene. 7th Ed. 4.50 (L. C.), Manual. 2.50 5 i.oo .50 5 .50 50 75 5 Starr. Hygiene of the Nursery, i.oo Wilson's Handbook of. - Domestic. - - i.oo JOURNALS, ETC. Archives of Surgery. 4 Nos. 3.00 Jl. of Dermatology. " " 3.00 Ophthalmic Review. " " 3.00 New Sydenham Society's Publications - - - 9.00 KIDNEY DISEASES. Beale. Renal and Urin. 1.75 Edwards. How to Live with Bright's Disease. - - .50 Ralfe. Dis. of Kidney, etc. 2.75 Thornton. Surg. of Kidney. 1.75 Tyson. Bright's Disease and Diabetes, lllus. - 3.50 LIVER. Habershon. Diseases of. 1.50 Harley. Diseases of. - 3.00 LUNGS AND CHEST. See Phy. Diagnosis and Throat. Hare. Mediastinal Disease. 2.00 Harris. On the Chest. - 2.50 Williams. Consumption. 5.00 MASSAGE. Murrell. Massage, sth Ed. 1.50 Ostrom. Massage, lllus. .75 MATERIA MEDICA. Biddle. nth Ed. 00.4.25 Gorgas. Dental. 3d Ed. 3.50 Merrell's Digest. - 4.00 Potter's Compend of. 5th Ed. i co CLASSIFIED LIST OF P. BLAKISTON, SON CO.'S TYSON. Bright's Disease and Diabetes. With Especial Reference to Pathology and Therapeutics. By JAMES TYSON, M.D., Professor of Pathology and Morbid Anatomy in the University of Pennsylvania. Including a Section on Retinitis in Bright's Disease. By WM. F. NORRIS, M.D., Clin. Prof, of Ophthalmology, in Univ. of Penna. With Colored Plates and many Wood Engravings. 8vo. Cloth, $3.50 Guide to the Examination of Urine. Seventh Edition. For the Use of Physicians and Students. With Colored Plates and Numerous Illustrations Engraved on Wood. Seventh Edition. Revised. I2mo. 255pages. Cloth, $1.50 Cell Doctrine. Its History and Present State. With a Copious Bibliography of the subject. Illustrated. Second Edition. 8vo. Cloth, $2.00 VALENTIN'S Qualitative Analysis. A Course of Qualitative Chemical Analysis. By WM.G. VALENTIN, F.C.S. Seventh Edition. Illustrated. Octavo. Cloth, $3.00 VAN HAELIN6EN on Skin Diseases. A Practical Manual of Diagnosis and Treatment. By ARTHUR VAN HARLINGEN, M.D., Professor of Diseases of the Skin in the Philadelphia Polyclinic ; Clinical Lecturer on Dermatology at Jef- ferson Medical College. Second Edition. Revised and Enlarged. With Formulae. Eight Colored and other full page plates, and New Illustrations. Cloth, $2.50 VAN NUYS on The Urine. Chemical Analysis of Healthy and Diseased Urine, Qualitative and Quantitative. By T. C. VAN NUYS, Professor of Chemistry Indiana University. 39 Illustrations. Octavo. Cloth, $2.00 VIRCHOW'S Post-mortem Examinations. A Description and Explanation of the Method of Performing them in the Dead House of the Berlin Charite Hospital, with especial reference to Medico-legal Practice. By Prof. VIRCHOW. Trans- lated by Dr. T. P. SMITH. Third Edition, with Additions. Cloth, $I.OD Cellular Pathology, as based upon Physiological and Pathological Histology. 20 Lectures delivered at the Pathological Institute of Berlin. Translated from the 2d Ed. by F. CHANCE, M.D. 134 Illus. 8th Am. Ed. Cloth, $4.00 WALSH AM. Manual of Practical Surgery. For Students and Physicians. By WM. J. WALSHAM, M.D., F.R.C.S., Asst. Surg. to, and Dem. of Practical Surg. in, St. Bartholomew's Hospital, Surg. to Metropolitan Free Hospital, London. With 236 Engravings. New Series of Manuals. Cloth, $3.00 ; Leather, $3.50 WARING. Practical Therapeutics. A Manual for Physicians and Students. By Edward J. Waring, M.D. Fourth Edition. Revised, Rewritten and Rearranged by DUDLEY W. BUXTON, M.D., Assistant to the Professor of Medicine, University College, London. Crown Octavo. Cloth, $3.00; Leather, $3.50 WARREN. Compend Dental Pathology and Dental Medicine. Containing all the most noteworthy points of interest to the Dental student. By GEO. W. WARREN, D.D.S., Clinical Chief, Penn'a College of Dental Surgery, Phila. Illus. Being No. /j ? Quiz- Compend? Siries. I2mo. Cloth, $1.00 Interleaved for the addition of notes, $1.25 WATSON on Amputations of the Extremities and Their Complications. By B. A. WATSON, A.M., M.D., Surgeon to the Jersey City Charity Hospital and to Christ's Hospital, Jersey City, N. J. ; Member of the American Surgical Associ- ation. 250 Wood Engravings and two Full-page Colored Plates. Cloth, $5.50 Concussions. An Experimental Study of Lesions arising from Severe Con- cussions. 8vo. Paper cover, $1.00 WATTS' Inorganic Chemistry. A Manual of Chemistry, Physical and Inorganic. (Being the i4th Edition of FOWNE'S PHYSICAL AND INORGANIC CHEMISTRY.) By HENRY WATTS, B.A., F.R.S., Editor of the Journal of the Chemical Society ; Author of " A Dictionary of Chemistry," etc. With Colored Plate of Spectra and other Illustrations. I2mo. 595 pages. Cloth, $2.25 Organic Chemistry. Second Edition. By WM. A. TILDEN, D.SC., F.R.S. (Being the i3th Edition of FOWNE'S ORGANIC CHEMISTRY.) Illustrated. I2mo. Cloth, $2.25 WELCH'S Enteric Fever. Its Prevalence and Modifications ; Etiology, Pathology and Treatment. By FRANCIS H. WELCH, F.R.C.S. 8vo. Cloth, $2.00 MEDICAL AND SCIENTIFIC PUBLICA TIONS. 25 WHITE. The Mouth and Teeth. By J. W. WHITE, M.D., D.D.S. Editor of the Dental Cosmos. Illustrated. Cloth, .50 WILLIAMS. Pulmonary Consumption. Its Etiology, Pathology and Treatment, with an Analysis of 1000 Cases to Exemplify its Duration and Modes of Arrest. By C. J. B. WILLIAMS, M.D. Second Edition. Enlarged and Rewritten. By C. THEODORE WILLIAMS, M.D. With Illustrations. Octavo. Cloth, $5.00 WILSON'S Text-Book of Domestic Hygiene and Sanitary Information. A Guide to Personal and Domestic Hygiene. By GEORGE WILSON, M.D., Medical Officer of Health. Edited by Jos. G. RICHARDSON, M.D., Professor of Hygiene at the University of Pennsylvania. Cloth, $1.00 WILSON. Handbook of Hygiene and Sanitary Science. With Illustrations. Seventh Edition, Revised and Enlarged. 8vo. In Press. WILSON. The Summer and Its Diseases. By JAMES C. WILSON, M.D. Cloth, .50 WINCKEL. Diseases of Women. Second Edition. Including the Dis- eases of the Bladder and Urethra. By Dr. F. WINCKEL, Professor of Gynaecology, and Director of the Royal University Clinic for Women, in Munich. Translated by special authority of Author and Publisher, under the supervision of, and with an Introduction by, THEOPHILUS PARVIN, M.D., Professor of Obstetrics and Diseases of Women and Children in Jefferson Medical Col- lege, -Philadelphia. With 1 50 Engravings on Wood, most of which are original 2d Edition, Revised and Enlarged. Cloth, $3.00; Leather, $3.50 Text-Book of Obstetrics ; Including the Pathology and Therapeutics of the Puerperal State. Authorized Translation by J. CLIFTON EDGAR, A.M., M.D., Adjunct Professor to the Chair of Obstetrics, Medical Department, University, City of New York. With nearly 200 Handsome Illus., the majority of which are original with this work. Octavo. Cloth, $6.00; Leather, $ J. oo WOAKES. Post-Nasal Catarrh and Diseases of the Nose, causing Deafness. By EDWARD WOAKES, M.D., Senior Aural Surgeon to the London Hospital for Diseases of the Throat and Chest. 26 Illustrations. Cloth, $1.50 Nasal Polypus, with Neuralgia, Hay Fever and Asthma in Relation to Ethmoiditis. I2mo. Cloth, $1.25 WOLFF. Manual of Applied Medical Chemistry for Students and Practitioners of Medicine. By LAWRENCE WOLFF, M.D., Demonstrator of Chemistry in Jeffer- son Medical College, Philadelphia. Cloth, $1.00 WOOD. Brain Work and Overwork. By Prof. H. C. WOOD, Clinical Professor of Nervous Diseases, University of Pennsylvania. I2mo. Cloth, .50 WOODY. Essentials of Chemistry and Urinalysis. By SAM E. WOODY, A.M., M.D., Professor of Chemistry and Public Hygiene, and Clinical Lecturer on Diseases of Children, in the Kentucky School of Medicine. Third Edition. Illustrated. I2mo. Cloth, $1.25 WYNTER and WETHERED. Clinical and Practical Pathology. A Manual of Clinical and Practical Pathology. By W. ESSEX WYNTER, M.D., Medical Reg- istrar and late Dem. of Anat. and Chem. at the Middlesex Hospital, and FRANK J. WETHERED, M.D., Asst. Phys. to the City of London Hospital for Dis. of the Chest. 4 Colored Plates and 67 other Illustrations. 8vo. Cloth, $4.00 WYTHE on the Microscope. A Manual of Microscopy and Compendium of the Microscopic Sciences, Micro-mineralogy, Biology, Histology and Practical Medi- cine, with Index and Glossary and the genera of microscopic plants. By JOSEPH H. WYTHE, A.M., M.D. Fourth Edition. 252 Illus. Cloth, $3.00 Dose and Symptom Book. The Phvsician's Pocket Dose and Symptom Book. Containing the Doses and Uses of all the Principal Articles of the Materia Medica, and Officinal Preparations. iyth Edition, Revised and Rewritten. Cloth, $1.00; Leather, with Tucks and Pocket, $1.25 YEO'S Manual of Physiology. Fourth Edition. A Text-book for Students of Medicine. By GERALD F. YEO., M.D. F.R.C.S., Professor of Physiology in King's College, London. Fourth Edition ; revised and enlarged by the author. With New Illustrations. 321 Wood Engravings and a Glossary. Crown Octavo. Being No. 4, New Series of Manuals. Cloth, $3.00 ; Leather, $3 .50. New Series of Manuals. FOR MEDICAL STUDENTS AND PHYSICIANS. Demi-Octavo. Price of each, book, Cloth, $3.00 ; Leather, $3.50. The object held in view in the preparation of this Series was to make books that should be concise and pract cal, not burdened by useless theories and discussions, but containing all that is needed or necessary for the student and practitioner. No pains have been spared to bring them up to the times, and the very low price at which they have been published is an additional point in their favor. Full circular, descriptive of the Series, will be sent upon application. WALSHAM'S PRACTICAL SURGERY. A Manual for Students and Physicians. By WM. J. WALSHAM, M.D., Asst. Surgeon to, and Demonstrator of Surgery in, St. Bartholomew's Hospital; Sur- geon to Metropolitan Free Hospital, London, etc. 236 Illust. 656 pp. t Cloth, $3.00; Leather, $3.50 From the Polyclinic. " While evidently intended to be a text-book for students, and therefore small in size and compactly written, is neverthe- less full enough for the use of those practitioners who desire a short account of the various surgical principles and operation? involved in the treatment of the ordinary run of surgical cases. The author seems to-be a conservative and judicious surgeon PARVIN'S-WINCKEL'S DISEASES OF WOMEH. Second Edition. A Treatise on the Dis- eases of Women. Including the Diseases of the Bladder and Urethra. By DR. F. WINCKEL, Professor of Gynaecology and Director of the Royal University Clinic for Women, in Munich. Revised and Edited by THEOPHILUS PARVIN, M.D., Professor of Obstetrics and Diseases of Women and Children in Jeffer- son Medical College. Illustrated by 150 fine Engravings on Wood, most of which are new. 760 pp. Cloth, $300; Leather, $3.50 GALABIN'S MIDWIFERY. A Manual of Widwifery. By AIFRED LEWIS GALABIN, M.A., M.D., Obstetric Physician and Lecturer on Midwifery and the Diseases of Women at Guy's Hospital, London; Examiner in Midwifery to the Conjoint Examining Board of England. 227 Illustrations. 753 pages. Cloth, $3.00; Leather, $3.50 From the Archives of Gyntecology, New York. " The illustrations are mostly NEW and WELL EXECUTED, and we heartily commend this book as far superior to any manual YEO'S^MANUAL OF PHYSIOLOGY. Fourth Edition. A New Text-book for Students. By GERALD F. YEO, M.D., F.R.C.S., Professor of Physiology in King's College, London. 321 Illustra- tions and a Glossary. 758 pages. Cloth, $3.00; Leather, 53-5 RICHTER'S ORGANIC CHEMISTRY. By PROF. VICTOR VON RICHTER, University of Breslau. Authorized translation. First American, from the Fourth German Edition. By EDGAR F. SMITH, M.D., PH.D , Translator of Richter's Inorganic Chemistry ; Prof, of Chemistry in Wittenberg College, Spring- field, Ohio; formerly in the Laboratories of the University of Pennsylvania; Member of the Chemical Societies of Berlin and Paris, of the Academy of Natural Sciences of Philadelphia, etc. Illustrated. 710 pages. Cloth, $300; Leather. $3.50 GOODHARTAND STARR, DISEASES OF CHILDREN. Second Edition. By J. F.GOOL-HART, M.D., Physician to the Evelina Hospital for Children; Assistant Physician to Guy's Hospital, London. Second American from third English Edition. Revised and Edited by Louis STARR, M.D., Clinical Professor of Diseases of Children in the Hospital of the University of Pennsylvania, and Physician to the Children's Hospital, Phila. With many new Prescriptions and Directions for making Artificial Human Milk, for the Artificial Digestion of Milk, etc. 760 pages. Cloth, $3.00; Leather, $3.50 From The New York Medical Record. "As it is said of some men, to it might be said ot some books, that they are 'born to greatness.' This new volume has we believe, a mission, particularly in the hands of the young members of the profession. In these days of prolixity in medical literature, it is refreshing to meet with an author who knows both what to say and when he has said it." WARING'S PRACTICAL THERAPEUTICS. Fourth Edition. A Manual of Practical Thera- peutics, considered with reference to Articles of the Materia Medica. Containing, also, an Index of Diseases, with a list of Medicines applicable as Remedies, and a full Index of the Medicines and Preparations noticed in the work. By EDWARD JOHN WARING, M.D., F.R.C.P., F.L.S., etc. 4th Edition. Rewritten and Revised. Edited by DUDLEY W. BUXTON. M.D., Asst. to the Prof, of Medicine at University College Hospital; Member of the Royal College of Physicians of London. 666 pages. Cloth, $3.00; Leather, $3.50 From The Kansas Citv Medical Record. ''As a work of reference it excels, on account of the several complete indexes added to this edition. It was deservedly popular in former editions, and will be more so in the one before us, on account of the careful arrangement of the subjects." REESE'S MEDICAL JURISPRUDENCE AND TOXICOLOGY. Second Edition. By JOHN J. REESE, M.D., Professor of Medical Jurisprudence and Toxicology in the University of Pennsylvania ; late President of the Medical Jurisprudence Society of Philadelphia; Physician to St. Joseph's Hospital; Member of the College of Physicians of Phila.; Corresponding Membtr of the New York Medico- Legal Society, etc. 2d Edition. Revised and Enlarged. 654 pages. Cloih, $300; Leather, #3.50 THE MOST PRACTICAL SERIES OF TEXT-BOOKS. JUST PUBLISHED. THIRD EDITION. HUMAN PHYSIOLOGY. BY LANDOIS AND STIRLING. With 692 Illustrations. THIRD AMERICAN, FROM THE SIXTH GERMAN EDITION. A Text-Book of Human Physiology, including Histology and Microscopical Anatomy, with special reference to the requirements of Practical Medicine. By Dr. L. LANDOIS, Professor of Physiology and Director of the Physiological Institute, University of Greifswald. Translated^ from the Fifth German Edition, with addi- tions by WM. STIRLING, M.D., SC.D., Brackenbury, Professor of Physiology and Histology in Owen's College and Victoria University, Manchester; Examiner in the Honors' School ofScience, University of Oxford, England. Third Edition, revised and enlarged. 692 Illustrations. "A BRIDGE BETWEEN PHYSIOLOGY AND PRACTICAL MEDICINE." One Volume. Eoyal Octavo. Cloth, $6.50 ; leather, $7.50. From the Prefaces to the English Edition. The fact that Prof. Landois' book has passed through four large editions in the original since 1880, and that in barely six months' time a second edition of the English has been called for, shows that in some special way it has met a want. The characteristic which has thus commended the work will be found mainly to lie in its eminent practicability; and it is this consideration which has induced me to undertake the task of putting it into English. Landois' work, in fact, forms a Bridge between Physiology and the Practice of Medicine. It never loses sight of the fact that the student of to-day is the practicing physician of to-morrow. In the same way, the work offers to the busy physician in practice a ready means of refreshing his memory on the theoretical aspects of Medicine. He can pass backward from the examination of patho- logical phenomena to the normal processes, and, in the study of these, find new indications and new lights for the appreciation and treatment of the cases under consideration. With this object in view, all the methods of investigation which may, to advantage, be used by the practitioner, are carefully and fully described. Many additions, and about one hundred illustrations, have been introduced into this second English edition, and the whole work carefully revised. PRESS NOTICES. " Most effectively aids the busy physician to trace from morbid phenomena back the course of divergence from healthy physical operations, and to gather in this way new lights and novel indications for the COMPREHENSION AND TREATMENT of the maladies with which he is called upon to cope." American Journal of Medical Sciences. " I know of no book which is its equal in the applications to the needs of clinical medicine." Prof. Harrison Allen, late Professor of Physiology, University of Pennsylvania. " We have no hesitation in saying that THIS is THE WORK to which the PRACTITIONER will turn whenever he desires light thrown upon the phenomena of a COMPLICATED OR IMPORTANT CASE." Edinburgh Medical Journal. " So great are the advantages offered by Prof. LANDOIS' TEXT-BOOK, from the EXHAUSTIVE and EMINENTLY PRACTICAL manner in which the subject is treated, that it has passed through FOUR large editions in the same number of years. . . . Dr. STIRLING'S annotations have materially added to the value of the work. Admirably adapted for the PRACTITIONER. . . . With this Text-book at command, NO STUDENT COULD FAIL IN HIS EXAMINATION." The Lancet. "One of the MOST PRACTICAL WORKS on Physiology ever written, forming a ' bridge ' between Physiology and Practical Medicine. . . . Its chief merits are its completeness and conciseness. . . . The additions by the Editor are able and judicious. . . . EXCELLENTLY CLHAR, ATTRACTIVE and SUCCINCT." British Medical Journal. " The great subjects dealt with are treated in an admirably clear, terse, and happily illustrated manner." Practitioner. " Unquestionably the most admirable exposition of the relations of Human Physiology to Practical Medicine ever laid before English readers " Stuaents' Journal. " As a work of reference, LANDOIS and STIRLING'S Treatise OUGHT TO TAKE THE FOREMOST PLACE among the text- books in the English language. The wood-cuts are noticeable for their number and beauty." Glasgow Medical Journal. "Landois' Physiology is, without question, the best text-book on the subject that has ever been written." New York Medical Record. " The chapter on the Brain and Spinal Cord will be a rrost valuable one for the general reader, the translator's notes adding not a little to its importance. The sections on Sight and Hearing are exhaustive. . . . The Chemistry of the Urine is thoroughly considered. ... In its present form, the value of the original has been greatly increased. . . . The text is smooth, accurate, and unusually fiee from Germanisms ; in fact, it is good English." New York Medical Journal . " It is not for the physiological student alone that Prof. Landois' book possesses great value, for IT HAS BEEN ADDRESSED TO THE PRACTITIONER OF MEDICINE as well, who will find here a direct application of physiological to pathological processes." Medical Bulletin. P. BLAKISTON, SON & CO., Publishers, 1012 Walnut St., Philadelphia. DISEASES OF THE SKIN, BY T. MCCALL ANDERSON, M.D., Professor of Clinical Medicine in the University of Glasgow. ASSISTED BY DR. JAMES CHRISTIE, Sec'y London Epidemiological Society for Indian Ocean and East Africa; Mem. Medical Soc. of Bombay, etc. DR. HECTOR C. CAMERON, Surgeon and Lecturer to Western Infirmary, Glasgow; Surgeon to Glasgow Hospital for Children, etc. WILLIAM MACEWEN, M.B., M.D., Lecturer on Systematic and Clinical Surgery, Royal Infirmary; Surgeon to Royal Infirmary and Children's Hospital, Glasgow, etc. WITH COLORED PLATES AND NUMEROUS WOOD ENGRAVINGS. Octavo. 650 Pages. Cloth, $4.50 ; Leather, $5.50. A treatise on Diseases of the Skin, with reference to Diagnosis and Treatment, including an Analysis of 11,000 Consecutive Cases. Thoroughly illustrated by new and handsome wood engravings, and several colored and steel plates prepared, under the direction of the author, from special drawings by Dr. John Wilson. PARTICULARLY STRONG IN TREATMENT. 8s&* Special attention is given to the Differential Diagnosis of Skin Diseases and to the treatment. There are over 150 prescriptions, which will serve as hints to the physician in dealing with obstinate and chronic cases. There has been no complete treatise on Dermatology issued for several years ; Professor Anderson has, therefore, chosen an opportune time to publish his book. ILLUSTRATING ONE OF THE DISEASES OF THE HAIR (See fig. fy, page 7). For nearly twenty-five years Professor Anderson has been a general practitioner and a hospital physician, with unusual opportunities for the study of this class of diseases, though not a "specialist," as the term is understood. His experience is, therefore, of great value, and the physician will feel that, in consulting this work, he is reading the expe- riences of a man situated as himself with the same difficulties of diagnosis and treatment, and who has surmounted them successfully. We believe this to be a- valuable feature of the book that will be recognized at once; for it is undoubtedly a fact that a work like the present contains much practical information and many hints not to be found else- where. Professor Anderson is particularly happy in illustrating the impor- tant relations subsisting between the general economy and its covering, and his ideas of pathology and therapeutics, including a consideration of all the general and local manifestations of the common diseases of the economy which are manifested upon the surface, will find many appreciative readers. Diseases of the hair receive full systematic treatment. " We welcome Dr. Anderson's work not only as a friend, but as a benefactor to the profession, because the author has stricken off mediaeval shackles of insuperable nomenclature and made crooked ways straight in the diagnosis and treatment of this hitherto but little understood class of diseases. The chapter on Eczema is, alone, worth the price of the book." Nashville Medical A ews. NEW AND REVISED EDITIONS } PQU1Z-COMPENDS.P A SERIES OF PRACTICAL MANUALS FOR THE PHYSICIAN AND STUDENT. Compiled in accordance with the latest teachings of prominent lecturers and the most popular Text-books. Bound in Cloth, each $1.00. Interleaved, for the Addition of Notes, $1.25. They form a most complete, practical and exhaustive set of manuals, containing information nowhere else collected in such a practical shape. Thoroughly up to the times in every respect, containing many new prescriptions and formulae, and over 300 illustrations, many of which have been drawn and engraved specially for this series. The authors have had large experience as quiz-masters and attaches of colleges, with exceptional opportunities for noting the most recent advances and methods. The arrangement of the subjects, illustrations, types, etc., are all of the most approved form. They are constantly being revised, so as to include the latest and best teachings, and can be used by students of any college of medicine, dentistry and pharmacy. No. i. Human Anatomy. Fifth Edition, including Visceral Anatomy, formerly published separately. 16 Lithograph Plates, Tables, and 117 Illustrations. By SAMUEL O. L. POTTER, M.A., M.D., late A. A. Surgeon, U. S. Army. Professor of Practice, Cooper Med. College, San Francisco. Nos. 2 and 3. Practice of Medicine. Fourth Edition, Enlarged. By DANIEL E. HUGHES, M.D., late Demonstrator of Clinical Medicine in Jefferson Med. College, Phila. ; Physician-in Chief, Philadelphia Hospital. In two parts. PART I. Continued, Eruptive and Periodical Fevers, Diseases of the Stomach, Intestines, Peritoneum, Biliary Passages, Liver, Kidneys, etc. (including Tests for Urine), General Diseases, etc. PART II. Diseases of the Respiratory System (including Physical Diagnosis), Circulatory System and Nervous System ; Diseases of the Blood, etc. *$* These little books can be regarded as a full set of notes upon the Practice of Medicine, containing the Synonyms, Definitions, Causes, Symptoms, Prognosis, Diagnosis, Treatment, etc., of each disease, and including a number of prescriptions hitherto unpublished. No. 4. Physiology, including Embryology. Fifth Edition. By ALBERT P. BRUBAKER, M.D., Prof, of Physiology, Penn'a College of Dental Surgery; Demonstrator of Physiology in Jefferson Med. College, Phila. Revised, Enlarged and Illustrated. No. 5. Obstetrics. Illustrated. Fourth Edition. For Physicians and Students. By HENRY G. LANDIS, M.D., Prof, of Obstetrics and Diseases of Women, in Starling Medical College, Columbus. Revised Edition. New Illustrations. No. 6. Materia Medica, Therapeutics and Prescription Writing. Fifth Revised Edition. With especial Reference to the Physiological Action of Drues, and a complete article on Prescription Writing. Based on the Last Revision (Sixth) of the U. S. Pharma- copoeia, and including many unofficinal remedies. By SAMUEL O. L. POTTER, M.A., M.D., late A. A. Surg. U. S. Army ; Prof, of Practice, Cooper Med. College, San Francisco. 5th Edition. Improved and Enlarged. No. 7. Gynaecology. A Compend of Diseases of Women. By HENRY MORRIS, M.D., Demonstrator of Obstetrics, Jefferson Medical College, Philadelphia. Many Illustrations. No. 8. Diseases of the Eye and Refraction, including Treatment and Surgery. By L. WEBSTER Fox, M.D., Chief Clinical Assistant Opthalmological Dept., Jefferson Medical College, etc., and GEO. M. GOULD, M D. 71 Illustrations, 39 Formulae. 2d Edition. No. 9. Surgery, Minor Surgery and Bandaging. Illustrated. Fourth Edition. Includ- ing Fractures, Wounds, Dislocations, Sprains, Amputations and other operations; Inflam- mation, Suppuration, Ulcers, Syphilis, Tumors, Shock, etc. Diseases of the Spine, Ear, Bladder, Testicles, Anus, and other Surgical Diseases. By ORVILLE HORWITZ, A.M., M.D., Demonstrator of Surgery, Jefferson Medical College. 84 Formulae and 136 Illustrations. No. 10. Medical Chemistry. Third Edition. Inorganic and Organic, including Urine Analysis. For Medical and Dental Students. By HENRY LF.FFMANN, M.D., Prof, of Chem- istry in Penn'a College of Dental Surgery, Phila. Third Edition. Revised and Enlarged. No. II. Pharmacy. Based upon "Remington's Text-Book of Pharmacy." By F. E. STEWART, M.D., PH.G., Professor of Pharmacy, Powers College of Pharmacy; late Quiz- Master at Philadelphia College of Pharmacy. Third Edition. Revised. No. 12. Veterinary Anatomy and Physiology. Illustrated. By WM. R. BALLOU, M.D., Prof, of Equine Anatomy, New York College of Veterinary Surgeons, etc. 29 Illustrations. No. 13. Dental Pathology and Dental Medicine. Containing all the most noteworthy points of interest to the Dental student. By GEO. W. WARREN, D.D.S., Clinical Chief, Penn'a College of Dental Surgery, Philadelphia. Illus. No. 14. Diseases of Children. By MARCUS P. HATFIELD, Professor of Diseases of Children, Chicago Medical College. With Colored Plate. These books are constantly revised to keep up with the latest teachings and discoveries. "IT STANDS WITHOUT AN EQUAL AS THE MOST COMPLETE WORK ON PRACTICE IN THE ENGLISH LANGUAGE." New York Medical Journal. FAGGE'S PRACTICE OF MEDICINE, Two Large Royal Octavo Volumes. Containing over 1900 Pages. PRICE, HANDSOMELY BOUND IN CLOTH, S8.OO. The Principles and Practice of Medicine. BY CHARLES HILTON FAGGE, M.D., F.R.C.P., F.R.M.C.S., Examiner in Medicine, University of London; Physician to, and Lecturer on Pathology in, Guy's Hospital; Senior Physician to Evelina Hospital for Sick Children, etc. EDITED AND ARRANGED FOR THE PRESS BY P. H. PYE-SMITH, M.D., F.R.C.P., Lecturer on Medicine in Guy's Hospital, London, etc. , WITH A SECTION ON CUTANEOUS AFFECTIONS, BY THE EDITOR, A CHAPTER ON CAR- DIAC DISEASES, BY SAMUEL WlLKES, M. D., F. R. S., AND TWO INDEXES, ONE OF AUTHORS AND ONE OF SUBJECTS, BY ROBERT EDMUND CARRINGTON. Two Volumes. Royal Octavo. 1900 Pages. Price in Cloth, $3.00. Full Leather, $10.00. Half Morocco, $12.00. Half Russia, $12.00. It is based on laborious researches into the pathological and clinical records of Guy's Hospital, London, during the twenty years in which the author has held office there as Medical Registrar, as Pathologist, and as Physician. Familiar beyond most, if not all, of his contemporaries, with modern medical literature, a diligen'. reader of French and German periodicals, Dr. Fagge, with his remarkably retentive memory and methodical habits, was able to bring to his work of collection and criticism almost unequaled opportunities of extensive experience in the wards and dead house. The result is that which will probably be admitted to be a fuller, more original, and more elaborate text-book on medicine than has yet appeared. It is the first of importance emanating from Guy's Hospital, and the only two-volume work on the Practice of Medicine that has been issued for a number of years. Several subjects, such as Syphilis, that are usually omitted or but slightly spoken of in a general work of this character, receive full attention. Dr. Walter Moxon, one of Dr. Fagge's contemporaries, and a great personal friend, writes of him, in a recent number of the London Lancet : " Fagge was, to my mind, the type of true medical greatness. I believe he was capable of any kind of excellence. His greatness as a physician became evident to observers of character very soon after his brilliant student career had placed him on the staff of Guy's Hospital; he did not merely group already known facts, but he found new facts. Former volumes of Guy's Hospital Reports contain ample and most valuable proof of his greatness as a physician. ' His power of observation was sustained by immense memory, and brought into action by vivid and constant suggestiveness of intelligence. He was a physician by grace of nature, and being gifted with a quickness of perception, a genius for clinical facts and a patience in observation, he was at once recognized as a successful practitioner and a leading figure in the hospital and among the profession. NEW TEXT-BOOKS. Macalister's Human Anatomy. 816 Illustrations (400 of which are Original). Just Ready. A NEW TEXT BOOK for Students and Practitioners, Systematic and Topographical, including the Embryology, Histology and Morphology of Man. With special reference to the requirements of Practical Surgery and Medicine. By ALEX. MACALISTER, M.D., F.R.S., F.S.A., Professor of Anatomy in the Univer- sity of Cambridge, England; Examiner in Zoology and Comparative Anatomy, University of London ; formerly Professor of Anatomy and Surgery, University of Dublin. With 816 Illustrations, 400 of which are original. Octavo. Cloth, $7.50; Leather, $8.50 > *** Professor Macalister's reputation as an Anatomist and Zoologist is such that nothing need be said of the scientific value of this book. Regarding the illustrations, printing and binding we may say, however, that the workmanship is of the best character in every respect. No expense has been spared to make a handsome vol- ume, the 400 original illustrations adding greatly to its appearance as well as to its practical value as a working book for students and physicians. Potter's Materia Medica, Pharmacy and Therapeutics. Second Edition. Revised and Enlarged. A HANDBOOK OF MATERIA MEDICA, PHARMACY AND THERAPEUTICS including the Physiological Action of Drugs, Special Therapeutics of Diseases, Official and Extemporaneous Pharmacy, etc. By SAM'L O. L. POTTER, M.A., M.D., Professor of the Practice of Medicine in Cooper Medical College, San Francisco; Late A. A. Surgeon, U. S. Army, Author of "Speech and its Defects," and the "Quiz- Compends" of Anatomy and Materia Medica, etc. Revised, Enlarged and Im- oroved. Octavo. With Thumb Index in each copy. Cloth, $4.00; Leather, $5.00 " The author has aimed to embrace ia a single volume the essentials of practical materia medica and therapeutics, and has produced a book small enough for easy carriage and easy ref- erence, large enough to contain a carefully digested, but full, clear and well-arranged mass of information. He has not adhered to any pharmacopoeia, as is the case of certain recent manuals, thereby limiting his woik, and in this day of new remedies causing c nstant disappointment, but has brought it up to date in the most satisfactory way. No new remedy of any acknowledged value is omitted from this list. Under each the section on physiological action and therapeutics has been written with care. ... In the enumeration of drugs suited to different disorders a very successful efiort at discrimination has been made, both in the stage of disease and in the cases peculiarly suited to the remedy. It is no mere list of diseases followed by a catalogue of drugs, but is a digest of modern therapeutics, and as such will prove of immense use to its possessor." The Therapeutic Gazette. Winckel's Obstetrics. Original Illustrations. A TEXT-BOOK OF OBSTETRICS, INCLUDING THE PATHOLOGY AND THERAPEUTICS OF THE PUERPERAL STATE. By DR. F. WiNCKEL, Professor of Gynaecology, and Director of the Royal University Clinic for Women, in Munich. Authorized Translation, by J. CLIFTON EDGAR, M.D., Adjunct Professor to the Chair of Obstetrics, Medical Dept., University, of the City of New York, with nearly 200 handsome illustrations, the majority of which are original with this work. Octavo. Cloth, $6.00; Leather, #7.00 PUBLISHED ANNUALLY. 1891. NOW READY. 40 YEAR. T HE PHYSICIAN'S VISITING ]JST. (LINDSAY & BLAKISTON'S.) CONTENTS. ALMANAC for 1890 and 1891. TABLE OF SIGNS to be used in keeping accounts. MARSHALL HALL'S READY METHOD IN ASPHYXIA. POISONS AND ANTIDOTES, revised for 1890. THE METRIC OR FRENCH DECIMAL STSTBM OF WEIGHTS AND MEASURES. DOSE TABLE, revised and rewritten for 1890, by Hc- BART AMORY HARE, M.D, Demonstrator of Thera- peutics, University of Pennsylvania. LIST OF NEW REMEDIES for 1890, by same author. AIDS TO DIAGNOSIS AND TREATMENT OF DISEASES OF THE EYE, DR. L. WEBSTER Fox, Clinical Asst. Eye Dept., Jefferson Medical College Hospital, and G. M. GOULD, M.D. DIAGRAM SHOWING ERUPTION OF MILK TEETH, DR. Louis STARR, Prof, of Diseases of Children, Univer- sity Hospital, Philadelphia. POSOLOGICAL TABLE, MEADOWS. DISINFECTANTS AND DISINFECTING. EXAMINATION OF URINE, DR. J. D ALAND, based up