Digitized by the Internet Archive in 2017 with funding from University of Illinois Urbana-Champaign Alternates https://archive.org/details/ellissdemonstratOOelli 9 DEMONSTRATIOP t OP ANATOMY BEING A GUIDE TO THE KNOWLEDGE OF THE HUMAN BODY BY DISSECTION. BY GEORGE YINER ELLIS, EMERITUS PROFESSOR OF ANATOMY IN UNIVERSITY COLUEOK, LONDON, FROM THE EIGHTH AND REVISED ENGLISH EDITION. ILLUSTRATED BY TWO HUNDRED AND FORTY-NINE ENGRAVINGS ON WOOD. PHILADELPHIA: HENRY O. LEA. 1879 . 0 4 " ' PREFACE. The plan of this work is designed to teach the Anatomy of the lluman Body by dissection in successive stages after the following manner: — In the dissection of a Part the attention of the Student is directed first to the superficial prominences of bone and muscle, and to the hollows that point out the situation of the subjacent vessels. Next the cutaneous structures, and the different layers of muscles with their appertaining vessels and nerves are examined in succession, so that the several objects between the surface of the Body and the bones may be observed in much the same order as they would be met with in a Surgical operation. And, lastly, the joints and liga- ments receive due notice. In the dissection also of the viscera and the organs of the senses the manner in which the composition of each may be shown, is fully indicated for the guidance of the Student. The Anatomical description of the Part under examination is arranged in conformity with the dissection in regions, and each muscle, bloodvessel, nerve, or other structure, is described only to such an extent as it may be laid bare. Since the publication of the last edition great changes have been made in textural Anatomy; and the chief of these, for which I am indebted to Quain’s Anatomy, I have introduced into my account of the microscopic structure of the different organs. In this edition, as in the preceding ones, I have endeavored to make the work more complete by the correction of inaccuracies, and to render it more efficient as a guide to practical work. G. V. ELLIS. October, 1878. CONTENTS CHAPTER I. DISSECTION OF THE HEAD AND NECK. PAGE Section 1. External Parts of tlie Head . . . . .17 2. Internal Parts of tlie Head . . . . .24 3. The Face ........ 34 4. The Orbit ........ 50 5. The Neck, right side . . . . . . G1 Posterior triangular space . . . .63 Front of the Neck . . . . .67 . Anterior triangular space . . . .69 6. Pterygo-maxillaiy Region . . . . . .87 7. Suhraaxillary Region . . . . . .97 8. Superior Maxillary Nerve and Vessels .... 103 9. Deep Vessels and Nerves of the Neck .... 105 10. Left side of the Neck ...... 118 11. The Pharynx ....... 122 12. The Mouth ........ 132 13. Cavity of the Nose ....... 133 14. Spheno-palatine and Otic Oanglia, Facial and Nasal Nerves, and Internal Maxillary Artery ..... 138 15. The Tongue ........ 146 16. The Larynx ........ 151 17. Hyoid Bone, Cartilages and Ligaments of the Larhyx, Structure of the Trachea ....... 158 18. Prevertebral Muscles and the Vertebral Vessels . . . 163 19. Ligaments of the first two Cervical Vertebrae, and of the Clavicle 166 CHAPTER II. DISSECTION OF THE BRAIN. Section 1. Membranes and Vessels ...... 172 2. Origin of the Cranial Nerves ..... 177 3. Medulla Oblongata and Pons Varolii , . . .182 VI CONTENTS. Section 4. The Cerebrum, or Grreat Brain The under surface, or the Base The upper surface and lobes . Convolutions . The Interior Ventricles of the Brain Floor of the lateral Ventricle . Central Parts of the Cerebrum Structure of the Cerebrum 5. The Cerebellum, or little Brain Surfaces and Lobes Structure of the Mass . Fourth Ventricle CHAPTER III. DISSECTION OF THE UPPER LIMB. Section 1. 2 . 3. 4. 5. 6 . 7. The Wall of the Thorax .... The Axillary Space .... Scapular Muscles, Vessels, Nerves, and Ligaments The Front of the Arm .... Back of the Arm .... The Front of the Forearm .... The Palm of the Hand .... The Back of the Forearm .... Ligaments of the Shoulder, Elbow, Wrist, and Hand CHAPTER IV. DISSECTION OF THE THORAX. Section 1. Cavity of the Thorax ...... The Pleurae . . . . Connections of the Lungs ..... The Pericardium ...... The Heart and its large Vessels . . . . Nerves of the Thorax ...... The Trachea and the Characters and Structure of the Lung Parts in Front of the Spine, and the Cord of the Sympathetic Parieties of the Thorax ..... 2. Ligaments of the Trunk ...... Articulation of the Ribs to the Vertebrae Articulation of the Ribs to the Sternum Articulations of the Sternum ..... Articulations of the Vertebrae .... PAGE 189 190 193 195 199 200 203 205 209 211 212 215 217 224 228 240 248 257 260 272 282 290 305 307 308 310 312 329 333 336 342 343 343 346 346 346 CONTENTS. CHAPTER Y. DISSECTION OF THE BACK. First Layer of Muscles .... Second Layer of Muscles Third Layer of Muscles Fourth Layer of Muscles with Vessels and Nerves Fifth Muscular Layer, and the Sacral Nerves CHAPTER VI. DISSECTION OF THE SPINAL CORD. Membranes of the Cord .... Roots of the Spinal Nerves .... Vessels of the Cord ..... Form and Divisions of the Cord Structure of the Cord, and the deep Origin of the Nerves Intraspinal Vessels ..... CHAPTER VII. . DISSECTION OF THE PERINEUM. Section 1. Perinseum of the Male Posterior Half of the Space Anterior Half of the Space Lateral Operation of Lithotomy 2. Perinaeum of the Female CHAPTER VIII. DISSECTION OF THE ABDOMEN. Section 1. Wall of the Abdomen ..... 2. Hernia of the Abdomen ..... 3. Cavity of the Abdomen ..... Connections of the Viscera .... Peritoneum and its Folds .... Mesenteric Vessels, and Part of the Sympathetic Nerve Connections of the Aorta and Vena Cava Connections of the Duodenum and Pancreas . Coeliac Axis and Vena Portae .... Sympathetic and Vagus Nerves 4. Anatomy of the Abdominal Viscera The Stomach . . . . The Small Intestine ..... The Large Intestine ..... page . 354 . 358 . 359 . 361 . 369 . 374 . 377 . 379 . 380 . 382 . 384 . 386 . 387 . 391 . 399 . 400 . 404 . 420 . 430 . 431 . 435 . 439 . 444 . 445 . 446 . 450 . 452 . 452 . 456 . 461 Vlll CONTENTS Section 4. Anatomy of tlie Abdominal Viscera — continued. The Pancreas ..... Tlie Spleen ..... The Liver ..... The Gall Bladder .... The Kidney and the Ureter The Suprarenal Body .... The Testis and the Vas Deferens 5. Diaphragm with Aorta and Vena Cava Deep Muscles of the Abdomen 6. Lumbar Plexus and the Cord of the Sympathetic Nerve PAGE . 464 . 465 . 466 . 472 . 473 . 478 . 479 . 484 . 492 . 495 DISSECTION OF THE PELVIS. Section 1. Fascia of the Cavity and the Muscles of the Pelvic Outlet . 499 2. Connections of the Viscera in the Male .... 503 3. Connections of the Viscera in the Female .... 509 4. Vessels and Nerves of the Pelvis . . . . . 513 5. Anatomy of the Viscera of the Male .... 520 The Prostate Gland and the Seminal Vesicles . . 521 The Urinary Bladder ...... 524 The Urethra and the Penis ..... 526 The Rectum ....... 532 6. Anatomy of the Viscera of the Female .... 533 Genital Organs ....... 533 The Vagina ....... 535 The Uterus ....... 537 Ovaries and Fallopian Tubes ..... 539 Bladder, Urethra, and Rectum .... 541 7. Internal Muscles of the Pelvis ..... 542 Articulations of the Pelvis ..... 543 CHAPTER IX. DISSECTION OF THE LOAVER LIMB. Section 1. The Front of the Thigh .... . 552 Femoral Hernia .... . 559 Scarpa’s Space ..... 563 Deep Muscles, Vessels, and Nerves on the Front of the Thigh 565 Deep parts on the inner Side of the Thigh . 574 2. The Buttock, or the Gluteal Region . 581 3. The Back of the Thigh .... . 592 The Popliteal Space .... . 593 Hamstring Muscles and Vessels . 597 The Hip-Joint ..... . 600 4. The Back of the Leg .... 605 5. The Sole of the Foot .... . 614 6. The Front of the Leg and the Dorsum of the Foot . 626 7. Ligaments of the Knee, Ankle, and Foot . . 634 CONTENTS. CHAPTER X. DISSECTION OF THE EYE. Sclerotic Coat and Cornea ....... Choroid Coat and Ciliary Processes ...... Ciliary Muscle ......... The Iris ......... Ciliary Vessels and Nerves ....... Chamber of the Aqueous Humor ...... The Retina and Jacob’s Membrane ...... Vitreous Body, and Hyaloid Membrane, with the Susj^ensory Ligament and the Canal of Petit. . . . ^ . Crystalline Lens and its Capsule ...... CHAPTER XI. DISSECTION OF THE EAR. The Auditory Canal ..... The Tympanum, with its Vessels and Nerves . Ossicles of the Tympanum and their Muscles and Ligaments The Osseous Labyrinth of the Inner Ear Vestibule ...... Semicircular Canals .... Cochlea, its Septum and Passages Organ of Corti ..... The Membranous Sacs, or Labyrinth . Utricle ...... Saccule ...... Bloodvessels of the Labyrinth .... Nerves of the Cochlea and Membranous Sacs . ix PAGE 655 659 660 661 663 663 663 666 668 670 671 674 679 679 680 681 684 685 685 686 687 687 LIST OF ILLUSTRATIONS FIG. PAGE 1. Extrinsic muscles of the ear ...... 19 2. Cutaneous nerves and arteries of the scalp . . . .22 3. Some of the sinuses of the skull . . . . .28 4. Cranial nerves in the base of the skull . . . . .31 5. Muscles of the nose ....... 35 6. Muscles of the mouth ....... 37 7. Lateral cartilages of the nose ...... 43 8. Muscles on the outer and inner surface of the ear cartilage . . 46 9. Cutaneous branches of the fifth nerve in the face . . .49 10. First view of the orbit ....... 52 11. Second view of the orbit ....... 55 12. Third view of the orbit . . . . . . .58 13. The eyelids and lachrymal apparatus . . . . .60 14. Part of the posterior triangle of the neck ’ . . . .64 15. View of the anterior triangular space of the neck . . .72 16. A view of the common carotid and subclavian arteries . . .74 17. External carotid and its superficial branches . . . .84 18. Superficial view of the pterygoid region . . . .89 19. Ligaments of the jaw — an inner view . . . . .91 20. A view of the interior of the compound temporo-maxillary joint . 91 21. Deep view of the pterygoid region . . . . .95 22. Muscles of the tongue ....... 100 23. Deep view of the submaxillary region ..... 102 24. Diagram of the upper maxillary nerve and its branches . . 105 25. Deep vessels and nerves of the neck ..... 108 26. Diagram of the eighth nerve . . . . . . 112 27. Diagram of the ending of the lymph duct and the thoracic duct in the veins ......... 119 28. External view of the pharynx ...... 125 29. Internal vuew of the pharynx ...... 127 30. Muscles of the soft palate . . . . . .130 31. Spongy bones and meatuses of the nasal cavity . . . 135 32. Magnified vertical section of the mucous membrane of the nose . 136 33. Nerves of the septum of the nose ..... 137 34. Nerves of the nose and palate ...... 140 35. Nerves joining the enlargement of the facial nerve . . . 143 36. Inner view of the otic ganglion ...... 145 37. Muscles on the surface of the tongue ..... 149 38. Intrinsic muscles of the tongue ...... 149 39. Front view of the larynx . . . . . . . 152 40. Hinder view of the larynx . . . . . .152 41. View of the internal muscles of the larynx . . . .154 XI 1 LIST OF ILLUSTRATIONS. FIG. 42. Vocal apparatus, on a vertical section of tlie larjnx 43. Hyoid bone and tlie laryngeal cartilages .... 44. View of the vocal cords and crico-thyroid ligaments 45. Deep muscles of the front of tlie neck and tlie scaleni muscles . 46. External ligaments in front between tlie atlas and axis and the occipital bone . . . . . . . . . 47. External ligaments behind between the atlas and axis and the occipital bone ......... 48. Internal ligament between occipital bone and axis 49. Internal ligaments between the occipital bone and the atlas and axis . 50. First vertebra with the odontoid process removed from the socket formed by the bone and the transverse ligament 51. Ligaments of the inner end of the clavicle, and of the cartilage of the second rib ........ 52. Arteries at the base of the brain ...... 53. Origin of the cranial nerves ...... 54. Anterior view of the medulla oblongata and pons 55. Hinder view of the medulla oblongata . . . . . 56. Fibres of the medulla, pons, and crus cerebri . . . . 57. Fibres of the lateral tract and of the olivary body 58. Tranverse section of the medulla oblongata above the middle of the olivary body ........ 59. Under surface of the brain ...... 60. Lobes of the hemisphere, and convolutions and fissures of the outer surface of the brain ....... 61. View of the orbital lobule and the central lobe of the brain 62. Convolutions and -fissures on the inner face of the hemisphere of the brain ......... 63. View of the lateral ventricles of the brain .... 64. Second view of the dissection of the brain .... 65. Connection posteriorly between the cerebrum, the medulla oblongata, and cerebellum ........ 66. Under part of the cerebellum, seen from behind 67. View from behind of the under surface of the cerebellum 68. View of the third and fourth ventricles of the brain 69. View of the dissected axilla ...... 70. Second view of the dissection of the thorax .... 71. Diagram of the serratus magnus muscle ..... 72. View from behind of the attachments of the triangularis sterni muscle 73. View of the subscapularis and the surrounding muscles 74. View of the muscles of the dorsum of the scapula, and of the circumflex vessels and nerve ....... 75. Ligaments of the clavicle and scaj)ula, and of the shoulder joint 76. Cutaneous veins and nerves at the bend of the elbow 77. Axillary and brachial arteries and their branches 78. Muscles and deep vessels and nerves of the arm 79. Dissection of the dorsal scapular vessels and nerve, and of the triceps muscle of the arm ....... 80. Superficial view of the forearm ...... 81. Dissection of the deep layer of muscles of the forearm, and of the vessels and nerves between the two layers of muscles of the forearm PAGE 156 160 161 164 167 167 168 169 169 171 174 178 183 183 184 185 187 190 194 196 198 201 205 210 212 214 216 229 233 237 239 241 243 246 250 253 255 257 264 268 LIST OF ILLUSTRATIONS. FIG. 82. The extensor tendon of the finger with its accessory muscles and the sheath of the flexor tendons ...... 83. Dissection of the superficial vessels and nerves of the palm of the hand with some of the superficial muscles ..... 84. Deep dissection of the palm of the hand .... 85. Three jialmar interosseous muscles ..... 86. Four dorsal interosseous muscles ..... 87. Superficial layer of muscles on the hack of the forearm, with some ves- sels ......... 88. Dissection of the deep layer of muscles, and the vessels and nerve on the back of the forearm ....... 89. View of the interior of the shoulder-joint . . . . 90. The ligaments of the elbow joint, and the shaft of the radius and ulna 91. View of the orbicular ligament of the radius .... 92. Front view of the articulations of the wrist joint, and carpal and me- tacarpal hones ........ 93. The wrist joint opened to show the arch formed by the bones of the forearm with the uniting fibro-cartilage , . . . . 94. Articulations of the carpal bones ..... 95. Posterior ligaments of the wrist, and carpal and metacarpal bones 96. Union of metacarpal bone and first phalanx . . . . 97. Diagram to show the dilFerence in the anterior border of the right and left lung ........ 98. Diagram showing the position of the heart to the ribs and sternum . 99. Back of the heart with the coronary sinus and its veins 100. Diagram of the two cavities of the right side of the heart 101. Diagram of the two cavities of the left side of the heart 102. Muscular fibres of the auricles ...... 103. A diagram of the arrangement of the fibres in layers in the left ven- tricle ......... 104. The formation of the septum ventriculorum by the fibres of both ven- tricles ......... 105. Arch of the aorta and its great vessels ..... 106. View of the thoracic duct, and the intercostal veins 107. Scheme to illustrate the connection between the spinal and sympathetic nerves . . ....... 108. Ligaments of the ribs and vertebrae ..... 109. Anterior common ligament of the bodies of the vertebrae 110a. View of the posterior common ligament of the vertebrae of the neck 110b. View of the posterior common ligament of the vertebrae of the loin . 111. Intervertebral substance in the lumbar region . . . . 112. Vertical section of the intervertebral substance 113. A horizontal cut through an intervertebral fibro-cartilage 114. An inner view of the neural arches of the vertebrae, with their inter- posed ligaments ....... 115. Ligaments of the processes of the vertebrae, and of the ribs . 116. Muscles of the back ....... 117. Part of the third layer of the back-muscles .... 118. Dissection of the muscles underneath the splenius 119. Deep dissection of the back of the neck .... Xlll PAGE 273 275 279 281 281 283 286 291 293 295 296 297 298 299 301 309 313 315 316 319 322 323 325 326 340 341 344 347 347 347 348 348 349 350 350 355 360 364 366 XIV LIST OF ILLUSTRATIONS. FIG. PAGE 120. Dissection of sacral nerves ...... 121. Lower end of the dura mater, with its central and lateral processes . 122. View of the membranes of the spinal cord . . . . 123. Roots of the spinal nerves ...... 124. Membranes of the spinal cord laid open . . . . 125. A section of the spinal cord, to show its composition, and its divisions 126. The gray substance in the interior of the spinal cord . 127. Intraspin al arteries in the loins ...... 128. Intraspinal veins in the loins 129. A view of the dissection of the rectal half of the perimeum . 130. Superficial dissection of the anterior half of the perimeum 131. Deep dissection of the perinjeum . . . . . 132. The symphysis pubis seen from behind ..... 133. The female perimeum ....... 134. The muscles of the female perinseum ..... 135. Dissection of the first lateral muscle in the wall of the belly . 136. Internal oblique muscle of the abdominal wall 137. The lower part of the internal oblique with the Cremaster muscle and the testicle . ' . 138. Dissection of the third lateral muscle in the wall of the belly 139. Rectus muscle of the abdomen ...... 140. Dissection for inguinal hernia ...... 141. View of the parts concerned in femoral hernia .... 142. Connections of the liver, stomach, spleen, and large intestine . 143. Superior mesenteric artery and its branches .... 144. The lower mesenteric artery, and the aorta .... 145. View of the coeliac axis, and of the viscera to which its branches are supplied ........ 146. Vena portae and the veins joining it . 147. Diagram representing the arrangement of the muscular fibres of the stomach ......... 148. Alveolar depressions of the mucous membrane of the stomach 149. Enlarged representation of the tubes of the stomach 150. The duodenum opened showing the valvulse conniventes, and the opening of the bile duct ...... 151a. Vessels of the villi in the mouse, injected by Gerlach 151b Lacteals and plexus of vessels in two villi, injected by Teichman 152a. Patch of Peyer’s glands four times enlarged .... 152b. Magnified representation of an injection of the vessels surrounding and penetrating the follicles in a patch of Peyer in the rabbit 153a. a piece of mucous membrane enlarged .... 153b. a piece of mucous membrane enlarged .... 154. Magnified view of the mucous membrane of the duodenum 155. Interior of the ciecum dried and laid open .... 156a. Enlarged view of “ a solitary gland” . . . . . 156b. Enlarged view of “ a solitary gland” . . . . . 157. A drawing of the trabecular structure of the spleen of the ox 158. Under surface of the liver ...... 159. A magnified representation of the hepatic cells .... 160a. Lobules of the liver, magnified ..... 372 375 375 378 380 381 383 384 384 388 392 39'6 398 401 402 409 412 413 414 415 422 428 432 440 442 448 449 454 455 455 457 458 458 459 459 460 460 460 462 464 464 466 468 470 470 LIST OF ILLUSTRATIONS. XV FIG. 160b. Lobules of the liver, magnified . . . . . 161. Vessels in a portal canal, and tlie lobules of the liver . 162. Gall-bladder and its duct ...... 163. Section tbrougli tlie kidney ...... 164. Plan of tlie arrangement of the uriniferal tubes 165. Plan of contorted urine tubes ending in Malpighian corpuscles 166a. Plan of the vessels connected with the urine tubes 166b. Plan of the vessels connected with the urine tubes 167. Vertical section of the suprarenal body . . . . . 168. The testis with the tunica vaginalis laid open .... 169. Vertical and horizontal sections of the testis . . . . 170. Under surface of the diaphragm . . 171. Deep view of the muscles, vessels, and nerves of the abdominal cavity 172. Dissection of the lumbar plexus and its branches 173. Side view of the muscles in the outlet of the pelvis 174. Side view of the dissected male pelvis . . . . . 175. Side view of the female pelvis ...... 176. Dissection of the internal iliac artery ..... 177. Dissection of the sacral nerves and plexus . . . . 178. View of the under part of the bladder with the vesiculse seminales and vasa deferentia ....... 179. Muscular fibres of the bladder, prostate, and urethra . 180. Section through the bladder, prostate, and urethra 181. View of the lower part of the bladder and of the urethra laid open . 182. View of the fibres of the case of the corpus cavernosum 183. Pectiniform septum of the penis ..... 184. Magnified view of the trabecular structure and arteries of the penis . 185. Representation of the clitoris ...... 186. Venous plexuses of the genital organs and opening of the vagina 187. Interior of the uterus, with a posterior view of the broad ligament and the uterine appendages ...... 188. Ovary during the child-bearing period laid open 189. Irregular piece of cartilage in the sacro-iliac articulation 190. Sacro-sciatic ligaments ....... 191. Ligaments of the symphysis pubis, thyroid hole, and acetabulum 192. Cutaneous nerves on the front of the thigh .... 193. Dissection of the superficial parts of the thigh 194. Dissection of the crural sheath ...... 195. Dissection on Scarpa’s triangular space .... 196. Surface view of the front of the thigh, the teguments and fascia being removed ........ 197. Deep part of the femoral artery and its branches, with muscles of the thigh ......... 198. Deep dissection of the adductor muscles with their vessels and nerves 199. Superficial view of the buttock of the left side 200. Second view of the dissection of the buttock .... 201. Third view of the dissection of the buttock .... 202. View of the popliteal space ...... 203. Dissection of the back of the thigh . . . 204. Fore part of the capsule of the hip joint . . , . PAGE 470 471 473 474 476 476 477 477 479 480 482 485 488 496 501 505 511 514 519 523 524 527 528 529 530 531 534 536 538 540 545 545 546 556 558 561 563 567 569 575 582 585 591 594 598 600 Xvi LIST OF ILLUSTRATIONS. FIG. 205. Hinder part of tlie liip-joint capsule ..... 206. Hip joint opened ........ 207. First view of tlie back of the leg ..... 208. Second view of the back of the leg ..... 209. Deep dissection of the back of the leg ..... 210. First view of the sole of the foot ..... 211. Second view of the sole of the foot ..... 212. Third view of the sole of the foot ..... 213. Fourth view of the sole of the foot ..... 214. Cutaneous nerves of the front of the leg and foot 215. Anterior tibial vessel and muscles ..... 216. External ligament of the knee-joint ..... 217. Internal ligament of the knee-joint . . . 218. The capsule of the knee-joint cut across, and the patella thrown down to show the named folds of the synovial sac .... 219. Interarticular ligaments of the knee-joint .... 220. View of the head of the tibia with the fibro-cartilages attached 221. Internal lateral ligament of the ankle . . . . . 222. External lateral ligament of tlie ankle ..... 223. View of the dorsal ligaments of the tarsus .... 224. Plantar ligaments of the foot ...... 225. View of the inferior ligaments of the tarsal bones 226. Dorsal ligaments uniting the tarsus to the metatarsus, and the meta- tarsal bones to each other behind ..... 227. Diagram of a horizontal section of the eyeball 228. Vertical section of the cornea ...... 229. Inner view of the front of the choroid coat ... * 230. Pigment cells of the eyeball ...... 231. View of the front of the choroidal coat and iris 232. Distribution of the nerves and vessels of the iris 233. Objects on the inner surface of the retina .... 234. Magnified vertical section of the retina .... 235. Enlarged representation of the x^arts of the eyeball on one side oxiposite the lens ........ 236. A rex^resentation of the laminse in hardened lens 237. Views of the lens fibres after Henle ..... 238. Vertical section of the meatus auditorium and tympanum 239. View of the inner wall of the tympanum enlarged 240. Inner view of the membrana tyinx^ani in the foetus 241. The three ossicles of the tympanum ..... 242. Plan of the ossicles in x:>osition in the tympanum 243. Jacobson’s nerve in the tynix^anum ..... 244. View of the vestibule obtained by cutting away the outer boundary of a foetus ........ 245. Representation of the semicircular canals enlarged 246. Section through the cochlea ...... 247. A diagram of a section of the tube of the cochlea enlarged 248. Petrous bone partly removed to show the membranous labyrinth in place ......... 249. Distribution of nerves to the membranous labyrinth . PAGE 601 603 607 607 611 618 618 622 622 627 630 635 635 636 638 639 642 644 645 646 646 649 656 657 659 659 660 662 664 665 667 669 669 671 673 674 675 676 678 679 681 682 683 686 688 DEMONSTRATIONS OF ANATOMY. CHAPTER I. DISSECTION OF THE HEAD AND NECK. Section I. EXTERNAL PARTS OF THE HEAD. Directions. In the dissection of the head and neck, the student should endeavor to learn the parts described in the first fifty-one pages, before the position of the body is changed ; but if want of time necessitates an omission of some part, the examination of the facial nerve (p. 47) can be best deferred till a subsequent stage. The orbit on one side, the poste- rior triangular space on both sides of the neck, and the exterior and the interior of the head, should be examined whilst the body lies in its first position on the Back. Position. The student begins with the dissection of the scalp and the muscles of the ear. To obtain the best position, raise the head to a suitable height, and turn the face to the right side. On the left side the muscles are to be seen, and on the opposite half the vessels and nerves are to be displayed. Extrinsic muscles of the Ear. Three muscles attach the ear to the side of the head. Two are above it, one elevating, the other drawing it forwards ; and the third, a retrahent muscle, is behind the ear. There are other special or intrinsic muscles of the cartilage of the ear, which will be afterwards described. Dissection. When the ear has been drawn down by hooks, the position of the upper muscle will be indicated by a slight prominence between it and the head ; and the muscular fibres may be laid bare by means of the two following incisions, made no deeper than the skin : One is to be car- ried upwards on the side of the head, for about three inches, along the cutaneous ridge before mentioned ; and the other, about the same length, is to be directed from before backwards close above the ear, so that the two may join at a right angle. On carefully raising the flaps of skin from below upwards, and removing the subjacent tissue, a thin fan-shaped muscular layer will come into view — the more anterior fibres constituting the attrahens, and the posterior the attollens aurem muscle. On drawing forwards the ear a ridge marks the situation of the posterior muscle. To remove the integuments, let the scalpel be drawn about an inch behind the ear, from the transverse cut above as far as to a level with 2 18 DISSECTION OF THE HEAD. the lobule of the ear, and then forwards below the lobule. After the piece of skin included by those cuts has been reflected towards the ear, the retrahent muscle must be sought beneath the subcutaneous tissue ; it consists of rounded bundles of fibres, and is stronger and deeper than the others. The ATTRAHENS AUREM (fig. 1, is a Small fan-shaped muscle, and, arises from the fore part of the aponeurosis of the occipito-frontalis. Its fibres are directed backwards, and are inserted into a projection on the front of the rim of the ear. Beneath it are tlie superficial temporal vessels and nerve. The ATTOLLENS AUREM (fig. 1, has the same form as the preceding, though its fibres are longer and better marked. Arising also from the tendon of the occipito-frontalis, the fibres converge to their insertion into the inner or cranial surface of the pinna of the ear — into an eminence corresponding with a fossa (tliat of the anti-helix) on the opposite aspect. The RETRAHENS AUREM (musculi retrahentes, Alb., fig. 1, consists of two or three roundish but separate bundles of fibres, which are stronger than those of the other muscles. The bundles arise from the root of the mastoid process, and pass almost transversely forAvards to be inserted by aponeurotic fibres into the lower part of the ear (concha) at its cranial aspect. The posterior auricular artery and nerve are in contact with this muscle. Action. The three preceding muscles will move the outer ear slightly in the directions indicated by their names: the anterior drawing it upwards and forwards, the middle one upwards, and the posterior backwards. The OCCIPITO-FRONTALIS MUSCLE (fig. 1, ^) covers the arch of the skull, and consists of an anterior and a posterior fleshy part, with an intervening tendon. Dissection. On the same side of the head (the left) the occipito-frontalis is to be dissected. To bring this muscle into view, a cut may be made along the middle line of the skull, from the root of the nose to the occipital protuberance ; and it may be connected in front with the transverse incision on the side of the head. The flap of skin, thus marked out, is to be raised with the subjacent fat from before back; whilst doing this the dissector will meet first with the anterior fleshy part of the muscle, next Avith a Avhite shining thin aponeurosis, and lastly AAutli the posterior fleshy belly toAvards the lateral aspect of the cranium. The aponeurosis of the muscle is easily taken away with the granular fat superficial to it ; and if the under surface of the flap of integuments presents a white instead of a yel- low appearance, the student may suspect he is removing that aponeurosis. Tlie anterior or frontal part (^) is a thin muscular layer over the os frontis, Avhich is said to take its origin beloAv. Along the line of the eye- broAv the fibres are blended with the folloAving muscles, orbicularis palpe- brarum, corrugator supercilii, and pyramidalis nasi ; and they are also fixed to the subjacent bone, viz., to the os nasi internally, and to the outer angular process of the frontal bone externally (Theile). From these at- tachments the fibres are directed upAvards to the aponeurosis, and end in it ratlier beloAV the level of the coronal suture. The posterior or occipital part (f) is stronger than the anterior ; it arises from tlie outer half or two-thirds of the upper curved line of the occipital bone, and from the mastoid portion of the temporal bone. The fibres are about one inch and a half in length, and ascend to tlie aponeurosis. The tendon., or epicranial aponeurosis, extends over the upper part of OCCIPITO-FRONTALIS MUSCLE. 19 the cranium, and is continuous across the middle line with the same struc- ture of the opposite half of the head. On the side it gives origin to the u.uricular muscles ; and a thin membrane is here prolonged from it over the fascia covering the temporal muscle, to be fixed to the side of the head. Extrinsic Muscles of the Ear. 15. Attollens aurera. 17. Retrahens aurem, only partly seen. 16. Attrahens aurem. Posteriorly, the aponeurosis is attached to the superior curved ridge of the occipital bone between the fleshy parts of the muscles of opposite sides. The aponeurotic expansion is closely united to the skin ; but it is connected to the pericranium only by a loose areolar tissue devoid of fat, so that it moves freely over the skull. Superficial to the occipito-frontalis are the cutaneous vessels and nerves of the scalp. In front the fleshy fibres of opposite sides are joined above the root of the nose. Action. When the anterior belly contracts it elevates the eyebrow, making smooth the skin at the root of the nose, and wrinkling transversely tliat of the forehead ; and continuing to contract, it draws forward the scalp. The posterior belly will move back the scalp ; and the bellies acting in succession will carry the hairy scalp forwards and backwards. Dissection. After the removal of the superior auricular muscles and the temporal vessels, together with the epicranial aponeurosis and its lateral prolongation, the attachment of the temporal fascia on the side of the head may be seen. The temporal fascia is a white, shining membrane, which is stronger than the epicranial aponeurosis, and gives attachment to the subjacent temporal muscle. Superiorly it is inserted into the curved line that limits tlie temporal fossa on the side of the skull ; and inferiorly, where it is nar- rower and thicker, it is fixed to the zygomatic arch. By its cutaneous 20 DISSECTION OF THE HEAD. surface the fascia is in contact with the muscles already examined, and with the superficial temporal vessels and nerves. An incision in the fascia, a little above the zygoma, will show it to con- sist there of two layers, which are fixed to the edges of the upper border of the zygomatic arch. Between the layers is some fatty tissue, with a small branch of the superficial temporal artery, and a slender twig of the orbital branch of the superior maxillary nerve with its artery. Dissection. The temporal fascia is now to be detached from the skull, and to be thrown down to the zygomatic arch, in order that the origin of the underlying temporal muscle may be examined. A soft areolar tissue which lies beneath it near the zygoma is to be taken away. The difference in thickness of parts of the fascia will be evident. The TEMPORAL MUSCLE is laid bare only in part. Wide and thin above, it becomes narrower and thicker at the lower end. The muscle arises from the temporal fascia, and fi’om all the surface of the impression on the side of the skull, which is named the temporal fossa. From this origin the fibres descend, converging to a tendon, which is inserted into the under surface and fore part of the coronoid process of the lower jaw. On the cutaneous surface is the temporal fascia, with the parts superfi- cial to that membrane ; and concealed by the muscle are the deep tempo- ral vessels and nerves which ramify in it. The insertion of the muscle underneath the zygomatic arch will be afterwards followed. The temporal belongs to 'the group of masticatory muscles ; and its action will be referred to with the description of the pterygoid region. Dissection. For the dissection of the vessels and nerves, let the face be now turned to the left side, and let an incision be carried along the eyebrow and the zygomatic arch to a little behind the ear, so as to allow the skin on the right half of the head to be reflected. The flap of skin is to be raised from before backwards, but the subcutaneous fat should be left till the nerves are found. Behind the ear the skin should be raised as on the other side, to un- cover the posterior auricular vessels and nerve. Along the eyebrow seek the branches of vessels and nerves which come from the orbit (fig. 2), viz., the supra-orbital vessels and nerve opposite the middle, and the supra-trochlear nerve and frontal vessels near the inner part of the orbit ; they lie at first beneath the occipito-frontalis, and the muscular fibres must be cut througli to find them. On the side of the head, in front of the ear, the superficial temporal vessels and nerve are to be traced to the vertex ; and above the zygomatic arch the branches of the facial which join an offset of the superior maxillary nerve, are to be sought. Behind the ear the posterior auricular vessels and nerve, and below it brandies from the great auricular nerve to the tip and back of the ear, are to be found ; one or more offsets of the last should be followed to their junction with the posterior auricular nerve. At the back of the head the ramifications of the occipital vessels, also the large and small occipital nerves, sliould be denuded ; the former nerve lies by the side of the artery, and the latter about midway between this vessel and the ear. Cutaneous Arteries. Tlie arteries of the scalp (fig. 2), are fur- nished by the internal and external carotid trunks, and anastomose freely over the side of the head. Only two small brandies, the supra-orbital CUTANEOUS NERVES. 21 and frontal, come from the former ; whilst three, viz., the temporal, occi- pital, and posterior auricular, belong to the latter. Tlie supra-orhital artery (c) leaves the orbit through the notch in the margin of the orbit, and is distributed on the forehead. Some of its branches are superficial to the occipito-frontalis, and ascend to the top of the head ; whilst others lie beneath the muscle, and supply it, the peri- cranium, and the bone. The frontal branch {If) is close to the inner angle of the orbit, and is mucli smaller than the preceding. It ends in branches for the supply of the muscles, integuments, and pericranium. The superficial temporal artery {d) is one of the terminal branches of the external carotid. After ascending above the zygomatic arch for about two inches, the vessel divides on the temporal fascia into anterior and posterior : — The anterior branch runs forwards with a serpentine course to the fore- head, supplying muscular, cutaneous, and pericranial offsets, and anasto- moses with the supra-orbital artery : this is the branch that is opened when blood is taken from the temporal artery. The posterior branch is larger than the other, and arches backwards above the ear towards the occipital artery, with which it anastomoses. Its offsets to the parts around are similar to those of the anterior, and it communicates with the artery of the opposite side over the top of the head. Occipital artery (a.). The terminal part of this artery, after perforat- ing the trapezius, divides into large and tortuous branches, which spread over the back of the head and the occipito-frontalis muscle. Communi- cations take place with the artery of tlie opposite side, with the posterior part of the temporal, and with the following artery. Some offsets pass deeply to supply the occipito-frontalis muscle, the pericranium, and the bone. The posterior auricular artery (jf) appears in front of the mastoid process, and divides into two branches. One (mastoid) is directed back- wards to supply the occipito-frontalis, and anastomose with the occipital artery. The other (auricular) is furnished to the retrahent muscle and the back of the pinna of the ear ; and an offset from this pierces tiie pinna to be distributed on the opposite surface. The VEINS of the exterior of the head are so similar to the arteries, that a full notice of each is not required. All the veins corresponding with branches of the internal carotid artery enter the facial vein, whilst the rest open into the jugular veins. These superficial veins communi- cate both with the sinuses in the interior of the skull by means of small branches named emissary^ and with the veins occupying the spongy sub- stance (diploe) of the cranial bones. frontal vein is directed towards the inner angle of the orbit, where it receives the supra-orbital vein, the two giving rise to the angular vein of the face : near its ending it receives small veins from the eyebrow, and from the upper eyelid and the nose. Both the superficial temporal and posterior auricular veins open into the external jugular ; and the occipital joins the internal jugular vein. Cutaneous Nerves (fig. 2). The nerves of the scalp are furnished from cutaneous offsets of both cranial and spinal nerves. The half of the head anterior to the ear receives branches from three trunks of the fifth cranial nerve, and a few twigs from the facial nerve. All the rest of the 22 DISSECTION OF THE HEAD. head is supplied by spinal nerves (anterior and posterior primary branches), except close behind the ear, where there is an offset of the facial or seventh cranial nerve. The siipra-orhital nerve (fig. 2, comes from the first trunk of the fifth nerve, and escapes from the orbit with its companion artery ; whilst Fig. 2. 1. Great auricular nerve. 5. Supra-trochlear. 2. Small occipital. 6. Supra-orbital. .3. Great occipital. 10. Superficial temporal of the upper maxil- 4. Posterior auricular of the facial. lary, and crossing it are the superficial Auriculo-temporal (not numbered) in front temporal branches of the temporal nerve, of the ear, by the side of the temporal ar- tery, d. Cutaneous Arteries of the Scalp. а. Occipital artery. d. Superficial temporal. б. Frontal. /• Posterior auricular. c. Supi’a-orbital. h. Latei-al superficial temporal. beneath the occipito-frontalis muscle, the nerve gives ofisets to it and the orbicularis palpebrarum, as well as to tlie pericranium. In the orbicularis CUTANEOUS NERVES. 23 a communication is established between this and the facial nerve. Fi- nally the nerve ends in two cutaneous branches, which ramify in the tegu- ments : — One of these (inner) soon pierces the occipito-frontalis, and reaches upwards as high as the parietal bone. The other branch (outer) is of larger size, and, perforating the muscle higher up, extends over the arch of the head as far as the ear. As the nerve escapes from the supra-orbital notch it furnishes some 'palpebral filaments to the upper eyelid. At the inner angle of the orbit is the small supra-trochlear branch (fig. 2, of the same nerve. It ascends to the forehead close to the bone, and piercing the muscular fibres ends in the integument. Branches are given from it to tlie orbicularis and corrugator supercilii, and some palpebral twigs enter the eyelid. The superficial temporal nerves are derived from the second and third trunks of the fifth nerve, and from the facial nerve. The temporal branch of the superior maxillary nerve (second trunk of the fifth) is usually a slender twig (fig. 2, which perforates the tempo- ral aponeurosis about a finger’s breadth above the zygomatic arch. When cutaneous, the nerve is distributed on the temple, and communicates with the facial nerve, also sometimes with the next. Tlie auriculo-temporal branch (fig. 2 d) of the inferior maxillary nerve (third trunk of the fifth) lies near the ear, and accompanies the temporal artery to the top of the head. As soon as the nerve emerges from beneath the parotid gland, it divides into two terminal branches : — The more pos- terior is the smaller of the two, and supplies the attrahens aurem muscle and the integument above the ear. The other branch ascends vertically in the teguments to the top of the head. The nerve also furnishes an auricular branch (upper) to the anterior part of the ear above the audi- tory meatus. The temporal branches of the facial nerve are directed upwards over the zygomatic arch and the temporal aponeurosis to the orbicularis palpe- brarum muscle : they will be described with the dissection of the trunk of the facial nerve. Tlie posterior auricular nerve (fig. 2, lies behind the ear with the artery of the same name. It arises from the facial nerve close to the stylo-mastoid foramen, and ascends in front of the mastoid process. Soon after the nerve becomes superficial it communicates Avitli the great auri- cular nerve, and divides into an occipital and an auricular branch, which are distributed as their names express : — The occipital branch is long and slender, and ends in the posterior belly of the occipito-frontalis muscle. It lies near the occipital bone, enveloped in dense fibrous structure, and furnishes offsets to the integu- ments. The auricular branch ascends to the back of the ear, supplying the retrahent muscle and the posterior surface of the pinna. The great auricular nerve of the cervical plexus (fig. 2, ^) is seen to some extent at the lower part of the ear, but its anatomy will be after- wards given with the description of the cervical plexus. The great occipital (fig. 2, is the largest cutaneous nerve at the back of the head, and is recognized by its proximity to the occipital artery. Springing from the posterior primary branch of the second cervical nerve, it perforates the muscles of the back of the neck, and divides on the occi- 24 DISSECTION OF THE HEAD. put into numerous large offsets ; these spread over the posterior part of the occipito-frontalis muscle, ending mostly in the integument. As soon as the nerve pierces the trapezius, it is joined by an offset from the third cervical nerve ; and on the back of the head it communicates with the small occipital nerve. The small occipital nerve of the cervical plexus (fig. 2, lies midway between the ear and the preceding nerve, and is continued upwards in the integuments higher than the level of the ear. It communicates with the nerve on each side, viz., the posterior auricular and the great occipital. Usually this nerve furnishes an auricular branch to the upper part of the ear at the cranial aspect, which supplies also the attollens aurem muscle. Section II. INTERNAL PARTS OF THE HEAD. Dissection. The skull is now to be opened, but before sawing the bone the dissector should detach, on the right side, the temporal muscle nearly down to the zygoma, without separating the fascia of the same name from the fleshy fibres ; and all tlie remaining soft parts are to be divided by an incision carried around the skull, about one inch above the margin of the orbit at the forehead, and as low as the protuberance of the occiput. The cranium is to be sawn in the same line as the incision through the soft parts, but the saw is to cut only through the outer osseous plate. The inner plate is to be broken through with a chisel, in order that the subja- cent membrane of the brain (dura mater) may not be injured. The skull- cap is next to be forcibly detached by inserting the lingers between the cut surfaces in front, and the dura mater will then come into view. The DURA MATER is the most external of the membranes investing the brain. It is a strong, fibrous structure, which serves as an endosteum to the bones, and supports the cerebral mass. Its outer surface is rough, and presents, now the bone is separated from it, numerous small fibrous and vascular processes ; but tliese are most marked along the line of the sutures, where the attachment of the dura mater to the bone is the most intimate. Ramifying on tlie upper part of the membrane are branches of the large meningeal vessels. Small granular bodies, glands of Pacchioni, are also seen along the middle line. The number of these bodies is very variable ; they are found but seldom before the third year, but generally after the seventh, and they increase with age. Occasionally the surface of the skull is indented by these so-called glands. Dissection. For the purpose of seeing the interior of the dura mater, divide this membrane with a scissors close to the margin of the skull, except in the middle line before and behind where the superior longitudi- nal sinus lies. The cut membrane is then to be raised towards the top of the head ; and on the right side the veins connecting it with the brain may be broken through. The inner surface of the dura mater is smooth and polished ; and this appearance is due to an epithelial layer similar to that lining serous membranes. REMOVAL OF BRAIN. 25 This external envelope of the brain consists of white fibrous and elastic tissues so disposed as to give rise to two strata, viz., an external or en- dosteal, and an internal or supporting. At certain spots those layers are slightly separated, and form thereby the spaces or sinuses for the passage of the venous blood. Moreover, the innermost layer sends processes be- tween different parts of the brain, forming the falx, tentorium, etc. The falx cerebri is the process of the dura mater, in shape like a sickle, which dips in the middle line between the hemispheres of the large brain. Its form and extent will be evident if the right half of the brain is gently separated from it. Narrow and pointed in front, where it is attached to the crista galli of the ethmoid bone, it widens posteriorly, and joins a horizontal piece of the dura mater named the tentorium cerebelli. The upper border is convex, and is fixed to the middle line of the skull as far backwards as the occipital protuberance ; and the lower or free border, concave, is turned towards the central part of the brain (corpus callosum), with which it is in contact posteriorly. In this fold of the dura mater are contained the following sinuses : — the superior longitudinal along the convex border, the inferior longitudinal in the hinder part of the lower edge, and the straight sinus at the line of junction between it and the tentorium. The superior longitudinal sinus (fig. 3, h) extends from the ethmoid bone to the occipital protuberance. Its position in the convex border of the falx will be made manifest by the escape of blood through numerous small veins, when pressure is made from before back with the finger along the middle line of the brain. When the sinus is opened it is seen to be narrow in front, and to widen behind, where it ends in a common point of union of certain sinuses (tor- cular Herophili) at the centre of the occipital bone. Its cavity is trian- gular in form, with the apex of the space turned to the falx ; and across it are stretched small tendinous cords — chordae Willisii — near the openings of some of the cerebral veins. Occasionally small glandulae Pacchioni are present in the sinus. The sinus receives small veins from the substance and exterior of the skull, and larger ones from the brain ; and the blood flows backwards in it. The cerebral veins open chiefly at the posterior part of the brain, and lie for some distance against the wall of the sinus before they perforate the dura mater ; their course is directed from behind forwards, so that the current of the blood in them is evidently opposed to that in the sinus : this disposition of the veins may be seen on the left side of the brain, where the parts are undisturbed. Directions. Before the rest of the dura mater can be examined, the brain must be taken from the head. To facilitate its removal, let the head incline backwards, whilst the shoulders are raised on a block, so that the brain may be separated somewliat from the base of the skull. For the division of the cranial nerves a sharp scalpel will be necessary ; and the nerves are to be cut longer on the one side than on the other. Removal of the brain. As a first step cut across the anterior part’of the falx cerebri, and the different cerebral veins entering the longitudinal sinus ; raise and throw backwards the falx, but leave it uncut in the middle line behind. Gently raise with the fingers the frontal lobes and the olfactory bulbs of the large brain. Next cut through the internal car- otid artery and the second and third nerves, which then appear; the large second nerve is placed on the inner, and the round third nerve on the 26 DISSECTION OF THE HEAD. outer side of the artery. A small branch of artery to the orbit should likewise be divided at this time. The brain is now to be supported in the left hand, and the pituitary body to be dislodged with the knife from the hollow in the centre of the sphe- noid bone. A strong horizontal process of the dura mater (tentorium cere- belli) comes into view at the back of the cranium. Along its free margin lies tlie small fourth nerve, which is to be cut at this stage of the proceed- ing. Make an incision through the tentorium on each side, close to its attachment to the temporal bone, without injuring the parts underneath ; the following nerves, which will be then visible, are to be divided in suc- cession. Near the inner margin of the tentorium is the fifth nerve, consist- ing of a large and small root; whilst towards the middle line of the skull is the long slender sixth nerve. Below the fifth, and somewhat external to it, is the seventh nerve with its facial and auditory parts, the former being anterior and the smaller of the two. Directly below the seventh are the three trunks of the eighth nerve in one line : — of these, the upper small piece is the glosso- pharyngeal ; the flat band next below, the pneu- mogastric ; and the long round nerve ascending from the spinal canal, the spinal accessory. The remaining nerve nearer the middle line is the ninth, which consists of two small pieces. After dividing the nerves, cut through the vertebral arteries as they wind round the upper part of the spinal cord. Lastly, cut across the spinal cord as low as possible, as well as the roots of the spinal nerves that are attached on each side. Then on placing the first two fingers of the right hand in the spinal canal, the cord may be raised, and the whole brain may be taken readily from the skull in the left hand. Preservation of the hrain. After removing some of the membranes from the upper part, and making a few apertures through them on the under surface, the brain may be immersed in spirit to harden the texture ; and methylated spirit may be used on account of its cheapness. Placing the brain upside down on a piece of calico long enough to wrap over it, put it in the spirit. Examination of the hrain. At the end of two or three days the dissec- tor should examine the other membranes, and the vessels. As soon as the vessels have been learnt, the membranes are to be carefully removed from the surface of the brain, without detaching the different cranial nerves at the under surface. The brain may remain in the spirit till the dissection of the head and neck has been completed, but it should be turned over occasionally to allow the spirit to penetrate its substance. The description of the brain and its vessels will be found after that of the head and neck. Directions. After setting aside the brain, the anatomy of the dura mater, and the vessels and nerves in the base of the skull sliould be proceeded with. For this purpose raise the head to a convenient height, and fasten the tentorium in its natural position with a few stitches. The dissector should be furnished with the base of a skull while studying the following parts. Dura mater. At the base of the cranium the dura mater is much more closely united to the bones than it is at the top of the skull. Here it dips into the different inequalities of the osseous surfaces ; and it sends processes through the several foramina, which join for the most part the pericra- nium, and furnish sheaths to the nerves. Beginning the examination in front, the membrane will be found to send SINUSES OF CRANIUM. 27 a prolongation into the foramen caecum, as well as a series of tubes through the apertures in the cribriform plate of the ethmoid bone. Through the sphenoidal fissure it joins the periosteum of the orbit ; and through the optic foramen a covering is continued on the optic nerve to the eyeball. Behind the sella Turcica, the dura mater adheres closely to the basilar process of the occipital bone ; and it may be traced into the spinal canal through the foramen magnum, to the margin of which it is very firmly united. The tentorium cerehelli is the piece of the dura mater which is interposed in a somewhat horizontal position between the small brain (cerebellum), and the posterior part of the large brain (cerebrum). Its upper surface is raised along the middle, where it is joined by the falx cerebri, and is hollowed laterally for the reception of tlie back part of the cerebral hemispheres. Its under surface touches the little brain, and is joined by the falx cerehelli. The anterior concave margin is free, except at the ends where it is fixed by a narrow slip to each anterior clinoid process. The posterior or con- vex part is connected to the following bones : — occipital (transverse groove), inferior angle of the parietal, petrous portion of the temporal (upper border), and posterior clinoid process of the sphenoid. Along the centre of the tentorium is the straight sinus; and in the at- tached edge are the lateral and the superior petrosal sinus on each side. Falx cerebri. The characters of this fold have been given in page 2o. The Falx cerehelli has the same position below the tentorium as the falx cerebri above that fold. It is much smaller than the falx of the cerebrum, and will appear on detaching the tentorium. Triangular in form, this fold is adherent to the middle ridge of the occipital bone below the pro- tuberance, and projects between the hemispheres of the small brain. Its base is directed to the tentorium ; and the apex reaches the foramen mag- num, to each side of which it gives a small slip. In it is contained the occipital sinus. The SINUSES are venous spaces between the layers of the dura mater, into which blood is received. All the sinuses open either into a large space named torcular Herophili, opposite the occipital protuberance; or into the two cavernous sinuses on the sides of the body of the sphenoid bone. A. The TORCULAR Herophili (fig. 3, a) is placed in the tentorium, opposite the centre of the occipital bone. It is of an irregular shape, and numerous sinuses open into it, viz., the superior longitudinal above, and the occipital below ; the straight in front, and the lateral sinus on each side. The superior longitudinal sinus has been already described (see p. 25). The inferior longitudinal sinus (fig. 3, c) resembles a small vein, and is contained in the lower border of the falx cerebri at the posterior part. This vein receives blood from the falx and the larger brain, and ends in the straight sinus (d) at the edge of the tentorium. The straight sinus (fig. 3, d) lies along the middle of the tentorium, and seems to continue the preceding sinus to the common point of union. Its form is triangular, like the superior longitudinal. Joining it are the inferior longitudinal sinus, the veins of Galen from the interior of the large brain, and some small veins from the upper part of the cerebellum. The occipital sirius (fig. 3, g) is a small space in the falx cerehelli, which reaches to the foramen magnum, and collects the blood from the occipital fossae. This sinus may be double. 28 DISSECTION OF THE HEAD. The lateral sinus (fig. 3, e) is the channel by which most of the blood passes from the skull. There is one on each side, right and left, which extends from the occipital protuberance to the foramen jugulare, where it ends in the internal jugular vein. In this extent the sinus occupies the winding groove in the interior of the skull between the two points of bone before mentioned : and the right is frequently larger than the left. Fig. 3. a. Torcular Herophili. h. Superior longitudinal sinus. c. Inferior longitudinal. d. Straight sinus. e. Lateral sinus. g. Occipital sinus. /. Superior, and h, inferior petrosal sinus. Some of the Sinuses of the Skull. Besides small veins from the brain, it is joined by the superior petrosal sinus (/), opposite the upper edge of the petrous portion of the temporal bone ; and by the inferior petrosal (h) at the foramen jugulare. Often- times it communicates with the occipital vein through the mastoid fora- men, and sometimes with veins of the diploe of the skull. The foramen jugulare is divided into three compartments by bands of the dura mater. Through the posterior interval the lateral sinus passes ; through the anterior the inferior petrosal sinus ; and through the central one the pieces of the eighth nerve. Dissection. To examine the cavernous sinus on the left side, cut through the dura mater by the side of the body of the sphenoid bone from the anterior to the posterior clinoid process, and internal to the position of the third nerve : behind the clinoid process, let the knife be directed in- wards for about half the width of the basilar part of the occipital bone. By placing the handle of the scalpel in the opening thus made, the extent of the space will be defined. A probe or a blow-pipe will be required, in order that it may be passed into the different sinuses joining the cavernous centre. B. The CAVERNOUS sinus, which has been so named from the reticu- late structure in its interior, is situate on the side of the body of the sphenoid bone. This space, resulting from the separation of the two layers of tlui dura mater, is of an irregular shape, and extends from the sphenoidal fissure to the tip of the petrous portion of the temporal bone. The piece of dura mater bounding the sinus externally is of some thick- ness, and contains in its substance the third and fourth nerves, with the ophthalmic trynk of the fifth nerve ; these lie in their numerical order from above down. The cavity of the sinus is larger behind than before, and in it are shreds of fibrous tissue with small vessels. Through the space winds the MENINGEAL ARTERIES. 29 trunk of the internal carotid artery surrounded by the sympathetic, with the sixth nerve on the outer side of the vessel ; but all these are shut out from the blood in the space by a thin lining membrane. The cavernous sinus receives the ophthalmic vein of the orbit, some inferior cerebral veins, and twigs from the pterygoid veins outside the skull. It communicates with its fellow on the opposite side by the circular and transverse sinuses ; and its blood is transmiited to the lateral sinus by the superior and inferior petrosal channels. The circular sinus lies around the pituitary body, and reaches from the one cavernous sinus to the otlier across the middle line. Besides serving as the means of communication between those sinuses, it receives small veins from the pituitary body. This sinus is usually destroyed by the removal of the pituitary body. The transverse or hasilar sinus crosses the basilar process of the occipi- tal bone, on a level with the petrous part of the temporal bone, and unites the opposite cavernous sinuses. A second transverse sinus is sometimes found nearer the foramen magnum. The superior petrosal sinus (fig. 3,^) lies in a groove in the upper edge of the petrous part of the temporal bone, and extends between the cavernous and lateral sinuses. A small vein from the cerebellum, and an- other from the internal ear, are received into it. The inferior petrosal sinus (fig. 3, h) extends between the same sinuses as the preceding, and lies in a groove along the line of junction of the petrous part of the temporal with the basilar process of the occipital bone; it is joined by a small vein from the outside of the skull, through the fora- men lacerum in the base of the cranium. This sinus passes through the anterior compartment of the jugular foramen, and ends in the internal jugular vein. Meningeal Arteries. These arteries supplying the cranium and the dura mater come through the base of the skull ; they have been named from their situation in the three fossae, anterior, middle, and posterior meningeal. The anterior meningeal are very small branches of the ethmoidal arteries (p. 56), which enter the skull by apertures between the frontal and eth- moid bones ; they are distributed to the dura mater over and near the ethmoid bone. The middle meningeal arteries are three in number : two, named large and small, are derived from the internal maxillary trunk ; and the third is an offset of the ascending pharyngeal artery. a. The large meningeal branch of the internal maxillary artery appears through the foramen spinosum of the sphenoid bone, and ascends towards the anterior inferior angle of the parietal bone. At this spot the vessel enters a deep groove in the cranium, and ends in ramifications which spread over the side of the head, some of them reaching to the top and the occiput, whilst others perforate the bone, and end on the exterior of the head. Two veins accompany the artery. Branches. As soon as the artery comes into the cranial cavity, it furnishes branches to the dura mater and osseous structure, and to the ganglion of the fifth nerve. One small offset, petrosaf enters the hiatus Fallopii, and supplies the surrounding bone (Hyrtl). One or two branches pass into the orbit, and anastomose with the ophthalmic artery. b. The small meningeal branch is an offset of the large one outside the 30 DISSECTION OF THE HEAD. skull, and is transmitted through the foramen ovale to the membrane lining the middle cranial fossa. c. Another meningeal branch from the ascending pharyngeal artery comes through the foramen lacerum (basis cranii). This is seldom in- jected, and is not often visible. The posterior meningeal branches are small, and are furnished by the occipital and vertebral arteries. Tliat from the occipital, one on each side, enters the skull by the jugu- lar foramen ; and that from the vertebral arises opposite the foramen mag- num. Both vessels ramify in the posterior fossa of the skull. Meningeal Nerves. Offsets to the dura mater are said to be derived from the fourth, fifth, glosso-pharyngeal, and vagus, cranial nerves, and from the sympathetic nerve. To make these nerves apparent, it would be necessary to steep the dura mater in diluted nitric acid. Cranial Nerves (fig. 4). The cranial nerves pass from the encepha- lon through apertures in the base of the skull. As each leaves the cranium it is invested by processes of the membranes of the brain, which are thus disposed : — those of the dura mater and pia mater are lost on the nerve ; whilst that of the arachnoid membrane is reflected back, after a short dis- tance, to tlie interior of the skull. Some of the nerves, those in the middle fossa of the skull for instance, receive sheaths of the dura mater before they approach the foramina of transmission. The nerves will be referred to now as nine pairs, but notice will be subsequently taken of a different mode of enumerating them. Only part of the course of each nerve will be seen at this stage, the rest will be learnt in the dissection of the base of the brain. The FIRST nerve (fig. 33) ends anteriorly in the enlargement of the olfactory bulb. This swelling lies on the cribriform plate of the ethmoid bone, and supplies about twenty branches to the nose through the small foramina in the subjacent bone. These delicate nerves are surrounded by prolongations of the membranes of the brain, and their arrangement will be noticed in the dissection of the nose. The SECOND nerve (fig. 4, diverging from its commissure to the eye- ball, enters the orbit through the optic foramen ; accompanying the nerve is the ophthalmic artery. Dissection. The third and fourth nerves, and the ophthalmic trunk of the fifth nerve, lie in the outer wall of the cavernous sinus ; and to see them, it will be necessary to trace them through the dura mater towards the orbit. Afterwards the student should follow outwards the roots of the fifth nerve into the middle fossa of the skull, as in fig. 4, taking away the dura mater from them, and from the surface of the large Gasserian ganglion which lies on the point of the petrous portion of the temporal bone. From the front of the ganglion arise other two large trunks besides the ophthalmic, viz., superior and inferior maxillary, and these should also be traced to their apertures of exit from the skull. If the dura mater is removed en- tirely from the bone near the nerves a better dissection will be obtained. The THIRD nerve (fig. 4, is destined for the muscles of the orbit. It enters the wall of the cavernous sinus near the anterior clinoid process, and is deprived at that spot of its tube of arachnoid membrane. In the wall of the sinus it is placed above the other nerves ; but when it is about to enter the orbit through the sphenoidal fissure, it sinks below the fourth and a part of the fifth, and divides into two branches. NERVES IN BASE OF SKULL. 31 Near the orbit the nerve is joined by one or two delicate filaments of the cavernous plexus (p. 33). The FOURTH NERVE (fig. 4, courscs forwards, like the preceding, to one muscle in the orbit. It is tlie smallest of the nerves in the wall of the sinus, and is placed below the third ; but as it is about to pass through the sphenoidal fissure it rises higlier than all the other nerves. Fig. 4. Cranial Nerves in the Base of the Skull. The dura mater has been removed in the middle fossa, on the left side, to show the nerves in the wall of the cavernous sinus, and especially the ganglion, and the three trunks of the fifth nerve. Each nerve, except the first which is absent, is marked by its corresponding numeral. On the right side the dura mater is untouched, t Offsets to the dura mater fiom the fifth nerve. In the wall of the sinus the fourth nerve is joined by twigs of the sym- pathetic ; and it is sometimes united with the ophthalmic trunk of the fifth. Fifth Nerve (fig. 4, ®). This nerve is distributed to the face and head, and consists of two parts or roots — a large or sensory, and a small or motory. The large root of the nerve passes through an aperture in the dura mater into the middle fossa of the base of the skull, where it ends imme- diately in the Gasserian ganglion. The ganglion of the root of the fifth nerve Gasserian ganglion), placed in a depression on the point of the petrous part of the temporal bone, is fiattened, and is nearly as wide as the thumb-nail. The upper surface of the ganglion is closely united to the dura mater, and presents a semilunar elevation, wliose convexity looks forwards. Some filaments from the plexus of the sympathetic on the carotid artery join its inner side. Branches. From the front of the ganglion proceed the three following trunks: — The ophthalmic nerve, the first and highest, is destined for the orbit and forehead. Next in order is the superior maxillary nerve, which leaves the skull by the foramen rotundum, and ends in the face below the 32 DISSECTION OF THE HEAD. orbit. And the last, or the inferior maxillary nerve, passes through the fora- men ovale to reach the lower jaw, the lower part of the face, and the tongue. The smaller root, entering the same tube of the dura mater as the large one, passes beneath the ganglion, without communicating with it, and joins only one of the three trunks derived from the ganglion : if the ganglion be raised, this root will be seen to enter the inferior maxillary nerve. Those branches of the o:ano!:lion which are unconnected with the smaller or motor root, viz., the ophthalmic and superior maxillary, are solely nerves of sensibility ; but the inferior maxillary, which is compounded of both roots, is a nerve of sensibility and motion. But the whole of the inferior maxillary nerve has not this double function, for the motor root is mixed almost exclusively with the part which supplies the muscles of the lower jaw ; and it is, therefore, chiefly that small piece of the nerve which pos- sesses a twofold action, and resembles a spinal nerve. The ophthalmic nerve is the only one of the three trunks which needs a more special notice in this stage of the dissection. It is continued through the sphenoidal fissure and the orbit to the forehead. In form it is a flat band, and is contained in the wall of the cavernous sinus below the third and fourth nerves. Near the orbit it divides into three branches (p. 51). In this situation it is joined by filaments of the cavernous plexus of the sympathetic, and gives a small recurrent filament (fig. 4, f) to that part of the dura mater which forms the tentorium cerebelli (Arnold). The SIXTH NERVE (fig. 4, enters the orbit through the sphenoidal As- sure, and supplies one of the orbital muscles. It pierces the dura mater behind the body of the sphenoid bone, and crosses the space of the caver- nous sinus, instead of lying in the outer wall with the other nerves. In the sinus the nerve is placed close against the outer side of the carotid artery ; and it is joined by one or two large branches of the sym- pathetic nerve surrounding that vessel. Seventh Nerve according to Willis (fig. 4, '^). This cranial nerve consists of two trunks, fascial and auditory, and both enter the meatus auditorius internus. In the bottom of the meatus they separate ; the facial nerve courses through the aqueduct of Fallopius to the face, and the audi- tory nerve is distributed to the internal ear. Eighth Nerve (fig. 4, ®). Three trunks are combined in the eightli cranial nerve of Willis, viz., glosso- pharyngeal, pneumogastric, and spinal accessory. All three pass through the central compartment of the foramen jugulare, but all are not contained in one tube of the membranes of the brain. The glosso-pharyngeal nerve is external to the other two, being separated from them by the inferior petrosal sinus, and has distinct sheaths of the dura mater and the arachnoid membrane ; but the pneumo-gastric and spinal accessory nerves are inclosed in the same tube of the dura mater, only a piece of the arachnoid intervening between them. The NINTH NERVE (fig. 4, ®) is the motor nerve of the tongue, and con- sists of two small pieces, which pierce separately the dura mater opposite the anterior condyloid foramen ; these unite after passing through that aperture. Dissection. The dissector may now return to the examination of the trunk of the carotid artery as it winds through the cavernous sinus. On the opposite side of the head, viz., tliat on which the nerves in the wall of the cavernous sinus are untouched, an attempt may be made to find two small plexuses of the sympathetic on the carotid artery, though in an injected body this dissection is scarcely possible. INTERNAL CAROTID ARTERY. 33 One of these (cavernous) is near the root of the anterior cHnoicl pro- cess ; and to bring it into view it will be necessary to cut off that piece of bone, and to dissect out with care the third, fourth, fifth, and sixth nerves, looking for filaments between them and the plexus. Another plexus (carotid), joining the fifth and sixth nerves, surrounds the artery as this enters the sinus. The INTERNAL CAROTID ARTERY appears in the base of the skull at the apex of the petrous part of the temporal bone. In its ascent to the brain the vessel lies in the space of the cavernous sinus, along the side of the body of the sphenoid bone, and makes two remarkable bends, so as to look like the letter S reclined. At first, the artery ascends to the posterior clinoid process ; it is then directed forwards to the root of the anterior process of the same name ; and lastly it turns upwards internal to this last point of bone, perforates the dura mater bounding the sinus, and divides into cerebral arteries at the base of the brain. In this course the artery is enveloped by nerves derived from the sympathetic in the neck. The branches of the artery here are few. In the sinus there are some small arteries (arteriai receptaculi) for the supply of the dura mater and the bone, the nerves, and the pituitary body ; and at the anterior clinoid process the ophthalmic branch arises. The terminal branches of the carotid will be seen in the dissection of the base of the brain. Sympathetic Nerve. Around the carotid artery is a prolongation of the sympathetic nerve of the neck, which forms the following plexuses : — The carotid plexus is situate on the outer side of the vessel, at its en- trance into the cavernous sinus, and communicates with the sixth nerve and the Gasserian ganglion. The small cai^ernous plexus is placed below the bend of the artery which is close to the anterior clinoid process, and is connected with that offset of the upper cervical ganglion which courses along the inner side of the carotid artery. Filaments from the plexus unite with the third, fourth, and ophthalmic nerves. One filament is also furnished to the lenticidar ganglion in the orbit, either separately from, or in conjunction with, the nasal nerve. After forming those plexuses, the nerves surround the trunk of the carotid, and are lost chiefly in the cerebral membrane named pia mater ; but some ascend on the cerebral and ophthalmic branches of that vessel, and one offset is said to enter the eyeball with the central artery of the retina. Petrosal nerves (fig. 34). Beneath the Gasserian ganglion is the large superjicial petrosal nerve (fig. 34,*^) entering the hiatus Fallojdi to join the facial nerve. Externally to this is occasionally seen another small petrosal nerve (fig. 34, *) (^external superficial)^ which springs from the symj)athetic on the middle meningeal artery, and enters the bone to join the facial nerve. A third, the small petrosal nerve (fig. 34, ^), is con- tained in the substance of the temporal bone. The source, and the desti- nation of those three small nerves will be afterwards learnt. It will suffice now for the student to note the two first, and to see that they are kept moist and fit for examination at a future time. Directions. Now the base of the skull has been completed, a preserva- tive fluid or salt should be applied, and the flaps of the teguments should be stitched together over all. 3 34 DISSECTION OF THE FACE, Section III. DISSECTION OF THE FACE. Directions. The left side of the face may be used for learning the mus- cles and vessels, and the right side is to be reserved for the nerves. Position. The previous position of the body for the examination of the base of the skull will require to be changed : — the head is to be lowered, and the side of the face to be dissected is to be placed upwards. Dissection. As a preparatory step, the muscular fibres of the apertures may be made slightly tense by inserting a small quantity of tow or cotton- wool between the eyelids and the eyeball, and between the lips and the teeth. First lay bare the sphincter muscle of the eyelids by a skin-deep circular incision over the margin of the orbit, and by raising the skin of the lids towards the aperture of the eye. Much care must be taken in detaching the skin from the thin and oftentimes pale fibres of the orbicular muscle in the lids, else they will be cut away in consequence of the little areolar tissue betAveen the two. Next the integument is to be removed from the side of the face by one incision in front of the ear, from above the zygomatic arch to the angle of the jaw, and then along the base of the jaw to the chin ; and by another cut carried backwards horizontally from the corner of the mouth into the first. The flaps of skin are to be raised from behind forwards, and left adherent along the middle line. On the side of the nose the skin is closely united to the subjacent parts, and must be detached with caution. Around the mouth are many fleshy slips extending both upwards and downwards from the orbicular muscle, but they are all marked so distinctly as to escape injury, with the exception of the small risorius muscle which goes from the corner of the mouth towards the ramus of the lower jaw. While removing the fat from the muscles, each fleshy slip may be made tense with hooks. The facial vessels and their branches will come into view as the muscles are cleaned; but the nerves may be disregarded on this side. In front of the ear is the parotid gland, whose duct is to be preserved ; this is on a level with the meatus auditorius, and pierces the middle of the cheek. Muscles of the Face (fig. 6). The superficial muscles of the face are gathered around the apertures of the nose, eye, and mouth. An orbi- cular or sphincter muscle encircles the apertures of the eye and mouth ; and other muscles are blended with each to enlarge the opening in the centre of the fibres. There are three distinct groups of muscles ; one of the eyelids ; another of the nostril ; and a third of the aperture of the mouth. One of the muscles of mastication, viz., the masseter, is seen between the jaws. Muscles of the Nose. These muscles are the following: pyra- midalis nasi, compressor naris, levator alae nasi, dilator naris, and depressor ahe nasi. The PYRAMiDALTS NASI (fig. 5, is a small fleshy slip that covers the nasal bone, and is continuous above with the occipito-frontalis muscle. Over the cartilaginous part of the nose its fibres end in an aponeurosis, MUSCLES OF NOSE. 85 which joins that of the compressor naris. Along its inner border is the muscle of the opposite side. Action. This muscle makes tight the skin over the nasal cartilages, but renders lax, and sometimes wrinkles transversely the skin towards the root of the nose. Compressor Naris. This muscle (fig. 5,^) is not well seen till after the examination of tlie following one. Triangular in shape, it arises by its apex from the canine fossa of the upper maxillary bone. The fibres are directed inwards, spreading out at the same time, and end in an aponeurosis, wliich covers the cartilaginous part of the nose, and joins the tendon of the opposite muscle. This muscle is partly concealed by the next — the common elevator of the ala of the nose and the upper lip. Action. It stretches the skin over the cartilaginous part of the nose. The LEVATOR LABii supERiORis AL^EQUE NASI (fig. 5,^) is placed by the side of the nose, and arises from the lop of the nasal process of the upper maxillary bone, internal to the attachment of the orbicularis. As the fibres descend from the inner part of the orbit the most internal are 1. Pyramidalis nasi.. 2. Common elevator of the nose and lip. 3. Compressor naris. 4 and 5. The two slips of the dilatator naii.s. 6. Depressor alse nasi. 7. Orbicularis oris, attached to the septum nasi. Fig. 5. Muscles of the Nose. attached by a narrow slip to the wing of the nose, whilst the rest are blended interiorly with the orbicularis oris. Near its origin the muscle is partly concealed by the orbicularis palpebrarum, but in the rest of its extent it is subcutaneous. Its outer border joins the elevator of the upper lip. Action. As the name expresses, it can raise the upper lip, and draw outwards the wing of the nose, dilating the aperture ; but when the mouth is shut it can enlarge the nostril independently of the lip. Dilatator Naris. In the dense tissue on the outer side of the nostril are a few muscular fibres, botli at the fore and back part of that aperture (fig. 0 , and ®), to which the above name has been given by Theile: they are seldom visible without a lens. The anterior slip, passes from the cartilage of the aperture to the integument of the margin of the nostril; and the posterior.^ °, arising from the upper jawbone and the small sesa- moid cartilages, ends also in the integuments of the nostril. 36 DISSECTION OF THE FACE. Action. The fibres enlarge the nasal opening by raising and everting the outer edge. The DEPRESSOR ala: nasi (tig. 5, will be seen if the upper lip is everted, and the mucous membrane is removed, from the side of the fraenum of the lip. It arises below the nose from a depression of the upper jaw- bone above the roots of the second incisor and canine teeth ; and ascends to be inserted into the septum nasi and the posterior part of the ala of the nose. Action. By drawing down and turning in the edge of the dilated nostril, it restores the aperture to its usual size. Muscles of the Eyelids. The muscles of the eyelids and eyebrow are four in number, viz., orbicularis palpebrarum, corrugator supercilii, levator palpebme superioris, and tensor tarsi d the two latter are dissected in the orbit, and will be described with it. The ORBICULARIS PALPEBRARUM (fig. 6, is the Sphincter muscle closing the opening between the eyelids. It is a flat and thin layer, which extends from the margin of the lids beyond the circumference of the orbit. From a difference in the characters of the fibres, a division has been made of them into two parts — outer and inner. The external fibres (orbital part), the best marked, are fixed only at one point, viz., the inner angle of the orbit. This attachment (origin) is connected with the surface and borders of the small tendo palpebrarum ; above that tendon with the nasal process of the upper maxillary, and the internal angular process of the frontal bone ; and below the tendon with the superior maxillary bone, and the margin of the orbit. From this origin the fibres are directed outwards, giving rise to ovals, which lie side by side, and increase in size towards the outer edge of the muscle where they project beyond the margin of the orbit. The internal fibres (palpebral part), paler and finer than the outer, occupy the eyelids, and are fixed at both the outer and inner angles of the orbit. Internally (origin) they are united with the tendo palpebrarum, and externally (insertion) with the external tarsal ligament and the malar bone, and some few may blend with the orbital part. Close to the cilia or eyelashes the fibres form a small pale bundle, which is sometimes called ciliary. The muscle is subcutaneous ; and its circumference is blended above with the occipito-frontalis. Beneath the upper half of the orbicularis, as it lies on the margin of the orbit, is the corrugator supercilii muscle with the supra-orbital vessels and nerve ; and beneath the lower half is part of the elevator of the upper lip. The outer fibres are joined occasionally by slips to other contiguous muscles below the orbit. Action. The inner fibres cause the lids to approach each other, shut- ting the eye ; and in forced contraction the outer commissure is drawn inwards. In closure of the eye the lids move unequally — the upper being much depressed, and the lower slightly elevated and moved horizontally inwards. When the outer fibres contract, the eyebrow is depressed, and the skin over the edge of the orbit is raised around the eye, so as to protect the ball. Elevation of the upper lip follows contraction of the outer part of the orbicularis, in consequence of fibres being prolonged to the levator labii superioris. • The tensor tarsi muscle (p. 59) is sometimes described as a part of the orbicu- laris. MUSCLES OF MOUTH. 37 The CORRUGATOR suPERCiLii is beneath the orbicularis, near the inner angle of the orbit. Its fibres arise from the inner part of the superciliary ridge of the frontal bone, and are directed outwards to join the orbicular muscle about the middle of the orbital arch. It is a short muscle, and is distinguished by the closeness of its fibres. Action. It draws inwards and downwards the mid-part of the eyebrow, wrinkling vertically the skin near the nose, and stretching that outside its point of insertion. Muscles of the Mouth. The muscles of the aperture of the mouth consist of a sphincter ; an elevator of the upper lip and angle of the mouth ; an elevator and depressor of the lower lip and angle of the mouth ; and retractors of tlie corner. Lastly, a wide muscle of the cheek closes the space between the jaws. Fig. 6. 1. Occipito-frontalis, anterior belly. 4. Posterior belly. 2. Orbicularis palpebrarum. 3. Levator labii superioris alasque nasi. 5. Compressor nasi. 6. Levator labii superioris. 7. Zygomaticus minor (too large). 8. Zygomaticus major. 9. Risorins. 10. Masseter. 11. Orbicularis oris. 12. Depressor labii inferioris. 13. Depressor anguli oris. 14. Buccinator. f Levator anguli oris. See fig. 1. The ORBICULARIS ORIS MUSCLE (fig. 6, surrounds the opening of the mouth, and is united with the several muscles acting on that aperture. It consists of two parts, inner and outer, which differ in the appearance and arrangement of the fibres, like the sphincter muscle of the eyelids. The inner part (fig. 5, ’^), whose fibres are pale in color and fine in texture, forms a rounded thick fasciculus, which corresponds with the red margin of the lip. The fibres of this portion of the muscle, unattached to bone, blend with the buccinator at the corner of the mouth, and some pass from lip to lip. The outer part is thin, wide, and more irregular in form, and is con- nected with the subjacent bone, besides its union with the adjacent muscles. In the upper lip it is attached, on each side of the middle line, by one slip (naso-labial) to the back of the sejitum of tlie nose (fig. 5, '^) ; and by a thin stratum to the outer surface of the upper jaw, opposite the canine tooth, and external to the depressor of the wing of the nose. In the 38 DISSECTION OF THE FACE. lower lip it is fixed on each side into the inferior jawbone, opposite the canine tooth, external to the levator labii inferioris muscle. To see these attachments the lip must be everted, and the mucous membrane carefully raised. The inner margin of the muscle is free, and bounds the aperture of the mouth ; whilst the outer edge blends with the different muscles that ele- vate or depress tlie lips and the angle of the mouth. Beneath the orbicu- laris in each lip is the coronary artery, with the mucous membrane and the labial glands. Action. Both parts of the muscle contracting, the lips are pressed to- gether and projected forwards, and the aperture of the mouth is diminished transversely by the approximation of the corners towards eacli other. The inner fibres acting alone will turn inwards the red part of the lip, and diminish the width of the buccal opening. The outer fibres press the lips against the dental arches, the free edges being protruded and somewhat everted. At the same time the centre part of the nose is depressed and the chin raised by means of the fleshy slips connected with those parts. The LEVATOR LABII suPERiORis (fig. 6, ®) extends vertically from the lower margin of tlie orbit to the orbicularis oris. It arises from tlie upper maxillary and malar bones above the infra-orbital foramen, and blends interiorly with the orbicularis oris. Near the orbit the muscle- is overlapped by the orbicularis palpebrarum, but below that spot it is sub- cutaneous. By its inner side it joins the common elevator of the ala of the nose and upper lip ; and to its outer side lie the zygomatic muscles, the small one joining it. Beneath it are the infra-orbital vessels and nerve. Action. By the action of this muscle the upper lip is raised, and the skin of the clieek is bulged below the eye. Tlie DEPRESSOR LABII INFERIORIS (fig. 6, is Opposite the elevator of the upper lip, and has much yellow fat mixed with its fibres. The muscle has a wide origin from a depression on the front of the lower jaw, reaching backwards from near the symphysis to a little beyond the hole for the labial vessels and nerve ; ascending thence it is united with the orbicularis in the lower lip. Its inner border joins the muscle of the oppo- site side above, and its outer is overlapped below by the depressor anguli oris. Action. If one muscle contracts, the half of the lip of the same side is depressed and everted ; but by the use of both muscles, the whole lip is lowered and turned outwards, and rendered tense at the centre. Tlie LEVATOR LABII INFERIORIS (levatoi* menti) is a small muscle on the side of the frienum of the lower lip, which is opposite the depressor of the ala of the nose in the upper lip. When the lip has been everted and the mucous membrane removed, the muscle will be seen to arise from a fossa near the symphysis of tlie lower jaw, and to descend to its insertion into the integument of the chin. Its position is internal to the depressor of the li[i and the attachment of the orbicularis. Action. It indents the skin of the chin opposite its insertion, and assists in raising the lower lip. The LEVATOR ANGULI ORIS (fig. G, f) has well-marked fibres, and is ])artly concealed by the levator labii superioris. Arising from the canine fossa beneath the infra-orbital foramen, its fibres spread out towards the angle of the mouth where they are superficial to the buccinator, and mix MUSCLES OF MOUTH. 39 with the rest of the muscles, but the greater number are continued into the depressor anguli oris and the lower lip. Action. This muscle elevates the corner of the mouth, and acts as an antagonist to the depressor. The DEPRESSOR ANGULI ORIS (fig. 6, is triangular in shape ; it arises from the oblique line on the outer surface of the lower jaw, and ascending to the angle of the mouth, its fibres are prolonged into the ele- vator of the angle. The muscle conceals the labial branch of the inferior dental vessels and nerve. At its origin the depressor is united with the platysma myoides, and near its insertion with the risorius muscle. Action. The angle of the mouth is drawn downwards and backwards by it, as is exemplified in a sorrowful countenance. The ZYGOMATIC MUSCLES (fig. 6) are directed obliquely from the arch of the same name towards the angle of the mouth and tlie upper lip. One is longer and larger than the other ; they are therefore named major and minor. The zygomaticus major, arises from the outer part of the malar bone, and is inserted into the angle of the mouth. The zygomaticus mhior, is attached to the malar bone anterior to the other, and blends with the fibres of the special elevator of the upper lip. Action. The large muscle inclines upwards and backwards tlie corner of the mouth ; and the small one assists the levator labii superioris in raising the upper lip. The RISORIUS MUSCLE (Santorini) (fig. 6,®) is a thin and narrow bun- dle of fibres, sometimes divided into two or more parts, which arises externally from the fascia over the masseter muscle, and is connected in- ternally with the apex of the depressor anguli oris. Action. The use of this muscle is indicated by its name, as it retracts the corner of the mouth in laughing. The BUCCINATOR (fig. 6, ^*) is the flat and thin muscle of the cheek, and occupies the interval between the jaws. The muscle arises from the outer surface of the alveolar borders of the upper and lower maxillje, as far forwards in each as the first molar tooth ; and in the interval betM^een the jaws behind it is attached to a band of fascia — the pterygo-maxillary ligament. From the origin the fibres are directed forwards to the angle of the mouth, where they mix with the other muscles and with both parts of the orbicularis ; and as some of the central fibres descend to the lower lip whilst others ascend to the upper lip, a decussation takes place at the corner of the mouth. On the cutaneous surface of the buccinator are the different muscles converging to the angle of the mouth ; and crossing the upper part is the duct of the parotid gland, which perforates the muscle opposite the second upper molar teeth. Internally the muscle is lined by the mucous membrane of the mouth, aad externally it is covered by a fascia (bucco- pharyngeal) that is continued to the pharynx. By its intermaxillary origin the buccinator corresponds with the attachment of the superior constrictor of the pharynx. Action. By one muscle the corner of the mouth is retracted, and the cheek wrinkled. By the action of both tlie aperture of the mouth is widened transversely. In mastication the cheek is pressed by the muscular contraction against the dental arches, when the corner of the mouth is fixed by the sphincter. In the expulsion of air from the mouth, as in whistling, the muscle is 40 DISSECTION OF THE FACE. contracted SO as to prevent bulging of the cheek; but in the use of a blow-pipe it is distended over the volume of air contained in the mouth, and drives out a continuous stream of air by its contraction. The VESSELS OF THE FACE (fig. 17) are the facial and transverse facial arteries with their accompanying veins. The arteries are branches of the external carotid; and the facial vein is received into the internal jugular trunk. The facial artery (fig. 17, jf), a branch of the carotid, emerges from the neck, and appears on the lower jaw anterior to the masseter muscle. From this point the artery ascends in a tortuous manner, near the angle of the mouth and the side of the nose, to the inner angle of the orbit, where it anastomoses with the ophthalmic artery. The course of the ves- sel is comparatively superficial in the mass of fat of the inner part of the cheek. At first it is concealed by the platysma whilst crossing the jaw, but this thin muscle does not prevent pulsation being recognized during life; and near the mouth the large zygomatic muscle is superficial tO it. The vessel rests successively on the lower jaw, buccinator muscle, ele- vator of the angle of the mouth, and elevator of the upper lip. Accom- panying the artery is the facial vein, which is nearly a straight tube, and lies to the outer side. Branches. From the outer side of the vessel unnamed branches are furnished to the muscles and integuments, some of which anastomose with the transverse facial artery. From the inner side are given the following branches : — Tlie inferior labial branch (f) runs inwards beneath the depressor anguli oris muscle, and is distributed between the lower lip and chin; it communicates with the inferior coronary, and with the labial branch of the inferior dental artery. Coronary branches {r and s). There is one for each lip (superior and inferior), whicli arise together or separately from the facial, and are di- rected inwards between the orbicular muscle and the mucous membrane of the lip, till they inosculate with the corresponding branches of the opposite side. From the arterial arches thus formed, offsets are supplied to the lips and labial glands. From the arch in the upper lip a branch is given to each side of the septum of the nose, — artery of the septum. The lateral nasal branch {p) arises opposite the ala nasi, and passes beneath the levator labii superioris alaeque nasi to the side of the nose, where it anastomoses with the internal nasal branch of the ophthalmic artery. The angular branch (o) is the terminal twig of the facial artery at the inner angle of the orbit, and joins with a branch (external nasal) of the ophthalmic artery. The facial vein commences at the root of the nose in a small vein named angular (p. 21). It then crosses over the elevator of the upper lip, and separating from the artery, courses beneath the large zygomatic mus- cle to the side of the jaw. Afterwards it has a short course in the neck to join the internal jugular vein. Branches. At the inner side of the orbit it receives veins from the lower eyC[\(\. (inferior palpebral)., from the side of the nose. Below the orbit it is joined by tlie infra-orbital vein, also by a large branch, anterior internal maxillary, tliat comes from the pterygoid region ; and thence to its termination by veins corresponding with the branches of the artery in the face and neck. PAROTID GLAND. 41 The transverse facial artery (fig. 17) is a branch of the temporal, and appears in the face at the anterior border of the parotid gland. It lies by the side of the parotid duct, with branches of the facial nerve, and dis- tributes offsets to the muscles and integuments; some branches anastomose with the facial artery. Dissection. The parotid gland in front of the ear may be next displayed. To see the gland, raise the skin from the surface towards the ear by means of a cut from the base of the jaw to the anterior border of the sterno-nrias- toid muscle ; this cut may be united with that made for the dissection of tlie posterior muscle of the ear. A strong fascia covers the gland, and is connected above and behind to the zygomatic arch and the cartilage of the ear, but is continued over the face in front; this is to be removed, so that the gland may be detached slightly from the parts around. The great auricular nerve will be seen ascending to the lobe of the ear; and one or two small glands rest on the surface of the parotid. The PAROTID (fig. 16, is the largest of the salivary glands. It occu- pies the space between the ear and the lower jaw, and is named from its position. Its excretory duct enters the mouth through the middle of the cheek. The shape of the gland is irregular, and is determined somewhat by the bounding parts. Thus inferiorly, where there is not any resisting struc- ture, the parotid projects into the neck, and comes into close proximity with the sub-maxillary gland, though separated from it by a process of the cervical fascia; a line from the angle of the jaw to the sterno-mastoid muscle marks usually the extent of the gland in this direction. Above, the parotid is limited by the zygomatic arch and the temporal bone. Along the posterior part the sterno-mastoid muscle extends ; but anteriorly the gland projects somewhat on the face, and in this direction a small accessory part, soda parotidis., is prolonged from it over the masseter. Connected with the anterior border is the excretory duct — duct of Sten- son {ductus Stenonisy fig. 17), which crosses tlie masseter below the soda parotidiSy and perforates the cheek obliquely opposite the second molar tooth of the upper jaw. The duct lies between the transverse facial artery and some branches of the facial nerve, the latter being below it. A line drawn from the meatus auditorius to a little below the nostril would mark the level of the duct in the face ; and the central point of the line would be opposite the opening into the mouth. The length of the duct is about two inches and a half; and its capacity is large enough to allow a small probe to pass, but the opening into the mouth is much less. The cutaneous surface of the parotid is smooth, and one or two lymphatic glands are seated on it ; but from the deep part processes are sent into the inequalities of the space between the jaw and tlie mastoid process. Dissection. By removing with caution the parotid gland, the hollows that it fills will come into view : at the same time the dissector will see the vessels and nerves that pass through it. An examination of the pro- cesses of the gland, and of the number of important vessels and nerves in relation with it, will demonstrate the dangers attending any operation on it. The duct may be opened, and a pin may be passed along it to the mouth, to show the diminished size of the aperture. Two large processes of the gland extend deeply into the neck. One dips behind the styloid process, and projects beneath the mastoid process and sterno-mastoid muscle, whilst it reaches also the deep vessels and nerves of the neck. The other piece is situate in front of the styloid 42 DISSECTION OF THE FACE. process ; it passes into the glenoid hollow behind the articulation of the lower jaw ; and sinks beneath the ramus of that bone along the internal maxillary artery. Passing through the middle of the gland is the external carotid artery, which ascends behind the ramus of the jaw, and furnishes the auricular, superficial tem])oral, and internal maxillary branches. Superficial to the artery lies the trunk formed by the junction of the temporal and internal maxillary veins, from which tlie external jugular vein springs ; and this common trunk, receiving some veins from the parotid, is connected with the internal jugular vein by a branch through the gland. ^ Crossing the gland from behind forwards is the trunk of the facial nerve, which passes over the artery, and distributes its branches through the parotid. The superficial temporal branch of the inferior maxillary nerves lies above the upper part of the glandular mass ; and offsets of the great auricular nerve pierce the gland at the lower part, and join the facial. The structure of the parotid resembles that of the other salivary glands. The glandular mass is divided into numerous small lobules by intervening processes of fascia ; and each lobule consists of a set of the fine closed sac- cular extremities of the excretory duct, which are lined by flattened and nucleated epitlielium, and surrounded by capillary vessels. These little sacs form by their aggregation the mass of each lobule. From the lobules issue small ducts, which unite to form larger tubes, and finally all the ducts of the gland are collected into one. The common duct (duct of Stenson) is composed of an external fibrous coat, consisting of white and elastic fibres ; and of an internal mucous coat which is clothed with columnar epithelium. Tlie parotid receives its arteries from the external carotid ; and its nerves from the sympathetic, auriculo-temporal of the fifth, facial, and great auri- cular. Its lymphatics join those of the neck. Two or three small molar glands lie along the origin of the buccinator, and open into the mouth near the last molar tooth by separate ducts. Cartilacies of the Nose (fig. 7). These close the anterior nasal aperture in the skeleton, and form part of the outer nose and the septum. Tliey are five in number, two on each side — lateral cartilage and cartilage of the aperture ; together with a central one, or the cartilage of the septum of the nose. Only the lateral cartilages are seen in this stage of the dis-. section. Dissection. The lateral cartilages will be seen when the muscular and fibrous structure of the left side of the nose, and the skin of the lower part of the nostril of the same side, have been taken away. By turning aside the lateral cartilages the septal one will appear in the middle line. The upper lateral cartilage (fig. 7, ‘^) is flattened, and is somewhat triangular in form. Posteriorly it is attached to the nasal and upper maxillary bones ; and anteriorly it meets the one of the opposite side for a short distance above, but the two are separated below by an interval, in which the cartilage of the septum appears. Interiorly the lateral cartilage • Oftentimes tliere is a different arrangement of these veins. In such case the external jugular is continued from the occipital (half or all) and posterior auri- cular veins ; whilst the temporal and internal maxillary veins unite to form a trunk (tempo-maxillary), which receives the facial below the jaw, and opens into the internal jugular vein opposite the upper border of the thyroid cartilage. When this condition exists, the temporo-maxillary vein accompanies the external carotid artery. APPENDAGES OF EYE. 43 is contiguous to the cartilage of the aperture, and is connected to it by fibrous tissue. The cartilage of the aperture (fig. 7) forms a ring around the opening of the nose except behind. It lias not any attachment directly to bone ; but it is united above to the lateral cartilage by fibrous tissue, and below with the dense teguments forming the margin of the aperture of the nostril. Fig. 7. 1. Triangular septal cartilage. 2. Upper latei-al cartilage. 3. Lower lateral, or the cartilage of the aperture, the outer part. 4. Inner part of the cartilage of the aperture. 5. Nasal bone. Lateral Cartilages of the Nose. The part of the cartilage (f) which bounds the opening externally, is narrow and pointed behind, where it ends in two or three small pieces of cartilage — cartilagines minores vel sesamoidece ; but swells out in front where it touches its fellow, and forms the apex of the nose. The inner part {*) projects backwards along the septum of the nose nearly to the superior maxillary bone; it assists in the formation of the par- tition between the nostrils, and extends below the level of the septum nasi. The Appendages of the Eye include the eyebrow, the eyelid, and the lachrymal apparatus. Some of these can be examined now on the opposite side of the face. The apparatus for the tears will be dissected after the orbit has been completed. The eyebrow (supercilium) is a curved eminence just above the eye, which is placed over the orbital arch of the frontal bone. It consists of thickened integuments, and its prominence is in part due to the subjacent orbicularis palpebrarum. It is furnished with long coarse hairs, which are directed outwards, and towards one another. The eyelids are two movable semilunar parts in front of the eye, which can be approached or separated over the eyeball. The u|)per lid is the largest and the most movable, and descends below the middle of the eye- ball when the two meet ; it is also provided with a special muscle to raise it. The interval between the open lids is named Jissura palpebrarum. Externally and internally they are united by a commissure or cantkus. Tlie free margin is thicker than the rest of the lid, and is semilunar in form ; but towards tlie inner side, about a quarter of an inch from the commissure, it becomes straighter. At the spot where the two parts join is a small white eminence (fig. 13, ihe papilla lachrymalis ; and in this is the punctum lachrymale, or the opening of the canal for the tears. This margin is provided anteriorly with the eyelashes, and near tlie posterior edge with a row of small openings of the Meibomian glands ; but both the cilia and the glands are absent from the part of the lid which is internal to the opening of the punctum lachrymale. The free margin 44 DISSECTION OF THE FACE. of each lid is sharp at the anterior edge where it touches its fellow ; but is sloped at the ])osterior, so as to leave an interval between it and the eye- ball for the passage inwards of fluid. The eyelashes (cilia) are two or more rows of curved hairs, which are fixed into the anterior edge of the free border of the lid ; they are largest in the upper lid, and diminish in length from the centre towards the sides. The cilia are convex towards one another, and cross when the lids are shut. The Structure of the Eyelids. Each lid consists fundamentally of a piece of cartilage attached to the bone by ligaments. Superficial to this framework are the integuments with a layer of fibres of the orbicularis palpebrarum, and beneath it the mucous lining of the conjunctiva. The upper lid includes also the tendon of the levator palpebras. Vessels and nerves are contained in the lids. Dissection. The student may learn the structure of the lids on the left side, on which the muscles are dissected. The bit of tow or wool may remain beneath the lids; and the palpebral part of the orbicularis muscle is to be thrown inwards by an incision around the margin of the orbit. In raising the muscle care must be taken of the thin membranous palpe- bral ligament beneath, and of the vessels and nerves of the lid. Orbicularis palpebrarum. The palpebral fibres of this muscle form a pale layer which reaches the free edge of the eyelids (p. 3G). A thin stratum of areolar tissue without fat unites the muscle with the skin. The palpebral ligament is a stratum of fibrous membrane, which is continued from the margin of the orbit to join the lower or free edge of each tarsal cartilage. At the inner part of the orbit the ligament is thin and loose, but at the outer part it is somewhat thicker and stronger. The tarsal cartilages., one for each eyelid, are elongated transversely, and give strength to the lids. Each is fixed internally by the ligament of the eyelids, and externally by a fibrous band — external tarsal ligament., to the outer part of the orbit. The margin corresponding with the edge •of the lid is free, and thicker than the rest of the cartilage. On the inner surface each cartilage is lined by the mucous membrane or conjunc- tiva. The cartilages are not alike in the two lids. In the upper eyelid, where the cartilage is largest, it is crescentic in shape, and is about half an inch wide in the centre; and to its fore part the tendon of the levator palpebrte is attached. In the lower lid the cartilage is a narrow band, about two lines broad, with borders nearly straight. Ligament of the eyelids (tendo palpebrarum, internal tarsal ligament) is a small fibrous band at the inner part of the orbit, which serves to fix the lids, and is attached to the anterior margin of the lachrymal groove in the upper jaw. It is about a quarter of an inch long, and divides into two processes, which are united with the tarsal cartilages, one to each. This ligament crosses the lachrymal sac, to which it gives a fibrous expan- sion ; and the fleshy fibres of the orbicularis palpebrarum arise from it. The Meibomian glands or follicles are placed in grooves on the ocular surface of the tarsal cartilages. They extend, parallel to one another, from the thick towards the op[)Osite margin of the cartilage ; and their number is about thirty in the up[)er, and twenty in the lower lid. Tlie apertures of the glands 0 [)en in a line on the free border of the lid near the pos- terior edge. Each gland is a small yellowish tube, closed at one end, and having AUFJCLE OF THE EAR. 45 minute lateral caecal appendaf^es connected with it. Each contains a seba- ceous secretion, and is lined by flattened epithelium. If the palpebral ligament be cut through in the upper lid, the tendon of the levator palpehrce will be seen to be inserted into the fore part of the tarsal cartilage by a wide aponeurotic expansion. The conjunctiva^ or the mucous membrane, lines the interior of the eyelids, and covers the anterior part of the ball of the eye. Inside the lids it is inseparably united to the tarsal cartilages, and has numerous fine papillae. At the free margin of the lid this membrane joins the common integuments. Through the lachrymal canals and sac it is continuous with the pituitary membrane of the nose. At the inner commissure of the eyelids the conjunctiva forms a promi- nent and fleshy-looking body — caruncula lachrymalis (fig. 13, ^), which contains a group of mucous follicles, and has a few minute hairs on its surface. External to the caruncle is a small vertical fold of the mucous membrane — plica semilunaris ; this extends to the ball of the eye, and represents the membrana nictitans of birds. Bloodvessels of the eyelids. The arteries of the eyelids are furnished by the ophthalmic artery, and come from the palpebral and lachrymal branches : — The paJpehral arteries, one for each eyelid, run outwards from the inner canthus, lying between the tarsal cartilage and the tendon of the special elevator in the upper lid, and between the cartilage and the palpebral liga- ment in the lower lid ; and they anastomose externally with the lachrymal artery. From the arch that each forms, branches are distributed to the eyelids. The lachrymal artery furnishes an offset to each lid to form arches with the palpebral arteries, and then perforates the palpebral ligament at the outer part of the orbit to end in the upper lid. The veins of the lids open into the frontal and angular veins at the root of the nose (pp. 21, 40). The nerves of the eyelids are supplied from the ophthalmic and facial nerves. The branches of the ophthalmic nerve (of the fifth) which give offsets to the upper lid, are the following : lachrymal, near the outer part ; supra- orhitcd, about the middle ; and supra-trochlear and infra-trochlear at the inner side ([)p. 42, o4). In the lower eyelid, about its middle, is palpe- bral branch of the superior maxillary trunk of the fifth nerve. Branches of the facial nerve (p. 48) enter both lids at the outer part, and supply the orbicularis muscle ; they communicate with the offsets of the fifth nerve. External Ear. The outer ear consists of a trumpet-shaped structure, named pinna or auricle, which receives the undulations of the air ; and of a tube — meatus auditorius, which conveys them to the inner ear. The pinna may be examined on the left side of the head ; but the anatomy of the meatus will be described with the ear. The pinna, or auricle., is an uneven piece of yellow fibro-cartilage, which is covered with integument, and is fixed to the margin of the meatus auditorius extern us. It is of an oval form, with the margin folded and the larger end placed upwards. The surface next the head is generally convex ; but the opposite is ex- cavated, and presents the undermentioned elevations and depressions. In the centre is a deep hollow named concha, which is wide above but narrow 46 DISSECTION OF THE FACE. below ; it conducts to the meatus auditorius. In front of the narrowed i)art of the hollow is a projection of a triangular shape — the tragus, which has some hairs on the under surface ; and on the opposite side of the same narrow end, rather below the level of the tragus, is placed another projec- tion — the antitragus. The round rim-like margin of the ear, which extends into the concha, is called the helix; and the depression internal to it is the groove oy fossa, of the helix. Within the helix, between it and the concha, is the large Fig. 8. Muscles on the Outer Surface of the Ear Cartilaoe. 1. Muscles of the tragus. 3. Large muscle of the helix. 2. Muscles of the autitragus. 4. Small muscle of the helix. Muscles on the Inner Surface of the Ear Cartilage 6. Transverse muscle. 7. Oblique muscle (Tod) sometimes seen. eminence of the antihelix, which presents at its upper part a well-marked depression, the fossa of the antihelix. Interiorly the external ear is terminated by a soft pendulous part, the lobule. The special muscles of the pinna, which extend from one part of the cartilage to another, are very thin and pale. Five small muscles are to be recognized ; and these receive their names for the most part from the several eminences of the external ear. Dissection. In seeking the small auricular muscles, let the integuments be removed only over the spot where each muscle is said to be placed. A sharp knife and a good light are necessary lor the display of the muscular tihres. Occasionally the dissector will not find one or more of the number described below. The muscle of the tragus (fig. 8, is always found on the external aspect of the process from whicli it takes its name. The fibres are short, oblique, or transverse, and extend from the outer to the inner part of tlie tragus. Tlie muscle of the antitragus (fig. 8, is the best marked of all. It arises from the outer part of tlie autitragus, and the fibres are directed upwards to be inserted into the pointed extremity of the antihelix. The small muscle of the helix (fig. 8, *) is often indistinct or absent. It is placed on tlie part of the rim of the ear that extends into the concha. The large muscle of the helix (fig. 8, arises above the small muscle CARTILAGE OF AURICLE. 47 of the same part, and is inserted into the front of the helix, where this is about to curve backwards. It is usually present. The transverse muscle of the auricle (fig. 8, ®) forms a wide layer, which is situate at the back of the ear in the depression between the helix and the convexity of the concha. It arises from the convexity of the carti- lage forming the concha, and is inserted into the back of the helix. The muscle is mixed with much fibrous tissue, but it is well seen when that tissue is removed. Actions. These muscles are said to alter slightly the condition of the outer ear ; the muscles of the helix assisting, and those of the tragus and antitragus retarding the passage of sonorous undulations to the meatus. Dissection. The pinna may now be detached by cutting it close to the bone. When the integuments are entirely taken off', the cartilage of the pinna will be apparent ; but in removing the integuments, the lobule of the ear, which consists only of skin and fat, will disappear as in fig. 8. The cartilage of the pinna (fig. 8) resembles much the external ear in form, and presents nearly the same parts. The rim of the helix subsides posteriorly in the antihelix about the middle of the })inna ; whilst ante- riorly a small process projects from it, and there is a fissure near the pro- jection. The antihelix is divided about two-thirds down into two pieces ; one of these is pointed, and is joined by the helix, the other is continued into the antitragus. On the posterior aspect of the concha is a strong vertical process of cartilage. Interiorly the cartilage is fixed to the margin of the external auditory aperture in the temporal bone, and forms part of the meatus auditorius ; but it does not give rise to a complete tube, for at the upper and outer part the canal is closed by fibrous tissue. In the piece of cartilage forming the under part of the meatus are two fissures (Santorini), one is at the base of the tragus, the other passes from before backwards. Some ligaments connect the pinna with the head, but others pass from one point of the cartilage to another. The external ligaments are condensed bands of fibrous tissue, and are two in number, anterior and posterior. The anterior fixes the fore part of the helix to the root of the zygoma. The posterior passes from the back of the concha to the mastoid process. The chief special ligament crosses the interval between the tragus and the beginning of the helix, and completes the tube of the meatus. The FACIAL NERVE (portio dura, fig. 9), or the seventh cranial nerve, confers contractility on the muscles of the face. Numerous communica- tions take place between it and the fifth nerve ; the chief of these are found above and below the orbit, and over the body of the lower jaw. Dissection. The facial nerve is to be displayed on the right side of the face if there is time sufficient before the body is turned, otherwise it is to be omitted for the present (see p. 17). Some of the nerve is concealed by the })arotid gland, but the greater part is anterior to the glandular mass. To expose the ramification of the nerve beyond the parotid gland, let the skin be raised from the face in the same manner as on the left side. The different branches are then to be sought as they escape from beneath the anterior border of the gland, and are to be followed forwards to their termination. The highest branches to the temple have been already partly dissected above the zygomatic arch ; and their junctions with the temporal branch 48 DISSECTION OF THE FACE. of the superior maxillary and with the supra-orbital nerve have been seen. Other still smaller branches are to be traced to the outer part of the orbit, where they enter the eyelids and communicate with tlie other nerves in the lids ; as these cross the malar bone, a junction is to be found with the subcutaneous malar nerve of the fifth. With the duct of the parotid are two or more large branches, which are to be followed below the orbit to their junction with the infra-orbital, nasal, and infra-trochlear nerves. The remaining branches to the lower part of the face are smaller in size. One joins with the buccal nerve at the lower part of the buccinator muscle ; and one or two others are to be traced forwards to the lower lip, and to the labial branch of the inferior dental nerve. To follow backwards the trunk of the nerve through the gland, the in- teguments should be taken from the surface of the parotid as on the other side, and the gland should be removed piece by piece. In this proceeding the small branches of communication of the great auricular nerve with offsets of the facial, and the deep branches from the facial to the auriculo- temporal nerve, are to be sought. Lastly, the first small branches of the facial to the ear and the digastric and stylo-hyoid muscles, are to be looked for close to the base of the skull before the nerve enters the parotid. The Nerve outside the Skull (fig. 9, The nerve issues from the stylo-mastoid foramen, after traversing the aqueduct of Fallopius, and furnishes immediately the three following small branches : — The posterior auricular branch (fig. 9, *) turns upwards in front of the mastoid process, where it communicates with an offset of the great auricu- lar, and is said to be joined by a branch to the ear from the pneumogastric (cranial) nerve ; it ends in auricular and mastoid offsets (p. 23). The branch to the digastric muscle generally arises in common with the next. It is distributed by many offsets to the posterior belly of the mus- cle near the skull. The branch to the stylo-hyoideus is a long slender nerve, which is directed inwards and enters its muscle about the middle. This branch communicates with the sympathetic nerve on the external carotid artery. As soon as the facial nerve has given oft* those branches, it is directed forwards through the gland, and divides near the ramus of the jaw into two large trunks — temporo-facial and cervico-facial. The TEMPORO-FACIAL TRUNK fumislies offsets to the side of the head and face, whose ramifications extend as low as the meatus auditorius. As this trunk crosses over the external carotid artery, it sends downwards branches to join the auriculo-temporal portion of the inferior maxillary nerve ; and in front of the ear it gives some filaments to the tragus of the pinna. Three sets of terminal branches, temporal, malar, and infra-orbi- tal, are derived from the temporo-facial part. The temporal branches ascend obliquely over the zygomatic arch to enter the orbicular muscle, the corrugator supercilii, and the anterior belly of tlie occipito-frontalis ; they are united with offsets of the supra-orbital nerve (®). The attraliens aurem muscle receives a branch from this set ; and a junction takes place above the zygoma with the temporal branch of the superior maxillary nerve (^°). The malar branches are directed to the outer angle of the orbit, and are distributed to the orbicularis muscle. In the eyelids communications take place with the palpebral filaments of the fifth nerve ; and near the FACIAL NERVE. 49 outer part of the orbit, with the small subcutaneous malar branch of the superior maxillary nerve (®). The infra-orhital branches are longer than tlie rest, and are furnished to the muscles and the integument between the eye and mouth. Close to the orbit, and beneath the elevator of tlie upper lip, a remarkable commu- nication — infra-orhital plexus^ is formed between these nerves and the Fig. 9. Cutaneous Branches of the Fifth Nerve in the Face. 7. Nasal nerve. 8. Tnfra-trochlear. 9. Subcutaneous malar. 11. Infra-orbital. 12. Buccal. 13. Labial of inferior dental. 15. Facial or seventh cranial, sending back the posterior auricular branch, 4, and forwards its numerous ofi'sets to join the branches of the fifth nerve above enumerated. infra-orbital branches of the superior maxillary (^^). After crossing the branches of the fifth nerve, some small offsets of the facial nerve pass in- wards to the side of the nose, and others upwards to the inner angle of the orbit, to supply the muscles, and to join the nasal (’') and infra-trochlear (®) branches of the ophthalmic nerve. 4 50 DISSECTION OF THE ORBIT. The CERVico-FACiAL is Smaller than the other trunk, and distributes nerves to the lower part of the face and the upper part of the neck. Its highest branches join the lowest offsets of the temporo-facial nerve, and tlius complete the network on the face. This trunk, whilst in the parotid, gives twigs to the gland, and is united with the great auricular nerve. The terminal branches distributed from it are, buccal, supra-maxillaiy, and infra-maxillary. The hnccal branches pass forwards towards the angle of the mouth, giving offsets to the buccinator muscle, and terminate in the orbicularis oris. On the buccinator they join the branch of the inferior maxillary nerve to that muscle. The supra-maxillary branches course inwards above the base of the lower jaw to the middle line of the chin, and supply the muscles and the integument between the chin and mouth. Beneath the depressor anguli oris the branches of the facial join offsets of the labial branch of the in- ferior dental nerve (’®) in their course to the middle line. The infra-maxillary branches lie below the jaw, and are distributed to the upper part of the neck. The anatomy of these nerves will be given with the dissection of the anterior triangle of the neck. Section IV. DISSECTION OF THE ORBIT. Directions. The orbit should be learnt on that side on which the mus- cles of the face have been seen. Position. In the examination of the cavity the head is to be placed in the same position as for the dissection of the sinuses of the base of the skull. Dissection. For the display of the contents of the orbit, it will be neces- sary to take away the cotton wool from beneath the eyelids. To remove the bones forming the roof of the space, two cuts may be made with a saw through the margin of the orbit, one being placed at the outer, the other near the inner angle of the cavity ; and these should be continued back- ward with a chisel, along the roof of the orbit, so as to meet near the optic foramen. Tlie piece of bone included in the incisions is now to be tilted forwards, but is not to be taken away. Afterwards the rest of the roof of the orbit, which is formed by the small wing of the sphenoid bone, is to be cut away with the bone forceps, except a narrow ring around the optic foramen ; and any overhanging bone on the outer side, which may interfere with the dissection, may be likewise removed. During the examination of the cavity the eye is to be })ulled gently forwards. The periosteum of the orbit, which has been detached from the bone in the dissection, surrounds tlie contents of the orbital cavity, and joins the dura mater of the brain through tlie sphenoidal fissure. It encases the contents of the orbit like a sac, and adheres but loosely to the bones. Apertures exist posteriorly in the membrane for the entrance of the dif- ferent nerves and vessels ; and laterally prolongations of the periosteum jiccompany the vessels and nerves leaving the cavity. OPHTHALMIC NERVE. 51 Dissection. The periosteum is next to be divided along the middle of the orbit, and to be taken away. After the removal of a little fat, the following nerves, vessels, and muscles come into view ; but it is not need- ful to remove much of the fat in this stage of the dissection. The frontal nerve and the supra-orbital vessels lie in the centre ; the lachrymal nerve and vessels close to the outer wall ; and the small fourth nerve at the back of the orbit : all these nerves enter the cavity above the muscles. The superior oblique muscle is recognized by the fourth nerve entering it : the levator palpebraB and superior rectus lie beneath the frontal nerve ; and the external rectus is partly seen below the lachrymal nerve. In the outer part of the orbit, near the front, is the lachrymal gland. The frontal and lachrymal nerves should be followed forwards to their exit from the orbit, and backwards with the fourth nerve, through the sphenoidal fissure, to the wall of the cavernous sinus. In tracing them back, it will be expedient to remove the projecting clinoid process, should this still remain ; and some care will be required to follow the lachrymal nerve to its commencement. Contents of the orbit. The eyeball and the lachrymal gland, and a great quantity of granular fat, are lodged in the orbit. Connected with the eye are six muscles — four straight and two oblique ; and there is also an ele- vator of the upper eyelid in the cavity. The nerves in this small space are numerous, viz., the second, third, fourth, ophthalmic of the fifth, and the sixth nerve, together with the small temporo-malar branch of the superior maxillary nerve, and offsets of the sympathetic ; their general distribution is as follows : — The second nerve penetrates the eyeball ; the third is furnished to all the muscles of the cavity but two ; the fourth enters the superior oblique (one of the two ex- cepted); and the sixth is spent in the external rectus muscle. The fifth nerve supplies some filaments to tlie eyeball with the sympathetic, but the greater number of its branches pass through the orbital cavity to the face. The ophthalmic vessels are also contained in the orbit. The lachryynal gland (fig. 10, f) secretes the tears, and is situate in the hollow on the inner side of the external angular process of the frontal bone. It is of a lengthened form, something like an almond, and lies across the eye. From its anterior part a thin accessory piece projects be- neath the upper eyelid. The upper surface is convex, and in contact with the periosteum, to which it is connected by fibrous bands that constitute a ligament for the gland ; the lower surface rests on the eyeball and the external rectus muscle. In structure the lachrymal resembles the salivary glands ; and its very fine ducts, from eight to twelve in number, open by as many apertures in a semicircular line on the inner aspect of the upper eyelid towards the outer canthus. The FOURTH NERVE (fig. 10, is the most internal of the three nerves entering the orbit above the muscles. After reaching this space, it is directed inwards to the superior oblique muscle, which it pierces at the orbital surface, contrary to the general mode of distribution of the nerves on the ocular surface of the muscles. The OPHTHALMIC TRUNK of the fifth nerve (fig. 10, p. 52), as it ap- proaches the sphenoidal fissure, furnishes from its inner side the nasal branch, and then divides into the frontal and lachrymal branches ; the 52 DISSECTION OF THE ORBIT. former passes into the orbit between the heads of the external rectus, but the otlier two lie, as before said, above the muscles. The frontal nerve (fig. 10, is close to the outer side of the fourth as it enters the orbit, and is much larger than the lachrymal branch. In its course to the forehead the nerve lies along the middle of the orbit, and supplying anteriorly a supra-trochlear branch (4), leaves that cavity by the supra-orbital notch. Taking the name supra-orbital, it ascends on the forehead, and supplies the external part of the head (p. 21). Fig. 10. Whilst in the notch the nerve gives palpebral filaments to the upper lid. The supra-trochlear branch {f passes inwards above the pulley of the upper oblique muscle, and leaves the orbit to end in the eyelid and fore- head (p. 23). Before the nerve turns round the margin of the frontal bone, it sends downwards a branch of communication to the infra-trochlear branch of the nasal nerve. Frequently there are two supra-trochlear branches ; in such instances one arises near the back of the orbit. Tlie lachrymal nerve (fig. 10, after entering the orbit in a separate tube of the dura mater, is directed forwards in the outer part of the cavity, and beneath the lachrymal gland to tlie upper eyelid, where it pierces tlie pal])ebral ligament, and is distributed to the structure of the lid. The nerve furnishes branches to the lachrymal gland ; and near the gland it sends downwards one or two small filaments if) to communicate with the temporo-malar or orbital branch of the superior maxillary nerve. SUPERIOR OBLIQUE MUSCLE. 53 Occasionally it has a communicating filament behind with the fourth nerve. The nasal nerve is not visible at this stage of the dissection : it will be noticed afterwards at p. 43. Dissection. Divide the frontal nerve about its middle, and throw the ends forwards and backwards : by raising the posterior part of the nerve, the separate origin of the nasal branch from the ophthalmic trunk will appear. The lachrymal nerve may remain uncut. The LEVATOR PALPEBR^ suPERiORis (fig. 10, b) IS the most Superfi- cial muscle, and is attached posteriorly to the roof of the orbit in front of the optic foramen. The muscle widens in front, and bends downwards in the eyelid to be inserted by a wide tendon into the fore part of the tarsal cartilage. By one surface the muscle is in contact with the frontal nerve and the periosteum ; and by the other, with the superior rectus muscle. If it is cut across about the centre a small branch of the third nerve will be seen entering the posterior half at the under surface. Action. The lid-cartilage is made to glide upwards over the ball by this muscle, so that the upper edge is directed back and the lower forwards, the teguments of the lid being bent inwards at the same time. If the eye- ball is directed down, the movement of the lid is less free, because the conjunctiva is put on the stretch. The RECTUS SUPERIOR (fig. 10, is the upper of four muscles that lie arouud the globe of the eye. It arises from the upper part of the optic foramen, and is connected with the other recti muscles around the optic nerve. In front the fleshy fibres end in a tendon, which is inserted^ like the other recti, into the sclerotic coat of the eyeball about a quarter of an inch behind the transparent cornea. The under surface of the muscle is in contact with the globe of the eye, and with some vessels and nerves to be afterwards seen ; the other surface is covered by the preceding muscle. The action of the muscle will be given with the other recti (p. 57). The SUPERIOR OBLIQUE MUSCLE (fig. 10, is thin and narrow, and passes through a fibrous loop at the inner angle of the orbit before reach- ing the eyeball. The muscle arises behind from the inner part of the optic foramen, and ends anteriorly in a rounded tendon, which, after pass- ing through the loop before referred to (fig. 11) is reflected backwards and outwards between the superior rectus and the globe of the eye, and is in- serted into the sclerotic coat behind the middle of the ball. The fourth nerve is supplied to the orbital surface of the muscle, and the nasal nerve lies below it. The thin insertion of the muscle lies between the superior and the external rectus, and near the tendon of the inferior oblique. The 'pulley^ or trochlea (fig. 11), is a fibro-cartilaginous ring nearly a quarter of an inch wide, which is attached by fibrous tissue to the depres- sion of the frontal bone at the inner angle of the orbit. A fibrous layer is prolonged from the margins of the pulley on the tendon ; and a synovial membrane lines the ring, to facilitate the movement of the tendon through it. To see the synovial membrane and the motion of the tendon, this pro- longation must be cut away. • h^or the use of the muscle, see the description of the inferior oblique, p. 59. 54 DIHSECTION OF THE ORBIT. Dissection. The superior rectus muscle is next to be divided about the middle, and turned backwards (fig. 11), when a branch of the third nerve to its under surface will be found. At the same time the nasal nerve and the ophthalmic artery and vein will come into view as they cross inwards above the optic nerve : these should be traced forwards to the inner angle, and backwards to the posterior part of the orbit. By taking away the fat between the optic nerve and the external rectus, at the back of tlie orbit, the student will find easily fine nerve-threads (ciliary) with small arteries lying along the side of the optic nerve ; and by tracing the ciliary nerves backwards, they will guide to the small len- ticular ganglion (the size of a pin’s head) and its branches. The dissector should find then two branches from the nasal and tliird nerves to the ganglion : the nasal branch is slender, and enters tlie ganglion behind, and that of the third nerve, short and thick, joins the lower part. Lastly, the student should separate from one another the nasal, third, and sixth nerves, as they pass between the heads of the external rectus muscle into the orbit. The THIRD NERVE is placed liighest in the wall of the cavernous sinus (fig. 4, ^) ; but at the sphenoidal fissure it descends bf'low the fourth, and the two superficial branches (frontal and lachrymal) of the ophthalmic nerve. It comes into the orbit between the heads of the outer rectus, having previously divided into two parts. The upper piece (fig. 11, ®), the smallest in size, ends in the under sur- face of the levator palpebne and superior rectus muscles. The ioiver piece supplies some of the other muscles, and will be dissected afterwards (p. 57). The nasal branch of the ophthalmic nerve (fig. 11,^) enters the orbit between the heads of the rectus, lying between the two parts of the third nerve. In the orbit the nerve is directed obliquely inwards to reach the anterior of the two foramina in the inner wall. Passing through this aperture with the anterior ethmoidal (nasal) artery, the nerve appears in the cranium at the outer margin of the cribriform plate of the ethmoid bone. Finally, it enters the nasal cavity by an aperture at the front of the cribriform plate : and after passing behind the nasal bone, it is directed outwards between that bone and the cartilage, to end on the outer side of the nose. In the orbit the nasal crosses over the optic nerve, but beneath the superior rectus and levator jialpebrse muscles, and lies afterwards below the superior oblique ; in this part of its course it furnishes the following branches : — The branch to the lenticular ganglion (®) is about half an inch long and very slender, and arises as soon as the nerve comes into tlie orbit : this is the long root of the lenticular ganglion. Long ciliary branches. As the nasal crosses the optic nerve, it supplies two or more ciliary branches (fig. 11) to the eyeball. These lie on the inner side of the optic, and join the ciliary branches of the lenticular ganglion. The infra-trochlear branch (‘^) arises as the nasal nerve is about to leave the cavity, and is directed forwards below the pulley of the superior oblique muscle, to end in the upper eyelid, the conjunctiva, and the side of the nose. Before this branch leaves the orbit it receives an offset of commu- nication from the supra-trochlear nerve. In the nose (fig. 34). Whilst in the nasal cavity the nerve furnishes OPHTHALMIC ARTERY. 55 branches to the lining membrane of the septum narium and outer wall ; tliese will be subsequently referred to with the nose. Fig. 11. Second View of the Orbit (Illustrations of Dissections). Muscles : n. Superior oblique. h. Levator palpebne and upper rectus tlirown back together. c. External rectus. d. Fore part of upper rectus. /. Lachrymal gland. Nerves : 1. Nasal nerve beginning outside of the orbit. 2 Its infra-trochlear branch. 3. Lenticular ganglion . — 4. Its branch to the third nerve ; 5. Its branch to the nasal nerve (too large). 6. Branch of third to inferior oblique muscle, 7. Ciliary branches of the nasal nerve. 8. Upper branch of the third. P. Sixth nerve. 10. Third nerve, outside the orbit. Termination of the nasal nerve (fig. 9). After the nerve becomes cutaneous on the side of the nose, as seen in the dissection of the facial nerve (p. 47), it descends beneath the compressor naris muscle, and ends in the integuments of the wing and tip of the nose. The OPHTHALMIC or lenticular ganglion of the sympathetic nerve (fig. 11, is a small round body, of the size of a pin’s head, and of a slight red color. It is placed at the back of the orbit between the optic nerve and the external rectus, and commonly on the outer side of, and close to the ophthalmic artery. By its posterior part the ganglion has branches of communication with other nerves (its roots) ; and from the anterior part proceed the ciliary nerves to the eyeball. The ganglion communicates with sensory, motory, and symf athetic nerves. The offsets of communication are tliree in number. One, the lon^ root (®), is the branch of the nasal nerve before noticed, which joins the 56 DISSECTION OF THE ORBIT. superior angle. A second branch of considerable thickness {short root passes from the inferior angle to join the branch of the third nerve that supplies the inferior oblique muscle. And the third root is derived from the sympathetic (the cavernous plexus), either in union with the long root, or as a distinct branch to the posterior border of the ganglion. Branches. The short ciliary nerves (fig. 11) are ten or twelve in number, and are collected into two bundles, which leave the upper and lower angles of the front of the ganglion. In the upper bundle are four or five, and in the lower, six or seven nerves. As they extend along the optic nerve to the eyeball they occupy the outer and under parts, and com- municate with the long ciliary branches of the nasal nerve. The OPHTHALMIC ARTERY, a branch of the internal carotid, is trans- mitted into the orbit through the optic foramen. At first the vessel is outside the optic nerve, but it then courses inwards, over or under the nerve, to the inner angle of the orbit, where it ends in a nasal branch (external) on the side of the nose (fig. 17, ”), and anastomoses with the angular and nasal branches of the facial. Tlie branches of the artery are numerous, though inconsiderable in size, and may be arranged in three sets : — one arising outside the optic nerve, another above it, and a third set on the inner side. The lachrymal artery accompanies the nerve of the same name to the upper eyelid, where it ends by supplying that part, and anastomosing with the palpebral arches. It supplies branches, like the nerve, to the lachry- mal gland and the conjunctiva ; and it anastomoses with the middle men- ingeal by an offset through the sphenoidal fissures. At the front of the orbit it sends a small branch with each of the ter- minal pieces of the temporo-malar nerve ; and these join the temporal and transverse facial arteries. The central artery of the retina is a very small branch which pierces the optic nerve, and so reaches its destination in the eyeball. The supra-orbital branch arises beneath the levator palpebras and supe- rior rectus muscles ; it then takes the course of the nerve of the same name through the notch in the margin of the orbit, and ends in branches on the forehead (p. 21). As it winds round the margin of the orbit it sup- plies the eyelid and the orbicularis muscle. The ciliary branches are uncertain in their place of origin and enter the eyeball at the front and back : — The posterior ciliary., about twelve in number, are continued to the eyeball around the optic nerve, and perforate the sclerotic coat at the pos- terior part. Two of this set (one on each side of the optic nerve), named long ciliary, pierce the sclerotic farther out than the others, and lie along the middle of the eyeball. The anterior ciliary arteries arise from muscular branches of the oph- thalmic, and perforate the sclerotic coat near the cornea : in the eyeball they anastomose with the posterior ciliary. For the ending of these vessels, see the eyeball. The muscular branches are not fixed in their place of origin ; and those to the lower muscles often arise together as one trunk. The etlunoidal branches are two, anterior and posterior, and are directed through the foramina in the inner wall of the orbit : — The posterior is the smaller of the two, and furnishing small meningeal offsets (anterior) to the dura mater of the base of the skull, descends into RECTI MUSCLES. 57 the nose cavity through the openings in the cribriform plate of tlie ethmoid. The anterior branch (internal nasal) accompanies the nasal nerve to the cavity of the nose (Section XIV.), and gives likewise meningeal off- sets to the dura mater, and the fore part of the falx cerebri. The palpebral branches, one for each eyelid, generally arise together opposite the pulley of the superior oblique muscle, and then separate from one another. The arches they form have been dissected with the eyelids (p. 45). The frontal branch turns round the margin of the orbit, and is distrib- uted on the forehead (p. 21). The ophthalmic vein corresponds in its course and most of its branches with the artery of the same name. It begins at the inner angle of tlie orbit, where it joins the facial vein, and receives tributary branches in its progress to the back of the cavity. Posteriorly it leaves the artery, and escapes from the orbit by the sphenoidal fissure between the heads of tlie external rectus, to end in the cavernous sinus. The OPTIC NERVE in the orbit extends from the optic foramen to the back of the eyeball. As the nerve leaves the foramen it is surrounded by the recti muscles ; and beyond that spot the ciliary arteries and nerves entwine around it. It terminates in the retinal expansion of the eye. Dissection (fig. 12). Take away the oplithalmic artery, and divide the optic nerve about its middle, together with the small ciliary vessels and nerves. Turn forwards the eyeball, and fasten it in that position with hooks. On removing some fat the three recti muscles — inner, inferior, and outer, will appear ; and lying on the two first, are the offsets of the lower branch of the third nerve. The lower branch of the third nerve (fig. 12) supplies three muscles in the orbit. Whilst entering this space between the heads of the external rectus, it lies below the nasal, and rather above the sixth nerve. Almost immediately afterwards the nerve divides into three branches. One ('*) enters the internal rectus ; another (^) the inferior rectus ; and the third (f), the longest and most external, is continued forwards to the inferior oblique muscle which it pierces at the hinder border. Soon after its origin the last branch communicates with the lenticular ganglion, forming the short root (fig. 11, ^) of that body; and it furnishes two or more filaments to the inferior rectus. The SIXTH NERVE (fig. 12, f lies below the other nerves, and above the ophthalmic vein, in the interval between the heads of the external rectus. In the orbit it is distributed to the external rectus muscle. Recti Muscles. The internal d, inferior c, and external rectus h (fig. 12) are placed with reference to the eyeball as their names express. They arise posteriorly from the circumference of the optic foramen by a common attachment, which partly surrounds the optic nerve. But the external rectus differs from the others in having two heads : — The upper joins the superior rectus in the common origin. The lower and larger head blends on the one side with the inferior rectus in the common origin, and is attached in addition to a bony point on the lower border of the sphenoidal fissure, near the inner end ; whilst some of its muscular fibres are con- nected with a tendinous band between the heads. All the muscles are directed forwards, but the lower obliquely outwards, and have a tendinous insertion into the ball of the eye about a quarter of an inch from the cornea, and in front of the transverse diameter of the ball. 58 DISSECTION OF THE ORBIT. Between the heads of origin of the external rectus, the different nerves before mentioned are transmitted into the orbit, viz., the third, the nasal branch of the fifth, and tlie sixth, together with the ophthalmic vein. Action. The four recti muscles, attacluid to the eyeball at opposite sides in front of the transverse diameter, are able to turn the pupil in opposite directions. The inner and outer recti move the ball liorizontally around a vertical axis, the former directing the pupil towards the nose and the latter towards the temple. Fig. 12. Third View of the Orbit (Illustrations of Dissectijns). Mn.s'cles : o. Upper rectus and levator palpebra; thrown back together. h. External rectus. c. Inferior rectus.. d. Internal rectus. /. Upper oblique cut, showing the insertion. h. Insertion of inferior oblique. Nerves : 1. Upper branch of the bird. 2. Sixth nerve, 3. Inferior oblique branch of the third, 4. Branch of third to inferior rectus. 5. Branch of third to internal rectus. The upper and lower recti elevate and depress the fore part of tlie ball around a transverse axis ; but as their fibres are directed obliquely out- wards, the upper muscle turns the pupil up and in, and the lower muscle turns it down and in. By the simultaneous action of two contiguous recti, the ball will be moved to a point intermediate to that to which it would be directed by either muscle singly. I)issectio7i. By opening the optic foramen, the attachment of the recti muscles will be more fully laid bare. To dissect out the inferior oblique muscle, let the eyeball be replaced in its natural position ; then by taking ACTION OF OBLIQUE MUSCLES. 59 away the conjunctival lining of the lower eyelid near the inner part of the orbit, and removing some fat, the muscle will appear beneath the eyeball, bending from the inner to the outer side ; it may be followed outwards to its insertion into the ball. The iNP^ERiOR OBLIQUE MUSCLE (fig. 12, h) is situate near the anterior margin of the orbit, and difiers from the other muscles in being directed across, instead of parallel to the axis of the orbit. It arises from the superior maxillary bone betwixt the margin of the orbit and the groove for the lachrymal sac. From this spot the muscle passes outwards between the inferior rectus and the bone, and between the eyeball and the external rectus, to be inserted into the sclerotic coat between the outer and upper recti. The borders of the muscle look forwards and backwards, and the pos- terior receives the branch of the third nerve. The tendon of insertion is near that of the superior oblique muscle, but rather closer to the optic nerve. Action. The oblique muscles rotate the eyeball around an antero-poste- rior axis, and are supposed to be used in maintaining the parallelism of the axes of the two eyes. The upper muscle, acting by itself, would rotate the ball in such a way as to cause the inner end of the transverse axis to sink, and the pupil to be directed down and out, as in looking to the shoulder. The lower muscle would produce by itself rotation of the ball in the op- posite direction, viz., the inner end of the transverse axis would be raised, and the pupil would be inclined up and out, as in looking to the outer part of the orbit. During life the rotary movement is supposed to be chiefly employed in controlling the oblique action of the iqjper and lower recti. For instance, as the upper rectus alone would turn the pupil upwards and too much in- wards, the inner movement will be counteracted by the rotation out of the inferior oblique. And as the lower rectus will incline the pupil down and too much in, the motion inwards will be checked by the rotation out of the superior oblique. Dissection. To expose the small tensor tarsi muscle, the palpebral liga- ment uniting the eyelids to the margin of the orbit is to be cut through, where this has not been done ; but the lids must be left attached at the inner commissure by means of the tendo palpebrarum. By looking to the posterior aspect of the tendo palpebrarum, after the lids have been placed across the nose, the pale fibres of the tensor tarsi will be recognized. The TENSOR TARSI MUSCLE uriscs from the ridge on the os unguis, and slightly from the bone behind the ridge. Its fibres are pale, and form a very small fiat band, behind the ligamentum palpebrarum, which divides like that structure into a slip for each eyelid. In the lid the slip lies by the side of the lachrymal canal, and blends with the fibres of the orbicu- laris along the free margin of the tarsal cartilage. Action. By its contraction the muscle draws inwards and backwards the puncta of the lids, so as to favor the reception and passage of the tears. Dissection. A small nerve, the temporo-malar or orbital branch of the superior maxillary trunk, lies along the outer angle of the floor of the orbit, and may be brought into view after the removal of the eyeball and its muscles. This nerve is very soft and easily broken, and is covered by ))ale fleshy fibres (orbitalis muscle). Two branches, temporal and malar. 60 . DISSECTION OF THE ORBIT. . are to be traced forwards from it : and the junction of a filament of the lachrymal nerve with the former is to be sought in the bone ; the outer wall of the orbit may be cut away, bit by bit, to follow the temporal branch to the surface of the head. The temporo-malar or orbital branch of the superior maxillary nerve (fig. 26) arises in the spheno-maxillary fossa, and divides at the back of the orbit into malar and temporal branches, which ramify in the face and the side of the head with companion vessels. The malar branch (r. subcutaneus maloe) is directed forwards through a foramen in the malar bone : after emerging from its foramen, this branch supplies the orbicularis, and communicates with the facial nerve (p. 48). The temporal branch ascends in a groove in the bone on the outer wall of the orbit ; and being joined by a filament from the lachrymal nerve, passes into the temporal fossa through a foramen in the malar bone : it is then directed upwards between the temporal muscle and the skull, and perforates the temporal fascia near the orbit (p. 23). Orbitalis muscle. At the lower and outer angle of the orbit a thin fleshy layer is sometimes well seen. The fibres cross the spheno-maxillary fis- sure, being attached to the edges, and are pierced by the malar branch of the temporo-malar nerve. Lachrymal Apparatus (fig. 13). The lachrymal glands, puncta, canals, and sac, constitute the apparatus by which the tears are formed, and conveyed to the nose. The gland has been already described (p. 51). Dissection. A bristle should be introduced into each lachrymal canal through the punctum of the eyelid. The lachrymal sac will appear by removing the tensor tarsi and the areolar tissue from its surface, as it lies on the os unguis. The prolongation from the ligamentum palpebrarum over the sac should be defined. The puncta lachrymalia (^) are two small apertures, one for each lid, by which the lachrymal canals receive the tears. Each is situate in the free margin of the lid, about a quarter of an inch from the inner canthus, and in the elevation of the papilla lachrymalis. Fi 13. 1. Puncta lachrymalia. 3. Upper, and 3, Lower lachrymal canal. 4. Caruncula lachrymalis. 5. Lachrymal sac. 6. Lachrymal duct. The Eyelids and Lachrymal .Apparatus. The lachrymal canals (fig. 13, •‘’) lead from the puncta, and convey the tears to the lachrymal sac ; their situation is marked by the bristles inserted in them. In their course inwards the canals lie along the liga- mentum palpebrarum, one (^) above and the other (^) below it, and they are somewhat arched with the concavity towards each other. Internally they open near together into the lachrymal sac rather above its middle. DISSECTION OF THE NECK. 61 The canal in the upper eyelid is longer and more arched than that in the lower lid. The lachrymal sac and duct (fig. 13) extend from the inner part of the orbit to the nose, and convey the tears into the latter cavity. They form one tube, of which the upper dilated part is the sac, and the lower con- stricted end the duct. The sac, is situate in the hollow formed by the os unguis and nasal process of the superior maxillary bone. Externally it is crossed by the ligament of the eyelids, and is covered by an expansion derived from that band, which is fixed to the margin of the bony groove. If the aponeurotic covering be removed, the mucous membrane lining the interior will be seen. Into the outer side of the sac the lachrymal canals open. The duct, ® (ductus ad nasum), is the narrowed part of the tube, and is about half an inch long. It is entirely encased by bone, and corresponds with the passage of the same name in the dried skull. In the nasal cavity it opens into the front of the inferior meatus, where its opening is guarded by a piece of the mucous membrane. A bent probe introduced through the nostril may be passed into the duct from the meatus, but with destruc- tion of the valve. As the duct is continuous with the mucous membrane of the nose it has the same structure, viz., a fibrous external layer with a mucous lining. The epithelium of the sac and duct is ciliated as in the nose, but in the lachry- mal canals it is scaly. Directions. The examination of the eyeball may be omitted witli more advantage to the student till the dissection of the head and neck has been completed. The description of the eye will be found at the end of the book. Section V. DISSECTION OF THE NECK. Position. For the dissection of the right side of the neck let the head be supported at a moderate height on a block, and let the face be turned to the left side and fastened in that position witli hooks. To obtain a good view of the region, the right arm may be drawn under the body, with the object of depressing the point of the shoulder, and putting the neck parts on the stretch. In some bodies, owing to a difference in the form of the neck, the best position will be obtained by placing the upper limb over the chest. Surface-marking. The side of the neck presents a somewhat square out- line, and is limited in the following way : — Below is the prominence of the clavicle ; and above is the base of the lower jaw with the skull. In front the boundary is a line from the chin to the sternum ; and behind, another line from the occiput to the acromial end of the clavicle. The part thus included is divided into two triangular spaces (anterior and pos- terior) by the diagonal line of the projecting sterno-mastoid muscle. And in consequence of the position of that muscle the base of the anterior space is at the jaw, and the apex at the sternum ; whilst the base of the posterior one is at the clavicle, and the apex at the head. The surface in front of the sterno-mastoid is depressed at the upper part 62 DISSECTION OF THE NECK. of the neck, near the position of the carotid vessels; and behind the muscle, just above the clavicle, is another slight hollow which points to the situa- tion of the subclavian artery. Along the middle line of the neck the following parts can be recognized through the skin : — About two inches and a half from the base of the jaw is the eminence of the os hyoides, with its cornu extending laterally on each side. Below this may be felt the wide prominence of the thyroid cartilage, called pomum Adami, which is most marked in man : and be- tween the cartilage and the hyoid bone is a slight interval, corresponding with the thyro-hyoid membrane. Inferior to the thyroid, is the narrow prominent ring of the cricoid car- tilage ; and between the two the finger may distinguish another interval, which is opposite the crico-thyroid membrane. In some bodies, especially in women, the swelling of the thyroid gland may be felt by the side of the trachea. From the cricoid cartilage to the sternum, and between the sterno-mas- toid muscles, is a depression, whose depth is much increased in emaciated persons, in which the tube of the trachea can be recognized. Direction. As the time for turning the body will not allow the examina- tion of the whole side of the neck, the student should lay bare in this stage only the parts behind the sterno-mastoid muscle. Dissection. To raise the skin Irom the posterior triangle of the neck, make an incision along the sterno-mastoid muscle from the one end to the other, and afterwards along the clavicle as far as the acromion. The tri- angular flap of skin is to be reflected from before back towards the trapezius muscle. The superficial fascia which will then be brought into view, con- tains the platysma ; and to see that muscle, it will be necessary to take the subcutaneous fat from the surface of the fibres. The PLATiSMA MYOiDES is a thin subcufaneous muscular layer, which is now seen only in its lower half. The muscle is placed across the side of the neck, and extends from the top of the shoulder to the face. Its fleshy fibres take origin by fibrous bands from the clavicle and the acro- mion, and below those bones from the superficial fatty layer covering the pectoral and deltoid muscles ; ascending through the neck, the fibres are inserted into the jaw. The lower part of the muscle is more closely united to the skin than the upper, and covers the external jugular vein as well as the lower part of the posterior triangle. At first the fibres of the muscle are thin and scat- tered, but they increase in strength as they ascend. The oblique direc- tion of the fibres should be noted, because in venesection in the external jugular vein the incision is to be so made as to divide them across. The use will be found with the description of the remainder of the muscle. Dissection. The platysma is now to be cut across near the clavicle, and to be reflected upwards as far as the incision over the sterno-mastoid muscle, but it is to be left attached at that spot. In raising the muscle the student must be careful of tlie deep fascia of the neck ; and he should dissect out the external jugular vein, and the superficial descending branches of the cervical plexus, whicli are close beneath the platysma. The external jugular vein (fig. 14, commences in the parotid gland (p. 42), and is directed backwards beneath the })latysma to the lower part of the neck, where it pierces the deej) cervical fascia to open into the suh- clavian vein. Its course down the neck will be marked by a line from POSTERIOR TRIANGULAR SPACE. 63 the angle of the jaw to the middle of the clavicle. Beyond the sterno- mastoid muscle the vien is dilated, and the swollen part (sinus) is limited by two pairs of valves — one being situate below at the mouth of the vein, and the other near the muscle. Small superficial branches join the vein, and an offset connects it with the anterior jugular vein. Its size, and the height at which it crosses the sterno-mastoid muscle, are very uncertain. The deep cervical fascia consists, like the aponeuroses in other regions of the body, of a superficial layer which surrounds the neck continuously, and of processes that are prolonged inwards between the muscles. In some bodies this fascia is thin and indistinct. In its extent round the neck the membrane incases the sterno-mas- toideus, and presents a different disposition before and behind that muscle. As now seen passing backwards from the muscle, the fascia continues over the posterior triangular space, and incloses the trapezius in its progress to the spines of the vertebrae. At the lower part of the neck it is attached to the clavicle and is perforated by the external jugular vein, and tlie cutaneous nerves. After the superficial layer has been removed near the clavicle, a deep process may be observed to surround the small omo-hyoid muscle, and to extend under the clavicle, where it is fixed to the back of that bone, and the inner end of the first rib. POSTERIOR TRIANGULAR SPACE. This space (fig. 14), having the form and position before noted, is about eight inches in length. It contains the cervical and brachial plexuses, with the portion of the subclavian artery on which a ligature is usually placed, and some offsets of the vessel and the nerves. Dissection. By the removal of the cervical fascia and the fat between the sterno-mastoid and trapezius muscles, the posterior triangle of the neck will be displayed. In the execution of this task, the student may obtain some assistance by attending to the following remarks : — Crossing the space obliquely about an inch above the clavicle, and dividing it into two, is the small omo-hyoid muscle (fig. 14, ^). Close to or under the upper border of the muscle lie the small nerve and vessels to it : the nerve being traceable to the descendens noni, and the artery to the supra-scapular. Above the omo-hyoid muscle will be found the ramifications of the branches of the cervical plexus, together with the spinal accessory nerve ; the latter will be recognized by its piercing sterno-mastoid muscle. Tlie greater number of the branches of the cervical plexus descend in the space to the shoulder ; but the small occipital and great auricular nerves ascend to the head, and the superficial cervical branch is directed forwards over the sterno-mastoid muscle. Below the omo-hyoideus are the subclavian artery and the brachial plexus, which have a deep position. In this part also the following ves- sels and nerve are to be sought, viz., the supra-scapular vessels behind tlie clavicle ; the transverse cervical vessels which are higher in the neck, but take an outward direction beneath tlie omo-hyoid muscle ; and, lastly, the small branch of nerve to the subclavius muscle, which lies about the mid- dle of the space between tlie clavicle and omo-hyoideus. Underneath the trapezius, where it is attached to the clavicle, the 64 DISSECTION OF THE NECK serratus magnus muscle appears ; and behind the large cervical nerves, towards the lower part of the space, is placed the middle scalenus muscle. Through the scalenus issue two muscular nerves ; one, formed by two roots, for the serratus magnus ; the otlier smaller, and higher up, for the rhomhoidei. Fig. 14. Part of the Posterior Triangle of the Neck is here displayed, but the student should carry the dissection as high as the head, so as to lay bare the whole ot that space. 1. Sterno-mastoideus. 2 Trapezius. 8. Posterior belly of the omo-hyoid muscle. 4. Anterior scalenus, with the phrenic nerve oil it. f). Middle scalenus muscle. 6. Elevator of the angle of the scapula. 7. Third part of the subclavian artery. 8. External jugular vein joining the subcla- vian below'. 9. Nerves of the brachial plexus. 10. Spinal accessory nerve. (Blandin’s Surgical Anatomy.) Limits of the space. The space is bounded in the front by tlie sterno- mastoid muscle, ^ ; and behind by the trapezius, 'K Its base corresponds with the middle third of the clavicle, and its apex is at the skull. In its POSTERIOR TRIANOULAR SPACE. 65 area are several muscles, which are placed in the following order from above down, viz., splenius capitis, levator anguli scapulae ^ ; and the mid- dle scalenus ^ ; and at the lower and outer angle, somewhat beneath the trapezius lies the upper part of the serratus magnus. Covering the space are the structures already examined, viz,, the skin and superficial fascia, the platysma over the lower half or two-thirds, and the deep fascia. Tlie small omo-hyoid muscle, crosses the lower jmrt of the space, so as to subdivide it into two — a lower or clavicular, and an upper or occi- pital. The clavicular fart is small in size and close to the clavicle, and con- tains the subclavian artery. It is triangular in form, with its base directed forwards ; and is bounded in front by the sterno-mastoid, ^ ; above by the omo-hyoid muscle, ^ ; and below by the clavicle. This small space meas- ures commonly about one inch and a half from before backwards, and about half that in front at its base. Crossing the area of this portion, rather above the level of the clavicle, is the trunk of the subclavian artery, ^ (its third part), which issues from beneath tlie anterior scalenus muscle, and is directed over the first rib to the axilla. In the ordinary condition of tlie vessel the companion subcla- vian vein is seldom seen, owing to its situation being lower down beneath the clavicle. Above the artery are the large cords of the brachial plexus, which accompany the vessel, and become closely applied to it beneath the clavicle. Behind the artery and the nerves is the middle scalenus muscle, And below the vessel is the first rib. Along the lower boundary of the space, and rather beneath the clavicle lie the supra-scapular vessels ; and crossing tlie upper angle, at the meet- ing of the omo-hyoid and sterno-mastoid muscles, are the transverse cer- vical vessels. Entering the space from above is the external jugular vein, ®, wliich descends over or under the omo-hyoideus near the anterior part, and opens into tlie subclavian vein ; in this spot the vein receives the supra-scapular and transverse cervical branches, and sometimes a small vein, over the clavicle, from the cephalic vein of the arm. The size of the clavicular part of the space from before back is influ- enced by the attachment of the trapezius and sterno-mastoid muscles along the clavicle ; in some bodies these muscles occupy nearly the whole length of that bone, leaving but a small interval between them ; and in others they meet so as to cover the underlying vessels. This space may be fur- ther increased or diminished from above down by the position of the omo- hyoideus in the neck ; for this muscle may lie close to the clavicle, being attached thereto, or it may be distant one inch and a half from that bone. In depth the space varies naturally ; and in a short thick neck with a prominent clavicle, the artery is farther from the surface than in the op- posite condition of the parts. But the depth may be altered much more by the position of the clavicle, according as the limb may be raised or de- pressed. And lastly, the artery may be concealed entirely in its usual position by forcing upwards the arm and shoulder, as the collar bone can be raised above the level of the omo-hyoid muscle. The situation of the trunk of the subclavian artery may vary much, for the vessel may be one inch and a half above the clavicle, or at any point intermediate between this and its usual level just above the prominence of that bone. Further, its position to the anterior scalenus may be changed; and instead of the vessel being beneath, it may be in front of, or even between the fibres of that muscle. 5 66 DISSECTION OF THE NECK. Commonly there is not any branch connected with the artery in this part of its course; but the posterior scapular branch (tig. 14) may take origin from it at different distances from the scalenus, or there may be more than one branch (Quain). The subclavian vein rises upw^ards not unfrequently as high as the artery, or it may even lie with the artery beneath the anterior scalenus in some rare instances. The position of the external jugular vein with regard to the subclavian artery is very uncertain ; and the branches connected with the lower end may form a kind of plexus over the arterial trunk. The occipital part of the posterior triangle is larger than the other. Its boundaries in front and behind are the sterno-mastoid and the trapezius ; and it is separated from the clavicular portion by the omo-hyoid muscle. In it are contained chiefly the ramifications of the cervical plexus ; and a chain of lymphatic glands lies along the sterno-mastoid muscle. The spinal accessory nerve, is directed obliquely across this interval from the sterno-mastoid muscle, which it pierces, to the under surface of the trapezius ; and a communication takes place between this cranial and the spinal nerves in the space. Superficial Branches of the Cervical Plexus. Behind the sterno-mastoid muscle appear some of the ramifications of the cervical nerves in the plexus of the same name ; and superficial branches are fur- nished from these both upwards and downwards. The ASCENDING SET (fig. 14) are three in number, viz., small occipital, great auricular, and superficial cervical. The small occipital branch (fig. 2, ^) comes from the second cervical nerve, and is directed upwards to the head along the posterior border of the sterno-mastoid muscle. At first the nerve is beneath the fascia ; but near the occiput it becomes cutaneous, and is distributed between the ear and the great occipital nerve (p. 24). Occasionally there is a second cuta- neous nerve to the head. The great auricular nerve (fig. ‘2, ^) is a branch of the part of the plexus formed by the second and third cervical nerves. Perforating the deep fascia at the posterior border of the sterno-mastoid muscle, the nerve is directed upwards beneath the platysma to the lobule of the ear, where it ends in the following branches : — The facial branches are sent forwards to the integuments over the parotid, and a few slender filaments pass through the gland to join the facial nerve. The auricular branches ascend to the external ear, and are chiefly dis- tributed on its cranial aspect ; one or more reach the opposite surface by piercing the pinna. On the ear they communicate with branches furnished from the facial and pneumogastric nerves. The mastoid branch is directed backwards to the integuments between the ear and the mastoid process ; and it joins the posterior auricular branch of the facial nerve (p. 23). The superficial cervical nerve (fig. 2, ’^) springs from the same source as the preceding, and turns forwards round the sterno-mastoid muscle about the middle. Afterwards it pierces the fascia and platysma, and ramifies over the anterior triangular space (see p. 68). There may be more than one branch to represent this nerve. The DESCENDING SET of branches (fig. 2) (supra-clavicular), are de- rived from the third and fourth nerves of the plexus, and are directed FORE PART OF XECK. 67 towards the clavicle over the lower yjart of the triangular space. Their number is somewhat uncertain, but usually there are about three on the clavicle. The most internal branch (sternal) crosses the clavicle near its inner end ; the middle branch lies about the middle of that bone ; and the posterior (acromial) turns over the attachment of the trapezius to the acromion. All are distributed in the integuments of the chest and shoulder. Derived from the descending set are two or more posterior cutaneous cervical nerves, which ramify in the integument over the lower two thirds of the fore part of the trapezius. The lymphatic glands (glanduloB concatenate) lie along the sterno- mastoid muscle, and are continuous at the lower part of the neck with the glands in the cavity of the. thorax. There is also a superficial chain along the external jugular vein. Dissection, The dissection of the posterior triangle should be repeated on the left side of the neck, in order that the diflference in the vessels may be observed. Afterwards the reflected parts are to be replaced and care- fully fastened in their natural position with a few stitclies, preservative fluid or salt having been previously applied. Directions. It is supposed that the body will now be turned on the fore part for the examination of the Back ; and during the time allotted for this position the dissector of the. head is to learn tlie posterior part of the neck. (Dissection of the Back.) After the completion of tlie Back, the student should take out the spinal cord, and then return to the dissection of the front of the neck, which is described below. FRONT OF THE NECK. Directions. Supposing the thorax and Back finished, the head and neck may be detached from the trunk by dividing the spinal column be- tween the second and third dorsal vertebrie, and cutting through the arch of the aorta beyond its large branches (if this is not done), so as to take that piece of the vessel with the head. The dissector continues his work on the remainder of the right side of the neck ; but if the facial nerve has been omitted, it should be first learnt (p. 47). Position. Supposing the facial nerve completed, a small narrow block is to be placed beneath the left side of the neck, and the face is to be turned from the dissector. Further, the neck is to be made tense by means of hooks, the chin being well raised at the same time. Dissection. An incision along the base of the jaw on the right side (if it has not been made already) will readily allow the piece of integument in front of the sterno-mastoideus to be raised towards the middle line. Beneath the skin is the superficial fascia, containing very fine offsets of the superficial cervical nerve. To define the platysma muscle, remove the fat which covers it, carrying the knife down and back in the direction of the fleshy fibres. Platysma Myoides. The anterior part of the platysma, viz., from the sterno-mastoid muscle to the lower jaw, covers the greater portion of the anterior triangular space. At the base of the jaw it is inserted be- tween the symphysis and the masseter muscle ; while otlier and more posterior fibres are continued over the face, joining the depressor anguli 68 DISSECTION OF THE NECK. oris and risorius, as far as the fascia covering the parotid gland, or even to the cheek bone. The fibres have the same appearance in this as in the lower half of the muscle, but they are rather stronger. Below the chin the inner fibres of opposite muscles cross for a distance of about an inch, but those which are superficial do not belong always to the same side. Action. The ordinary action of this muscle is confined to the skin of the neck, which it throws into longitudinal wrinkles ; but it can depress the corner of the mouth by the slip prolonged to the face. Through its attachment to the jaw it will assist in opening the mouth. Dissection. Raise the platysma to the base of the jaw, and dissect out the branches of the superficial cervical nerve, and the cervical branches of the facial nerve that are beneath it. Clean also the deep fascia of the neck, and the anterior jugular vein which is placed near the middle line. Tlie superjicial cervical nerve has been traced from its origin in the cervical plexus to its position on tlie deep fascia of the neck (p. 66); but the nerve may arise from tlie plexus by two pieces. Beneath the platysma it divides into an ascending and a descending branch : — The ascending branch perforates the platysma, supplying it, and ends in the integuments over the anterior triangle, about half way down the neck. Whilst this branch is beneath the platysma it joins the facial nerve. The descending branch likewise passes through the platysma, and is distributed to the teguments below the preceding, reaching as low as the sternum. The infra-maxillary branches of the facial or seventh cranial nerve (rami subcutanei colli) (p. oO) pierce the deep cervical fascia, and pass forwards beneath the platysma, forming arches across the side of the neck (fig. 9), which reach as low as the hyoid bone. Most of the branches end in the platysma, but a few filaments perforate it, and reach the integu- ments. Beneath the muscle there is a communication between the branches of the facial and the offsets of the superficial cervical nerve. Dissection. Cut across the external jugular vein about the middle, and throw the ends up and down. Afterwards the superficial nerves of the neck may be divided in a line with the angle of the jaw, the anterior ends being removed, and the posterior reflected. The great auricular nerve may be cut through and the ends reflected. The part of the deep cervical fascia in front of the sterno-mastoideus is stronger than that behind the muscle, and has the following arrangement. Near the sternum the fascia forms a white firm membrane, which is at- tached to that bone ; but higher in the neck it becomes thinner, and is fixed above the lower jaw and the zygoma, covering also the parotid gland. From the ramus of the jaw a piece is prolonged downwards, be- tween the i)arotid and submaxillary glands, to join the styloid process ; this piece is named the stglo-niaxillary ligament. And from the angle of the jaw a strong piece is continued to the sterno-mastoideus, which fixes forwards the anterior border of tliat muscle. Layers of the membrane are prolonged between the muscles ; and that beneath the sterno-mastoid is connected with the sheath of the cervical vessels. One of these beneath the sterno-thyroid muscle, descends in front of the great vessels at the root of the neck to the arch of the aorta, and the pericardium. ANTERIOR TRIANGULAR SPACE. 69 ANTERIOR TRIANGULAR SPACE. This space (fi". lo) contains the carotid vessels and their branches, with many nerves ; and it corresponds with the liollow on the surface of the neck in front of the sterno-mastoid muscle. Dissection. To define the anterior triangular space and its contents, take away the deep fascia of the neck, and the fat, but without injuring or disjdacing the several parts. First clean the surface of tlie hyoid mus- cles that appear along the middle line, leaving untouched the anterior jugular vein. The trunks into which the large carotid artery bifurcates are to be fol- lowed upwards, especially the more superficial one (external carotid), whose numerous branches are to be traced as far as they lie in the space. In removing the sheath from the vessels, as these appear from beneath the muscles at the lower part of the neck, the dissector should be careful of the small descending branch of the hypo-glossal nerve in front of it. In the sheath between the vessels (carotid artery and jugular vein) will be found the pneumogastric nerve, and behind the sheath is the sympathetic nerve. Crossing the space, in the direction of a line from the mastoid process to the hyoid bone, are the digastric and stylo-hyoid muscles, with several nerves directed transversely. Thus lying below them is the hypo-glossal nerve, which gives one branch (descendens noni) in front of the sheath, and another to the thyroid-hyoid muscle. Above the muscles, and taking a similar direction between the two carotid arteries, are the glosso-pharyn- geal nerve and the stylo-pharyngeus muscle. Directed downwards and backwards from beneath the same muscles to the sterno-mastoideus, is the spinal accessory nerve. On the inner side of the vessels, between the hyoid bone and the thy- roid cartilage, the dissector will find the superior laryngeal nerve ; and by the side of the larynx, with the descending part of the superior thyroid artery, the small external laryngeal branch. Clean then the submaxillary gland close to the base of the jaw ; and on partly displacing it from the surface of the mylo-hyoid muscle, the student will expose the small branch of nerve to that muscle with the submental artery. The interval between the jaw and the mastoid process is supposed to be already cleaned by the removal of the parotid gland in the dissection of the facial nerve. Limits of the space. Behind, is the sterno-mastoid muscle, and in front, a line from the chin to the sternum, along the middle of the neck. Above, at the base of the space, Avould be the lower jaw, the skull, and the ear ; and below, at the apex, is the sternum. Over this space are placed the skin, the superficial fascia with the platysma, the deep fascia, and the ramifications of tlie facial pnd superficial cervical nerves. Muscles in the space. In the area of the triangular interval, as it is above defined, are seen the larynx, and pharynx in part, and many mus- cles converging towards the hyoid bone as a centre, some being above and some below it. Below are the depressors of that bone, viz., omo- hyoid, sterno-hyoid, and sterno-tliryoid. Mo and above the os hyoides are the elevator muscles, viz., mylo-hyoid, digastric, and stylo-liyoid. Con- 70 DISSECTION OF THE NECK. nected with the back of the hyoid bone and the layrnx are some of the constrictor muscles of the gullet. Vessels in the triangular space. The carotid bloodvessels, ® and occupy the hinder and deeper part of the space along the side of the sterno-mastoid muscle ; and their course would be marked on the surface by a line from the sterno-clavicular articulation to a point midway between the jaw and the mastoid process. As high as the level of the cricoid car- tilage they are buried beneath the depressor muscles of the os hyoides ; but beyond that spot they are covered by the superlicial layers over the space, and by the sterno-mastoid muscle which, before the parts are dis- placed, conceals the vessels as far as the parotid gland. For a short distance after its exit from beneath the muscles at the root of the neck, the common carotid artery remains a single trunk, ®;- but opposite the upper border of the thyroid cartilage it divides into two large vessels, external and internal carotid. From the place of division these trunks are continued onwards, beneath the digastric and stylo-hyoid mus- cles, to the interval between the jaw and the mastoid process. At first the trunks lie side by side, the vessel destined for the internal parts of the head (internal carotid) being the more posterior or external of the two; but above the digastric muscle it becomes deeper than the otlier. The more superficial artery (external carotid) furnishes many branches to the neck and the outer part of the head, viz., some forwards to the larynx, tongue, and face; others backwards to the occiput and the ear; and others upwards to the head. But the common carotid does not always divide, as here said. For the point of branching of the vessel may be moved from the upper border of the thyroid cartilage, either upwards or downwards, so that the trunk may remain undivided till it is beyond the os hyoides, or end in branches opposite the cricoid cartilage. The division beyond tlie usual place is more frequent than the branching short of that spot. It may ascend as an undivided trunk (though very rarely), furnishing offsets to the neck and head. In close contact with the outer side of both the common and the internal carotid artery, and incased in a sheath of fascia with them, is the large internal jugular vein, which receives branches in the neck corresponding with some of the branches of the superficial artery. In some bodies the vein may cover the artery, and the branches joining it above may form a kind of plexus over the upper part of the common carotid. Nerves in the space. In connection, more or less intimate, with the large vessels, dre the following nerves with a longitudinal direction : — In front of the sheath lies the descending branch of the hypo-glossal nerve ; within the sheath, between the carotid artery and jugular vein, is the pneumogastric nerve; and behind the sheath is the sympathetic nerve. Along the outer part of the vessels the spinal accessory nerve extends for a short distance, till it pierces the sterno-mastoid muscle. Several nerves are placed across the vessels : — thus, directed transversely over the two carotids, so as to form an arch below the digastric muscle, is the hypoglossal nerve, which gives downwards its branch (d(^scendens noni) most commonly in front of the sheath. Appearing on the inner side of the carotid arteries, close to the base of the space, is the glosso-pharyngeal nerve, wliicli courses forwards between tliem. Inside the internal carotid artery, opposite the hyoid bone, the superior laryngeal nerve comes into STERNO-CLEIDO-MASTOIDEUS. 71 sight; whilst a little lower down, with the descending branches of the thyroid artery, is the external laryngeal branch of that nerve. Glands in the space. Two glandular bodies, the submaxillary, and thyroid, have their seat in this triangular space of the neck. The sub- maxillary gland is situate altogether in front of the vessels, and is partly concealed by the jaw ; and beneath it on the surface of the mylo-hyoideus is the small nerve to that muscle; with the submental artery. By the side of the thyroid cartilage, between it and the common carotid artery, lies the thyroid body beneath the sterno-thyroid muscle: in the female this body is more largely developed than in the male. At the base of the space, if the parts were not disturbed, would be the parotid gland, which is wedged into the hollow between the jaw and the mastoid process, and projects somewhat below the level of the jaw. Its connections have been noticed at p. 41. Directions. The student has to proceed next with the examination of the individual parts that have been referred to wdth the triangular s[)aces. Anterior jugular vein. This small vein occu})ies the middle line of the neck, and its size is dependent upon the degree of development of the ex- ternal jugular. Beginning in some small branches below the chin, the vein descends to the sternum, and then bends outwards beneath the steriio- mastoid muscle, to 0 })en into the subclavian vein, or into the external jugular. In the neck the anterior and external jugular veins communicate. Tliere are two anterior veins, one for each side, though one is usually larger than the other ; and at the bottom of the neck they are joined by a transverse branch. The STERNO-CLEIDO-MASTOID MUSCLE (fig. 15, *) fo -ms the superficial prominence of the side of the neck. It is narrower in the centre than at the ends, and is attached below by two heads of origin, which are separated by an elongated interval. The inner head is fixed by a narrowed tendon to the anterior surface^of the first piece of the sternum ; and the outer head has a wide fleshy attachment to the sternal third of the clavicle. From this origin the heads are directed upwards, the internal passing backwards, and the external almost vertically, and are blended about the middle of the neck in a roundish belly. Near the skull the muscle ends in a tendon, which is inserted into the mastoid process at the outer as})ect from base to tip, and by a thin aponeurosis into a rough surface behind that process, and into the outer part of the upper curved line of the occipital bone. The muscle divides the lateral surface of the neck into two triangular spaces. On its cutaneous aspect the sterno-mastoid is covered by the com- mon integuments, by the platysma and deep fascia, and by the external jugular vein and the superficial branches of the cervical plexus (across the middle). If the muscle be cut through below and raised, it will be seen to lie on the following parts : The clavicular origin is superficial to the anterior scalenus and omo-hyoid muscles ; and the sternal head conceals the depressors of the hyoid bone, and the common carotid artery with its vein and nerves. After the union of the heads, the muscle is })laced over the cervical plexus, and the middle scalenus and elevator of the angle of the scapula ; and near the skull, on the digastric and splenius muscles, the occipital artery, and part of the parotid gland. The spinal accessory per- forates the muscular fibres about the upper third. Action. Both muscles acting bend the head forwards ; but one muscle turns the face to the opposite side. In conjunction wdth the muscles at- 72 DISSECTION OF THE NECK. taclied to the mastoid process one sterno-mastoideus will incline the head towards the shoulder of the same side. / Fig. 15. View of the Anteriok Triangular Space of the Neck (Quaia’s “Arteries”). 1. Sterno-mastoicleus. 7 Interual jugular vein. 2. Stenio-hyoideus. 8. Externa] jugular vein. — In the Drawing 3. Anterior belly of the omo-hyoideus. from which this cut is copied the sterno-mas- 4. Thyro-hyoideus. toid is partly cut through. 6. Common carotid artery dividing. In laborious resjiiration the two muscles wall assist in elevating the ster- num. The OMO-iiYOiD MUSCLE crosscs beneath the sterno-mastoideus, and consists of two fleshy bellies united by a small round intermediate tendon (fig. 14, ^). The origin of the niuscle from the sca])ula, and the connec- tions of the })osterior part, are to be studied in the dissection of the Back. From the intervening tendon the anterior fleshy belly (tig. 15, is directed u[)wards along the outer border of the sterno-hyoid muscle, and is inserted into the lower })art of the body of the hyoid bone, close to the great cornu. Tlie anterior belly is in contact with the fascia, after escaping from be- neath the sterno-mastoid ; and rests on the sterno-thyroideus. This part of the muscle crosses the common carotid artery and internal jugular vein on a level with the cricoid cartilage. Action. The anterior belly depresses the hyoid bone ; and the posterior DEPRESSORS OF OS HYOIDES. 73 is said by Theile to make tense the deep fascia of the neck with vvliieli it is connected. The STERNO-iiYOiD MUSCLE (fig. 15, is a flat tliin band nearer the middle line than the preceding. It arises from the posterior surface of the sternum and the cartilage of the first rib. From this spot the fibres ascend, and are inserted into the lower border of the body of the os hyoides, inter- nal to the preceding muscle. One surface is in contact with the fascia, and is often marked by a ten- dinous intersection near the clavicle. When the muscle is divided and turned aside, the deep surface will be found to touch the sterno-thyroideus, and the superior thyroid vessels. The muscles of opposite sides are sepa- rated by an interval which is largest below. Action. It draws the os hyoides downwards after swallowing ; and in laborious res[)iration it will act as an elevator of the sternum. The STERNO-THYROiD MUSCLE is wider and shorter than the sterno- hyoid, beneath which it lies. Like the other hyoid muscle, it arises from the posterior surface of the sternum, and the cartilage of the first rib below the former ; and it is inserted into the oblique line on the side of the thy- roid cartilage, where it is continuous with the thyro-hyoid muscle. The inner border touches its fellow for about an inch, along the middle line of the neck, whilst the outer reaches over the carotid artery. The superficial surface is concealed by the preceding hyoid muscles ; and the oj)posite surface is in contact with the lower part of the common carotid artery, the trachea, and the larynx and thyroid body. A transverse, ten- dinous line crosses the muscle near the sternum. Action. Its chief use is to aid the preceding muscle in lowering rapidly the hyoid bone after deglutition ; but it can draw down and forwards the thyroid cartilage, and assist in rendering tight the vocal cords. Like the sterno-hyoid it participates in the movement of the chest in laborious breathing. The THYRO-HYOIDEUS (fig. 15, is a continuation in direction of the last muscle. Beginning on the side of the thyroid cartilage, the fibres ascend to the inner half of the great cornu of the os hyoides, and to the outer part of the body of the bone. On the muscle lies the omo-hyoideus ; and beneath it are the superior laryngeal nerve and vessels. It is sometimes considered one of the special muscles of the larynx. Action. Raising the thyroid cartilage towards the os hyoides, it renders lax the vocal cords, and assists in placing the cartilage under the tongue preparatory to swallowing. Directions. — The remaining parts included in this section are the scaleni muscles and the subclavian bloodvessels, with the cervical nerves and the carotid bloodvessels. The student may examine them in the order here given. Dissection (fig. 16). Siq)posing the sterno-mastoid cut, the fat and fascia are to be taken away from the lower part of the neck, so as to pre- pare the scaleni muscles with the subclavian vessels and their branches. By means of a little dissection the anterior scalenus muscle will be seen ascending from the first rib to the neck, having the jdirenic nerve and sub- clavian vein in front of it, the latter crossing it near the rib. The part of the subclavian artery on the inner side of the scalenus is then to be cleaned, care being taken not only of its branches, but of the branches of the sympathetic nerve which course over and along it from the 74 DISSECTION OF THE NECK. neck to the chest. This dissection will be facilitated by the removal of a part or the whole of the clavicle. All the branches of the artery are in general easily found, except the superior intercostal, which is to be souglit in the thorax in front of the neck of the first rib. On the branch (inferior thyroid) ascending to the Fig. 16. A VIEW OF THE Common Carotid and Subclavian Arteries (Quain’s “ Arteries”). 1. Anterior scalenus, with the phrenic on it. 2. Middle scalenus. 3. Levator anguli scapulae. 4. Omohyoideus. 5. Kectus capitis anticus major. 6. Common carotid artery. nerve 7. Subclavian vein. 8. Subclavian artery. 9. Digastric muscle. 10. Parotid gland, 11. Submaxillary gland. 12. Thyroid body. 13. Trapezius muscle, reflected. thyroid body, or near it, is the middle cervical ganglion of the sympathetic ; and the dissector should follow downwards from it a small cardiac nerve to the thorax. Only the origin and first part of the course of the arterial branches can be now seen ; their termination is met with in other stages of this dissection, or in the dissection of other parts of the body. Now the student should seek tlie small right lymphatic duct that opens into the subclavian vein near its junction with the jugular. A notice of it will be given with the lympliatics of the thorax. SCALENI MUSCLES. 75 The outer part of the sul)clavian artery having been already prepared, let the dissector remove more completely the fibrous tissue from the nerves of the brachial plexus. From the plexus trace the small branch to the subclavius muscle ; and the branches to the rliomboid and serratus muscles, which pierce the middle scalenus. If it is thought necessary, the anterior scalenus may be cut through after the artery has been studied. Clean the cervical plexus, and seek its muscular branches, the small twigs to join the descendens noni, and the root^ of the phrenic nerve. Lastly, let the middle scalenus muscle be defined, as it lies beneath the cervical nerves. The SCALENI muscles are usually described as tliree in number, and are named from their relative position, anterior, middle, and posterior ; they extend from the first two ribs to the transverse processes of the cervical vertebroB. The SCALENUS ANTicus (fig. 16, extends from the first rib to the lower cervical vertebra3, and is somewhat conical in shape. It is attached by its apex to the inner border and the upper surface on the first rib, so as to surround the rough surface or projection on this aspect of the bone ; and by its base it is inserted into the anterior transverse processes of four of the cervical vertebrae, viz., sixth, fifth, fourth, and third (fig. 45,^). More deeply seated below tlian above, the muscle is concealed by the clavicle and the subclavius, and by the clavicular part of tlie sterno-mas- toid : the phrenic nerve lies along its cutaneous surface, and the subclavian vein crosses over it near the rib. Along the inner border is the internal jugular vein. Beneath the scalenus are the pleura, the subclavian artery, and the nerves of the brachial plexus. The insertion into the vertebras corresponds with the origin of the rectus capitus anticus major muscle. Action. The anterior of these muscles raises strongly the first rib,/in consequence of its forward attachment. If the rib is fixed, it bends for- ward the lower part of the neck. The scALENius MEDius MUSCLE (fig. 16, is larger than the anterior, and extends farthest of all on the vertebrae. Inferiorly it is attached to a groove on the upper surface of the first rib, extending obliquely forwards from the tubercle to tlie outer border for one inch and a half. The muscle ascends behind the spinal nerves, and is inserted, into the tips of the poste- rior transverse processes of all the cervical vertebrae (fig. 45, ®). In contact with the anterior surface are the subclavian artery and the spinal nerves, together with the sterno-mastoid muscle ; whilst the poste- rior surface touches the posterior scalenus, and the deep lateral muscles of the back of the neck. The outer border is perforated by the nerves of the rhomboid and serratus muscles. Action. Usually it elevates the first rib. With the rib fixed, the cer- vical part of the spine will be inclined laterally by one muscle. The SCALENUS POSTICUS (fig. 45, is considerable in size, and appears to be but part of the preceding. It is attached below by a slip, about half an inch wide, to the second rib, in front of the serratus posticus superior; and it is inserted above with the scalenus medius into two or three of the lower cervical transverse processes. Action. It acts as an elevator of the second rib ; and its fibres having the same direction as those of the medius, it will incline the neck in the same way. The SUBCLAVIAN ARTERY (fig. 16) is the first part of the large vessel supplying the upper limb with blood, which is thus designated from its 76 DISSECTION OF THE NECK. position beneath the clavicle. This vessel (®) is derived from the branch- ing of the innominate artery behind the sterno-clavicular articulation, and the part of it named subclavian extends as far as the lower border of the first rib. To reach the limb the artery crosses the lower part of the neck, taking an arched course over the bag of the pleura and the first rib, and between the scaleni muscles. For the purpose of describing its numerous connections the vessel may be divided into three parts : the first extending from the sterno-clavicijar articulation to the inner border of the interior scalenus ; the second, beneath the scalenus ; and the third, from the outer border of that muscle to the lower edge of the first rib. First part. Internal to the anterior scalenus the artery lies deep in the neck, and ascends slightly from its origin. Between the vessel and the surface will be found the common integumentary coverings with the pla- tysma and the deep fascia, the sterno-mastoid, sterno-hyoid and sterno- thyroid muscles, and a strong deep process of fascia from the inner border of the scalenus muscle. This part of the subclavian lies over the longus colli muscle, though at some distance from it, and separated from it by fat and nerves. Below the artery is the pleura, which ascends into the arch formed by the vessel. Veins. The innominate vein, and the ending of the subclavian (’), form an arch below that of the artery. The large internal jugular vein crosses the arterial trunk close to the scalenus ; and underneath this vein, with the same direction, lies the vertebral vein. Much more superficial, and separated from the artery by muscles, is the deep part of the anterior jugu- lar vein. Nerves. In front of the artery lies the pneumogastric nerve, near to the internal jugular vein ; and inside this, the lower cardiac branch of the same nerve trunk. Behind the subclavian artery winds the recurrent branch of the [)neumogastric ; and still deeper is the cord of the sympa- thetic nerve with its cardiac branches, one or more of its offsets entwining round the vessel. Second part. Beneath the scalenus the vessel is less deep than when placed internal to that muscle, and at this spot it rises highest above the clavicle. The second part, like the first, is covered by the integuments, platysma, and deep fascia; then by the clavicular origin of the st erno- mastoideus ; and lastly by the anterior scalenus. Behind the vessel is the middle scalenus. Below the artery is the bag of the pleura, which ascends between the scalena. Veins. Below the level of the artery, and separated from it by the an- terior scalenus muscle, lies the arch of the subclavian vein. Nerves. In front of the scalenus descends the phrenic nerve. Above the vessel, in the interval between the scalena, are placed the large cervical nerves ; and the trunk formed by the last cervical and first dorsal is inter- posed between the artery and the middle scalenus. Third part. Beyond the scalenus the artery is contained in the clavicu- lar })art of the posterior trijingular s])ace (p. 64), and is nearer the surface than in the rest of its course : this part of the vessel is inclosed in a tube of the dee]) cervical fascia, which it receives as it ])a.sses from between the scaleni. It is comj)aratively su])erficial whilst in the space before men- tioned, for it is covered only by the integuments, the ])latysma, and deep fascia, ; but near its termination the vessel gets under cover of the su|)i*a- scapular artery and vein, and the clavicle and subclavius muscle. In this SUBCLAVIAN ARTERY. 77 part of its course the artery rests on the surface of the first rib, which is interposed between it and tlie pleura. Veins. The arch of the subclavian vein is close to the artery, not being separated by muscle, but lies commonly at a lower level. The external jugular vein crosses it near the scalenus muscle ; and the suprascapular and transverse cervical branches, which enter the jugular, form sometimes a plexus over the third part of the artery. Nerves. The large cords of the brachial plexus are placed above and close to the vessel ; and the small nerve of the subclavius crosses it about the middle. Superficial to the cervical fascia lie the descending cutaneous branches of the cervical plexus. Peculiarities. The artery may spring as a separate truid^ from the arch of the aorta ; and in such a deviation the vessel takes a deeper place than usual to reach the scaleni muscles. It has been before said (p. 66) that the subclavian may be in front of the scalenus or in its fibres ; and that it may be placed one inch and a half above the level of the clavicle. Branches of subclavian. Usually there are four chief branches on the subclavian artery. Three branches arise from the first part of the arterial trunk ; one (vertebral) ascends to the head ; another (internal mammary) descends to the chest; and the remaining one (thyroid axis) is a short thick trunk, which furnishes branches inwards and outwards to the thyroid body and shoulder. These arise commonly near the scalenus muscle, so as to leave an interval at the origin free from offsets. This interval varies in length from half an inch to an inch in the greater number of cases ; and its extremes range from somewhat less than half an inch to an inch and three quarters. But in some instances the branches are scattered over the first part of the artery (Quain).^ The fourth branch (superior intercostal) arises beneath the anterior scalenus from the second part of the artery, and gives off the deep cervical branch ; a small spinal artery comes sometimes from this part of the trunk. If there is a branch present on the third part of the artery, it is com- monly the posterior scajmlar ; if more than one, this same branch with the external mammary ; and if more than two, an offset belonging to the thyroid axis will be added. The vertebral artery is generally the first and largest branch of the sub- clavian, and arises from the upper and posterior part. Ascending between the contiguous borders of the scalenus and longus colli muscles, this branch enters the aperture in the lateral mass of the sixth cervical vertebra, and is continued upwards to the skull through the foramina in the other cervical vertebras. Before the artery enters its aperture it is partly concealed by the internal jugular vein, and passes beneath the thyroid artery ; it is ac- companied by branches of the sympathetic nerve, and supplies small mus- cular offsets. Its course and distribution will be given afterwards. The vertebral vein issues with its accompanying artery, to which it is superficial in the neck, and is directed over the subclavian artery to join the subclavian vein ; it receives the deep cervical vein., and the branch that accompanies the ascending cervical artery. The internal mammary branch leaves the lower part of the subclavian • The student is referred for fuller information respecting the peculiarities of the vessel, and the practical applications to be deduced from them, to the original and valuable work on the Anatomy of the Arteries of the Human Body, by Richard Quail! , F.R.S. 78 DISSECTION OF THE NECK. artery, and coursing downwards beneath tlie clavicle, subclavius, and the right innominate vein, enters the thorax between the first rib and the bag of the pleura. As the artery disa[)pears in the chest, it is crossed (super- ficially) by the phrenic nerve. Tlie vessel is distributed to the walls of tiie chest and abdomen ; and its anatomy will be given with the dissection of those parts. Thyroid axis. Tliis is a short thick trunk (fig. 16 ) which arises from the front of the artery near the anterior scalenus muscle, and soon divides into three branches — one to the thyroid body, and two to the scapula. The suprascapular branch courses outwards across the lower part of the neck, behind the clavicle and subclavius muscle, to the superior costa of the scaj)ula, and entering the supraspinal fossa is distributed on the dorsum of that bone. Tlie connections of this artery are more fully seen in the dissection of the Back. The transverse cervical branch, usually larger than the preceding, takes a similar direction, though higher in the neck, and ends beneath the bor- der of the trapezius muscle in the superficial cervical and posterior scapular arteries. (“ Dissection of the Back.”) In its course outwards through the space containing the third part of the subclavian artery, this branch crosses the anterior scalenus, the phrenic nerve, and the brachial plexus. Some small offsets are supplied by it to the posterior triangular space of the neck. Though the transverse cervical artery supplies ordinarily the posterior scapular branch, there are many bodies in which it is too small to give origin to so large an offset. In such instances the diminished artery ends in the trapezius muscle ; whilst the posterior scapular branch arises sepa- rately from the third, or even the second part of the subclavian artery (Hg. Ki). ^ ^ The inferior thyroid branch is the largest offset of the thyroid axis. Directed inwards with a flexuous course to the thyroid body, the branch j)asses beneath the common carotid artery and the accompanying vein and nerves, and in front of the longus colli muscle and the recurrent nerve. At the lower part of the thyroid body it divides into branches which ramify in the under surface, and communicate with the superior thyroid, and its fellow, forming a very free anastomosis between those vessels. Near the larynx a laryngeal branch is distributed to that tube, and other offsets are furnished to the trachea. Tlie ascending cervical branch of the thyroid is directed upwards be- tween the scalenus and rectus capitis anticus major, and ends in branches to those muscles and the posterior triangle of tlie neck. Some small spinal offsets are conveyed along the spinal nerves to the cord and its membranes. The veins corres})onding with the branches of the thyroid axis have the following destination : those with the su})rasca])ular and transverse cervical arteries open into the external jugular vein. But the inferior thyroid vein begins in the thyroid body, and descends in front of the trachea, beneath the muscles covering this tube, to the innominate vein. The superior intercostal artery arises from the posterior part of the sub- clavian, and bends downwards over the neck of the first rib : its distribu- tion to the first two intercostal spaces will be seen in the thorax. Arising in common with this branch is the deep cervical artery (art. pro- funda cervicis). Analogous to the dorsal branch of an intercostal artery (Quain), it passes backwards between the transverse process of the last cervical vertebra and the first rib, lying internal to or beneath the two SUBCLAVIAN VEIN. 79 hinder scaleni muscles and the fleshy slips continued upwards from the erector spime, to end beneath the complexus muscle at the posterior part of the neck. A spinal hranch (Quain) is frequently given from the second part of the artery ; its offsets are continued into the spinal canal through the inter- vertebral foramina. The SUBCLAVIAN VEIN lias not the same limits as the companion artery, reaching only from the lower edge of the first rib to the inner border of the anterior scalenus. It is a continuation of the axillary vein, and ends by joining the internal jugular in the innominate trunk. Its course is arched below the level of the artery, from which it is separated by the scalenus. The anterior and external jugular join the subclavian vein outside the scalenus, and the vertebral vein enters it inside tliat muscle. Into the angle of union of the subclavian and jugular veins the right lymphatic duct opens (fig. 27,®) ; and at the like spot, on the left side, tlie large lymphatic or thoracic duct ends (fig. 27,®). The highest pair of valves in the sub- clavian trunk is placed outside tlie opening of the external jugular vein.^ It should be borne in mind that not unfre(piently the vein is as high in the neck as the third part of its companion artery ; and that the vein has been seen twice witli tlie artery beneath the anterior scalenus. The ANTERIOR PRIMARY BRANCHES OF THE CERVICAL NERVES Spring from the common trunks in the intervertebral foramina, and ajipear on the side of the neck between the intertransverse muscles. These nerves are eight in number, and are equally divided between the cervical and the brachial plexus ; the highest four being combined in the former, and the remaining nerves in the latter plexus. The nerves receive offsets of com- munication from the sympathetic at their beginning, and intermix by means of numerous branches near the spine. To this general statement some addition is needed for the first two nerves ; and their peculiarities will be noticed in Section 18 . Brachial Plexus. The four lower cervical nerves and part of the first intercostal are blended in this jilexus ; and a fasciculus is added to them from the lowest nerve entering the cervical plexus. Thus formed, the plexus reaches from the neck to the axilla, where it ends in nerves for the upper limb. Only the ])art of it above the clavicle can now be seen. In the neck the nerves have but little of a jdexiform disposition : they lie at first between the scaleni muscles, opposite the four lower cervical vertebrie, and have the following arrangement : — The fifth and sixth nerves unite near the vertebroe ; the seventh remains distinct as far as the outer border of the middle scalenus; and the last cer- vical and the piece of the first intercostal are blended in one trunk beneath the anterior scalenus; so that they make at first three cords. Near the attachment of the middle scalenus to the rib, the seventh nerve throws itself into the trunk of the united fifth and sixtli, and then there result two cords to the plexus: — the one (upper) formed by the fifth, sixth, and sev- enth cervical nerves; and the other (lower) by the eighth cervical and the first intercostal nerve. Tliese two trunks accompany the subclavian artery, lying to its acromial side, and are continued to the axilla where they are more intimately blended. Branches. The branches of the plexus may be classed into those above ' See a paper on the Valves in the Veins of the Neck in the Edin. Med. Journal, of Nov., 1856, by Dr. Struthers. 80 DTSSECTIOX OF THE NECK. the clavicle, and those below that bone. The highest set end mostly in muscles of tlie lower part of the neck and of the scapula; whilst the other set consist of the terminal branches, and are furnished to the upper limb, with which they will be referred to. Branches above the Clavice. The branch of the suhclavins mus- cle is a slender twig, which arises from the trunk formed by the fifth and sixth nerves, and is directed downwards over the subclavian artery to the under surface of the muscle; it is often united with the phrenic nerve at tlie lower part of the neck. Tlie branch of the rhomboid muscles springs from the fifth nerve in the substance of the middle scalenus, and perforates the fibres of that muscle; it is directed backwards beneatli the levator anguli scapuhe to its destina- tion. Branches are given usually from this nerve to the levator anguli scapulje. The nerve of the serratus (posterior thoracic nerve) is contained in the scalenus, like the preceding, and arises from the fifth and sixth nerves near the intervertrebral foramina. Piercing the fibres of the scalenus lower than the preceding branch, tlie nerve is continued behind the brachial plexus, and enters the serratus magnus muscle on the axillary surface. Branches of the scaleni and longus colli muscles. These small twigs are seen when the anterior scalenus is divided; they arise from the begin- ning of the trunks of the nerves. The suprascapular nerve is larger than either of the others. It arises near the subclavian branch from the cord of the plexus formed by the fifth and sixth nerves. Its destination is to the muscles on the dorsum of tlie scapula, and it will be dissected with the arm. Occasionally an offset from the fifth cervical trunk joins the phrenic nerve on the anterior scalenus muscle. The CERVICAL PLEXUS is formed by the first four cervical nerves. kSituate at the upper part of the neck, it lies beneath the sterno-mastoid muscle, and on the middle scalenus and the levator anguli scapulie. It differs much from the brachial plexus, for it resembles a network more than a bundle of large cords. The following is the general arrangement of the nerves in the plexus : Each nerve, except the first, divides into an ascending and a descending branch, and these unite with similar jiarts of the contiguous nerves, so as to give rise to a series of arches. From these loops or arches the different branches arise: — The branches are sujierficial and deep. The superficial set has been described with the triangular space of the neck, as consisting of ascending and descending (p. 66). The ascending branches may be now seen to spring from the union of the second and third nerves; and the descending, to take origin from the loop between the third and fourth nerves. The deep set of branches remains to be examined : they are muscular and com- municating, and may be arranged into an internal and an external series. Internal Series The phrenic or muscular nerve of the diaphragm (fig. 16) is derived from the fourth, or third and fourth nerves of the plexus ; and it may be joined by a fasciculus from the fifth cervical nerve. Descending obliquely on the surface of the anterior scalenus from the outer to the inner edge, it enters the chest in front of the internal mammary artery, but behind the subclavian vein, and traverses that cavity to reach the diaphragm. At the lower part of the neck the phrenic nerve is joined by a filament of the sympathetic, and sometimes by an offset of the nerve of the subclavius muscle. CERVICAL PLEXUS. 81 On the left side the nerve crosses over the first part of the subclavian artery. The branches communicating with the descendens noni are two in num- ber. One arises from the second, and the other from the third cervical nerve ; they are directed inwards over the internal jugular vein, and com- municate in front of the carotid slieath with the descending muscular branch (descendens noni) of the hypoglossal nerve. Sometimes these nerves pass under the jugular vein. Muscidar branches are furnished to the anterior recti muscles ; they arise from the loop between the first two nerves, and from the trunks of the other nerves close to the intervertebral foramina. Some connecting branches pass from the loop between the first two nerves, and unite with the sympathetic and some cranial nerves near the base of the skull: these will be afterwards described. External or Posterior Series. Muscidar branches are given from the second nerve to the sterno-mastoideus ; from the third nerve to the levator anguli scapulae ; and from the third and fourth nerves to the trapezius. Further, some small branches sup[)ly the substance of the mid- dle scalenus. Connecting branches with the spinal accessory nerve exist in three places. First, in the sterno-mastoid muscle; next, in the })Osterior trian- gular space; and lastly, benetath the trapezius. Tlie union with the branches distributed to the trapezius has the appearance of a plexus. The COMMON CAROTID ARTERY is the leading vessel for the supply of blood to the neck and head (tig. 16 , ®). The origin of the vessel differs on opposite sides of tlie body, beginning at the lower part of the neck on the right, and in the thorax on the left side. The right vessel commences opposite the sterno-clavicular articulation in the bifurcation of the innominate artery, and ends at the upper border of the thyroid cartilage by dividing into the external and internal carotid. The course of the artery is along the side of the trachea and larynx, gradu- ally diverging from the vessel on the opposite side in consequence of the increasing size of the larynx; and its position wdll be marked by a line from the sterno-clavicular articulation to a point midway between the angle of the jaw and the mastoid process. Contained in a sheath of cervical fascia with the internal jugular vein and the pneumo-gastric nerve, the carotid artery has the following connec- tions with the surrounding parts : — As high as the cricoid cartilage the vessel is deeply placed, and is concealed by the common coverings of the skin, platysma, and fasciae, and by the muscles at the lower part of the neck, viz., sterno-mastoid (sternal origin), sterno-hyoid, omo-hyoid, and sterno-thyroid. But above the circoid cartilage to its termination the artery is less deep, being covered only by the sterno-mastoid with the common investments of the part. The vessel rests mostly on the longus colli muscle, but close to its ending on the rectus capitis anticus major. To the inner side of the carotid lie the trachea and larynx, the oesophagus and pharynx, and the thyroid body, the last overhanging the vessel by the side of the larynx. Along the outer side of the carotid sheath is a chain of lymphatic glands. Veins. The large internal jugular lies on the outer side and close to the carotid at the up[)er end, but separated from it below by an interval of about half an inch : on the left side the vein is over the artery below, as will be afterwards seen. One or two upper thyroid veins and their branches 6 82 DISSECTION OF THE NECK. cross the upper part of the arterial trunk ; and opposite the thyroid body another small vein (middle (thyroid) is directed back over the vessel. Near the clavicle the anterior jugular vein passes out under the sterno- mastoid : it is su|)erficial to the artery, and separated from it by the sterno- hyoid and thyroid muscles. Arteries. Offsets of the upper thyroid artery descend over the top of the sheath ; and the inferior thyroid crosses under it below the level of the cricoid cartilage. Nerves. Tlie descendens noni lies in front of the sheath, crossing from the outer to the inner side, and is joined there by the cervical nerves. The pueumogastric lies within the sheath, behind and between the artery and the vein. The sympatlietic cord and branches rest on the spine behind the sheath. All the nerves above mentioned have a longitudinal direction; but the inferior laryngeal or recurrent crosses obliquely inwards behind the sheath towards the lower end of the artery. Branches of carotid. As a rule, the common carotid artery does not furnish any collateral branch, though it is very common for the superior thyroid to sowing from its upper end. At the terminal bifurcation into the two carotids tlie artery is slightly bulged. The INTERNAL JUGULAR VEIN extends upwards to the base of the skull, but only the part of it that accompanies the common carotid is now seen. Placed behind or external to its artery, the vein ends below by uniting Muth the subclavian in the innominate vein. Its proximity to the carotid is not equally close throughout, for at the lower part of the neck the vein inclines backwards, leaving a space between it and the artery, in which the vagus nerve is seen about midway between the two. Sometimes the vein is su])erticial to the carotid, as on tlie left side. The lower part of the vein is marked by a dilatation or sinus. Near its ending it becomes contracted, and is provided witli a pair of valves (Struthers). In this part of its course tlie vein receives the superior and middle thy- roid branches. Peculiarities of the carotid. The origin of the artery on the right side may be above or below the point stated. Mention has been made of the difference in the place of bifurcation, and of the fact that the common carotid may not be divided into two (p. 70). Instead of one, there may be two trunks issuing from beneath the hyoid muscles. Dissection. The dissector may next trace out completely the trunk of the external carotid (fig. 17), and follow its branches until they disappear beneath different parts. Afterwards he may sejiarate from one another the digastric and stylo-hyoid muscles, which cross the carotid ; and may define their origin and insertion. The DIGASTRIC MUSCLE (fig. 15®) coiisists of two fleshy bellies, united by an intervening tendon, whence its name. The posterior, the larger of the two, arises from the groove beneath the mastoid process ; whilst the anterior belly is fixed on the side of the symjihysis of the lower jaw. From these attachments the fibres are directed to the intervening tendon, which is surrounded by fibres of the stylo-hyoideus, and is united to its fellow, and to the body and part of the great cornu of the os hyoides by an aponeurotic expansion. The arch formed by the digastric is superficial, exce})t at the outer end, where it is beneath the sterno-niastoid and splenius muscles. The poste- rior belly covers the carotid Vessels and tlie accom])anying veins and DISSECTION OF THE NECK. 83 nerves ; and is placed across the anterior triangular space of the neck in the [)Osition of a line from the mastoid [)rocess to a little above tlie hyoid bone : along its lower border lie the occij)ital artery and the hypoglossal nerve ; the former passing backwards, the latter forwards. The anterior belly rests on the mylo-hyoid muscle. Tlie muscle forms the lower boundary of a space between the jaw and the base of the skull, which is subdivided into two by the stylo-maxillary ligament. In the posterior portion are contained the parotid gland ('”), and the vessels and nerves in connection with it (p. 41) ; in the anterior, are the submaxillary gland ("), with the facial and submental vessels, and deeper still, the muscles between the chin and the hyoid bone. Action. The lower jaw being movable, the muscle depresses that bone and opens the mouth. If the jaw is fixed, the two bellies acting will ele- vate the hyoid bone. It is supposed that the posterior belly may assist in moving back the head when the jaw is fixed. The STYLO-HYOID MUSCLE is thin and slender, and has the same posi- tion as the posterior belly of the digastric. It arises from the outer sur- face of the styloid process, near the base, and is inserted into the body of the os hyoides. The muscle has the same connections as the posterior belly of the digas- tric ; and its fleshy fibres are usually perforated by the tendon of that muscle. In some bodies the stylo-hyoideus is absent. Action. This muscle elevates the os hyoides pre[)aratory to swallowing, and checks, with the posterior belly of the digastric, the too forward move- ment of that bone by the other elevators. The HYPOGLOSSAL NERVE (ninth cranial) appears in the anterior tri- angle at the lower edge of the digastric muscle, where it hooks round the occipital artery; it is then directed forwards to the tongue below that muscle, and disappears in front beneath the mylo-hyoideus. In this course the nerve passes over the two carotids ; and near the cornu of the os hyoides it crosses also the lingual artery, so as to become higher than the vessel. From this part arise the descendens noni branch, and a small muscular offset to the thryo-hyoideus. The descending branch (ram. descend, noni) leaves the trunk of the hypoglossal on the outer side of the carotid artery, and descends on the front of (sometimes in) the sheath of the vessel to about the middle of the neck, where it is joined by the communicating branches of the cervical nerves. After the union of tlie spinal nerves, offsets are supplied to the depressor muscles of the os hyoides, viz., omo-hyoid (both bellies), sterno- hyoid, and sterno-thyroid : sometimes another offset is continued to the thorax, where it joins the phrenic and cardiac nerves. The connection between the descendens noni and the spinal nerves is formed by two or more cross filaments, so as to construct an arch with the concavity upwards ; and an interchange of fibrils between the two nerves is supposed to take place. The EXTERNAL CAROTID ARTERY (fig. 17, d) Springs from the bifurca- tion of the common carotid at the upper border of the thyroid cartilage, and furnishes branches to the neck, the face, and the outer parts of the head. From the place of origin it ascends in front of the mastoid process, and ends near the condyle of the jaw in the internal maxillary and temporal branches. The artery lies at first to the inner side of the internal carotid, but 84 DISSECTION OF THE NECK. it afterwards becomes superficial to that vessel ; and its direction is some- what arched forwards, though the position would be marked sufficiently by a line from the front of the meatus of the ear to the cricoid cartilage. At first the external carotid is overlaid by the sterno-mastoideus, and by the common coverings of the anterior triangular space, viz., the skin, and the superficial and deep fascia with the platysma. But above the Fig. 17. External Carotid and its Superficial Branches (“ Anatomy of the Arteries,” Quain). a. Common carotid. b. Internal jugular vein. c. Internal carotid. d External carotid. e. Upper thyroid branch. /. Lingual. g. Facial. h. Internal maxillary. i. Superficial temporal. m. Supra orbital. n. External nasal. o. Angular bi’anch of facial. p. Lateral nasal. r. Superior coronary. s. Inferior coronary. t. Inferior labial. u. Submental artery. level of a line from the mastoid process to the hyoid bone, the artery is crossed by the digastric and stylo-hyoid muscles, and still higher the parotid gland conceals it. At its beginning the artery rests against the pharynx ;* but above the angle of the jaw it is placed over the styloid process and stylo-pharyngeus muscle, which separates it from the internal carotid. To the inner side of the vessel at first is the pharynx ; and still higher, are the ramus of the jaw and the stylo-maxillary ligament. EXTERNAL CAROTID ARTERY. 85 Veins. There is not any companion vein with tlie external carotid as witli most arteries ; bnt sometimes a vein, formed ])y the union of the tem- j)oral and internal maxillary branches (]). 42), will accompany it. Near the beginning it is crossed by the facial and lingual branches joining the internal jugular vein ; and near the ending the external jugular vein lies over it. Nerves are directed fi'om behind forwards over and under the artery. At the lower border of the digastric muscle the hy}X)glossal lies over the vessel, and near the ending the ramifications of the facial nerve are super- ficial to it. Three nerves lie beneath it : beginning below, the small ex- ternal laryngeal ; a little higher, the superior laryngeal ; and near the base of the jaw, the glosso-pharyngeal. The branches of the external carotid are numerous, and are classed into an anterior, posterior, and ascending set. The anterior set comprise branches to the thyroid body, the tongue, and the face, viz., superior thy- roid, lingual, and facial arteries. In the ])OSterior set are the occipital and ]msterior auricular l)ranches. And the ascending set include the as- cending pharyngeal, tem[)oral, and internal maxillary arteries. Besides these, the carotid gives other branches to the sterno-mastoid muscle and the ])arotid gland. The origin of the branches of the carotid may be altered by their closer aggregation on the trunk. The usual number may be diminished by two or more uniting into one ; or the number may be increased by some of the secondary offsets being transferred to the parent trunk. Directions. All the branches, except the ascending pharyngeal, lingual, and internal maxillary, may be now examined ; but those three will be described afterwards with the regions they occupy. The superior thyroid artery (c) arises near the cornu of the os hyoides, and passes beneath the omo-hyoid, sterno-hyoid, and sterno-thyroid mus- cles to the thyroid body, to which it is distributed on the anterior aspect. This artery is superficial in the anterior triangle, and furnishes offsets to the lowest constrictor and the muscle beneath which it lies, in addition to the following named branches : — a. The hyoid branch is very inconsiderable in size, and runs inwards below the hyoid bone : it supplies the muscles attached to that bone, and anastomoses with the vessel of the ojiposite side. b. A branch for the sterno-mastoid mnscle lies in front of the sheath of the common carotid artery, and is distributed chiefly to the muscle from which it takes its name. c. The laryngeal branch pierces the membrane between the hyoid bone and the thyroid cartilage, with the superior laryngeal nerve, and ends in the interior of the larynx. d. A small crico-thyroid branch is placed on the membrane between the cricoid and the thyroid cartilage, and communicates with the corresponding artery of the opposite side, forming an arch. The snperior thyroid vein commences in the larynx and the thyroid body, and crosses the end of the common carotid artery to open into the internal jugular vein. The facial artery {g') arises above the lingual, and is directed u])wards over the lower jaw to the face. In the neck the artery passes beneath the digastric and stylo-hyoid muscles, and is afterwards lodged on the sub- maxillary gland, on which it makes a sigmoid turn. Its anatomy in the 86 DISSECTION OF THE NECK. face lias been examined (p. 40). From the cervical part branches are given to the pharynx, and to the structures below the jaw, viz. : — a. The inferior 'palatine branch ascends to the pharynx beneath the jaw, passing between the stylo-glossus and stylo-pharyngeus muscles, and is distributed to the soft palate, after furnishing a branch to the tonsil. This branch frequently arises from the ascending pharyngeal artery. h. The tonsillar branch is smaller than the preceding, and passes be- tween the internal pterygoid and stylo-glossus muscles. 0[)})Osite the ton- sil it perforates the constrictor muscle, and ends in offsets to that body. c. Glandular branches are siqiplied to the submaxillary gland from the part of the artery in contact with it. d. The submental branch arises near the inferior maxilla, and courses forwards on the mylo-hyoideus to the anterior belly of the digastric muscle, where it ends in offsets : some of these turn over the jaw to the chin and lower lip ; and the rest supply the muscles between the jaw and the hyoid bone — one or two perforating the mylo-hyoideus and anastomosing with the sublingual artery. The /arm/ vein (p. 40) joins the internal jugular. In the cervical part of its course it receives branches corresponding with the offsets of the artery. It often throws itself into the temporo-maxillary trunk. The occipital artery is of considerable size, and is destined for the back of the head. It arises from the carotid opposite the facial branch, near the lower border of the digastric muscle, and ascends to the inner part of the mastoid process of the temporal bone. Next it turns horizontally backwards on the occij)ital bone, passing above the transverse process of the atlas ; and finally becomes cutaneous near the middle line (p. 21). In the neck this artery passes beneath the digastric muscle and a part of the parotid gland ; and crosses over the internal carotid artery, the jugular vein, and the spinal accessory and hypoglossal nerves. The only offset from the artery in the front of the neck is a small poste- rior meningeal branch: this ascends along the internal jugular vein, and enters the skull by the foramen jugulare (p. 30). The branches at the back of the neck wdll be afterwards seen. The occipital vein begins at the back of the head (p. 21), and has the same course as the artery ; it communicates wdth the lateral sinus through the mastoid foramen, also wdth the diploic veins, and coalesces with the in- ternal (sometimes the external) jugular vein. The posterior auricular artery is smaller than the preceding branch, and takes origin above the digastric muscle. Betw'een the ear and the mastoid process, it divides into two branches for the ear and occiput (p. 21). A small branch, stylo-mastoid enters the foramen of the same name, and siq)plies the tympanum of the ear. The vein wdth the artery receives a stylo mastoid branch, and terminates in the trunk formed by the tem})oral and internal maxillary veins. The temporal artery {%) is in direction the continuation of the external carotid trunk, and is one of the terminal branches of that artery. As- cending under the parotid gland it divides on the tem})oral fascia into an- terior and })osterior branches, about tw'o inches above the zygoma ; these are distributed to the front and side of the head (p. 21). The trunk of the artery gives offsets to tlie surrounding ])arts, viz. : — a. Parotid branches are furnished to the gland of the same name. Articular twigs are supplied to the articulation of the low'er jaw^ ; and MASSETER MUSCLE. 87 other muscAiIar branches enter tlie masseter. Some anterior auricular offsets are distributed to the pinna and meatus of the external ear. h. The transverse facial branch quits the temporal artery opposite the condyle of the jaw, and is directed forwards over the masseter muscle (p. 41) ; on the side of the face it supplies the muscles and integuments, and anastomoses with the facial artery. c. The middle temporal branch arises just above the zygoma, and pierces the temporal aponeurosis to enter the substance of tlie temporal muscle : it anastomoses with branches of* the internal maxillary artery. d. A small branch of tlie temporal artery is likewise found between the layers of the temporal fascia ; this anastomoses with an offset of the lachry- mal. Tlie temporal vmi commences on the side of the head (p. 21) and is con- tiguous to its comjianion artery. Near the zygoma it is joined by the middle temporal vein ; next it receives branches which are companions of the offsets of the artery ; and it ends by uniting with the internal maxil- lary vein. Directions. The lower part of the neck will not be used again for some days, so that the dissector may stitch together the flaps of skin, when he has applied salt to preserve it. Section VI. PTERYGO-MAXILLARY REGION. In this region are included the muscles superficial to and beneath the ramus of the lower jaw, together with the articulation of that bone. In contact with the muscles (pterygoid) beneath the jaw, are the internal maxillary bloodvessels, and the inferior maxillary trunk of the fifth nerve. Dissection. The masseter muscle, which is superficial to the bones, has been partly laid bare in the dissection of the facial nerve. To see it more fully the branches of the facial nerve, and the transverse facial artery should be cut through, and turned backwards off the face. A little cleaning will suffice to define the origin and insertion of the muscle. Should there be any tow or cotton wool in the mouth let it be removed. The MASSETER (fig. 6, ^®) is partly a))oneurotic at the upper attachment. It arises from all tlie lower border of the zygomatic arch, extending for- wards to the upper jaw ; and from the inner surface of the arch by fine fleshy fibres. Most of the fibres are inclined down and somewhat back, and are inserted into the outer surface of the coronoid process, ramus, and angle of the lower jaw ; but a few are fixed into the contiguous part of the body of the bone as far as the second molar tooth. Some of the hinder and deeper fibres are inclined downwards and forwards across the others. The lower part of the masseter is subcutaneous, but the upper is partly concealed by the parotid gland (socia parotidis), and is crossed by Sten- son’s duct, and by the transverse facial vessels and the facial nerve. The anterior border projects over the buccinator muscle, and a quantity of fat resembling that in the orbit is found beneath it. The muscle covers the 88 DISSECTION OF THE PTERYGOID REGION- ramus of the jaw, and the masseteric branches of nerve and artery enter- ing it at the under surface. Action. It raises the lower jaw with the internal pterygoid in the mas- tication of the food. Dissection. To lay bare the temporal muscle to its insertion, the follow- ing dissection may be made : The temporal fascia is to be detached from the upper border of the zygomatic arch, and to be removed from the sur- face of the muscle. Next, the arcli of the zygoma is to be sawn through in front and behind, so as to include all its length ; and is to be thrown down (without being cut off) with the masseter muscle still attached to it, hy separating the fibres of that muscle from the ramus of the jaw. In detacliing the masseter muscle, its nerve and artery, which pass through the sigmoid notch, will be found. The surface of the temporal muscle may be then cleaned ; and to ex- pose its insertion and deep origin, let the coronoid process be sawn oft‘ by a cut jmssing from the centre of the sigmoid notch nearly to the last molar tooth, so as to include the whole insertion of the muscle. Before sawing tlie bone let the student find and separate from the muscle the buccal ves- sels and nerve issuing from beneath it. Lastly, the coronoid process should be raised and the fat removed, in order that the lower fibres of the tem- poral muscle, and their contiguity to the external pterygoid close below them, may be observed. The temporal muscle (fig. 18, takes its origin from the whole of the temporal fossa (p. 20), reaching up to the semicircular line on the side of the skull, and downwards to the crest on the outer aspect of the great wing of the sphenoid bone.- From this extensive attachment, as well as from the fascia over it, the fibres converge to a superficial tendon, which is inserted into the inner surface of the coronoid process, as well as into a groove on the same process which reaches from the a[)ex to near the last molar tooth. Behind the posterior border of the tendon are the masseteric vessels and nerve, and in front of it the buccal vessels and nerve : the last nerve per- forates occasionally some of the fibres of the muscle. Action. All the fibres contracting the muscle will raise the mandible and press it forcibly against the upper jaw ; but the hinder fibres may re- tract the lower jaw after it has been moved forwards by the external ptery- Dissection. For the display of the pterygoid muscles (fig. 18), it will be necessary to remove a })iece of the ramus of the jaw. But the greater part of the temi)oral muscle is to be first detached from the subjacent bone with the handle of the scalpel, and the deep temporal vessels and nerves are to be sought in its fibres. A piece of the ramus is next to be taken away by sawing across the bone close to the condyle, and again close above the dental foramen ; and to make the dental vessels and nerve in contact with its inner surface secure from injury, the handle of the scal[)el may be inserted between them and the bone, and carried downwards to their entrance into the foramen. The masseteric artery and nerve are liable to be cut in sawing the bone ; sliould these be divided, turn them upwards for the present, and afterwards tie together the ends. After the loose piece of bone has been removed, and the subjacent parts freed from much fat, the pterygoid muscles will ai)pear, — the external (■^) being directed outwards to the condyle of the jaw, and the internal (^), which is parallel in direction to the masseter, being inclined to the angle POSITION OF VESSELS AND NERVES. 89 of the jaw. In removing the fatty tissue, the student must he careful not to take away the thin lateral ligament, which lies on the internal pterygoid muscle beneath the ramus. Position of vessels. Crossing inwards over the external pterygoid muscle, is the internal maxillary artery, which distributes offsets upwards Superficial View op the Pterygoid Region (Quain’s “ Arteries”). 1. Temporal muscle. 6. Common carotid dividing into external and 2. External pterygoid. internal trunks. Internal pterygoid. 8. Internal maxillary artery (beneath the 4. Buccinator. pterygoid instead of over it) and its 5. Digastric and stylo-hyoid muscles cut and branches. thrown back. The nerves are omitted in this woodcut. and downwards : sometimes the artery will be placed beneath tlie muscle. The veins with the artery are large and plexiform : and may be taken away. Position of nerves. Most of the branches of the inferior maxillary nerve appear in this dissection. Thus, issuing from beneath tlie lower border of the external pterygoid are the large dental and gustatory nerves, the latter being the more internal of the two; and coming out behind the joint of the jaw is the auriculo-temporal nerve. Appearing between the upper border of the muscle and the cranium, are the small masseteric and deep temporal nerves. The buccal branch of the nerve perforates the fibres of the same muscle near the inner attachment. Brandies of the above- mentioned artery accompany the nerves. Coursing along the posterior part .of the upper jaw, is the small posterior dental nerve with an artery. Between the jaws is the whitish narrow band of the jiterygo-maxillary ligament, to which the buccinator and superior constrictor muscles are connected. Tlie EXTERNAL PTERYGOID MUSCLE (fig. 18, extends alinost horizon- tally from the zygomatic fossa to the neck of the lower jaw. Its origin is 90 DISSECTION OF THE PTERYGOID REGION. from the outer surface of the great wing of tlie sphenoid bone below the crest, and from the outer surface of the external pterygoid plate. The fibres are directed outwards and somewhat backwards, those attached to the upper margin of the spheno-maxillary fissure forming at first a separate bundle, and are inserted into the hollow in front of the neck of the lower jaw bone, and into the interarticular fibro-cartilage of the joint. Externally the pterygoid is concealed by the temporal muscle and the lower jaw, and the internal maxillary artery lies on it. By the deep sur- face it is in contact with the inferior maxillary nerve, with a plexus of veins, and with the internal lateral ligament of the joint of the jaw. The parts in contact with the borders of the muscle have been enumerated before. Sometimes the slij) of the muscle, which is attached to tlie margin of the spheno-maxillary fissure and the root of the external pterygoid plate, is described as a separate head with an insertion into the interarticular car- tilage. Action. If both muscles act the jaw is moved forwards, so that the lower dental arch is placed in front of the upper, and the grinding teeth are rubbed togetlier in an antero-posterior direction. In order that the lower front teetli may be able to pass the others the jaw is depressed. One muscle contracting (say the right), tlie condyle of the same side is drawn inwards and forwards, and the grinding teeth of the lower jaw are moved horizontally to the left across tliose of the upper. By the alternate action of the two muscles the trituration of the food is effected. The INTERNAL PTERYGOID MUSCLE (fig. 18, is nearly parallel to the ramus of the jaw, and its fibres are longer than those of the preceding muscle. Arising in the pterygoid fossa, and chiefly from the inner sur- face of the external pterygoid plate, the muscle is further attached below, outside the fossa, to the outer surface of the tuberosity of the palate bone, and to the tuberosity of the upper jaw bone. The fibres descend to be inserted into the angle, and into the inner surface of the ramus of the jaw as high as the inferior dental foramen. On the muscle are placed the dental and gustatory nerves, the dental artery, and the internal lateral ligament of the jaw. The deep surface is in relation below with the superior constrictor, and at its origin with the tensor palati muscle. Action. From the direction and attachment of the fibres the muscle will unite with the masseter in elevating the jaw. Directions. Before proceeding further in the dissection, the student may learn the anatomy of the articulation of the lower jaw. Temporo-maxillary articulation. In this articulation are com- ])ined the condyle of the jaw and the anterior part of the glenoid fossa of the temi)oral bone ; but the osseous surfaces are not in contact, for a piece of fibro-cartilage with two synovial sacs is inter})Osed between them. The bones are retained in apposition mostly by the strong muscles of the lower jaw ; but the following ligaments serve to unite them. Capside. This is a thin fibrous tube inclosing the bones, and is wider above than below. By the ujiper end it is fixed around the articular • surface of the temporal bone in front of the Glaserian fissure ; and it is in- serted below around the condyle of the lower jaw. The space in the interior is divided into two, up])er and lower, by a juece of fibro-cartilage, which is united to the capsule by its circumference. The external lateral is a short ligamentous band, being but a part of the TEMPORO-MAXILLARY JOINT. 91 capsule, which is attached above to the tubercle at the root of the zygoma, and below to the outer side of the neck of the inferior maxilla. The internal lateral ligament (tig. 19, is a long, thin, membranous band, which is not in contact with the joint. Superiorly it is connected to a projection inside the glenoid fossa, which consists of the spinous pro- cess of the sphenoid and tlie vaginal process of the temporal bone ; and interiorly it is inserted into the orifice of the dental canal in the lower jaw. The ligament lies between the jaw and the internal ])terygoid ; and its origin is concealed by the external pterygoid muscle. Between the liga- ment and the jaw the internal maxillary artery intervenes. Fig. 19. Ligaments of the Jaw — an inner view (Bourgery and Jacob). 1. Internal lateral ligament. 2 Stylo-maxillary. 3. Stylo-maxillary ligament. Fig. 20. A VIEW OF THE INTERIOR OF THE COMPOCNI) Temporo-maxillary Joint (Bourgery and Jacob). 4. Interarticular fibro-cartilage — the dark inter- vals above aud below are the hollows con- taining the synovial membranes. Dissection. After the external lateral ligament and tlie capsule of the joint have been examined, an interarticular fibro-cartilage, with a hollow above and below it, will be exposed by taking away the capsule on the outer side (fig. 20). The interarticular fibro-cartilage (fig. 20, is adapted to the surfaces of the bones. It is elongated transversely, is thinner in the centre than at the margins, and an aperture is sometimes present in the middle. The U})per surface fits into the glenoid fossa, being concavo-convex from before backwards, and the lower is moulded on the convexity of the condyle of the jaw. By the circumference it is connected with the capsule and the external lateral ligament ; and in front the external pterygoid muscle is attached to it. This interarticular pad allows greater freedom of movement in the joint without dislocation ; diminishes the injurious effect of pressure ; and deacU ens the sound of the jaw striking the skull. Two synovial membranes are ]U'esent in the articulation — one above, and one below the fibro-cartilage. The lower one is the smaller of the two. Another structure — the stylo-maxillary ligament (fig. 20, is described as a uniting band to tliis articulation. It is a process of the deep cervical fascia, which extends from the styloid process to the hinder part of the ramus of the jaw : it gives attachment to tlie stylo-glossus muscle, and separates the parotid and submaxillary glands. 92 DISSECTION OF THE PTERYGOID REGION. Articular surfaces of the hones. The lower jaw possesses a thin narrow condyle, which is elongated transversely, and directed backwards and inwards. On the temporal bone is a narrow deep articular hollow (glenoid fossa), which is lengthened from without in, and is placed in front of the Glaserian fissure. In front of this is a prominence of bone (transverse root of the zygomatic process), which is convex from before back and rather hollowed from side to side. Movements of the joint. This condyloid articulation is provided with an up and down, a to and fro, and a lateral movement. In depressing the jaw., as in opening the mouth, the articular condyle moves forwards till it is jdaced under the convexity at the fore part of the articular hollow, but the interposed concave fibro-cartilage gives security to the joint. Even with this provision, a slight degree more of sudden motion throws the condyle off the prominence of the temporal bone into the zygomatic fossa, and gives rise to dislocation. In this movement the fore and lateral parts of the capsule are made tight; and the fibro-cartilage is drawn forwards with the condyle by the external pterygoid muscle. When the jaiv is elevated and the mouth closed, the condyle and the fibro-cartilage glide back into the glenoid fossa. In this position the jaw is placed in the state of greatest security against dislocation. The ligaments and the surrounding muscles, which were stretched in the previous movement, are then set at rest. During the horizontal motion forwards and backwards the condyle is moved successively to the front and back of the temporal articular surface; and the lower jaw is slightly de[)ressed, in order that the fore teeth in the upper dental arch should not im[)ede those of the lower. By turns the front and back of the capsule will be stretched; and the fibro-cartilage always follows the condyle of the jaw, even in dislocation. Too great motion forwards will be prevented by the coronoid process of the jaw striking against the zygomatic arch; and that backwards, by the meeting of the condyle and the auditory process of the os temporis. Lateral horizontal movement puts the jaw first to one side and then to the other. When the jaw is forced to the left side, the right condyle sinks into its articular hollow, whilst the left is projected ; and the grinding teeth of the lower dental arch are moved to the left across those of the upper. By the alternate action to 0 })posite sides the food is triturated. The inner part of the capsule on the right, and the outer part on the left side, will be put on the stretch when the jaw is carried to the left of the middle line ; and the opposite. With old edentulous jaws the capsule is much enlarged, and permits the condyle to wander backwards behind the Glaserian fissure. Without this provision the altered lower jaw would not meet the u])per to crush the food. Dissection. The condyle of the jaw is next to be disarticulated, the external j)terygoid muscle being still uncut; and it with the attached mus- cle is to be drawn forwards so as to allow the fifth nerve to be seen. Whilst cutting through the joint capsule, the dissector must be careful of the auriculo-temponil nerve close beneath (fig. 21). On drawing forwards the pterygoid muscle, and removing some fat, the dissector will find tlie trunk of the inferior maxillary nerve. All the small muscular branches of the nerve before noted should be traced to the trunk in the foramen ovale of the sphenoid bone. Tlie auriculo-temporal branch INTERNAL MAXILLARY ARTERY. 93 should be followed backwards with care behind the articulation, and tlie dental and gustatory nerves beneath the muscle should be cleaned. The small chorda tym[)ani is then to be found joining the posterior part of the gustatory nerve near the skull. Tlie middle meningeal artery is to be sought beneath the external ptery- goid. Sometimes the trunk of the internal maxillary artery lies beneath that muscle, and in sucli case, it and its branches are to be traced out. The INTERNAL MAXILLARY ARTERY (fig. 17, //) is oiie of the terminal branches of the external cai’otid, and takes a winding course beneath the lower jaw and the temporal muscle to the spheno-maxillary fossa, where it ends in branches for the face, the interior of the nose, and the palate and pharynx. At first the artery is directed inwards beneath the jaw, between that bone and tlie internal lateral ligament of the joint, and crosses the dental nerve. Next, the vessel winds over the external pterygoid muscle, being placed between it and the tem[)oral muside. And lastly, tlie artery enters the spheno-maxillary fossa between the [irocesses of origin of the external pterygoid. The course of the artery is sometimes beneath, instead of over the external pterygoid : in such a state the artery gains the spheno-maxil- lary fossa by coming upwards through the origin of the muscle, as in the woodcut. The branches of this artery are very numerous, and are classed into three sets: thus one set arises beneath the jaw; another between the mus- cles ; and another in the S[)heno-niaxillary fossa. Two branches, viz., the inferior dental and middle meningeal, leave the internal maxillary artery whilst it is in contact with the ramus of the jaw. The inferior dental branch descends between the internal lateral liga- ment and the jaw, and enters the foramen on the inner surface of the ramus, along with the dental nerve: it supplies the teeth, and ends in the lower part of the face. As this artery is about to enter the foramen it furnishes a small twig, mylo-hyoid branch, io the muscle of that name; this is conducted by a groove on the inner surface of the bone, in company with a branch from the dental nerve, to the superficial surface of the mylo-hyoid muscle, where it anastomoses with the submental artery. The great meningeal artery is the largest branch, and arises opposite the preceding. It ascends beneath the external pterygoid muscle, and (oftentimes) between the roots of the auriculo-temporal nerve; crossing the internal lateral ligament, it enters tlie skull through the foramen spino- sum of the splienoid bone. Wlien in tlie skull the artery ascends to the vertex of the head, and supjdies the bone and the dura mater (p. 29). Before the meningeal artery enters the skull, it furnishes the following small branches : — a. The tympanic branch (inferior) passes into the tympanum through the Glaserian fissure, and is distributed to the membrana tympani and that cavity. b. A deep auricidar branch arises with the former or separately enters the meatus through the cartilage, or between this and the bone, and rami- fies in the meatus and on the membrana tympani. c. The small meningeal branch begins near the skull, and courses through the foramen ovale with the inferior maxillary nerve; it ramifies in the dura mater in the middle fossa of the skull. Another small branch springs from the dental artery or the internal 94 DISSECTION OF THE PTERYGOID REGION. maxillmy trunk, and accompanying the gustatory nerve, ends in the cheek and the mucous membrane of the mouth. Tlie brandies from the second part of tlie artery, viz., whilst it is between the temporalis and pterygoideus externus are distributed to the temporal, masseteric, buccal, and pterygoid muscles. Tlie deep temporal arteries are two in number (anterior and posterior) ; and each occupies tlie part of the temporal fossa indicated by its name. They ascend beneath the temporal muscle, and anastomose with the super- ticial temfioral artery: the anterior communicates, through the malar bone, with branches of the lachrymal artery. When the parent trunk has the unusual position beneath the pterygoid, the anterior branch lies under that muscle, instead of over it. The masseteric artery is directed outwards with the nerve of the same name behind the tendon of the temporal muscle ; and passing through the sigmoid notch, enters the under surface of the masseter muscle. Its branches anastamose with the other offsets to the muscle from the external carotid trunk. The buccal branch quits the artery near the upper jaw, and in the un- usual position of the artery it may perforate the fibres of the pterygoid ; it descends beneath the coronoid process with its companion nerve, and is distributed to the buccinator muscle, tlie cheek, and the side of the face, joining the branches of the facial artery. 'V\\e pterygoid branches are uncertain in their position; whether derived from the trunk or some of the branches of the internal maxillary, they enter both pterygoid muscles. Of the branches that arise from the artery when it enters the spheno- maxillary fossa, only one, the superior dental, will be now described. The remainder will be examined with the superior maxillary nerve and Meckel’s ganglion ; they are infraorbital (p. 105), superior palatine, naso-palatine, vidian, and pterygo-palatine (Section 14). The superior or posterior dental branch takes origin near the top of the upper maxilla, and descends with a tortuous course on the outer surface of that bone, along with a small branch of the superior maxillary nerve. It sends twigs into the foramina in the bone, and supplies the upper molar and bicuspid teeth ; but some external offsets are furnished to the gums. A few branches reach the lining membrane of the antrum. The INTERNAL MAXILLARY VEIN receive the offsets accompanying the branches of the artery in the first two parts of its course : these veins form a plexus — pterygoid^ between the two pterygoid muscles, and in part be- tween the temporal and external pterygoid muscles. This anastomosis communicates with the alveolar plexus ; with the facial vein by a large branch (anterior internal maxillary) : and with the cavernous sinus in the interior of the skull, by veinules that pass through the base of the cranium. Escaping from the plexus, the vein accompanies the artery to the paro- tid gland, and there joins the superficial tem[)oral vein, — the union of the two giving rise to the external jugular. Sometimes this common vessel enters the internal jugular vein (p. 42). The INFERIOR MAXILLARY NERVE (fig. 21) is the largest of the three trunks arising from the Gasserian ganglion (p. 32). It leaves the skull by the foramen ovale in the sphenoid bone, and divides beneath the ex- ternal pterygoid muscle into two cliief pieces, viz., an anterior, small, moto- sensory })art ; and a large, posterior, chiefly sensory portion. INFERIOR MAXILLARY NERVE. 95 Directions. Should the internal maxillary artery obstruct the view of the nerve, it may be cut through. The SMALLER I’ART, formed mainly by its contribution from the trunk of the nerve, receives nearly all the fibrils of the motor root, and ends in branches for the muscles of the jaw, viz., temporal, masseter, and one ptery- goid ; and for the muscle of the cheek, the buccinator. Fig. 21. Deep view of the Pterygoid Region (Illustra- tions of Dissections), Muscles : — а. Temporal reflected. h. Condyle of the jaw disarticulated with the external pterygoid attached to it. c. Internal pterygoid. d. Buccinator. /. Massi ter thrown down. Nerves ; — 1. Buccal. 2. Masseteric, cut. 3. Deep temporal. 4. Auriculo-temporal. б. Chorda tympani. 7. Inferior dental. 8. Gustatory. 10. Internal lateral ligament of the lower jaw. The arteries are not figured, with the exception of the internal maxillary trunk which is marked with 9 : the offsets of the artery ac- company the nerves, being named like them. The deep temporal branches (®) are furnished to the under surface of the temporal muscle. Like the arteries, they are two in number, anterior and posterior, and course upwards beneath the external pterygoid muscle. The posterior branch is the smallest, and is often derived from the masseteric nerve ; it is placed near the back of the temporal fossa. The anterior branch supplies the greater part of the muscle, and com- municates sometimes with the buccal nerve. The masseteric branch (^) takes a backward course above the external pterygoid muscle, and through the sigmoid notch, to the under surface of tlie masseter muscle : in the masseter the nerve can be followed to near the anterior border. As this branch passes by the articulation of the jaw it gives one or more twigs to that joint. The pterygoid branches come from both parts of the inferior maxillary nerve. The branch or branches to the external pterygoid spring from the small part, or from the buccal nerve, and enter the under surface of its muscle. The nerve to the internal pterygoid arises from the large part of the maxillary trunk close to the skull, and may be followed beneath the upper border to the deep surface of the muscle; it will be learnt in the dissection of the otic ganglion (Section 14). The buccal branch (^), longer and larger than the others, perforates the external pterygoid, and is directed inwards, beneath the coronoid process to the surface of the buccinator, where it ends in terminal brandies. As it perforates the pterygoid muscle filaments are given to the fleshy sub- 96 DISSECTION OF THE PTERYGOID REGION. stance ; and after it has passed through the fibres it furnishes a branch to the tem[)oral muscle. The nerve is directed towards the angle of the mouth, supplying the integument, the buccinator muscle, and the lining mucous membrane. It is united freely with the facial nerve, the two forming a plexus. The LARGER PART of the inferior maxillary nerve divides into three trunks — auriculo-temporal, dental, and gustatory. A few of the hbrils of the small (motor) root are applied to it, and are conveyed to certain mus- cles, viz., tensor tympani, circumflexus palati, pterygoideus, internus, my- lohyoideus, and digastricus. The AURICULO-TEMPORAL NERVE (*) Separates from the others near the base of the skull, and has commonly two roots. Its course to the sur- face of the head is directed first backwards beneath the external pterygoid muscle, as far as the inner part of the articulation of the jaw; and, then, upwards with the temporal artery in front of the ear. The nerve furnishes branches to the surrounding parts, viz., the joint, the ear, and the parotid gland ; and it communicates with the facial nerve. Its ramifications on the head are described at page 23. In the part now dissected its branches are the following: — a. Branches of the meatus audltorius. Two offsets are given to the * meatus from the point of union of the branches of the facial with the auriculo-temporal nerve, and enter that tube between the cartilage and bone. h. Articular branch. The branch to the joint of the jaw arises near the same spot as the preceding, or from the branches to tlie meatus. c. The inferior auricular branch supplies the external ear below the meatus auditorius: it sends offsets along the internal maxillary artery, which communicates with the sympathetic nerve. d. Parotid branches. These small filaments ramify in the gland. e. Communicating branches. Two or more brandies around the ex- ternal carotid artery communicate with the facial and sympathetic nerves. The INFERIOR DENTAL is the largest of the three trunks into which the inferior maxillary nerve divides. In its course to the canal in the lower jaw, the nerve is external to the gustatory, and lies at first beneath the external pterygoid muscle ; it is afterwards placed on the internal pterygoid, and on the internal lateral ligament near the dental foramen. After the nerve enters the bone, it is continued forwards beneath the teeth to the foramen in the side of the jaw, and ends at that spot by dividing into an incisor and a labial branch. Only one muscular offset (mylo-hyoid) is supplied by the dental nerve before it enters the bone. Its branches are : — a. The mylo-hyoid branch arises from the trunk of the nerve near the dental foramen, and is continued along a groove on the inner aspect of the ramus of tlie jaw to the cutaneous surface of the mylo-hyoideus, and to the anterior belly of the digastric muscle. b. The dental branches arise in the bone, and supply the molar and bicus[)id teeth. If the bone is soft, the canal containing the nerve and artery may be laid open so as to expose these branches. c. The incisor branch continues the trunk of the nerve onwards to the middle line, and furnishes offsets to the canine and incisor teeth, beneath which it lies. . d. The labial branch (mental?) (fig. 9, ^^) issues on the face beneath DISSECTION OF THE SUBMAXILLARY REGION. 97 the depressor of tlie anj^le of the mouth. It gives branches to the muscles below the aperture of the mouth, and communicates with the facial nerve; but the greater part of tlie branch is directed upwards beneath the depressor labii inferioris, and is distributed on the inner and outer surfaces of the lower lip. The inferior dental artery^ after entering the lower jaw, has a similar course and distribution to the nerve. Thus it supplies offsets to the bone, dental branches to the molar and bicuspid teeth, and ends anteriorly in an incisor and a labial branch. The incisor branch is continued to the symphysis of the jaw, where it ends in the bone: it lies beneath the canine and incisor teeth, to wliich it furnishes twigs. The labial branchy issuing by the labial foramen, ramifies in the struc- tures covering the lower jaw, and communicates with the branches of the facial artery. The GUSTATORY or LINGUAL NERVE (®) is the remaining trunk of the inferior maxillary, and is concealed at first, like the others, by the exter- nal pterygoid muscle. It is then inclined inwards with a small artery over the internal pterygoid muscle, and under cover of the side of the jaw to the tongue. The remainder of the nerve will be seen in the dissection of the submaxillary region. In this course under the jaw the nerve does not distribute any branch to the parts around, but the following communicating branch is received by it. The chorda tympani is a branch of the facial nerve, and is distributed to the tongue. Escaping from the tympanum by the Glaserian fissure, this small branch (®) is applied to the gustatory nerve at an acute angle. At the point of junction some fibrils communicate with the gustatory, but the greater part of the chorda tympani is conducted along that nerve to the tongue. The origin of the nerve, and its course across the tympanum to its posi- tion beneath the external pterygoid, are described in Section 14. Section VII. SUBMAXILLARY REGION. The submaxillary region is situate between the lower jaw and the hyoid bone. In it are contained the muscles of the os hyoides and tongue, the vessels and nerves of the tongue, and the sublingual and submaxillary glands. Position. In this dissection the position of the neck is the same as for the examination of the anterior triangle. Dissection. If any fatty tissue has been left on the submaxillary gland, or on the mylo-hyoid muscle, when the anterior triangular space was dis- sected,. let it be taken away. Tiie submaxillary gland (fig. 16, “) lies below the jaw in the anterior part of the space limited by that bone and the digastric muscle. Its shape is irregular, and the facial artery winds over the surface. It rests on the mylo-hyoideus, and sends a deep process round tlie posterior or free border 7 98 DISSECTION OF THE SUBMAXILLARY REGION. of that muscle. In front of it is the anterior belly of the digastric ; and behind is the stylo-maxillary ligament separating it from the parotid. Occupying a position somewhat below the side of the jaw, the gland is very near the surface, being covered only by the integuments and pla- tysma, and the deep fascia. In structure the submaxillary resembles the parotid gland (p. 42) ; and its duct — duct of Wharton — issuing from the deep process, extends beneath the mylo-hyoid muscle to the mouth. Dissection. To see the mylo-hyoid muscle, detach the anterior belly of the digastric from the jaw, and dislodge without injury the submaxillary gland from beneath the bone. The MYLO-HYOID MUSCLE (hg. 33, is triangular in shape, with the base at the jaw and the apex at the hyoid bone, and unites along the middle line with its fellow of the opposite side. It arises from the mylo- hyoid ridge on the inner surface of the lower jaw as far back as the last molar tooth; and is inserted into the middle of the body of the os hyoides, as well as into a central tendinous band between that bone and the jaw. On the cutaneous surface lie the digastric muscle, and the submaxillary gland, the facial artery with the submental offset, and its own branch of nerve and artery. Its fibres are frequently deficient near the jaw, and allow the next muscle to be seen. Only the posterior border is unattached, and round it a piece of the submaxillary gland winds. The parts in con- tact with the deep surface of the muscle will be perceived after the under- mentioned dissection has been made. Action. The lower jaw being fixed the muscle approaches the os hyoides to the jaw, enlarging the pharynx preparatory to swallowing. With the hyoid bone immovable, the mylo-hyoideus can help in de- pressing the jaw, and opening the mouth. Dissectio7i. To bring into view the muscles beneath the mylo-hyoid, and to trace the vessels and nerves to the substance of the tongue (as in figure 23), the student should first divide the facial vessels on the jaw, and remove them with the superficial part of the submaxillary gland; but he should be careful to leave the deep part of the gland which turns be- neath the mylo-hyoideus, because the small submaxillary ganglion is in contact with it. Next he should cut through the small branches of ves- sels and nerve on the surface of the mylo-hyoideus ; and detaching that muscle from the jaw and its fellow, should throw it down to the os hyoides, but without injuring the genio-hyoid muscle beneath it. Afterwards the bone is to be sawn through on the right side of the muscles attached to the symphysis, the soft parts covering the lower jaw having been previously cut. The side of the jaw, which will then be loose (for the ramus of the bone has been sawn before), is to be raised to see the parts beneath, and it may be fastened up out of the M'ay with a stitch; but it should not be detached from the mucous membrane of the mouth. The apex of the tongue is to be now pulled well out of the mouth over the upper teeth, and fastened with a stitch to the septum of the nose, whilst the left half of the jaw is to be drawn down forcibly with hooks. The scalpel should be tlien })assed from below upwards between the sawn surfaces of the bone, for the purpose of dividing a strong band of the mucous membrane of the mouth; and it should be carried onwards along the middle line of the tongue to the tip. By means of a stitch the os hyoides may be fastened down, to make HYOID AND STYLOID MUSCLES. 99 tight the muscular fil)res. All the fat and areolar tissue are to be removed, and in doing this the student is to take care of tlie Whartonian duct ; ol tlie hypoglossal nerve and its branches, wliich lie on the liyo-glossus mus- cle, and especially of its small offset ascending to the stylo-glossus mus- cle ; also of the gustatory nerve nearer the jaw. Between the gustatory nerve and the deep part of the sulmiaxillary gland the dissector should seek the small submaxillary ganglion (smaller than a pin’s head), with its offsets; and should endeavor to separate from the trunk of the gustatory the small chorda tympani nerve, and to define the offset from it to the submaxillary ganglion. At the hinder border of the hyo glossus clean the lingual vessels, the Stylo-hyoid ligament, and the glosso-pharyngeal nerve, all passing beneath that muscle; and at the anterior border find the issuing ranine vessels which, with the gustatory and hypoglossal nerves, are to be traced on the under surface of the tongue to the tip. Parts beneath mylo-hyoideus (fig. 23). The relative position of the objects brought into view by the steps of the previous dissection is now apparent: — Extending from the cornu of the hyoid bone to the side of the tongue is the hyo-glossus muscle, whose fibres are crossed superiorly by those of the stylo-glossus. On the hyo-glossus are placed, from below upwards, the hypoglossal nerve, the Whartonian duct, and the gustatory nerve, the latter crossing the duct; and near the inner border of the mus- cle the two nerves are united by branches. Beneath the same muscle lie, from below upwards, the lingual artery with its vein, the stylo-hyoid ligament, and the glosso-pharyngeal nerve. Above the hyo-glossus is the mucous membrane of the mouth, with the sublingual gland attached to it in front, and some fibres of the superior constrictor muscle covering it behind near the jaw. Between the chin and the os hyoides, along the middle line, is situate the genio-hyoid muscle ; and larger and deeper than it is a fan-shaped muscle, the genio-hyo-glossus. Along the outer side of the last muscle lie the ranine vessels ; and a sublingual branch for the gland of the same name springs from the lingual artery at the inner border of the hyo-glos- sus. On the under surface of the tongue, near the margin, lies the gus- tatory nerve ; and in the fibres of the genio-hyo-glossus runs the hypo- glossal nerve. The iiYO-GLOSSUS MUSCLE (fig. 22, 0 tliin and somewhat square in shape. The muscle arises from the lateral part of the body of the os hyoides (basio-glossus), and from all the great cornu of the same bone (cerato-glossus). The two pieces form a thin sheet, and enter the back part and side of the tongue ; they will be seen afterwards to mingle with fibres of the palate- and stylo-glossus.^ The parts in contact with the surfaces of the hyo-glossus have been already enumerated ; and beneath the muscle also are portions of the genio-hyo-glossus and middle constrictor. Along the anterior border is the genio-hyo-glossus muscle. Action. When the tongue is at rest, the muscle can bring that organ to the floor of the mouth, drawing down the sides and giving a rounded * A third part (clioiidro-glossus) is distinct from the others, and is not dissected ; it ends on the upper surface of the tongue near the root. For further details re- specting tlie anatomy of this and the other lingual muscles, reference is to be made to the dissection of the tongue. Section 15. 100 DISSECTION OF THE SUBMAXILLARY REGION. Fiff. 22. form to the dorsum ; but if the tongue is protruded from the mouth, the fibres will retract it into that cavity. If the tongue is fixed against the roof of the mouth by other mus- cles, even though the lower jaw is depressed, this muscle with the genio- hyo-glossus will elevate the os hyoides, and allow swallowing to take place. The STYLO-GLOSSUS (fig. 22, is a slender muscle, whose attachments are exi)ressed by its name. Arising from the styloid process near the apex, and from the stylo-maxillary ligament, the muscle is continued for- wards to the side of the tongue. Here it gives fibres to the dorsum, and turning to the under surface, extends to the tip of the tongue. Beneath the jaw this muscle is crossed by the gustatory nerve. Action. Both muscles will raise the back of the tongue against the roof of the mouth, but if the tongue is protruded they will restore it to the cavity. One muscle can direct the point of the tongue towards its own side of the mouth. The GENio-HYOiD MUSCLE (fig. 22, ariscs from the lower of the two lateral tubercles on the inner aspect of the symphysis of the jaw, and is in- serted into the middle of the hyoid bone. Covered by the mylo-hyoideus, this muscle rests on the genio-hyo-glossus. The inner border touches the muscle of the opposite side, and the two are often united. Action. As long as the mouth is shut it raises the hyoid bone ; but acting from the os hyoides, and the closers of the mouth being relaxed, it can depress the jaw and open the mouth. The GENIO-HYO-GLOSSUS (fig. 22,^) is the largest muscle of this region ; it has a triangular form, with the apex at the jaw, and the base at the middle line of the tongue. It takes origin from the upper tubercle behind the symphysis of the jaw. From this spot the fibres radiate, the posterior passing downwards to their insertion into the body of the hyoid bone, the anterior and the intermediate to the tongue from Muscles of the Tongue. 1. Hyo-glossus. 4. Genio-hyoideus. 2. Stylo-glossus. 5. Stylo-pharyugeus. 3. Geiiio-hyo-glossus. forwards to the tip of the tongue root to point. Lying along the middle of the tongue, it is in contact with its fellow. The lower border of the muscle corresponds with the genio-hyoideus, and the upper with the frcenum lingum. On its outer side are the ranine ves- sels, and the hyo-glossus muscle ; and the hyi)Oglossal nerve })erforates the posterior fibres. Action. By the simultaneous action of all the fibres the tongue is depressed in the fioor of the mouth, and hollowed along the middle. But different parts of the muscle are thought to have difierent uses when they GUSTATOKY NERVE. 101 act from the jaw : — Thus the fibres attached to the os hyoides advance and fix that bone before swallowing ; the hinder tongue fibres raise the root of the tongue and protrude the tip, and the anterior then turn down the tip of the tongue over the teeth. When the mouth is open swallowing can be performexi if the tongue is fixed against the teeth and roof of the mouth, because this muscle and the hyo-glossus can then raise the hyoid bone. The lingual artery (fig. 17, /‘), arises from the external carotid between the superior thyroid and facial branches. At first it is directed inwards above the os hyoides, and then upwards beneath the hyo-glossus to the under part of the tongue (fig. 23) ; it ends at the anterior border of that muscle in the sublingual and ranine branches. Near the hyo-glossus the artery is crossed by tlie ninth nerve, and by the digastric and stylo-hyoid muscles. Beneath the hyo-glossus, the vessel rests on the middle con- strictor and genio-hyo-glossus muscles, and is below the level of the glosso- pharyngeal nerve. Its branches are these : — a. A small hyoid branch is distributed on the upper border of the os hyoides, supplying the muscles ; it anastomoses with its fellow of the oppo- site side, and with tlie hyoid branch of the superior thyroid artery of the same side. b. A branch to the dorsum of the tongue arises beneath the hyo-glossus muscle, and ascends to supply the substance of the tongue and the tonsil. The fibres of the hyo-glossus must be divided to see it. c. The sublingual branch springs from the final division of the artery at the edge of tlie hyo-glossus, and is directed outwards to the gland of the same name. Some offsets supply the gums and the contiguous muscles, and one continues behind the incisor teeth to join a similar artery from tlie other side. d. The ranine branch (9) is the terminal part of the lingual artery, and extends forwards along the outer side of the genio-hyo-glossus to the tip of the tongue where it ends. Muscular offsets are furnished to the sub- stance of the tongue of the same side. This artery lies along the frsenum linguae, but is imbedded in the muscular fibres. The lingual vein commences on both the upper and under surfaces of the tongue. It lies with its companion artery, and ends in the internal jugular vein. The GUSTATORY or LINGUAL NERVE (fig. 23, has been followed in the pterygo-maxillary region to its passage between the ramus of the lower jaw and the internal pterygoid muscle (p. 97). In this dissection the nerve is inclined forwards to the side of the tongue, across the mucous membrane of the mouth and the origin of the superior constrictor muscle, and above the deep part of the submaxillary gland. Lastly, it is directed across the Whartonian duct, and along the side of the tongue to the apex. Branches are furnished to the surrounding parts, thus : — Two or more offsets connect it with the submaxillary ganglion, near the gland of that name. Farther forwards branches descend on the hyo-glossus to unite in a kind of plexus wdth twigs of the hypoglossal nerve. Other filaments are supplied to the mucous membrane of the mouth, the gums, and the sublingual gland. Lastly, the branches for the tongue ascend through the muscular sub- stance, and are distributed to the conical and fungiform papillae. The submaxillary ganglion (fig. 23, '^) resembles the other ganglia 102 DISSECTION OF THE SUBMAXILLARY REGION. connected with the three trunks of the fifth nerve, and communicates with sensory, motory, and sympathetic nerves. It is smaller in size than the lenticular ganglion, is sometimes rather red, and is placed above the deep process of the submaxillary gland. Offsets proceed upwards to connect it ^dth other nerves ; and from the lower part arise the branches to the ad- jacent structures. Connection with nerves — roots. Two or three branches, in the form of loops, pass from the ganglion to the gustatory nerve. At the posterior Fig. 23. Muscles : A. Genio-hyo-glossus. B. Genio-hyoideus. c. Hyo-glossiis. I). Stylo-glosRus. E Mylo-liyoideus, reflected. H. Stylo-hyoideas. j. Posterior belly of digastricus. Nerves: 1. Gustatory. 2. Submaxillary ganglion. 3. Wharton’s duct. 4. Glosso-pharyngeal nerve. 6. Hypo-glossal. 7. Upper laryngeal. The lingual ar- tery ramifies in this region, lying by the side of the hypoglossal nerve : the ranine offset is marked with 9. Deep view of the Submaxillary Region (Illustrations of Dissections). part the ganglion is further joined by an offset from the chorda tympani (of the facial nerve) which lies in contact with the gustatory. And its sympathetic branch comes from the nerves around the facial artery. Branches. From the lower part of the ganglion five or six branches descend to the substance of tlie submaxillary gland ; and from the anterior part other filaments are furnished to the mucous membrane of the mouth and the Whartonian duct. Chorda tympani. Joining the gustatory above by fibrils (p. 97), it is applied to tlie back of that nerve till near the tongue, and can be easily sejfarated from it ; but beyond that point it enters amongst the fibres of the gustatory nerve and is conveyed to the tongue. Near the submaxil- lary gland an offset is sent to the submaxillary ganglion. The iiYPO-GLOSSAL 01 ’ NINTH NERVE (fig. 23, ®) ill the submaxillary region lies on the hyo-glossus muscle, being concealed by the mylo- hyoideus : but fit the inner border of the hyo-glossus it enters the fibres of the genio-hyo-glossus, and is continued along the middle line of the tongue to the tip. Branches. On the hyo-glossus the ninth nerve furnishes branches to the muscles of the submaxillary region, except the mylo-hyoid and the digastric, viz., to the hyo-glossus, stylo-glossus, genio-hyoideus, and genio- hyo-glossus. F urther, some offsets communicate with the gustatory nerve on tlie hyo-glossus. Along the middle of the tongue the nerve sends upwards long filaments UPPER MAXILLARY NERVE. 103 wliich supply the muscular structure, and communicate with the gustatory nerve. The ^losso-pharyngeal cranial nerve (fig. 23, *), issuing between the two carotid arteries, courses over tlie stylo-pharyngeus and the middle constrictor of the pharynx, and ends under the hyo-glossus in branches for the tongue. See Dissection of the Tongue. The duct of the suhmaxillary gland (fig. 23, ^), Wharton’s duct, issues from the deep part of the glandular mass turning round the border of the mylo-hyoid muscle. It is about two inches in length, and is directed up- wards on the hyo-glossus muscle, and beneath the gustatory nerve, to open on the side of the frienum linguin in the centre of an eminence : its opening in the mouth will be seen if a bristle be passed along it. The duct has a thin wall, and consists externally of a fibrous layer with much elastic tissue and a few pale muscular fibres, and internally of a mucous lining with flattened epithelium. The deep part of the submaxillary gland extends along the side of the duct, reaching in some instances the sublingual gland. The suhlingnal gland (fig. 23, is somewhat of the shape of an almond, and the longest measurement, which is about one inch and a half, is directed backwards. It is situate beneath the anterior part of the tongue, in con- tact with the inner surface of the lower jaw, and close to the symphysis. Separated from the cavity of the mouth by the mucous membrane, the gland is prolonged across the upper border of the genio-hyo-glossus muscle, so as to touch the one of the opposite side. The sublingual is an aggregation of small glandular masses, each being provided with a separate duct (Henle). The ducts (ductus Riviniani) are from ten to eighteen in number. Some of them open beneath the tongue along a crescent-shaped fold of the mucous membrane, and others join the Whartonian duct ; one or more form a larger tube, which either joins that duct or opens near it. Section A^III. SUPERIOR MAXILLARY NERVE AND VESSELS. Directions. The student may examine next the right orbit, and the remaining trunk, superior maxillary of the fifth nerve. Supposing the right orbit to be untouched, the student may vary his former examination of the left cavity (p. 50) by dissecting it from the outer side. Dissection. For this purpose divide the margin of the orbit with a saw through the supra-orbital notch, and the roof with a chisel back to the sphenoidal fissure. Cut also with a chisel (from the inside) along the middle fossa of the base of the skull from the S|)henoidal fissure in front to the foramen spinosum behind, and outside the line of the foramen ro- tundum and foramen ovale. The side of the skull is next to be sawn ver- tically in front of the petrous part of the temporal bone, so that the incision shall end at the posterior extremity of the cut made in the base. After- wards the outer wall of the orbit is to be sawn horizontally into the sj)heno- maxillary fissure. The piece of bone forming part of the cranium and 104 DISSECTION OF THE NECK. orbit is now loose, and is to be removed with the temporal muscle. If the ])art of the roof of the orbit, which is left, should interfere with the sight of tlie contents of the cavity, let it be taken away with a bone-forceps. Tiie description of the orbit (p. 51) will serve in a general way for the right cavity. The superior maxillary division of the fifth nerve, in its course to the face, occupies successively the skull, the spheno-maxillary fossa, and the infra-orbital canal. The beginning of the nerve in the cranium has been already demon- strated (p. 31). Dissection. In the spheno-maxillary fossa the nerve can be partly seen by the dissection already made for the orbit, and its exposure here will be completed by removing the tat, and cutting away some of the wing of the sphenoid bone, so as to leave only an osseous ring round the nerve at its exit from the skull. In tlie fossa the student seeks the following offsets, tlie orbital branch entering the cavity of the orbit ; branches to Meckel’s ganglion which descend in the fossa ; and a dental branch along the back of the upper jaw. To follow onwards the nerve in the floor of the orbit, the contents of the cavity having been taken away, the bony canal in which it lies must be opened to tlie face. Near the front of the orbit the anterior dental branch is to be traced downwards for some distance in the bone. The infraorbital vessels are prepared with the nerve. The Sltpp:rior maxillary nervf: (fig. 24) commences in the Gasse- rian ganglion (p. 31), and leaves the cranium by the foramen rotundum. The course of the nerve is almost straight to the face, across the spheno- maxillary fossa, and along the orbital plate of the superior maxilla and the infraorbital canal. Issuing from the canal by the infraorbital foramen, it is concealed by the elevator of the upper lip, and ends in branches to the eyelid, nose, and upper lip : — a. The orbital branch (^) arises in the spheno-maxillary fossa, and en- tering the orbit, divides into malar and temporal branches (p. GO). b. The spheno -palatine branches (^) descend from the nerve in the fossa, and supply the nose and the palate; they are connected with Meck- el’s ganglion, and will be dissected with it (Section 14). c. A posterior dental branch (^) leaves the nerve near the upper jaw. It enters a canal in the maxilla, and supplies branches to the molar teeth and the lining membrane of the antrum ; it joins the anterior dental branch near the teeth. Before entering the canal it furnishes one or more offsets to the gums and the buccinator muscle. d. The anterior dental branch (®) quits the nerve trunk in the floor of tlie orbit, and descends to the anterior teeth in a special canal in front of the antrum: it is distributed by two branches. One (inner) gives nerves to the incisor and canine teeth, and furnishes one or two filaments to the lower meatus of the nose; the other (outer) ends by supplying the bicuspid teeth. €. Before the trunk ends in the facial branches, it supplies a small pal- pebral off'set to the lower eyelid; this is directed upwards to the lid in a groove in the margin of the orbit. /’. Infraorbital or facial branches C^). These are larger than the other offsets of the nerve, and form its terminal ramifications. Some incline inwards to the side of the nose, and the rest descend to the upper lip. Near the orbit they are crossed by branches of the facial nerve (fig. 9, “), UPPER MAXILLARY NERVE. 105 with which they communicate, the whole forming the infraorbital plexus 49 ). g. The branches for the side of the nose supply the muscular and tegu- mentary structures. Fig. 24. 2. Trunk of the nerve leaving the Gasserian ganglion. 3. Spheno-palatine branches. 4. Teinporo-nialar branch. 5. Posterior dental nerves. 6. Anterior dental. 7. Pacial branches. Di.4lGram of the Upper Maxillary Nerve and its Branches. h. The branches for the upper lip are three or four in number, which divide as they descend, and are distributed chiefly to the surfaces of the lip, though they supply as well the muscles and the labial glands. The infraorbital artery is a branch of the internal maxillary (p. 94). Taking the course of the nerve through the infraorbital canal, the vessel appears in the face beneath the elevator muscle of the upper lip; and it ends in branches, which are distributed, like those of the nerve, to the parts between the eye and mouth. In the face its branches anastomose with the facial and buccal arteries. In the canal in the maxilla the artery furnishes branches to the orbit. Another branch, anterior dental, runs with the nerve of the same name, and supplies the incisor and canine teeth : this gives offsets to the antrum of the maxilla, and near the teeth it anastomoses with the posterior dental artery. The i^ein, accompanying the artery, communicates in front with the facial vein; and terminates behind in a plexus of veins (alveolar) corre- sponding with the offsets of the internal maxilla artery in the spheno- maxillary fossa. Section IX. DEEP VESSELS AND NERVES OF THE NECK. In this Section are included the deepest styloid muscle, the internal carotid and ascending pharyngeal arteries, and some cranial and sympa- thetic nerves. Position. The position of the part is to remain as before, viz., the neck is to be fixed over a small block. 106 DISSECTION OF THE NECK. Dissection. To see the stylo-pharyngeus muscle, the posterior belly of the digastric, and the stylo-hyoid muscle, should be detached from their origin and thrown down. The trunk of the external carotid artery is to be removed by cutting it tlirough where the hypoglossal nerve crosses it, and by dividing those branches of it that have been already examined; the veins accompanying the arteries are to be taken away. In cleaning the surface of the stylo-pharyngeus muscle, the glosso- pharyngeal nerve and its branches, and the stylo-hyoid ligament may be prepared. The side of the jaw is to be drawn forwards on the face. The STYLO-PHARYNGEUS MUSCLE (levator pharyngis externus) resem- bles the other styloid muscles in its elongated form. The fibres arise from the root of the styloid process on the inner surface, and descend be- tween the superior and middle constrictors to be inserted partly into the pharynx, and partly into the upper border (hinder border, Merkeb) of the thyroid cartilage. The muscle lies below the stylo-glossus, and between the carotid arte- ries ; and the glosso-pharyngeal nerve turns over the lower part of its fleshy belly. Action. It elevates and draws outwards the part of the pharynx above the hyoid bone, making the tube ready for the reception of the morsel to be swallowed. From its attachment to the thyroid cartilage it will raise the larynx; and by its position it will control the movement forwards of the air tube. The stylo-hyoid ligament is a fibrous band, which extends from the tip of tlie styloid process to the small cornu of the os hyoides. Its position is between the stylo-glossus and stylo-pharyngeus muscles, and over the in- ternal carotid artery ; whilst the lower end is placed beneath the hyo- glossus muscle. To the posterior border the middle constrictor muscle is attached below. It is frequently cartilaginous or osseous in part of, or in all its extent. Occasionally a slip of fleshy libres is continued along it. The INTERNAL CAROTID ARTERY Supplies parts within the head, viz., the brain, the eye and orbit, and the nose ; and takes a circuitous course through and along the base of the skull before it terminates in the brain. The arterial trunk in the cranium, and its offset to the orbit, have been already examined ; but the portion in the neck and the temporal bone re- mains to be dissected. The branches of the carotid to the brain are examined with the encephalon. Dissection. For the display of the cervical part of the artery (fig. 25) there is now but little dissection required. By detaching the styloid pro- cess at the root, and throwing it with its muscles to the middle line, the internal carotid artery and the jugular vein may be followed upwards to tlie skull. Only a dense fascia conceals them, but this is to be taken away carefully, so that the brandies of the nerves may not be injured. In the fascia, and directed inwards over the artery, seek the glosso- pliaryngeal nerve and its branches near the skull, and the small pharyn- geal branch of the vagus lower down ; still lower, the superior laryngeal brancli of the vagus, with its external laryngeal offset crossing beneath the carotid. Between the vein and artery, close to the skull, will be found the vagus, hyj)Oglossal, and sympathetic nerves ; and crossing backwards, over or under the vein, the S[)inal accessory nerve. External to the ves- • Auatomie und Pliisiologie des Meiiscliliclien Stimm iind Spracli Organs. Leip- zig, 1857. Von Dr. Merkel. STYLO-PHAEYNGEUS MUSCLE. 107 sels a loop of the first and second cervical nerves over the transverse process of the atlas is to be defined ; and from it branches of communica- tion are to be traced to the large ganglion of the sympathetic beneath the artery, and to the vagus and hypoglossal nerves. Ascending to the cranium, on the inner side of the carotid, the ascending pharyngeal artery will be met with. To open the carotid canal in the temporal bone, and to follow the con- tained artery into the cranium, make a cut along the side of the skull in the following manner : the saw being placed beneath the mastoid process, cut forwards to the foramen spinosum in the wing of the sphenoid bone (to which s[)Ot the side of tlie skull has been already taken away), and let the instrument be directed through the stylo-mastoid foramen and the root of the styloid process, but rather exteimal to the jugular foramen and the carotid canal. When the piece of bone has been detached, the carotid canal may be opened with the bone forceps. In cleaning the artery in the canal, large and rather red branches of the superior cervical ganglion of the sympathetic will be found on it ; and in a fresh part two small filaments may be recognized with care — one from Jacobson’s nerve, joining the sympathetic at the posterior part of the canal ; the other from the vidian nerve, at the front of the canol. On the piece of bone that has been cut otf, the dissector may jwejiare very readily the tympanum with its membrane and chain of bones, and the chorda tympani nerve. The internal carotid artery (fig. 25, c?) springs from the bifurcation of the common carotid trunk. It extends from the upper border of the thy- roid cartilage to the base of the skull ; then through the petrous portion of the temporal bone ; and lastly along the base of the sknll to the anterior clinoid process, where it ends in branches for the brain. This winding course of the artery may be divided into three parts : one in the neck, an- other in the temporal bone, and a third in the cranium. Cervical 'part. In the neck the artery ascends almost vertically from its origin to the carotid canal, and is in contact with the ])harynx on the inner side. The line of the common carotid artery would mark its posi- tion in the neck. Its depth from the surface varies like that of the ex- ternal carotid ; and the digastric muscle may be taken as the index of this difference. Thus, below that muscle, the internal carotid is overlapped by the sterno-mastoid and covered by the common teguments, fascia, and the platysma, and is on the same level as the external carotid, though farther back. But, above that muscle, the vessel is placed deeply beneath the external carotid artery and the parotid gland, and is crossed by the styloid ])rocess and the stylo-pharyngeus muscle. Whilst in the neck the internal carotid lies on the rectus capitis anticus major muscle, which separates it from the vertebrre. Vein. The internal jugular vein accompanies the artery, being con- tained in a sheath with it, and placed on the outer side. Small vessels. Below the digastric muscle the occipital artery is directed back over the carotid ; and the offset from it to the sterno-mastoi- deus may run down on the carotid trunk. Above the digastric the poste- rior auricular vessels cross the carotid. Nerves. The pneumogastric is contained in the sheath between the artery and vein, being ])arallel to them ; and the sympathetic, also run- ning longitudinally, lies behind the sheath of the vessels. Crossing the artery superficially, from below up, is the hypoglossal, which sends the 108 DISSECTION OF THE NECK (lescendens noni along it ; next the small pharyngeal branch of the vagns ; and lastly the glosso-pharyngeal. Directed inwards beneath the carotid is the superior laryngeal nerve, furnishing the external laryngeah branch ; together with pharyngeal offsets of the upper ganglion of the sympathetic. Fig. 25. Deep Vessels and Nerves of the Neck Arteries: a. Subclaviaa trunk. h. Conimou carotid. / c. External carotid, cut. d. Internal carotid. f. Inferior palatine branch of the facial. g. Ascending pharyngeal. Nerves: 1. Glosso-pharyngeal. 2. Spinal accessory. 3. Pueumo-gastric or vagus. (Illustrations of Dissections). 4. Hypoglossal. Phai-yngeal branch of the vagus. 6. Upper laryngeal branch of the vagus. 7. External laryngeal branch of the last. 8. Thyro-hyoid branch of the hypoglossal. 9. Desceudens noni of hypoglossal, cut. 10. Phrenic nerve of cervical plexus. 11. Brachial plexus. Recurrent of the vagus, winds round the subclavian artery, a. Close to the skull the erunial nerves of the neck are interposed between the artery and tlie vein. Around the carotid entwine branches of the sympathetic, and offsets of the glosso-pharyngeal nerve. The cervical part of the artery remains much the same in size to the ASCENDING PHARYNGEAL VESSELS. 109 end, though it is sometimes very tortuous; and it usually does not furnish any braneh. Part in the temporal hone. In the carotid canal the winding course of the vessel commences. The artery first ascends in front of the inner ear (cochlea and tympanum) ; next it is directed forwards almost horizontally; and lastly it turns upwards into the cranium opposite the foramen lacerum (basis cranii). Branches of the sympathetic nerve surround the carotid in tlie bone. Whilst in the canal the artery supplies a small branch to the cavity of the typanum. Tlie cranial part of the artery is described with the base of the skull (p. SS). The INTERNAL JUGULAR VEIN is coutinuous with the lateral sinus of the skull, and extends from the foramen jugulare nearly to tlie first rib. At the lower part of the neck it joins the subclavian to form the innomi- nate vein (p. 79). As far as the thyroid cartilage the vein accompanies the internal carotid, but below that point it is the companion to the common carotid artery; and it lies on the outer side of each. Its contiguity to the artery is not equally close throughout, for near the skull tliere is a small interval be- tween them, containing the cranial nerves; and at the lower part of the neck there is a still larger intervening space, in which the pneumogastric nerve with its cardiac branch is found. The size of the upper part of the vein remains much the same till near the os hyoides, where it is suddenly increased by the addition of those branches of the head and neck, corresponding with branches of the exter- nal carotid artery, which do not join tlie external jugular vein.^ Its lower dilatation and its valves have been referred to (p. 82). The following branches open into the internal jugular, viz., the facial, lingual, thyroid (superior), occipital, and pharyngeal; and at the lower part of the neck it receives the middle thyroid vein. The ascending pharyngeal artery (tig. 25, g) is a long slender branch of the external carotid, which arises near the commencement of that vessel. Directed upwards on the spinal column between the internal carotid and the pharynx, the artery becomes tortuous near the skull, and enters the pharynx above the upper constrictor to end in the soft palate. In the neck the artery gives some small offsets to the surrounding parts, viz., the muscles on the vertebrae, the nerves, and the lymphatic glands. A meningeal branch enters the cranium through the foramen lacerum (basis cranii), and is distributed in the dura mater of the middle fossa of the skull ; this is seldom seen in the cranium, because it is but rarely injected. The palatine branch, which is larger than the preceding, divides in the pharynx into two main pieces, which are directed across the fore part of the palate beneath the mucous membrane, and form arches with like branches of the opposite side ; one of these is near the upper, and the other near the lower edge of the soft palate.'^ The size of the pala- tine artery depends upon that of the inferior palatine branch of the facial artery. ' Sometimes the term internal cephalic is applied to the vein between the skull and the hyoid bone ; and the name internal jugular, to the part below that bone and the junction of its large branches. 2 The Anatomy of the Arteries. By R. Quain, F.R.S., p. 110. 110 DISSECTION OF THE NECK. Pharyngeal hranches. Other small arteries ramify in the upper con- strictor, the Eustachian tube, the back of the soft palate, and the tonsil. Tlie vein accompanying the pharyngeal artery receives branches from the cranium, tlie palate, and the pharynx, and ends in the internal jugular vein. Dissection of the cranial nerves in the neck. By the time this stage of the dissection has been arrived at, the condition of the parts will not per- mit the tracing of the very minute filaments of the cranial nerves in the foramen jugulare of the skull ; and all the paragraplis marked with an asterisk are tlierefore to be omitted for the present. Afterwards, if a fresh })iece of the skull can be obtained, in which the bone has been softened by acid, and the nerves hardened in spirit, the examination of the branches now passed over may be made. * In the foramen lacerum (fig. 26). Supposing the dissection of the internal carotid to be carried out as is described at page 107, let the stu- dent cut across with care the jugular vein near the skull. Let liim then remove bit by bit with the bone forceps, or with a scalpel if the part has been softened, tlie ring of bone which bounds externally the jugular fora- men, proceeding as far forwards as the osseous crest between that foramen and tlie carotid canal. Between the bone and the coat of the jugular vein, the small auricular branch of the pneumogastric nerve is to be found; it is directed backwards to an aperture near the styloid process. * Trace, then, the spinal accessory and jmeumogastric nerves through the aperture, by opening the fibrous sheath around them. Two parts, large and small, of the spinal accessory nerve should be defined ; the latter is to be shown joining a ganglion on the vagus, and applying itself to the trunk of that nerve. A communication between the two parts of the spinal accessory is to be found. On the pneumogastric is a small well- marked ganglion, from which the auricular branch before referred to takes origin ; and from the ganglion filaments are to be sought passing to the smaller portion of the spinal accessory nerve, and to the ascenaing branch of the upper cervical ganglion of the sympathetic. * Next follow the glosso-pharyngeal nerve through the fore part of the foramen, and take away any bone that overhangs it. This nerve presents two ganglia as it passes from the skull (fig. 26): one (jugular), which is scarcely to be perceived, near the upper part of the tube of membrane containing it; the other, much larger (petrous), is situate at the lower border of the petrous portion of the temporal bone. From the lower one, seek the small nerve of Jacobson, which enters an aperture in the crest of bone between the jugular foramen and the carotid canal ; and another filament of communication with the ganglion of the sympathetic. Some- times the dissector will be able to find a filament from the lower oranorlion to join the auricular branch of the pneumogastric ; and another to end in the upper ganglion of the pneumogastric nerve. Below the foramen of exit from the skull the cranial nerves have been greatly denuded by the dissection of the internal carotid (fig. 25) ; but the intercommunications of the vagus, hypoglossal, sympathetic, and first two spinal nerves near the skull, are to be traced out more completely. The larger part of the S})inal accessory has been sutficiently laid bare already; but its small piece is to be traced to the vagus, close to the skull, and onwards by the side of that trunk. The chief pjirt of the glosso-pharyngeal has been also dissected ; but the offsets on the carotid, and others to join the pharyngeal branch of the vagus and the pharyngeal plexus are to be displayed. GLOSSO-PHARYNGEAL NERVE. Ill On the pneumogastric trunk tlie student should define an enlargement close to the skull (ganglion of the trunk) to which the hypoglossal nerve is intimately united. From the ganglion proceed two branches (pharyn- geal and laryngeal), which are to be traced to the parts indicated by their names, especially the first which enters the pharyngeal plexus. The task of disentangling the ramifications of the branch of the vagus, and those of the glosso-pharyngeal and sympathetic in the plexus, is by no means easy, in consequence of the dense tissue in which they are contained. Two or more cardiac offsets of the vagus, one at the upper and another at the lower part of the neck, may be recognized readily. Lastly the dissector may prepare more fully the recurrent branch coursing up beneath the lower part of the common carotid : by removing the fat around it, offsets will be seen entering the chest and the windpipe. Only the first, or the deep part of the hypoglossal nerve remains to be made ready for learning ; its communications with the vagus, sympathetic, and the spinal nerves are to be demonstrated. A dissection for the sympathetic will be given further on (p. 110); but its large ganglion near the skull (upper cervical) should be defined, and the small branches from it to the pharyngeal plexus should be pursued beneath the carotid artery. The three cranial nerves^ glosso-pharyngeal, pneumogastric, and spinal accessory, which constitute the eighth nerve of Willis, leave the cranium by the foramen jugulare (p. 82). Outside the skull the nerves take dif- ferent directions according to their destination ; thus the glosso-pharyngeal is inclined inwards to the tongue and pharynx ; the spinal accessory back- wards to the sterno-mastoid and trapezius muscles ; and the pneumogastric nerve descends to the viscera of the thorax and abdomen. The GLOSSO-PHARYNGEAL NERVE (fig. 26, ’) is the smallest of the three trunks. In the jugular foramen it is placed somewhat in front of the other two, and lies in a groove in the lower border of the petrous part of the tem- poral bone. In the aperture of exit the nerve is marked by two ganglionic swellings, the upper one being the jugular, and the lower the petrous ganglion. * Ganglia. Tha jugular ganglion., (ganglion superius) is very small, and is situate at the upper part of the osseous groove containing the nerve. It is placed on the outer surface of the glosso-pharyngeal trunk, and in- cludes only some fibrils of the nerve. The petrosal ganglion., (gang, inferius) is much larger than the preceding, and incloses all the fibrils of the nerve. Ovalish in form, it is placed in a hollow in the lower border of the temporal bone ; and from it spiing the branches that unite the glosso- pharyngeal with other nerves. After the nerve has quitted the foramen it comes forwards between the jugular vein and the carotid artery (fig. 25, ^), and crossing inwards over tlie artery, reaches the lower border of the stylo-pharyngeus muscle. At this spot the nerve becomes almost transverse in direction in its course to the pharynx; it crosses over the stylo-pharyngeus, and forms an arch across the side of the neck above the superior laryngeal nerve. Finally it passes beneath the hyo-glossus muscle, and ends in branches to the pharynx, the tonsil, and the tongue. The branches of the glosso-pharyngeal may be classed into those con- necting it with other nerves at the base of the skull, and those distributed in the neck. * Connecting branches arise chiefly from the petrosal ganglion; and in this set is the tympanic nerve. 112 DISSECTION OF THE NECK. * A filament ascends from the sympathetic nerve in the neck to join tlie petrosal ganglion. Sometimes there is an offset from the ganglion to the auricular branch of the vagus, as well as to the upper ganglion of this nerve. * The tympanic branch (fig. 26, *) (nerve of Jacobson) enters the aperture in the ridge of bone between the jugular and the carotid foramen, and ascends by a special canal to the inner wall of the tympanum, where it ends in branches : its distribution is given with the tympanum of the ear. a. Bandies for Distrihulion. In the neck the branches are furnished chiefly to the pharynx and the tongue. b. Carotid branches surround the internal artery of that name, and communicate with the pharyngeal branch of the vagus, and the sympa- thetic nerve. c. Some muscular branches enter the stylo-pharyngeus, whilst the nerve is in contact with it. d. Branches to the pharynx ‘iovva the pharyngeal plexus by uniting with nerves from the sympathetic and vagus. e. The tonsillitic branches supply the tonsil and the arches of the soft palate. On die former they end in a kind of plexus — circulus tonsillaris. /'. Lingual branches. The terminal branches of the nerve supply the root and posterior part of the tongue, as well as the lateral surface. The distribution of these is described with the tongue (Section 15). Tlie PNEUMOGASTRic NERVE (fig. 26, ^) (vagus nerve) is the largest of the cranial nerves in the neck, and escapes through the jugular foramen Fig. 26. ' 1. GlossO'pharyngeal trunk. 2. Vagus. 3. Spinal accessory. 4. Jugular ganglion. 5. Petrosal ganglion. 6. Jacobson’s nerve. 7. Auricular branch. 8. Root ganglion of vagus. 9. Trunk ganglion of vagus. 10. Branch joining the petrosal and upper ganglion of the vagus. 11. Small part of spinal accessory. 12. Chief part of spinal accessoiy. 13. Pharyngeal branch of vagus. 14. Superior laryngeal branch of vagus. Biaquam of the Eighth Nerve, in the same sheath of dura mater as tlie spinal accessory. In the aperture of exit it has a distinct ganglion (gang, of the root), to which the smaller part of the spinal accessory nerve is connected. PXEUMOGASTRIC NERVE. 113 When the nerve has left the foramen, it receives the small part of the spinal accessory, and swells into a ganglion nearly an inch long (gang, of the trunk). Here the nerve lies between tlie internal carotid artery and jugular vein, and communicates witli several nerves. To reach the thorax, the vagus descends almost vertically (fig. 25, between the internal jugu- lar vein and the internal and common carotid arteries; and enters that cavity, on the right side, by crossing over the subclavian artery, but beneath the innominate vein. * Ganglia. The ganglion of the root (gang, superius), (fig. 2G, is of a grayish color, and in texture is like the ganglion on the large root of the fiftii nerve. Small branches in the foramen jugulare come from this gan- glion. The ganglion of the trunk (gang, inferius), (^) is cylindrical in form, is reddish in color, and is nearly an inch in length; it communicates with the hypoglossal, spinal, and sympathetic nerves. All the intrinsic fibres of the trunk of the nerve are surrounded by tlie ganglionic substance, but those derived from the spinal accessory nerve (‘^) pass over the gan- glion without being inclosed in it. The branches of the pneumogastric nerve may be arranged into those uniting it with other nerves, and tliose distributed to parts around. * Connecting branches (fig. 26) arise from the ganglion of the root and the ganglion of the trunk of the vagus. * From the ganglion of the root. The auricular branch (J) is the chief offset, and crosses tlie jugular fossa to enter an aperture near the root of the styloid process ; it traverses the substance of the temporal bone, and reaches the outer ear, on which it is distributed. Its farther course will be described with the anatomy of the ear. * One or two short filaments unite this ganglion with the spinal acces- sory nerve ; and a branch of the sympathetic nerve in the neck enters it. Occasionally there is an off'set to join the lower (petrosal) ganglion of the glosso-pharyngeal nerve. From the ganglion of the trimk. Communicating filaments connect it with the hypoglossal nerve. Other branches pass between it and the upper ganglion of the sympathetic, and between it and the loop of the first two cervical nerves. Branches for Distribution (fig. 25). The cervical branches arise from the inner side of the nerve, and are directed inwards, to su[)ply the pharynx, the larynx, and the heart. a. The pharyngeal brayich (fig. 26, ^^) is an offset from the upper part of the ganglion of the trunk, and terminates in the pharynx. The nerve is directed inwards over the internal carotid artery (fig. 25, ^), and joins the branches of the glosso-pharyngeal nerve on that vessel. Finally it courses to the side of the middle constrictor muscle, and communicates with branches of the glosso-pharyngeal, superior laryngeal, and sympa- thetic nerves, to form the pharyngeal plexus. From the plexus branches are furnished to the constrictors and palato-glossus and pharyngeus, and to the pharyngeal mucous membrane between the tongue and the hyoid bone. b. The superior laryngeal nerve (fig. 26, ^^) is much larger than the ])receding branch, and comes from the middle of the ganglion of the trunk. From this point it inclines obliquely inwards beneath the internal carotid artery (fig. 25, ®), and reaches the larynx opposite the interval between the hyoid bone and the thyroid cartilage. Tlie nerve then perforates the thyro-hyoid membrane, and is distributed to the mucous lining of the 8 114 DISSECTION OF THE NECK. larynx. (See “ Larynx.”) In the neck it furnishes branches to the thyroid body, and the following offset to one laryngeal muscle and the pharynx : — The external laryngeal branch (tig. 25, ’) arises beneath the internal carotid artery, and runs below the superior laryngeal nerve to the side of the larynx. Here it gives offsets to the pharyngeal plexus, and it is con- tinued beneath the sterno-thyroideus to the crico-thyroid muscle ard the inferior constrictor. Near its origin this branch communicates with the superficial cardiac branch of the sympathetic nerve. c. Cardiac branches. Some small cardiac nerves spring from the pneumo-gastric at the upper part of the neck, and join cardiac branches of the sympathetic. At the lower part of the neck, on each side, there is a single cardiac nerve : the right one enters the chest and joins the deep nerves to the heart from the sympathetic ; and the left nerve terminates in the superficial cardiac plexus of the thorax. d. The inferior laryngeal or recurrent nerve (fig. 25) leaves the pneumo- gastric trunk on the right side opposite the subclavian artery, and winding round that vessel, takes an upward course in the neck to the larynx, ascending beneath the common carotid and inferior thyroid arteries, and between the trachea and the cesophagus. At the larynx it enters beneath the ala of the thyroid cartilage, where it will be afterwards traced. The following branches arise from it : — Some cardiac branches leave the nerve as it turns round the subclavian artery ; these enter the thorax, and join the cardiac nerves of the sym- pathetic. Muscular branches spring from it whilst it lies between the trachea and the oesophagus, and are distributed to both those tubes. Near the larynx some filaments are furnished to the inferior constrictor muscle. On the left side the recurrent nerve arises in the thorax, opposite the arch of the aorta, but lies between the trachea and oesophagus in the neck, as on the right side. The SPINAL ACCESSORY NERVE (fig. 2G, ^^) coui'ses through the foramen jugulare with the pneumo-gastric, but is not marked by any ganglion. The nerve is constructed of two parts, viz., accessory to the vagus, and spinal, which have a different origin and distribution. (Origin of the cranial nerves.) The part accessory to the vagus (”) is the smaller of the two, and finally blends with the pneumo-gastric beyond the skull. In the foramen of exit it lies close to the vagus, and joins the upper ganglion of that nerve by one or two filaments. Below the foramen it is continued over the lower ganglion of the nerve, and blends with the trunk beyond the ganglion. It gives offsets to join the pharyngeal and upper laryngeal branches of the pneumo-gastric, and according to Bendz, to many other branches of that nerve. The spinal part (fig. 2G, ^^) is much larger, is round and cord-like, and is connected witli tlie smaller piece whilst it is passing through the fora- men jugulare. Beyond the foramen the nerve (fig. 25, ^) takes a back- ward course through the sterno-mastoid muscle, and across the side of the neck to end in the trapezius muscle : at first it is concealed by the jugular vein, but it then passes either over or under that vessel. The connections of the nerve beyond the sterno-mastoideus have been already examined (p. GO). SUB-OCCIPITAL NERVE. 115 The nerve furnishes muscular offsets to the sterno-mastoideus and the trapezius. The HYPOGLOSSAL NERVE (ninth of Willis), issuing from the cranium by the anterior condyloid foramen, lies deeply between the internal carotid artery and the jugular vein (tig. 25, *), It next comes forwards between the vein and artery, turning round the outer side of the vagus to which it is united. The nerve now descends in the neck, and becomes superficial below the digastric muscle in the anterior triangular space ; from this spot it is directed inwards to the tongue and its muscles. * Connecting branches. Near the skull the hypo-glossal is united by branches with the vagus nerve, the two being almost inseparably joined. * Kather lower down the nerve is connected by offsets with the sympa- thetic, and with the loop of the first two spinal nerves. The branches for distribution have been met with in the foregoing dis- sections. Thus in the neck it supplies, in union with the spinal nerves, the depressors of the hyoid bone. In the submaxillary region it furnishes branches to one elevator (genio-hyoid) of the os hyoides ; to the extrinsic muscles of the tongue except the palato and pharyngeo-glossus ; and to all the intrinsic of the tongue. Dissection. The small rectus capitis lateralis muscle, between the transverse process of the atlas and the base of the skull, is now to be cleaned and learnt. At its inner border the anterior branch of the first cervical nerve, which forms part of a loop on the atlas, is to be found. The RECTUS CAPITIS LATERALIS (fig. 25) is Small and thin, and repre- sents an intertransverse muscle. It arises from the anterior transverse process, and the tip of the united transverse processes of the atlas ; and is inserted into the jugular eminence of the occipital bone. On the anterior surface rests the jugular vein ; and in contact with the posterior is the vertebral artery. To the inner side lies the anterior pri- mary branch of the first cervical nerve. Action. It assists the muscles attached to the mastoid process in in- clining the head laterally. Dissection. For the purpose of tracing backwards the anterior branch of the first cervical nerve divide the rectus lateralis muscle, and observe the offset to it ; then cut ofi* the end of the lateral mass of the atlas, and remove the vertebral artery, so as to bring into view the nerve as it lies on the first vertebra. The anterior primary bra^ich of the first or sub-occipital nerve is slen- der in size, and arises from the common trunk on the neural arch of the atlas. From that origin it is directed forwards on the arch, beneath the vertebral artery, to the inner side of the rectus lateralis : here it bends down in front of the lateral mass of the bone, and forms a loop by uniting with the second cervical nerve. As the nerve passes forwards it supplies the rectus lateralis muscle, and branches connect the loop with the vagus, hypoglossal, and sympathetic nerves. Sympathetic Nerve. In the neck the sympathetic nerve consists, on each side, of a gangliated cord, which lies close to the vertebral column, and is continued into the thorax. On this part of the nerve are three ganglia : — One near the skull, another on the neck of the first rib, and a third somewhere between the two ; these are named respectively superior, inferior, and middle ganglion. From the ganglia proceed connecting branches with the spinal and most of the cervical cranial nerves; and branches for distribution to viscera and bloodvessels. 116 DISSECTION OF THE NECK. Besides the ganglia above mentioned, there are other ganglia in the head and neck in connection with tlie three trunks of the fifth nerve. Dissection. To display the branches of the sympathetic nerve requires greater care than is necessary in tracing the white fibred nerves, for they are softer, more easily torn, and generally of smaller size. In the neck the ganglia and their branches have been partly prepared, and only the following additional dissection will be required to bring tliem into view : — The jugular vein having been cut through, the upper ganglion will be seen by raising the carotid artery, and the trunks of the vagus and hypo- glossal nerves, and by cutting through the branches that unite these two to the loop of the first and second spinal nerves. Tlie several branches of the ganglion are to be traced upwards on the carotid artery, inwards to the pharynx, down along the neck, and outwards to other nerves. Tlie dissector has already seen the middle ganglion on or near the infe- rior thyroid artery, and its branches to spinal nerves, and along the neck, are now to be traced. To obtain a view of the inferior ganglion the greater part of the first rib is to be taken away, and the subclavian artery is to be cut through, inside the scalenus, and drawn aside, without however destroying the fine nerves that pass Over it. The clavicle is supposed not to be in position. The ganglion is placed on the neck of the first rib ; its branches are large, and are easily followed outwards to the vertebral artery and the spinal nerves, and downwards to the thorax. The SUPERIOR CERVICAL GANGLION is the largest of the three, and is of a reddish-gray color. Of a fusiform shape, it is as long as the second and third cervical vertebral, and is placed on the rectus capitis anticus major muscle, beneath the internal carotid artery and the contiguous cra- nial nerves. Branches connect the ganglion with other nerves ; and some are distributed to the bloodvessels, the ])harynx, and the heart. * Connecting branches unite the sympathetic with both the spinal and the cranial nerves. * With the spinal nerves. The four highest spinal nerves have branches of communication with the upper ganglion of the sympathetic ; but the offset to the fourth nerve may come from the cord connecting the upper to the next ganglion. * With the cranial nerves. Near the skull the trunks of the vagus (its lower ganglion) and hypoglossal nerves are joined by branches of the sympathetic. In the foramen jugulare also, both the petrosal ganglion of the glosso-pharyngeal and the ganglion of the root of the vagus receive small filaments, one to each, from an ascending offset of the ganglion. Communications are formed with several other cranial nerves by means of an offset from the ganglion into the carotid canal (p. 33). Branches for Distribution. This set of branches is more numerous than the preceding, and the nerves are larger in size. Branches for bloodvessels (nervi molles). These nerves surround the external carotid artery, and ramify on its branches so as to form plexuses on the arteries with the same names as the vessels : some small ganglia are occasionally found on these ramifying nerves. By means of the plexus on the facial artery the submaxillary ganglion communicates with the sym- [)athetic ; and through the plexus on the internal maxillary artery the otic ganglion obtains a similar communication. Another offset from the iq)per part of the ganglion accompanies the internal carotid artery and its branches. Near the skull it divides into CERVICAL GANGLIA OF SYMPATHETIC. 117 two pieces, wliicli enter the canal for the carotid, one on each side of that vessel : and are continued to the eyeball and tlie pia mater of the brain, forming secondary plexuses on the ophthalmic and cerebral arteries. In the carotid canal communications are formed with the tympanic nerve (p. Ill) and with the spheno-palatine ganglion (p. 141) ; with the former near the lower, and with the latter near the upper opening of the canal. The communications and plexuses which these nerves form in their course to the base of the brain are described at p. 33. The 'pharyngeal nerves pass inwards to the side of the pharynx, where they join with other branches of the cranial nerves in the pharyngeal plexus (p. 113). Cardiac nerves enter the thorax to join in the plexuses of the heart. There are tliree cardiac nerves on each side, viz., superior, middle, and inferior, each taking its name from the ganglion of which it is an offset. The superior cardiac nerve (superficial) of the riglit side courses behind the sheath of the carotid vessels, and enters the thorax beneath the sub- clavian artery. In the neck the nerve is connected with the cardiac branch of the vagus, with the external laryngeal, and with the recurrent nerve. In some bodies it ends by joining one of the other cardiac nerves. The MIDDLE CERVICAL GANGLION (gang, tliyroideiim) is of small size, and is situate opposite the fifth cervical vertebra, usually on or near the inferior thyroid artery. It has a roundish shape, and lies beneath the great vessels. Its branches are the following: — * Connecting branches with the spinal nerves sink between the borders of the longus colli and anterior scalenus, to join the fifth and sixth cervi- cal nerves. Branches for Distribution. These consist of nerves to the thyroid body, together with tlie middle cardiac nerve. The thyroid branches ramify around the inferior thyroid artery, and end in the thyroid body ; they join the external and recurrent laryngeal nerves. The middle or great cardiac nerve descends to the thorax across the subclavian artery ; its termination in the cardiac plexus will be learnt in the chest. In the neck it communicates with the upper cardiac and re- current laryngeal nerves. The INFERIOR CERVICAL GANGLION is of large size but irregular in shape, and occupies the interval between the first rib and the lateral mass of the last cervical vertebra, its position being internal to the superior intercostal artery. Oftentimes it extends in front of the neck of the rib, and joins the first swelling of the knotted cord in the thorax. Its branches are similar to those of the other two ganglia. One or two branches surround the trunk of the subclavian artery, and supply filaments to that bloodvessel. ^Connecting branches join the last two cervical nerves. Other nerves accompany the vertebral artery, forming a plexus — vertebral, around it, and communicate with the spinal nerves as high as the fourth. Only one branch for distribution, the inferior cardiac nerve, issues from the lower ganglion. It lies beneath the subclavian artery, joining in that position the recurrent laryngeal nerve, and enters the thorax to terminate in the deep cardiac plexus behind the arch of the aorta. Directions. The student now proceeds to dissect the left side of the neck, but the remains of the right half should be carefully preserved during the time occupied in tlie examination of the left half. 118 DISSECTION OF THE NECK. Section X. DISSECTION OF THE LEFT SIDE OF THE NECK. Directions. In the dissection of the left half of the neck, the differences observable between it and the right side are specially to be studied. When the description of the right side will suffice, reference will be made to it. After the neck has been made tense over a narrow block, the anterior part of it is to be prepared as on the opposite side. The description of the right side (p. 67 to 73) is to be used for the anterior triangular space, the sterno-mastoideus, and the depressor muscles of the hyoid bone. Next the scaleni muscles and the subclavian vessels are to be learnt. The dissection and description of the muscles on the right side (p. 73 to 75), will serve for those on the left, except that the student will meet on the left side with the thoracic duct. The thoracic duct is contiguous to the part of the subclavian artery in- side the scalenus muscle. If it is uninjected it looks like a vein, rather smaller than a crow-quill ; and it will be found by sepamting the jugular vein from the carotid artery, about half an inch above the clavicle, cours- ing from beneath the artery to end in the subclavian vein. On this side the clavicle may remain articulated, in order that the joint may be learnt. The LEFT SUBCLAVIAN ARTERY arises from the arch of the aorta, in- stead of from an innominate trunk, and ascends tlience over the first rib in its course to the upper limb. With this difference on the two sides in the origin of the subclavian — the one vessel beginning opposite the sterno- clavicular articulation, the other in the thorax — it is evident that the length and connections of the part of the artery on the inner side of the scalenus must vary much on opposite sides. First part. The part of the artery internal to the anterior scalenus is much longer on the left than the right side, and is almost vertical in direc- tion, instead of being horizontal like its fellow. After leaving the chest it is deeply placed in the neck, near the spine and the cesophagus, and does not rise usually so high above the first rib as the right subclavian. Between the artery and the surface are structures like those on the right side, viz., the common teguments with the platysrna and deep fascia, and the sterno-mastoid, hyoid, and thyroid muscles. Behind the vessel is the longus colli muscle. To the inner side are the oesophagus and the thoracic duct; and the pleura is in contact with the outer and anterior ])arts. Its connections lower in the chest are described in the dissection of the thorax. Veins. The internal jugular vein is superficial to the artery and paral- lel to it. Ney'ves. The pneumo-gastric nerve lies parallel to the vessel instead of across it as on the right side; and the phrenic nerve crosses over it close to the scalenus. Accompanying the artery are the cardiac branches of the sympathetic, which course along its inner side to the chest; and beneath it is the inferior cervical ganglion. The second and parts of the artery, viz., beneath and beyond ENDING OF THORACIC DUCT. 119 the scalenus, are nearly the same as on the right side (p. 76); but the student must note for himself the variations that may exist in the connec- tions. The branches of this artery resemble so closely those of the right trunk, that one description will serve for both (p. 76 to 78). It may be re- marked, that the superior intercostal of the left side is usually internal to, instead of beneath the scalenus as on the right side; in other words, this branch arises sooner. The thoracic duct (fig. 27, ®) conveys the chyle and lymph of the greater part of the body into the venous circulation. Escaping from the thorax on the cesophagus, the duct ascends in the neck as liigh as the seventh or sixth cervical vertebra. At the spot mentioned it issues from beneath the carotid trunk, and arches outwards above or over the subcla- vian artery, and in front of the scalenus muscle and the phrenic nerve, to open into the subclavian close to the union vvdth the internal jugular vein. Double valves, like those of the veins, are present in the interior of the tube ; and a pair guards the opening into the posterior part of the vein, to prevent the passage of the blood into it. P^requently the upper part of the duct is divided; and there may be separate openings into the large vein, corresponding with those divisions. Fig. 27. Diagram of the Ending op the Lymph Duct and the Thoracic Duct in the Veins. 1. Upper vena cava. 8. Thoracic duct. 2. Right, and 3, left innominate vein. 9. A lymphatic vessel joining the right lym- 4. Left, and 5, right internal j ugular, phatic duct, as this is about to end in 6. Left, and 7, right subclavian vein. the subclavian vein. Large lymphatic vessels from the left side of the head and neck, and from the left upper limb, open into the upper part of the duct, and some- times separately into the vein (^®). Structure. This tube is formed of three coats like the bloodvessels, viz., inner, middle, and outer. The inner is an elastic layer of longitudi- nal fibres covered by flattened epithelium; the middle is muscular and elastic with transverse fibres; and the outer is constructed chiefly of fibrous tissues arranged longitudinally and obliquely. Examine next the brachial and cervical plexuses, using the description of the right side (p. 79 to 81). 120 DISSECTION OF THE NECK. Common carotids. On opposite sides these vessels have differences like those between the right and left subclavian arteries; for the left ves- sel arises from the arch of the aorta, and is therefore deep in the chest, and longer than the right. The description of the artery between its origin and the top of the sternum will be included in the dissection of the thorax. Beyond the sterno-clavicular articulation the vessels, on both sides, so nearly resemble one another that the same description may serve for the two (p. 81 ). On the left side, however, the jugular vein and the pneumo- gastric nerve are much nearer to the carotid than on the right side, and are placed over the artery in the lower third of the neck.^ Parts in the upper aperturk of the thorax. The relative po- sition of the several parts entering or leaving- the thorax by the upper opening may be now observed. In the middle line lie the remains of the thymus gland, and the trachea and oesophagus. In front of the trachea are the lower ends of the sterno- hyoid and sterno-thyroid muscles with layers of the cervical fascia, and the inferior thyroid veins; and behind the gullet and windpipe is the longus colli muscle. Between the two tubes is the recurrent nerve on the left side. On each side the bag of the pleura and the apex of the lung project into the neck ; and in the interval between the pleura and the trachea and oeso]i)hagus, are })laced the vessels and nerves })assing between the thorax and the neck. Most anteriorly on both sides lie the innominate vein, the phrenic nerve, and tlie internal mammary artery ; but the vessels and nerves next met with are different on tlie two sides. On the right side come the innominate artery, with the vagus, the cardiac nerves, and the right lymphatic duct ; but on the left side are the left vagus, the left com- mon carotid artery, the thoracic duct, and the left subclavian artery with the cardiac nerves. Lastly, altogether behind on each side are part of the first intercostal nerve, the cord of tlie sympathetic, and the superior inter- costal artery. The THYROID BODY is a soft reddish mass, which is situate opposite the upper part of the trachea. It consists of two lobes, one on each side, which are united by a narrow piece across the front of the windpipe. The connecting piece, about half an inch in depth, is named the isthmus^ and is placed o[)posite the second and third rings of the air tube. Each lobe is somewhat conical in shape, with the smaller end upwards, and is about two inches in length. It is interposed between the Avindpipe and the sheath of the common carotid artery, and is covered by the sterno- thyroid, sterno-hyoid, and omo-hyoid muscles. The extent of the lobe varies ; but usually it reaches as high as the middle of the thyroid cartilage, and as low as the sixth ring of the tracliea. From the upjier part of the thyroid body, and most commonly from the left lobe, a conical piece — pyramid, ascends towards the hyoid bone, to Avhich it is connected by a fibrous band. Sometimes this part is attached to tlie os hyoides by a slip of muscle, the levator ylandidce thyroidece of Soemmering. This body is of a brownish red or purple hue, is granular in texture, and weighs from one to two ounces. Its size is larger in the woman than ' Occasionally these ditlerences will be reversed — the A'eiii and nerve being over the artery on the right side, and away from it on the left. THYROID BODY. 121 ill the man. On cutting into the gland a viscid yellowish fluid escapes. It has not any excretory tube or duct. Structure. The thyroid body is not provided with a distinct capsule ; but it is surrounded by areolar and tine elastic tissues, which project into the substance and divide it into masses. The substance of the gland consists of spherical or elongated vesicles, which vary in size, some being as large as the head of a small pin, and others only gi^th of an inch. These vesicles are simple sacs, distinct from one another, and contain a yellowish fluid with corpuscles. The wall of the vesicles consists of a thin proper membrane with a nucleated epithelial lining. Fine vessels and areolar tissue unite together the vesicles into small irregular masses or lobules of the size of the little Anger nail. The arteries of the thyroid body are two on each side — superior and inferior thyroid. The branches of the external carotids (superior thyroid) ramify chiefly on the anterior aspect ; while those from the subclavians (inferior thyroid) pierce the under surface of the body. A very free com- munication is established between all the vessels ; and in the substance of the thyroid body the arteries form a capillary network around the vesicles. Occasionally there is a third thyroid branch {art. thyroid, ima) which arises from the innominate artery into the thorax, and ascending in front of the trachea assists in supplying the thyroid body. The veins are large and numerous ; they are superior, middle, and infe- rior thyroid on each side. The first two enter the internal jugular vein (p. 82). The inferior thyroid vein issues from the lower part of the thy- roid body, and descends on the trachea — the two forming a plexuse on that tube beneath the sterno-thyroid muscles ; it enters finally the innomi- nate vein of its own side. The TRACHEA, or air tube, is continued from the larynx to the thorax, and ends by dividing into two tubes (bronchi) one for each lung. It occu- pies the middle line of the body, and extends commonly from the fifth cervical to the fourth dorsal vertebra, measuring about four inches and a half in length, and nearly one in breadth. The front of the trachea is rounded in consequence of the existence of firm cartilaginous bands in the anterior wall, but at the posterior aspect the cartilages are absent, and the tube is flat and muscular. The cervical part of the trachea is very movable, and has the following relative position to the surrounding parts. Covering it in front are the small muscles reaching from the sternum to the hyoid bone, with the deep cervical fascia : beneath those muscles is the inferior thyroid plexus of veins ; and near the larynx is the isthmus of the thyroid body. Behind the tube is the msophagus, with the recurrent nerves. On each side are the common carotid artery and the thyroid body. The structure of the trachea is described in Section XYII. The cESOPHAGUS, or gullet, reaches from the pharynx to the stomach. It commences, like the trachea, opposite the fifth cervical vertebra, and ends opposite the tenth dorsal vertebra. The tube reaches through j)art of the neck, and through the whole of the thorax ; and occupies the middle line of the body. In length it measures about nine inches. In the neck its position is behind the trachea till near the thorax, where it projects to the left side of the air tube, and touches the thyroid body and tlie thoracic duct. Behind the oesophagus is the longus colli muscle. On each side is the common carotid artery, the proximity of the left b(ung greatest because of the projection of the cjesophagus towards the same side. 122 DISSECTION OF THE PHARYNX. The structure of the oesophagus will be examined in the dissection of the thorax. Directions. The dissector may learn next the digastric and stylo-hyoid muscles, with the hypoglossal nerve (p. 82). Afterwards he may take the trunk of the external carotid, with the following branches — superior thyroid, facial, occipital, posterior auricular, and superficial temporal (p. 83 to 87). The dissector is not to examine now the ptery go-maxillary or snb- maxillary regions on the left side, because such a proceeding would inter- fere with the subsequent dissections. Before learning the pharynx he should lay bare, on tliis side, the middle and inferior ganglia of the sym- pathetic with their branches. Dissection. For the display of the two lower ganglia of the sympathetic and their branches, it will be necessary to take away the great bloodvessels by cutting them across at the lower part of tlie neck, and near the digastric muscle. In removing the vessels, care must be taken of the sympathetic beneath them. The middle ganglion must be sought in the fat and areolar tissue near the inferior thyroid artery ; and the inferior one will be seen on the neck of the first rib, after the subclavian artery has been divided. The upper cardiac nerve may be found descending beneath the carotid sheath. The upper end of the sternum with its attached clavicle is to be taken away next, by cutting through the middle of the first rib ; and the piece of bone is to be put aside for the subsequent examination of the sterno- clavicular articulation. The middle and inferior cervical ganglia of the sympathetic nerve are so similar to the corresponding ganglia of the right side, that the same description will suffice (p. 117). The cardiac nerves are three in number on tlie left as on the right side, viz., superior, middle, and inferior, but they present some differences. The superior cardiac nerve has a similar course in the neck on both sides ; but the left in entering the chest lies between and parallel to the carotid and subclavian arteries. The middle cardiac nerve unites frequently with the next, and passes beneath the subclavian artery to the deep cardiac plexus. The inferior cardiac nerve is generally a small branch, which enters the thorax conjoined with the preceding, to end in the cardiac plexus. Section XL DISSECTION OF THE PHARYNX. The pharynx, or the commencement of the alimentary passage, can be examined only when it has been se{)ara.ted from the rest of the head ; and it will tlierefore be necessary to cut through the base of tlie skull in the manner mentioned below, so as to have tlie anterior half, with the pharynx connected to it, detached from the posterior half. Dissection. The block being removed from beneath the neck, the head is to be placed downwards, so that it may stand on the cut edge of the skull. Xext the trachea and oesophagus, together with the vagus and PREPARATION OF PHARYNX. 123 sympathetic nerves, are to be cut near the first rib, and all are to be sepa- rated from the spine as high as the basilar process of the occipital bone ; and Mdtbout injuring, on the left side, the vessels and nerves near the skull. For the division of the skull turn upwards the inner surface of the base, and make the following incisions in the posterior fossa. On the right side a cut, Avitb the chisel, is to be carried along the line of union of the petrous part of the temporal with the occipital bone. On the left side an- other cut with the cliisel is to be made in the same direction, but through the occipital bone internal to the foramen jugulare and the inferior petrosal sinus : this is to begin rather behind that foramen, and to end opposite the one on the other side. The skull is to be sawn through vertically on the left side close behind the mastoid part of the temporal bone, so that the incision shall meet the outer end of the cut made with the chisel. Finally placing the skull again upside down, let the student chisel through the basilar process of the occipital bone between the attachments of tl e pharynx and the muscles of the spinal column, the instrument being directed backwards^ Tlie base of the skull is now divided into two parts (one liaving the pharynx attached to it, the other articulating with the spine), whicli can be readily separated with a scalf)el. The spinal column with the piece of the occipital bone connected with it should be set aside, and kept for after examination. Dissection of the 'pharynx (fig. 28). Let the student take the anterior part of the divided skull, and, after moderately filling the pharynx with tow, fasten it with hooks on a block, so that the cesophagus may be pen- dent and towards him. On the left side of the pharynx a different view from that of the right side may be obtained of the cranial and sympathetic nerves near the skull (p. 112), when some loose areolar tissue, and the styloid process with its muscles, have been removed : if the lower ends of the nerves are fixed with pieces of thread, a more satisfactory examination can be made of them. Afterwards the dissector may proceed to remove the fascia from the constrictor muscles of the right side (fig. 28), in the direction of the fibres — these radiating from the side to the middle line. The margins of the two lower constrictor muscles (middle and inferior) are to be defined. Beneath the lower one near the larynx, will be found the recurrent nerve with vessels ; whilst intervening between the middle and superior, are the stylo-pharyngeus muscle and the glosso-pharyngeal nerve. To see the attachment of the superior constrictor to the lower jaw and the pterygo-maxillary ligament, it will be necessary to cut through the in- ternal pterygoid muscle of the right side. Above the upper fibres of this constrictor, and near the base of the skull, are two small muscles of the palate (F and H) entering the pharynx : one — tensor palati, lies between the internal pterygoid plate and muscle ; and the other — levator })jilati, is farther in, and larger. The PHARYNX is situated behind the nose, mouth, and larynx. Its extent is from the base of the skull to the cricoid cartilage of the larynx, where it ends in the oesophagus. In form it is somewhat conical, with the dilated part upwards ; and in length it measures from five to six inches. The tube of the pharynx is incomplete in front, where it communicates with the cavities above mentioned, but is quite closed behind. On each side of it are placed the trunks of the carotid arteries, with the internal 124 DISSECTION OF THE PHARYNX. / jugular vein and the accom})anying cranial and sympathetic nerves. Behind it is the spinal column, covered by muscles, viz., longus colli and rectus capitis anticus major. In front the {)harynx is united to the larynx, the hyoid hone and the tongue, and to the bony framework of the nasal cavity ; but behind it is unattached, and is formed chiefly of thin, fleshy strata. In the posterior wall are contained elevator and constrictor muscles ; and at the upper part the bag is further completed by an a[)oneurotic expansion which fixes it to the base of the skull. The whole is lined by mucous membrane. The aponeurosis of attachment is seen at the upper part of the pharynx, where the muscular fibres are absent, to connect the tube to the base of the skull, and to complete the posterior boundary. Superiorly it is fixed to the basilar process of the occipital, and the petrous part of the temporal bone, as well as to the cartilage between the two ; but inferiorly it becomes thin, and extends between the muscular and mucous strata. On this mem- brane some of the fibres of the constrictor muscles terminate. The CONSTRICTORS are three thin muscles, which are arranged like scales, the lower partly overlaying the middle, and the -middle the upper. The inferior constrictor (fig. 28, the most superficial and lowest, arises from the side of the cricoid cartilage ; from the oblique line and U})per and lower borders of the thyroid cartilage, and from the part of the latter which is behind the oblique line. The origin is small when com- pared with the insertion, for the fibres are directed backwards, radiating, and are inserted into a raphe along the middle line, where it meets the corresponding muscle of the opposite side. The outer surface of the muscle is in contact with the sheath of the carotid artery, and with the muscles covering the spinal column. The lower border is straight, and is continuous with the fibres of the oesopha- gus ; whilst the iq)per border overla})S the fibres of the middle constrictor (b). The recurrent nerve and vessels (^) enter beneath the lower border. The middle constrictor (fig. 28 has nearly the same shape as the pre- ceding, that is to say, it is narrowed in front and expanded behind. Its fibres arise from the great cornu of the os hyoides, from the small cornu of the same bone, and from the stylo-hyoid ligament. From this origin the fibres radiate, and are blended along the middle line with the other muscles. The surfaces have connections similar to those of the preceding con- strictor. The upper border is sejiarated from the superior constrictor by the stylo-])haryngeus muscle u, and ends on the aponeurosis of the pharynx, al)Out an inch from the base of the skull. The lower border descends beneath the inferior constrictor ; and opposite the interval between the two is the upper laryngeal nerve (^). The superior constrictor (fig. 28 is the least strong of the three muscles, and wants the usual conical form. Its origin is extensive, and is connected successively, from above down, with the inner surface of the internal pterygoid plate (the lower third or less), with the pterygo-maxil- lary ligament, with the posterior ])art of the mylo-hyoid ridge of the lower jaw, and with the mucous membrane of the mouth and tlie side of the tongue. The fleshy fibres })ass backwards, and are inserted on the aponeu- rosis of the pharynx, as well as into the raphe along the middle line. The [)arts in contact externally with this muscle are, the deep vessels and nerves of the neck ; and internally it is lined by the aponeurosis and the mucous membrane. The upper border consists of arclied fibres which CONSTRICTOR MUSCLES. 125 are directed backwards from tlie pterygoid plate; and above it the levator palati muscle r is seen. The lower border is overlaid by the middle con- strictor muscle. The attachment to the pterygo-maxillary ligament cor- responds with the origin of the buccinator muscle i. Fi< 28 . External View of the Pharynx (Illnsti-atioas of Dissections). Muscles : A. Inferior constrictor. B. Middle constrictor, c. Upper constrictor. D. Stylo-pharyngeiis. F. Levator palati. H. Tensor palati. I. Buccinator. K. Hyo-glossus. Nerves : 1. Glosso-pharyngeal. 2. Hypo-glossal. .3. Superior laryngeal. 4. External laryngeal. 5. Recurrent laryngeal. 6. Gustatory nerve. Action of constrictors. The muscles of both sides contracting will diminish the size of the pharynx ; and as the anterior attachments of the lower muscles are nearer together than those of the upper, the tube will be contracted more behind the larynx than near the head. In swallowing the morsel is seized first by the middle constrictor, and is delivered over to the inferior, by whicli it is conveyed to the oesopha- gus : both muscles act involuntarily. By the contraction of the ipiper muscle the space above the mouth will be narrowed, so that the soft palate being raised, the upper portion of the pharyngeal space can be shut off from the lower. 126 DISSECTION OF THE PHARYNX. Dissection (fig. 29). Open the pharynx by an incision along its mid- dle, and, after removing the tow from tlie interior, keep it open with hooks: a better view of the cavity will be obtained by partly dividing the occipital attachment on each side. The mucous membrane is to be care- fully removed below the dilated extremity of the Eustachian tube on the right side, for the [>urpose of finding some pale muscular fibres, salpingo- pharyngeus c, which descend from it. The ELEVATORS of the pharynx are two in number on each side — an external (stylo-pharyngeus), and an internal (salpingo-pharyngeus). The stylo-pharyngeus (external elevator) may be read again with the pharynx. Its description is given in p. 106. Salpingo-pharyngeus^ c (internal elevator). This little band is fixed by tendon to the lower border of the cartilage of the Eustachian tube near the orifice. Its fleshy fibres end below by joining those of the palato- pharyngeus Q. If the part is not tolerably fresh the muscle may not be visible. Action. This thin muscle elevates the upper and lateral part of the pharynx above the spot where the large external elevator enters the wall ; but it is probably used chiefly in opening the Eustachian tube in swal- lowing. The interior of the pharynx (fig. 29) is wider from side to side than from before back, and its greatest width is opposite the hyoid bone; from that spot it diminishes both upwards and downwards, but much more rapidly in the latter than in the former direction. Through the part of the passage above tlie mouth the air moves in respiration; whilst thi*ough that below the mouth both air and food are transmitted — the air passing to the aperture of the windpipe, and the food to the oesophagus. In it the following objects are to be noticed: — • At the top are situate the posterior apertures, G, of the nasal cavity, which are se[)arated by the septum nasi; and below them hangs the soft ])alate, partly closing the cavity of the mouth. By the side of each nasal aperture ds the trumpet-sha[)ed end of the Eustachian tube, F. Below the soft palate, the opening into the mouth — isthmus faucium, II, is to be recognized; and on each side of this is the tonsil, K, which is placed in a hollow between two prominences named pillars of the soft palate — the one, i, proceeding from the soft palate to the side of the tongue, and the other, l, from the same part to the side of the pharynx. Next in order, below the mouth, comes the aperture of the larynx, N; and close in front of it is the epiglottis, or the valve which assists to close that opening during deglutition. Lowest of all is the opening, o, from the pharynx into the oesophagus. The apertures into the pharynx are seven in number, and have the following })Osition and boundaries: — The posterior openings of the nasal fossce, G, are oval in form, and measure about an inch fi'om above down, but only half an inch across. Each is constructed in the dried skull by the sj)henoid and palate bones above, and by the palate below ; by the vomer inside, and the internal pterygoid plate outside; and it is lined by mucous membrane. The Eustachian tube., F, is a canal, partly osseous, partly cartilaginous, by which the tym[)anic cavity of the ear communicates with the exter- nal air. If the mucous membrane be removed from the tube on the right side, the cartilaginous part appears to be nearly an inch long. It is narrow OPENINGS OF PHARYNX. 127 superiorly, where it is fixed to the margins of a groove between the petrous part of the temporal and the sphenoid bone; but it increases in width as it is directed downwards to the pharynx, and ends by a wide aperture inside the internal pterygoid plate, on a level with tlie inferior meatus. Its opening in the pharynx is oval in form; and the inner side, which is larger than the outer, projects forwards, giving rise to a trumpet-shaped mouth. Fig. 29. A. Levator palati. B. Tensor palati. c. Salpingo-pharyiigeus. B. Azygos uvulai. E. Internal pterygoid muscle. F. End of the Eustachian tube. G. Posterior navis. H. Mouth cavity. I. Anterior pillar of the fauces. K, Apertures of the tonsil. L. Posterior pillar of the fauces. N. Opening of the larynx. o. Opening of the oesophagus. p. Uvula. Q. Superficial part of Palato-pharyn- geus. Internal View of the Phaknyx (Illustrations of Dissections). Muscles of the Palate, and NAMED Parts. This part of the tube is constructed by a triangular piece of cartilage, whose margins are bent downwards so as to inclose a narrow space; but at the under aspect the cartilage is deficient, and the wall is formed by fibrous membrane. Closely united to the pterygoid plate, the tube is covered by the mucous membrane; and through it the mucous lining of the cavity of the tympanum is continuous with that of the pliarynx. Tlie space included between the root of the tongue and the arches of the soft palate on opposite sides is called the fauces. It is wider below than above ; and on each side lies the tonsil. 128 DISSECTION OF THE PHARYNX. The isthmus faucium^ ii, is the narrowed aperture of communication between the mouth and the fauces, whose size is altered by the elevated or pendent position of tlie soft palate. Laterally it is bounded by the anterior arches of the soft palate, which are named of the fauces. The aperture of the larynx., n, is wide in front, where it is bounded by the epiglottis, and pointed behind between the arytjenoid cartilages. The sides are sloped from before back, and are formed by folds of the mucous membrane extending between the arytrenoid cartilages and the epiglottis. Posteriorly it is limited by the cornicula laryngis, and by the arytrenoid muscle covered by mucous membrane. During respiration this aperture is unobstructed, but in the act of deglutition it is closed by the epiglottis. The opening into the oesophagus., o, is the narrowest part of the pha- rynx, and is opposite tlie cricoid cartilage and the fifth cervical vertebra. Internally the mucous membnine in the oesophagus is paler than that in the pharynx : and externally the point at which the pharynx ends is marked by a slight contraction, and by a change in the direction of the muscular fibres. The SOFT FALATE, Q (velum pendulum palati), is a movable structure between the mouth and the pharynx, which can either close the opening of the mouth, or cut off' tlie passage to the nose, according as it is de- pressed or elevated. In the usual position of the soft palate (the state of relaxation) the anterior surface is somewhat curved, and is continuous with the roof of the mouth, whilst the opposite surface is convex and turned to the pharynx. The upper border is fixed to the posterior margin of the hard palate ; and eacli lateral part joins the pharynx. Tlie lower border is free, and presents in the centre a conical pendulous part — the uvula., p. Along its middle is a slight ridge, indicative of the original separation into two halves. Springing from the lower part of the soft palate, near the uvula, are two folds on each sides, containing muscular fibres, which are directed down- wards on the sides of the fauces. These are named arches or pillars of the palate., and are distinguished from one another by their relative position. The anterior., i, reaches from the fore part to the side of the tongue near the middle ; and the posterior., l, longer than the other, is continued from the lower border to the side of the pharynx. As they diverge from their origin to their termination, they limit a triangular space in which the ton- sil lies. The velum consists of an aponeurosis, with muscles, vessels, nerves, and mucous glands ; and the whole is enveloped by the mucous membrane. Dissection Some of the muscles of the palate are readily displayed, but others require care in their dissection. On the right side the two principal muscles of the soft palate — the ele- vator and tensor, are very plain. Idiese have been partly dissected on the right side ; but to follow them to their termination, let the upper attach- ment of the pharynx on the same side, and the part of the superior con- strictor which arises from the internal pterygoid plate, be cut through. The levator will be fully laid bare by the removal of the mucous mem- brane, and a few muscular fibres covering its lower part. The tendon of the tensor palati should be followed round the hamular process of the pterygoid plate ; and its situation in the j)alate beneath the levator should be made evident. The position of the Eustachian tube with respect to those muscles should be ascertained. MUSCLES OF PALATE. 129 On the left side, the mucous membrane is to be raised witli great care from the posterior surface of the palate, to obtain a view of the superficial muscular fibres. Immediately beneath the mucous covering are some fine transverse fibres of the palato-pharyngeus muscle; and beneath them, in the middle line, are the longitudinal fibres of the azygos uvulie. A deeper set of fibres of the palato-pharyngeus is to be followed, on the right side, beneath the levator and azygos muscles. The student should remove next the mucous membrane from the mus- cular fibres contained in the arches of the palate, and should follow these upwards and downwards. In order to see them in the anterior fold, it will be necessary to take the membrane from the anterior surface of the palate. If the part is not tolerably fresh, some of the i)aler fibres may not be visible. Aponeurosis of the soft palate. Giving strength to the velum is a thin but firm aponeurosis, which is attached to the hard palate. This mem- brane becomes thinner as it descends in the velum; and it is joined by the tendon of the tensor palati muscle. The MUSCLES of the soft palate are four on each side, — an elevator and tensor; with the palato-glossus and palato-pharyngeus, which act as de- pressors. In addition there is a small median azygos muscle. The LEVATOR PALATI (fig. 29, is a thick, roundish muscle, which is partly situate outside the pharynx. It arises from the under surface of the apex of the petrous portion of the temporal bone (fig. 30,^), and from the inner and hinder part of the cartilage of the Eustachian tube. Tlie fibres enter the pharynx above the superior constrictor, and then spread out in the soft palate, where they join along the middle line with those of tlie muscles of the opposite side. Outside the pharynx this muscle rests against the Eustachian tube. In the palate it forms a stratum that reaches the whole depth of that struc- ture, and is embraced by two planes of fibres of the palato-pharyngeus (*). Action. It tilts backwards the free edge of the soft palate towards the pharynx so as to enlarge the isthmus faucium, and to shut off* with the contracted pharynx the nose openings. In swallowing the palate is raised, and is arched over the bolus passing from the mouth to the pharynx. For its action on the Eustachian tube, see Tensor palati. The TENSOR vel circumflexus palati (fig. 29, arises like the preceding outside the pharynx, and is a thin riband-like band, situate between the internal pterygoid plate and muscle. About one inch and a half wide at its origin, it is attached to the slight depression (scaphoid fossa) at the root of the internal pterygoid plate, to the outer and forepart of the Eustachian tube, and still further out to the spinous process of the sphenoid, and tlie vaginal (tympanic) process of the temporal bone. In- feriorly the fleshy filires end in a tendon which, entering the pharynx between the attachments of the buccinator muscle, is reflected round the hamular process (fig. 30, ^), and is inserted into about one-third of an inch of the posterior border of the palate, viz., from the central spine to a pro- jecting point; and interiorly into the aponeurosis of the velum. As the tendon winds round the bone, it is thrown into folds; and be- tween the two is a bursa. In the soft palate it lies beneath the levator muscle. The Eustachian tube is directed inwards between this muscle and the preceding. Action. Acting from the skull the muscle will fix and make tense the 9 130 DISSECTION OF THE PHARYNX. lateral part of the soft palate; hat its movements will be very limited, seeing that the tendon is inserted partly into the palate bone. Fig. 30. 1. Azygos uvulae. 2. Tensor palati. 3. Levator palati. 4. Palato-pharyngeus — upper end. 5. External pterygoid. If the soft palate is fixed by the depressor muscles, the levator and tensor, and the salpingo-pharyngeus, taking their fixed points below, open the Eustachian tube in swallowing. The PALATO-GLOSSUS MUSCLE (constHctor isthmi faucium) is a small, pale band of fibres, which is contained in the anterior arch, i, of the soft palate. It is connected inferiorly with the lateral surface and the dorsum of the tongue; from this S})Ot the fibres ascend before the tonsil to the anterior aspect of the soft palate, where they form a thin muscular stratum, and join those of the fellow muscle along the middle line. At its origin the muscle is blended with the glossal muscles, and at its insertion it is placed before the tensor palati. Action. The palato-glossus narrows the isthmus of the fauces; the mus- cles of opposite sides moving inwards towards each other, and separating from the mouth the morsel to be swallowed. When the tongue is fixed the muscle will render tense and draw down the soft palate. The PALATO-PHARYNGEUS is mucli larger in size than the preceding, and gives rise to the eminence of the posterior pillar, l, of the soft palate. Tlie muscle is attached below to the posterior border of the thyroid carti- lage, some fibres blending with the contiguous portion of the pharynx ; and it decussates across the middle line with corresponding fibres of the muscle of the opposite side (JMerkel).^ Ascending thence behind the tonsil, the fibres enter the side of the palate, and separate into two layers (fig. 30, *). The posterior, thin and in contact with the mucous mem- brane, joins at the middle line a like offset of its fellow. The deeper or anterior stratum, much the strongest, enters the substance of the palate between the levator and tensor, and joins at the middle line the corre- sponding part of the opposite muscle, whilst some of the upper fibres end on the aponeurosis of tlie palate. • Dr. Merkel, in the work before referred to, states that this muscle has no firm fixed attachment below, and that it ends altogether in the wall of the pharynx, decussating with the muscle of the opposite side. This assertion does not accorcl with my experience. THE TONSIL. 131 In the palate the muscle incloses the levator palati and azygos uvulae between its two strata. Action. Taking its fixed point at the thyroid cartilage the muscle de- presses and makes tense the soft palate. During the act of swallowing both muscles move back the lower edge of the soft palate towards the pharynx; and approaching each other, form an oblique plane for the downward direction of tlie food ; in that state the uvula lies in the interval between the two. Tlie AZYGOS UVULAS (fig. 29, is situate along the middle line of the velum near the posterior surface. The muscle consists of two narrow slips of pale fibres, which arise from the spine at the posterior border of the hard palate, or from the contiguous aponeurosis, and end interiorly in the tip of the uvula. Behind tliis muscle, separating it from the mucous membrane, is the thin stratum of the palato-pharyngeus. Action. Its fibres elevate the uvula, shortening the mid part of the soft palate, and direct that process backwards. The tonsil^ k, is a collection of follicular capsules resembling those on the dorsum lingua^, which is placed close above the base of the tongue, and between the arches of the soft palate. Each is roundish in shape, but variable in size ; and apertures are apparent on its surface. Externally the tonsil is situate oj)posite the superior constrictor muscle and the angle of the lower jaw ; and when enlarged it may press against the internal carotid bloodvessel. The ai)ertures on the surface lead to rounded terminal recesses or hol- lows Avhich are lined by mucous membrane. Around each recess is a layer of small closed capsules, which are seated in the tissue beneath the mucous membrane, and are filled with a grayish substance containing cells and nuclear-looking bodies. No openings from the capsules are to be recognized in the recesses. Its arteries are numerous and are derived from the facial, lingual, as- cending pharyngeal, and internal maxillary branches of the external carotid. Its veins have a plexiform arrangement on the outer side. Nerves are furnished to it from the fifth and glosso-pharyngeal nerves. The mucous membrane of the 'pharynx is continuous anteriorly with the lining of the mouth, nose, and larynx. Covering the soft palate and its numerous small glands (palatine), the membrane is continued to the ton- sils on each side, and is prolonged by the Eustachian tube to the tym- panum. In front of each arytajnoid cartilage it incloses a mass of muci- })arous glands (arytoonoid). Inferiorly, it is continued by the oesophagus to the stomach. The mucous membrane is provided with more glands in the upper, than in the lower part of the pharynx ; and its character, near the different apertures, resembles that of the membrane lining the cavities communi- cating with the pharynx. Its epithelium is scaly below the nares (Henle) ; but is columnar and ciliated above that spot, where only the air is trans- mitted. Beginning of the oesophagus. This tube is much smaller than the pha- rynx, and the walls are flaccid. For the commencement, and its connec- tions in the neck, see p. 121. The gullet consists of two layers of muscular fibres, with a lining of mucous membrane. The external layer is formed of longitudinal fibres, which begin opposite the cricoid cartilage by three bundles, anterior and two lateral ; the former is attached to the ridge at the back of the carti- 132 CAVITY OF THE MOUTH. la^e, and the others join the inferior constrictor. The internal layer ^ on the other hand, is formed of circular fibres, which are continuous with those of the inferior constrictor. The structure of the oesophagus is de- scribed more fully in the dissection of the thorax. Section XII. CAVITY OF THE MOUTH. The cheeks, the lips, and the teeth are to be examined with the mouth, as all may be considered accessory parts. The Mouth. The cavity of the month is situate below that of the nose, and extends from the lips in front to the isthmus of the fauces be- hind. Its boundaries are partly osseous and partly muscular, and its size depends upon the position of the lower jaw bone. When the lower jaw is moderately removed from the upper, the mouth is an oval cavity with the following boundaries. The roo}\ concave, is constituted by the hard and soft palate, and is limited anteriorly by the arch of the teeth. In the -door is the tongue, bounded by the arch of the lower teeth ; and beneath the tip of that body is the frsenum linguie, with the sublingual gland on each side. Each lateral boundary consists of the cheek and the ramus of the lower jaw ; and in it, near the second molar tooth in the upper jaw, is the opening of the parotid duct. The anterior opening of the mouth is bounded by the lips ; and the posterior corresponds with the anterior pil- lars of the soft palate. The mucous membrane is less sensitive on the hard than the soft parts bounding the mouth ; it lines the interior of the cavity, and is reflected over the tongue. Anteriorly it is continuous with the tegument, and pos- teriorly with the lining of the pharynx. The epithelium covering the membrane is of the scaly variety. Between each lip and the front of the corresponding jaw the membrane forms a small fold — ffienulum. On the bony part of the roof it blends with the dense tissue (gums) covering the vessels and nerves. On the soft palate it is smooth and thinner, and along the middle of the palate is a ridge which ends in front in a small papilla. In the floor of the mouth the membrane forms the fr^enurn lingua3 beneath the tip of the tongue, and sends tubes into the openings of the Whartonian and sublingual ducts ; whilst on each side of the frienum it is raised into a ridge by the subjacent sublingual gland. On the interior of the cheek and lips the mucous lining is smooth, and is separated from the muscles by small buccal and labial glands. Over the whole cavity, but especially on the lips, are papillie for the purpose of touch. The CHEEK extends from the commissure of the lips to the ramus of the lower jaw, and is attached above and below to the alveolar process of the jaw on the outer aspect. The chief constituent of the cheek is the fleshy part of the buccinator muscle ; on the inner surface of this is the mucous membrane ; and on the outer the integuments, with some muscles, vessels, and nerves. The parotid duct perforates the cheek near the second molar tooth of the upper jaw. CAVITY OF THE NOSE. 133 The LIPS surround the opening of the mouth ; they consist chiefly of the fleshy part of tlie orbicularis oris muscle, covered externally by integu- ment, and internally by mucous membrane. The lower lip is the larger and more movable of the two. Between the muscular structure and the mucous covering lie the labial glands ; and in the substance of each lip, nearer the inner than the outer surface, and at the line of junction of the two parts of the orbicularis, is placed the arch of the coronary artery. Teeth. In the adult there are sixteen teeth in each jaw, which are set in the alveolar borders in tlie form of an arch, and are surrounded by the gums. Each dental arch has its convexity turned forwards ; and, commonly, the arch in the maxilla overhangs that in the mandible when the jaws are in contact. The teeth are similar in the half of each jaw, and have received the following names : the most anterior two are incisors, and the one next behind is the canine tooth ; two, still farther back, are the bicuspids ; and the last three are molar teeth. Moreover, the last molar tooth has been called also “ dens sapientiae,” from the late period of its appearance. The names a])plied to the teeth indicate very nearly the part they perform in mastication ; thus the incisor and canine teeth act as dividers of the food, whilst the bicuspid and molar teeth serve to grind the aliment. The several parts of the teeth, viz., the crown, fang, and neck ; the general and special characters of those parts in the different groups of teeth ; and the structure of the different comiionents of a tooth, must be referred to in some general treatise on anatomy. Section XIII. DISSECTION OF THE NOSE. To obtain a view of the interior of the nose, it will be necessary to make a longitudinal section through the base of the skull. Whilst the student is examining the boundaries of the nose he will derive advantage from the use of a vertical section of a dried nasal cavity. Dissection. Before sawing the bone, the loose part of the lower jaw on the right side should be taken away ; further, the tongue, hyoid bone, and larynx, all united, may be detached from the opposite half of the lower jaw, and laid aside till the dissector is ready to use them. On the right side of the middle line saw through the frontal and nasal bones, the cribriform plate of the ethmoid, and part of the body of the sphenoid bone, without letting the saw descend into the nasal cavity. Next the roof of the mouth is to be turned upwards, and the soft parts are to be divided on the right of the median line opposite the cut in the roof of the nose. The saw is then to be carried through the floor of the nose and the body of* the sphenoid bone in such a direction as to come into the incision above. The piece of the skull is now separated into two parts, right and left; the right half will serve for the examination of the meatuses, and the left will show the septum nasi, after the mucous membrane has been removed. The CAVITY OF THE NOSE is placed in the centre of the bones of the face, being situate above the mouth, below the cranium, and between the 134 DISSECTION OF THE NASAL CAVITY. orbits. This space is divided into two parts — nasal fossae — by a vertical partition. Each fossa is larger below than above ; and is flattened in form, so tliat the measurement from before back or above down exceeds much tliat from within out. It communicates with both the face and the pharynx by apertures named nares, and has also apertures of communication with the sinuses in the surrounding bones, viz., frontal, ethmoid, sphenoid, and superior maxillary. The student has to examine in each fossa a roof and floor, an inner and outer wall, and an anterior and posterior opening. The roof is somewhat arched, and is formed by the cribriform plate of the ethmoid bone in the centre ; by the frontal and nasal bones, and the cartilages in front ; and by the body of the sphenoid, the sphenoidal spongy bone, and the os palati, at the jiosterior part. In the dried skull many apertures exist in it ; most are in the ethmoid bone for the branches of the olfactory nerve with vessels, and one for the nasal nerve and vessels ; in the front of the body of the sphenoid is the opening of its sinus. The floor is slightly hollowed from side to side, and in it are the palate and superior maxillary bones — their palate processes. Near the front in the dry skull is the incisor foramen leading to the anterior pala- tine fossa. The inner boundary (septum nasi) is partly osseous and partly carti- laginous. The osseous part is constructed by the vomer, by the perpen- dicular plate of the ethmoid bone, and by those parts of the frontal and nasal with which this last bone articulates. The irregular space in front in the prepared skull is tilled in the recent state by the triangular carti- lage of the septum^ which forms part of the partition between the nostrils, and supports the cartilages of the anterior aperture. Fixed between the vomer, the ethmoid plate, and the nasal bones, this cartilage rests ante- riorly on the median ridge between the superior maxillae, and projects even between the cartilages of each nostril. The septum nasi is commonly bent to one side. The outer boundary has the greatest extent and the most irregular sur- face. Six bones enter into its formation, and they come in the following order from before backwards : the nasal and superior maxillary ; the small os unguis with the lateral mass of the ethmoid bone ; and posteriorly the ascending part of the palate bone, with the internal pterygoid plate of the sphenoid bone : of these, the nasal, ungual, and ethmoidal reach only about half way from the roof to floor, whilst the others extend the whole depth. Altogether in front of the bones, the lateral cartilages may be said to con- struct part of this boundary. On this wall are three convoluted osseous pieces, named spongy or tur- binate bones, (tig. 31), which project into the cavity: — the two upper (^) and (^), are processes of the ethmoid, but the lower one (^), is a separate bone — the inferior spongy. The spongy bones are confined to a certain portion of the outer wall, and their extent would be limited by a line con- tinued nearly vertically upwards to the roof of the cavity from both the front and back of the hard palate. Between each turbinate bone and the wall of the nose is a longitudinal hollow or meatus ; and into these hollows the nasal duct and the sinuses of the surrounding bones open. The meatuses are the s[)aces arched over by the spongy bones ; and as the bones are limited to a certain part of the outer wall, so are the spaces beneath them. The upper one (fig. 31, is the smallest and straightest of the three SPONGY BONES AND MEATUSES. 135 meatuses, and occupies the posterior half of the space included by the ver- tical lines before mentioned. Into it the posterior ethmoidal sinuses open at the front ; and at its posterior part, in the dried bone, is the spheno- palatine foramen by which the nerves and vessels enter the nose. The middle meatus (tig. 31,'^) is longer than the preceding; it is curved upwards in front, and reaches all across the space referred to on the outer wall. Anteriorly it communicates by a funnel-shaped passage (infundibulum) with the frontal sinus and the anterior ethmoidal cells ; and near its middle is a small aperture, which leads into the cavity of the upper jaw. The inferior meatus (fig. 31,®) is straighter than the middle one, and rather exceeds the width of the included space on the outer wall ; and Fig. 31. 1. Upper spongy bone. 2. Middle spongy bone. 3. Inferior spongy bone. 4. Square part of the ethmoid bone. 6. Upper meatus. 7. Middle meatus. 8. Lower meatus. 9. Kudimentaiy fourth meatus. 10. Vestibule of the nasal cavity. The woodcut shows also the aper- tures of the glands of the nose. Spongt Bones and Meatuses of the Nasal Cavity. when the bone is clothed by the mucous membrane it extends still further forwards. In its front is the opening of the ductus ad nasum. Occasionally there is a small fourth or rudimentary meatus above the rest (fig. 31, ®), which communicates with a posterior ethmoidal cell. The nares. In the recent condition of the nose each fossa has a dis- tinct anterior opening in the face, and another in the pharynx ; but in the skeleton there is only one common opening in front for both sides. These apertures, and the parts bounding them, have been before described (pp. 42 and 126). The mucous membrane lining the nasal fossa is called the pituitary or Schneiderian membrane ; and from its blending with the periosteum it acquires much strength. It is continuous with the integument at the nos- tril, and with the membrane lining the pharynx through the posterior opening : moreover, it is also continuous with the mucous membrane of the eyeball, and with that of the different sinuses, viz., frontal, ethmoidal, sphenoidal, and maxillary. The foramina in the dry bones, which transmit nerves and vessels, are entirely closed by the membrane, viz., the incisor, spheno-palatine, the holes in the cribriform plate, and the foramen for the nasal nerve and 136 DISSECTION OF THE NASAL CAVITY. vessels ; but the apertures that lead to the sinuses and the orbit are only somewhat diminished by the lining they receive. The membrane is stretched over the opening of the ductus ad nasum, forming a flap or valve to close the aperture. The characters of the membrane in the lower or respiratory part of the nose differ greatly from those of the same layer in the olfactorial region near the roof. In the lower region of the nose, through which the air passes to the lungs, the membrane is thick, and closely united to the subjacent perios- teum and perichondrium ; and on the margins of the two inferior s[)ongy bones it is projected somewhat by the large submucous vessels, so as to increase the extent of surface. In the canals and sinuses it is very thin. Near the nostril it is furnished with papillm, and small hairs (vibrissoe). The surface is covered by the apertures of branched mucous glands, which are in greatest abundance, and of largest size, about the middle and posterior parts of the nasal fossa. In tlie lower part of the nose, and in the sinuses, the epithelium is of the columnar ciliated kind; but it becomes laminated or scaly in the dilatation or vestibule inside the nostril (fig. 31, Fig. 32. A. 1. Columnar epithelium at the free surface. 2. Granular or middle layer of the same. 3. Deepest layer of elongated cells placed vertically. 4. Secreting tubular glands. B. a. Pieces of the columnar epithelium greatly en- larged. 6. Olfactorial cells amongst the epithelium parti- cles. Magnified Vertical Section of the Mucous Membrane of the Nose (altered from Henle), The olfactory region (fig. 32) is situate at the top of the nasal cavity, and is confined to the surface of the roof formed by the cribriform plate of the ethmoid; to a portion of the outer wall constructed by the lateral mass of the ethmoid bone: and to a corresponding extent of the septum, viz., about one-third. The mucous membrane in the olfactory region receives the olfactory nerve, and is therefore the seat of the sense of smell. It differs much from that in the lower jiortion of the nose, for it is less strong and vascu- lar; and is of a yellowish color, which is due to pigment in the epithelium and the glands. The epitlielium (fig. 32 a) is thicker but softer here than lower in the cavity, and it is columnar on the surface, but not ciliated. Beneath the OLFACTORY NERVE. 137 surface layer are strata of granules and ovalisli cells (^), amongst which sink the pointed or attached ends of the pieces of epithelium. Around the pieces of the columnar epithelium stand numerous bodies named olfactorial cells by Schultze (fig. 32 b. *). They consist of small spindle-shaped nucleated cells, with a rounded filament prolonged from each end towards the attached and free surfaces of the mucous membrane: that to the free surface, the larger, ends on a level with the pieces of tlie columnar epithelium. But tlie connections of the deeper threads or pro- cesses are unknown; they have been supposed to unite with the olfactory nerve. The glands in the olfactory region are simple lengthened tubes (fig. 32 A. like those in the stomach, but are slightly wavy, and end in the submucous tissue by closed extremities. A flattened epithelium, with colored granular contents, lines the tubes (Henle.) Dissection. At this stage of the dissection, little will be seen of the distribution of the olfactory nerve. If the septum nasi be removed, so as to leave entire the membrane covering it on the opposite side (the left), the filaments of the nerve will appear on the surface, near the cribriform plate. In the membrane, too, near the fi’ont of the septum, is an offset of the nasal nerve. The naso-})alatine nerve and artery (fig. 33, are to be sought lower down, as they are directed from behind forwards, towards the anterior Fiff. 33. Nerves of the Septum op the Nose. 1, Olfactory bulb and its ramifications on the 3. Naso-palatine nerve from Meckel’s ganglion septum. (too large in the cut.) 2. Nasal nerve of the ophthalmic trunk. palatine fossa; the artery is readily seen, especially if it is injected, but the fine nerve, which is about as large as a coarse hair, is imbedded in the membrane and will be found by scraping with the point of the scalpel. By cutting through the fore and upper ])art of the membrane that has been detached from the sejitum nasi, other branches of the olfactory nerve may be traced on the outer wall of the nasal fossa. 138 DISSECTION OF THE HEAD. The OLFACTORY NERVE (fig. 33, forms a bulb on the cribriform yfiate of the ethmoid bone, and sends branches to the olfactory region of the nose through the apertures in the roof. These branches are about twenty in number, and are divisible into three sets. An inner set, the largest, descend in the grooves on the septum nasi, and branching, extend over the upper third. A middle set is confined to the roof of the nose. And an external set is distributed on the upper Sj)ongy bone, on the anterior square surface of the os ethmoides, and on the fore part of the middle spongy bone. As the branches of the olfactory nerve leave the skull, they receive tubes from the dura mater and pia mater, which are lost in the tissue to which the nerves are distributed. The nerves ramify in the pituitary membrane in tufts of filaments which communicate freely with the con- tiguous twigs, forming a network, but their mode of termination in the tissue is unknown. It has been suggested by Schulze that they join the deep processes or ends of the so-called olfactorial cells ; but this union has not been seen. The olfactory nerve differs in structure from the other cranial nerves ; for its branches are deficient in the white substance of Schwann, are not divisible into fibrillje, and are nucleated and granular in texture. They resemble the ganglionic fibres: and seem to consist of an extension of the nerve sid)stance of the olfactory bulb. The other nerves in the nose will be described in the following section. Bloodvessels. For a statement of the different vessels of the nose, see p. 141. The arteries form a network in the pituitary membrane, and a large submucous plexus on the edge of eaeh of the two lower spongy bones, especially on the inferior. The veins have a plexiforrn disposition like the arteries, and this is largest on the lower spongy bone and the septum nasi. Section XIV. SPHENO-PALATINE AND OTIC OANGLIA, FACIAL AND NASAL NERVES, AND BRANCHES OF THE INTERNAL MAXILLARY ARTERY. The preparation of Meckel’s ganglion and its branches (fig. 34), and of the terminal branches of the internal maxillary artery, is a somewhat diffi- cult task in consequence of the nerves and vessels being contained in osseous canals which require to be opened. As is the case with other dissections, the student seeks first the branches, and traces these to the ganglion and main trunk. Dissection. The left half of the head is to be used for the display of the ganglion and its branches; but the student may previously acquire some skill by attempting the dissection on the remains of the right side. To lay bare the branches of the palate, detacli the sof't parts in the roof of the mouth from the bone, until the nerves and vessels escaping from the [)Osterior y)alatine foramina are arrived at. Cut off, with a bone forceps, the posterior part of the hard y)alate to a level with the vessels and nerves ; and cleaning these, trace offsets beliind into the soft palate, and follow the main ])ieces forwards to the front of the mouth. Take away without injury to the naso-palatine nerve and vessels (already SPHENO-PALATINE GANGLION. 139 found), the hinder part of the loose piece of mucous membrane before de- tached from the septum nasi, and separate the mucous membrane from tlie outer wall of the nasal fossa, behind the spongy bones, as high as the spheno-palatine foramen. In reflecting forwards the membrane many branches of vessels and nerves will be seen entering it through the fora- men ; but these may be left for the present, as directions for their dissec- tion will be subsequently given. When the lining membrane of the nose has been removed behind the spongy bones, palatine nerves and vessels will appear through the thin translucent palate bone, and will be readily reached by breaking carefully through it with a chisel. Afterwards the tube of membrane containing the palatine vessels and nerves being opened, these are to be followed down to the soft palate and the roof of the mouth, and upwards to the ganglion which is close to the body of the sphenoid bone. To bring the ganglion fully into view, it will be necessary to saw through the overhanging part of the sphenoid bone, to cut away pieces of the bones surrounding the hollow in which it lies, and to remove with care the enveloping fat and the periosteum. The ganglion then appears as a flat- tened reddish-looking body, Irom which the vidian and pharyngeal nerves pass backwards. Besides the branches referred to, the student should seek two large nerves from the upper part of the ganglion to join the upper maxillary, and smaller offsets to the floor of the orbit. To trace backwards the vidian branch to the carotid plexus and the facial nerve, the student must lay open the canal which contains it and its artery in the root of the pterygoid process; and in doing this he must define the small pharyngeal branclies of nerve and artery which are super- ficial to the vidian, and lie in the pterygo-palatine canal. At the back of the pterygoid canal, a small branch from the vidian to the plexus on the internal carotid artery is to be looked for. Lastly, the vidian nerve is to be followed into the skull through the cartilage in the foramen lacerum (basis cranii), after cutting away the point of the petrous portion of the temporal bone, and dividing the internal carotid artery ; and it is to be pursued on the surface of the temporal bone, beneath the ganglion of the fifth nerve, to the hiatus Fallopii: its junction with the facial nerve will be seen with the dissection of that nerve. The branches of the ganglion to the nose will be found entering the outer surface of the detached mucous membrane opposite the splieno-pala- tine foramen, with corresponding arteries. One of these nerves (naso- palatine), before dissected in the membrane of the septum, is to be isolated, and to be followed forwards to where it enters the floor of the nose. The branches of the internal maxillary artery with the nerves are to be cleaned at the same time. The SPHENO-PALATINE GANGLION (fig. 34, ^) (ganglion of Meckel) occupies the spheno-maxillary fossa, close to the spheno-palatine foramen, and is connected with the branches of the superior maxillary nerve to the palate. The ganglionic mass is somewhat triangular in form, and of a reddish-gray color. It is situate for the most part, behind the branches (spheno-palatine) of the superior maxillary nerve to the palate, so as to sur- round only part of their fibres ; and it is prolonged posteriorly into the vidian nerve. Meckel’s ganglion resembles the other ganglia in connec- tion with the fifth nerve in having sensory, motor, and sympathetic offsets or roots connected with it. The Branches of the ganglion are distributed for the most part to the 140 DISSECTION OF THE HEAD. nose and palate, but small offsets are given to the pharynx and the orbit. Other offsets connect it with surrounding nerves. Branches of the nose. The nasal branches, from three to five in num- ber, are for tlie most part very small and soft, and pass inwards through the spheno-palatine foramen : their distribution is given below : — The superior nasal branches (f t) distributed in the mucous mem- brane on the two upper spongy bones, and a few filaments reach the back part of the septum nasi. The naso-palatine nerve (nerve of Cotunnius) (fig. 33, crosses the roof of the nasal fossa to reach the septum nasi, and descends on that par- tition to near the front. In tlie floor of the nose it enters a special canal by the side of the septum, tlie left being anterior to the other, and is con- veyed to the roof of the mouth, where it lies in the centre of the anterior palatine fossa. Finally, the nerves of opposite sides are united in the mouth, and are distributed in the mucous membrane behind the incisor teeth. On the septum nasi filaments are supplied by the naso-palatine nerve to the mucous membrane. To follow the nerve to its termination, the canal in the roof of the mouth must be opened. Fig. 34. Nerves of the Nose and Palate. 1. Olfactory nerve. 2. Olfactoiy bulb giving branches to the nose. .3. Third nerve. 4 Fourth nerve. ,5. Fiftli nerve. 6. Nasal nerve of the ophthalmic trunk. 7. Meckel’s ganglion. 8. Vidian nerve. 9. Larger palatine nerve. 10. Smaller palatine nerve. It Nasal nerve. Branches of the palate. The nerves of the palate, though connected in part with the ganglionic mass, are the continuation of the spheno-palatine branches of the superior maxillary nerve (]b 104). Below the ganglion they are divided into three — large, small, and external. The large palatine nerve (anterior) (tig. 34, ^) reaches the roof of the mouth through the largest palatine canal, and courses forwards nearly to the incisor teeth, where it joins the naso-])alatine nerve. Whilst in the canal, the nerve furnishes two or more filaments {inferior nasal t) to the SPHENO-PALATINE GANGLION. 141 membrane on the middle and lower spongy bones ; in the roof of tlie moutli it supplies the mucous membrane and glands, and gives an offset to the soft palate. The small 'palatine nerve^ 10 (posterior), lies in the smaller canal, and ends inferiorly in the soft palate, and the levator jjalati and azygos uvulae muscles ; it supplies the uvula and tonsil. The external palatine nerve is smaller than the otlier two, and de- scends in the canal of the same name. Leaving the canal, the nerve is distributed to the velum palati and the tonsil. The phar'yngeal branch is very small, and is directed through the pterygo-palatine canal to the mucous membrane of the pharynx near the Eustachian tube, in which it ends. Branches to the orbit. Two or three in number, these ascend through the spheno-maxillary fissure, and end in the fleshy layer of the 7nusculus orbitalis (p. GO). It will be necessary to cut through the sphenoid bone to follow these nerves to their termination. Connecting braiiches. The ganglion is united, as before said, with the spheno-palatine branches of the fifth nerve (fig. 24, ®), receiving sensory nerve fibres through them ; and through the medium of the vidian, which is described below, it communicates with a motor nerve (facial) and with the sympathetic nerve. The vidian nerve (®) passes backwards through the vidian canal, and sends some small filaments, through the bone, to the membrane of the back of the roof of the nose {npper posterior nasal branches). At its exit from the canal, the nerve recei\es a soft reddish offset (parotid branch) from the sympathetic on the outer side of the carotid artery. The continuation of the nerve enters the cranium through the cartilaginous substance in the foramen lacerum (basis cranii), and is directed backwards in a groove on the surface of the ])etrous part of the tem})oral bone, where it takes the name of large superficial petrosal nerve (fig. 35, ^). Lastly it is continued through the hiatus Fallopii, to join the gangliform enlargement on the facial nerve. Whilst in the temporal bone, the vidian receives a twig from the tympanic nerve. The vidian nerve is supposed to consist of motor and sympathetic fibres in the same sheath, as in the connecting branches between the sympa- thetic and spinal nerve. Directions. The student may now give his attention to the remaining nerves in the nasal cavity. Dissection. The nasal nerve is to be sought in the nose behind the nasal bone (fig. 34), by gently detaching the lining membrane, after having cut off the projecting bone. A branch is given from the nerve to the septum nasi, but probably this, and the trunk of the nerve, will be seen but imperfectly in the present condition of the part. The terminal branches of the internal maxillary artery in the spheno- maxillary fossa have been laid bare in the dissection of Meckel’s ganglion, but they may be now completely traced out. The 7iasal nerve (of the ophthalmic) (fig. 34, ®) has been already seen in the skull and orbit. Plntering the nasal fossa by an aperture at the front of the ethmoid bone, the nerve gives a branch to the membrane of the septum, and is continued in a groove behind the os nasi to the lower margin of this bone where it escapes to the surface of the nose in the face (fig. 9, ’). 142 DISSECTION OF THE HEAD. Branches. The branch to the septum (fig. 33) divides into filaments that ramify on the anterior part of tliat partition, and reach nearly to the lower border. One or tic o filaments are likewise furnished by the nerve to the mucous membrane on the outer wall of the nasal fossa ; these extend as low as the inferior spongy bone. Terminal branches of the internal maxillary artery. The branches of the artery in the spheno-maxillary fossa, which have not been examined, are the superior palatine, naso-palatine, pterygo-palatine, and vidian. The superior or descending palatine is the largest branch, and accom- panies the large palatine nerve through the canal, and along the roof of the mouth ; it anastomoses behind the incisor teeth with its fellow, and ivith a branch through the incisor foramen. This artery sup[)lies offsets to the soft palate and tonsil through the other palatine canals, and some twigs are furnished to the lining membrane of the nose. In the roof of the mouth the mucous membrane, glands, and gums, receive their vessels from it. The nasal or spheno -palatine artery enters the nose through the spheno- palatine foramen, and divides into branches : Some of these are distributed on the spongy bones, and the outer wall of the nasal fossa, and supply off- sets to the posterior ethmoidal cells. One long branch, artery of the sep- tum {art. naso. palatiiui) runs on the partition between the nasal fossce to tlie incisor foramen, through which it anastomoses with the superior pala- tine in the roof of tlie mouth ; this branch accompanies the naso-palatine nerve, and covers the septum with numerous ramifications. The pterygo-palatine is a very small branch which, passing backwards through the canal of the same name, is distributed to the lining membrane of the pharynx. The vidian or pterygoid branch is contained in the vidian canal with the nerve of the same name, and ends on the mucous membrane of the Pffistachian tube and the upper part of the pharynx. vSome small nasal arteries are furnished to the roof of the nasal fossa by the posterior ethmoidal branch of the ophthalmic (p. 5G). Also the anterior ethmoidal (internal nasal, p. 57), enters the cavity with the nasal nerve, and ramifies in the lining membrane of the fore part of the nasal chamber as low as the vestibule ; a branch passes to the face between the os nasi and the cartilage, with its nerve. Otlier offsets from the facial artery supply the part near the nostril. Veins. The veins accompanying the terminal branches of the internal maxillary artery unite in the spheno-maxillary fossa in the alveolar })lexus. Into this plexus offsets are received from the pterygoid plexus and the infraorbital vein ; and from the plexus a large trunk (anterior in- ternal maxillary) is directed forwards below the malar bone to join the facial vein ([). 40). Beneath the mucous membrane of the nose the veins have a {)lexiform arrangement, as before said. Facial nerve in the temroral bone (fig. 35). This nerve winds through the petrous i)art of the temporal bone; and it is followed with difiiculty in consequence of the extreme density of the bone, and the ab- sence of marks on the surface to indicate its position. To render this dissection easier, the student sliould be jwovided with a temporal bone, in which the course of the facial nerve and the cavity of the tympanum are displayed. FACIAL NERVE IN THE BONE. 143 Dissection. The examination of the nerve is to be begun at the stylo- mastoid foramen, and to be carried forwards from that point. With this view, the side of the skull should be sawn through vertically between the meatus externus and the anterior border of the mastoid process, so as to open the posterior part of the aqueduct of Fallopius. The nerve will be then seen entering deeply into the substance of the temporal bone ; and it can be followed by cutting away with the bone forceps all the bone pro- jecting above it. In this last step the cavity of the tympanum will be more or less opened, and the chain of bones in it laid bare. The nerve is to be traced onwards along the inner side of the tympa- num, till it becomes enlarged, and bends suddenly inwards to the meatus auditorious internus. The surrounding bone is to be removed from that enlargement so as to allow of the petrosal nerves being traced to it ; and the meatus auditorious is to be laid open, to see the facial and auditory nerves in that hollow. The course of the chorda tympani nerve (branch of the facial) across the tympanum will be brought into sight by the removal of the central ear bone, the incus. This nerve may be also followed to the facial through Fig. 35. the wall of the cavity behind, as well as out of the cavity in front. The remaining branches of the facial nerve in the bone are very minute, and are not to be seen ex- cept on a fresh piece of the skull which has been softened in acid. The student may therefore omit the para- graphs marked with an asterisk, till he is able to obtain a part on which a careful examination can be made. The facial nerve (fig. 3a, is re- ceived into the internal auditory mea- tus, and entering the aqueduct of Fallopius at the bottom of that hol- low, is conducted through the tem- poral bone to the stylo-mastoid fora- men and the face (p. 48). In its serpentine course through the bone, the nerve is first directed outwards to the inner wall of the tympanum : at that spot it bends backwards, and is marked by a gangliform swelling ( i n t u m u s c e n t i a gangliformis) , to which several small nerves are united. From tliis swelling the nerve is con- NeRVES JOININa THE ENLARGEMENT OP THE Facial Nerve. 1. Facial nerve. 2. Large superficial petrosal. 3. Small superficial petrosal from Jacobson’s nerve. 4. External superficial petrosal. 5. Chorda tympani of the facial. tinned through the arched aqueduct, to the aperture of exit from the bone. The branches of the nerve in the bone serve for the most part to con- nect it with otlier nerves ; but one supplies the tongue, and another tlie stapedius muscle. * Connectinrj branches communicate with the auditory and glosso- pharyngeal nerves ; and witli two trunks (superior and inferior maxillary) of the fifth nerve. 144 DISSECTION OF THE HEAD. * Union with the auditory nerve. In the bottom of the meatus the facial and auditory nerves are connected by one or two minute filaments. * Connecting branches of the gangliform erdargement. The swelling of the facial nerve receives three small twigs. One in front is the large superfcial petrosal nerve"^ (vidian) ; another is the small superficial petro- saC of the tympanic nerve ; and the third is the external superficial petrosal., which is derived from the sympathetic on the middle menin- geal artery. * Tlie branch of the stapedius muscle arises at the back of the tympa- num, and reaches its muscle by a special canal. Chorda tympani. Tliis long but slender branch of the facial nerve crosses the tympanum, and ends in the tongue. Arising about a quarter of an inch from the stylo-mastoid foramen (fig. 35, ^), it enters the tym- panum below the pyramid. In the cavity the nerve is directed forwards across the handle of the malleus and the membrana tympani to the Glase- rian fissure, or to an aperture on the inner side, through which it leaves the tympanum. As it issues from the cavity it emits a small branch to the laxator tympani muscle (?). Outside the skull the chorda tympani joins the gustatory nerve, and continues along it to the submaxillary ganglion and the tongue (p. 102). The AUDITORY NERVE will be learnt with the ear. Entering the audi- tory meatus with the facial it divides into two parts, of which one belongs to the cochlea, and the other to the vestibule. Otic ganglion (fig. 3G). At this stage of the dissection there is little to be seen of the ganglion, but the student should remember that it is one of the things to be examined in a fresh part. Its situation is on the inner aspect of the inferior maxillary nerve, close to the base of the skull, and it must therefore be arrived at from the inner side. Dissection. Putting the |)art in the same position as for the examina- tion of Meckel’s ganglion, the dissector should define the Eustachian tube and the muscles of the palate, and then take away the levator palati and that tube, using much care in removing the last. When some loose areolar tissue has been cleared away the internal pterygoid muscle {b) comes into view, with the trunk of the inferior maxillary nerve above it ; and a branch (internal pterygoid, descending from that nerve to the muscle. If the nerve to the pterygoid be taken as a guide, it will lead to the ganglion. To comjdete the dissection, saw vertically through the petrous part of the tem{)oral bone, near the inner wall of the tympanum, the bone being supported whilst it is divided. Taking off some membrane which covers the ganglion, the student may follow backwards a small branch to the tensor tympani muscle ; but he must open the small tube that contains the muscle, by entering it below through the carotid canal. Above this small branch there is said to be another minute nerve (small superficial petrosal), which issues from the skull, and joins the back of the ganglion. A small twig is to be sought from the front of the ganglion to the tensor palati muscle ; and one, near the same spot, to join the sympathetic nerve on the middle meningeal artery. The OTIC GANGLION (gang, auriculare, Arnold) (fig. 36) is a small reddish body, which is situate on the inner surface of the inferior maxil- lary nerve close to the skull, and surrounds the origin of the nerve to the internal pterygoid muscle. By its inner surface the ganglion is in contact with the Eustachian tube, and at a little distance, behind, lies the middle OTIC GANGLION. 145 meningeal artery. In tliis ganglion, as in the others connected with the fifth nerve, filaments from motor, sensory, and sympathetic nerves are blended. Some twigs are furnished by it to muscles. Connecting hrcinches — roots. The ganglion is joined by a fasciculus from the motor part of the inferior maxillary nerve, and is closely united with Fig. 36. a. Tensor tympaiii muscle. b. Internal pterygoid muscle with its nerve entering it. c. External carotid artery with the sym- pathetic on it. 1. Otic ganglion. 2. Branch of Jacobson’s nerve. 3. Nerve to tensor tympani. 4. Chorda tympani joining gustatory^ 5. Nerve to pterygoideus internus. 6. Nerve of tensor palati. 7. Auriculo-temporal nerve. Inner View op the Otic Ganglion. the branch of that nerve to the internal pterygoid muscle, thus receiving two of its roots, motor and sensory, from the fifth nerve. Its connection with the sympathetic is established by a twig from the plexus on the middle meningeal artery.^ Branches to muscles. Two muscles receive their nerves from the otic ganglion, viz., tensor tympani and circumhexus palati. The nerve to the tensor tympani., is directed backwards, and enters the bony canal con- taining that muscle. Tlie branch for the circumjiexns, arising from the front of the ganglion, may be supposed to be derived from the internal pterygoid nerve. The nerve of the internal pterygoid muscle., arises from the inner side of the inferior maxillary nerve near the skull and penetrates the deep surface of the muscle. This branch is joined by a fasciculus from the motor root of the fifth nerve. Directions. The remainder of the pterygo-maxillary region of the left side may be now examined. * Further, the ganglion is said to he connected with the tympanic nerve (of tlie glosso-pharyngeal) hy means of the small superficial petrosal nerve, 2, joining the posterior part. 10 146 DISSECTION OF THE TONGUE. Section XV. DISSECTION OF THE TONGUE. Directions. The tongue and larynx are to remain connected with each other whilst the student learns the general form and structure of the tongue. Dissection. The ends of the extrinsic lingual muscles that have been detached on the right side may be shortened, but enough of each should be left to trace it afterwards into the substance of the tongue. The TONGUE occupies the floor of the mouth, and is rather flattened, with the larger end turned backwards. It is free over the greater part of the surface ; but at the hinder part, and at the posterior two-thirds of the under surface, it gives attachment to the muscles and the mucous mem- brane which fix it to the parts around. The tip of the tongue (apex) touches the incisor teeth ; and the base, which looks towards the pharynx, is attached to the hyoid bone, and is connected likewise with the epiglottis by three folds of mucous membrane — a central and tw'o lateral. The upper surface of dorsum is somewhat convex, and is received into the hollow^ of the roof of the mouth ; along the anterior two-thirds it is divided into two ecjual parts by a median groove, which ends beliind in a hollow named foramen ctecum. This surface is covered with papilloe over the anterior tw^o-thirds ; but is smoother at the posterior third, though even here the surface is irregular in consequence of projecting mucous glands and follicles. The under surface, free only in part, gives attach- ment to the mucous membrane, and to the different lingual muscles con- nected with the hyoid bone and the jaw; and in front of those muscles is a fold of the mucous membrane named frsenum lingUiB. The borders of the tongue are thick and round at the base of the organ, where they are marked by vertical ridges and furrows ; but gradually be- come thinner near the tip. Papillce. On the dorsum of the tongue are the following kinds of pa- pillae; the conical and filiform, the fungiform, and the circumvallate. The conical and filiform papillie are the numerous small projections, like the villi on the mucous membrane of the small intestine, which cover the anterior two-thirds of the dorsum of the tongue. Some of the papillae (conical) are wdder at their attached than at their free ends, and these are most developed over the central part of the tongue. Others become longer (filiform), es})ecially towards the sides of the tongue. These papillae are furnished with minuter papilhe, and are provided at the ti{) with liair-like processes of the epithelium. Tow’ards their limit behind, as w^ell as on the side of the tongue, they have a linear arrangement. fungiform papillae are less numerous but larger than the preceding set, amongst whicli they are scattered. They are wdder at the free end tlian at the ])art fixed to the tongue, and project beyond the other set ; they are situate mostly at the tip and sides of the tongue. Tliey are covered wdtli small sim[)le papilla?. The circumvallate or caliciform are few'er in number and larger than the others, and are placed at the junction of the two anterior wdth the STRUCTURE OF THE TONGUE. 147 posterior tliird of the tongue: their number varies from eight to ten Tliese papillae extend across the tongue in a line resembling the letter V with the point turned backwards. Each pa{)illa consists of a central truncated part of a conical form, which is surrounded by a fold of the mucous membrane ; its wider part or base projects above the surface, whilst the apex is attached to the tongue. Both the papilla and the sur- rounding fold are furnished with smaller secondary papillae. Minute simple papillae exist behind the calciform kind, and on the under surface of the free portion of the tongue ; but they are not observed till the epithelium is removed. Taste buds. Around the circumvallate papillae is a circle of small peculiar bodies, which are covered by the e})ithelium : they are like a small carafe in sha|)e, the base resting on the corium. They are formed of elongated epithelium-like cells, of which the central, resembling olfac- torial cells, are supposed to be connected with the nerve of taste. A small collection of similar bodies occupies the back of the tongue, on each side, just in front of tlie anterior pillar of the fauces. Structure of the Papillce. The simple pa{)illaG are constructed like those of the skin, viz. of a projecting cone of membrane, which is covered by epithelium, and filled with a loop of capillaries, and a nerve. The other compound forms of the papillm may be said to be produced by outgrowths from the simple kind. Thus smaller papillary eminences spring from the common cone of limiting membrane ; and each has its separate investment of epithelium, by which the brush-like appearance on the surface is produced. From the plexus of capillary vessels in the in- terior of the papilla a looped offset is furnished to each smaller papillary projection. The entering nerve sends offsets to the different subdivisions of the papilla, on some of which end-bulbs may be recognized. Structure. The tongue consists of two symmetrical halves separated by a fibrous layer in the middle line. Each half is made up of muscular fibres with interspersed fat ; and entering it are the lingual vessels and nerves. The whole tongue is enveloped by the mucous membrane ; and a special fibrous membrane attaches it to the hyoid bone. Dissection. To define the septum, and the membrane attaching the tongue to the hyoid bone, the tongue is to be placed on its dorsum ; and, the remains of the right mylo- and genio-hyoideus having been removed, the. genio-hyo-glossi muscles are to be cleaned, and drawn from one another along the middle line. After separating those muscles, except for an inch in front, and cutting across their intercommunicating fibres, the edge of the septum will appear. By tracing the hinder fibres of the genio-hyo- glossus muscle towards the os hyoides, the hyo-glossal membrane will be arrived at. Outside this triangular muscle in the middle line, is the longitudinal bundle of the inferior lingualis, which will be better seen subsequently. Fibrous tissue. Along the middle line of the tongue is placed a thin lamina of this tissue, forming a septum : its root is attached by another fibrous structure, the hyo-glossal membrane ; and covering the greater part of the organ is a submucous layer of the same tissue. Septum. This structure forms a vertical ])artition between the two halves of the tongue (fig. 37, ®), and extends from the base to the apex. It is thicker posteriorly than anteriorly, and is connected behind with the hyo-glossal membrane. To each side the transverse muscle is connected. Its disposition may be better seen subsequently on a vertical section. In 148 DISSECTION OF THE TONGUE. some instances a small fibro-cartilage, about a quarter of an inch deep and long, exists in the septum. The hyo- glossal membrane is a thin but strong fibrous lamina, which attaclies the root of the tongue to the upper border of the body of the hyoid bone. On its under or anterior surface some of the hinder fibres of the genio-hyo-glossi are inserted, as if this was their aponeuroses to attacli them to the os hyoides. The submucous fibrous or aponeurotic stratum of the tongue invests the organ, and is continued into the slieaths of the muscles. Ov^er the pos- terior third of the dorsum its strength is greater than elsewhere; and in front of the epiglottis it forms bands in the folds of the mucous membrane in that situation. Into it are inserted the muscular fibres which end on the surface of the tongue. Muscles. Each lialf of the tongue is made up of extrinsic and in- trinsic muscles. The former or external are distinguished by having only their termination in tlie tongue ; and the latter or internal, by having both origin and insertion within the origin — that is to say, springing from one part and ending in another. The extrinsic muscles (fig. 37) are the following : palato and stylo- glossus, hyo and genio-hyo-glossus, and pharyngeo-glossus. Only the lingual endings of these are now to be looked to. Dissection. After the tongue has been firmly fastened on its left side, the extrinsic muscles may be dissected on the right half. Three of these muscles, viz., palato-, d, stylo-, b, and hyo-glossus, c, come together to the side of the tongue, at the junction of the middle and posterior third ; and, to follow their radiating fibres forwards, it will be necessary to remove from the dorsum, between them and tlie tip, a thin layer consisting of the mu- cous membrane and fleshy fibres of the upper lingualis. Beneath the tip a junction between the stylo-glossus muscles of opposite sides is to be traced. The part of the constrictor muscle, g, which is attached to the tongue, and the ending of the genio-hyo-glossus, will come into view on the divi- sion of the hyo-glossus. Only the two parts of the hyo-glossus (basio- and cerato-glossus, p. 99), which arise from the body and great wing of the hyoid bone, are referred to above. To lay bare the third part, or the chondro-glossus, f, which is a small muscular sli[) attached to tlie small cornu of the os liyoides, turn upwards the dorsum of the tongue, and feel for the small cornu of the hyoid bone through the mucous membrane. Tlien remove the mucous membrane in front of the cornu, and the fibres of the muscle radiating forwards will be exposed. The palato and stylo-glossus muscles, d and b, are partly combined at tlieir attachment to the lateral part of the tongue, and form, together witli the following muscle, an expansion over the anterior two-thirds of the dorsum beneath the superficial lingualis. In this stratum tlie fibres radi- ate from the point of contact of the muscles with the tongue — some passing almost horizontally inwards to the middle, and others obliquely forwards to the tip of the organ. A great jiortion of the stylo-glossus is directed along the side of the tongue ; and some fibres are inclined to the under surface in front of the hyo-glossus, to join those of the ojiposite muscle beneath the tip. Byo-glossus. The two superficial parts of the muscle (basio and cerato- MUSCLES OF THE TONGUE. 149 Fig. 37. glossus, c, p. 99) enter the under surface of the tongue, between the stylo-glossus and the lingualis. After entering that surface by separate bundles, they are bent round the margin, and form, with the two preceding muscles, a stratum on the dorsum of the tongue. The third part of the muscle, or the chondro- gJossns^ f, is distinct from the rest. About two or three lines wide at its origin from the root of the small cornu, and from part of the body of the os hyoides, the muscle entering beneath the upper lingualis, passes obliquely inwards over tlie posterior third of the dorsum, to blend with the hyo glossus. Cortex of the tongue. The muscles above described, together with the superficial lingua- lis, constitute a cortical layer of oblique and longitudinal fibres, which covers the tongue, except below where some muscles are placed, and resembles “a slipper turned upside down.” This stratum is pierced by deeper fibres. The genio-hyo-glossus (fig. 38, enters the tongue vertically on the side of the septum, and perforates the cortical covering to end in the submucous tissue. In the tongue the fibres spread like the rays of a fan from apex to base, and are collected into bundles as they pass through the transversalis. The most pos- terior fibres end on the hyo-glossal membrane and the hyoid bone ; and a slip is prolonged from them, beneath the hyo-glossus, to the up- per constrictor of the pharynx. A vertical section at a future stage will show the radiation of its fibres. The pharyngeo-gJossus (glossoq)haryngeus), or the part of the upper constrictor attached to the side of the tongue, passes amongst fibres of the hyo- glossus, and is continued with the trans- verse muscle to the septum. The intrinsic muscles (fig. 38) are three in number in each half of the tongue, viz., transversalis, with a superior and an infe- rior lingualis. Dissection. To complete the prepara- tion of the inferior lingualis on the right side, the fibres of the stylo-glossus covering it in front, and those of the genio-hyo- glossus over it behind, are to be cut through. The superior lingualis (fig. 37, may be shown, on the left side, i)y taking the thin mucous membrane from tlie up{)er surface from tip to base. The transversalis (fig. 38, may be laid bare on the right side, by cutting away on the upper surface the stratum of the extrinsic muscles Muscles on the surface of THE Tonoue. A. Superficial liugualis. B. Stylo-glossus. c Hyo-glossus. D. Palato-glossus. F. Choudro-glossus. o. Pharyiigeo-glossus. H. Septum liuguje (Zaglas). Fig. 38. Intrinsic Muscles of the Tongue. A. Genio-hyo-glossus. B. Septum linguas. c. Transversalis. D. Inferior lingualis (Zaglas). 150 DISSECTION OF THE TONGUE. already seen ; and by removing on the lower surface, the inferior lingualis and the genio-hyo-glossus. The nerves of the tongue are to be dissected on the left half as well as the part will admit ; but a recent specimen would be required to follow them satisfactorily. The transL'ersaUs muscle (fig. 38, forms a horizontal layer in the substance of the tongue from base to apex. The fibres are attached in- ternally to the side of the septum, and are directed thence outwards, the posterior being somewhat curved, to their insertion into the side of the tongue. Its fibres are collected into vertical plates, so as to allow the passage between them of the ascending fibres of the genio-hyo-glossus. Action. By the contraction of the fibres of these muscles the tongue is made narrower and rounder, and is increased in length. Tlie superior lingualis (fig. 37, noto-glossus of Zaglas) is a very thin layer of oblique and longitudinal fibres close beneath the submucous tissue on the dorsum of the tongue. Its fibres arise from the frcenum epiglotti- dis, and from the fascia along the middle line ; from this attachment they are directed obliquely outwards, the anterior becoming longitudinal, to the margin of the tongue, at which they end in the fascia. Action. Both muscles tend to sliorten the tongue ; and they will bend the point back and up. The inferior lingualis (fig. 38, is much stronger than the preceding, and is placed under the tongue, between the hyo and genio-hyo-glossus. The muscle arises posteriorly from the fascia at the root of the tongue; and the fibres are collected into a roundish bundle: from its attached sur- face fascicidi are continued vertically through the transverse fibres up- wards to the dorsum; and at the anterior third of the tongue, where the muscle is overlaid by the stylo-glossus, some of tlie fibres are applied to that muscle and distributed with it. Action. Like the uj^per lingualis this muscle shortens the tongue, and bends the point down and back. The mucous membrane is a continuation of that lining the mouth, and is provided with a laminar epithelium. It partly invests the tongue, and is reflected off at different points in the form of folds (p. 146). At the epiglottis are three small glosso-epiglottid folds, connecting this body to the root of the tongue ; the central one of these is called the framum of the epiglottis. Like tlie membrane of the mouth, it is furnished with numerous glands, and some follicles. The follicles are depressions of the mucous membrane, which are sur- rounded by closed capsules in the submucous tissue, like the arrangement in the tonsil: they occupy the dorsum of the tongue between the papillne circumvallalaj and the epiglottis, where they form a stratum, close beneath the mucous membrane. The glands (lingual) are racemose or compound in structure, similar to those of the lips and cheek, and are placed beneath the mucous membrane on the dorsum of the tongue behind the papilUe vallatai. A few are found in front of the circumvallate papilla?, where they ])roject into the muscular substance. Some of their ducts open on the surface; others into the hol- lows around the large papilhe, or into the foramen ciecum and the depres- sions of the follicles. Op})osite the papilhe vallata?, at the margin of the tongue, is a small cluster of submucous glands. Under the tip of the tongue, on each side EXTERNAL LARYNGEAL MUSCLES. 151 of the fraennm, is another elongated collection of the same kind of glands imbedded in the muscular fibres, from which several ducts issue. Nerves. There are three nerves on the under part of each half of the tongue, viz., the gustatory, the hypoglossal, and the glosso-pharyngeal (fig. 23 ). Tlie gustatory nerve gives upwards filaments to the muscular substance, and to the two smallest sets of papillm, conical and fungiform; it joins also the hy[)Oglossal nerve. The hypoglossal nerve is spent in long slender offsets to the muscular substance of the tongue. The glosso-pharyngeal nerve divides under the hyo-glossus into two branches: — One turns to the dorsum, and ramifies in the mucous mem- brane behind tlie foramen cnecurn. The other passes beneath the side of the tongue, and ends in branches for the muscular substance; it supplies tlie papilhn circumvallatae, as well as the mucous membrane covering the lateral part of the tongue. Vessels. Tlie arteries are derived chiefly from the lingual of each side; these, together with the veins, have been examined (p. 101.) Section XVI. DISSECTION OF THE LARYNX. The larynx is the upper dilated part of the air tube, in which the voice is produced. It is constructed of several cartilages united together by ligamentous bands; of muscles for the movement of the cartilages; and of vessels and nerves. The whole is lined by mucous membrane. Dissection. The tongue may be removed from the larynx hy cutting through its root, but this is to be done without injuring the epiglottis. If the student learns the laryngeal cartilages before he begins the dis- section of the larynx, he will obtain more knowledge from the study of this Section. Occupying the middle line of the neck, the larynx is placed in front of the pharynx, and between the carotid vessels. It is pyramidal in form. The base is turned upwards, and is attached to the hyoid bone; and the apex is continuous with the trachea. In length it measures about one inch and a half ; in width at the top one inch and a quarter, and at the lower end one inch. The front is prominent along the middle line of the neck; and the pos- terior surface is covered by the mucous membnme of the pharynx. The larynx is very movable, and during deglutition is elevated and depressed by the different extrinsic muscles. Muscles. Commonly five pair and one single muscle are described in the larynx. Three are outside the cartilages, and three are more or less concealed by the thyroid cartilage. Directions. On one side of the larynx, say the right, the muscles may be dissected, and on the opposite side the nerves and vessels; and those superficial muscles are to be first learnt, which do not require the carti- lages to be cut. Dissection. The larynx being extended and fastened with ])ins, the dissector may clear away from tlie os hyoides and the thyroid cartilage the 152 DISSECTION OF THE LAEYNX. following extrinsic muscles, viz., constrictor, sterno-liyoicl, sterno-tliyroid, and thyro-liyoid. In front, between the thyroid and cricoid cartilages, one of the three small external muscles — crico-thyroid (tig. 39), will be recognized. The other two external muscles (fig. 40) are situate at the posterior aspect of the larynx ; to denude them it will be necessary to turn over the larynx, and to remove the mucous membrane covering it. On the back of the circoid cartilage the dissector will find the crico-aryta3noideus posti- cus muscle; and above it, on the posterior part of the arytcenoid cartilages, the arytasnoid muscle will appear. The CKico-TiiYROiDECS MUSCLE (fig. 39, is triangular in form, and is separated by an interval from the one on the opposite side. It arises from the front and the lateral part of the cricoid cartilage ; and its fibres Fig. 39. Fig. 40. Front View of the Larynx. 1. Crico-thyroid muscle 2. Thyroid cartilage. 3. Cricoid cartilage. Hinder View of the Larynx. A. Superficial part of the arytsenoideus muscle. B. Deep part of the arytseuoideus. c. Crico-arytieuoideus posticus. ascend to be inserted into the lower cornu, and the lower border of the thyroid cartilage as far forwards as a quarter of an inch from the middle line ; also, fora short distance (a line), into the inner surface of that carti- lage. The muscle rests on the crico-thyroid membrane, and is concealed by the sterno-thyroid muscle. Action. It approaches the thyroid to the cricoid cartilage, making longm’ the distance between the thyroid and the arytienoid cartilages, and tightens indirectly the vocal cords. The ciiico-ARYTiENOiDEus POSTICUS MUSCLE (fig. 40, ^) lics on the posterior part of the cricoid cartilage. Its origin is from the dejiression on the side of the vertical ridge at the back of that cartilage. From this origin the fibres are dii-ected outwards, and are inserted into a projection at the outer part of the base at the arytienoid cartilage. INTERNAL LARYNGEAL MUSCLES. 153 Action. It rotates the aryUienoid cartilage, turning out tlie lateral pro- jection at the base, and enlarges the interval between the cartilages. At the same time the upper orifice of the larynx is widened by the separation from each other of its lateral boundaries. Musculus kerato-cricoideus (Merkel). This is a small fleshy slip which is occasionally seen below and close to the preceding muscle ; it arises from the cricoid cartilage, and is inserted into the back part of the lower cornu of the thyroid cartilage. The ARYT^NOIDEUS is a single muscle in the middle line (fig. 40, ®), and is placed on the posterior surface of the arytoenoid cartilages : it pos- sesses two sets of fibres, superficial and deep, with different directions. Tlie deep fibres, b, are transverse, and are inserted into the outer border and the posterior surface of each cartilage ; they close the interval between the cartilages. The superficial fibres, a, consist of two oblique fasciculi, which cross like the parts of the letter X, each passing from the base of one cartilage to the a[)ex of the other : a few of these fibres are continued beyond the cartilage to join the thyro-arytinnoid muscle, and the depressor of the epiglottis. Action. The muscle causes the arytmnoid cartilages to glide towards one another, and diminishes much, or closes the rima glottidis. Acting with the depressors of the epiglottis it will assist in closing the upper orifice of the larynx. Dissection. The remaining muscles and the vocal apparatus would be learnt better on a fresli larynx, if this can be obtained. To bring into view the muscles, which are concealed by the thyroid cartilage (fig. 41) it will be necessary to remove tlie right half of the cartilage, by cutting through it a quarter of an inch from the middle line, after its lower cornu has been detached from the cricoid. By dividing next the crico-thyroid membrane attached to the lower edge, and the thyro-hyoid ligament con- nected with the upper margin, the loose piece will come away on separat- ing it from the subjacent areolar tissue. By the removal of some areolar tissue, the dissector will define inferiorly the crico-aryta3noid muscle ; above it, the thyro-arytmnoideus muscle ; and still higher, the thin muscular fibres (de^iressor of the epiglottis) in the fold of mucous membrane between the epiglottis and the arytamoid cartilage. On cleaning the fibres of the thyro-arytamoideus near the front of the larynx, the top of the sacculus laryngis with its small glands will appear above the fleshy-fibres. The CHICO aryta:noideus lateralis (fig. 41,^) is a small lengthened band, which arises from the ui)per border of the cricoid cartilage at the lateral part ; its fibres are directed backwards to be inserted into a projec- tion on the outer side of the base of the arytasnoid cartilage, and into the contiguous part of the outer surface. This muscle is concealed by the crico-thyroideus, and its upper border is contioruous to the succeedino; muscle. Action. Rotating the arytaenoid cartilage by moving inwards the pro- jection on the outer part of the base, it replaces the cartilage after tliis has been everted by the crico-arytmnoideus posticus. It may also approach the one vocal cord to the other, and so narrow the glottis. The THYRO-ARYTyENOiDEus MUSCLE (fig. 41) extends from the thyroid to the arytagnoid cartilage ; it is thick below, but thin and expanded above. The muscle arises from the thyroid cartilage near the middle line, for about the lower half of the depth, and from the crico-thyroid liga ment. The fibres are directed backwards with different inclinations : — The external, 154 DISSECTION OF THE LARYNX. Fig. 41. ascend somewhat, and are inserted in- to the upper part of the outer surface of tlie arytosnoid cartilage, and blend with the depressor of the epiglottis. The internal and lower fibres, are transverse, and form a thick bundle, which is inserted into the fore part of the base of that cartilage, and into the outer surface. By its outer surface the muscle is in contact with the thyroid cartilage ; and the inner surface rests on the vocal cords, and on the ventricle of the larynx and the pouch. Action. It moves forwards the ary- ta3noid cartilage towards the thyroid, and relaxes the vocal cord. By a thin band of fibres along the upper edge the rima glottidis can be narrowed, and the cord put into the vocalizing position. The DEPRESSOR OF THE EPIGLOT- TIS (fig. 41, (thyro-arytaeno-epiglot- tideus) is a thin muscular layer by the side of the up])er opening of the larynx. Its fibres arise posteriorly from the front of the arytsenoid cartilage, some being continuous below with fibres of the arytienoid and thyro-arytoenoid muscles ; and anteriorly by a narrow slip from the thyroid cartilage near the middle line. From those attachments . .. "'rn upwai'cls with very dit- 13. Crico arytajuoideus lateralis. fcreiit directions, and are inserted into h. Thyro-arytainoideus, superficial part. tlie border of the epiglottis Oil the Same U sldc. Tl^ streiigtli of the muscle va- ries much in different bodies. Some of the lower fibres of the muscle, which cover the top of the laryngeal pouch, have been described by Mr. Hilton as a separate muscle \yith the name arytceno-epiglottideiis inferior. Action. By the contraction of the fibres, the tip of the arytnenoid car- tilage will be moved forwards and inwards, and the eppiglottis will be lowered over tlie orifice of the larynx. The fibres of the muscle which are spread over the sacculus will compress it, and assist in the expulsion of the contents. Parts inside the larynx. The parts more immediately concerned in the production of the voice are, the vocal cords, the glottis, and the ventricle of the larynx and its pouch : these are placed within, and are protected by the laryngeal cartilages. Dissection. F or the ])urpose of disjilaying the vocal apparatus, let the tube of the larynx be divided along the posterior part, as in fig. 42 ; and in cutting through the arytamoid muscle, let the incision be rather to the right^f the middle line, so as to avoid the nerves entering it. On looking into the larynx a hollow (ventricle) will appear on each View of the Internal Muscles of the Larynx. 1. Crico-thyroideus detached. 2. Crico-aryta?uoideiis posticus. ^3. Crico arytajuoideus lateralis. Thyro-ary tainoideus, superficial part. Depressor of the epiglottis. •6. Thyro-hyoideus, cut- 8. Deep or transverse part of thyro-arytae- noideus. GLOTTIS AND LARYNGEAL POUCH. 155 side ; and bounding the ventricle above and below are the whitisli bands of the vocal cords. If a probe be passed into that hollow, it will enter a small pouch (sac- culus laryngis) by an aperture in the anterior and upper part. The dis- sector should fill tlie sacculus on the left side by introducing a small piece of cotton wool into it. The laryngeal space reaches from the epiglottis to the lower border of the cricoid cartilage. It opens above into the pharynx, and below into the trachea ; and in the intermediate portion are lodged the parts pro- ducing voice. The upper orifice of the larynx (fig. 29, will be evident on placing in contact the cut surfaces. It is triangular in shape, with the base in front and the apex behind, and its sides are sloped obliquely downwards in the antero-posterior direction. Its boundaries are, — the epiglottis in front, the aryta3noid muscle and cartilages behind, and the arytyeno-epiglottidean fold of mucous membrane on each side. This aperture is closed by the epiglottis during deglutition. The lower opening^ limited by the inferior edge of the cricoid cartilage, is circular in form, and is of the same size as that cartilage. The laryngeal cavity is much reduced in size within the thyroid car- tilage by the vocal cords, and is dilated above and below them for the pur- pose of allowing their free vibration. The lower dilatation may be seen to be as large as the ring of the cricoid ; and the upper, much smaller, corresponds with the ventricle of the larynx. Above the upper bulge the wall of the larynx slants up to the epiglottis. The glottis or rinia glottidisy is the interval between the lower vocal cords (tig. 44) ; it is placed on a level with the base of the aryta^noid car- tilages, and is the narrovvest part of the laryngeal cavity. Its sides are constructed partly of ligament and partly of cartilage : — thus, for about the two anterior thirds is the elastic vocal cord (tig. 42, ®), whilst at the posterior third is the smooth inner surface of the arytcunoid cartilage, e. Behind it is bounded by the arytainoid muscle ; and in front by the thyroid cartilage and the attachments of the vocal cords. The size of the interval differs in the two sexes. In the male it mea- sures from before back nearly an inch (less a line), and across at the base, when dilated, about a third of the other measurement. In the female the dimensions will be less by two or three lines. Alterations in the size and form affect the interval where it is bounded by the cartilages, as well as where it is limited by the ligaments. In the former part, the changes are occasioned by the movements of the aryta?- noid cartilages ; but in the latter they are due to the lengthening and shortening of tlie bands. In the state of rest it is a narrow fissure which is enlarged a little behind and rounded ; but when dilated it is triangular in form, like the upper orifice, though its wider part is turned backwards to the arytasnoid muscle. In the living body the fissure is larger in inspiration than in ex[)iration. The mus- cles too are constantly producing alterations in the fissure, some acting more immediately on the cartilages as dilators and contractors of the base; and others altering the state of the ligaments, by elongating and shortening the sides. The base is enlarged, and the interval rendered triangular by the poste- rior crico-arytaenoid ; and is diminished by the aryta3noid, and the lateral crico-arytasnoid. And the ligamentous sides are elongated and made tense by the crico-thyroidei, but are shortened by the thyro-aryta3noidei. 156 DISSECTION OF THE LARYNX. The ventricle of the larynx (fig. 42, is best seen on the left side. It is the oval hollow between the vocal cords, whose upper margin is semi- lunar, and the lower straight. It is lined by the mucous membrane, and on the outer surface are the fibres of the thyro-arytasnoid muscle. In the anterior part is the aperture into the laryngeal pouch. Tlie laryngeal poncJi (sacculus laryngis) (fig. 42, has been laid bare in part on the right side by tlie removal of the half of the thyroid cartilage (p. 153), but it will be seen again in the subsequent dissection for the vocal cords. It is a small membranous sac, half an inch deep and cylindrical in form, which projects upwards between the upper vocal cord and the thyroid slip of the depressor of the epiglottis. Fig. 42. and reaches sometimes as high as the upper border of the thyroid cartilage. Its cavity communicates with the front of the ventricle by a somewhat narrow aperture. On the outer sur- face are numerous small glands, whose ducts are transmitted through the coats of the sac to the inside. Numerous nerves are distributed over the top. Its upper part is covered by the muscular slij) before referred to. Dissection. The general sliape and position of the vocal cords are evi- dent on the left half of the laryngeal tube, but to show more fully the na- ture of the lower cord, put the cut surfaces in contact, and detach on the right side the crico-arytienoideus lat- eralis from its cartilages. Remove in like manner the thyro-arytsenoi- deus, raising it from before back. By the removal of the last muscle, a fibrous membrane, crico-thyroid (fig. 44, ®), comes into view, and its up- per free edge will be perceived to constitute the inferior or true vocal cord. "Whilst taking away the thyro- arytenoideus, the ventricle and the sacculus laryngis, which are formed chiefly by mucous membrane, will disappear. The vocal cords or the thyro-ary- tcenoid ligaments (fig. 42), are two bands on each side, whicli are ex- tended from the angle of the thyroid to the arytmnoid cartilage — one 1‘orm- ing the upper, the other the lower margin of the ventricle. The upper ligament (false vocal cord (fig. 42, ^) is semilunar in form, and is much weaker than the other. It is fixed in front to the angle of the thyroid cartilage, near the attachment of the epiglottis ; and behind to Vocal Apparatus, on a Vertical Section OF THE Larynx. A. Ventricle of the lai’ynx. - B. True vocal cord, c. False vocal cord. D. Sacculus laryngis. E Arytainoid cartilage. F. Cricoid cartilage. G. Thyroid cartilage. H. Epiglottis. K. Crico-thyroid ligament. L. Thyro-hyoid ligament. GLOTTIS AND LARYNGEAL POUCH. 157 tlie outer surface of the arjtaenoid cartilage. Tliis ligament consists chiefly of white fibrous tissue, which is continuous with that in the arytaiiio-epi- glottidean fold of mucous membrane. The inferior ligament (chorda vocalis, fig. 42, ®) is attached in front to the angle of the thyroid cartilage, about half-way down below the not(?h ; the ligament is directed backwards, and is inserted into the anterior promi- nence at the base of the arytmnoid cartilage. It is about seven lines long in man, and two less in the woman. Internally this band is covered by thin mucous membrane, and projects towards its fellow into the cavity of the larynx, the interval between it and the opposite one being the glottis. Externally it is connected with the thyro-arytajnoid muscle And inte- riorly it is continuous with the crico-thyroid ligament, k. The edge that bounds the v'entricle is straight and well defined, and vibrates to produce sounds. The ligament is composed of tine elastic tissue. The mucous membrane of the larynx is continued from that investing the pharynx, and is prolonged to the lungs through the trachea. AVhen entering the larynx it is stretched between the epiglottis and the tip of the arytenoid cartilage, forming the arytmno-epiglottid fold on each side of the laryngeal orifice: at this S{)Ot it is very loose, and the submucous tissue abundant. In the larynx the membrane lines closely the cavity, sinks into the ventricle, and is prolonged into the laryngeal pouch. On the thyro-arytenoid ligaments it is very thin and adherent, allowing these to be visible through it. In the small part of the larynx above tlie vocal cords, the epithelium is of the laminar kind, and free from cilia. But a columnar ciliated epithe- lium covers the surface below the level of the superior cords, though it becomes flattened without cilia on the cords : on the epiglottis it is ciliated in the lower half. Numerous branched glands are connected wdth the mucous membrane of the larynx, and the orifices will be seen on the surface, especially at the posterior aspect of the epiglottis. In the edge of the aryta:no-epiglot- tidean fold there is a little swelling occasioned by a mass of subjacent glands (arytcenoid) ; and along the upper vocal cord lies another set. None exist over the vocal cords, but close to those bands is the collection of the sacculus laryngis, which lubricates the ventricle and the lower vocal cord. Dissection of nerves and vessels. The termination of the laryngeal nerves may be dissected on the untouched side of the larynx. For this purpose the other half of the thyroid is to be disarticulated from the cri- coid cartilage, care being taken of the recurrent nerve, which lies near the joint between the two. The trachea and larynx sliould be fastened down next with pins; and after the thyroid has been drawn away from the cricoid cartilage, the inferior laryngeal nerve can be traced over the side of the latter cartilage to the muscles of the larynx, and mucous mem- brane of the pharynx. Afterwards the superior laryngeal is to be found as it pierces the thyro- hyoid membrane, and branches of it are to be followed to the mucous membrane of the larynx and pharynx. Two communications are to be looked for between the laryngeal nerves ; one is beneath the thyroid car- tilage, the other in the mucous membrane of the pharynx. An artery accompanies each nerve, and its offsets are to be dissected at the same time as the nerve. 158 DISSECTION OF THE LARYNX. Nerves. The nerves of the larynx are the superior and inferior laryn- geal brandies of the pneumo-gastric (p. 113) ; the former is distributed to the mucous membrane, and the latter chiefly to the muscles. The inferior laryngeal nerve (recurrent), when about to enter the larynx, furnishes backwards an offset to the mucous membrane of the pharynx ; this joins filaments of the upper laryngeal. The nerve then passes beneath the ala of the thyroid cartilage, and ends in branches for all the special muscles of the larynx except the crico-thyroideus. Its small muscular branches are superficial, but that to the arytoenoid muscle passes beneath the crico-arytasnoideus posticus. Beneath the thyroid car- tilage the inferior is joined by a long offset of the upper laryngeal nerve. The superior laryngeal nerve pierces the thyro-hyoid ligament, and gives offsets to the mucous membrane of the pharynx ; it furnishes also a long branch beneath the ala of the thyroid cartilage to communicate with the recurrent nerve. The trunk then terminates in many branches for the supply of the mucous membrane : — Some of these ascend in the arytgeno- epiglottid fold to the epiglottis, and the root of the tongue. The others, which are the largest, descend on the inner side of the ventricular pouch, and sup[)ly the lining membrane of the larynx as low as the vocal cords. One nerve of this set pierces the arytjenoid muscle, and ends in the mucous membrane. Vessels. The arteries of the larynx are furnished from the superior and in erior thyroid branches (p. 85 and 78). The laryngeal branch of the superior thyroid artery enters the larynx with the superior laryngeal nerve, and divides into ascending and descend- ing branches ; some of these enter the muscles, but the rest su})ply the epiglottis, and the mucous membrane from the root of the tongue to the chorda vocalis. Like the nerves, it unites with the following artery both beneath the ala of the thyroid cartilage, and in the mucous membrane of the |)harynx. The laryngeal branch of the inferior thyroid artery ascends on the back of the cricoid cartilage, and ends in the mucous membrane of the pharynx and the ])OSte]‘ior muscles of the larynx. Some other twigs from the su[)erior thyroid artery perforate the crico- thyroid membrane, and ramify in the mucous lining of the interior of the larynx at the lower part. Laryngeal veins. The vein accompanying the branch of the superior thyroid artery, joins the internal jugular or the superior tliyroid vein ; and the vein with the artery from the inferior thyroid opens into the plexus of the inferior thyroid veins (p. 85 and 78). Section XVII. HYOID BONE, CARTILAGES AND LIGAMENTS OF THE LARYNX, AND STRUCTURE OF THE TRACHEA. Dissection. All the muscles and the mucous membrane are to be taken away so as to denude the hyoid bone, the cartilages of the larynx, and the epiglottis ; but the piece of membrane that joins the hyoid bone CARTILAGES OF LARYNX. 159 to the thyroid cartilage, and the ligaments uniting one cartilage to another on the left side, should not be destroyed. In the arytteno-epiglottidean fold of mucous membrane, a small carti- laginous body (cuneiform) may be recognized ; an oblique whitish pro- jection indicates its position. The hyoid bone (os hyoides) (fig. 43) ’s situate between the larynx and the root of the tongue. Resembling the letter U, placed horizontally and with the legs turned backwards, it offers for examination a central part or body, and two lateral pieces or cornua on each side. The body, c, is thin and flattened, and measures most in the transverse direction. Convex in front, where it is marked by a tubercle, it presents an uneven surface for the attachment of muscles; whilst on the opj)Osite aspect it is concave. To the upper border the fibrous membrane (hyo- glossal) fixing the tongue is attached. The cornua are two in number on each side (large and small). The large cornu, ii, continues the bone backwards, and is joined to the body by an intervening piece of cartilage. The surfaces of this cornu look somewhat upwards and downwards ; and the size decreases from before backwards. It ends posteriorly in a tubercle. The small cornu, or ap- pendix, j, is dissected upwards from the point of union of the great cornu with the body, and is joined by the stylo-hyoid ligament: it is seldom wholly ossified. Cartilages of the Larynx (fig. 43). There are four large carti- lages in the larynx, which are concerned in the production of the voice, viz., the thyroid, the cricoid, and the two arytienoid. In addition there are some yellow fibro-cartilaginous structures, viz., the epiglottis, a capitu- lum to each arytasnoid cartilage, and a small ovalish piece (cuneiform) in each arytieno-epiglottidean fold of mucous membrane. The thyroid cartilage^ B, is the largest of all : it forms the front of the larynx, and protects the vocal apparatus as with a shield. The upper part of the cartilage is considerably wider than the lower, and in conse- quence of this form the larynx is somewhat funnel-shaped. The anterior surface is prominent in the middle line, forming the subcutaneous swelling named pomum Adami ; but the cartilage is concave behind at the same spot, and gives attachment to the epiglottis and the thyro-arytcenoid mus- cles and ligaments. The upper border is notched in the centre. The cartilage consists of two square halves, which are united in the middle line. Posteriorly each half of the cartilage has a thick border, which terminates U))wards and downwards in a rounded process or cornu (e and f). Both cornua are bent slightly inwards: of the two, the upper, E, is the longest ; but the lower one, f, is thicker than the otlier, and articulates with the cricoid cartilage. The inner surface of each half is smooth ; but the outer is marked by an oblique line for the attachment of muscles, which extends from a tubercle near the root of the upper cornu, almost to the middle of the lower border. The cricoid cartilage^ d, is stronger though smaller than the thyroid, and encircles the cavity of the larynx ; it is partly concealed by the shield- like cartilage, below which it is placed. It is very unequal in depth be- fore and behind, — the posterior part being three times deeper than the anterior, something like a signet ring. Its hollow is about as large as the fore finger. The outer surface is rough, and gives attachment to muscles. At the back of the cartilage there is a fiat and rather square portion, which is 160 DISSECTION OF THE LARYNX. Fiff. 43. marked by a median ridge between two contiguous muscular depressions. On each side, immediately in front of the square part, is a shallow articu- lar mark, which receives the lower cornu of the thyroid cartilage. The inner surface is smooth, and is covered by mucous membrane. The lower border is undulating, and is united to the trachea by fibrous membrane. Tlie upper border is nearly straight posteriorly, opposite the deep part of the ring ; and this portion is limited on each side by an articular mark for the arytcenoid cartilage. In front of that spot the border is sloped obliquely downwards to the middle line. At the middle line behind there is a slight excavation in each border. The two arytceiioid cartilages, C, are placed one on each side at the back of the larynx, on the upper border of the cricoid cartilage. Each is pyramidal in shape, is about half an inch in depth, and offers for examination a base and apex, and three surfaces. The base has a slightly hollow'ed sur- face behind for articulation with the cricoid cartilage, and is elongated in front into a process which gives attach- ment to the vocal cord. The apex is directed backwards and somewhat in- wards, and is surmounted by the carti- lage of Santorini. The inner surface is narrow, especially above, and flat. The outer is wide and irregular, and on it is a small projection at the base, which receives the insertion of some of the muscles. At the pos- terior aspect the cartihige is concave and smooth. Cartilages of Santorini. Attached to the apex of each arytaenoid cartilage is the small, conical fibro-cartilage of Santorini (corniculum capitulum), which is bent inwards towards the one of the opposite side. The arytieno-epiglottidean fold is connected wdth it. Cuneiform cartilages. Two other small fibro-cartilaginous bodies, one on each side, which are contained in the arytfeno-epiglottid folds, have received this name. Eacli is somewhat elongated and rounded in form, like a grain of rice; it is situate obliquely in front of the capitulum of the aryta 3 noid cartilage, and its place in the fold of the mucous membrane is marked by a slight whitish projection. The epiglottis (fig. 43, is single, and is the largest of the pieces of yellow fibro-cartilage. In form it is cordate, and it resembles a leaf, with the stalk below and tlie lamina or expanded part above. Its position is beliind the tongue, and in front of the orifice of the larynx. During Hyoid Bone and the Laryngeal Cartilages. G. Body of the hyoid hone. H. Large cornu, j. Small cornu. A. Epiglottis. B. Thyroid cartilage, c. Arytainoid cartilage. D. Cricoid cartilage. E. Upper cornu, and F. Lower cornu of the thyroid carti- lage. LIGAMENTS OF LARYNX. 161 Fiff. 44. respiration it is placed vertically, but during deglutition it takes a hori- zontal direction so as to close the opening of the larynx. The anterior surface is bent forwards to the tongue, to which it is con- nected by three folds of mucous membrane; and the posterior surface, hollowed laterally, is convex from above down. To its sides the arytaeno- epiglottid folds of mucous membrane are united. After the mucous mem- brane has been removed from the epiglottis its substance will be seen to be perforated by numerous spaces, which lodge mucous glands. Between the epiglottis and the hyoid bone is a mass of yellowish fat with some glands; this has been sometimes called the epiglottidean gland. Ligaments of the Larynx. Tlie larynx is connected by extrinsic ligaments with the hyoid bone above and the trachea below. Other liga- ments join together the cartilages, forming joints in some cases. Union of the larynx with the hyoid bone and the trachea. A thin loose elastic membrane (thyro-hyoid) passes from the thyroid cartilage to the hyoid bone; and a second membrane connects the cricoid cartilage with the trachea. The thyro-hyoid ligament (fig. 4*2, l) is at- tached on the one part to the upper border of the thyroid cartilage; and on the other, to the upper border of the hyoid bone, at the posterior aspect. Of some thickness in the centre, it gradually be- comes thinner towards the sides; and it ends laterally in a rounded elastic cord, which inter- venes between the extremity of the hyoid bone and the upper coi'iiu of the thyroid cartilage. The superior laryngeal nerve and vessels per- forate the ligament, and a synovial membrane is placed between it and the posterior surface of the hyoid bone. In the elastic lateral part of the ligament will be found occasionally a small ossific nodule (cartilago triticea). The membrane joining the lower border of the cricoid cartilage to the first ring of the trachea — crico -tracheal ligament., resembles the band joining the rings of the trachea to each other. Union of the cricoid a7id thyroid cartilages. These cartilages are joined in the middle line in front by ligament; and on the side, by a joint with the small cornu of the thyroid cartilage. The crico-thyroid ligament or membrane (fig. 44, closes the space between the thyroid, cri- coid, and arytaenoid cartilages, and the right half is now visible. It is yellow in color, and is formed mostly of elastic tissue. At the centre it is thick and strong, but is thinner on each side as it is continued backwards. By the lower bor- der it is fixed to the upper edge of the cricoid as far back on each side as the joint with the arytasnoid cartilage. Its upper border, free and rounded, is covered by mucous membrane, and forms the lower vocal cord. In front it is united to the thyroid cartilage; and be- hind to the base of the arytsenoid. 11 View of the Vocal Cords AND Crico-thyroid Lioa- MENTS. 1. True vocal cord. 2. Post, crico-arytsea muscle. 3. Cricoid cartilage. 4. Arytsenoid cartilage. •5. Sacculus laryngis. 6. Crico-thyroid membrane. 162 DISSECTION OF THE LARYNX. The ligament is partly concealed by the crico-thyroid muscle, and some small apertures exist in it for the passage of fine arteries into the larynx. The strong forepart of the ligament serves the purpose of uniting the two large laryngeal cartilages; and the lateral piece, closing the larynx, ends above in the vocal cord. A capsular ligament surrounds the articular surfaces between the side of the cricoid and the lower cornu of the thyroid cartilage. Its fibres are strongest beliind. A synovial membrane lines the capsule. This joint admits forward and backward movements of the thyroid car- tilage, by which the condition of the vocal cords is altered. If that carti- lage is moved forwards the cords are stretched, and if backwards the cords are relaxed. Articulation of the cricoid and arytcenoid cartilages. The articular surfaces of the cartilages are retained by a loose capsule, and possess a synovial sac. The capsular ligament is fixed to each cartilage around its articular surface ; and one part — posterior ligament., is strongest on the inner and posterior aspects. A loose synovial membrane is present in the articu- lation. The arytienoid cartilage glides freely forwards and backwards, inwards and outwards; but if its horizontal movements are controlled by muscular action, it can be rotated around a vertical axis, the anterior spur being moved inwards and outwards. Obviously the state of the vocal cords will be changed by the movements of the cartilages. When the arytaenoids glide in and out the cords will be approximated and separated; when backwards and forwards, the cords will be tightened and relaxed; and in rotation the cords will be moved away from, and brought towards each other. A kind of capsule, formed of thin scattered fibres, with a synovial sac, unites the apex of the arytjenoid cartilage with the hollowed base of the capitulum of Santorini. Sometimes these cartilages are blended together. Fibrous bands (thyro-arytaenoid) join the thyroid with the arytcenoid cartilages, and have been examined as the vocal cords (p. 156). Ligaments of the epiglottis. A band, thyro-epiglottidean, connects the lower part of the epiglottis to the thyroid cartilage, close to the excavation in the upper border of the latter (fig. 42). Some fibrous and elastic tis- sues — hyo-epiglottid ligament, connect likewise the front of the epiglottis to the hyoid bone. Structure of the Trachea. The air tube consists of a series of pieces of cartilage (segments of rings) (fig. 40), which are connected together by fibrous tissue. The interval between the cartilages at the back of the tube is closed by fibrous membrane, and by muscular fibres and mucous glands. The trachea is lined by mucous membrane with subja- cent elastic tissue. Cartilages. The pieces of cartilage vary in number from sixteen to twenty. Each forms an incom})lete ring, which extends about three- fourths of a circle ; and each is convex forwards, forming the front and sides of the air tube. Both above and below, the cartilaginous pieces are less constant in size and lorm : for tov ards the larynx they increase in depth, whilst in the 0 })posite direction they may be slit at their ends or blended together ; and the lowest piece of cartilage is shaped like the letter V. A fibrous tissue is continued from one to another on both aspects, though LONGUS COLLI xMUSCLE. 163 in greatest quantity externally, so as to incase and unite them ; and it is extended across the posterior part of the air tube. Dissection. On removing for about two inches the fibrous membrane and the mucous glands from the interval between the cartilages at the back of the trachea, the muscular fibres will appear. After the muscular fibres have been examined the membranous part of the tube may be slit down, to see the elastic tissue and the mucous mem- brane. Muscular fibres. Between the ends of the cartilages is a continuous layer of transverse bundles of unstriated muscle, which is attached to the truncated ends and the inner surface of the cartilages. By the one sur- face the fleshy fibres are in contact with the membrane and glands, and by the other with the elastic tissue. Some longitudinal fibres are super- ficial to the transverse ; they are arranged in scattered bundles, and are attached to the fibrous tissue. The elastic tissue forms a complete lining to the tracheal tube beneath the mucous membrane ; and at the posterior part, where the cartilages are deficient, it is gathered into strong longitudinal folds. This layer is closely connected with the mucous membrane covering it. The mucous membrane of the trachea lines the tube, and resembles that of the larynx in being furnished with a columnar ciliated epithelium. Connected with this membrane are numerous branched mucous glands of variable size. The largest are found at the back of the trachea, in the interval between the cartilages, where some are placed beneath the fibrous membrane with the muscular fibres, and others outside that layer. Other smaller glands occupy the front and sides of the trachea, being situate on and in the fibrous tissue connecting the cartilaginous rings. Section XVIII. PREVERTEBRAL MUSCLES AND VERTEBRAL VESSELS. Directions. On the part of the spinal column that was laid aside after the separation of the pharynx from it, the student is to learn the deep muscles on the front of the vertebrae. Dissection. The prevertebral muscles will be prepared by removing the fascia and areolar tissue. The muscles are three in number on each side (fig. 45), and are easily distinguished. Nearest the middle line lies the longus colli — this is the longest ; the muscle external to it, which reaches to the head, is the rectus capitis anticus major ; and the small muscle close to the skull, which is external to the last and partly concealed by it, is the rectus capitis anticus minor. The smaller rectus muscle is often injured in cutting through the basilar process of the occipital bone. The LONGUS COLLI MUSCLE (fig. 45, is situate on the bodies of the cervical and upper dorsal vertebrae, and is pointed above, but larger below. It consists of two parts — internal and external, the former being vertical, and the latter oblique in direction, as on the right side of the figure. The internal part arises by fleshy and tendinous processes from the bodies of the two upper dorsal and two lower cervical vertebrae ; and the external piece takes origin from the anterior transverse processes of four 164 DISSECTION OF THE NECK. cervical vertebra3 (sixth, fifth, fourth, and third) Both parts of the mus- cle are blended above, and the whole is insertedhj four slips into the bodies of the four upper cervical vertebrae. Some of tlie lowest fibres of the muscle are attached separately by ten- don to the anterior transverse process of one or two of the lower cervical vertebrae. Fig. 45. A. Longus medius. B. Rectus capitis anticus major, c. Scalenus anticus. D. Scalenus medius. F. Scalenus posticus. G. Rectus capitis anticus minor. Deep Muscles of the Front of the Neck and the Scaleni Muscles. In contact with the anterior surface of the muscle is the pharynx. The inner border is at some distance interiorly from the muscle of the opposite side, but superiorly only the pointed anterior common ligament of the ver- tebras separates the tvvo. The outer border is contiguous to the scalenus, to the vertebral vessels, and to the rectus capitis anticus major muscle. Action. Both muscles bend forwards the neck; and the upper oblique fibres of one will turn the neck and head to the same side, by the attach- ment to the atlas. The RECTUS CAPITIS ANTICUS MAJOR (fig. 45, ®) is external to the preceding muscle, and is largest at the upper end. Its origin is by pointed tendinous slips, with the longus colli, from the summits of the anterior transverse processes of four cervical vertebrag (sixth, fifth, fourth, and third) ; and the fibres ascend to be inserted into the basilar process of the occipital bone, in front of the foramen magnum. Tlie anterior surface of tlie muscle is covered by the pharynx, and by the carotid artery and tlie numerous nerves near the base of tlie skull. The muscle partly conceals the following one. At its insertion the rectus is fleshy, and reaches from the middle line to the temporal bone. Action. Both muscles incline forwards the head ; and one will bring the face to the same side by rotating the head. INTERTRANSVERSE MUSCLES. 165 The RECTUS CAPITIS ANTicus MINOR (fig. 45, ®), is a small flat muscle, which arises from the anterior transverse process and body of the atlas ; and is inserted into the basilar process of the occipital bone between the foramen magnum and the rectus major, and half an inch from its fellow. The anterior primary branch of the suboccipital nerve lies between the borders of this muscle and the rectus capitis lateralis. Action. Its power is very slight, but it will help in moving forwards the head. Dissection. The small intertransversales muscles will come into view when the other muscles have been removed from the front and back of the transverse processes. By tracing towards the spine the anterior primary branches of the cervical nerves, the intertransversales will be readily seen on their sides. After the muscles and nerves have been examined, the tips of the conjoined transverse processes may be cut off to lay bare the vertebral artery. The INTERTRANSVERSE MUSCLES are sleuder fleshy slips in the inter- vals between the transverse processes. In the neck there are seven pairs — the first being between the atlas and axis, and the last between the lowest cervical and the first dorsal vertebra. One set is attached to the anterior, and the other to the posterior tubercles on the tips of the con- joined transverse processes. Between the muscles, except in the first two spaces, is the anterior pri- mary branch of a cervical nerve ; and beneath the posterior muscle is the other primary branch of the same nerve. In the up})er space the posterior muscle is often wanting; and in the lowest space, the muscle of the ante- rior set is smaller than the others, or it may be absent. Action. By approximating the transverse processes these muscles bend the spinal column laterally. Cervical nerves at their exit from the spinal canal. The trunks of the cervical nerves issue from the spinal canal through the intervertebral foramina, except the first two, and bifurcate into anterior and posterior branches. The anterior primary branch passes outwards between the intertrans- verse muscles, and joins in plexuses with its fellows. The posterior primary branch turns to the Back beneath the posterior intertransverse muscle, and the other muscles attached to the [posterior transverse processes; in its course it lies close to the bone between the articular processes of the vertebra. Peculiarities in the first two. The first two nerves leave the spinal canal above the neural arches of the atlas and axis, and divide at the back of the neck into anterior and posterior branches. The anterior primary branch of the first or suboccipital nerve has been examined (p. 115). The anterior branch of the second nerve, after per- forating the membrane between the neural arches of the first and second vertebrae, is directed forwards outside the vertebral artery, and beneath the first pair of intertransverse muscles, to join the cervical plexus. The posterior primary branches of the first two nerves are described in the dissection of the Back. The vertebral artery has been seen at its origin in the neck (p. 77) ; and its termination is described with the vessels of the brain. Entering usually the foramen in the sixth cervical vertebra, the artery ascends ver- 166 DISSECTION OF THE NECK. tically through the corresponding foramina in the other vertebrae. Beyond the atlas, the vessel turns backAvards on the neural arch of that bone, and passing beneath the ligament joining the first vertebra with the os occipi- tis, enters the skull through the foramen magnum. In its course through the foramina the artery lies in front of the anterior trunks of the cervical nerves, except those of the first and second — the former of which crosses on the inner, and the latter on the outer side. The vessel is accompanied by a vein, and by a plexus of nerves of the same name. In the neck the artery furnishes small twigs to the surrounding muscles, the spinal canal, and the spinal cord. The vertebral vein begins by small radicles in the occiput, and in the muscles of the back of the neck, and enters the aperture of the atlas, where it receives sometimes a vein from the skull through the posterior condyloid foramen of the occi})ital bone. Accompanying the artery, the vein tra- verses the apertures between the transverse processes, and ends in the subclavian vein. In its course it is joined by branches from the internal and external spinal veins; its other branches are described at p. 78. The vertebral plexus of nerves is derived from the inferior cervical ganglion of the sympathetic (p. 117). It surrounds the artery, and com- municates with the spinal nerves as high as the third or fourth. Section XIX. LIGAMENTS OF THE VERTEBRAE AND CLAVICLE. Directions. On the remaining part of the spine, the ligaments connect- ing the cervical vertebraB to each other and to the occipital bone are to be learnt. Dissection. Disarticulate the last cervical from the first dorsal verte- bra. Then remove altogether the muscles, vessels, nerves, and areolar tissue and fat from the cervical vertebrae. By sawing through the occipi- tal bone, so as to leave only an osseous ring behind the foramen magnum, the ligaments between the atlas and the occipital bone can be more easily cleaned. The COMMON LIGAMENTS attaching together the cervical vertebrae are similar to those uniting the vertebrae in other parts of the spine, viz., an anterior and a posterior common ligament; bands between the laminae and spines; capsular ligaments and synovial membranes for the articulating })rocesses ; and an intervertebral ligament between the bodies of the bones. Directions. The common ligaments will be best seen on the dorsal or lumbar portions of the spine where they are more fully developed ; their ])reparation and description will be found at the end of the thorax, Avith the description of the ligaments of the spine. Should the student examine them in the neck, to see their difference in this region of the spine, he should leave uncut the neural arches of the three highest cervical vertebra?, to which special ligaments are attached. Special ligaments unite the first tAvo cervical vertebrae to each other jind to the occi))ital bone: some of these are external to, and others Avithin the spinal canal. LIGAMENTS OF ATLAS AND AXIS. 167 The ligaments outside the spinal canal are thin fibrous membranes, which connect the bodies and arches of the first two vertebrae in front and behind ; and join the atlas with the occipital bone at the same aspects. Fig. 46. External Ligaments in front between the Atlas and Axis and the Occipital Bone (Bourgery). 1. Sawn basilar process. 3, Anterior atlo-axoid. 2. Anterior occipito-atloid. 4. Articulation of the articular processes cut open. Capsular ligaments surround the articular surfaces of all the bones; but these will be examined more conveniently after the spinal canal has been opened. Union of the atlas with the axis. The posterior ligament (atlo-axoid) (fig. 47, ■*) is a thin loose membrane, which is attached by one margin to the neural arch of the atlas, and by the other to the corresponding arch of the axis. Below the superficial part are some deeper and stronger fibres. Tlie posterior primary branch of the second nerve pierces it. Fig. 47. External Ligaments behind between the Atlas and Axis and the Occipital Bone. 1. Posterior occipito-atloid ligament. 3. Vertebral artery entering beneath the oc- 2. Posterior atlo-axoid. cipito-atloid ligament. The anterior ligament (fig. 46, unites the bodies of the first two ver- tebrte in the same manner as the preceding ligament connects their arches. It is thickest in the middle. 168 DISSECTION OF THE NECK. Union of the atlas with the occipital hone. The anterior ligament (oc- cipito-atloid) (fig. 46, '^) is thin and wide, and passes from the basilar process of the occipital bone, in front of the foramen magnum, to the body of the atlas. The middle part of the ligament, which is fixed to the tubercle on the front of the atlas, is much the thickest. The posterior ligament (fig. 47, is fixed to the occipital bone behind the foramen magnum, and to the neural arch of the atlas. It is thin; and at its attachment to the atlas the vertebral artery (^), and the posterior primary branch of the suboccipital nerve, pass beneath it. The ligaments inside the spinal canal are peculiar in form, and assist in retaining the skull in place during the rotatory and nodding movements of the head. Between the occipital bone and the second vertebra are Fig. 48. Internal Ligament between Occipital Bonk and Axis (Bourgery). 1 and 2. Attachments of the occipito-axoidean ligament. three strong ligaments — a central, and two lateral or check ; and the odon- toid process of the axis is fixed against the body of the atlas by a strong transverse band.' Dissection. Supposing the neural arches of the cervical vertebrte to be removed except in the first three, the arches of these vertebrae are to be sawn through close to the articular processes. Nextly the ring of the occipital bone bounding posteriorly the foramen magnum is to be taken away. Lastly, the student should detach the tube of dura mater from the interior of the spinal canal; and, on raising from below the upper part of the posterior common ligament of the bodies of the vertebrae, the liga- mentous band between the occipital bone and the axis (occipito-axoid) will come into view. Union of the occipital hone with the axis. The central ligament (oc- cipito-axoidean) (fig. 48, is a strong, thick layer beneatli the posterior common ligament of the bodies of the vertebrae, and is rather triangular in form with the base upjiermost. Above it is attached to the basilar process (on the cranial aspect) near the margin of tlie foramen magnum, extending as far on each side as the insertion of the clieck ligaments. From that spot it descends over the odontoid process, and, becoming nar- rower, is inserted into tlie body of the axis. Occasionally a bursa is found between it and the transverse ligament of the atlas. LIGAMENTS OF ATLAS AND AXIS. 169 Dissection (fig. 49). After the removal of the occipito-axoidean liga- ment, by cutting transversely through it above, and reflecting it, the stu- dent should define a strong band, the transverse ligament which crosses Fig. 49, Intrrnal Ligaments between the Occipital Bone and the Atlas and Axis (Bourgery). 1. The left cheek ligament. 3. Cut end of the occipito-axoidean ligament. 2. The transverse ligament, sending offsets upwards and downwards. the root of the odontoid process, and sends upwards and downwards a slip to the occipital bone and the axis. The upper offset from the transverse ligament may be cut through afterwards for the purpose of seeing the check ligaments which diverge, one on each side, from the odontoid process. The lateral odontoid or check ligaynents (fig. 49, are two strong bun- dles of fibres, attached by one end to the side of the head of the odontoid process, and by the other to a depression on the inner surface of the con- dyle of the occipital bone. These ligaments are covered by the occipito- axoidean band ; their upper fibres are short and almost horizontal, and the lower are longer and oblique. Between the lateral bands is a central odontoid ligament^ which connects the tip of the odontoid process to the margin of the basilar process of the occipital bone. Union of the atlas with the axis. (fig. 49, is a flat, strong, arched band behind the odontoid process, which is attached on each side to a tubercle below the inner part of the articular process. This ligament is widest in the centre; and at this spot it has a band of longitudinal fibres connected with the upper and lower margins (fig. 49), so as to produce a cruciform appearance ; the upper piece is inserted into the basilar process, and the lower into the body of the second vertebra. Its surface towards the cord is con- cealed by the occipito-axoid liga- ment. The transverse ligament of the atlas Fig. 50. First Vertebra with the Odontoid Process REMOVED FROM THE SOCKET FORMED BY THE Bone and the Transverse Ligament. 1. Transverse ligament with its offsets cut. 2. Socket for the odontoid process. 170 DISSECTION OF THE NECK. This ligament fixes the odontoid process of the second vertebra against the body of the atlas, confining it in a ring (fig. 50). Wlien the transverse and check ligaments have been cut through, the tip of the odontoid process will be seen to have two cartilaginous surfaces ; one in front where it touches the atlas, the other at the opposite aspect, where it is in contact with the transverse ligament. Two synovial mem,- hranes facilitate tlie movements of the odontoid process, one serving for the joint between this piece of bone and the atlas ; and the other for the joint between it and the transverse ligament. Union of the articular surfaces. The articular surfaces of the occipital bone and atlas are surrounded by a capsular, ligament of scattered fibres, which is strongest externally and in front. When the joint is opened, the condyle of the occipital bone will be seen to look somewhat outwards, and the hollowed surface of the atlas inwards. A synovial membrane is pre- sent on each side. The articular surfaces of the first two vertebrae are inclosed on each side by a capsule (fig. 4G, ^), which is stronger in front than behind. On opening the joint the surfaces of the bones may be perceived to be almost horizontal. On each side tliere is a separate loose synovial membrane. Movements of the head. The head can be bent forwards and backwards; turned from side to side — rotation ; and inclined towards the shoulder. Nodding takes place in the joints between the atlas and the occipital bone, the condyles gliding forwards and backwards. When the head is moved more freely, flexion and extension of the cervical vertebrae come into play. Rotation is permitted by the several joints between the atlas and axis. In this movement the axis is fixed, and the atlas, bound to it by the transverse ligament, moves to the right and the left, carrying the weight of the head. Too great a movement of the face to the side is checked by the odontoid ligament. Only part of the wliole of the rotatory movement to one side is obtained between the atlas and axis, the rest being made up by the neck. Approximation of the head to the shoulder is effected by the neck move- ment: perhaps a very slight degree of it may be due to gliding downwards of the occipital condyle of the same side on the articular surface of the atlas. Stp:rno-clavicular Articulation (fig. 51). The articular surfaces are somewhat irregular and adapted to each other, with an intermediate flbro-cartilage ; and they are retained in contact by a capsular ligament; by a band to the first rib ; and by another band between the ends of the clavicles. Dissection. For the examination of the ligaments of the sterno-clavicu- lar articulation, take the ])iece of the sternum that was set aside for the pur[)Ose (p. 134). If the ligaments have become dry, they may be moist- ened for a short time. The several ligaments will appear in the situation indicated by their names, after the removal of some fibrous tissue. Capsular ligament. This is a thin membranous ex{)ansion (fig. 51, ^), which incases the articular ends of the bones and the fibro-cartilage. It is attached near the articular surface of each bone, and is thinner before than behind. Sometimes the stronger fibres in front and at the back are described as separate ligaments. The inter clavicular ligament (fig. 51, ^) extends above the sternum, between the ends of the clavicles. The fibres do not cross in a straight STERNO-CLAVrCULAR JOINT. 171 line, but dip into the hollow between the collar bones, and are connected with the upper piece of the sternum. The costo-clavicular ligament (fig. 51, is a short strong band of ob- lique fibres between the first rib and the clavicle. Interiorly it is fixed to the upper surface of the cartilage of the first rib, and superiorly to a tuber- cle on the under surface of the clavicle near the sternal end. The sub- clavius muscle is in front of the ligament. Sometimes the clavicle touches the rib, and is provided with an articular surface and a synovial membrane. The inter articular Jibro-cartilage (fig. 51, '^) will come into view by cutting the ligaments before described, and raising the clavicle. It is ovalish in form and fiattened, but is thicker at the circumference than tlie centre. By its upper margin and surface the cartilage is united to the head of the clavicle which is imbedded in it; and by the opposite surface and margin it is inserted into the cartilage of the first rib. At its cir- cumference it unites with the capsule of the joint. Sometimes there is an aperture in the centre of the fibro-cartilage. Two synovial sacs are present in the articulation, one on each side of the fibro-cartilage. The sac in contact with the sternum is looser than that touching the clavicle. Movement. The inner end of the clavicle can be moved up and down, and forwards and backwards, and the direction it takes is the opposite to Fig. 51. Ligaments of the Inner End of the Ceavicle, and of the Cartilage of the Second Rib. 1. Capsule. 4. Ligaments of the second rib with the sternum. 2. Costo-clavicular ligament. 6. Interarticular fibro-cartilage of second rib. 3. Interclavicular ligament. 7. Interarticular fibro-cartilage of the clavicle. that of the shoulder : thus when the limb is depressed the sternal end of the clavicle is raised ; and so on in the other movements. The extent of each movement is but limited, though those forwards and upwards are the freest , and dislocation may ensue in any direction except downwards, from force applied to the limb. 172 DISSECTION OF THE BRAIN. CHAPTER IL DISSECTION OF THE BRAIN. Section I. MEMBRANES AND VESSELS. During the examiniition of the membranes, vessels, and nerves, the brain is to be placed upside down, resting in the coil of a cloth which sup- ports it evenly. Membranes op the Brain. The coverings of the brain (meninges) are three in number, viz., dura mater, pia mater, and arachnoid mem- brane. Tlie dura mater is a firm fibrous investment, which supports part of the brain, and serves as an endosteum to the bones. The pia mater is the most internal layer, and is very vascular. And the arachnoid is a thin serous sac, which is situate between the other two. Besides enveloping the brain, tliese membranes are prolonged on the cord into the spinal canal. Only the cranial part of the two last will be now noticed. For the description of the cranial part of the dura mater, see p. 24. The ARACHNOID is a thin serous membrane, which lines the inner sur- face of the dura mater, and is reflected over the pia mater and the brain. Around the vessels and nerves that intervene between the skull and the brain, the membrane forms sheaths, which extend a short distance into the several apertures, and then become continuous with the parietal or cranial portion. Like other serous membranes, it forms a sac which con- tains a lubricating moisture ; and it consists of a parietal and a visceral part. The parietal part is inseparably united to the inner surface of the dura mater, giving this a smooth and polished surface, and is continued over the pieces of the fibrous membrane projecting between portions of the brain. The visceral part covers the encephalon loosely, especially at the under surface of the brain, but is united to the underlying pia mater by fibrous processes ; beneath it there is a considerable interval (subarachnoid space). On the upper or convex surface of the great brain the membrane passes from one convolution to another, without dipping into the intervening sulci ; though it lines the great median fissure as low as the extent of the falx. On the lower surface of the cerebrum there is a large space between it and the centre of the brain. Still more posteriorly, between the hemispheres of the little brain, there is an interval, similar to that at the under part of the cerebrum. The subarachnoid space, or the interval between the arachnoid mem- brane and the pia mater, is larger in one spot than another; and it con- MEMBRANES OF THE BRAIN. 173 tains more or less flaid, which has been named cerebrospinal. Tlie space is largest at the under part of the great brain, about its middle, and in the fissure between the hemispheres of it and the cerebellum. Under the arachnoid, in the fissure between the halves of the cerebellum, is the aper- ture of the fourth ventricle, by which that cavity communicates with the subarachnoid space. The PiA MATER closely invests the different parts of the brain, and dips into the fissures, as well as into the sulci between the convolutions and laminae. Besides covering the exterior of the brain, it sends processes into the interior to supply vessels to the walls of the inclosed space : thus, one penetrates into the cerebrum below the cor[)US callosum, and is named velum interpositum ; and two vascular fringes, which project into the fourth ventricle, are known as the choroid plexuses of that cavity. This membrane is a network of vessels, and is constructed of the minute ramifications of the arteries and veins entering into or issuing from the cerebral substance ; whilst the intervals between the vessels are closed by fine areolar tissue, so as to form a continuous thin layer. From the under surface of the membrane proceed numerous fine vessels for the nutrition of the brain. Vessels and nerves. The arachnoid membrane has but few vessels, whilst the pia mater is composed almost entirely of vessels. The pia mater is largely supplied by offsets of some cranial nerves, and by branches of the sympathetic which accompany the vessels at the base of the brain (p. 33). Bochdalek has described branches to the arachnoid from some cranial nerves. Subdivisions of the encephalon. Before the description of the arteries is given, the chief subdivisions of the encephalon will be shortly noticed. The cranial or encephalic mass of the nervous system consists of cere- brum or great brain, cerebellum or small brain, pons, and medulla oblon- gata. Each of these parts has the following situation and subdivisions : — The medulla oblongata, or the upper end of the spinal cord, lies in the groove between the halves of the small brain, and is divided into two symmetrical parts by a median fissure. To it several of the cranial nerves are united. The pons Varolii is situate in front of the medulla oblongata, and is marked along the middle by a groove, which indicates its separation into halves. Anterior to it are two large processes (crura cerebri) connecting it to the great brain ; on each side it is united to the small brain by a sim- ilar white mass (crus cerebelli) ; and behind it is the enlarged upper part of the cord. The cerebellum, or the small brain, is separated into two by a median fissure, and each half will be subsequently seen to consist of lobes. The cerebrum, or the large brain, is divided into hemispheres by a longitudinal fissure in the middle line ; and each half is further subdivided into two by a transverse sulcus — the fissure of Sylvius. In the centre of the cerebrum, between the hemispheres and in front of the pons, are seve- ral small bodies that will be afterwards enumerated. Dissection. To follow out the arteries, let the brain remain upside down, and let the remains of any arachnoid membrane be removed. Hav- ing displayed the trunks of the vertebral arteries on the medulla oblon- gata, and those of the carotid in front near the median fissure of the large brain, the student should lay bare on one side the branches to the large 174 DISSECTION OF THE BRAIN. brain. Define first the two arteries lying in tlie median fissure and join- ing by a short brancli ; next, an artery that passes outwards transversely in the fissure of Sylvius, and pursue it to the outer surface of the hemis- phere. Look then for a much smaller vessel (choroid), which enters into the brain substance on the outer side of the crus cerebri. By gently raising the cerebellum on the same side, the last artery of the cerebrum may be traced back along the inner aspect of the hemisphere. Two arteries pass out to the small brain. One on the upper surface may be brought into view on raising the cerebellum ; and care is to be taken of the slender fourth nerve which lies by its side. The other artery turns inwards to the median hollow of the cerebellum, and may be easily followed. Arteries of the Brain (fig. 52). Tlie brain is supplied with blood by the vertebral and internal carotid arteries. The VERTEBRAL ARTERY, is a branch of the subclavian trunk (p. 77), and enters the trunk through the foramen magnum ; directed upwards round the medulla oblongata, it blends with its fellow in a common trunk (basilar) at the lower border of the pons. As the vessel winds round the upper part of the cord, it lies between the roots of the suboccipital and hypoglossal nerves ; but it is afterwards internal to the last. Fig. 52. 1. Internal carotid trunk. 2. Anterior cei'ebral branch. .3. Anterior communicating. 4. Middle cerebral branch. 5. Choroidal branch. 6. Posterior communicating. 7. Posterior cerebral branch. 8. Upper cerebellar branch. 9. Internal auditory branch. 10. Inferior cerebellar branch. 11. Basilar artery. 12. Vertebral artery. 13. Anterior spinal branch. Branches. Between its entrance into the spinal canal and its termina- tion, each artery furnishes offsets to the spinal cord, the dura mater, and the cerebellum. a. The posterior spinal branch is of inconsiderable size, and arises opposite the posterior part of the medulla : it descends along the side of the cord, behind the nerves, and anastomoses with its fellow, and with branches that enter by the intervertebral foramina. b. The anterior spinal branch (’®) is small like the preceding, and springs from the artery ojiposite the front of the spinal cord. It joins the corresponding twig on the opposite side, and the resulting vessel is con- tinued along the middle of the cord on the anterior aspect. c. The posterior meningeal artery leaves the vertebral trunk opposite ARTERIES OF THE BRAIN. 175 the foramen magnum, and ramifies in the dura mater lining the fossa of the occipital hone. d. The inferior cerehellar artery (posterior) is distributed to the under surface of the cerebellum. Taking origin from the end of the vertebral, this branch wdnds backwards round the medulla between the pneumogastric and spinal accessory nerves, to the median fissure of the cerebellum. Directed onwards along the fissure the artery reaches the upper surface of the small brain, and there anastomoses with the superior cerebellar arteiy. An offset of this branch ramifies over the under part of the cerebellum, and ends externally by anastomosing with the artery of the upper surface. As the vessel lies by the side of the aperture of the fourth ventricle it gives a small choroid offset to the plexus of that cavity. The BASILAR ARTERY (”), formed by the union of the two vertebrals, reaches from the lower to the upper border of the pons, where it ends by dividing into two branches (posterior cerebral) for the cerebrum. The vessel touches the basilar process of the occipital bone, from that circum- stance receiving its name, and lies in the median groove of the pons. On each side of, and almost parallel to it, is the sixth nerve. Branches. Besides the two terminal branches mentioned above, the artery supplies transverse offsets to the pons and the under part of the cerebellum, and a large branch to the upper surface of the cerebellum. a. The transverse arteries oi the pons are four or six small twigs, which are named from their direction, and are distributed to the substance of the pons. One of them (®) gives an offset (auditory) to the internal ear along the auditory nerve. b. Resembling this set of branches is the following artery, the inferior cerebellar (anterior) : this arises from the basilar trunk, and extends to the fore part of the under surface of the cerebellum, on which it is dis- tributed. c. The superior cerebellar artery (®) is derived from the basilar so near the termination as to be often described as one of the final branches of that vessel. Its destination is to the upper surface of the small brain, to which it is directed backwards over the third nerve and the crus cerebri, but parallel with the fourth nerve. On the upper surface of the cerebellum the artery spreads its ramifications, which anastomose with the vessel of the opposite side, and with the inferior cerebellar artery. Some twigs of this vessel enter the piece of the pia mater (velum inter- positum), which projects into the posterior part of the cerebrum. d. The 'posterior cerebral artery (^) takes on each side a backward course, similar to that of the preceding artery, but separated from it by the third nerve. The vessel is then applied to the inner surface of the cere- brum, and divides into many branches : some of these supply the under part, whilst others turn upwards on both the outer and inner surfaces of the back of the hemisphere, and anastomose with the other cerebral arteries. Near its origin it is joined by the posterior communicating artery of the carotid ; and its branclies to the brain are the following : — Numerous small long branches leave it close to its origin, and enter the base of the brain between the crura cerebri (posterior perforated spot). A small choroid artery (posterior) supplies the fold of pia mater that projects into the cerebrum : this small branch is transmitted between the 176 DISSECTION OF THE BRAIN. crus and hemisphere of the cerebrum to the velum interpositum and the choroid plexus. From the foregoing examination of the offsets of the vertebral arteries and the basilar trunk, it appears that about half the encephalon — viz., the medulla oblongata, the pons, the cerebellum, and the posterior third of the cerebrum — receives its blood through the branches of the subclavian arteries. The INTERNAL CAROTID ARTERY Q) terminates in branches for the re- maining part of the cerebrum. The vessel emerges from the cavernous sinus (p. 33) inside the anterior clinoid process, and divides at the inner end of the fissure of Sylvius into cerebral and communicating arteries. At tlm base of the brain the carotid lies between the second and third nerves, but nearest the former. Branches. In the skull the carotid gives off the ophthalmic offset, before it ceases in the following terminal branches to the cerebrum. a. The anterior cerebral artery (‘^) supplies the inner part of the cerebral hemisphere. It is directed forwards to the median fissure between the halves of the large brain ; and as it is about to enter, it is united to its fel- low by a short thick branch — the anterior communicating (^). Then passing into the fissure, it bends round the anterior part of the corpus callosum, so as to be placed on the upper aspect in the natural position of the brain, and is continued backwards distributing offsets nearly to the posterior extremity of the hemisphere. It gives off numerous branches, and some of them supply the base of the cerebrum, thus : — Near the commencement it furnishes small branches to the part of the brain (anterior perforated spot) contiguous to the inner end of the fissure of Sylvius : and it distributes some branches to the under part of the frontal lobe. b. The middle cerebral artery (^) is the largest offset of the carotid, and ramifies over the outer side of the hemisphere. Entering the fissure of Sylvius, the artery divides into many large branches, which issue at the outer end of that groove, and, spreading over the external surface of the hemisphere, inosculate with the other two cerebral arteries at the front, the back, and the upper part of the brain. Only a few fine offsets require special notice : A set of small branches arise at the inner end of the fissure of Sylvius, and enter the cerebral substance through the substantia perforata antica. c. The posterior communicating artery (^) is a small twig, which is directed backwards parallel to, and on the inner side of the third nerve, to join the posterior cerebral artery (of the basilar) near the pons. d. The choroid, artery (anterior) (^) is small in size, and arises either from the trunk of the carotid, or from the middle cerebral artery : it passes backwards on the other side of the preceding, and finds its way between the hemisphere and the crus cerebri to the choroid plexus of the lateral ventricle. Circle of Willis. The arteries at the under part of the brain are united freely both on their own side and across the middle line in an arterial anastomosis, — the circle of Willis. On each side this circle is formed by the trunk of the internal carotid giving forwards the anterior cerebral, and backwards the posterior communicating artery. In front it is constructed by the converging anterior cerebral, and the anterior communicating ORIGIN OF CRANIAL NERVES. 177 artery. And behind is the bifurcation of the basilar trunk into the poste- rior cerebrals. In the area of tlie circle lie several parts corresponding with the floor of the third ventricle. The comjdete inosculation between the cranial vessels in the circle of Willis allows at all times a free circulation of blood througli the brain, even though a large vessel on one side of the neck should be obstructed. The VEINS of the brain enter the sinuses of the dura mater, instead of uniting trunks as companions to the arteries. Two sets of veins belong to the cerebrum, viz., superficial or external, and deep or internal. The external veins of the upper surface are collected into the superior longitudinal sinus (p. 29); and those of the lateral and under parts enter the sinuses in the base of the skull, especially the lateral sinus. The deep veins of the interior of the cerebrum join the veins of Galen, and reach the straight sinus. The veins of the cerebellum end differently above and below. On the upper surface they are received by the veins of Galen and the straight sinus; and on the lower surface they terminate in the occipital and lateral sinuses. Dissection. Tlie pia mater and the vessels are now to be stripped from the brain, and the origin of the cranial nerves is to be defined. Over the greater part of the cerebrum, the pons, and the medulla, the pia mater can be detached with tolerable facility by using two pairs of forceps ; but on the cerebellum the membrane adheres so closely as to require some care in removing it without tearing the substance of the brain. In clearing out the fissure between the halves of the cerebellum on the under surface, the membrane bounding the opening of the fourth ventricle will probably be taken away: therefore the position, size, and limits of that opening between the back of the medulla oblongata and the cerebel- lum should be now noted. When the surface has been cleaned, the brain is to be replaced in the spirit, but it is to be turned over occasionally, so that all the parts may be hardened. Section II. ORIGIN OF THE CRANIAL NERVES. The cranial nerves take origin from the encephalon, with one exception (spinal accessory), and pass from it througli apertures in the skull. The origin of a nerve is not determined by the place at which it appears on the surface of the brain, for fibres or roots may be traced deeply into the brain substance. Each nerve has therefore a superficial or apparent, and a deep or real origin in the encephalon. With respect to the superficial attachment there cannot be any doubt ; but there is much difference of opinion concerning the deep origin, in con- sequence of the difficulty of tracing the roots. When the roots are followed into the encephalon, they enter masses of gray substance, which are looked upon as ganglia of origin. 12 178 DISSECTION OF THE BRAIN. The cranial nerves may be regarded either as nine or twelve pairs, according to the mode of classifying themd The several nerves may be designated first, second, third, and so forth : this numerical mode of naming applies to all, and is the one generally used. But a second name has been derived for some of the nerves from the parts to which they are supplied ; as instances of this nomenclature the terms hy})oglossal, pneumogastric, may be taken. And a different ap- pellation is given to others, in consequence of the function conferred on the part to which they are distributed, as the terms auditory and olfactory express. In this way two names may be employed in referring to a nerve: one being numerical, the other local or functional, as is exemplified below. The FIRST OR OLFACTORY NERVE (olfactory process) (fig. 53,^) is soft Fig. 53. 1. Olfactory. 2. Optic. 3. Motor oculi. ' ‘ 4. Trochlear. 5. Trigeminal with small and large root. 6. Abductor ocoli. 7. Facial and auditory, the former smaller and internal. 8. Eighth nerve consisting of three trunks in a line; the upper, glosso- pharyngeal ; the middle, pneumo- gastric ; and the lowest spinal ac- cessory. 9. Roots of attachment of the hypoglossal nerve. Oriuin of the Cranial Nerves. and pulpy, being destitute of a neurilemma ; and it may be considered an advanced part of the brain, for it has both gray substance and white fibres in its composition, like the cerebrum. The olfactory process is a flat-looking band, wider at each end than in the middle, Avhicli is lodged in a sulcus on the under aspect of the frontal lobe of the cerebrum, and is kept in position by the reflection of the arach- noid membrane over it. When the so-called nerve is raised from the • Those anatomists, who take the smaller number after the example of illis, include in one nerve all the trunks contained in the same aperture of the skull : as in the case of the eighth nerve, which consists of three trunks in the loramen jugulare. But those who are disposed with Sommerring to enumerate twelve nerves, consider each of the three trunks of the eighth mo ve before mentioned, to constitute a separate cranial nerve, notwithstanding that it may be combined with others in the foramen of exit. ORIGIN OF CRANIAL NERVES. 179 sulcus, it is prismatic in form, tlie apex of the prism being directed down- wards (in this position). Anteriorly the nervous substance swells into the olfactory hulb , — a pyri- form grayish mass, about half an inch in length, which rests on the ethmoid bone, and distributes nerves to the nose. Posteriorly the olfactory process is connected to the cerebrum by three roots, external, internal, and middle. The external or long root is a slender white band, which is directed backwards along the outer part of the anterior perforated space, and across the fissure of Sylvius, and sinks into the substance of the cerebrum. The internal or short root^ not always visible, is white and delicate, and comes from the inner part of the cerebrum. The middle or gray root is connected with the gray matter on the sur- face of the brain by means of a conical elevation at the back of the sulcus which lodges the nerve. Deep origin. The external root is said to be traceable to one of the convolutions of the island of Reil. Tlie inner root joins a band of white fibres connected with a convolution (gyrus fornicatus) to be afterwards examined. And the middle root, continuous with the gray matter of the convolutions, contains white fibres which enter the corpus striatum. The SECOND or optic is the largest of the cranial nerves except the fifth, and appears as a flat band on the crus cerebri. Anteriorly the nerves of opposite sides are united in a commissure. The part of the nerve pos- terior to the commissure is named optic tract ; but the part beyond the commissural union, which is round and firm, is called optic nerve. The destination of the nerve is to the eyeball. The origin of the nerve will be afterwards seen to come from the optic thalamus and the corpora geniculata, and from one of the corpora quadri- gemina (nates). The tract is the flattened part of the optic winding round the peduncle of the cerebrum. In front it ends in the commissure, and behind it splits into two pieces by which it is fixed to the brain. As the tract reaches forwards it crosses the crus cerebri, to which it is attached by its outer or anterior edge ; and in front of the crus it is placed between tlie substantia perforata antica on the outside, and the tuber cinereum on the inside, but whether it receives filaments from the latter is uncertain. The commissure (chiasma) of the nerves measures half an inch across, and lies on the olivary eminence of the sphenoid bone, within the circle of Willis. It is placed in front of the tuber cinereum ; and passing be- neath it (in this position of the brain) is the thin lamina cinerea. In the commissure each tract is resolved into three sets of fibres with the following arrangement : — the outer fibres, few in number, are continued straight to the eyeball of the same side. The middle, the largest, decus- sate with the corresponding bundle of the other tract, — those of the right nerve being continued to the left side, to the opposite eye, and vice versdi. And the most internal are continued through tlie tract of the other side back to the brain without entering the eye. At the front of the commis- sure are placed some transverse fibres, which are prolonged to the eyeballs through the part of each nerve in front of the commissure, but have not any connection with the tracts and the brain. The part called nerve extends from the commissure to the eyeball. Leaving the skull by the optic foramen, it receives a tube of dura mater. 180 DISSECTION OF BRAIN. and its course in the orbit is described in p. 56. In tlie eyeball it ends in the retina. The THIRD NERVE (^), Hiotor nerve of the eyeball, is round and firm, and is attached by a slanting line of threads to the inner surface of the cerebral peduncle, near the locus perforatus, and close in front of the pons Yarolii. Deep origin. The deep origin is uncertain. According to Stilling, • the fibres of the nerve pierce the peduncle, passing through the locus niger, and enter a nu- cleus of gray substance near the floor of the aqueduct of Sylvius. The FOURTH or trochlear nerve (^) cannot be followed backwards at present to its origin. It is the smallest of the cranial nerves, and issues from the valve of Yieussens over the fourth ventricle (fig. 68, ^). The nerve appears between the cerebrum and the cerebellum, on the side of the crus cerebri ; and is then directed forwards to enter an aperture in the free edge of the tentorium cerebelli near the posterior clinoid process. Deep origin. In entering the valve of Vieussens, filaments of the nerves of oppo- site sides cross and communicate. Each divides into two parts : the anterior enters a nucleus of gray matter on the side of the aqueduct of Sylvius ; the posterior joins a nucleus (ujjper trigeminal) near the top of the fourth ventricle (Stilling). The FIFTH or trigeminal is the largest of all the cranial nerves, and consists of two roots, ganglionic or sensory, and aganglionic or motor, vdiich are partly blended in one trunk beyond the ganglion. The nerve is attached to the side of the pons Yarolii, nearer the upper than the lower border (^). The small or aganglionic root is highest, and is separated from the large one by two or three of the transverse fibres of the pons. Both roots pass outwards through an aperture in the dura mater, above the petrous part of the temporal bone, and are blended in the peculiar manner stated in page 31. Both roots penetrate the fibres of the pons, and are connected with nu- clei in the floor of the fourth ventricle. Deep origin. The large root divides into two parts near the mass of gray matter called locus cjeruleus (p. 217). One piece arises from the gray matter near the locus cjeruleus (upper trigeminal nucleus) ; and the other, from a deeper nucleus, lower trigeminal^ opposite the lower border of the pons, within the fasciculus teres (Stilling). The small root begins with the fourth nerve in the upper trigeminal nucleus near the top of the fourth ventricle (Stilling). The SIXTH NERVE (®), abducent nerve of the eyeball, springs from the pyramidal body close to the pons, and by a second band from the lower part of the pons. Deep origin. The fibres of the nerve bend backwards, through the medulla oblongata, to a nucleus in the floor of the fourth ventricle, whose position is on the outer part of the fasciculus teres, and behind the anterior fossa. See Anatomy of the Fourth Ventricle (p. 217). The SEVENTH CRANIAL NERVE (Willis) (’) appears at the lower border of the pons near the restiform body. It consists of two distinct trunks, facial and auditory ; the former being the motor nerve of the face, and the latter the s})ecial nerve of the organ of hearing. The Jacial nerve (portio dura, seventh nerve, Sbmmerring) is firm and * Untersuchungen uher den Bail des Ilirnknotens. OKIGIN OF CRANIAL NERVES. 181 round, and smaller than the auditory, internal to which it is placed. It issues from the lateral tract of the medulla at the upper part, and is con- nected by a slip with the lower border of the pons. The facial nerve receives a small accessory band of fibres (intermediate portion of Wrisberg) from the same part of the medulla, and enters the internal meatus with the auditory trunk. The auditory nerve (portio mollis, eighth nerve, Sommerring) has a surface attachment to the restiform body and the floor of the fourth ven- tricle. The nerve is very soft, and receives one of its names from that fact. Deep origin. The facial nerve penetrates to tire floor of the fourth ventricle, and arises from the same nucleus as the sixth nerve, which it joins (Clarke •). The fasciculus of the auditory nerve which reaches the floor of the fourth ventri- cle, bends backwards over the restiform body to the auditory nucleus ; and some arciform fibres out of the median sulcus are joined with this part of the root. The other fasciculus pierces the restiform body, and takes origin from a network connected with the posterior pyramid (Clarke). The EIGHTH cranial nerve (Willis) (®) is placed along the side of the medulla oblongata, and consists of three distinct trunks, glosso- pharyngeal, pneumogastric, and spinal accessory : the names of the first two indicate their destination ; and the last, besides being accessory to the pneumogastric, supplies some muscles. The glosso-pharyngea.l nerve (ninth nerve, Sommerring) is the smallest of the three, and is situate highest. Its apparent origin is by three or more fibrils, which penetrate the lateral tract of the medulla close to the facial nerve. The pneumogastric or vagus (tenth nerve, Sommerring) is connected with the lateral tract of the medulla, below the glosso-pharyngeal nerve, by a series of filaments, which are collected at first into bundles, but are finally gathered into one fiat band. The spinal accessory nerve (eleventh nerve, Sommerring) consists of two parts — accessory to the vagus, and spinal. The accessory part is of small size, and arises by fine filaments in a line with the root of the vagus, as low as the first cervical nerve. Finally this fasciculus throws itself into the pneumogastric nerve outside the skull. (See p. 114.) The spinal part is firm and round, like the third or the sixth nerve, but only a small piece of it can be seen. It arises by a number of fine fila- ments from the lateral column of the spinal cord near the lateral fissure, as low as the sixth cervical nerve. As the nerve ascends along the side of the cord it lies between the ligamentum denticulatum and the posterior roots of the spinal nerves, with the up{)er of which it may be connected; and it finally enters the skull by the foramen magnum. All three nerves converge below the crus cerebelli, and rest on a small lobe of the cerebellum (flocculus). From that spot they are directed out- wards to the foramen jugulare (p. 32). The fibrils of the nerves pierce the medulla ; and each nerve, except the spinal part of the last, takes origin from a special deposit of gray matter at the back of the medulla oblongata, and near the lower of the fourth ven- tricle (p. 217). ' On the structure of the Medulla Oblongata, by J. Lockhart Clarke, F. R. S., in the Philosophical Transactions for 1858, part i. 182 DISSECTION OF THE BRAIN. Deep origin. The glosso-pharyngeal penetrates as far as the vagus nucleus, wliere it ends in fibres which enter that deposit. The vagus nerve arises in a special nucleus (p. 217) ; but some fibres pass through the hypoglossal nucleus. The accessory part of the spinal accessory nerve is transmitted to a special nucleus below that of the vagus ; and some fibres decussate across the middle line with their fellows. The roots of the spinal part of the nerve, piercing the lateral column of the cord, pass through a collection of cells to the anterior cornu of the crescent (Clarke). The NINTH or hypoglossal nerve of Willis (tw^elfth nerve, Sommer- ring) (®) is placed on the front of the medulla oblongata, and arises by a series of filaments from the sulcus between the pyramidal and olivary bodies, in a line with the anterior roots of the spinal nerves. The filaments of origin unite into tw'O bundles, which pierce separately the dura mater, and do not blend together till they are outside the cranial cavity. Deep origin. The filaments of the nerve can be traced through the corpus olivare to a nucleus below the level of the fourth ventricle, and in front of the canal of the cord ; but some bend inwards to decussate through the raphe with the nerve of the opposite side (Clarke). Section III. MEDULLA OBLONGATA AND PONS VAROLII. The medulla oblongata and the pons are interposed between the spinal cord and the brain proper. Directions. On a single brain the student may ascertain nearly all the anatomy of the parts composing the medulla and the pons ; but if he can procure one hardened specimen of the medulla and the pons united, and another of a vertical median section through those bodies, he will compre- hend much more readily the following description. Position. The brain is to remain in the same position as for the exami- nation of the nerves and vessels. The MEDi LLA OBLONGATA is the dilated upper part of the spinal cord which is contained in the cranium (fig. 54). Its limit is the lower border of the pons in one direction, and the upper margin of the atlas in the other. This part of the cord is pyramidal in form, and measures about one inch and a quarter in length ; half an inch in breadth belowq and about an incli at its widest part. Its base joins the pons, the transverse fibres of the latter marking its limit ; and its apex is blended with the spinal cord. The anterior surface is irregularly convex, and is in contact with the ho!lo\ved basilar process of the occipital bone. The opposite surface is somewhat excavated supe- riorly, where it forms the floor of th i fourth ventricle ; and it rests in the fissure between the halves of the cerebellum. On the posterior aspect there are not any cross fibres of the pons, as in front, to mark the extent of the medulla. The medulla oblongata is divided into halves by a median fissure in front and behind. The fissures are in a line with those along the cord ; the anterior ceases at the pons in a dilated part (foramen caecum), but MEDULLA OBLONGATA. 183 the posterior is prolonged, behind the pons*, into the floor of the fourth ventricle. Each half of the medulla is constituted of pieces continuous with those of the spinal cord (fig. 54); and slight grooves indicative of these divi- sions are to be seen on the surface. Thus at the middle line in front is the anterior pyramid (^) corresponding with the anterior column of the cord ; at the middle line behind is the small posterior pyramid (*) con- tinuous with the posterior median column. On the side is the larger pro- jecting restiform body (^), joining below the posterior column of the cord; and between this and the anterior pyramid is the lateral tract ('^), with an oval projecting body (corpus olivare) (^) on the exterior, which blends below with the lateral column. Fig. 54. Anterior View of the Medulla Oblongata AND Pons. ]. Anterior pyramid. 2. Lateral tract. 3. Restiform body. Ck Corpus olivare. 6. The decussation. The anterior 'pyramid (fig. 54, is the most internal eminence and receives its name from its position and form. Situate on the side of the median fissure, it is internal to the olivary body, from which it is sepa- rated by a slight groove. P]nlarging as it ascends, this body enters the pons, but before disappearing beneath the transverse fibres, it is somewhat constricted and rounded. Lateral tract and olivary body. The lateral tract (funiculus lateralis) (^) fills the interval between the anterior pyramid and the restiform body. Its surface width is not the same throughout : opposite the lower part of the medulla oblongata it measures as much as the pyramid ; but near the pons it is concealed by the olivary body, so that it is seen only in the narrow interval between the outer side of the corpus olivare and the resti- form body. The olivary body (corpus olivare) (^) is an oval projection, about half Fig. 55. 1. Floor of the fourth ventricle. 2. Eminentia teres. 3. Restiform body. 4. Posterior pyramid. 184 DISSECTION OF THE BRAIN. an inch long. A shallow groove separates it from the pyramid, and a deeper and wider one intervenes between it and the restiform body. This eminence is shorter than the pyramid, and does not reach to the pons. Its upper end is most prominent; and arching round the lower end, and over the surface, are some white fibres (fibrse arciformes). Restifarm body (^). The restiform body (restis, a rope) forms the largest prominence on the half of the medulla oblongata, and cannot be seen satisfactorily except on a distinct preparation. It is posterior to the lateral tract, and projects on the side, so as to give the width to the upper part of the medulla oblongata. Behind, the restiform bodies diverge above from each other, and between them is the space of the fourth ventricle. The posterior pyramid (funic, gracilis) (fig. 55, ^) lies along the side of the posterior median fissure, and is much narrower than either of the other component pieces. By drawing forwards the medulla it will be seen to be slightly enlarged (clava) at the apex of the fourth ventricle, and then to become gradually indistinct along the inner part of the corpus restiforme. Structure. From the interposition of the medulla oblongata between the brain and the spinal cord, it is continuous with both. Below, the con- stituent pieces of the half join directly (as before said) those of the spinal cord ; but, above, they are continued chiefly to the cerebrum, only one piece (restiform) entering the cerebellum. Dissection (fig. 56). The student has now to show the continuity of the constructing parts of one-half of the medulla oblongata with those of the Fig. 56. a. Anterior pyramid. b. Decussation of the medulla oblon- gata (decussation of the pyra- mids). c. Fibres of the pyramid in the pons. d. Fibres of the pyramids in the crus cerebri. e. Suiierficial fibres of the pons, cut through and reflected. /. Superficial fibres of the pons, in place. Fibres of the Medulla, Pons and Crus Cerebri. « spinal cord. Let him trace out first the fibres of the pyramid on the right side : in it two sets of fibres have to be shown — one from the same, and one from the ojiposite side of the cord. The fibres from the opposite half of the cord will ajipear in the median fissure, when the pyramids are gently drawn from one another, where they are named the decussating fibres ; and to lay these bare more completely, the small part of the anterior FIBRES OF OBLONG MEDULLA. 185 column of the cord on the opposite side, which remains below the cross fibres (for the cord has been cut through near these), may be forcibly turned outwards. The anterior pijramid (fig. 5G, a) receives fibres inferiorly from the anterior column of the cord of its own side, and from the opposite half of the cord. The inner set of fibres, b, deep at their origin, become super- ficial, and are directed upwards, close to the median fissure, joining the fibres continued from the anterior column of the cord ; and as the inner fibres of each pyramid are derived from the opposite side, they cross each other in the median line — forming thus the decussation of the medulla ob- longata. The fibres of the pyramid are white and longitudinal, and are collected into a bundle of a prismatic form. Superiorly they enter the pons (fig. 5G), to reach the cerebrum. Dissection. For the purpose of seeing the arrangement of the fibres of the lateral tract, the anterior pyramid is to be cut across on the right side, between its decussation and the olivary body (fig. 57), and to be raised towards the pons. The lateral tract of the medulla is prolonged inferiorly into the portion of the spinal cord between the anterior and posterior roots of the nerves. The continuation of the tract (fig. 57) ascends beneath the olivary body, and leaving the surface of the medulla enters the pons. The olivary body, and its fillet (fig. 57, c). Tlie olivary mass consists of three parts, viz., a gray incasing layer, a nucleus, and a band prolonged from it — the fillet. Fig. 57. a. Anterior pyramid fibres, cut through, and raised as far as the optic thalamus. h. Lateral tract of the medulla oblongata. e. Olivary body, and fillet of the olivary body issuing at the upper end. d. Fibres of the lateral tract in the pons and crus cerebri. e. Superficial, and f. Deep transverse fibres of the pons, cut through, and turn- ed outwards. g. Locus niger in the crus cere- bri, between the fibres of the lateral tract and pyramid. Fibres of the Lateral Tract and of the Olivary Body. When the olivary body has been sliced obliquely, a very thin wavy layer of gray substance surrounding a nucleus of whitish matter will be apparent: this is the coqius dentatum (fig. 58, y). It forms a thin cap- sule or bag, having a zigzag outline in a section, with the dilated part 186 DISSECTION OF THE BRAIN. towards the surface, and the narrowed part or neck open and directed backwards near the middle line. It consists of small, nucleated, and rami- tied nerve cells. ^ The nucleus is the yellowish white substance filling the capsule ; and from it and the capsule issue transverse fibres, which unite the olivary bodies across the middle line (tig. 58, g) : this uniting band is close below the anterior median fissure. The fillet is a narrow band of fibres, which ascends from the olivary body to the cerebrum (fig. 57). It is formed in part by longitudinal fibres of tjie lateral tract which diverge to inclose the corpus olivare, and in part by fibres derived from the sac. The restiform body (fig. 54, is continuous inferiorly with the poste- rior column of the cord. Superiorly it bends outwards to the cerebellum without entering the pons. The posterior pyramid runs below into the posterior median column of the cord, and is directed above along the floor of the fourth ventricle, joining the fibres of the lateral tract of the same side. The decussation of the medulla oblongata (pyramids) (fig. 56, b) occu- pies the anterior groove of the oblong medulla, at the distance of three- quarters of an inch from the pons. It is about a quarter of an inch in length, and is constructed by the crossing of three or four bundles of fibres from eacli side. In this intercommunication the fibres are derived, according to Mr. Clarke, from all the constituent parts of the half of the spinal cord of the opposite side except from the anterior column ; but the fibres from the lateral column of that side, blended with otfsets from the contiguous gray substance, form the chief jiortion of the decussation. Arched or commissural fibres of the medulla. In each half of the me- dulla oblongata are fine transverse fibres, both on the exterior and in its substance. At the middle line the fibres of opj)Osite sides unite, and give rise to a commissure between the halves (raphe). The superficial transverse fibres (fig. 58, s, and fig. 54), more marked in some bodies, issue from the nucleus in the restiform body (Clarke), and advance over the surface of the olivary and pyramidal bodies to the ante- rior fissure, where they enter the half of the medulla of the same, and of the opposite side. Below the olivary body they form oftentimes a disti.ict band, the fihrce arciformes (fig. 54). The deep transverse fibres (fig. 58, h) are to be seen with the micro- scope on thin hardened transverse sections ; they begin behind in nuclei of the posterior pyramid and restiform body (Clarke), and penetrate be- tween the longitudinal fibres, and through tlie corpus olivare, as they reach forwards to enter tlie raphe in the middle line. The raphe (fig. 58, h and g), in which tlie arched fibres meet, occupies the middle line of the medulla above the decussation of the pyramids, and serves as the commissure between the halves of the medulla and the oli- vary bodies. Gray matter of the medulla oblongata. In the medulla oblongata there are the remains of the gray matter of tlie spinal cord ; and some special de|)Osits. Cross sections of the part when hardened would be required to see them. • Tlie arrangement of the fibres in the sac is most complicated, and a fuller account may be obtained by consulting Mr. Clarke’s Paper in the Philosophical Transactions for 1858. GRAY SUBSTANCE OF MEDULLA. 187 Remains of gray matter of the spinal cord. At the lower part of the medulla the central gray matter resembles that in the spinal cord (see fig. 126), but it undergoes the following changes d The posterior cornu in- creases in bulk, and extends towards the side of the cord, where it appears on the surface, in front of the restiform body, as the gray tubercle of Ro- lando (tuberculo cinero) (fig. 58, <). Higher in the medulla it becomes the chief nucleus of the sensory root of the fifth nerve. The piece of the gray commissure behind the central canal of the cord joins, above, the nucleus of the vagus nerve, and contributes to the audi- tory nucleus : and the piece in front of the canal is laid bare in the floor Transverse Section of the Medulla Oblonoata above the Middle of the Olivary Body (Cl: a. Anterior pyramid. b and c. Lateral column. d. Restiform body. e. Posterior pyramid. /. Corpus olivare with roots of the ninth nerve piercing it. g. Olivary commissure h. Deep transverse or commissural fibres of the medulla meeting in the raph6 (a few more are added in this cut from a second drawing). ,rke). k. Accessory olivary nucleus. l. Other gray deposits inside the olivary body. n. Floor of the fourth ventricle covered by epithelium. 0 . Nuclei of the ninth nerve. p. Nuclei of the vagus and glosso-pharyngeal nerves. r. Nucleus of the auditory nerve. s. Superficial transverse fibres. t. Remains of the gelatinous substance (tuber- culo cinereo). of the fourth ventricle by the inclination outwards of the restiform bodies ; it disappears above the fasciculi teretes. Special deposits of gray matter. Other masses of gray substances are deposited in the medulla, both in front and behind : those behind are near the floor of the fourth ventricle, and serve as nuclei of origin for certain nerves ; whilst those in front are interspersed amongst the fibres continued from the lateral columns of the cord. Nuclei at the back of the medulla. A nucleus for the hypoglossal nerve is deposited in front of the central canal, and extends upwards into the floor of the fourth ventricle close to the median sulcus (fig. 58, o). The nucleus of the accessory part of the spinal accessory nerve is placed opposite that of the hypoglossal, behind the central canal. The nucleus of the vagus begins on a level with the fourth ventricle ’ The description of the arrangement of the gray matter in the medulla oblon- gata is a summary of the facts contained in Mr. Clarke’s paper in the “ Transac- tions of the Royal Society for 1858.” 188 DISSECTION OF THE BRAIN. (fig. 58, p), and is continuous below with that of the accessory nerve. On the surface it forms a pyriform swelling along the inner side of the posterior pyramid, and limits laterally the calamus scriptorius. Above, this sinks under the auditory nucleus, and joins a nucleus for the glosso-pharyngeal nerve in a line with it. Above the last two nerves is another collection of cells serving as a nucleus for the auditory nerve. This projects on the lateral part of the medulla (fig. 58, r). At the front of the medulla. Outside the pyramid is the gray layer of the olivary body (fig. 58,/) already described (p. 185). Behind this is another separate, elongated, and flattened yellowish streak, the accessory olivary nucleus (fig. 43, ^•) ; while at the inner part of the olive, near the raphe., is a second collection (fig. 58, /), which is broken up into pieces. Both of the last de[)osits Mr. Clarke considers to be but parts of the cut folds of the corpus dentatum. PONS VAROLII. The PONS, or annular protuberance (pons Varolii, nodus encephali) (fig. 54), is situate above the medulla oblongata, and between the hemi- splieres of the cerebellum. In its natural position in the skull it lies below the opening in the tentorium cerebelli. It is nearly of a square shape, though it is rather widest from side to side, and measures two inches in the last direction. The anterior surface is grooved along the middle line, and is received into the basilar hollow in the base of the skull. By the opposite surface the pons forms part of the floor of the fourth ventricle. The upper border is longest and most curved, and arches over the cere- bral peduncles ; and the lower border overlays the medulla oblongata. On each side is the crus cerebelli, whose fibres radiate over the surface. Structure. In the pons are alternating strata of transverse and longi- tudinal fibres (fig. 56) : — The transverse set are continuous with the fibres of the crus cerebelli, much gray matter being interspersed: and the longi- tudinal are prolonged from the medulla oblongata. Dissection. The transverse superficial fibres of the pons being divided along the line of the pyramidal body of the right side (fig. 56), may be turned outwards so as to denude the longitudinal fibres (c) of the pyramid ; and this first set of longitudinal fibres, having been cut across already in tlie medulla oblongata, may be raised as far as the upper border of the pons. Beneath them will appear the second or deep set of transverse fibres of the pons (fig. 57,/). The deep transverse fibres may be cut through outside the ])yramidal (fig. 57); tlien the deep longitudinal fibres from the lateral column and the posterior pyramid (d) will appear. Amongst this last set of longitu- dinal fibres is the fillet of the corpus olivare, which the dissector should trace upwards from that body. Tlie superficial fibres of the pons can be seen on the side that is un- touched. The transverse fibres of the annular protuberance (fig. 56), are collected chiefly into two strata — a superficial and dee[), which are united in the middle line : they are commissural fibres of tlie cerebellum, and are de- rived from the crus or middle peduncle of that body. There are a few other transverse, which serve also as a commissure. CRURA OF THE CEREBRUM. 189 The superficia.1 set (fig. 56,/) are mostly horizontal, but some from the upper margin of the pons descend obliquely over the others. The deep layer (fig. 57,/) is thickened, and contains much gray matter between its fibres. The longitudinal jihres consist of two sets, viz., one from the anterior pyramidal body ; and another from the lateral tract and the posterior pyramid, to which a slip is added from the corpus olivare. The fibres are not continued simply through the pons, but are increased in number by the addition of others (peduncular) which, beginning in the upper two- thirds of the pons, join them on the outer side. The fibres of the anterior pyramid (fig. 56, c) pass through the pons between the two sets of transverse fibres, but not as one mass, for they are divided into a number of small bundles in their progress. Much in- creased in number, the fibres enter the crus cerebri at the upper border of the pons, and construct that fasciculated surface of the peduncle (c?), which is now uppermost. The fibres of the lateral column and posterior pyramid are altogether deeper than the transverse fibres of the pons (fig. 57, c?), and are mixed up with gray matter ; they are also more numerous than the preceding set. They project close to the middle line, in the floor of the fourth ven- tricle, and form the eminence of the fasciculus teres (fig. 55, ; from that spot they are continued upwards to the crus cerebri, of which they form the deeper or cerebral part (fig. 57, d). In the pons a band from the olivary fasciculus is added to these fibres. The olivary fasciculus (fillet, fig. 57) divides into two slips the pons. One passes backwards to the upper (in this position deeper) part of the crus cerebri, and ends in and beneath the corpora quadrigemina (p. 208). The other is continued to the crus cerebri with the fibres of the lateral column. Commissure o f the pons. At the back of the pons there is a commissure between the halves, opposite the deep longitudinal fibres. It consists, like that of the medulla oblongata, of fine anterior-posterior and trans- verse fibres. Section IV. DISSECTION OF THE CEREBRUM. The cerebrum, or the great brain, is the largest of the subdivisions of the encephalon, and weighs on an average 49 oz. in the male, and 44 oz. in the female. It fills the upper part of the cavity of the skull ; and its under surface would correspond with an oblique line on the head from the eyebrow to the articulation of the jaw ; and from this point to the occipi- tal protuberance. Taking the general form of the cranium, the cerebrum is convex on the upper aspect, and uneven on the lower. It consists of two hemispheres, which are placed side by side, and are partly separated by a median or longitudinal fissure. Across the middle line the halves are united by cer- tain interior parts (commissures), as well as by several connecting struc- tures at the under surface. Superiorly the surface of the hemisphere is 190 DISSECTION OF THE BRAIN. without any large cleft ; but inferiorly it is divided into two by a trans- verse fissure — that of Sylvius. Under Surface or Base of the Cerkbrum (fig. 59). At its under part the cerebrum is very irregular, in consequence of its fitting into in- ecjualities in the base of the skull ; and on this aspect the separation into hemispheres is not so complete as on the upper, for the median fissure exists only at the front and back. The following objects are to be recog- nized at the base of the brain along the middle line. Fig. 59. Under Surface of the Brain. b. Cersbellum. r. Teraporo-sphenoidal lobe of the cerebrum, p. Frontal lobe of the cerebrum : the great fis- sure between the two lobes, is the Sylvian, a. Medulla oblongata, d. PonsVarolii, /, Crus cerebri, g. Locus perforatus posticus. e. Corpus albicans. h. Tuber cinereum. i. Commissure of the optic nerves. l. Locus perforatus anticus. m. Lamina cinei-ea. n. Lower end (rostrum) of the corpus callosum in the great median fissure; the point in front where it bends is named genu. On each side of the lamina cinerea a narrow white band is continued from the end of the corpus callosum : this is the fillet of the corpus callosum. Immediately in front of the pons {d) are two large white masses, the peduncles of the cerebrum (crura cerebri, /’), one belonging to each hem- isphere ; and between is a space perforated by vessels, which is named locus perforatus posticus {cf). Outside the peduncle is the optic tract (f) ; and between it and the inner part of the hemisphere is a fissure leading into the lateral ventricle. In front of the peduncles are placed two white bodies like peas, the BASE OF THE BRAIN. 191 corpora albicantia {e) ; and anterior to these a grayish mass, called tuber cinereum (A). From the tuber cinereum a conical reddish tube, the in- fundibulum, descends to the pituitary body in the sella Turcica of the sphenoid bone. Anterior to the tuber cinereum are the converging optic tracts with their commissure (/). Beneath the commissure lies a thin grayish layer (lamina cinerea, in') ; and still further forwards is the great longitudinal tissure between the hemispheres, with the white corpus callosum (n) in the bottom of it. At the inner end of the transverse fissure (Sylvian) across the hemi- sphere, is another spot, perforated by vessels, and distinguished by the name substantia perforata, or locus perforatus anticus (/). Peduncle of the cerebrum (crus cerebri,/). This is a large, white, stalk-like piece, which reaches from the upper border of the pons to the under part of the cerebral hemisphere of the same side, near the inner margin. In the natural position the two peduncles fill the opening in the tentorium cerebelli. hhich is about three-quarters of an inch long, and widens as it approaches the cerebrum. Crossing its outer surface is the optic tract ; and between the crura of opposite sides is the interpeduncular space, which contains the locus perforatus, the corpora albicantia, and the tuber cinereum. Structure. The peduncle consists of longitudinal fibres, continuous with the longitudinal fibres of the pons, which inclose here a mass of gray mat- ter between them. Dissection. For the purpose of showing the structure of the crus, on the right side (fig. 57), the optic tract should be divided, and the fibres continuous witli tlie anterior pyramid of the medulla oblongata should be raised as far into the crus as the optic thalamus. In this proceeding the mass of gray matter (locus niger) will appear, and beneath it will be seen a second or deeper set of longitudinal fibres. The superficial fhres, whicli form the under or free part of the crus, are continued from the anterior pyramidal body (fig. 56, c). They are longitudinal in direction, and coarse in texture, and are directed u[)wards radiating to the cerebrum. The surface of the peduncle, which is com- posed of these fibres, is called i\ui fasciculated portion, or the crust. The deeper fibres are also prolonged to the cerebrum. They are derived chiefly from the lateral tract and posterior pyramid of the medulla oblon- gata, with a slip from the olivary fasciculus (fig. 57, d). Others come from the cerebellum, and mix with the former : some of these decussate across the middle line^ (p. 215). The fibres obtained from these four sources are situate beneath (as now seen) the gray matter : besides being deeper they ai'e finer than the superficial set, and inclose much gray sub- stance : the part of the crus formed by them is named tegmentum. The gray matter (locus niger) of the crus (fig. 57, y) forms a thin layer, whicli reaches nearer the inner than the outer margin of that body ; it is convex towards the free surface, but concave in the opposite direction. Tlie posterior perforated spot (pons Tarini, g) is situate between the peduncles of the cerebrum ; in the area of the space is a layer of grayish ' M. Foville describes a median commissure for the medulla oblongata, pons, and cerebral peduncles, which is composed of the interweaving of fibres of oppo- site sides. See the work of M. Foville, entitled : Traite complet de P Anatornie, du Sysibnie Nerveux cerebrospinal, p. 323, 1844. 192 DISSECTION OF THE BRAIN. mutter, and numerous vessels penetrate it. This structure forms the hinder part of the floor of the third ventricle. The corpora albicantia (corp. mamillaria, e) are two small, white bodies, about the size of peas, which are constructed in greater part by the crura of the fornix. If one, say the right, is cut across, it will be seen to contain gray matter. In front of them is the gray mass of the tuber cinereum. The median eminence of the tuber cinereum (Ji) forms part of the third ventricle, and is continuous with the gray substance in that cavity. In front of it are the optic tracts and commissure, and from its centre projects the following. Tlie infundibulum (funnel) is a conically-shaped tube which reaches from the tuber cinereum to the upper part of the posterior lobe of the pituitary body. It consists of a layer of gray matter, surrounded by the pia mater ; and it is lined by the ependyma of the third ventricle, as far as it is pervious. In the foetus this tube is open between the tliird ven- tricle and the pituitary body, but in the adult it is closed inferiorly. pituitary body will be very imperfectly seen when it has been dis- lodged from its resting-place : therefore it should be sometimes examined in the base of the skull by removing the surrounding bone. Its use is unknown. It is situate in the hollow (sella Turcica) on the sphenoid bone, and consists of two lobes, anterior and posterior. The anterior is the largest, and is hollowed out behind, where it receives the round posterior lobe. In the adult this body is solid, and firm in texture ; but in the foetus it is hol- low, and opens into the third ventricle through the infundibulum. Structure. It is firm aud reddish externally, but softer and yellowish internally. In it are nucleated cells, mixed with a granular semi-fluid substance; and the whole is contained in roundish spaces, which are con- structed by a stroma of areolar tissue with bloodvessels (Sharpey). Dissection. To see the lamina cinerea and the anterior termination of the corpus callosum, the hemispheres are to be gently separated from each other at the fore part. The lamina cinerea (^ni) is a thin concave layer of gray substance, which gradually tapers forwards from the tuber cinereum to the anterior termination of the corpus callosum. This stratum closes the anterior part of tlie third ventricle, and is continuous laterally with the anterior perfo- rated spot. In consequence of its great thinness, this structure is often broken through in removing the brain. Tlie corpus callosum (/«), bent in front, is continued horizontally back- wards in the longitudinal fissure to the lamina cinerea, and ends in two white narrow bands, the fillets or peduncles of the corpus callosum : each band is continued onwards by the side of the lamina cinerea to the anterior perforated spot. To the anterior bend of the corpus callosum the term knee (genu) is applied, and to the prolonged central part the appellation rostrum has been given. Laterally the corpus callosum reaches into the frontal lobe, and forms part of the floor of the lateral ventricle. Anterior perforated spot (substantia perforata antica, 1) is a space near the inner end of tlie fissure of Sylvius, which is situate between tlie frontal and ternporo-sphenoidal lobes of the cerebrum, and external to the optic tract. On the inner side it is continuous with the lamina cinerea; and crossing it, from within outwards, is the fillet of the corpus callosum. This space is gray on the surface; it corresponds with the corpus striatum FISSURES OF THE HEMISPHERES. 193 in the interior of the brain, and is perforated by numerous vessels for that body. Position of the part. Now the base of the cerebrum has been dissected, the brain should be turned over for the examination of the upper part. Something should then be placed beneath the front, in order that it may be raised to the same level as the back ; and a rolled-up cloth should loosely encircle the whole, to support the hemispheres. Upper Surface of the Cerebrum. On the upper surface the cere- brum, taken as a whole, is oval in form, and is convex in its outline, in acc^^rdance with the shape of the skull. A median longitudinal fissure divides the cerebrum incompletely into two halves. At the front and back the hemispheres are (piite separated by it; but at the middle and under parts they are united by connecting pieces, the largest of which is the white corpus callosum. In it the falx cerebri is lodged. Each hemisphere is larger in front than behind. Its outer surface is convex; but the inner is Hat, and in contact in tfont with the opposite half. On the upper aspect the surface of the hemisphere is divided by fissures into lobes, and on the under aspect it is cleft into two large pieces by the fissure of Sylvius. The superficies of the hemisphere is marked by tortuous eminences, the projections on it being named convolutions or gyri, and the intervening depressions, sulci or anfractuosities.^ Fissures of the Hemisphere. The larger fissures separate the lobes, and the smaller sulci mark the extent of particular convolutions. The fissures dividing the hemisphere into lobes are the three following: — The fissure of Sylvius (N, fig. CO) begins below at the anterior perfo- rated spot, and directed out between the frontal and temporo-sphenoidal lobes, divides into two parts, anterior and posterior. The anterior limb, ' S, ascends for a short distance into the frontal lobe. The posterior limb, the continuation of the fissure, is directed obliquely upwards and backwards to about the middle of the outer face of the hemi- sphere. At its extremity it is sometimes divided into smaller sulci. Fissure of Rolando (i?, fig. GO). Beginning above, about half way along the hemisphere, in or near the longitudinal fissure of the cerebrum, it is prolonged outwards between the frontal and parietal lobes nearly to the posterior part of the Sylvian fissure, — about the middle of that limb. The external parietO'-occipital fissure (opposite P 0, fig. 60) begins in the median longitudinal fissure half way between the preceding and the hinder end of the hemisi)here. It is very variable in extent, being some- times an inch long, and at others only a slight indentation ; but it may be always recognized by its continuity with the perpendicular fissure on the inner face of the hemisphere (fig. 62). Lobes of the Hemisphere. Each hemisphere is divided into five lobes, which have the following names and limits : — The frofital lobe (Fr, fig. 60) forms the anterior half of the hemis[)here. It is limited below by the fissure of Sylvius, S, and behind by the fissure * In the following description of the surface anatomy of the cerebrum I have followed chiefly the arrangement of Professor Turner in his paper “Ox the Con- voLUTioxs OF THE HuMAx CEREBRUM and to hiiii I am indebted for permission to copy the wood-cuts employed in illustration of his publication. 13 194 DISSECTION OF THE BRAIN. of Eolando,^ R. Its under part, w hich rests on the orbital plate, has been called tlie orbital lobule. The parietal lobe {Par, fig. GO) is placed behind the preceding, and reaches down to the Sylvian fissure. It is about half as long as the fron- tal. In front it is bounded by the fissure of Eolando, R, and behind by the parieto-occipital {P 0). The upper and hinder part, close to the median fissure, is named the parietal lobule (o'). Fig. 60. Lobes of the Hemisphere, and Convolutions and Fissures of the Outer Surface. Fr. Frontal lobe. Par. Parietal lobe. Oc. Occipital lobe. T S. Teinporo-sphenoidal lobe. R. Fissure of Rolando. S. Posterior. 'S, Ascending limb of the Sylvian fissure. P 0. Place of the external parieto-occipital fissiye which is not visible in a side view. I P. Intra-parietal sulcus. P. Parallel sulcus — 1, inferior ; 2, middle ; aud 3, superior frontal gyrus; 4, ascending frontal ; and 5, ascending parietal gyrus ; 5', parietal lobule ; 6, angular gyrus ; 7, superior ; 8, middle ; and 9, inferior temporc-sphenoidal gyrus ; 10, superior ; 11, middle ; and 12, inferior occipital convolution. A. Supra-marginal convolution — a, first ; second ; c, third ; and d, fourth, annectant gyrus. The occipital lobe {Oc, fig. GO) constitutes the pointed end of the hemi- sphere, and measures about a fifth of tlie wdiole. In front it is separated from the parietal lobe by the parieto-occi[)ital fissure {P 0), but below^ it blends with the following lobe. It rests on the tentorium. On the inner surface is a triangular piece, the occipital lobule fig. G2). The temporo-sphe^ioidal lobe {T S, fig. GO) projects into the middle fossa of the base of the skull. It is situate behind the fissure of Sylvius, and below' the parietal and occipital lobes. The outer surface is in contact w'ith tlie cranium, and the opposite is supported mainly on the tentorium. The central lobe or the island of Eeil {C, fig. Gl) lies in the sylvian fis- sure, and is concealed by the overlapping of tlie frontal and temporo-sphe- r.oidal lobes. On separating those lobes it will be seen to be bounded in 1 By some the anterior limb of the fissure 'S is made the hinder bound of the lobe ; but this is not so good an arrangement as that in the text. OUTER CEREBRAL CONVOLUTIONS. 195 front and beliind by tlie limbs of the Sylvian fissure, and externally by a deep groove separating it from the frontal and parietal lobes. It is of a triangular form with the apex down. Convolutions of the Cerebrum. In different brains the convolu- tions vary slightly in form, and even in the two hemispheres of the same cerebrum they are not exactly alike : but there is always similarity enough for the recognition of tlie chief eminences. Each lobe possesses convolutions, but tliese run into each other by means of smaller gyri, either on the surface of the brain or at the bottom of the sulci ; and the student may experience some difficulty at first in defining the limits of each. It is in tlie smaller gyri that the greatest variation will be found. A. Convolutions of the Outer Surface. About the middle of the hemis[)here are two straight vertical convolutions, one on each side of the fissure of Kolando, which will vServe as a starting jioint. In front of those two the convolutions are longitudinal ; and behind they take an oblique direction to the back of the brain. a. The frontal convolutions (fig. 60) form two sets, one on the outer, the other on the under surface of the frontal lobe : those on the outer aspect are four, viz., one vertical or posterior, and three longitudinal or anterior, as follows : — The ascending frontal (*) is the vertical, straight convolution, which bounds in front the Rolando fissure. It reaches down from the median to the sylvian fissure (posterior limb). Along the anterior border it is joined by the three frontal convolutions ; and below it unites with the most ante- rior convolution of the parietal lobe round the lower end of the fissure of Rolando, R. The three longitudinal frontal convolutions are much subdivided and blended, and are separated by two intervening sulci. They are named superior (®), middle (‘^), and inferior (^) : they communicate behind by secondary gyri with the ascending frontal (^), the highest having often two processes ; and are directed forwards one outside another to the anterior extremity of the hemisphere. The under or orbital surface of the frontal lobe, concave, is represented in fig. 01. Near the inner margin is a sulcus, the olfactory, lodging the olfactory nerve ; and internal to it is the lower end of the mai-ginal convo- lution ('7). External to the sulcus lies a convolution, which is pointed behind, but widened and subdivided in front, and incloses smaller gyri and sulci within its coil: this has been subdivided into three parts, an inner C'^), a posterior (^),and an external (®). h. parietal convolutions (fig. 60), like the outer frontal, are four in number ; an anterior, or ascending, which is vertical along the fissure of Rolando, and three directed back from it. The ascending parietal (“), narrow and straight, limits behind the fissure of Rolando, and reaches from the middle line to the hinder limb of the vSylvian fissure, S. Above, it runs into the parietal lobule,^' ; and below, it joins the ascending frontal round the lower end of the fissure of Rolando. Behind it is separated from the other gyri of the parietal lobe by a saclus, IP} The parietal lobule {f) appears to be an appendage to the upper end of 1 Tlie intraparietal sulcus (I P, fig. 60, Turner), is placed between the ascending parietal and the supra-marginal convolution, A. Above, it is directed back near the upper part of the hemisphere, separating the parietal lobule (5') and the supra-marginal convolution, A. 196 DISSECTION OF THE BRAIN. the ascending convolution, and is continued back along the upper margin of the hemisphere as far as tlie parieto-occipital fissure. Subdivided on the surface into two chief parts it is joined beliind to the occipital lobe by the small annectant gyrus {a). To its outer side lies the upper part of the intraparietal sulcus ; and here it joins usually the following convolution, A. The supra-marginal convolution lying outside and below the preced- ing, is interposed between the intraparietal sulcus, I P, and the Sylvian fissure (outer end). Variable in shape it joins, below, the ascending parietal convolution (^) ; it may communicate above with the parietal lobule, and behind with the following. The angular convolution (®), very complicated and not well defined, is placed at the extremity of the hinder limb of the Sylvian fissure, and is composed of two or three pieces Above it is the parietal lobule ; and below, the temporo-sphenoidal lobe which it joins. In front lies the supra-marginal convolution ; and behind, the occipital lobe, with which it blends by the small annect- ant gyrus (6). c. The occipital convolutions (fig. 60) are small and very mucli di- vided, so that their outline is un- certain. They are three in number, lying one above another, and sepa- rated by sulci, something like the frontal gyri at the opposite end of the hemisphere. The upper (^°), forming part of the margin of the longitudinal fis- sure, receives an annectant gyrus from the parietal lobule. The middle ("), crossing out- wards the hemisphere, has two an- nectant gyri to other convolutions ; one (b) joining it above to the an- gular convolution, and another (c) passing to the middle temporo- sphenoidal convolution. The inferior (’‘^j occupies the tip of the hemisphere between the up- per and under surfaces. At the inner end it is continuous with the upper gyrus ; and at the outer end with the inferior temporo-S})henoi- dal convolution (®) by an annectant gyrus (d). d. The temporo-sphenoidal convolutions (fig. 60), three in number, run from above down, and are separated from one another by two sulci. The superior (^) bounds posteriorly the horizontal limb of the Sylvian fissure. At the upper end it is connected by a gyrus with the angular convolution. The middle (®) is separated from the first by the parallel sulcus {P). Fig. 61. View of the Orbital Lobule and thb Central Lobe. C. Island of Reil or median lobe. 0 . Olfactory sulcus. 2. Internal ; and 6. External orbital convolution, posterior ; 17. Marginal convolution of the hemisphere. INNER CEREBRAL CONVOLUTIONS. 197 Above, it blends commonly with the angular convolution, and is connected to the middle occipital convolution by an annectant gyrus (c). Tlie inferior (*’), less well marked than the other two, l^orms part also of the inner surface of the temporo-sphenoidal lobe, lly the upper end it is united to the third occipital convolution by an annectant gyrus (d). The parallel sulcus (P, fig. GO), named from its position to the Sylvian fissure, extends from the lower end of the temporo-sphenoidal lobe to the angular convolution. e. The convolutions of the central lobe ( (7, fig. Gl), about six in number, are straight for the most part, and are separated by shallow sulci : they are directed upwards from apex to base of the lobe. The posterior gyri are the longest and broadest, and the anterior joins the convolution of the under surface of the orbital lobule. *B. The CONVOLUTIONS ON THE INNER SURFACE of the hemisphere (fig. G2) are generally well defined ; but some being so long as to reach beyond the extent of a lobe, the arrangement of them in lobes cannot be followed, as on the exterior. Di ssection. Without the use of a separate hardened hemisphere, the parts now to be described will not be seen satisfactorily. If the student possesses only one brain, he may bring into view much of the inner sur- face by cutting of the left hemisphere as low as the white corpus callosum in the median fissure. Convolution of the corpus callosum^ gyrus fornicatus (^®), is long and simple, and arches round tlie body from which it takes its name. Begin- ning at the base of the brain in the anterior perforated spot, it bends backwards in contact with the corpus callosum i^Gal)^ and below the back of that body blends by a narrowed part with the uncinate convolution (^®) of the temporo-sphenoidal lobe. Anteriorly a sulcus separates it from the following convolution ; and smaller gyri often connect the two across that sulcus. The marginal convolution (’'^) is named from its position on the edge of the median fissure. Its extent is rather more than half the length of the liemisphere, for it begins in front at the anterior perforated spot, and ter- minates near the back of the corpus callosum, just behind the fissure of Rolando. It is much subdivided both internally and externally; and on the under part of the frontal lobe (fig. Gl) it lies internal to tlie olfactory sulcus. Between it and the preceding convolution is situate the calloso- marginal sulcus {%) which marks its hinder limit. The calloso-marginal sulcus (f, Huxley), designated from its situation, begins in front below the corpus callosum, and ends behind, near the back of the same body, by ascending to the edge of the hemisphere. Smaller gyri uniting the two bounding convolutions, frequently interrupt it, and secondary sulci are prolonged from it into the same convolutions. The quadrilateral lohide (^®) reaches Ifom the marginal convolution in front to the parieto-occipital fissure behind. It is much divided by sulci, and projects above to the edge of the hemisphere ; it joins below the gyrus fornicatus. The occipitat lobule is triangular in shape, with the base upwards, at the margin of the hemisjihere. Measuring about an inch and a half in depth, it lies between the internal parieto-occipital fissure, PO, and the calcarine sulcus (/). Sulci running from apex to base divide it into four or five narrow convolutions. 198 DISSECTION OF THE BRAIN. Internal 'perpendicular or parieto-occipital Jissure (PO, fig. 62) sepa- rates the two preceding lobules. Continuous with the external fissure of the same name, it opens below into the following. The calcarine sulcus /, (Huxley) is directed across the back of the hemisphere below the level of the corpus callosum, and ends in front at the gyrus fornicatus ('®), whose hinder limit it marks. It receives above Fig. 62. Convolutions and Fissures on the Inner Face of the Hemisphere. P. 0. Internal parieto-occipital fissure. Cal. Corpus callosum, cut. i. Calloso-marginal sulcus. l. Calcarine sulcus. m. Dentate sulcus. n. Collateral sulcus. 17. Marginal gyrus. IS. Convolution of corpus callosum. 18'. Quadrilateral lobule, 19. Uncinate gyrus. 19'. Crotchet or hook of the uncinate gyrus. 25. Occipital lobule. 9. Inferior temporo-sphenoidal gyrus partly seen. the internal perpendicular fissure; and it sinks into the posterior cornu of the lateral ventricle, forming the eminence of the hippocampus minor. Internal temporo-sphenoidal convolutions (fig. 62) are two in number, viz., the uncinate and dentate, and occupy the tentorial surface of the hemisphere. Tlie uncinate or hippocampal convolution (^®) is prolonged from the posterior end of the hemisphere nearly to the tip of the temporo-sphenoidal lobe. It is somewhat narrowed in the middle, where the gyrus fornicatus blends with it ; and is enlarged at each end, especially at the posterior where it is subdivided by sulci. Below it is a long curved sulcus, the collateral (w) ; and above it are the calcarine (/), and the dentate suB cus(/«). From the anterior extremity a narrow part (^^', uncus) is pro- longed back for half an inch on the inner side, like a hook. Below the uncinate convolution is part of the inferior tem})oro-sphe- noidal convolution (®), before described, which forms the lower edge of the temporo-Sjdienoidal lobe, appearing more largely on the inner than on the outer face. The collateral sulcus 7^, (Huxley) courses along the lower border of the uncinate convolution ; it projects into the inferior cornu of tfie lateral ventricle, and gives rise to the prominence of the eminentia collateralis. Secondary sulci emanate from it, and it is often interrupted by cross gjri. The dentate sulcus ???, (Huxley) is the deep groove at the upper edge of the uncinate convolution (’^), and corresponds with the prominence of the CORPUS CALLOSUM. 199 hippocampus major in the descending cornu of the lateral ventricle. Upwards it is limited by the corpus callosum {Cal) and downwards it intervenes between the hook and the body of the uncinate convolution. In the dentate sulcus is the gray substance of the hemisphere, which presents a notched border at the inner edge of the temporo-s[)henoidal lobe ; this has been called the dentate convolution^ and will be better seen in a subsequent stage of the dissection of the brain. Structure of the convolutions. Each convolution is continuous witli the interior of the brain on the one side (base) ; and is free on tlie surface of tlie brain on the other side, where it presents a summit and lateral parts. On a cross section it will be seen to consist externally of gray cerebral substance as a cortical layer, which is continued from one eminence to another over the surface of the hemisphere ; and internally it is composed of wliite brain substance — the medullary part, which is derived from the fibrous mass in the interior. The cortical layer is composed of two, or in some parts of tliree strata, which are separated by their intervening paler layers; and an outer wliite stratum, which covers the surface, is most marked over tlie internal and lower portions of the uncinate convolution. Interior of the Cerebrum. The cerebrum consists on each side of a dilated part or hemis[)here, and of a stalk or peduncle. In tlie interior is a large central space, which is subdivided into smaller hollows or ven- tricles by the before-mentioned connecting pieces. And the whole, except the peduncle, is surrounded by a convoluted crust. In conducting the dissection of the cerebrum, the student will learn the form and situation of the several constituent parts, and the connections between these by means of fibres. Dissection. Supposing both hemispheres entire, the left is to be cut off to the level of the convolution of the corpus callosum. When this has been done, the surface disjdays a white central mass of an oval shape (centrum ovale minus), which sends processes into the several convolu- tions. In a fresh brain this surface would be studded with drops of blood escaping fi'om the divided vessels. Next, the convolution of the corpus callosum is to be divided about the middle, and the two pieces are to be thrown backwards and forwards. Under it lies a thin narrow band, the covered band of Reil, which bends down before and behind the corpus callosum. The same steps of the dissection are to be taken on the opposite side ; and the tops of the hemispheres being removed to the level of the corpus callosum, the transverse fibres of that body are to be defined as they radi- ate to the convolutions. Now a much larger white surface comes into view (larger ovan centre), which has been named centrum ovale, Vieussens ; and the white mass in each hemisphere is seen to be continuous, across the middle line, through the corpus callosum. The corpus callosum reaches from the one-half of tlie cerebrum to the other, and forms the roof of a space (lateral ventricle) in each hemisphere. Between the halves of the brain, where it occupies the longitudinal fissure, it is of small extent, being about four inches in length, and somewliat arched from before backwards. It is narrower in front than behind, and extends nearer to the anterior than the posterior part of the cerebrum. In front the corpus callosum is bent to the base of the brain (fig. 59, ??.), as before described (p. 192); and behind it ends in a thick roll, which is connected with the subjacent fornix. 200 DISSECTION OF THE BRAIN. On the upper 'surface the fibres are directed from the hemispheres to tlie middle line — the middle being transverse, but those from the anterior and posterior })arts oblique. Along the centre is a ridge or raphe, and close to it are two or more slight longitudinal white lines (nerv'es of Lancisi). Still further out may be seen other longitudinal lines (covered band), beneath the convolution of the corpus callosum, if all of them have not been taken away in the removal of that convolution. The longitudinal fibres in the middle line are continued downwards in front, and joining the covered band or fillet are continued to the anterior per- forated spot. Dissection. In order to see the thickness of the corpus callosum, and to bring into view the parts in contact with its under surface, a cut is to l)e made through it on the right side about half an inch from the central ridge : and this is to be extended forwards and backwards, as far as the limits of the underlying ventricle. Whilst cutting through the corpus callo- sum, the student may observe that a thin membraniform structure lines its under suiface. The corpus callosum is thicker at each end than at the centre, in con- sec juence of a greater number of fibres being collected from the cerebrum ; and the posterior part is the thickest of all. Connected with its under surface along the middle is the septum lucidum or partition between the ventricles (fig. 63, ^), and still posterior to that is the fornix. This body is the chief commissural part of the halves of the brain, and reaches laterally even to the convolutions, but its fibres are not distinct far in the hemisphere. Dissection. The left lateral ventricle is to be now opened in the same way as the right \ and to {)repai‘e for the examination of the cavity on the right side, as much of the cor[)us callosum as forms the roof of the space is to be removed. A part of the ventricle extends down in the temporo- sphenoidal lobe towards the bjise of the brain ; and to open it, a cut is to be carried outwards and downwards, through the substance of the hemi- sphere, along the course of the hollow. (See fig. 63.) Ventricles of the brain The ventricular spaces in the interior of the cerebrum are derived f]*om the subdivision of a large central hollow, and are five in number. One (lateral) is contained in each hemisphere ; and these constitute the first and second. The third occupies the middle line of the brain near the under surface ; and the small fifth is included in the partition between the lateral ventricles. The fourth is situate be- tween the cerebellum and the posterior surface of the medulla oblongata and pons. The lateral ventricles (fig. 63) are two in number, one in each hemi- sphere ; they are separated incom^detely in the middle line by a septum, as they communicate by an aperture below that partition. The interior is lined by a thin stratum of areolar tissue covered by nucleated epithelium (the ependyma ventriculorum), with cilia at some spots. Each is a narrow interval, which reaches into the anterior, posterior, and middle regions of the corresponding hemisi)here. Its central part (body) is almost straight, but the extremities (cornua) are curved. Thus there are three cornua in each, which have the following disposition : — The anterior is directed outwards from its fellow in the otlier hemisphere. The posterior or the digital cavity is much smaller in size, and is bent inwards in the occipital lobe towards the one on the ojqiosite side. And the inferior coniu, beginning opposite the posterior fold of the corpus cal- BOUNDS OF LATERAL VENTRICLE. 201 losum (a), descends in a curved direction in the temporo-sphenoidal lobe, with the concavity of the bend turned inwards. For the purpose of examining its boundaries, the ventricle may be di- vided into an upper or horizontal, and a lower or descending part. The upper or horizontal portion reaches from the trontal to the occipital lobe, and is shaped like the italic letter _/! View of the Lateral Ventricles: on the left side the Descending Cornu is laid OPEN. (From a cast ia a museum of University College, Londou.) a. Remains of the corpus callosum. h. Septum lucidum, inclosing the small space of the fifth ventricle. c. Fornix. d. Posterior crus or taenia of the fornix. e. Corpus striatum. /. Taenia semicircularis. g. Optic thalamus. h. Choroid plexus. i Hippocampus minor, fc. Eminentia collateralis. 1. Hippocampus major, o. Digital fossa. The roof is formed by the corpus callosum. The floor is irregular in outline, and presents from before backwards the following objects : — first, a small piece of the under part of the corpus cal'osum ; next, a large, gray body, the corpus striatum (e) ; behind tliis, the large white projection, named optic thalamus {(j') ; and between the two last bodies is a white band ( /’), ta3nia semicircularis. On the surface of the optic thalamus is a vascular fold of tlie pia mater {li ) — the plexus choroides, together witli the thin wliite half of the fornix (e). Close behind the thalamus is tlie beginning of a projection (hippocampus major) (e), in the floor of tlie de- scending part of the lateral ventricle ; and in the posterior cornu is an elongated eminence, the hippocampus minor (?'). 202 DISSECTION OF THE BRAIN. The inner boundary (septum ventricnlornm) is a thin layer which is sometimes named se{)tnm liicidnm (fig. G3, h). Its extent corresponds with tlie central part of the corj)us callosum. Below it and the fornix, opposite the front of the optic thalamus, is the aperture of communication (foramen of Monro) between the two lateral ventricles. The lower or descending part of the ventricle winds beneath the optic thalamus, and forms a curve like the half-bent forefinger. The roof is formed by tlie optic thalamus and tlie contiguous part of the hemisphere. In the floor is a large curved, convex eminence, somewhat indented at tlie end — the liippocampus major (/) ; and along its concave margin is a thin white band — tmnia (d)^ which is prolonged from the fornix. Ex- ternal to the projection of the hippocampus is another white eminence, the eminentia collateralis (^’), which tapers from above down. In this part of the ventricle is the vascular fringe of the ple:^us choroides. The spptum. lacidum (fig. G3, h), or the thin structure between the lateral ventricles, is translucent, and hangs vertically in the middle line along the anterior two-thirds of the corpus callosum. It is somewhat triangular in form, with the larger part turned forwards, and the pointed extremity backwards. Its surfaces look to the lateral ventricles. The U])per border is attached altogether to the under surface of the corpus cal- losum ; and the lower border is joined in part to the fornix (c), but in front of that body it is inserted into the under or prolonged portion (rostrum) of the corpus callosum. The septum consists of two layers, which inclose a space — the fifth ventricle ; and each layer is formed of white subsfance, with an external coating of gray matter. Dissection. The space of the fifth ventricle will come into view by cutting through the part of the corjms callosum which remains in the middle line, and by detaching the anterior half from the septum lucidum, and raising it. (See fig. G3.) The ventricle of the septum., or the fifth ventricle, is a triangular space in the fore part of the ventricular partition, where the depth is greatest. Like the septum containing it, its largest part is in front. Its surface has an epithelial covering like that in the lateral ventricles. In the adult it is closed ; but in the foetus it opens inf'eriorly into the third ventricle be- tween the pillars of the fornix. Dissection. The fornix is to be next examined. To lay bare this body the posterior part of the corpus callosum should be detached with care from it, and thrown backwards ; and the septum lucidum should also be removed from its upper surface. The fornix, or arch (fig. G3, c), is a thin white horizontal stratum be- neath tlie corpus callosum, which, projecting on each side into the lateral ventricle, forms ^lart of the floor of that cavity. Its central part or body is triangular in shape, with the base turned backwards ; and it is continu- ous with the rest of the brain by processes or crura before or behind. To the upper surface of the body, along the middle line, the septum lucidum is attached. Each border is free in the corresponding lateral ventricle, where it rests on the optic thalamus ; and along it lies the cho- roid plexus. At its posterior part it joins the corpus callosum in the middle line, whilst on each side it sends off a small riband-like band — tamia hiiipocampi (d), along the concave margin of the hippocampus major. At the anterior part it is arched over the foramen of Monro, opposite the front of the optic thalamus, and ends likewise in two pro- FLOOR OF LATERAL VENTRICLE. 203 cesses or crnra, which will be afterwards followed to the corpora albicantia and the optic thalami (p. 208). If the forrnix be cut across near its front, the foramen of Monro will be opened, and the descending anterior pillars will be seen (fig. G4). When the posterior part is raised, it will be found to be supported on a process of the pia mater, named velum interpositum. And near its base (on the under aspect) between the two offsets of the taeniae hi[)pocampi, is a trian- gular sui-face, which is marked by transverse lines : the part which is so defined has been called the lyra (fig. G4). The fornix may be described as consisting of two bands, right and left, which are united for a certain distance in the central part or body. Ac- cording to this view each band, commencing in the optic tlialamus, passes over the foramen of Monro, and after forming the body of the fornix, is continued as a distinct piece to the uncinate convolution. The foramen of Monro is the interval beneath the anterior part of the fornix, which opens on each side by a slit between the edge of the fornix and the optic thalamus. In it the plexus choroides lies; and through it the lateral ventricles communicate with one another and with tlie third ventricle. Floor of the Lateral Ventricle The student may leave un- touched, for the present, the • membrane on which the fornix rests; and proceed to examine, on the right side, the different bodies which have been enumerated as constituting the door of the lateral ventricle. The corpus striatum (superior ganglion of the cerebrum) (fig. G3, e) is the large gray body in the front of the lateral ventricle. It is placed op- posite the island of Reil in the fissure of Sylvius; and it has received its name from the striated appearance of a vertical section. Dissection. To see the composition of the corpus striatum, the student should slice off obliquely the upper and outer part until certain white fibres crossing it obliquely from within outwards are reached. The knife should then be carried through this layer of white fibres until another mass of gray substance, similar to the first, is arrived at. The striate body is a jiyriform mass of gray matter of considerable thickness, which is surrounded by the white substance of the hemisphere, except where it projects into tlie lateral ventricle. Its position is oblique with respect to the middle line of the brain, for the anterior part is near the septum of the ventricles, whilst the posterior is external to the optic thalamus. By means of the incision in the corpus striatum, white fibres can be seen to be directed through it in such a way as to divide the gray matter into two parts, one being situate in the ventricle (intra-ventricular) above the white fibres, and the other outside the ventricular space (extra- ventricular), below these fibres. The intra-ventricular jiiece (nucleus caudatus) is shaped like a kite, and projects into the floor of the ventricle. The end, directed forwards, is large and rounded; whilst the opposite end is tliin and pointed, and is continued backwards, outside the optic thalamus, to the roof of the de- scending cornu of the lateral ventricle. Numerous veins cover this part of the corpus striatum. The extra-ventricular part (nucleus lenticularis) will be better seen, afterwards, by sections made from the outer side or from below. It is oval in form, but does not reach so far back as the other, and is bounded inferiorly by a white capsule ; through it the anterior commissure of the brain passes very obliquely, as a subsequent dissection will show. 204 DISSECTION OF THE BRAIN. The tcenia semicircnlaris (fig. 63, /) is a thin and narrow wliite band of longitudinal fibres, which lies between the corpus striatum and the optic thalamus. In front this band becomes broader and joins the pillar of the fornix; and behind it is continued, along with the pointed end of the cor- pus striatum, into the white substance of the roof of the descending cornu of the lateral ventricle. Superficial to the anterior part of the tainia is a yellowish semi-transparent layer (lamina cornea) ; and beneath this pass some small veins from the corpus striatum, in their course to the veins of Galen. The optic thalamus is only partly laid bare in this stage of the dissec- tion, and its examination may be omitted till the third ventricle has been learnt. The hippocampus minor (calcar avis) resembles a cock’s spur (fig. 63, f), as it lies in the posterior cornu of the ventricle. It is })ointed at its posterior extremity, and is covered on the free surface by a medullary layer continuous with the corpus callosum. When it is cut across a gray stratum will be found beneath the white; and the eminence itself will be seen to be produced by the extension inwards of the calcarine sulcus at the inner surface of the hemisphere (p. 198). The hippocampus major (fig. 63, 1) is the curved projection in the floor of the descending cornu of the lateral ventricle. Convex on the surface that looks to the cavity, this body is curved in the same direction as the cornu, and has its concavity turned inwards. The anterior ex- tremity is the largest, and presents two or three indentations, which give it the appearance of the foot of a feline animal; it is named pes hippo- cam])i. All along the inner or concave margin is the small band or tsenia {d) that is prolonged from the fornix; it ends below by joining the small recurved part of the uncinate convolution. Dissection. To examine more fully the hippocampus, the parts of the corpus callosum and fornix, which remain in the middle line, should be divided longitudinally, and the posterior part of the right hemisphere should be drawn away from the rest of the brain. When the pia mater has been removed from the inner side of the hippocampus, and this pro- jection has been cut across, its structure will be manifest. The hippocampus is covered on the ventricular surface by a medullary layer, with which the taenia or the band of the fornix blends. On its opposite surface is the hollow of the dentate sulcus on the exterior of the brain, which is filled with gray substance. Along the free margin of the hippocampus the gray matter [)rojects in the form of a notched ridge, the lamina dentata: this is external to the cavity of the ventricle, beneath the taenia, and has been named the dentate convolution (p. 199). Transverse Jiss?ire of the cerebrum. By drawing the separated right hemisphere away from the crus cerebri and the optic thalamus, and re- placing it, the dissector will comprehend the position, and the boundaries of the great cleft at the posterior ])art of the brain. This fissure lies beneath the fornix, and opens into the lateral ventricle, on each side, along the edge of the fornix, from the foramen of Monro to the extremity of the descending cornu. The part of the slit entering the latenil ventricle is bounded by the edge of the fornix on the one side, and by the 0 })tic thalamus and crus cerebri on the other. A piece of pia mater projects into the transverse fissure, forming a horizontal central piece, velum interpositum, beneath the fornix (fig. 64, ®), and thinner lateral VELUM INTERPOSITUM. 205 pieces with terminal fringes in tlie latter ventricles (/). But the slit tlirough which the membrane enters the ventricle is closed by the lining structure of that cavity being continued on the intruded part. Second View of the Dissection of the Brain, the Fornix being Cut through IN Front and Raised. (From a cast in the University College, Loudon.) 05 . Fornix. d. Corpus striatum. b. Hippocampus major. e. Optic thalamus. c. Tsenia hippocampi, or hinder crus of /. Choroid plexus. the fornix. g. Velum interpositum. Parts in the Middle Line of Cerebrum. The student is now to return to the examination of the parts in the centre ot‘ the brain, viz., the fold of pia mater and its vessels, with the third ventricle. At the same time the optic thalamus is to be seen. The velum interpositum (fig. fi4, g) is the central part of the fold of pia mater entering the great transverse fissure. Triangular in sliape, it has the same extent as the body of the fornix, and reaches in front to the foramen of Monro. The upper surface is in contact with the fornix, to which it supplies vessels. And tlie lower surface, looking to the third ventricle, covers the pineal body, and a part of each optic thalamus : un- derneath it in the middle line are the two choroid plexuses of the third ven- tricle. Along each side is another vascular roll of the membrane (choroid plexus). The choroid plexus of the lateral ventricle (fig. 64,/) is the red, some- what rounded, and fringed margin of the piece of pia mater in the inte- rior of the lateral ventricle, which extends from the foramen of Monro to 206 DISSECTION OF THE BRAIN. the extremity of the descending cornu. Its lower end is larger than the upper. On its surface the choroid plexus is villous ; and the villi, minutely subdivided, are covered by flattened nucleated epithelium, with the fat granules and pigment in the cells. ^ Vessels of the velum. Small arteries have been already traced to the velum and the choroid plexus from the cerebral and cerebellar arteries (p. 175): they are three on each side, and supply the surrounding cerebral substance. The veins of the choroid plexus receive branches from the ventricle, and end in the following. Veins of Galen. Along the centre of the velum are placed two large veins with this name ; they begin at the foramen of Monro, by the union of branches from the cor[)us striatum and the choroid plexus. Lying side by side in the membrane tliey are usually united into one at the posterior part of the velum ; and by this tliey join the straight sinus. Dissection. When the velum interpositum has been raised and thrown backwards, the third ventricle will be visible (fig. 68). In reflecting the piece of pia mater the student must be careful behind of the pineal body (y), whicli would otherwise be detached, as it is surrounded by the mem- brane. On the under surface of the velum are the choroid plexuses of the third ventricle. The choroid plexuses of the third ventricle are two short and narrow fringed bodies beneath the velum, which resemble the like parts in the lateral ventricle. The third ventricle is in the interval between the optic thalami (fig. 68). Its situation is in the middle line of the cerebrum, below the level of the other ventricles with which it communicates ; and it reaches to the base of the brain. Its boundaries and communications are the follow- ing , The roof is formed by the velum interpositum and the fornix. The floor is very oblique from behind forwards, so that the depth of the cavity is about an inch in front and half an inch behind : it corresponds with the t)arts at the base of the. brain, which lie between the crura cerebri and the median fissure (fig. 59), viz., locus perforatus, corpora albicantia, tuber cinereum, commissure of the optic nerves, and lamina cinerea. On the sides of the cavity are situate the optic thalami (5). In front of the space are the descending pillars of the fornix, with the anterior commissure of tlie cerebrum (c) in the interval between them. Behind are the posterior commissure (e) and the pim.'al body (y). Crossing the centre of the ven- tricle, from one optic thalamus to another, is a band of gray matter — the soft commissure (c?). This space communicates with the other ventricles of the brain in the following way: — In front it joins each lateral ventricle through the fora- men of Monro ; and in the foetus it opens into the fifth ventricle. Behind is a passage beneath the posterior commissure into the fourth ventricle, which is named aqueduct of Sylvius. At the lower part, in front, there is a depression opposite the infundibulum (iter ad infundibulum). The lining of the ventricle (ependyma) is continued into the neighbor- ing cavities tlirough the different apertures of communication, and closes the iter ad infundibulum. Gray matter of the ventricle. A stratum of gray matter covers most of the surface of the ventricle. At the lower part of each optic thalamus • Particles of brain sand, like that in the pineal body, are sometimes present in the choroid plexus. THIRD VENTRICLE. 207 it envelops the crus of the fornix, and ascends to the septum luciduin ; and in tlie floor of the cavity it exists in abundance, entering into the corpora albicantia. In the middle of the space it reaches from side to side, and forms the soft commissure {d). The anterior commissure of the cerebrum (e) is a round bundle of white fibres about as large as a crow-quill, wliich passes through both corpoi-a striata, and connects the opposite hemispheres. To see it in one-half of its extent, the following dissection should be made : — Dissection. On the side on which the corpus striatum has been cut into, the commissure is to be followed into the interior of that body, by scra])ing away the intraventricular gray matter with the handle of the scalpel. The commissure may be seen then to perforate below the white fibres of the corpus striatum ; and it should be followed through the extraventricular mass of gray matter of the same body. The anterior commissure is free in the middle line for about the eighth of an inch, where it lies before the pillars of the fornix. Laterally it per- forates the corpus striatum, passing in succession through the intraven- tricular gray mass, the Avhite fibres, and the extra gray ventricular gray mass. Lastly, the commissure pierces the white layer bounding externally the corpus striatum, and spreads in the hemisphere over the inferior cornu of the lateral ventricle communicating with the temporo-sphenoidal and central lobes. posterior commissure of the cerebrum {e) is smaller than the ante- rior, and is placed above the passage into the fourth ventricle. Laterally it enters the substance of the 0 })tic thalamus ; and pierces this body to end in the hemisphere. The connections of the thalamus opticus (inferior ganglion of the cere- brum) (6) will be best seen on the side on which the inferior cornu of the lateral ventricle has been opened. It has the form of a cube, and bounds the lateral and third ventricles. The upper surface projects in the floor of the lateral ventricle, and is marked in front by a prominence — anterior tubercle, near the taenia semi- circularis. The under surface forms part of the roof of the inferior cornu of the lateral ventricle, and into it the crus cerebri is inserted. By its inner side it enters into the third ventricle ; and along the upper part lies the peduncle of the pineal body. On the outer side are the cor pus striatum, the tsenia semicii cularis, and the substance of the hemisphere. The anterior end looks to the foramen of Monro. And the posterior part, which is free in the inferior cornu of the lateral ventricle, presents inferiorly two small roundish tubercles, which are placed one outside and the other inside the bend (genu) of the optic nerve, and are named from their position to it, internal and external geniculate bodies. The structure of the optic thalamus will be subsequently referred to, p. 211 . The origin of the optic nerve can now be seen. At the back of the crus cerebri the optic tract receives fibres from the thalamus which it touches, and then divides into two terminal bands: — One of these is connected with the gray matter in the external geniculate body, and is continued onwards to one of the corpora quadrigemina (nates) ; the other is connected with the internal geniculate body. Dissection. The origin of the fornix in the optic thalamus may be fol- lowed out next. As a preparatory step the anterior commissure, the anterior part of the corpus callosum, and the commissure of the optic 208 DISSECTION OF THE BRAIN. nerves, should be cut along the middle line, so that the left hemisphere can be separated from the other. On the left hemisphere the crus of the fornix is to be traced downwards through the gray matter of the third ventricle to the corpus albicans, and then upwards into the optic thalamus. Anterior pillar of the fornix. The fornix begins in the thalamus near the tubercle on the upper surface. From this spot it descends in a curved direction to the corpus albicans, where it makes a turn like half of the figure 8, and furnishes’a white envelope to the gray matter of that body. The crus then ascends through the gray substance in front of the optic thalamus, and is applied to the like part of the opposite side to form the body of the fornix. It is joined by bands of fibres from the taenia semi- circularis and peduncle of the pineal body. The pineal body and the corpora quadrigemina, which are placed be- hind the third ventricle, may be next examined. Dissection. All the pia mater should be carefully removed from the sur- face of the quadrigeminal bodies, es[)ecially on the right side, on which they are to be seen. The posterior part of the hemisphere of the same side may be taken away. T\\q pinecd gland (conarium) is a small conical body (fig. 68,^), which is situate above the posterior commissure, and between the anterior pair of the corpora quadrigemina. In shape like the cone of a pine, it is about a quarter of an inch in length, and has the base or wider part turned for- wards. It is connected to the optic thalami by two white bands, — pedun- cles of the pineal body (/): these begin at the base, and extending for- wards, one on each side along the inner part of tlie thalamus, end by joining the crura of the fornix. At the base of the gland is a band of trans- verse white fibres which unites it which the posterior commissure. This body is of a red color and vascular, and incloses two or more cells containing a thick fiaid, with amyloid bodies, and a calcareous material (brain sand) consisting of particles of })hosphate and carbonate of lime, and phosphate of magnesia and ammoniad In its substance are large pale nucleated cells. The corpora, quadrigemina (fig. 68) are four small bodies, which are arranged in pairs, right and left, and are separated by a median groove. Each pair is situate on the upper aspect of the cerebral peduncle of the same side. The anterior eminence (/?, nates) is somewhat larger than the posterior, from which it is sei)arated by a slight depression; it is oblong from before backwards, and sends forward a white band to join the optic tract and thalamus. The posterior eminence (f, testis) is rounder in form and whiter in color than the preceding ; it lias also a lateral white band which is directed beneath the corpus geniculatum internum, and blends with the peduncular fibres in the thalamus opticus. These bodies are small masses of gray substance enveloped by white, and are placed on the band of the fillet which forms the roof of the aque- duct of Sylvius. The processes (brachia) to the optic thalamus are acces- sory parts to the peduncular fibres of the cerebrum (p. 209). Fillet of the olivary body. If the iqqier margin of the cerebellum be J These particles are referred to by Kolliker, as pathological products ; and the concentrically arranged masses amongst them are said to be incrustations of fibrin coagula. FIBRES OF CEREBRUM. 209 pulled aside, a white band, about a quarter of an inch in width, will be seen to issue from the transverse fibres of the pons, and to bend upwards over the peduncle of the cerebellum to the corpora quadrigemina (fig. 65, *). Tliis is the upper or commissural piece of the fillet (p. 128), which passes beneath the corpora quadrigemina, and joins with the similar part of the opposite side over the Sylvan aqueduct. Structure of the Cerebrum. In each cerebral hemisphere three principal sets of constituent fibres are recognized, viz., diverging, trans- verse, and longitudinal. The former are in part derived from the spinal cord ; while the two latter, joining distant pieces of the cerebrum, are con- sidered to be only connecting or commissural in their office. Peduncular or diverging fibres (fig. 56). In the crus cerebri two bundles of longitudinal fibres are collected; these are separated, in part, by gray matter, and are derived from the medulla oblongata (p. 191). Dissection. A complete systematic view of the diverging fibres can- not be now obtained on the imperfect brain. At this stage the chief pur- pose is to show the passage of the radiating fibres from the crus through the two cerebral ganglia. To trace the diverging fibres onwards beyonds the crus cerebri, and through the corpus striatum, the nucleus caudatus of this body should be scraped away (fig. 65) ; and the dissection should be made on the left side on which the striate body and the optic thalamus remain uncut. In this proceeding the pecten of Reil comes into view, viz., gray matter passing between the white fibres in the corpus striatum, and giving the appearance of the teeth of a comb. On taking away completely the prolonged part of the nucleus caudatus, others of the same set of fibres will be seen issuing from the outer side of the optic thalamus, and radiating to the posterior and inferior lobes. After tracing those fibres, the upper part of the optic thalamus may be taken away at the posterior end, to denude the accessory bundles to the peduncular fibres, from the corpora quadrigemina and the superior pedun- cle of the cerebellum (fig. 65, ^) : the last band lies beneath the corpora quadrigemina. Their arrangement (fig. 65,®). Some of the diverging fibres radiate from the peduncle of the cerebrum to the surface of the hemisphere, pass- ing in their course through the two cerebral ganglia (optic thalamus (®) and corpus striatum (^) ), and they form a conically-shaped bundle, whose apex is below and base above. The fibres forming the free or fasciculated part (crust) of the peduncle (fig. 56) pass through the striate body. The fibres on the opposite aspect, which form the tegmentum (fig. 57, c?), are transmitted through the under part of the optic thalamus, and through the corpus striatum, reaching as far forwards as, but much farther back than those of the crust. In the thalamus and the corpus striatum the fibres are greatly increased in number. The upper or sensory set receive also accessory bundles from the superior peduncle of the cerebellum (fig. 65, ^) in the crus cerebri (p. 191); and from the pair of the corpora quadrigemina, and the corpora geniculata of the same side, in the thalamus. On escaping from the striate body and the thalamus the fibres decussate with the converging fibres of the corpus callosum, and radiate then into the anterior, middle, and posterior parts of the cerebral hemisphere, form- ing the corona radiata. In the hemisphere the fibres are continued to 14 210 DISSECTION OF THE BRAIN. the convolutions : their expansion in the hemisphere resembles a fan bent down in front and behind, forming thus a layer which is concave on the under side. Their extent. All the fibres of the peduncle do not reach the surface of the brain, for some end in the corpus striatum and the optic thalamus, especially in the former. And some of the fibres in the convolutions begin in the ganglionic bodies before mentioned, and extend to the surface of the hemisphere.^ Thus, in addition to the fibres continued throughout, viz., from the crus to the surface, some unite the peduncle of the cerebrum with the ganglia, and others connect the ganglia with the convolutions on the exterior. Fig. 65. 1. Superior peduncle. 2. Middle, and 3, infeiior peduncleof the cerebellum. 4. Process from the fillet of the oli- vary body to the corpora quadri- gemina : on the right side it is cut and refiected. 5 Posterior pyramid. 6. Continuation of the lateral tract into the optic thalamus. 7. Corpora quadrigemiua. 8. Optic thalamus. 9. Corpus striatum. 10. Corpus callosum. Connection posteriorly between the Cerkbrhm and the Medulla Oblonoata and Cerebellum. Their source. The fibres thus entering inferiorly the cerebrum through its peduncle, and continued thence to the periphery of the hemisphere, are derived from the component pieces of the medulla oblongata except the restiform body (fig. 57), viz., from anterior pyramid, lateral column and olivary body, and posterior pyramid (p. 183) : they serve to connect the spinal cord with the cerebrum. The decussation between opposite sides has been before referred to (p. 186). The transverse or co7nmissural fibres connect the hemispheres of the cerebrum across the middle line. They give rise to the great commissure or the corpus callosum (p. 210) : and to the anterior and posterior com- missures (p. 207). Those bodies have been already examined. Longitudinal fibres. Other connecting fibres pass from before back- wards, uniting together parts of the same hemisphere. The chief bands of this system are the following, the fornix, the tienia semicircularis, and the peduncles of the pineal body. Other longitudinal fibres may be enu- ' According to some authors none of the fibres of the peduncle reach farther than the corpus striatum and the optic thalamus. SURFACES OF CEREBELLUM. 211 merated on the upper and under surfaces of the corpus callosum, along the middle line, together with tlie band of the convolution of the corpus cal- losum : these fibres are connected with the anterior perforated spot of the base of the brain. Structure of the optic thalamus. The thalamus is about an inch deep, and the following is a summary of its structure, as displayed in the pre- vious dissections. The upper and inner half is formed chiefly of gray matter, with Avhich the undermentioned white bands are connected : Thus through it pass the fornix in front, and the posterior commissure behind ; whilst the pedun- cles of the pineal body lie along the inner side, and the taenia semicircu- laris along the outer. The lower and outer part consists mainly of white fibres directed upwards, and these are derived from the peduncle of the cerebrum in- feriorly, and from the peduncle of the cerebellum and the corpora quadri- gemina superiorly : to the hinder part of them two slips of fibres are added from the corpora geniculata. The corpora geniculata contain gray substance inside. Into these bodies fibres of the optic tract enter ; and from each issues a band to join the fibres of the crus cerebri. They seem to serve as accessory ganglia to the peduncular fibres of the cerebrum. Corpus striatum. By slicing through the corona radiata on the left side, so as to bring into view the extraventricular nucleus of the corpus striatum, the extent and form of that mass, and the situation of the ante- rior commissure in it, will be apparent. Crus cerebri. By a vertical section through the left peduncle of the cerebrum, the disposition and the thickness of the two layers of its longi- tudinal fibres ; and the situation and extent of the locus niger between them, may be perceived. Section V. THE CEREBELLUM. Dissection. The cerebellum (fig. 59, h) is to be separated from the remains of the cerebrum, by carrying the knife through the optic thala- mus so that the small brain, the corpora quadrigemina, the crura cerebri, the pons, and the medulla oblongata, may remain united together. All the pia mater is to be carefully removed from the median fissure on the under surface ; and the different bodies in that fissure are to be sepa- rated from one another. Lastly the handle of the scalpel should be passed along a sulcus at the circumference, which is continued from the crus, be- tween the upper and under surfaces. The cerebellum^ little brain (fig. 66), is flattened from above down, so as to be widest from side to side, and measures about four inches across. This part of the encephalon is situate in the posterior fossae of the base of the skull, beneath the tentorium cerebelli. Like the cerebrum, it is in- completely divided into two hemispheres ; the division being marked by a wide median groove along the under surface, and by a notch at the poste- rior border which receives the falx cerebelli. 212 DISSECTION OF THE BRAIN. Upper Surface. On the upper aspect the cerebellum is raised in the centre (fig. G8), but slopes towards the circumference. There is not any median sulcus on this surface ; and the halves are united by a central con- stricted part — the superior vermiform process. Separating the upper from, the under surface, at the circumference, is the horizontal fissure^ which is wide in front, and extends backwards from the pons Varolii to the middle line of the cerebellum. The UNDER SURFACE is convcx, being received into the fossce of the base of tlie skull, and is divided into hemispheres (fig. 66) by a median hollow (vallecula). Fig. 66. Under part of the Cekebellpm, seen from behind, the Medulla Oblonoata, 6, BEING cut away IN GREATER PART. а. Pons Varolii. c to e. Inferior vermiform process, consisting б. Medulla oblongata, cut through. of; — c. Uvula, d. Pyramid, e. Com- missural laminse. Lobes of each half of the Cerebellum on the Under Surface. /. Suhpeduncular. k. Posterior. g. Amygdaloid. 3 Third nerve attached to the crus cerehri. h. Biventral. 5. Two roots of the fifth nerve attached to the i. Slender. side of the pons Varolii. ' The central Jissure, or the vallecula, is wider at the middle than at either the anterior or the posterior end, and receives the medulla oblongata. In the bottom of the fissure is a mass named inferior vermiform process (fig. 66, c to e), which corresponds w’ith the central part connecting the halves of the cerebellum on the upper surface. The two vermiform processes constitute the general commissure of the halves of the cerebellum. Constituents of the vermiform process. In the inferior vermiform pro- cess are the following eminences, which may be easily separated from one another with the handle of the scalpel ; — Most anteriorly is a narrow body, the uvula (fig. 66, c), wliich is named from its resemblance to the same part in the throat ; it is longer from before backwards tlian from side to side, and is divided into lamime. Its anterior projection into the fourth ventricle is named nodule, or laminated tubercle (fig. 67); and on the side is a band of gray matter with ridges and sulci, the furrowed band (fig. 67, d), which unites it with the almond-like lobe of tlie hemisphere. Connected with the nodule is a thin white layer, — the medullary velum LOBES OF THE CEREBELLUM. 213 (&) ; but this, and the furrowed band will be seen in a subsequent dissec- tion (p. 214). Behind the uvula is a tongue-shaped body, named 'pyramid (fig. GG, f/), which is elongated from side to side, and is marked by trans- verse laminee. Further back are certain transverse pieces (f*), extending between the posterior lobes of the hemispheres, of which they were con- sidered by Reil to be the commissures. Lamince. The surface of the cerebellum is covered by plates or laminae (fig. G8), instead of convolutions, which form segments of circles with their convexity directed backwards. On the upper aspect the anterior laminae pass from the one hemisphere to the other, with only a slight bending forwards in the superior vermiform process ; but those on the under aspect join the sides of the different commissures in the median fissure. Sulci. Between the laminae are sulci, which are lined by the pia mater, and reach to different depths : the sliallower separate the laminae ; but the deeper limit the lobes, and reach downwards to the white substance of the interior. Here and there the sulci are interrupted by cross laminae. Structure of the lamince. On cutting across the laminae of the upper surface on the right side they will be seen to possess a white internal, and a gray external layer (fig. G8). The white part is derived from a central medullary mass ; and dividing, like the branching of a tree, it ends in small lateral ofi’sets which enter the subdivisions of the laminm. Besides the white stalk of the laminae, derived from the central mass, there are other white fibres which pass from one lamina to another beneath the sulci. The stratum of gray matter enveloping the white substance resembles the cortical covering of the convolutions of the cerebrum. It is con- structed of two strata, inner and outer, which can be distinguished by a difference in their color. The superficial stratum is clear gray, and about equal to the other in thickness ; but the deeper one is of a rust-color, and is generally thickest in the hollows between the lamina3. Between the two a layer of ramified cells (Purkinje) may be recognized with the micro- scope. Lobes of the Hemisphere. Each hemisphere is subdivided into lobes on both aspects. On the upper surface there are two lobes, anterior and posterior, which are separated by a sulcus, but the interval between them is not well marked. The anterior or square lobe extends back to a level with the posterior edge of the vermiform process ; and the posterior reaches thence to the great horizontal fissure at the circumference. On the under surface of the cerebellum (fig. GG), there are five lobes ; and three of them are separated by sulci amongst the lamince of the hemi- sphere, but they are scarcely more distinct than the lobes on tlie upper surface. Beginning behind, the student will meet first the posterior lobe (I), which joins the commissural lamince behind the pyramid in the val- ley. Next in succession is the slender lobe (i), which is connected with the posterior part of the pyramid, as well as with the other transverse laminae behind that body. And lastly, attached to the side of the pyramid, is the biventral lobe (Ji). The two other lobes, though smaller are more separate, and appear be- tween the biventral lobe and the medulla oblongata : — One of these is the amygdaloid lobe (^), which projects into the vallecula opposite the uvula, and touches the medulla oblongata. The other is a small pyramidal slip, 214 DISSECTION OF THE BRAIN. which is directed outwards over (the under surface of the cerebellum being uppermost) the crus cerebelli, and is named flocculus, or subpeduncular lobe if). Dissection. To see the flocculus and the posterior medullary velum, the biventral and slender lobes are to be sliced off on the left side, so that the amygdaloid lobe may be everted from the valley (fig. 67). The Hoc- Fig. 67. View from behind of the under surface of the Cerebellum, ■vtith some of the lobes REMOVED to SHOW THE POSTERIOR MEDULLARY VeLUM. а. Uvula. d. Furrowed band. e. Pyramid. /. Amygdaloid lobe, turned aside. б. Posterior medullary velum, with a bit of g. Medulla oblongata raised, showing posterior whalebone under it. surface. c. Subpeduncular lobe or flocculus. cuius is laid bare by this proceeding, and passing from it to the tip of the uvula is the thin and soft white layer of the posterior velum ; beneath the last a bit of paper may be inserted. The furrowed band on the side of the uvula can be fully seen now. Flocculus and medullary velum. The position of the flocculus to the crus cerebelli has been before mentioned. This body (c) resembles tlie other lobes in structure, and may be considered a rudimentary lobe ; for it is divided on the surface into laminte, and contains a white medullary centre which furnishes offsets to the lamina?. Passing from the flocculus to the tip of the inferior vermiform process (nodule) is tlie half of a thin white layer {h), t\\id posterior medullary velum, which serves as a commissure to the flocculi. On each side this band is semilunar in form. Its anterior edge is free ; but its posterior border is attached in front of tlie transverse furrowed band {d). In front of the nodule the pieces of opposite sides are united. Interior of the Cerebellum. In the cerebellum there is not any cavity or ventricle inclosed as in the cerebrum. In the interior there is a large white centre, corresponding with that of the cerebrum, which fur- nishes offsets to the lamina?, and to other parts of the encephalon. Dissection. For the purpose of seeing the medullary centre, with its contained corpus dentatum, remove all the lamina? from the upper surface on the left side. This dissection may be accomplished by placing the scalpel in the horizontal fissure at the circumference, and carrying it in- wards as far as the upper vermiform jirocess, so as to detach the cortical stratum. If the corpus dentatum does not at first appear, thin slices may be made anteriorly till it is reached. INTERIOR OF CEREBELLUM. 215 Medullary Centre. In the centre of each cerebellar hemisphere is a large white mass, containing in its substance a dentate body. From its surface offsets are furnished to the different laminae. And from the ante- rior part proceeds a large stalk-like process, the crus cerebelli, which is subdivided into three pieces or peduncles, an upper for the cerebrum, a middle piece for the pons, and a lower one for the medulla oblongata. The superior peduncle (processsus ad cerebrum) is directed forwards towards the corpora quadrigemina (fig. 65, ^). It is rather flattened in shape, and forms part of the roof of the fourth ventricle : between the pro- cesses of opposite sides the valve of Vieussens is situate. Its fibres, con- tinuous behind with the inferior vermiform process, receive an offset from the interior of the corpus dentatum ; and passing beneath the band of the fillet and the pair of the corpora quadrigemina of the same side, enter the optic thalamus, and are applied to the fibres of the crus cerebri (p. 209). Beneath the corpora quadrigemina the internal fibres of the peduncle are directed across the middle line, through the bundle prolonged fi-om the fasciculus teres.* In this way the fibres of each peduncle end partly in the same, and partly in the opposite hemisphere of the cerebrum. Between the superior peduncles is a thin,' translucent, white layer — the iralve of Vieussens (vellum medullare anterius), which enters into the roof of the fourth ventricle (fig. 68, k). It is thin and pointed anteriorly, but widens behind, where it is connected with the under part of the vermiform process. Near the corpora quadrigemina the fourth nerve (^) is attached to the surface of the valve ; and close to the cerebellum the surface is marked by some gray transverse ridges. The middle peduncle (processus ad ])ontem), commonly named the crus cerebelli (fig. 65, ^), is tlie largest of the three peduncular processes. Its fibres begin in the lateral part of the cerebellum, and are directed forwards to the pons, of which they form the transverse fibres, and unite with the peduncle of the opposite side. This peduncle is supposed to serve as a commissural or connecting band between the halves of the cerebellum. The inferior peduncle (fig. 65, (processus ad medullam) passes down- wards to the medulla oblongata, and gives rise to the restiform body. Its fibres begin chiefly in the laminae of the upper surface of the cerebellum. It will be better seen when the fourth ventricle has been opened. The fibres in the peduncles connect one cerebellar hemisphere with the cerebrum; with its fellow; and with the medulla oblongata of the same side, in the manner mentioned above. The dentate body (corpus dentatum) is contained in the white mass of the cerebellum, and resembles the like part in the corpus olivare of the medulla oblongata. This body measures nearly an inch from before back, and is situate near the inner part of the white centre. It consists of a small plicated capsule, which, when cut across, appears as a thin, wavy, grayish-yellow line ; the bag is open at the interior part, and incloses a nucleus of whitish substance. Through its aperture issues a band of fibres from the nucleus to join the superior peduncle. Dissection. One other section (fig. 68) must be made to show the fourth ventricle, and the structure of the vermiform process. The cerebellum still * This intercommunication was known to Reil, and was named “ ansa” by him, but the decussation has been since noticed by Stilling, Ueber den Ban des Ilirnlc- nolens: 1846. 216 DISSECTION OF THE BRAIN restMig on under surface, let the knife be carried vertically through the centre of tlie vermiform processes; and then the structure of the central uniting part, as well as the boundaries of the fourth ventricle, may be observed on separating the halves of the cerebellum. Fig. 68. View of the Third and Fourth Ventricles. The former being obtained by the removal of the vehim interpositum ; and the latter by dividing vertically the veriniforin process of the cerebellum. (From a cast in the Museum of University College.) The third ventricle is the interval i a. Corpus striatum. b. Optic thalamus. c. Anterior commissure. d. Middle or soft commissure. €. Posterior commissure. g. Pineal body. /. Peduncle of the pineal body. /( and i. Left pair of the corpora quadrigentina. The fourth ventricle, v, is at the back of the medulla oblangata. the middle line between the optic thalami, b. k. Valve of Vieussens. l. Upper peduncle of the cerebellum. 0 . Eminentia teres. p. Anterior fossa. r. Posterior fossa. .9. Posterior pyramid. 4. Origin of the fourth nerve from the valve of Vieussens. Strncture of the vermiform process (fig. G8). The upper and lower rermiform processes of tlie cerebeilum are united in one central part, which connects together the hemispheres. The structure of this connecting FOURTH VENTRICLE. 217 piece is the same as that of the rest of the cerebellum, viz., a central white portion and investing laminae. Here the branching appearance of a tree (arbor vitae) is best seen, in consequence of the laminae being more divided, and the white central pieces being longer and more ramified. The FOURTH VENTRICLE (fossa I’liomboidalis) is a space between the cerebellum and the posterior surface of the medulla oblongata and pons (fig. C)8). It has the form of a lozenge, with the points placed upwards and downwards. The upper angle reaches as high as the upper border of the pons; and the lower, to a level with the inferior end of the olivary body. Its greatest breadth is 0 |)posite th'e lower edge of the pons; and a transverse line in this situation would divide the hollow into two triangu- lar portions — upper and lower. The lower half has been named calamus scriptorius from its resemblance to a writing pen. The lateral boundaries are more marked above than below. For about half way down, the cavity is limited on each side by the superior .peduncle of the cerebellum (/), which projecting over it forms part of the roof; and along the lower half lies the eminence of the restiforrn body (fig. 55, ^). The roof of the space is somewhat arched, and is formed above by the valve of Vieussens (i('), and the under part of the vermiform process ; and below, by the reflection of the pia mater from that process to the spinal cord. HXieJioor of the ventricle is constituted by the posterior surfaces of the medulla oblongata and pons, and is grayish in color. Along its centre is a median fissure, which ends below, near the point of the calamus, in a minute hole — the aperture of the canal of the cord. On each side of the groove is a spindle-shaped elevation, fasciculus s. eminentia teres (o). This eminence reaches the whole length of the floor, and is pointed and little marked interiorly, where it is covered by gray substance ; but it be- comes whiter and more prominent superiorly, and its widest point is oppo- site the lower border of the pons. The outer border of the eminence is limited externally by a slight groove, which points put the position of two small fossie (fovea anterior et posterior). The posterior (r) is near the lower end of the groove ; and the anterior (^p) is opposite the crus cerebelli. Above the anterior fossa is a deposit of very dark gray substance, which has a bluish appearance as it is seen through the thin stratum covering it f from it a bluish streak is continued upwards, at the outer edge of the eminentia teres, to the opening in the top of the fourth ventricle. Crossing tlie floor on each side, opposite the lower border of the pons, are some white lines, which vary much in their arrangement (fig. 55) : they issue from the central median fissure, and enter the auditory nerve (p. 181 ). Besides the objects above mentioned, there are other eminences in the floor of the ventricle indicating the position of the nuclei of origin of cer- tain nerves. In the lower half of the space are three slight eminences on each side for the hypo-glossal, vagus, and auditory nerves : that for the hypo-glossal is close to the middle line below, and eorresponds with the lower pointed end of the eminentia teres. The other two, outside that eminence, are placed in a line one above another, but separated by a well-marked groove • The term locus caeruleus has been applied to the spot, and the dark vesicular matter in it has been named substantia ferruyinea. 218 DISSECTION OF THE BRAIN. (fovea posterior) ; the lower is tlie nucleus of the vagus and glosso-pharyn- geal nerves, and the upper is the nucleus of the auditory nerve. Running into the lower part of the vagus nucleus, is the nucleus of the accessory portion of the spinal accessory nerve. (See p. 189.) In the upper half of the space some other nerves take origin from nu- clei, but there is only one projection. This is placed over the common nucleus of the sixth and the facial nerve : it is a rounded elevation on the outer part of the eminentia teres, about a line above the white cross striae on the floor, and close behind the fovea anterior. The fourth ventricle communicates at the upper part with the third ventricle tlirough the Sylvian aqueduct ; and with the subarachnoid space of the cord and brain, through an aperture in tlie pia mater intervening between the medulla and the cerebellum : laterally, the ventricular space is extended for a short distance between the cerebellum and the side of the medulla oblongata. Tlie lining of the other ventricles is prolonged into this by the aperture of communication with the third. Covering the floor is a columnar epi- thelium, which is continuous with that in the upper part of the central canal of the spinal cord (Clarke). In this ventricle is a vascular fold — choroid plexus^ on each side, simi- lar to the body of the same name in the other ventricles. It is attached to the inner surface of the membrane (pia mater) which closes the ventricle between the medulla and the cerebellum, and it extends upwards on the side of tlie opening into the sub-arachnoid space. Its vessels are supplied by the inferior cerebellar artery. Gray matter of fourth ventricle. The gray matter forms a surface- covering for the floor of the fourth ventricle. It is continuous below with the gray commissure of the cord, and extends upwards to the aqueduct of Sylvius (p. 187). The special nuclei have been referred to already (p. 217). Arch of the aorta furnishes to the neck, ARTERIES OF THE HEAD AND NECK 219 TABLE OF THE 1. Common carotid . pi. Brachio-^ cephalic . 2. subcla- vian . . 2. left common carotid. t.3. left subclavian. CHIEF ARTERIES OF THE HEAD AND NECK. 1. Superior thyroid fl. External carotid . 2. lingual 3. facial 4. occipital inferior superior 5. posterior auricular 6. ascending pharyngeal 7. temporal 8. internal maxillary L n Arteriaj receptaculi. 2. ophthalmic 2. internal carotid . 3. antero cerebral 4. anterior communicating .5. middle cerebral 6. posterior communicating L7. choroid. ( Hyoid branch . < laryngeal ( thyroid. { Hyoid branch J dorsal lingual ' j sublingual , I ranine. Tlnferior palatine branch tonsillitic glandular submental inferior labial coronary . lateral nasal ^angular. Meningeal branch posterior cervical. Stylo-rnastoid branch auricular mastoid. S Pharyngeal branches < meningeal, f Auricular I parotid articular transverse facial middle temporal anterior temporal posterior temporal. Inferior dental middle meningeal muscular posterior dental .-{ infraorbital spheno-palatine descending palatine vidian pterygo-palatine. ^Lachrymal supraorbital central of the retina I ciliary .-5 muscular ethmoidal palpebral frontal ^nasal. f 1. Vertebral 2. internal mammary 'Anterior spinal posterior spinal inferior cerebellar posterior meningeal 1 transverse basilar I anterior inferior cerebellar I superior cerebellar ^posterior cerebral. Infra thyroid Ascending cervical. 3. thyroid axis . . 4. superior L intercostal suprascapular . l^transverse cervical . I Deep cervical. ^ Supraspinal ^ infraspinal. t Superficial cervical ^ posterior scapular. 220 VEINS OF THE HEAD AND NECK TABLE OF THE CHIEF VEINS OF THE HEAD AND NECK. 1. Lateral sinus 2. ascending l)haiyugeal. 3. lingual f Internal ju- gular . .-{ Brachio-ce- phalic is formed by-^ the union of 4. facial f Superior longitudinal I sinus inferior longitudinal sinus straight sinus I occipital sinuses ophthalmic vein superior petrosal ^inferior petrosal. J Meningeal branches ( pharyngeal. S Superficial dorsal lingual ranine. 'Angular . inferior palpebral dorsal and lateral nasal veins. anterior internal maxil- •i lary 5. occipital coronary buccal masseteric laiiial submental inferior palatine tonsillitic ■glandular. Mastoid vein cervical. superior inferior { Supraorbital frontal palpebral nasal. r Alveolar branches I infraorbital descending palatine naso-palatine vidian. 6. superior thyroid | 7. middle thyroid . fl. Vertebral Spinal deej) cervical ascending cervical. 1. Internal maxillary uibclavian - 2. external jugular 3, anterior jugular 2. temporal 3. posterior auricular 4. branch to the internal jugular. 5. suprascapular 6. transverse cervical f Middle meningeal I inferior dental . deep temporal pterygoid l_masseteric. r Anterior posterior J middle temporal ' j parotid I anterior auricular [^transverse facial. < Auricular ’ ( Stylo-mastoid. J Supraspinal ^ infraspinal. t Superficial cervical I posterior scapular. CRANIAL NERVES OF THE HEAD AND NECK 221 TABLE OF THE CRANIAL NERVES. 1. First nerve . 2. Second nerve 3. Third nerve 4. Fourth nerve f Ophthalmic Filaments to the nose. To retina of the eyeball. To muscles of the orbit. To superior oblique muscle. 'Meningeal lachrymal frontal . . . . .nasal < Lachrymal ^ palbebral. < Supraorbital ( supratrochlear. TTo lenticular ganglion J ciliary nerves I infratrochlear 1. nasal. ophthalmic or ( Connecting branches lenticular J ganglion. . ] I ciliary nerves. f Orbital branch superior max-J to Meckel’s ganglion illary . . ] posterior dental anterior dental ^ infraorbital Internal branches ( To nasal nerve < to the third nerve ( to sympathetic. < Malar ( temporal. Nasal naso-palatine. ascending Meckel’s gang- lion . descending 5. Fifth or tri-faciaL nerve. I posterior . To the orbit. C Anterior palatine ^ posterior j ( external. < Vidian < pharyngeal. fSmall or muscular part fDeep temporal J masseteric j buccal (.pterygoid. inferior maxil- | lary . ' Auriculo- temporal f Articular and to I meatus parotid j auricular (.temporal. .large or sensory part gustatory fTo submaxillary I and sublingual ^ ganglia I to hypoglossal t^to the tongue. otic ganglion . j Connecting branches ( branches for muscles. r Connecting branches branches to the submaxillary J glands and the ganglion . ] mucous mem- brane of the 1. mouth. ! C Mylo-hyoid t Inferior dental . .< labial ( incisor. To Jacobson’s nerve to the fifth and sym- pathetic. f To the gustatory, < chorda tympaui, and ( sympathetic. 222 CRANIAL NERVES OF THE HEAD AND NECK TABLE OF CRANIAL NERVES — Continued. 6. Sixth nerve . To external rectus. f Connecting branches r To join auditory I to Meckel’s ganglion •i tympanic and sym- I pathetic nerves the chorda tympani Seventh nerve, or facial I Branches for L distribution f Posterior auricular digastric branch stylo-hyoid branch temporo-facial . { Temporal malar infraorbital. S. Eighth nerve, or auditory f Connecting branches Ninth nerve, pharyngeal or glosso- 10. Tenth nerve, or pneumo-J gastric ... ^ cervico-facial To the portio dura nerve to cochlea. nerve to vestibule ■1 To vagus to sympathetic. Jacobson’s nerve B’’anches for . distribution Connecting branches Branches for distribution r Connecting 11. Eleventh nerve, or spinal J branches accessory . • Branches for distribution Connecting branches 12. Twelfth nerve, lingual or hypoglossal . . Branches for distribution Buccal supramaxillary inframaxillary. rTo the common sac J to the saccule j to the semicircular I, canals. Joins otic ganglion, supplies tympanum. r To carotid artery I to the pharynx tonsillitic branches muscular b lingual. To glosso-pharyngeal sympathetic and au- ricular nerves To the hypoglossal. (■pharyngeal nerve. superior laryngeal cardiac nerves. inferior laryngeal rExternal laryngeal ascending ^ ^be J J J. < mucous '1 / membrane to join the inferior lar- t yngeal. r Cardiac oesophageal, tracheal to J constrictor and mus- cles of larynx to join superior laryn- L geaL ^ To pneumo-gastric ( to the cervical plexus. < To sterno-mastoideus ^ and trapezius. r To the pneumo-gas- I trie nerve W to the sympathetic to loop of atlas to gustatory nerve. { descendens noni thyro-hyoid nerve to the lingual mus- cles and tongue. The sympathetic nerve in the neck. SPINAL AND SYMPATHETIC NERVES 223 TABLE OF THE SPINAL AND SYMPATHETIC NERVES OF THE HEAD AND NECK. Spinal Nerves. C /The first four form the Cervical Plexus, which gives /Superficial ascending superficial descending deep internal f Small occipital nerve < great auricular ( superficial cervical. ( Supraacromial < supraclavicular ( suprasternal. fTo the pneume-gastric I to the hypoglossal to the sympathetic I to join the spinal accessory [^nerves to desceiidens noni. /Anterior branches \deep muscular rTo rectus muscles j to diaphragm to the sterno-mastoideus to the trapezius 1 to the levator anguli scapula. The cervical spinal / nerves ( divide i into The last four and part of first dor- sal form the Brachial Plexus, which \ gives . Branches above the clavicle . (^branches below f The rhomboid nerve I to the phrenic nerve J suprascapular nerve j subclavian branch I posterior thoracic l^to the scaleni muscles. 5 Are dissected with the upper I limb. posterior \ branches TAre distributed to the muscles of •<^ the back, and give off cuta- neous nerves. Sympathetic Nerve. /l. Superior cervical ganglion has . /Ascending branches, Which unite in -< plexuses / external branches Carotid plexus, which gives Branch to tympanic plexus to the vidian to the sixth and fifth cranial nerves. rTo the third cranial nerve I to the fourth cranial nerve ! to the fifth and lenticular gang- I lion. to the carotid artery and L branches. To join pneumo-gastric and hvpoglossal nerves to the spinal nerves. Cavernous plexus, which gives branches . . internal branches \ Pharyngeal branches < superficial cardiac nerve. 'branches to vessels Nervi molles. 2. Middle cervical ganglion ( External branches internal . To the spinal nerves. Middle cardiac nerve to supply thyroid body and join the external laryngeal. r Anterior branches To the subclavian artery. 3. Inferior cervical ^ external ganglion < To the spinal nerves forming ( vertebral plexus. internal Inferior cardiac nerve. 224 DISSECTION OF THE UPPER LIMB. CHAPTEE in. DISSECTION OF THE UPPER LIMB. Section I. THE WALL OF THE THORAX AND THE AXILLA. The parts included in tliis section, viz., the wall of the chest and the axilla, are to be learnt within a fixed time, in order that the examination of the thorax may be undertaken. Whilst the dissection of the thorax is in progress, the student will have to discontinue his labors on the upper limb ; but, on the completion of that cavity, he must be ready to begin the part of the Back that belongs to him. Position. Whilst the body lies on the Back, the thorax is to be raised to a convenient height by a block ; and the arm, being slightly rotated outwards, is to be placed at a right angle to the trunk. Directions. Before the dissection is entered on, attention should be given to the depressions on the surface, to the prominences of muscles, and to the projections of the bones ; because these serve as guides to the position of parts beneath the skin. Surface-marking . Between the arm and the chest is the hollow of the arm-pit, in which the large vessels and nerves of the limb are lodged. The extent of this hollow may be seen to vary much with the position of the limb to the trunk ; for in proportion as the arm is elevated, the fore and hinder boundaries are carried upwards and rendered tense, and the depth of the space is diminished. In this spot the skin is of a dark color, and is furnished with hairs and large sweat glands. If the arm is forcibly raised and moved in different directions, whilst the fingers of one hand are placed in the arm-pit, the head of the humerus may be recognized. On the outer side of the limb is the prominence of the shoulder ; and immediately above it is an osseous arch, which is formed internally by the clavicle, and externally by the spine and the acromion process of the scapula. Continued downwards from about the middle of the clavicle, is a slight depression between the pectoral and deltoid muscles, in which the coracoid process can be felt near that bone. A second groove, extending outwards from the sternal end of the clavicle, corresponds with the inter- val between the clavicular and sternal origin of the great pectoral muscle. Along the front of the arm is the prominence of the biceps muscle ; and on each side of that eminence is a groove, which subsides interiorly in a depression in front of the elbow-joint. The inner of the two grooves, the deepest, indicates the position of the brachial vessels. If the elbow joint be semifiexed, the prominences of the outer and inner condyles of the humerus will be rendered evident, especially the inner. PARTS ON FRONT OF THORAX. 225 Below the outer condyle, and separated from it by a slight interval, the head of the radius projects ; it may be recognized by rotating the bone, the fingers at the same time being placed over it. At the back of the articulation is the prominence of the olecranon. Dissection. As the first step in the dissection, raise the skin from the side of the chest and the arm-pit, over the great pectoral muscle and the hollow of the axilla, by means of the following incisions: — One is to be made along the middle of the sternum. A second, carried along the cla- vicle for the inner two-thirds of that bone, is to be continued down the front of the arm rather beyond the anterior fold of the arm-pit, and then to be turned across the inner surface of the arm as far as the hinder fold of the axilla. From the xiphoid cartilage a third cut is to be directed outwards over the side of the chest, as far back as to a level with the pos- terior fold of the arm-pit. The flap of skin now marked out should be reflected outwards beyond the axilla ; but it should be left attached to the body, in order that it may be used afterwards for the preservation of the part. The subcutaneous fatty layer of the thorax resembles the same structure in other parts of the body; but in this region it does not contain much fat. Beneath the subcutaneous layer is a deeper and stronger special fascia which closely invests the muscles, and is continuous with the deep fascia of the arm. It is thin on the side of the chest, but becomes much thicker Avhere it is stretched across the axilla. An incision through it, over the arm-pit, will render evident its increased strength in this situation, and the casing it gives to the muscles bounding the axilla ; and if the fore finger be introduced through the opening, some idea will be gained of its capability of confining an abscess in that hollow. Dissection. The cutaneous nerves of the side of the cliest are to be next sought. At the spots where they are to be found they are placed beneath the fat, so that the student must cut through it ; and those on the clavicle lie also beneath the platysma muscle. Small vessels will indicate the position of the nerves. Some of them (from the cervical plexus) cross the clavicle at the middle, and the inner part. Others (anterior cutaneous of the thorax) appear at the side of the sternum — one from each intercostal space. And the rest (lateral cutaneous of the thorax) should be looked for along the side of the chest, about one inch below the anterior fold of the axilla, there being one from each intercostal space except the first : as the last-mentioned nerves pierce the wall of the thorax, they divide into an anterior and a posterior piece. The posterior pieces of the highest two nerves are larger than the rest. They are to be followed across the arm-pit, and a junction is to be found there with a branch (nerve of Wrisberg) of the brachial plexus. Cutaneous nerves of the cervical plexus. These cross the clavicle and are distributed to the integuments over the pectoral muscle. The most internal branch (sternal) lies near the inner end of the bone, and reaches but a short distance below it. Other branches (clavicular), two or more in number and larger in size, cross the centre of the clavicle and extend to near the lower border of the pectoralis major ; they join one or more of the anterior cutaneous nerves of the thorax. The cutaneous nerves of the thorax are derived from the trunks of the intercostal nerves between the ribs (fig. G9). Of these there are two sets : One set, lateral cutaneous nerves of the thorax, arise from the 15 226 DISSECTION OF THE UPPER LIMB. trunks of the nerves about midway between the spine and the sternum. The other set, anterior cutaneous nerves of the tliorax, are the termina- tions of the same intercostal trunks at the middle line of the body. The anterior cutaneous nerves piercing the pectoral muscle, are directed outwards in the integuments as slender filaments. The offset of tlie second nerve joins a cutaneous branch of the cervical plexus ; and the others sup|)ly the integuments and the mammary gland. Small cutaneous branches of the internal mammary vessels accompany the nerves. The lateral cutaneous nerves (fig. 69) issue with companion vessels between the digitations of the seratus muscle, and divide into an anterior and a ])Osterior piece. There is not usually any lateral cutaneous nerve to the first intercostal trunk. The anterior offsets {^) bend over the pectoral muscle, and end in the integuments and the mammary gland : they increase in size downwards, and the lowest give twigs to the digitations of the external oblique muscle. The cutaneous nerve of the second intercostal trunk wants commonly the anterior offset. The posterior offsets (®) end in the integuments over the latissimus dorsi muscle and the back of the scapula, and decrease in size from above down. The branch of the second intercostal nerve is larger than the rest, and perforates the fascia of the axilla ; it supplies the integument of the arm (p. 251), and is named inter costo -humeral. As it crosses the axilla it is divided into two or more pieces, and is connected to the nerve of Wris- berg (^) by a filament of variable size. The branch of the third intercostal gives filaments likewise to the arm- pit and the inner part of tlie arm. The MAMMA is the gland for the secretion of the milk, and is situate on the lateral aspect of the fore part of the chest.^ Resting on the great pectoral muscle, it is hemispherical in form, but it is rather most prominent at the inner and lower aspects. Its dimensions and weight vary greatly. In a breast not enlarged by lactation, the width is commonly about four inches. Longitudinally it extends from the third to the sixtli or seventh rib, and transversely from the side of the sternum to the axilla. Its thickness is about one inch and a half. The weight of the. mamma ranges from six to eicrht ounces. Nearly in the centre of the gland (rather to the inner side) rises the conical or cylindrical projection of the nipple or mamilla. This promi- nence is about half an inch or rather more in length, is slightly turned outwards, and presents in the centre a shallow depression, where it is rather redder. Around the nipple is a colored ring, — the areola., about an inch in width, whose tint is influenced by the complexion of the body, and is altered during the times of menstruation, pregnancy, and lactation. The skin of the nipple and areola is provided with numerous papillaB and lubricating glands ; and on the surface are some small tubercles marking the position of the ducts of the glands. In the male the mammary gland resembles that of the female in general form, though it is less prominent; and it possesses a small nipple, which is surrounded by an areola provided with hairs. The glandular or secre- tory structure is im[)erfect. • If tlie studiuit lias a male body, lie may disregard the description of the mamma ; and if the body is a female, he may set aside the breast for a more con- venient examination of its structure. MAMMARY GLAND. 227 Structure. In its texture the mamma resembles those compound glands which are formed by the vesicular endings of branched ducts. It consists of small vesicles which are united to form lobules and lobes. Connected witli each lobe is an excretory or lactiferous duct. A layer of areolar tissue, containing fat, surrounds the gland, and penetrates into the interior, subdiving it into lobes ; but in the ultimate structure of tlie gland, and in the nipjde and areola, there is not any fatty substance. Some fibrous septa fix the gland to the skin, and support it ; these are the ligamenta suspensoria of Sir A. Cooper. Vesicles. The little vesicles or cells at the ends of the most minute ducts are rounded in shape, and when filled with milk or mercury are just visible to the naked eye, being about the size of a small pinhole in paper. (Cooper.) Each is surrounded externally by a close vascular network. Lobules and lobes. A collection of the vesicles around their ducts form the lobule or glandule, which varies in size from a pin’s head to a small tare. By the union of the lobules the lobes are produced, of which there are about twenty altogether, and each is provided with a distinct duct. The d?/cts issuing from the several lobes (about twenty) are named from their office gulactophorus ; they converge to the areola, where they swell into oblong dilations or reservoirs (sacculi) of one-sixth to one-third of an inch in width. Onwards from that spot the ducts become straight ; and, surrounded by areolar tissue and vessels, are continued through the nipple, nearly parallel to one another, and gradually narrowing in size, to open on the summit by apertures varying from the size of a bristle to that of a common pin. Like many other excretory ducts, the milk tubes consist of an external or fibrous, and of an internal or mucous coat ; they and the vesicles are sheathed by a columnar epithelium, which becomes flattened towards the outer opening. Beneath the skin of the nipple and areola are branched lubricating glands, which open on the tubercles before mentioned. Bloodvessels . — The arteries are supplied by the axillary, internal mammary, and intercostal, and enter both surfaces of the gland. The veins end principally in the axillary and internal mammary trunks ; but others enter the intercostal veins. The nerves are supplied from the anterior and lateral cutaneous branches of the thorax, viz., from the third, fourth, and fifth intercostal nerves. The lymphatics of the inner side open into the anterior mediastinal glands ; but on the outer side they reach the axillary glands. Dissection (fig. G9). With the limb in the same position to the trunk, the student is first to remove the fascia and the fat from the surface of the great pectoral muscle. In cleaning the muscle the scalpel should be car- ried in the direction of the fibres, viz., from the arm to thorax ; and the dissection may be begun at the lower border on the right side, and at the upper border on the left side. The fascia and the fat are to be taken from the axilla, without injury to the numerous vessels, nerves, and glands in the space. The dissection will be best executed by cleaning first the large axillary vessels at the outer part, where these are about to enter the arm : and then following their branches which are directed to the chest, viz., the long thoracic under cover of the anterior boundary, and the circumflex and subscapular vessels and nerves along tlie posterior boundary. Some arterial twigs entering the axillary glands should be traced out. In taking away the fascia and fat from the muscles in the posterior 228 DISSECTION or THE UPPER LIMB. boundary of the space, the small internal cutaneous nerve of the musculo- spiral should be looked for near the great vessels. The large nerves of the brachial plexus are then to be defined. The smallest of these, which possibly may be destroyed, is the nerve of Wris- berg : it lies close to the hinder edge of the axillary vein, and joins with the intercosto-humeral nerve. When cleaning the serratus muscle on the ribs the student is to seek on its surface the posterior thoracic nerve ; and to trace the posterior off- sets of the intercostal nerves crossing the axilla. THE AXILLA. The axilla is the hollow between the arm and the chest (fig. 69). It is somewhat pyramidal in form, and its apex is directed upwards to the root of the neck. The space is larger near the thorax than at the arm, and its boundaries are as follows : — Boundaries. In front and behind the space is limited by folds, which are constructed by the muscles passing from the trunk to the upper limb. In the anterior fold are the two pectoral muscles, but these take unequal shares in its construction, in consequence of the difference in their size and shape : — thus the pectoralis major a extends over the whole front of the space, reaching from the clavicle to the lower edge of the anterior fold ; whilst the pectoralis minor b, which is a narrow muscle, corresponds only with the middle third of the space. In the posterior boundary, from above down- wards, lie the subscapularis f, the latissimus dorsi muscle d, and the teres major e : this boundary reaches further out than the anterior, especially near the humerus ; and its lower margin, which is formed by the latissimus dorsi, projects forwards beyond the level of the subscapularis. On the inner side of the axilla lie the first four ribs, with their inter- vening intercostal muscles, and the part of the serratus magnus c taking origin from those bones. On the outer side the space has but small di- mensions, and is limited by the humerus and the coraco-brachialis and biceps muscles (g and h). The apex of the hollow is situate between the clavicle, the upper mar- gin of the scapula, and the first rib; and the forefinger may be introduced into the space for the purpose of ascertaining the upper boundaries, and the depth. The base or widest part of the pyramid is turned downwards, and is closed by the thick aponeurosis reaching from the anterior to the posterior fold. Contents of the space. In the axilla are contained the axillary vessels and the brachial plexus, with their branches ; some branches of the inter- costal nerves ; together with lymphatic glands, and a large quantity of loose areolar tissue and fat. Position of the trunks of vessels and nerves. The large axillary artery (a) and vein (6) cross the outer portion of the space in passing from the neck to the upper limb. The part of each vessel now seen lies close to the humerus, reaching beyond tlie line of tlie anterior fold of the arm-pit, and is covered only by the common superficial coverings, viz., the skin, the fatty layer or superficial fascia, and the deep fascia. Behind the vessels are the subscapularis (f) and the tendons of the latissimus and teres muscles (u and e). To their outer side is the coraco-brachialis muscle (g). BOUNDARIES OF AXILLA 229 On looking into the space from below, the axillary vein (b) lies on the thoracic side of the artery. After the vein has been drawn aside, the artery will be seen amongst the large nerves of the upper limb, having the median trunk (^) to the outside, and the ulnar (^) and the small nerve of Wrisberg (®) to the inner side ; the internal cutaneous generally superficial to, and the musculo- spiral (^) and circumflex nerves beneath it. This part of the artery gives branches to the side of the chest and the shoulder. The vein receives some branches in this spot. Fig. 69. View of the Dissecteh Axilla (Illustrations of Dissections). Muscles : A. Pectoralis major. B. Pectoralis minor, c. Serratus magnus. D. Lastissimus dorsi. E. Teres major. F. Subscapiilaris. o. Coraco-brachialis H. Biceps. Vessels : a. Axillary artery. b. Axillary vein. c. Subscapular vein. d. Subscapular artery. e. Posterior circumflex artery. Position of the branches of vessels and nerves. The several branches of the vessels and nerves have the undermentioned position with respect to the boundaries : — Close to the anterior fold, and concealed by it, the long thoracic Nerves : 1. Median. 2. Internal cutaneous. 3. Ulnar. 4. Musculo-spiral. 6. Nerve of Wrisberg. 6 Internal cutaneous of musculo-spiral. 7. Subscapular. 5. Posterior pieces of the lateral cutaneous of the thorax. 9. Anterior pieces of cutaneous of the thorax. 230 DISSECTION OF THE UPPER LIMB. artery runs to the side of the chest ; and taking the same direction, thougli nearer tlie middle of the hollow, are tlie small external mammary artery and vein. Extending along the posterior fold, within its lower margin and in con- tact with the edge of the subscapularis muscle, are the subscapular vessels and nerves {d and ; and near the humeral end of the subscapularis the posterior circumflex vessels and nerve (e) bend backwards beneath the large axillary trunks. On the inner boundary, at the upper part, are a few small branches of the superior tlioracic artery, which ramify on the serratus muscle; but these are commonly so unimportant, that this part of the axillary space may be considered free from vessels with respect to any surgical operation. Lying on the surface of the serratus magnus, is the nerve to that muscle ; and })erforating the inner boundary of the space, are the lateral cutaneous nerves of the thorax — two or more offsets of wliicli are directed across the axilla to the arm, and receive the name intercosto-humeral. The lymphatic glands of the axilla are arranged in two sets : one is placed along the inner side of the bloodv'Tcssels ; and the other occupies the lower and hinder parts of the space, lying near and along the posterior boundary. Commonly they are ten or twelve in number ; but in number and size they vary much. Small vascular twigs from the branches of the axillary vessels are furnished to them. The glands by the side of the bloodvessels receive the lymphatics of the arm ; and those along the hinder boundary are joined by the lymphatics of the fore part of the thorax and posterior surface of the Back, as well as by some from the mamma. Most of the efferent ducts unite to form a trunk, which opens into the lymphatic duct of the neck of the same side ; some may enter separately the subclavian vein. The PECTORALis MAJOR, A, is triangular in shape, with the base at the thorax and the apex at the arm. It arises internally from the front of the sternum, and the cartilages of the true ribs except the last ; superiorly from the sternal half of the clavicle ; and interiorly from the aponeurosis of the external oblique muscle of the abdomen. From this wide origin the fibres take different directions — tliose from the clavicle being inclined obliquely downwards, and those from the lower ribs upwards beneath the former ; and all end in a tendon, which is inserted into the outer edge of the bicipital groove of the humerus for about two inches. This muscle bounds the axilla anteriorly, and is connected sometimes to its fellow by fibres in front of the sternum. Besides the superficial structures and the mamma, the platysma covers the pectoralis major close below the clavicle. A lengthened interval, whicli corresponds with a de- ])ression on the surface, separates the clavicular from the sternal attach- ment. One border (outer) is in contact witli the deltoid muscle, and with the cephalic vein and a small artery ; and the lower border forms the margin of the anterior fold of the axilla. The parts covered by the muscle will be seen subsequently. Action. If the humerus is hanging, the muscle will move forwards the limb until the elbow reaches the front of tlie trunk, and will rotate it in. When the limb is raised, the pectoralis depresses and adducts it ; and acting with other muscles inserted into the opposite side of the humerus, it may dislocate the head of that bone when the lower end is fixed, as in a fall on the elbow. PECTORALIS MINOR MUSCLE. 231 Supposing both limbs fixed as in climbing, the trunk will be raised by both muscles ; and the ribs can be elevated in laborious breathing. Dissection (fig. 70). The great pectoral muscle is to be cut across now in the following manner : — Only the clavicular part is to be first divided, so that the branches of the nerve and artery to the muscle may be found. Reflect the cut part of muscle, and press the limb against the edge of the table, for the purpose of raising the clavicle and rendering tight the fascia attached to that bone ; on carefully removing the fat, and a piece of fascia prolonged from the upper border of the small pectoral muscle, the membranous costo- coracoid sheath will be seen close to the clavicle, covering the axillary vessels and nerves. At this stage the cephalic vein is to be defined as it crosses inwards to the axillary vein. A branch of nerve (anterior thoracic), and the acro- mial thoracic artery, which perforate the tube of membrane around the vessels, are to be followed to the pectoral muscles. The remaining part of the pectoralis major may be cut about its centre, and the pieces may be thrown inwards and outwards. Any fat coming into view is to be removed ; and the insertion of the tendon of tlie pecto- ralis is to be followed to the humerus. Insertion of the pectoralis. The tendon of the pectoralis consists of two parts, anterior and posterior, at its attachment to the bone ; the ante- rior receives the clavicular and upper sternal fibres, and joins the tendon of the deltoid muscle ; and the posterior gives attachment to the lower ascending fibres. The tendon is from two inches to two inches and a half wide, and sends upwards one expansion over the bicipital groove to the capsule of the shoulder-joint, and another to the fascia of the arm. Parts covered hy the pectoralis. The great pectoral muscle covers the pectoralis minor, and forms alone, above and below that muscle, the ante- rior boundary of the axilla. Between the pectoralis minor and the clavicle it conceals the subclavius muscle, the sheath containing the axillary ves- sels, and the branches perforating that sheath. Below the pectoralis minor it lies on the side of the cliest, on the axillary vessels and nerves, and on the biceps and coraco-brachialis muscles near the humerus. The PECTORALIS MINOR (fig. 70, ®) resembles the preceding muscle in shape, and is extended like it from the thorax to the arm. Its origin is connected by slips with the third, fourth, and fifth ribs, external to their cartilages ; and between the ribs, with the aponeurosis covering the inter- costal muscles. The fibres converge to their insertion in the anterior half of the upper surface of the coracoid process of the scapula. This muscle is placed before the axillary space, and assists the pecto- ralis major in forming the middle of the anterior boundary: in that po- sition it conceals the axillary vessels and the accompanying nerves. The upper border lies near the clavicle, but between it and that bone is an in- terval of a somewhat triangular form. The lower border projects beyond the pectoralis major, close to the chest ; and along it the long thoracic artery lies. The tendon of insertion is united with the short head of the biceps and the coraco-brachialis. Action. Acting with the serratus magnus it moves the scapula for- wards and somewhat downwards. In laborious breathing it becomes an inspiratory muscle, as it takes its fixed point at the scapula. 232 DISSECTION OF THE UPPEK LIMB. Dissection. Supposing the clavicle raised by the pressing backwards the arm, as before directed, the tube of fascia around the vessels will be demonstrated by making a transverse cut in the costo-coracoid membrane near the clavicle, so that the handle of the scalpel can be passed beneath it. By raising the lower border of the subclavius this muscle will be seen to be incased by fascia, which is attached to the bone both before and be- hind it. Tlie costo-coracoid membrane., or ligament (fig. 70), is a firm membra- nous band, which receives this name from its attachment on the one side to the rib, and on the other to the coracoid process of the scapula. Between those points it is inserted into the clavicle, inclosing the subclavius muscle ; and is joined by the piece of fascia that incases the small pectoral muscle. From its strength and position it gives protection to the vessels surrounded by their loose sheath. When traced downwards it is found to descend on the axillary vessels and nerves, joining externally the fascia on the coraco-brachialis muscle, and blending with the sheath of the axillary vessels beneath the small pectoral muscle. Its extent is not so great on the inner as on the outer side, for internally it reaches but a very short distance on the axillary vein. The sheath of the axillary vessels and nerves, e, is derived from the deep fascia of the neck, being prolonged from that on the scaleni muscles ; and resembles, in its form and office, the funnel-shaped tube of membrane surrounding the femoral vessels in the upper part of the thigh. It is strongest near the subclavius muscle, where the costo-coracoid band joins it. The anterior part of the tube is perforated by the cephalic vein (e), the acromial thoracic artery (a), and the anterior thoracic nerve (*). Dissection. After the costo-coracoid membrane has been examined, the remains of it are to be taken away ; and the subclavius muscle, and the axillary vessels and nerves with tlieir branches, are to be carefully cleaned. The SUBCLAVIUS muscle (fig. 70, is roundish in form, and is placed between the clavicle and the rib. It arises by a tendon from the first rib, at the junction of the osseous and cartilaginous parts, and in front of the costo-clavicular ligament. The fibres ascend obliquely, and are inserted into a groove on the under surface of the clavicle, which reaches between the two tubercles (internal and external) for the attachment of the costo and coraco-clavicular ligaments. The muscle overhangs the large vessels and nerves of the limb, and is inclosed, as before said, in a sheath of fascia. Action. It depresses the clavicle, and indirectly the scapula ; but if the shoulder is fixed it elevates the first rib. The AXiLLARV ARTERY (fig. 70) contiiiues the subclavian trunk to the upper limb. The part of the vessel to which this name is applied is con- tained in the axilla, and extends from the lower border of the first rib to the lower edge of the teres major muscle (h). In the axillary space its position will be marked by a line from the middle of the clavicle to the inner edge of the coraco-brachialis. Its di- rection will vary with the position of the limb to the trunk ; for when the arm lies by the side of the body the vessel is curved, its convexity being upwards ; and in proportion as the limb is removed to a right angle with the chest, the artery becomes straight. In the upper part of the axilla the vessel is deeply placed, but it becomes superficial as it approaches the arm. AXILLARY ARTERY. 233 Its connections with surrounding parts are numerous ; and the descrip- tion of these will be methodized by dividing the artery into three parts — one above, one beneath, and one below the small pectoral muscle. Above the small pectoral muscle the artery is contained in the axillary sheath of membrane, e. This part is concealed by the clavicular portion of the great pectoral muscle. Behind it are the intercostal muscles of the first space and the first digitation of the serratus magnus. Fig. 70. Second View of the Dissection of the Thorax (Illustrations of Dissections). Muscles : A. Pectoralis major, cut. B. Pectoralis minor, c. Serratus magnus. D. Subclavius. E. Axillary sheath. F. Suhscapularis. G. Latissimus dorsi. H. Teres major. J. Coraco-trachialis. K. Biceps. Vessels : a. Acromial-thoracic branch. h. Long thoracic branch. c. Subscapular branch. d. Axillary artery. e. Cephalic vein. /. Brachial veins joining the axillary veins, g. Nerves : 1 and 2. Anterior thoracic branches. 3. Subscapular branch. 4. Nerve to the serratus. 5. Intercosto-humeral branch. To the thoracic side is placed the axillary vein (^). The cephalic vein (e), and offsets of the acromial thoracic artery and vein, cross over it. On the acromial side lie the two cords of the brachial plexus, separated from the vessel by a slight interval. Superficial to it lies an anterior tho- racic nerve ; and beneath, is the posterior thoracic. Beneath the pectoralis^ the pectoralis minor and major b and a are superficial to the axillary vessel. But there is not any muscle immediately 234 DISSECTION OF THE UPPERnLIMB. in contact behind, for the artery is placed across the top of the axilla, particularly when the limb is in the position required by the dissection. The companion vein {g) lies to the inner side, but separated from the arterial trunk by a bundle of nerves. In this position the cords of the brachial plexus lie around it, one being outside, a second inside, and a third beneath the artery. Beyond the pectoralis minor the artery is concealed in part by the lower border of the great pectoral muscle a, but thence to its termination it is covered only by the integuments and the fascia. Beneath it are the sub- scapularis muscle, f, and the tendons of the latissimus and teres, G and h. To the outer side is the coraco-brachialis muscle, J. The axillary vein remains as above on the thoracic side of the artery. Here the artery lies in the midst of the large trunks of nerves into which the brachial plexus has been resolved: On the outer side is the median nerve, with the musculo-cutaneous for a short distance; and on the inner side are the ulnar, and the nerve of Wrisberg. Superficial to the vessel is the internal cutaneous ; and behind are the musculo-spiral and circumflex nerves, the latter extending only as far as the border of the subscapular muscle. The branches of the axillary artery are furnished to the wall of the thorax and the shoulder. The thoracic branches are four in number; two (superior and acromial thoracic) arise from the artery above the pectoralis minor; one (alar thoracic) beneath the muscle; and one (long thoracic) at the lower border. Three branches are supplied to the shoulder, viz., subscapular and two circumflex; the first springs opposite the edge of the muscle of the same name, and the others wind round the neck of the humerus. The last offsets are the external mammary and some muscular twigs. The superior thoracic branch is the highest and smallest offset, and arises opposite the first intercostal space; it ramifies on the side of the chest, anastomosing with the intercostal arteries. Tlie acromial thoracic branch (fig. 70, a) is a short trunk on the front of the artery, which appears at the upper border of the pectoralis minor, and opposite the interval between the large pectoral and deltoid muscles. Its branches are directed inwards, outwards, and upwards: — a. The inner set supply the thoracic muscles, and give a few offsets to the side of the chest to anastomose with the intercostal and other thoracic arteries. h. The outer or acromial set end mostly in the deltoid ; but one small artery accompanies the cephalic vein for a short distance ; and another {inferior acromial) perforates the deltoid muscle, and anastomoses on the acromion with a branch of the suprascapular artery of the neck. c. One or two small twigs ascend to the subclavius and deltoid muscles. The alar thoracic is very inconstant as a separate branch, and its place is taken by offsets of the subscapular and long thoracic arteries; it is dis- tributed to the glands and fat of the axillary space. Tlie long thoracic branch is directed along the border of the pectoralis minor (fig. 70, h) to about the sixth intercostal space; it supplies the pec- toral and serratus muscles, and anastomoses, like the other branches, with the intercostal and thoracic arteries. In the female it gives branches to the mammary gland. An external mammary artery is commonly met with, especially in the female ; its position is near the middle of the axilla with a companion vein. BRACHIAL PLEXUS. 235 It supplies the glands, and ends in the wall of the thorax below the pre- ceding. Tlie snhscapular branch (fig. 70, c) courses with a nerve of the same name along the subscapularis, as far as the lower angle of the scapula, where it ends in brandies for the serratus magnus, and tlie latissimus dorsi and teres muscles: it gives many offsets to the glands of the space. Near its origin the artery sends backwards a considerable dorsal branch round the edge of the subscapular muscle: this gives an infrascajndar offset to the ventral aspect of the scapula, and then turns to the dorsum of that bone, where it will be afterwards dissected. The subscapular artery is frequently combined at its origin with other branches of the axillary, or with brandies of the brachial artery. The circiimjlex branches (anterior and posterior) arise near the border of the subscapular muscle. One turns in front of, and the other behind the humerus. They will be followed in the examination of the arm. Small muscular ojfsets enter the coraco-brachialis muscle. The AXILLARY VEIN {g) continues upwards the basilic vein of the arm and has the same extent and connections as the axillary artery. It lies to the thoracic side of its artery, and receives thoracic and shoulder branches. Opposite the subscapular muscle it is joined externally by a large vein, which is formed by the union of the veme comites of the brachial artery; and near the clavicle the cephalic vein opens into it. Dissection. To follow out the branches of the brachial plexus, cut through the pectoralis minor near its insertion into the coracoid process, and turn it towards the chest, but without injuring the thoracic nerves in contact with it. The axillary vessels are next to be cut across below the second rib,‘ and to be drawn down with hooks; and their thoracic branches may be removed at the same time. A dense fascia is to be cleared away from the large nerves of the plexus. The BRACHIAL PLEXUS results from the union of the anterior branches of the four lower cervical nerves with the first dorsal (in part) ; and a slip is added to it above from the lowest nerve in the cervical plexus. It is placed partly in the neck, and partly in the axilla, and is divided opposite the coracoid process into large trunks for the supply of the limb. The part of the plexus above the clavicle is described in the dissection of the head and neck (p. 79). The part below the clavicle has the same connec- tions with the surrounding muscles as the axillary artery. The nerve trunks interlace in it generally in the following manner : — At first the plexus consists of two bundles of nerves, which lie on the outer side of the artery, and are thus constituted ; — the one nearest the vessel is formed by the last cervical with the })art of the first dorsal nerve ; and the other, by the fifth, sixth, and seventh cervical nerves. A little lower down a third or posterior cord is produced by the union of two fas- ciculi, one from each of the other bundles ; so that, beneath the small pec- toral muscle, the plexus consists of three large cords, one being on the outer side, another on the inner side, and the third behind the vessel. Occasionally there may be some deviation from the above mentioned arrangement. The branches of the plexus below the clavicles arise from the several cords in the following way : — • ' The student must he Ccareful not to cut the vessels In'gher than the spot men- tioned, otherwise he will injure the dissection of the neck. 236 DISSECTION OF THE UPPER LIMB. The outer cord gives origin to one anterior thoracic branch, the musculo- cutaneous trunk, and the outer head of the median nerve. The mner cord produces a second anterior thoracic nerve, the inner head of the median, the internal cutaneous, the nerve of Wrisberg, and the ulnar nerve. The posterior cord furnishes the subscapular branches, and ends in the circumflex and musculo-spiral trunks. Only the thoracic and subscapular nerves are dissected to their termina- tion at present ; the remaining nerves will be seen in the arm. The anterior thoracic branches (fig. 70, ^ and ^), two in number, are named outer and inner, like the cords from which they come. The outer nerve crosses inwards over the axillary artery, to the under surface of the great pectoral muscle in which it ends. On the inner side of the vessel it communicates with the following branch. The inner thoracic branch turns upwards between the arteiy and vein, and after receiving the offsets from the other, ends in many branches to the under surface of the pectoralis minor. Some twigs enter the great pectoral muscle, after passing either through the pectoralis minor or above its border. The subscapular nerves are three in number, and take their names from the muscles supplied : — The branch of the subscapularis is the highest and smallest, and enters the upper part of that muscle. The nerve of the teres major gives a small offset to the inferior part of the subscapularis, and ends in its muscle. A long nerve of the latissimus dorsi {^) takes the course of the sub- scapular artery along the posterior wall of the axilla, and enters the fleshy fibres near the outer end. Another small nerve, nerve to the serratus (^) (posterior thoracic), lies on the surface of the serratus muscle. It arises above the clavicle (p. 80), from the fifth and sixth cervical nerves ; it descends behind the axil- lary artery, and enters that surface of the serratus magnus which is turned towards the axilla. The LATISSIMUS DORSI MUSCLE, G, may be examined as far as it enters into the posterior fold of the axilla. Arising from the spinal column and the back of the trunk, and crossing the lower angle of the scapula, the muscle ascends to be inserted into the bottom of the bicipital groove by a tendon, one inch and a half in width, in front of the teres ; at the lower border aponeurotic fibres connect the two, but a bursa intervenes between them near the insertion. Dissection. To lay bare the serratus muscle between the side of the chest and the base of the scapula, the arm is to be drawn from the trunk, so as to separate tlie scapula from the thorax. The nerves of the brachial plexus may be cut through opposite the third rib ; and the fat and fascia should be cleaned from tlie muscular fibres. The SERRATUS MAGNUS MUSCLE (fig. 71, a) extends between the scapula and the thorax. It arises by nine pointed processes from the outer surface of the eight upper ribs, — the second rib having two pieces ; and between the ribs it takes origin from the aponeurosis covering the inter- costal muscles. The fibres converge towards the base and angles of the scapula, but from a difference in their direction the muscle appears to consist of three parts. The upper part is attached internally to the first two ribs and an INTERCOSTAL MUSCLES. 237 aponeurotic arch between them ; and externally, to an impression on the ventral surface of the upper angle of the scapula. A middle part, which is very thin, extends from the second, third, and fourth ribs, to the base of the shoulder bone. And a lower part, which is the strongest, is con- nected on the one side with four ribs (fifth, sixth, seventh, and eighth), where it digitates with like processes of origin of the external oblique muscle ; and, on the other side, it is fixed into the special surface on the costal aspect of the lower angle of the scapula. The serratus is applied against the ribs and the intercostal muscles, and is partly concealed by the pectoral muscles and the axillary vessels and< nerves : in the ordinary position of the arm the scapula and subscapularis are in contact with it. Action. The whole muscle acting, the scapula is carried forwards. But the lower and stronger fibres can move forwards the lower angle, rotating the bone around an axis through the centre, and raise the acromion. Dissection. The intercostal muscles will be brought into view by de- taching the processes of origin of the serratus from the ribs for a couple of inches, and by taking away the loose tissue on the surface. Towards the front of the chest is a thin aponeurosis, which is continued forwards from each external intercostal to the sternum ; this is to be retained in the third intercostal space. Some of the lateral cutaneous nerves should be preserved. The INTERCOSTAL MUSCLES are named from their position between the ribs. There are two layers in each s()ace, but neither occupies the whole length of the space. The direction of the fibres differs in each stratum; for, whilst the fibres of the external muscle run very obliquely down- wards and forwards, those of the internal have an opposite direction between the osseous parts of the ribs, so that the two sets cross. Tlie external muscle is fixed to the outer margin of the ribs of each intercostal space, and consists of fleshy and tendinous fibres. Pos- teriorly the fibres begin at or near the tubercle of the rib ; and ante- riorly they end short of the middle line, but after a different manner in the upper and lower spaces : — In the intervals between the true ribs, they cease near the costal cartilages, and a thin aponeurosis is continued onwards from the point of ending to the sternum. In the lower spaces they are continued between the car- tilages (Theile) reaching the end of the ribs in the last two. Dissection. The internal inter- costal muscle will be seen by cutting through and removing the external layer and the fascia in one of the widest spaces, say the second ; it will be recognized by the difference in the direction of the fibres. bar back between the two muscles, and close to the rib above, the inter- Diagram of the Serratus Magnus Muscle, A. Attachments. 238 DISSECTION OF THE UPPER LIMB. costal nerve and artery will appear. A branch of the nerve to the surface (lateral cutaneous of the tliorax) should be followed through the external muscle ; and the trunk of the nerve is to be traced forwards in one or more spaces to the sternum, and the surface of the thorax. Tlie hinder part of these muscles will be seen in the dissection of the Back and thorax. The internal intercostal muscle, attached to the inner border of the ribs bounding *the intercostal space, begins in fi'ont at the extremity of tlie ribs, and ceases behind near their angles. Posteriorly they do not end at •the same distance from the spine, for the upper and lower approach nearer than the middle ; and, anteriorly, in the two lowest spaces, the muscular fibres are continuous with the internal oblique of the abdomen. One sur- face is covered by tlie external muscle and in part by the intercostal ves- sels and nerve ; and the opposite surface is in contact with the pleura. Action, By the alternate action of the intercostal muscles the ribs are moved in respiration. The external intercostals elevate the ribs and evert the lower edges, so as to enlarge the thorax in the antero-posterior and transverse directions : they come into play during inspiration. The internal intercostals act in a different way at the side and fore part of the chest. Between the osseous parts of the ribs they depress and turn in those bones, diminishing the si2e of the thorax ; and they are brought into use in expiration. Between the rib-cartilages they raise the ribs, and become muscles of inspiration like the outer layer. If both sets of muscles contract simultaneously, the motion of tlie ribs will be arrested ; or if two or more ribs are broken near the spinal column, the muscles of the space or spaces injured will be unable to move these bones. Dissection. To bring into view the triangularis sterni muscle and the internal mammary vessels, the cartilages of the true ribs, except the first and seventh, are to be taken away with the intervening muscles on the right side of the body but tlie two ribs menti med are to be left un- touched for the benefit of the dissectors of the abdomen and head and neck. Small arteries to each intercostal sjiace and the surface of tlie thorax, and tlie intercostal nerves, are to be preserved. The surface of the triangularis sterni will be apparent when the loose tissue and fat are removed. The TRIANGULARIS STERNI (fig. 72, a) is a thill muscle beneath the costal cartilages. It arises internally from the side of the xiphoid carti- lage, from the side of the sternum as high as the third costal cartilage, and usually from the inner ends of the lower three true costal cartilages. Its fibres are directed outwards, the upper being most oblique, and are inserted by fleshy fasciculi into the true ribs except the last two and the first, at the junction of the bone and cartilage, and into an aponeurosis in the intercostal spaces. The muscle is covered by the ribs and the internal intercostals, and by the internal mammary vessels and the intercostal nerves. It lies on the pleura. Its lower fibres touch those of the transversalis abdominis. 5 On tlie left side the vessels and the muscle will have been destroyed by the injection of the body. INTERNAL MAMMARY VESSELS. 239 Action. The muscle assists in depressing the anterior ends of tlie ribs ; and by diminishing the size of the thorax, it becomes an expiratory muscle. The internal mammary artery is a branch of the subclavian (p. 77), and enters the thorax beneath the cartilage of the first rib. It is con- tinued through the thorax, lying beneath the costal cartilages and about half an inch from the sternum, as far as the interval between the sixth and seventh ribs; there it gives externally a large muscular branch (musculo-phrenic), and passing beneath the seventh rib, enters the sheath of the rectus muscle in the wall of the abdomen. In the chest the artery lies on the pleura and the triangularis sterni, and is crossed by the intercostal nerves. It is accompanied by two veins, and by a chain of lymphatic glands. The follow- ing branches take origin in the thorax : — a. A small branch {comes nervi phrenici) arises as soon as the artery enters the chest, and descends to the diaphragm along the phrenic nerve. h. A few small mediastinal branches are distributed to the remains of the thymus gland, the pericardium, and the tri- angularis sterni muscle. c. Two anterior intercostal branches turn outwards in each space, one being placed on the border of each costal cartilage, and terminate by anastomosing with the aortic inter- costal arteries. d. Perforating branches., one or two opposite each space, pierce the in- ternal intercostal and pectoral muscles, and are distributed on the surface of the thorax with the anterior cutaneous nerves : the lower branches sup- ply the mamma in the female. e. The musculo-phrenic branch courses outwards beneath the cartilages of the seventh and eighth ribs, and enters the wall of the abdomen by perforating the diaphragm : it supplies anterior branches to the lower intercostal spaces. Its termination will appear in the dissection of the abdomen. Two veins accompany the artery; these join into one trunk, which opens into the innominate vein. The intercostal nerves., seen now in the anterior part of their extent, are the anterior primary branches of the dorsal nerves, and supply the wall of the thorax. Placed at first between the layers of the intercostal muscles, each gives off the lateral cutaneous nerve of the thorax, about midway between the spine and the sternum. Diminished in size by the emission of that offset, the trunk is continued onwards, at first in, and afterwards beneath the internal intercostal muscle as far as the side of the sternum, where it ends as the anterior cutaneous nerve of the thorax. Branches supply the intercostal muscles, and the triangularis sterni. View fkom behind of the Attachments of the Triangularis Sterni Muscle, a. 240 DISSECTION OF THE UPPER LIMB. The aortic intercostal arteries lie with the nerves between the strata of intercostal muscles, and nearer the upper than the lower rib bounding the intercostal space. About the mid point of the space (from before back) the artery bifurcates : — one branch follows the line of the upper rib, and the other descends to the lower rib ; both anastomose anteriorly with the intercostal offsets of the internal mammary artery. A small cutaneous offset is distributed with the lateral cutaneous nerve of the thorax; and other branches are furnished to the thoracic wall. Directions. The dissector of the upper limb waits now the appointed time for the examination of the thorax. But as soon as the body is turned he is to take his share in the dissection of the Back, and to proceed with the parts marked for him in Chapter V. After the Back is finished the limb is to be detached from the trunk by sawing the clavicle about the middle, and cutting through the soft parts connected with the scapula. Section II. « SCAPULAR MUSCLES, VESSELS, NERVES, AND LIGAMENTS. Position. After the limb has been sepm'ated from the trunk it is to be placed with the subscapularis uppermost. Dissection. The different muscles that have been traced to the scapula in the dissection of the front of the thorax and the Back, are now to be cleaned, and to be followed to their insertion into the bone. A small part of each, about an inch in length, should be left for the purpose of ascertaining the osseous attachment. Between the larger rhomboid muscle and the serratus magnus at the base of the scapula, run the posterior scapular artery and vein, whose ramifications are to be traced. To the borders and the angles of the scapula the following muscles are connected : — From the upper margin of the scapula arises one muscle, the omo-hyoid (fig. 73, e). At its origin that muscle is about half an inch Avide; it is attached to the edge of the bone behind the notch, and sometimes to the ligament which converts the notch into a foramen. The lower margin., or costa, gives origin to the long head of the triceps (fig. 79, a), and to some fibres of the teres major; but these attachments will be ascertained in the progress of the dissection. The hase of the bone has many muscles inserted into it (fig. 74). Be- tween the superior angle and the spine is the levator anguli scapula?, h. Opposite the spine the rhomboideus minor, j, is fixed. And between the spine and tlie inferior angle the rhomboideus major, r, is attached: the upper fibres of tliis muscle end often in an aponeurotic arch, and are con- nected indirectly to the bone by means of an expansion from it. Internal to those muscles, and inserted into all the base of the scapula, is the ser- ratus magnus muscle (fig. 73, d). On the inner surface of the upper and lower angles of the scapula the STJBSOAPULARIS MUSCLE. 241 fibres of tbe sernitus magniis are collected. On the outer surface of the inferior angle lies the teres major (lig. 79, g) which will be subsequently seen. The insertion of the small pectoral muscle into the fore part of the upper surface of the coracoid process may be ascertained at this stage of the dissection (tig. 73, f). Fig. 73. A. Subscapiilaris. B. Teres major. c. Latissimus ciorsi. D. Serratus maguus. E. Orao-hyoideus. F. Pectoralis minor. G. Biceps. H. Coraco-bracliialis. a. Supra-scapular artery. I. Supra-scapular uerve passing through the notch. View of the Stbscapuearts and the surrounding Muscles. The other muscles fixed into the base of the scapula as shown in fig. 74. Dissection. By the separation of the serratus from the subscapularis a thin fascia comes into view, which belongs to the last muscle, and is fixed to the bone around its margins ; after it has been observed, it may be re- moved. The subscapularis muscle is to be followed forwards to its insertion into the humerus. Next, the axillary vessels and nerves, and the offsets of these to the muscles, should be well cleaned. The SUBSCAPULARIS MUSCLE (fig. 73, a) occupies the under surface of the scapula, and is concealed by that bone when the limb is in its natural position. The muscle arises from the concave surface on the ventral aspect of the scapula, except at the angles, and this attachment reaches forwards nearly to the neck ; it is united also to the ridges of the bone by tendinous [irocesses. Externally it is inserted by a tendon into the small tuberosity of the humerus, and by fleshy fibres into the neck for nearly an inch below that process. By one surface the muscle bounds the axilla, and is in contact with the axillary vessels and nerves and the serratus magnus. By the other, it rests against the scapula and the shoulder joint ; and between its tendon and the root of the coracoid process is a bursa, which communicates gene- rally with the .sjMiovial membrane of the joint. The lower border projects much beyond the bone ; it is contiguous to the teres major, the latissimus 16 242 DISSECTION OF THE UPPER LIMB. dorsi, and the long head of the triceps : along this border is the subscapular artery, which gives backwards its dorsal branch. Action. It rotates in the hanging limb ; and when the humerus is raised it depresses the bone. If the humerus is fixed the subscapularis supports the shoulder joint with the other scapular muscles. Dissection. The subscapular muscle is to be separated from the scapula, but a thin layer of fibres, in which the vessels lie, is to be left on the bone : as it is raised its tendinous processes of origin, the connection between its tendon and the capsule of the shoulder joint, and the bursa, are to be ob- served. A small arterial anastomosis on the ventral surface of the bone is to be dissected out of the fleshy fibres. The infrascapular artery ramifies on the ventral surface of the scapula, and is an offset of the dorsal branch of the scapular vessel (p. 335): en- tering beneath the subscapularis muscle, it forms an anastomosis with small twigs of the supra and posterior scapular branches. Position. The examination of the muscles on the opposite surface of the scapula may be next undertaken. For this pur})Ose the scapula is to be turned over ; and a block, which is deep enough to make the shoulder prominent, is to be placed between that bone and the arm. Dissection. The skin is to be removed from the ])rominence of the shoulder, by beginning at the anterior border of the deltoid muscle. After its removal some small cutaneous nerves are to be found in the fat: — the upper of these extend over tlie acromion ; and another comes to the sur- lace about half way down the posterior border of the deltoid muscle. Snperjicial nerves. Branches of nerves, super- acromial., descend to the surface of the shoulder from the cervical plexus (p. 66). A cutaneous branch of the circumflex nerve (fig. 74,*'^) turns forwards with a small companion artery from beneath the posterior border of the deltoid, and supplies the integuments covering the lower two-thirds of the muscle. Dissection. The fat and fascia are now to be taken from the fleshy del- toid, its fibres being made tense at the same time. Beginning at the anterior edge of the muscle, the dissector is to carry the knife U[)wards and downwards along the fibres, in order that its coarse muscular fasciculi may bj more easily cleaned. As the posterior edge is approached, the cuta- neous nerve and artery escaping from beneath it, are to be dissected out. At the same time the fascia may be removed from the back of tlie scapula, so as to denude the muscles there. llie DELTOID MUSCLE is triangular in Ibrm (fig. 74, ^), with the base at the scapula and clavicle, and the apex at the liumerus. It arises from nearly all the lower edge of the spine of the scapula, from the anterior edge of the acromion, and from the outer half or third of the clavicle. Its fibres converge to a tendon, which is inserted into a triangular impression, two or three inches long and about one inch wide at the base, above the middle of the outer surface of the humerus. The anterior border is contiguous to the pectoralis major muscle and the cephalic vein ; and the posterior rests on the infraspinatus and triceps muscles. The origin of the muscle corresponds with the attachment ol the trapezius to the bones of the shoulder; the insertion is united with the tendon of the pectoralis major, and a fasciculus of the brachialis anticus is attached on each side ot it. Action The whole muscle raises the humerus, and abducts it from DELTOID MUSCLE. 243 the trunk. The limb being raised, the anterior fibres will carry it for- wards, and the posterior fibres will move it backwards. When the humerus is fixed as in climbing, the muscle assists in sup- {)orting tlie weight of the body, and strengthening the shoulder-joint. Dissection (fig. 74). The deltoid is to be divided near its origin, and is to be thrown down as much as the circumflex vessels and nerve beneath will permit. As the muscle is raised a large thick bursa between it and the head of the humerus comes into sight. The loose tissue and fat are to be taken away from the circumflex vessels and nerve ; and the size of the bursa having been looked to, the remains are to be removed. The insertion of the muscle should be examined. Fig. 74. ViKW OF THE Muscles of the DoRSUiM of the Scapula, and of the Circumflex Vessels AND Nerve. (Illustrations of Dissections.) M (Scles : A. Supra-sp'natus. B. Infra-spinatus. c. Teres minor. D. Teres major. E. Latissimus dorsi. F. Deltoid. a. Triceps (long head). H. Levator anguli scapul®. j. Rhomboideus minor. K. Rhomboideus major. Arteries: a. Posterior circumflex artery. h. Branch to teres minor, c. Dorsal scapular branch of sub- scapular. Nerves : 1. Posterior circumflex. 2. Its cutaneous offset to the arm. 3. Branch to the teres minor muscle. Parts covered hy deltoid. The deltoid conceals the head and upper end of the humerus, and those parts of the dorstil scapular muscles which are fixed to the great tuberosity. A large bursa, sometimes divided into sacs, intervenes between the head of the humerus and the under surface of the deltoid muscle and the acromion process. Below the head of the 244 DISSECTION OF THE UPPER LIMB. bone are tbe circumflex vessels and nerve, and the upper part of tlie biceps muscle. In front of the humerus is the coracoid [U’ocess with its muscles. Dissection. By following back the posterior circumflex vessels and nerve through a space between the humerus and the long head of the tri- ceps, G, their connection with the axillary trunks will be arrived at. In clearing the fat from the space a branch of the nerve to the teres minor muscle is to be sought close to the border of the scapula, where it is sur- rounded by dense fibrous tissue. Arching outwards in front of the neck of the humerus, is the small anterior circumflex artery : this is to be cleaned. The circumjiex arteries arise near the termination of the axillary trunk (p. 335) ; they are two in number, and are named anterior and posterior from their position to the neck of the humerus. The anterior branch is a small artery, which courses beneath the coraco-brachialis and biceps muscles, and ascends in the bicipital groove to the articulation and the head of the humerus : it anastomoses with small offsets of the posterior circumflex. The posterior circumjiex artery (fig. 74, g), larger in size, winds back- wards through a space between the humerus and the long head of the triceps, and is distributed chiefly to the deltoid muscle, in which it anasto- moses with the acromial thoracic and upper profunda arteries. Branches are given from it to the head of the humerus and the shoulder joint, and to anastomose with the anterior circumflex artery. It supplies branches likewise to the teres minor, the long head of the triceps, and the integuments. The circumjiex nerve (fig. 74,^) leaves the arm-pit with the posterior circumflex artery (p. 335), and bends round the neck of the humerus, beneath the deltoid muscle in which it ends. Many and large branches enter the deltoid, and terminate in it ; one or two filaments pierce the fibres and become cutaneous. Branches. In the axilla it gives an articular filament to the under part of the shoulder-joint. Behind the humerus it furnishes an offset to the teres minor (j, which has a reddish gangliforin swelling on it. And at the edge of the deltoid it gives origin to the cutaneous nerve before noticed. The iNFRAsriNATus MUSCLE (fig. 74, b) occupies the infraspinal part of the scapula, and extends to the head of the humerus. The muscle arises from the infraspinal fossa, except at three spots, viz., the neck, and the lower angle and inferior border wliere the teres muscles are attached ; it arises also from the lower side of the spinous process, and from the special fascia covering the surface. Its fibres converge to a tendon, which is in- serted into the middle impression on the great tuberosity of the humerus, and joins the tendons of the su[)raspinatus and teres minor. A part of the muscle is subcutaneous, and the fibres arising from the spine of the scapula overlay the tendon : the upper portion is concealed by the deltoid ; and the lower end, by the latissimus dorsi. The lower l)order is ])arallel to tlie teres minor, with which it is sometimes united. The muscle lies on the scapula and the humero-sca[)ular articulation, but between it and the joint is a small bursa. Action. With the humerus hanging it acts as a rotator outwards; and when the bone is raised it will move the same backwards in concert with the hinder part of the deltoid. DORSAL SCAPULAR MUSCLES. 245 The TEiiES MINOR (fig. 74, c) is a narrow fleshy slip, wliicli is often united inseparably with the preceding muscle, along whose lower border it lies. It arises on the dorsum of the scapula from a special surface along the upper two-thirds of the inferior costa of the bone, and from the invest- ing fascia ; and it is inserted by a tendon into the lowest of the three marks on the great tuberosity of the humerus, as well as by fleshy fibres into the humerus below that spot — about an inch together. This muscle is partly covered by the deltoid ; it rests on the long head of the triceps and the shoulder joint. Underneath it the dorsal branch of the subscapular artery turns. Action. The arm hanging the muscle rotates it out and moves it back ; the arm being raised the teres depresses the humerus. In climbing it supports tlie joint like the preceding scapular muscles. The TERES MAJOR muscle (fig. 74, d) is extended from the inferior angle of the scapula to the humerus. Its origin is from the rough surface on the dorsum of the bone at the inferior angle ; from the inferior costa as far forwards as an inch from the long head of the triceps ; and from the fascia covering the teres minor. The fibres end in a tendon which is inserted partly into, and partly behind the inner edge of the bicipital groove of the humerus. This muscle assists in forming the posterior fold of the axilla; and is situate beneath the axillary vessels and nerves near the humerus (fig. 70). At its origin it is covered by the latissimus dorsi. The upper border is contiguous to the subscapularis muscle, and the lower is received into a hollow formed by the fibres of the latissimus dorsi At the humerus the tendon of the muscle is one inch and a half to two inches wide, and is placed behind that of the latissimus: the two are separated above by a bursa ; but they are united below, and an ex|)ausion is sent from them to the fascia of the arm. A second bursa lies between the tendon and the bone. Action. If the limb hangs it is carried back behind the trunk and is rotated inwards by the muscle. The humerus being raised, the muscle depresses and adducts it. With the limb fixed by the hand the teres will cause the lower angle of the scapula to move forwards. Below the scapula (inferior costa), where the teres muscles separate from one another, is a triangular interval, which is bounded in front by the shaft of the humerus, and above and below by the teres muscles. Tliis space is divided into two by the long head of the triceps. Through the anterior part, which is of a quadrilateral shape, the posterior circumflex vessels and the circumflex nerve pass : and opposite the posterior trian- gular space, the dorsal branch (c) of the subscapular artery bends back- wards. Dissection (fig. 75). In order that the acromion process may be sawn through to expose the supraspinatus muscle, the ligaments of the scapula and clavicle, which would be injured by such a proceeding, should next be dissected. A ligament (coraco-clavicular) ascends from the coracoid ]n’ocess to the under part of the clavicle : on removing the areolar tissue it will be seen to consist of two parts, anterior and posterior, diflering in size, and in the direction of the fibres. A capsular ligament, connecting the outer end of the clavicle with the acromion, Avill be recognized by taking away the fibres of the trapezius and deltoid muscles. 246 DISSECTION OF THE UPPER LIMC. Another strong band (coraco-acromial) passing transversely between the acromion and the coracoid process ; and a small fasciculus (posterior proper ligament), placed over the notch in the superior costa, are then to be defined. Ligaments of the Clavicle and Scapula (fig. 75). The clavicle is connected to the scapula by a distinct joint with the acromion, and by a strong ligament (coraco-clavicular) between it and the coracoid process. The coraco-clavicvlar ligament consists of two parts, each having a different direction and designation. The posterior piece (^), called conoid from its shape, is fixed by its apex to the posterior and inner part of the coracoid process ; and by its base to the tubercle and tlie contiguous part of the under surface of the clavicle, at the junction of the outer with the middle third of the bone. The anterior part (‘^), trapezoid ligament^ is larger than the conoid piece : it is connected interiorly to the inner border of the carocoid pro- cess along the hinder half;, and superiorly to the line on the under surface of the clavicle which extends outwards from the tubc'rcle before mentioned. The two pieces of the ligament are in apposition posteriorly, but are sepa- rated by an interval in front. Use. Both pieces of the ligament sup{)ort the scapula in a state of rest : they serve also to restrain the rotatory movements of that bone ; thus Fig. 75. 1. Conoid ligament. 2. Trapezoid ligament. 3. Anteiior ligament of the .scapula. 4. Posterior scapular ligament. 5. Capsule of the shoulder joint. 6. Tendon of the long head of the bi- ceps entering the joint. 7. Tendon of the subscapular muscle. S. Coraco humeral ligament. Lioaments of the Clavicle and Scapula, and of the Shoulder Joint (altered from Bourgeiy and Jacob). when the acromion is rotated down, the motion is checked by the trapezoid band ; and when upwards, by the conoid jiiece. Acromio-clavicular articulation. The articular surfaces of the clavicle and acromion process of the sca})ula are retained in contact by a capsule formed of strong fibres. Some of the fibres are thicker above and below, and are considered to constitute a superior and an inferior ligament. An inter articular jihro-cartilage generally exists at the upper part of the joint ; but sometimes it forms a com[)lete interarticular septum. If the hbro-cartilage is jierfect, there are two synoviol membranes present in the joint ; if it is imperfect, there is only one. The joint should be opened to see the cartilage and the synovial membrane. Movements. In this articulation there are limited fore and back and up and down movements of the scapula. SCAPULAR LIGAMENTS. 247 Besides, there is a gliding movement of the acromion on the clavicle in rotation of the scapula. For instance, when the acromion is depressed, its articular surface moves from above down at the fore part of the joint, and from below up at the back. Wlien the acromion is deviated the sur- face moves in exactly the opposite way. Scapular Ligaments. The special Hgame7its of the scapula are two in number, anterior and posterior, and extend from one part of the bone to another. The posterior ligament (*) is a narrow fasciculus of fibres stretching across the notch in tlie upper costa of the scapula. By one end it is at- tached to the base of the coracoid process, and by the other to tlie costa behind the notch. It converts the notch into a foramen, through which the suprascapular nerve passes. The anterior or cor aco -acromial ligament (^) is triangular in form, and extends transversely between the acromion and the coracoid process. Ex- ternally it is inserted by its point or apex into the tip of tlie acromion ; and internally, where it is much wider, it is attached to all the outer border of the coracoid process, reaching backwards to the capsule of the shoulder joint. The ligament consists usually of two thickened bands, anterior and posterior, with a thin intervening part. It forms part of an arch above the shoulder joint, which stops the ascent of the head of the humerus. Dissection. To lay bare the supraspinatus muscle, the acromion pro- cess is to be sawn through, and to be turned aside with the outer end of the clavicle : but in the repetition of the dissection of the upper limb, the bone may be left uncut for the purpose of seeing the use of the coraco- acromial arch. A strong fascia covers tlie surface of the muscle ; this is to be taken away after it has been observed. The SUPRASPINATUS MUSCLE (fig. 74, has the same form as the hollow of the bone it fills. It arises from the surface of the supra-spinal fossa of the sca|)ula, except from the cervical part ; from the upper side of the spine of the bone ; and from the fascia covering the surface. Its fibres end in a tendon, which crosses over the shoulder joint, and is inserted into the upper impression of the great tuberosity of the humerus. The muscle is concealed by the trapezius and the acromion process ; and it rests upon the scapula, the shoulder joint, and the suprascapular ves- sels and nerve. Its tendon joins that of the infraspinatus at the attach- ment to the humerus. Action. It comes into use with the deltoid in raising the limb, and supporting the joint. Dissection (fig. 78). The vessels and nerves on the dorsum of the scapula can be traced by detaching from behind forwards the supra and infraspinatus muscles, so as to leave a thin layer of the fleshy fibres with the ramifying bloodvessels on the surface of the bone. In the supraspinal fossa are the suprascapular vessels and nerve, which are to be followed beneath the acromion to the infraspinal fossa ; and entering the infra- spinal fossa, beneath the teres minor muscle, is the dorsal branch of the subscapular artery. The anastomosis between those vessels should be pur- sued in the fleshy fibres and cleaned. The suprascapular artery {a) is derived from the subclavian trunk, and is one of the branches of the thyroid axis (p. 78). After a short course in the neck it passes over the ligament at the superior costa, and crossing beneath the supraspinatus muscle, ends in the infraspinal fossa, 248 DISSECTION OF THE ARM. where it gives offsets to the infraspinatus muscle and the scapula, and anastomoses with the dorsal branch of the subscapular, and the posterior sca})ular artery of the subclavian. Beneath the supraspinatus it furnishes a supraspinal branch for the supply of the muscle, the bone, and the shoulder-joint. The companion vein of the suprascapular artery joins the external jugu- lar vein. The suprascapular nerve (^) is a branch of the brachial plexus (p. 80). ^Yhen it reaches the costa of the scapula, it enters the suprasi)inal fossa beneath the posterior special ligament. In tlie fossa it supplies two branches to the supraspinatus ; and is continued beneath a fibrous band to the infraspinatus muscle, in which it ends. The nerve gives some articular filaments to the shoulder-joint, and other offsets to the scapula. The posterior scapular artery yuw^ along the base of the scapula beneath the rhomboid muscles, furnishing offsets to them and the surfaces of the bone. It is more fully noticed with the dissection of the Back. The dorsal branch of the subscapular artery (6) (p. 335) turns below the inferior costa of the scapula, opposite the posterior of the two spaces between the teres muscles. Entering the infraspinal fossa beneath the teres minor, it supplies tliat muscle and the infraspinatus, and communi- cates with the suprascapular artery. Tliis vessel sends a branch along the dorsum of the scapula between the teres muscles, towards the inferior angle of the bone. Section III. THE FRONT OF THE ARM. Position. For the dissection of the superficial vessels and nerves on the front of the arm, the limb should lie flat on the table, with the front uppermost. Dissection. The skin is to be raised from the fore and hinder parts of the arm and elbow-joint. To reflect it, make one incision along the centre of the limb as far as two inches below the elbow ; and at tlie termination, a second cut half round the forearm. Strii) now the skin from the limb, as low as the transverse incision, so that the fat which contains the cuta- neous vessels and nerves may be denuded. Between the skin and the prominence of the olecranon a bursa may be seen. The cutaneous veins (fig. 7G) may be sought first in the fat: they are very numerous below the bend of the elbow, as tliey issue from beneath the integument. One in the centre of the foreaim is the median vein, which bifurcates rather below the elbow. External to this is a small vein (radial) ; and internal to it are the anterior and })OSterior ulnar veins, coming from the front and back of the forearm. At the elbow these veins are united into two ; one (basilic) is to be followed along the inner side, and the other (cephalic) along tlie outer side of the arm. The cutaneous nerves may be next traced out. Where they perforate the deep fascia they lie beneath the fat: and this layer must be scraped through to find them. CUTANEOUS VEINS. 249 On tlie outer side of tlie arm, about its middle, two external cutaneous branches of the musculo-spiral are to be sought. In tlie outer bicipital groove, in front of the elbow or rather below it, the cutaneous part of the musculo-cutaneous nerve will be recognized. On the inner [lart of the limb the nerves to the surface are more nume- rous; Takinof the basilic vein as a o-uide, the internal cutaneous nerve of the forearm will be found by its side, about the middle of the arm ; and rather external to this nerve is a small cutaneous offset from it, which pierces the fascia higher up. Scrape through the fat behind the internal cutaneous, in the lower third of the arm, for the small nerve of Wrisbero; ; and in the upper third, seek the small nerves which have been already met witli in the dissection of tlie axilla, viz., the intercosto-humeral, and the internal cutaneous of the musculo-S[)iral. Superjicial fascia. The subcutaneous fatty layer forms a continuous investment for the limb, but it is thicker in front of the elliow than in the other parts of the arm. In that spot it incloses the superficial vessels and the lymphatics. Cutaneous Veins. The position and the connections of the superficial veins in front of the elbow are to be attentively noted by the dissector, because the operation of venesection is practised in one of them. The median vein of the forearm (fig. 76, divides into two branches, internal and external, rather below the bend of the elbow ; at its point of division it is joined by an offset from a deep vein. The internal branch (median basilic) crosses to the inner border of the biceps, and unites with the ulnar veins (®) to form the basilic vein of the inner side of the arm. The external branch (median cephalic) is usually longer than the other, and by its junction with the radial vein (^) gives rise to the cephalic vein of the arm. The connections of the two veins into which the median bifurcates, are described below : — The median cephalic vein (fig. 76) is directed obliquely, and lies over the hollow between the biceps and the outer mass of muscles of the fore- arm. Beneath it is the trunk of the musculo-cutaneous nerve ; and over it some small offsets from the nerve are directed. This vein is altogether removed from the brachial artery, and is genei‘ally smaller than the me- dian basilic vein. If opened with a lancet, it does not generally yield much blood, in consequence of its position in a hollow between muscles rendering compression of it very uncertain and difficult. The median basilic vein (fig. 76, ^) is more horizontal in direction than the preceding, and crosses the brachial artery. It is larger than the cor- responding vein of the outer side of the arm, and is firmly supported by the underlying fascia — the aponeurosis of the arm, strengthened by fibres from the biceps tendon, intervening between it and the brachial vessels. Branches of the internal cutaneous nerve lie beneath it, and some twigs of the same nerve are placed over it. The median basilic is the vein on which the operation of blood-letting is commonly performed. It is selected in consequence of its usually larger size, and more su})erficial position, and of the ease with which it may be compressed ; but from its close proximity to tlie brachial vessels, the spot to be opened should not be immediately over the trunk of the artery. The basilic vein (fig. 76, “), commencing as before said, ascends near the inner border of the biceps muscle to the middle of the arm, where it 250 DISSECTION OF THE ARM. passes beneath the deep fascia, and is continuous with the axillary vein. In this course it lies to the inner side of the brachial artery. The cephalic vein (fig. 76, is derived chiefly from the external branch of the median, for the radial vein is oftentimes very small : it is continued to the shoulder along the outer side of the biceps, and sinks between the deltoid and pectoral muscles, near the clavicle, to open into the axillary vein. 1. Median basilic vein. 2. Median vein of the forearm bifurcating. 3. Anterior ulnar veins. 4. Cephalic vein formed by radial from behind and the median cephalic in front. The mnsculo-cutaneous nerve is by the side of it. .5. Basilic vein, with large internal cutaneous nerve by its side. 6. Brachial artery, with its companion veins (one cut). 7. Kadial vein. . Cutaneous Veins anp Nerves at the Bend of the Elbow. (Quain’s “ Arteries.”) The superficial lymphatics of the arm lie for the most part along tlie basilic vein, and enter into the glands of the axilla. A few lynijihatics accompany the cephalic vein, and end as the others in the axillary glands. One or more superficial lymphatic glands are commonly found near the inner condyle of the humerus. Cutaneous Nerves. The superficial nerves of the arm appear on the inner and outer sides, and S|)read so as to cover the surface of the limb. With one exception (intercosto-humeral) all are derived from the brachial plexus, either as distinct branches, or as offsets of other nerves. On the outer side of the limb are branches of the musculo-spiral and musculo- cutaneous nerves. On the inner side are two’ internal cutaneous nerves, large and small (from the plexus), a third internal cutaneous from the musculo-spiral, and the intercosto-humeral nerve. External cutaneous Nerves. The external cutaneous branches of the musculo-spiral nerve are two in number, and appear at the outer side of the limb about the middle. The upper small one turns forwards with the cephalic vein, and reaches the front of tlie elbow, supplying the ante- rior part of the arm. The lower and larger pierces the fascia somewhat farther down, and after supplying some cutaneous filaments, is continued to the forearm. The cutaneous part of the mnsculo-cutaneous nerve pierces the fascia in front of the elbow ; it lies beneath the median cephalic vein, and divides into branches for the forearm. Internal cutaneous Nerves'. The larger internal cutaneous nerve perforates the fascia in two parts, or as one trunk that divides almost INTERNAL CUTANEOUS NERVES. 251 directly into two : — Its external branch passes beneath the median basilic vein to the front of the forearm ; and the internal winds over the inner condyle of the humerus to the back of the forearm. A cutaneous offset of the nerve pierces the fascia near the axilla, and reaches as far, or nearly as far as the elbow : it supplies the integuments over the inner part of the biceps muscle. The small internal cutaneous nerve (Wrisberg) appears below the pre- ceding, and extends to the interval between the olecranon and the inner condyle of the humerus, where it ends in filaments over the back of the olecranon. The nerve give offsets to the lower tliird of the arm on the inner and posterior surfaces, and joins above the elbow the inner branch of the larger internal cutaneous nerve. The mter^ial cutaneous branch of the musculo-spiral nerve becoming subcutaneous in tlie upper third, winds to the back of the arm, and reaches nearly as far as the olecranon. The inter costo -humeral branch of the second intercostal nerve (]>. 220), perforates the fascia near the axilla, and ramifies in the inner side and posterior surface of the arm in the upper half. But the size and distribu- tion of the nerve will depend upon the development of the small internal cutaneous and the offsets of the musculo-spiral. The aponeurosis of the arm is a white shining membrane which sur- rounds the limb, and sends inwards processes between the muscle. Over the biceps muscle it is thinner than elsewhere. At certain points it re- ceives accessory fibres from the subjacent tendons : — thus in front of the elbow an offset from the tendon of the biceps joins it ; and near the axilla the tendons of the pectoralis major, latissimus dorsi, and teres, send pro- longations to it. At the upper part of the limb the fascia is continuous with that of the axilla, and is prolonged over the deltoid and pectoral muscles to the scapula and the clavicle. Inferiorly it is continued to the forearm, and is con- nected to the prominences of bone around the elbow joint, especially to the condyloid ridges of the humerus so as to give rise to the intermuscular septa of the ai-m. Directions. As the back of the arm will not be dissected now, the skin may be replaced on it until the front has been examined. And to keep in place the vessels and nerves at the upper part of the limb, these should be tied together with string in their natural position to one another, and fastened to the coracoid process. Position. The limb is still to lie on the back, but the scapula is to be raised by means of a small block; and the bladebone is to be fixed in such a position as to render tense the muscles. The inner surface of the arm is to be placed towards the dissector. Dissection. The aponeurosis is to be reflected from the front of the arm by an incision along the centre, like that through the integuments ; and it is to be removed on the outer side as far as the outer condyloid ridge of the humerus, but on the inner side rather farther back than tlie corresponding line, so as to lay bare [)art of the triceps muscle. In rais- ing the fascia the knife must be carried in the direction of the fibres of the biceps muscle ; and to prevent the displacement of the brachial artery and its nerves, fasten them here and there with stitches. In front of the elbow is a hollow containing the brachial vessels: the artery should be followed into it, to show its ending in the radial and ulnar trunks. 252 DISSECTION OF THE ARM. Muscles on the Front of the Arm. There are only three muscles on the fore part of tlie arm. The one along the centre of the limb is the biceps ; and that along its inner side, reaching about half way down, is the coraco-brachialis. The brachialis anticus lies beneath the biceps. Some muscles of tlie forearm are connected to the inner and outer condyles of the humerus, and to the line above the outer condyle. Tlie BICEPS MUSCLE (fig. 78, forms the prominence observable on the front of the arm. It is wider at the middle than at either end; and tlie upper part consists of two tendinous pieces of ditferent lengths, which are attached to the scapula. The short head arises from the apex of the coracoid process in common Mutli the coraco-brachialis muscle (fig. 73) ; and the long head is attached to the upjier part of the glenoid cavity of tlie scapula, within the capsule of the shoulder joint (fig. 89). Muscular fibres spring from each tendinous head, and blend about the middle of the arm in a fleshy belly, which is somewhat flattened from before back. In- feriorly the biceps ends in a tendon, and is inserted into the tubercle of the radius. The muscle is superficial except at the extremities. At the upper part it is concealed by the pectoralis major and deltoid muscles; and at the lower end the tendon dips into tbe hollow in front of the elbow, having previously given an offset to the fascia of the arm. Beneath the biceps are the brachialis anticus muscle, the musculo-cutaneous nerve, and the upper part of the humerus. Its inner border is the guide to the brachial artery below the middle of the humerus, but above that spot the coraco- brachialis muscle intervenes between tliem. The connection of the long head of the biceps with the shoulder joint, and the insertion of the muscle into the radius, will be afterwards learnt. Action. It bends the elbow-joint, and acts powerfully in supinating the radius. When the body is hanging by the hands it will apply the scapula firmly to the humerus, and will assist in raising the trunk. AVith tlie arm hanging and the radius fixed, the long head will assist the abductors in removing the limb from the thorax ; and after the limb is abducted, tlie short head will aid in restoring it to the pendent position. The CORACO-BRACHIALIS (fig. 73, ”) is roundish in form, and is named from its attachments. Its origin is fleshy from the tip of the coracoid process, and from the tendinous short head of the biceps. Its fibres be- come tendinous, and are inserted., below the level of the deltoid muscle, into the ridge on the inner side of the humerus : from the insertion an aponeurotic slip is continued upM^ards to the head of the humerus, and is joined by fleshy fibres. Part of the muscle is beneath the pectoralis major (fig. 78), and forms a prominence in the axilla; but the rest is superficial, except at the inser- tion where it is covered by the brachial vessels and the median nerve. The coraco-brachialis conceals the subscapular muscle, the anterior cir- cumflex artery, and the tendons of the latissimus and teres. Along the inner border are the large artery and nerves of the limb. Perforating it is the musculo-cutaneous nerve. Action. The hanging limb is adducted to the thorax by this muscle; and the action is greater in proportion as the humerus is removed from the trunk. The humerus being fixed, the muscle will bring down the scapula, and assist in keeping the articular surfaces of the shoulder joint in apposition. BRACHIAL ARTERY. 253 The BRACHIAL artery (fig. 77, is a, continuation of the axillary trunk, and supplies vessels to the upper limb. It begins at the lower border of the teres major muscle, and terminates rather below the bend of the elbow, or “oi)posite the neck of the radius” (Quain), in two branches — radial and ulnar, for the forearm. In the upper part of its course, the vessel is internal to the humerus, but afterwards in front of that bone; and its situation is indicated by the surface depression along the inner border of the biceps and coraco-bi-achi- alis muscles. Fig. 77. 1. Axillary artery and branches; the small branch above the figure is the highest thoracic, and the larger branch close below, the acromial thoracic. 2. Long thoracic branch. 3. Subscapular branch. 4. Brachial artery and branches. 6. Superior profunda branch. 6. Inferior profunda branch. 7. Anastomotic branch. 8. Biceps muscle. 9. Triceps muscle. The median and ulnar nerves are shown in the arm ; the median is close to the bra- chial artery. Axillary and Brachial Artkries and their Branches. (Quain’s “Arteries.”) In all its extent the brachial artery is superficial, being covered by the integuments and the deep fascia; but at the bend of the elbow it becomes deeper, and is crossed by the prolongation from the tendon of the bicejis. Posteriorly the artery has the following muscular connections (fig. 78) : — 254 DISSECTION OF THE ARM. Whilst it is inside the humerus it is placed over the long head of the tri- ceps F, for two inches, but separated partly by the musculo-spiral nerve and profunda vessels; and over the inner head, G, of the same muscle for about an inch and a half. But when the vessel turns to the front of the bone, it lies on the insertion of the coraco-brachialis, c, and on the brachi- alis anticus, n. To the outer side are laid the coraco-brachialis and biceps muscles, c, and b, the latter overlapping it. Veins. VemTe comites lie on the sides of the artery (fig. 78, c?), encir- cling it with branches, and the median basilic vein crosses over it at the elbow. The basilic vein is near, and inside the artery above, but is suj)erficial to the fascia in the lower half of the arm. The nerves in relation with the artery are the following: — The internal cutaneous (^) is in contact with the vessel until it perforates the fascia about the middle of the arm. The ulnar nerve (^) lies to the inner side as far as the insertion of the coraco-brachialis muscle; and the musculo- spiral (fig. 69, is behind for a distance of two inches. The median nerve (*) is close to the vessel throughout, but alters its position in this way : — as low as the insertion of the coraco-brachialis it is placed on the outer side, but it then crosses obliquely either over or under the artery, and becomes internal about two inches above the elbow joint. Peculiarities in position. The brachial trunk may leave the inner border of the biceps in the lower half of the arm, and course along the intermuscular septum, wdth or without the median nerve, to the inner condyle of the humerus. At this spot the vessel is directed to its ordinary position in front of the elbow, either through or beneath the fibres of the pronator teres, which has then a wide origin. In this unusual course the artery lies behind a projecting bony point of the hu- merus. Muscular covering. In some bodies the humeral artery is covered by an addi- tional slip of origin of the biceps, or of the brachialis anticus muscle. And some- times a slip of the brachialis may conceal, in cases of high origin of the radial, the remainder of the arterial trunk continuing to the forearm. Branches spring both externally and internally from the brachial artery (fig. 77). Those on the outer side, muscular., supply the coraco-brachi- alis, biceps, and brachialis anticus; those on the inner side are named superior and inferior profunda, nutritious, and anastomotic. The superior profunda branch (^) is larger than the others, and leaves the artery near the lower border of the teres major; it winds backwards with the musculo-spiral nerve to the triceps muscle, and will be dissected with the back of the arm. The inferior profunda branch (®) arises opposite the coraco-brachialis muscle, and accompanies the ulnar nerve to the interval between the olecranon and the inner condyle of the humerus. There it anastomoses with the posterior ulnar recurrent and anastomotic branches, and sup- ])lies the triceps. It arises often in common with the superior profunda artery. A nutritious artery of the bone shaft begins near the preceding branch, and enters the large aperture about the middle of the humerus; it is dis- tributed to the osseous and the medullary substance. The anastomotic branch (’) arises one to two inches above the elbow, and courses inwards through the intermuscular septum to the hollow be- tween the olecranon and the inner condyle of the humerus. Here the artery inosculates with the inferior profunda and posterior ulnar recurrent branches, and gives twigs to the triceps muscle: one of the offsets forms NERVES OF THE ARM. 255 fin a,rch across the back of the humerus with a branch of the superior pro- funda. In front of the elbow joint the anastomotic branch sends an offset to the ]n-onator teres muscle: this joins the anterior ulnar recurrent branch. Vasa aherrantia. Occasionally long slender vessels connect the bra- chial or the axillary trunk with the radial artery ; the accessory vessel very rarely ends in the ulnar artery. The BRACHIAL VEINS (fig. 78, d) accompany the artery, one on each side, and have branches of communication across that vessel; they receive contributing veins corresponding with the brandies of the arteries. Su- periorly they unite into one, wliich joins the axillary vein near the sub- scapular muscle. Nerves of the Arm (fig. 78). The nerves on the front of the arm are derived from the terminal cords of the brachial plexus. Few of tlieni furnish offsets above the elbow, but they are continued, for the most part without branching, to the forearm and the hand. The cutaneous branches of some of them have been referred to (p. 250). Fig. 78. Muscles and Deed Vessels and Nervi.s Muscles : A. Pectoralis major. B. Biceps. c. Coraco-brachialis. D and e, Latissimus and teres. F. Long head of the triceps, c. Inner head of triceps. H. Brachialis auticus. OF the Arm. (Illustrations of Dissections.) Nerves : 1. Median. 2. Internal cutaneous. .3. Nerve of Wrisberg. 4. Ulnar. 5. Muscular to the triceps. 6. Internal cutaneous from the musculo-spiral. The median nerve (’ ) arises from tlie brachial plexus by two roots, one from the outer, and the other from tlie inner cord (p. 236). Its destina- tion is to the palm of the hand; and it accompanies the brachial artery to the forearm. Beginning on the outer side of the artery, the nerve crosses over or under it about the middle of the arm, and is placed on tlie inner side a little above the elbow. It does not give any bianch in the arm; but there may be a fasciculus connecting it with the musculo-cuta- neous nerve. Its connections- with muscles are the same as those of the artery. The ulnar nerve (*), derived from the inner cord of the brachial plexus, 25G DISSECTION OF THE ARM. ends jit the inner side of the hand. In the arm the nerve lies at first close to the inner side of the axillary, and the brachial artery, as far as the insertion of the coraco-braehialis ; then leaving the bloodvessel, it is di- rected inwards through the inner intermuscular septum to the interval be- tween the olecranon and the inner condyle, being surrounded by the mus- cular fibres of the triceps. There is not any branch from the nerve till it reaches the elbow-joint. The internal cutaneous (‘^) is a tegumentary nerve of the forearm, to which it is prolonged like the others. Arising from the inner cord of the plexus, it is at first superficial to the humeral artery as far as the middle of the arm, where it divides into two branches that perforate the investing fascia and reach the forearm (p. 250). Near the axilla it furnishes a small cutaneous offset to the integuments of the arm. The small internal cutaneous nerve Q) (nerve of AYrisberg) arises with the })receding. Concealed at first by the axillary vein, it is directed in- wards beneath (but sometimes through) that vein, and joins with the inter- costo-humeral nerve. Afterwards it lies along the inner part of the arm as far as the middle, where it perforates the fascia to end in the integu- ment (p. 251). The musculo-cutaneous nerve (nerv. perforans, Casserii), named from sup])lying muscles and integuments, ends on the surface of the forearm. It leaves the outer cord of the brachial plexus opposite the lower border of the pectoralis minor (fig. 70) and perforates directly the coraco-brach- ialis : it is then directed obliquely to the outer side of the limb between the biceps and brachialis anticus muscles. Near the elbow it becomes a cutaneous nerve of the forearm. Branches. The nerve furnishes branches to the muscles in front of the humerus, viz., to the coraco-brachialis as it passes through the fibres, and to the biceps and brachialis anticus where it is jdaced between them. Dissection. The brachialis anticus muscle will be brought into view by cutting through the tendon of the biceps near the elbow, and turning upwards this muscle. The fascia and areolar tissue should be taken from the fleshy fibres ; and the lateral extent of the muscle should be well de- fined on each side, so as to show that it reaches the intermuscular septum largely on the inner side, but only for a short distance above on the outer side. Some care is required in detaching the brachialis externally from the muscles of the forearm, to which it is closely applied. As the muscles are separated the musculo-spiral nerve with a small artery comes into sight. The BRACHIALIS anticus (fig. 78, covers the elbow-joint, and the lower half of the front of the humerus. It arises from the anterior sur- face of the humerus below the insertion of the deltoid muscle ; and from the intermuscular septa on the sides, viz., from all the inner, but from only the upper part of the outer (about one inch and a half.) The flesliy fibres converge to a tendon, which is inserted into the impression on the front of the coronoid process of the ulna (p. 271). This muscle is concealed by the biceps. On it lies the brachial artery, with the median, musculo-cutaneous, and musculo-spiral nerves. It covers the humerus and the articulation of the elbow. Its origin embraces by two })arts the attachment of the deltoid ; and its insertion is placed between two fleshy pieces of the flexor profundus digitorum. The inner border reaches the intermuscular septum in all its length ; but the outer is sepa- rated from the external intermuscular septum below by two muscles of TRICEPS EXTENSOR OF MUSCLE. 257 the forearm (supinator longus and extensor carpi radialis longior), which extend upwards on the humerus. Action. The brachialis brings forwards the ulna towards tlie humerus, and bends the elbow-joint. If the ulna is fixed, as in climbing with the hands above the head, the muscle bends the elbow-joint by raising the humerus. BACK OF THE ARM. Position. During the examination of the back of the arm, the limb is to be raised in a semiflexed position by means of a block beneath the elbow. The scapula is to be brought nearly in a line with tlie humerus, so as to tighten tlie muscular fibres ; and it is to be fastened with hooks in that position. Fig. 79. Muscles : A. Long head of the triceps. B. Outer head, with a bit of whalebone beneath it to mark the extent of its attachment down the humerus. c. Inner head of the triceps. D. Anconeus. E. Supinator longus. F. Extensor carpi radialis longus. G. Teres major. H. Teres minor. X. Infra-spinatus, cut across, j. Supra-spinatus, cut through. Arteries : a. Supra-scapular. h. Dorsal scapular, c. Posterior circumflex. Nerves : I. Supra-scapular. 2. Posterior circumflex. Dissection of the Dorsal Scapular Vessels and Xerve, and of the Triceps Muscle OF the Arm. Dissection (fig. 79). On the back of the arm there is one muscle, the triceps, with the musculo-spiral nerve and superior profunda vessels. The skin having been reflected already, the muscle will be laid bare readily, for it is covered only by fascia. To take away the fascia, carry an inci- sion along the middle of the limb to a little below the elbow ; and in reflect- ing it, the subaponeurotic loose tissue should be removed at the same time. 17 258 DISSECTION OF THE ARM. Separate tlie middle from the inner and outer heads of the muscle, and trace the musculo-S})iral nerve and vessels beneath it. Define the outer head which reaches down to the spot at which the musculo-spiral nerve appears on the outer side. The TRICEPS MUSCLE (fig. 79), is divided superiorly into three parts or heads of origin, inner, outer, and middle :• two of these are attached to the humerus, and one to the scapula. The middle piece, or head, a, is the longest, and has a tendinous origin, about an inch wide, from the inferior costa of the scapula close to the glenoid cavity, where it is united with the capsule of the shoulder joint. The outer head, b, is narrow and arises from the back of the humerus above the spiral groove, extending from the root of the large tuberosity to that groove. The inner head, c, fleshy and wide, arises from the posterior surface of the humerus below the spiral groove, reaching laterally to the intermuscular septa, and gradually tapeidng upwards as far as the insertion of the teres major (Theile). From the different heads the fibres are directed with varying degrees of inclination to a common tendon at the lower part. Interiorly the muscle is inserted into the end of the ole- cranon process of the ulna, and gives an expansion to the a})oneurosis of the forearm. Between the tip of the olecranon and the tendon is a small bursa. The triceps is superficial, except at the upper part where it is overlapped by the deltoid muscle. It lies on the humerus, and conceals the musculo- S])iral nerve, the superior profunda vessels, and the articulation of tlie elbow. On the sides the muscle is united to the intermuscular septa ; and the lower fibres are continuous externally with the anconeus — a muscle of the forearm. Action. All the parts of the triceps combining in their action will bring the ulna into a line with the humerus, and extend the elbow-joint. As the long head passes the shoulder it can depress the raised humerus, and adduct the bone to the thorax. The intermuscular septa are fibrous processes continuous with the in- vesting aj)oneurosis of the arm, which are fixed to the ridges leading to the condyles of the humerus : they intervene between the muscles on the front an(l back of the limb, and give attachment to fleshy fibres. The internal is the strono-est, and reaches as high as the coraco-brachialis muscle, from which it receives some tendinous fibres. The brachialis an- ticus is attached to it in front, and the triceps behind ; and the ulnar nerve, and the inferior j)rofunda and anastomotic vessels pierce it. Tiie external se[)tum is thinner, and ceases at the deltoid muscle. Be- hind it is the triceps ; and in front are the brachialis anticus, and the muscles of the forearm (supinator longus and extensor carpi radialis longus) arising above tlie condyle of the humerus : it is pierced by the musculo-spiral nerve and the accompanying vessels. Dissection. To follow the su})erior profunda vessels and the musculo- spiral nerve, the middle head of the triceps should be cut across over them, and tlie fatty tissue should be removed. The trunks of the artery and nerve are to be afterwards followed below the outer head of the triceps to the front of tlie humerus. To trace out the branches of the nerve and artery, whicli descend to the olecranon and tlie anconeus muscle, the triceps is to be divided along tlie line of union of the outer witli the middle liead. The superior profunda branch of the brachial artery (p. 254) turns to MUSCULO-SPIRAL NERVE. 259 the back of the humerus between the inner and outer heads of the triceps; in this position it supplies branches to the triceps and deltoid muscles, and is continued onwards in the groove in the bone to the outer part of the arm, where it divides into its terminal offsets : — One of these, which is very small, courses on the musculo-spiral nerve to the front of the elbow, anastomosing with the recurrent radial branch : whilst others continue along the intermuscular septum to the elbow, and join the radial and pos- terior interosseous recurrent branches. Branches. Most of the muscular offsets of the vessels descend to the olecranon, supplying the triceps, and communicate with the inferior pro- funda and anastomotic branches of the bracliial artery (p. 254) ; and with the recurrent branches of the arteries of the forearm except the anterior ulnar. One slender offset accompanies a branch of the musculo-spiral nerve, and ends in the anconeus muscle below the outer condyle of the humerus. Two or more cutaneous offsets arise on the outside of the arm, and accompany the superficial nerves. The musculo-sjnral nerve (fig. 70) is the largest trunk of the posterior cord of the brachial plexus (p. 236) and is continued along the back and outer part of the limb to the hand. In the arm the nerve winds with the profunda artery beneath the triceps muscle. At the outer aspect of the arm it is continued between the brachialis anticus and supinator longus muscles to the external condyle of the humerus, in front of which it divides into the radial and posterior interosseous nerves. The nerve gives muscu- lar branches, and the following cutaneous offsets to the inner and outer parts of the limb. a. The internal cutaneous branch of the arm (fig. 78, ®) is of small size, and arises in the axillary space in common with the branch to the inner head of the triceps ; it is directed across the posterior boundary of the axilla to the inner side of the arm, where it becomes cutaneous in the upper third, and is distributed as before said (p. 250). b. The external cutaneous branches springing at the outer side of the limb are two in number : they are distributed in the integuments of the arm and forearm (p. 250). c. The muscular branches to the triceps are numerous, and supply all three heads. One slender offset for the inner head, arises in common with the inner cutaneous branch, and lies close to the ulnar nerve till it enters the muscular fibres at the lower third of the arm. Another long and slender branch behind the humerus, appearing as if it ended in the triceps, can be followed downwards to the anconeus muscle. d. On the outer side of the limb the musculo-spiral nerve supplies the brachialis anticus in part, and two muscles of the forearm, viz., supinator longus and extensor carpi radialis longior. Buhanconeus muscle. A thin fleshy stratum of the under part of tl.e triceps near the elbow has been so named. It is described as consisting of two fasciculi, inner and outer, which are attached above the fossa for the olecranon, and end in the synovial sac of the joint. A corresponding muscle is placed beneath the extensor of the knee joint. Action. It is said to raise the synovial membrane in extension of the joint. Directions. As the dissection of the arm has been completed as far as the elbow, it will be advisable to keep moist the shoulder joint until it is examined with the other ligaments. 260 DISSECTION OF THE FRONT OF THE FOREARM. Section IV. THE FRONT OF THE FOREARM. Position. The limb is to be placed with the palm of the hand upper- most ; and the marking of the surface, and the projections of the bone, are first to be noted. Surface-marking. On the anterior aspect of the forearm are two lateral depressions, corresponding with the position of the main vessels. The external is placed over the radial artery, and inclines towards the middle of the limb as it approaches the elbow. The internal groove is evident only beyond the middle of the forearm, and points out the place of the ulnar artery. The bones (radius and ulnar) are sufficiently near the surface to be traced in their whole length : each ends below in a point — the styloid process ; and that of the radius is the lowest. A transverse line separates the forearm from the hand, and the articulation of the wrist is about an inch above it. On each side of the palm of the hand is a lateral projection ; the exter- nal of these (thenar) is formed by muscles of the thumb, and the internal (hypo-thenar) by muscles of the little finger. Between the projections is the hollow of the palm, which is pointed towards the wrist. Two trans- verse lines are seen in the palm, but neither reaches completely across it : the anterior one will direct to the line of the articulations between the metacarpus and the phalanges, but is about a quarter of an inch behind the three inner joints when the fingers are extended. The superficial palmar arch of arteries reaches forwards a little way into the hollow of the hand, and its position may be marked by a line across the palm from the root of the thumb, when that digit is placed at a right angle to the hand. Transverse lines are seen on both aspects of the joints of the thumb and fingers. The lines on the palmar surface of the fingers may be used to detect the articulations of the phalanges. Thus the joint between the metacarpal phalanx and the next will be found about a line in front of the chief transverse groove ; whilst the articulation between the last two pha- langes is situate about a line in front of the single mark. Dissection. AVith the limb lying flat on the table, an incision is to be carried through the skin along the middle of the front of the forearm, as far as an inch beyond the wrist ; and at its termination a transverse one is to cross it. The skin is to be reflected carefully from the front and back of the forearm, without injury to the numerous superficial vessels and nerves beneath ; and it should be taken also from the back of the hand, by prolonging the ends of the transverse cut along each margin to a little beyond the knuckles. The whole of the forefinger should have the integ- ument removed from it, in order that the nerves may be followed to the end. The superficial vessels and nerves can be now traced in the fat ; they have the following position, and most of them have been partly dissected ; Along the inner side, in front of the forearm with the ulnar veins, is the continuation of the internal cutaneous nerve ; and near the wrist there is CUTANEOUS VEINS OF FOREARM. 261 occasionally a small offset from the ulnar nerve. On the outer side with the radial vein is the superficial part of the musculo-cutaneous nerve. Close to the hand, in the centre of the forearm, and inside the tendon of the flexor carpi radialis which can be rendered prominent by extending the wrist, the small palmar branch of the median nerve should be sought beneath the fat. On the ulnar artery, close inside the pisiform bone, a small palmar branch of the ulnar nerve is to be looked for. At the back of the forearm the largest external cutaneous branch of the musculo-spiral nerve is to be traced onwards ; and offsets are to be followed to this surface from the nerves in front. On the posterior part of the hand is an arch of superficial veins. Wind- ing back below' the ulna is the dorsal branch of the ulnar nerve ; and lying along the outer border of the hand is the radial nerve : these should be traced to the fingers. Cutaneous Veins. The superficial veins are named median, radial, and ulnar, from their position in the limb. Superficial arch on the back of the hand. This arch is more or less per- fect, and receives the posterior superficial digital veins. At the sides the arch terminates in the radial and ulnar veins. The radial vein begins in the outer part of the arch above mentioned, and in some small radicles at the back of the thumb. It is continued along the forearm, at first behind and then on the outer border as far as the elbow'^, where it gives rise to the cephalic vein by its union with the outer branch of the median vein (fig. 76, ^). The ulnar veins are anterior and posterior, and occupy the front and back of the limb : — The anterior arises near the w^rist by the junction of small roots from the hand, and runs on the inner part of the forearm to the elbow ; here it unites with the inner branch of the median, and forms the basilic vein (fig. 76, ^). posterior ulnar vein is situate on the back of the limb. It com- mences by the union of a branch, vena salvatella,” from the back of the little finger, with an offset of the venous arch ; it is continued along the back of the forearm nearly to the elbow, and bends forwards to open into the anterior ulnar vein. The median vein takes origin near the wTist by small branches which are derived from the palmar surface of the hand ; and it is directed along the centre of the forearm nearly to the elbowu Here the vein divides into external and internal branches (median basilic and median cephalic), wdiich unite, as before seen (fig. 76, ^), with radial and ulnar veins. At its point of bifurcation the median receives a communicating branch from a vein (vena comes) beneath the fascia. Cutaneous Nerves. Some of the superficial nerves of the forearm are continued from the arm : — those on the inner side from the large in- ternal cutaneous nerve ; and those on the outer, from the two external cutaneous nerves of the musculo-spiral, and the musculo-cutaneous. On the forepart of the limb there is occasionally a small offset of the ulnar nerve near the wrist. On the back of the hand is the termination of the radial nerve, together with a branch of the ulnar nerve. The internal cutaneous nerve (p. 256) is divided into two parts. The anterior branch extends on the front of the forearm as far as the wudst, and supplies the integuments on the inner half of the anterior surface. Near the wrist it communicates sometimes with a cutaneous offset from 262 DISSECTION OF THE FRONT OF THE FOREARM. the ulnar nerve. The posterior branch continues along the back of the forearm (ulnar side) to rather below the middle. The cutaneous part of the musculo-cutaneous nerve (p. 2o6) is pro- longed on the radial border of the limb to the ball of the thumb, over which it terminates in cutaneous offsets. Near the wrist the nerve is placed over the radial arterj, and some twigs pierce the fascia to ramify on the vessel and supply the carpus. A little above the middle of the forearm the nerve sends backwards a branch to the posterior aspect, which reaches nearly to the wrist, and communicates with the radial, and the following cutaneous nerve. The external cutaneous branch of the musculo-spiral nerve (p. 259) after passing the elbow, turns to the hinder part of the forearm, and reaches as far as the wrist. Near its termination it joins the preceding cutaneous nerve. The radial nerve ramifies in the integument of the back of the hand and some of the digits. It becomes cutaneous at the outer border of the forearm in the lower third, and after giving some filaments to the poste- rior aspect of the limb, divides into two branches : — One (external) is joined by the musculo-cutaneous nerve, and is dis- tributed on the radial border and the ball of the thumb. The other brauch (internal) supplies the remaining side of the thumb, both sides of the next two digits, and half the ring finger ; so that the radial nerve distributes the same number of digital branches to the dorsum as the median nerve furnishes to the palmar surface. This portion of the radial nerve communicates with the musculo-cutaneous and ulnar nerves ; and the offsets to the contiguous sides of the ring and middle fingers is joined by a twig from the dorsal branch of the ulnar nerve. On the side of the fingers each of these dorsal digital branches is united with an offset from the digital nerve on the palmar surface. The dorsal branch of tlie ulnar nerve gives offsets to the rest of the fingers and the back of the hand. Appearing by the styloid process of the ulnar, it joins the radial nerve in an arch across the back of the liand, and is distributed to both sides of the little finger, and to the ulnar side of the ring finger : it communicates with the part of the radial nerve supplying the space between the ring and middle fingers. The ulnar nerve furnishes branches to the same digits on the palmar surface. The aponeurosis of the forearm is continuous with a similar investment of the arm. It is of a pearly wliite color, and is formed of fibres whicli cross obliquely : it furnishes sheaths to the muscles, and is thicker behind than before. Near the elbow it is stronger than towards the hand; and at that part it receives fibres from the tendons of the biceps and brachialis anticus, and gives origin to the muscles attached to the inner condyle of the humerus. On the back of the limb the aponeurosis is connected to the margins of the ulna, so as to leave the upper part of the bone subcutaneous ; and it is joined by fibres from the tendon of the trice})S. Horizontal })rocesses are sent downwards from the aponeurosis to sepa- rate the superficial and deep layers of muscles, both on the front and back of tlie forearm ; and longitudinal white bands indicate tlie position of the intermuscular processes which isolate one muscle from anotlier, and give origin to the muscular fibres. At tlie wrist tlie fascia joins the anterior annular ligament ; and near that band the tendon of the palmaris longus pierces it, and receives a sheath APONEUROSIS OF FOREARM. 268 from it. Close to the pisiform bone there is an aperture througli whicli the ulnar vessels and nerve enter the fat of tlie hand. Beliind the wrist it is thickened by transverse fibres, giving rise to the posterior annular ligament ; but on the back of the hand and fingers the fascia becomes very thin. Dissection. The skin is to be replaced on the back of the forearm and hand, in order that the denuded parts may not become dry. Beginning the dissection on the anterior surface of the limb, let the student divide the aponeurosis as far as the wrist, and take it away with the cutaneous vessels and nerves, except the small j)almar cutaneous offsets of the median and ulnar nerves near the wrist. In cleaning the muscles it will be impossible to remove the aponeurosis from them at the upper part of the forearm without detaching muscular fibres. In front of the elbow is the hollow, already partly dissected, between the two masses of muscles arising from the inner and outer sides of the humerus. The space should be carefully cleaned, so as to display the brachial and forearm vessels, the median nerve and branches, the musculo- spiral nerve, and the recurrent radial and ulnar arteries. In the lower half of the forearm a large artery, radial, is to be laid bare along the radial border ; and at the ulnar side, close to the annular liga- ment, the trunk of the ulnar artery will be i-ecognized, as it becomes superficial. These vessels and their branches should be carefully cleaned ; but the collateral muscles should be fixed with stitches to prevent their displacement. The anterior annular ligament of the wrist, which arches over the ten- dons [)assing to the hand, is next to be defined. This strong band is at some depth from the surface ; and whilst the student removes the fibrous tissue superficial to it, he must take care of the small branches of the median and ulnar nerves to the palm of the hand. The ulnar vessels and nerve pass over the ligament, and will serve as a guide to its depth. HoUoiv in front of the elbow (fig. 80). This hollow corresponds with the popliteal space at the knee, and is situate between the inner and the outer muscles of the forearm. The interval is somewhat triangular in sha])e, and the wider part is towards the humerus. It is bounded on the outer side by the su{)inator longus muscle, and on the inner side by the pronator teres. The aponeurosis of the limb is stretched over the s])ace ; and the bones, covered by the brachialls anticus and supinator brevis, form the deep boundary. Contents. In the hollow are lodged the termination of the brachial artery with its veins, and the median nerve ; the musculo-S])iral nerve ; the tendon of the biceps muscle ; and small recurrent vessels, .with much fat and a few glands. These several parts have the following relative position : The tendon of the biceps is directed towards the outer boundary to reach tlie radius ; on the outer side, concealed by the supinator longus muscle, is the musculo- spiral nerve. Nearly in the centre of the space are the brachial artery and veins and the median nerve, the nerv^e being internal ; but as the artery is inclined to the outer part of the limb, they soon become distant from one another about half an inch. The brachial artery divides here into two trunks — radial and ulnar ; and the recurrent radial and ulnar branches appear in the space, one on the outer and the other on the inner side. Two or three lymjdiatic glands lie on the sides of the artery, and one below its point of splitting. 264 DISSECTION OF THE FRONT OF THE FOREARM. Fig- 80. Muscles on the front of the forearm (fig. 80). The muscles on the front of the forearm are divided into a superficial and a deep layer. In the superficial layer there are five muscles, which are fixed to the inner condyle of the hu- merus, mostly by a common tendon, and lie in the undermentioned order from the middle to the inner side of the limb : pronator radii teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris ; and deeper and larger than any of these is the flexor sublimis digitorum. The deep layer will be met with in a subsequent dissection (p. 270). Tlie PRONATOR radii’ TERES (fig. 80°,^) arises from the inner condyle of the humerus by the common tendon ; from the ridge above the condyle by fleshy fibres ; from the inner part of the coro- noid process by a second tendinous slip ; and from the fascia, and the septum between it and the next muscle. It is inserted by a fiat tendon into an im- pression, an inch in length, on the middle of the outer surface of the radius. The muscle is superficial except at the insertion, where it is covered by the radial artery, and some of the outer set of muscles, viz., supinator longus, and radial extensors of the wrist. The pronator forms the inner boundary of the triangular space in front of the elbow ; and its inner border touches the flexor carpi radialis. By gently separating the muscle from the rest, it will be found to lie on the brachialis anticus, the flexor sublimis digitorum, and the ulnar artery and the median nerve : the second small head of origin is directed inwards between that artery and nerve. Action. The pronator assists in bringing for- wards the radius over the ulna, so as to pronate the hand. When the radius is fixed the muscle raises that bone towards the humerus, bending the elbow-joint. The FLEXOR CARPI RADIALIS (fig. 80, takes its origin from the common tendon, from the aponeurosis of the limb, and from the intermuscular septum on each side. The tendon of the muscle, becoming free from fleshy fibres about the middle of the forearm, passes through a groove in the os trapezium, outside the anterior annular ligament, to be inserted mainly into the base of the meta- carpal bone of the index finger, and by a slip into that of tlie middle finger. Tlie muscle rests chiefly on the flexor sublimis digitorum ; but near the wrist it lies over the flexor longus poUicis — a muscle of tlie deep layer. As low as the middle of the forearm the muscle corresponds externally with the pronator teres, and Superficial view of the FOREARM (Quain’s Arte- ries). 1. Radial arteiy with its nerve outside. 2. Uluar artery and nerve where they are super- ficial. 3. Pronator teres. 4. Flexor carpi radialis. 5. Palmaris longus. 6. Flexor sublimis. 7. Flexor carpi uluaris. 8. Supinator longus. 9. Biceps. RADIAL ARTERY AND BRANCHES. 265 below that with the radial artery to which its tendon is taken as the guide. The ulnar border is in contact at first with the palmaris longus muscle, and for about two inches above the wrist, with the median nerve.^ Action. The hand being free the muscle flexes first the wrist joint, inclining the hand somewhat to the radial side ; and will assist in bringing forwards the lower end of the radius in pronation. Still continuing to contract, it bends the elbow. The PALMARIS LONGUS (fig. 80, is often absent : or it may present great irregularity in the proportion between the fleshy and tendinous parts. Its origin is connected, like that of the preceding muscle, to the common tendon, the fascia, and the intermuscular se[)ta. Its long thin tendon is continued along the centre of the forearm ; and piercing the aponeurosis, it passes over the annular ligament to end in the palmar fascia, and to join by a tendinous slip the short muscles of the thumb. The palmaris is situate between tlie flexor carpi radialis and ulnaris, and rests on the flexor sublimis digitorum. Action. Rendering tense the palmar fascia, the palmaris will afterwards bend the wrist and elbow, like the other muscles of the superficial layer. The FLEXOR CARPI ULNARIS (fig 80, ’^) has an aponeurotic origin from the inner condyle of the humerus ; from the inner side of the olecranon ; and from the ridge of the ulna between the internal and posterior surfaces for three-fourths of the length. Most of the fibres are continued vertically downwards, but others obliquely forwards to a tendon on the anterior part of the muscle in the lower half, some joining it as low as the wrist ; and the tendon is inserted into the pisiform bone, an offset being sent to the muscles of the little finger. One surface of the muscle is in contact with the fascia ; and its tendon, which can be felt readily through the skin, may be taken as the guide to the ulnar artery. To its radial side are the palmaris and flexor digitorum sublimis muscles. When the attachment to the inner condyle has been divided, the muscle will be seen to conceal the flexor digitorum sublimis and flexor profundus, the ulnar nei*ve, and the ulnar vessels ; between the attachments to the condyle and the olecranon the ulnar nerve enters the forearm. Action. The wrist is bent and the hand is drawn inwards by the con- traction of the muscle. The RADIAL ARTERY (flg. 80, is One of the vessels derived from the bifurcation of the brachial trunk ; and its destination is the palm of the hand. It is placed first along the outer side of the forearm as far as the end of the radius.^ next it winds backwards below the extremity of that bone : and it enters finally the palm of the hand through the first inter- osseous space. In consequence of this circuitous course the artery will be found in three different dissections, viz., the front of the forearm, the back of the wrist, and the palm of the hand. hi the front of the forearm. In this part of the limb the position of the artery will be marked, on the surface, by a line from the centre of the hollow of the elbow to the fore part of the styloid process of the radius. At first it lies on the inner side of the radius, but afterwards over that bone. This vesvsel is smaller than the ulnar artery, though it appears in direction to be the continuation of the brachial trunk ; and it is partly J In the body of a woman which was well developed, the muscle was absent on both sides. 266 DISSECTION OF THE FRONT OF THE FOREARM. deep and partly superficial, but where it is more superficial in the lower half it can be felt beating as the pulse near the wrist during life. In its v'p'per half the vessel is placed beneath the supinator longus (®) ; and rests successively on the following muscles, the fleshy supinator brevis, the pronator teres (^), part of the thin origin of the flexor sublimis (®), and sometimes on the biceps tendon (^). Veins. Venae comites lie on the sides, with cross branches over the artery. Nerve. The radial nerve is parallel to, and outside it, but separated by a slight interval. In its lower /m//’the artery with its venae comites is superficial, being covered only by the teguments and the deep fascia. Here it is placed in a hollow between the tendons of the supinator longus (®) and flexor carpi radicalis (^). It lies from above down on the origin of the flexor sublimis, on two other muscles of the deep layer, viz., flexor pollicis longus and pronator quadratus, and lastly on the end of the radius. Nerves. The radial nerve is still on the outer side until it passes back- Avards beneath the tendon of the supinator longus, and becomes cutaneous. Superficial to the lower end are the ramifications of the musculo-cutaneous nerve, some of Avhich reach the vessels (p. 202). Braiiches. The radial artery furnishes many unnamed muscular and nutrient offsets to the surrounding parts ; and three named branches, viz., recurrent radial, superficial volar, and anterior car|)al. a. The radical recurrent is the first branch, and supplies the muscles of the outer side of the limb. Its course is almost transverse to the supi- nator longus, beneath which it terminates in that muscle and the two radial extensors of the wrist. One offset ascends beneath the supinator, and anastomoses with the su})erior, profunda branch of the brachial artery. b. The superficial volar branch (fig. 83, c) arises usually near the lower end of the radius. It is directed towards the })alm of the hand, across or through the mass of muscles in the ball of the thumb, and it either ends in those muscles, or joins the superficial palmar arch. c. The anterior carpal branch is very inconsiderable in size, and will be seen in the examination of the deep layer of muscles. Arising rather above the end of the radius, it passes transversely at the lower border of the pronator quadratus, and anastomoses with a similar branch fi-om the ulnar artery : from the arch thus formed, offsets are given to the corpus. Pecidiarities of the radial artery. When the radial arises high in the arm, its course is close to the brachial artery, along the edge of the biceps muscle ; and in passing the bend of the elbow it may be occasionally subcutaneous, viz., above the deep fascia, and be liable to injury in venesection. In the forearm it may be likewise subcutaneous and superficial to the supinator longus muscle. Dissection. To bring into view the flexor sublimis digitorum, the flexor carpi radialis and palmaris longus must be cut through near the inner con- dyle of the humerus, and turned to one side. Small branches of the ulnar artery and median nerve may be seen entering the under surfaces of those muscles. For the present, the pronator teres may be left uncut. The FLEXOR DIGITORUAt SUBLIAIIS vel PERFORATUS (fig. 80,®) is the largest of the muscles of the suj)erficial layer, and is named from its posi- tion to another flexor in the deep layer. It arises from the inner condyle of the humerus and the internal lateral ligament, and from the intermus- cular septa in common with other muscles ; it takes origin in addition from ULNAR ARTERY AND BRANCHES. 26T the bones of the forearm, viz., from the inner part of the coronoid process of the ulna ; from the obli(pie line below the radial tubercle ; and from the anterior margin of the radius as far as, or one or two inches below the insertion of the pronator teres. Ratlier below the middle of the forearm tlie muscle ends in four tendons, which are continued beneath the annular ligament and across the hand, to l)e inserted into the middle jdialanges of the fingers, after being perforated by the tendons of the deep flexor. The flexor sublimis is concealed by the other muscles of the superficial layer ; and the radial vessels lie on the attachment to • the radius. Along the inner border is the flexor carpi ulnaris, with the ulnar vessels and nerve. The tendons of the muscle are arranged in pairs before they pass beneath the annular ligament of the wrist ; — the middle and ring finger tendons being anterior, and those of the index and little finger posterior in position. On dividing the coronoid and condyloid attachments, the muscle will be seen to cover two flexors of the deep layer (flexor digitorum pro- fundus and flexor pollicis), the median nerve, and the upper part of the ulnar artery. Action. This flexor bends primarily the middle joint of each finger; and is then able to bring the nearest phalanx towards the palm in consequence of being bound thereto by a sheath. But when the nearest phalanx is fixed by the extensor of the fingers, it remains straight whilst the super- ficial flexor moves the second phalanx. After the fingers are bent the muscle will help in flexing the wrist and elbow joints. The ULNAR ARTERY (fig 81, is the larger of the two branches coming from the bifurcation of the brachial trunk ; and is directed along the inner side of the limb to the palm of the hand, where it forms the superficial palmar arch, and joins offsets of the radial artery. In the forearm the vessel has an arched direction ; and its de[)th from the surface varies in the first and last parts of its course. In the upper half the artery is inclined obliquely inwards from the centre of the elbow to the inner part of the limb, midway between the elbow and wrist. It courses between the superficial and deep layers of muscles, being covered by the pronator teres, flexor carpi radialis, palmaris longus, and flexor sublimis. Beneath it lie the brachialis anticus, for a short distance, and the flexor profundus, c. Veins. Two companion veins are situate on the sides of the artery, and join freely over it. Nerves. The median nerve (^) lies to the inner side of the vessel for about an inch, but then crosses over it to gain the outer side. About the middle of the forearm the ulnar nerve (^) approaches the artery and con- tinues thence on the inner side. In the lower half it has a straight course to the pisiform bone, and is covered by the teguments and fascia, and the flexor carpi ulnaris as far as the wrist. To the outer side are the tendons of the flexor sublimis. Be- neath it is the flexor profundus, c. Veins. Two companion veins accompany the artery, as in the upper part, and are united across it at intervals. Nerves. The ulnar nerve (^) lies close to, and on the inner side of the vessels ; and a small branch (^), sending twigs around the artery, courses to the palm of the hand. On the annular ligament of the wrist the artery has passed through the 268 DISSECTION OF THE FRONT OF THE FOREARM. fascia and lies close to the pisiform bone. The ulnar nerve, with its palmar branch, still accompanies the vessel on the inner side. Ficr. 81 . Muscles : A. Pronator teres. B. Flexor longus pollicis. c. Flexor digitorum per- forans. D. Pronator quadratus. E. Flexor carpi ulnaris. Arteries : a. Radial trunk. b. Cutaneous branch of it to the palm of the hand. G. Ulnar trunk. d. Its recurrent branch. /. Branch with the median nerve. e. Anterior interosseous. g. Brachial trunk. Nerves : 1. Median. 2. Anterior interosseous. 3. Cutaneous palmar branch. 4. Ulnar trunk. 5. Cutaneous palmar branch of ulnar. Dissection op the Deep Layer of Muscles of the Forearm, and op the Vessels and Nerves between the Two Layers of Muscles of the Forearm. (Illustrations of Dissections.) Branches. The greater number of the collateral offsets of the artery are distributed to the muscles. But the named branches are the following : — a. Tiie anterior ulnar recurrent branch (f?) arises generally in common with the next, and ascending on the brachialis anticus muscle inosculates witli the small anastomotic artery beneath the pronator radii teres. It gives oflsets to the contiguous muscles. ULNAR NERVE. 269 h. The posterior ulnar recurrent branch (c?), of larger size than the anterior, is inclined beneath the flexor sublimis muscle to the interval between the inner condyle and the olecranon. There it passes with the ulnar nerve between the attachments of the flexor carpi ulnaris, and joins the ramifications of the inferior profunda and anastomotic arteries on the inner side of the elbow joint. Some of its offsets enter the muscles, and others supply the articulation and the ulnar nerve. c. The interosseous branch is a short thick trunk, about an inch long, which is directed backwards towards the interosseus membrane, and divides into anterior and posterior interosseous : these branches will be afterwards followed. ^ d. The metacarpal branch arises from the artery near the lower end of the ulna, and runs along the metacarjml bone of the little finger, of which it is the inner dorsal branch. e. The carpal branches (anterior and posterior) ramify on the front and back of the carpus, on which they anastomose with corresponding offsets of the radial artery, and form arches across the wrist. Peculiarities of the ulnar artery. The origin of the artery may be transferred to any point of the main vessel in the arm or axilla. Once the origin was found between two and three inches below the elbow. (Quain.) When it begins higher than usual it is generally superficial to the flexor muscles at the bend of the elbow (only one exception, Quain), but beneath the aponeurosis of the forearm ; though sometimes it is subcutaneous with the super- ficial veins. The ULNAR NERVE (fig. 81, ^) enters the forearm betw'een the attach- ments of the flexor carpi ulnaris to the olecranon and inner condyle of the humerus. Under cover of that muscle the nerve reaches the ulnar artery about the middle (in length) of the forearm, and is continued on the inner side of the vessel to the hand. On the annular ligament the nerve is rather deeper than the artery. It furnishes articular, muscular, and cutaneous branches as below : — a. Articular nerves. In the interval between the olecranon and the inner condyle, slender filaments to the joint arise. h. Muscular branches. It furnishes offsets near the elbow to two muscles of the forearm ; one enters the upper part of the flexor carpi ulnaris, and the other supplies the inner half of the flexor profundus digitorum. c. Cutaneous nerve of the forearm and hand. About the middle of the forearm arises a small palmar branch (®), which courses on the ulnar artery, sending twigs around that vessel, to the end in the integuments of the palm of the hand : sometimes a cutaneous offset perforates the aponeu- rosis near the wrist, and joins the internal cutaneous nerve. d. The dorsal cutaneous nerve of the hand arises about two inches above the end of the ulna, and passes obliquely backwards beneath the flexor carpi ulnaris : perforating the aponeurosis it is lost on the back of the hand and fingers (p. 262). The MEDIAN NERVE (fig. 81, ^) leaves the hollow of the elbow between the heads of origin of the pronator teres, and takes the middle line of the limb to the hand. It is placed beneath the flexor sublimis as low as two inches from the annular ligament, where it becomes superficial along the outer border of the tendons of that muscle. Lastly the nerve passes be- neath the annular ligament to the palm of the hand. The nerve supplies 270 DISSECTION OF THE FRONT OF THE FOREARM. the mnscles on the front of the forearm, and furnishes a cutaneous offset to the hand. 05. Muscular offsets leave the trunk of the nerve near the elbow, and are distributed to all the muscles of the superficial layer except the flexor carpi ulnaris ; in addition, the nerve supplies the deep layer through the interosseous branch (p. 271), except the inner half of the flexor profun- dus digitorum. b. The cutaneous 'palmar branch (^) arises in the lower fourth of the forearm ; it pierces the fascia near the annular ligament, and crosses over that ligament to reach the ])alm of the hand. The RADIAL NERVE is the smaller of the two branches into which the musculo-spiral divides at the elbow. This nerve is placed along the outer border of the limb, under cover of the supinator longus (fig. 80), and on the outer side of the radial artery till within three indies of the wrist, where it becomes cutaneous at the posterior border of the supinator tendon. On the surface of the limb it divides into two branches, which are dis- tributed on the dorsum of the hand, and digits (3^) (p. 2G2). No muscular offset is furnished by the nerve. Dissection (fig. 81). To examine the deep layer of muscles it will be necessary to draw well over to the radial side of the forearm the pronator teres ; to detach the flexor sublimis from the radius, and to remove its fleshy part. The areolar tissue is to be taken from the deep muscular fibres ; and the anterior interosseous vessels and nerve, which lie on the interosse- ous membrane, and are concealed by the muscles, are to be traced out. Above the ends of the forearm-bones the arch of the anterior carpal arteries may be defined. Deer Layer of Muscles. Only three deep muscles are present on the front of the forearm. One lies on the ulna, and is the deep flexor of the fingers; a second covers the radius, viz., the long flexor of the thumb; and the third is the pronator quadratus, which lies beneath the other two, near the lower end of the bones. The FLEXOR DIGITORUM PROFUNDUS Vel PERFORANS (fig. 81, ^) ariseS from the anterior and inner surfaces of the ulna for three-fourths of the length of the bone ; from the inner half of the interosseous ligament for the same distance ; and from an aponeurosis common to the muscle and the flexor carpi ulnaris. The muscle has a thick flesliy belly, and ends in tendons which, united together, pass beneath the annular ligament, and are inserted into the last phalanges of the fingers. The cutaneous surface of the muscle is in contact with the ulnar nerve and vessels, the superficial flexor of the fingers, and the flexor carpi ulna- ris. Tlie deep surface rests on the ulna and the pronator quadratus mus- cle. The outer border touches the flexor pollicis longus and the anterior interosseous vessels and nerve ; and the inner is connected by aponeurosis to the posterior margin of the ulna. Action. The muscle bends the last joints of the fingers and the wrist ; but it does not act on the last plialanx till after the second has been moved by the flexor sublimis. The fingers are approximated and the joints bent In the following order: — first, the articulation between the metacarpal and the middle phalanx is flexed, secondly, the last phalangeal joint, and thirdly the metacarpo-pha- langeal. The FLEXOR LONGUS POLLICIS (fig. 81,®) from the hollowed an- terior surface of the radius, as low as the pronator quadratus ; from the DEEP LAYER OF MUSCLES. 271 outer part of tlie interosseous membrane ; and by a round distinct slip from the coronoid process of the ulna, internal to the attachment of the brachi- alis anticus. Tlie fleshy fibres descend to a tendon, which is continued beneath the annular ligament, and is inserted into the last phalan:<^of the thumb. On the cutaneous surface of the muscle is the flexor sublimis, with the radial vessels for a short distance inferiorly. The muscle lies on the radius and the pronator quadratus. To the inner side is the flexor profundus digitorum. Action. It bends both joints of the thumb, but first the distal or un- gual. After the phalanges are drawn downwards the muscle flexes the wrist. The PRONATOR QUADRAtus (fig. 81, is a flat muscle, and lies on tlie lower fourth of the bones of the forearm. It arises from the anterior and inner surfaces of the ulna, where it is somewhat widened, and is inserted into the forepart of the radius for about two indies. Tlie anterior surface is covered by the tendons of the flexor muscles of the fingers, and by the radial vessels ; and the posterior surface rests on the radius and ulna with the intervening membrane, and on the interosse- ous vessels and nerve. Along its lower borders is the arch formed by the anterior carpal arteries. Action. The end of the radius is moved forwards over the ulna by this muscle, and the hand is pronated. The anterior interosseous artery (fig. 81, e) is continued on the front of the interosseous membrane, between the two flexors or in the fibres of the flexor digitorum, till it reaches an aperture beneath the pronator quadratus. At tliat spot the artery turns from the front to the back of the limb, and descends to the back of the carpus, where it ends by anastomosing with the posterior interosseous and carpal arteries. Branches. Numerous offsets are given to the contiguous muscles. a. One long branch (/), median.^ accompanies the median nerve, sup- plying it, and either ends in the flexor sublimis, or extends beneath the annular ligament to the palmar arch. h. About the middle of the forearm two nutrient vessels of the radius and ulna arise from the artery. c. Where it is about to pass through the interosseous membrane it fur- nishes twigs to the pronator quadratus ; and one branch is continued be- neath that muscle to anastomose with the anterior carpal arteries. The anterior interosseous nerve is derived from the median (fig. 81, ^), and accompanies the artery of the same name to the pronator quadratus muscle, the under surface of which it enters. Some lateral branches are distributed by it to the deep flexor muscles. Dissection. The attachment of the biceps and brachialis anticus to the bones of the forearm may be now cleaned and examined. The insertion of the brachialis anticus takes place by a broad thick tendon, about an inch in length, which is fixed into the coronoid process of the ulna, except at the inner edge ; and into the contiguous rough part of the bone. Insertion of the biceps. The tendon of the biceps is inserted into the inner part of the tubercle of the radius, and slightly into the bone behind it. A bursa intervenes between it and the fore[)art of the tubercle. At its attachment the anterior surface becomes external ; and the opposite. The supinator brevis muscle partly surrounds the insertion. DISSECTION OF THE HAND. 272 Section Y. THE PALM OF THE HAND. Dissection (fig. 83). The digits being separated and fixed firmly with tacks, the skin is to be reflected from the palm of the hand by means of two incisions. One is to be carried along the centre from the wrist to the fingers ; and the other is to be made from side to side, at the termination of the first. In raising the inner flap, the small palmaris brevis muscle will be seen at the inner margin of the hand ; and its insertion into the skin may be left till the muscle has been learnt. In the fat the ramifica- tions of the small branches (palmar) of the median and ulnar nerves are to be traced. The student should remove the fat from the palmaris muscle, and from the strong palmar fascia in the centre of the hand ; and he should take care not to destroy a transverse fibrous band (transverse ligament) which lies across the roots of the fingers. When cleaning the fat from the palmar fascia he will recognize, near the digits, the digital vessels and nerves ; and must be especially careful of two, — viz., those of the inner side of the lit- tle finger and outer side of tlie index finger, which appear farther back than the rest, and are most likely to be injured. By the side of the vessels and nerves to the fingers four slender lumbricales muscles are to be defined. Lastly, the skin and the fat may be reflected from the thumb and fingers by an incision along each, in order that the sheaths of the tendons with the collateral vessels and nerves may be laid bare. Cutaneous 'palmar nerves. Some unnamed twigs are furnished to the integument from both the median and ulnar nerves in the hand ; and two named cutaneous nerves ramify in the palm. One is an offset of the median nerve (p. 270), and crosses the annular ligament : it extends to about the middle of the palm, and is united with the palmar branch of the ulnar : a few filaments are furnished to the ball of the thumb. The other palmar branch is derived from the ulnar nerve (p. 269) ; it has been traced on the ulnar artery to the hand, and its distribution in the palm may be now observed. The PALMARIS BREVIS (fig. 83, ®) is a small subcutaneous muscle, about two inches wide, whose fibres are collected into separate bundles. It is attached on the outer side to the palmar aponeurosis, and its fibres are di- rected inwards to join the skin at the inner border of the hand. This muscle lies over the ulnar artery and nerve. After it has been ex- amined it may be thrown inwards with tlie skin. Action. Drawing inwards the skin of the inner border of the hand to- wards the centre, it deepens the hollow or cup of the palm. The palmar fascia or aponeurosis consists of a central and two lateral parts ; but the lateral, which cover the muscles of the thumb and little finger, are so thin as not to require separate notice. The central part is a strong, white layer, which is pointed at the wrist, but is expanded towards the fingers, where it nearly covers the palm of the hand. Posteriorly the fascia receives the tendon of the palmaris longus, and is connected to the annular ligament ; and anteriorly it ends in four ULJ^AR VESSELS AND NERVE. 273 processes, which are continued forwards, one for each finger, to the sheaths of the tendons. At tlie point of separation of the processes from one an- other some transverse fibres are placed, which arch over the lumhricalis muscle, and the digital artery and nerve ap))earing at this spot. From the pieces of the fascia a few superficial longitudinal fibres are prolonged to the integuments near the cleft of the fingers. Dissection. To follow one of the digital processes of the fascia to its termination, the superficial fibres being first removed, it must be divided longitudinally by inserting the knife beneath it opposite the head of the metacarpal bone. Ending of the processes. Each process of the fascia sends downwards an offset on each side of the tendons, which is fixed to the deep ligament connecting together the ends of the metacarpal bones, and to the edge of the metacarpal bone for a short distance. The superficial transverse ligament of the fingers is a thin fibrous band, which stretches across the roots of the four fingers, and is contained in the fold of skin forming the rudiment of a web be- tween them. Beneath it the digital nerves and vessels are continued onwards to their termina- tions. Sheath of the flexor tendons (fig. 82). Along each finger the flexor tendons are retained in posi- tion against the phalanges by a fibrous sheath. Opposite the middle of each of the two nearest phalanges the sheath is formed by a strong fibrous band {e and f) (ligamentum vaginale), which is almost tendinous in consistence ; but opposite the joints it consists of a thin membrane with scat- tered and oblique fibres. If the sheath be opened it will be seen to be lined by a synovial membrane, which forms long and slender vascular folds (vin- cula vasculosa) between the tendons and the bones. Dissection. The palmar fascia, and the thinner parts of the digital sheaths opposite the joints of Extensor Tendon of the fingers, may be taken away. On the removal the finger with its ac- of the fascia the palmar arch of the ulnar artery, sheath op the and the median and ulnar nerves, become ap- Flexor tendons. parent. Extensor tendon, with b, Palmar Part of the Ulnar Artery (fig. interosseous, and c,iu:n- 83). In the palm of the hand the ulnar artery is bricaies muscles joining directed towards the muscles of the thumb, where it communicates with two offsets of the radial ^thj^ker^^^mHs ^oT^Us trunk, viz., the superficial volar branch (c), and sheath, the branch to the radial side of the forefinger (f). The curved part of the artery, which lies across the hand, is named the superficial palmar arch {d). Its convexity is turned towards the fingers, and its position in the paint would be nearly marked by a line across the hand from the cleft of the thumb. The arch is comparatively superficial ; it is covered in greater part hy 274 DISSECTION OF THE HAND. the integuments a.nd the palmar fascia, but at the inner border of the hand the palmaris brevis muscle (h) lies over it. Beneath it are the flexor tendons and the branches of the ulnar and median nerves. Venae comites lie on its sides. Branches. From the convexity of the arch proceed the digital arteries, and from the concavity some small offsets to the palm of the hand. A small branch (profunda) arises as soon as the artery enters the hand. a. The profunda or communicating branch (fig. 84, 5), passes down- wards with a branch of the ulnar nerve between the abductor and short flexor muscles of the little finger, to inosculate with the deep palmar arch of the radial artery. b. The digital branches {g) are four in number, and supply both sides of the three inner fingers and one side of the index finger. The branch to the inner side of the hand and little finger is undivided ; but the others, corresponding with the three inner interosseous spaces, bifurcate anteriorly to supply the contiguous sides of the above said digits. In the hand these branches are accompanied by the digital nerves, which they sometimes pierce. Near the root of the fingers they receive communicating branches from offsets of the deep arch ; but the digital artery of the inner side of the little finger has its communicating branch about the middle of the hand. From the point of bifurcation the branches extend along the sides ot the fingers ; and over the last phalanx the vessels of opposite sides unite in an arch, from whose convexity offsets proceed to supply the ball of the finger. Collateral offsets are furnished to the finger and the sheath of the tendons ; and small twigs are supplied to the phalangeal articulations from small arterial arches on the bones — an arch being close behind each joint. On the dorsum of the last phalanx is another arch near the nail, from which the nail-pulp is supplied. Palmar Part of the Ulnar Nerve (fig. 83, ^). The ulnar nerve divides on or near the annular ligament, into a superficial and a deep branch. The deep branch accompanies the profunda artery to the muscles, and will be subsequently dissected with that vessel (fig. 84). The superficial branch furnishes an offset to the palmaris brevis muscle, and some filaments to the integument of the inner part of the hand, and ends in two digital nerves, for the supply of both sides of the little finger and half the next. Digital nerves (^). The more internal nerve is undivided, like the cor- responding artery. The other is directed to the cleft between the ring and little fingers, and bifurcates for the supply of their opposed sides : in the palm of the hand this last branch is connected with an offset (^) of the median nerve. Along the sides of the fingers the digital branches have the same- arrangement as those of the median nerve. Palmar Part of the Median Nerve (fig. 83,^). As soon as the median nerve issues from beneath the annular ligament it becomes enlarged and somewhat flattened, and divides into two nearly equal parts for the supply of digital nerves to the thumb and the remaining two fingers and a half: the more external of the two portions furnishes a small muscular branch to the ball of the thumb. Tlie trunk of the nerve and its branches are covered by the palmar fascia ; and beneath them are the tendons of the flexor muscles. MEDIAN NERVE AND BRANCHES. 275 a. The branch to muscles of the thumb (*) supplies the outer half of the short flexor, and ends in the abductor, and opponens pollicis muscles. b. The digital nerves (®) are five in number. Three of them, which are distributed to the sides of the thumb and the radial side of the fore finger, are undivided, and come from the external of the two pieces into Fig. 83. Dissection of the Superficial Vessels and Nerves of the Palm of the Hand with some OF THE Superficial Muscles, (Illustratious of Dissections.) Muscles : A. Abductor policis. c. Flexor brevis. D. Adductor policis. H. Palmaris brevis. Arteries: a. Trunk of ulnar, and &, of radial. c. Superficial volar branch, d. Superficial palmar arch. e. Branch uniting the arch with / the radial digital branch of the forefinger. g. Four digital branches of the superficial arch. Nerves : 1. Ulnar, and 2, its two digital branches. 3. Median, and 5, its digital branches to three fingers and a half. 4. Branch of the median to some muscles of the thumb 5. Communicating branch from the median to the ulnar. which the trunk of the median splits. The other two spring from the in- ner piece of the nerve, and are bifurcated to supply the opposed sides of the middle and fore, and the middle and ring fingers. The first two nerves belong to the tliumb, one being on each side, and the most external is said to communicate with branches of the radial nerve. 276 DISSECTION OF THE HAND. The third is directed to the radial side of the index finger, and gives a branch to the most external h mbrical muscle. The fourth furnishes a nerve to the second lumbrical muscle, and di- vides to supply the contiguous sides of the fore and middle fingers. The Jifth^ like the fourth, is distributed by two branches to the opposed sides of the middle and ring fingers : it communicates with a branch of the ulnar nerve. On the fingers. On the sides of the fingers the nerves are superficial to the arteries, and reach to the last phalanx, where they end in filaments for the ball and the pulp beneath the nail. In their course forwards the nerves supply chiefly tegumentary branches : one of these is directed backwards by the side of the metacarpal phalanx, and after uniting with the digital nerve on the back of the finger (p. 2G2), is continued to the dorsum of the last phalanx. Dissection. The tendons of the flexor muscles may be followed next to their termination. To expose them the ulnar artery should be cut through below the origin of the profunda branch ; and the small superficial volar branch (of the radial) having been divided, the palmar arch is to be thrown towards the fingers. The ulnar and median nerves are also to be cut be- low the annular ligament, and turned forwards. A longitudinal incision is to be made through tlie centre of the annular ligament, without injuring the small muscles that arise from it, and the pieces of the ligament are to be thrown to the sides. Finally the sheaths of the fingers may be opened for the purpose of ob- serving the insertion of the tendons. Flexor tendons. Beneath the annular ligament the tendons of the deep and superficial flexors are surrounded by a large and loose synovial membrane, which projects upwards into the forearm and downwards into the hand, and sends an offset into the digital sheath of the thumb and that of the little finger.^ Flexor suhlimis. The tendons of the flexor sublimis are superficial to those of the deep flexor beneath the ligament ; and all four are nearly on the same level, instead of being arranged in pairs, as in the forearm. After crossing the [)alm of the hand they enter the sheath of the fingers (fig. 82, e), and are inserted each by two processes into the margins of the middle phalanx, about the centre. When first entering the digital sheath, the tendon of the flexor sublimis* conceals that of the flexor profundus ; but near the front of the first phalanx it is split for the passage of the tendon of the latter muscle. Dissection. To see the tendons of the deep flexor and the lumbrical mus- cles, the flexor sublimis must be cut through above the wrist, and thrown towards the fingers. Afterwards the areolar tissue should be taken away. Flexor profundus. At the lower border of the annular ligament the ten- dinous mass of the flexor profundus is divided into four pieces, though in the forearm only the tendon of the forefinger is distinct from the rest. From the ligament the four tendons are directed through the hand to the fingers, and give origin to the small lumbricales muscles. At the root of the fingers each enters the digital sheath with a tendon of the flexor sub- limis, and having passed through that tendon, is inserted into the base of the last phalanx. • Theile refers the notice of this fact to M. Maslieurat-Lag^rnard, in No. 18 of the “Gazette MMicale,” for 1839. MUSCLES OF THUMB. 277 Between both flexor tendons and the bones are thin membranes, one for each. By means of this each tendon is connected with the capsule of the joint, and the fore part of the phalanx immediately behind the bone into which it is inserted. The lumhricales muscles (fig. 84, i) are four small fleshy slips, which arise from the tendons of the deep flexor near the annular ligament ; and are directed to the radial side of each finger, to be inserted into an aponeurotic expansion on the dorsal aspect of the metacarpal phalanx (fig. 82, c). These muscles are concealed for the most part by the tendons and ves- sels that have been removed; but they are subcutaneous for a short distance between the processes of the palmar fascia. The outer two arise from single tendons, but each of the others is connected with two tendons. Action. By their insertion into the long extensor tendon they will aid it in straightening the two last phalangeal joints ; and when the metacarpo- phalangeal joints are much bent they may assist in maintaining the flexion of these articulations. Tendon of the flexor poUicis longus. Beneath the annular ligament this tendon is external to the flexor profundus, and turns outwards between the heads of the flexor brevis pollicis (fig. 84), to be inserted into the last phalanx of tlie thumb. Tlie common synovial membrane surrounds it be- neath the annular ligament, and sends a prolongation, as before said, into its digital sheath. Dissection (fig. 84). The deep palmar arch of the radial artery, with the deep branch of the ulnar nerve, and the interossei muscles, will come into view if the flexor profundus is cut above tlie wrist, and thrown with the lumhricales muscles towards the fingers ; but in raising the tendons the student should preserve two fine nerves and vessels entering the two inner lumbrical muscles. The dissection of the muscles of the ball of the thumb and the little finger is next to be prepared. Some care is necessary in making a satis- factory separation of the ditferent small thumb muscles ; but those of the little finger are more easily defined. Short Muscles of the Thumb (fig. 84). These are four in number, and are named from their action on the thumb. The most superficial is the abductor pollicis ; beneath it is the opponens pollicis, which will be recognized by its attachment to the whole length of the metacarpal bone. To the inner side of the last is the short flexor. And the wide muscle coming from the third metacarpal bone is the adductor of the thumb. The ABDUCTOR POLLICIS, A, is about an inch wide, and is thin, and superficial to the rest. It arises from the upper part of the annular liga- ment at the radial side, and from the ridge of the os trapezium ; and is inserted into the base of the first phalanx of the thumb. The muscle is subcutaneous, and rests on the opponens pollicis : it is connected oftentimes at its origin with a slip from the tendon of the ex- tensor ossis metacarpi pollicis. Action. It removes the metacarpal bone of the thumb from the other digits ; and when it has so acted it may assist slightly the short flexor in bending the metacarpo-phalangeal joint. Dissection. The opponens pollicis will be seen on cutting through the abductor. To separate the muscle from the short flexor on the inner side, the student should begin near the fore part of the metacarpal bone, where there is usually a slight interval. 278 DISSECTION OF THE HAND. The OPPONENS POLLicis, B, arises from the annular ligament beneath the preceding, and from the os trapezium and its ridge ; it is inserted into the front and outer border of the metacarpal bone for the whole length. This muscle is partly concealed by the preceding, though it projects on the outer side. Along its inner border is the flexor brevis pollicis. An insertion into the external sesamoid bone is described by Theile. Action. From its attachment to the metacarpal bone it is able to draw that bone inwards over the palm of the hand, turning it at the same time, so as to allow the ball of the thumb to be applied to the ball of each of the fingers, as in picking up a pin. The FLEXOR BREVIS POLLICIS, c, is the largest of the short muscles of the thumb : it consists of two pieces (inner and outer) at the insertion, but these are united at the origin. Posteriorly it arises from the os trapezoides and os magnum ; from the bases of the second and third metacarpal bones ; and from the annular ligament, at the lower part. In front it is inserted by two heads into the sides of the base of the first phalanx of the thumb, — the inner piece being united with the adductor, and the outer with the abductor pollicis. A sesamoid bone is connected with each head at its insertion. The tendon of the long flexor lies on this muscle, occupying the interval between the processes of insertion ; and the deep palmar arch of the radial artery issues from beneath the inner head. Action. The muscle bends the metacarpo-phalangeal joint, and assists the opponens in drawing the thumb forwards and inwards over the palm. The ADDUCTOR POLLICIS, D, is pointed at the thumb, and wide at the opposite end. Its origin is fixed to the anterior or lower two-thirds of the metacarpal bone of the middle digit, on the palmar aspect ; and its inser- tion is attached, with that of the short flexor, to the inner side of the first phalanx of the thumb. The cutaneous surface is in contact with the tendons of the flexor pro- fundus and the lumbrical muscles ; and the deep surface lies over (in this position) the first dorsal interosseous muscle, J, and the second and third metacarpal bones with the intervening muscle. Actions. By its contraction the thumb is applied to the radial border of the hand, and approximated to the fingers. Short Muscles of the Little Finger (fig. 84). There are com- monly two muscles in the ball of the little finger, — an abductor and an adductor. Sometimes there is a short flexor between the other two. The ABDUCTOR MINIMI DIGIT!, E, is the most internal of the short muscles. It arises from the pisiform bone and the tendon of the flexor carpi ulnaris, and is inserted into the ulnar side of the base of the first j)halanx of the little finger; an offset from it reaches the extensor tendon on the back of the phalanx. The palmaris brevis partly conceals the muscle. Action. First it draws the little finger away from the others; but con- tinuing to act it bends the metacarpo-phalangeal joint. The FLEXOR BREVIS MINIMI DiGiTi, F, appears often to be a part of the abductor. Placed at the radial border of the preceding muscle, it takes origin from the tip of the process of tlie unciform bone, and slightly from the annular ligament ; it is inserted with the abductor into the first phalanx. It lies on the adductor ; and near its origin it is separated from the abductor muscle by the deep branches of the ulnar artery and nerve. MUSCLES OF LITTLE FINGER. 279 Action. The first phalanx is moved towards the palm by this muscle, and the metacarpo-phalangeal joint is bent. The ADDUCTOR vel OPPONENS MINIMI DiGiTi, G, resembles the opponens pollicis in being attached to the metacarpal bone. Its origin is from the process of the unciform bone, and the lower part of the annular ligament ; its insertion is fixed into the ulnar side of the metacarpal bone of the little finger. Fig. 84. Deep Dissection of the Palm of Muscles : A. Abductor pollicis. B. Opponens pollicis. c. Flexor brevis pollicis. D. Adductor pollicis. E. Abductor minimi digiti. F. Flexor brevis minimi digiti. G. Opponens minimi digiti. I. Lumbricales. J. First dorsal interosseous. HE Hand. (Illustrations of Dissections.) Vessels : «. Ulnar artery, cut. h. Profunda branch. c. Deep palmar arch. d. Radial digital artery of the index finger. e. Arteria magna pollicis. /. Interosseous arteries. Nerves : 1. Ulnar nerve, cut. 2. Deep branch of the palm of the hand, and 4, its continuation to end in some of the thumb muscles. 3. Offsets to the inner two lumbricales. The adductor is partly overlaid by the preceding muscles ; and beneath it the deep branches of the ulnar artery and nerve pass. Action. It raises the inner metacarpal bone, and moves it towards the others, so as to deepen the palm of the hand. Dissection. The radial artery comes into the hand between the first 280 DISSECTION OF THE HAND. two metacarpal bones ; and to lay bare the vessel, it will be requisite to detach the origin of the flexor brevis pollicis. The deep palmar arch, and the branch of the ulnar nerve accompanying it, together with their offsets, are to be dissected out. A fascia, which covers the interossei muscles, is to be removed, when the dissector has observed its connection with the transverse ligament uniting the heads of the metacarpal bones. Radial Artery in the Hand (tig. 84). The radial artery enters the palm at the first interosseous space, between the heads of the first dorsal interosseous muscle : and after furnishing one branch to the thumb, and another to the index finger, turns across the hand towards the ulnar side, with its veme comites, forming the deep arch. The deep palmar arch (c) extends from the interosseous space to the base of the metacarpal bone of the little finger, where it joins the profunda communicating branch (h). Its convexity, which is but slight, is directed forwards ; and its ])Osition is nearer the carpal bones than that of the superficial arch. The arch has a deep position in the hand, and lies on the metacarpal bones and the interossei muscles. It is covered by the long flexor tendons, and in part by the flexor brevis pollicis. The branches of the arch are the following : — a. Recurrent branches pass from the concavity of the arch to the front of the carpus ; these supply the bones, and anastomose with the other carpal arteries. b. Three perforating arteries pierce the three inner dorsal interossei muscles, and communicate with the interosseous arteries on the back of the hand. c. Usually there are three palmar interosseous arteries (/), which occupy the three inner metacarpal spaces, and terminate by joining the digital branches of the superficial })almar arch at the cleft of the fingers. These branches supjdy the interosseous muscles, and the two or three inner lumbricales ; they vary much in their size and distribution. d. Digital branches of the radial. The large artery of the thumb {c) (art. princeps pollicis) runs between the first metacarpal bone and the flexor brevis pollicis, to the interval between the heads of the muscle, where it divides into the two collateral branches of the thumb : these are distributed like the arteries of the superficial fu'ch. e. The digited branch of the index finger (art. radialis indicis) is directed over the first dorsal interosseous muscle, .i, and beneath the short flexor and the adductor pollicis, to the radial side of the forefinger. At the free or anterior border of the adductor {',ollicis, d, this branch is usually connected by an offset with the superficial palmar arch ; and at the end of the digit it unites with the branch furnished to the opposite side by the ulnar artery. The deep branch of the ulnar nerve ('^) accompanies the arch of the radial artery as far as the muscles of the tliiimb, and terminates in offsets to the adductor pollicis and the inner head of the short flexor. Branches. Near its origin the nerve furnishes branches to the muscles of the little finger. In the palm it gives offsets to all the palmar and dorsal interosseous muscles, and to the inner two lumbrical muscles (^), besides the terminal branches before mentioned. The transverse metacarpal ligament connects together the heads of the four inner metacarpal bones. Its cutaneous surface is hollowed where the flexor tendons cross it ; and beneath the interossei muscles pass to their RADIAL ARTERY AND OFFSETS. 281 insertion. To the posterior border the fascia covering the interossei muscles is united. The ligament should now be taken away to see the interossei muscles. The INTEROSSEI MUSCLES, SO named from their position between the metacarpal bones, are seven in number. Two muscles occupy each space, except in the first where there is only one ; they arise from the meta- carpal bones, and are inserted into the first phalanx of the fingers. They are divided into palmar and dorsal interossei ; but all the small muscles are evident in the palm of the hand, though some project more than the others. The 'palmar muscles (fig. 85), three in number, are smaller than the dorsal set, and are most prominent in the palm of the hand. They arise from the palmar surface of the metacarpal bones of the fingers on which they act, viz., those of the fore, ring, and little fingers ; and they are in- serted into the ulnar side of the fore, and the radial side of the other two digits. Fig. 85. Fig. 80. Three Palmar Interosseoc.s Muscles. Four Dorsal Interosseous Muscles. a. Muscle of the little finger; h, of the ring d. Muscle of the forefinger, called sometimes finger ; and c, of the forefinger. abductor indicis. c and/. Muscles of the middle finger. g. Muscle of the ring finger. Both sets of muscles have a similar termination (fig. 82, 5) : — the fibres end in a tendon, which is inserted into the side of the first or metacarpal phalanx, and sends an expansion to join the extensor tendon on the dor- sum of the bone. The dorsal interossei (fig. 8G) extend farther back than the palmar setj and arise by two heads from the lateral surfaces of the metacarpal bones between which they lie. The dorsal muscles are thus allotted to the digits : — two belong to the second finger, a third is connected with the radial side of the fore, and the fourth with the ulnar side of the ring finger. Action. They help to bend the m'etacarpo-phalangeal joints by their 282 DISSECTION OF THE FOREARM. attachment to the first phalanx ; and assist in the extension of the two last phalangeal joints through their union with the extensor tendon. Further they can separate and approximate the fingers : thus the palmar set adduct to tlie second finger ; and the dorsal abduct from the middle line of the second finger — the two attached to this digit moving it to the right and left of that line. Dissection. The attachments of the annular ligament to the carpal bones on each side are to be next dissected out by taking away the small muscles of the thumb and little finger. Before reading its description, the ends of the cut ligament iiray be placed in apposition. The anterior annular ligament is a firm ligamentous band, which arches over and binds down the flexor tendons of the fingers. It is attached ex- ternally to the front of the os scaphoides, and to the fore and inner parts, and ridge of the os trapezium ; and internally to the unciform and pisiform bones. By its upper border it is connected with the aponeurosis of the forearm ; and by its anterior surface it joins the palmar fascia. On it lie the palmaris longus and the ulnar artery and nerve. Dissection. Next follow the tendon of the flexor carpi radialis through the os trapezium to its insertion into the metacarpal bones. The tendon of the flexor carpi radialis, in passing from the forearm to the hand, lies in the groove in the os trapezium between the attachments of the annular ligament to the bone, but outside the arch of that ligament ; here it is bound down by a fibrous sheath lined by a synovial membrane. The tendon is inserted into the base of the metacarpal bone of the index finger, and sends a slip to that of the middle digit. Section VI. THE BACK OF THE FOREARM. Position. During the dissection of the back of the forearm the limb lies with the forepart undermost, and a small block is to be placed beneath the wrist for the purpose of stretching the tendons. Dissection (fig. 87). The fascia and the cutaneous nerves and vessels are to be reflected from the muscles of the forearm, and from the tendons on the back of the hand ; but in removing the fascia in the forearm, the student must be careful not to cut away the posterior interosseous vessels, which are in contact vvith it on the inner side in the lower third. A thick- ened band of the fascia opposite the carpus (the posterior annular ligament) is to be left. Let the integument be removed from the fingers, in order that the ten- dons may be traced to the end of the digits. The several muscles should be separated from one another up to their origin, especially the two radial extensors of the wrist. The posterior annular ligament, k, consists of the special aponeurosis of the limb, thickened by the addition of some transverse fibres, and is situate op{)osite the lower end of the bones of the forearm. This band is connected at the outer part to the radius, and at the inner to the cuneiform and pisiform bones. Processes from it are fixed to the bones beneath, and SUPERFICIAL LAYER OF MUSCLES 283 confine the extensor tendons. The ligament will be subsequently examined more in detail. Superficial layer of muscles (fig. 87). The muscles are arranged in a superficial and a deep layer, as on tlie anterior part of the forearm. Fig. 87. Mnscles : A. Supinator longus. B, Extensor carpi radialis longns. 0 . Extensor carpi radialis brevis. ». Extensor communis digitorum. E. Extensor minimi digiti. F. Extensor carpi ulnaris. G. Anconeus. H. Extensor ossis metacarpi pollicis. 1. Extensor prirai iuternodii. J. Extensor secuudi interiiodii pollicis. K. Posterior annular ligament. li. Bands uniting the tendons of the common ex- tensor on the back of the hand. N. Insertion of the common extensor into the last two phalanges. Arteries : a. Posterior interosseous. I. Radial. 2. Posterior carpal arch. d. Metacarpal branch. 4. Dorsal branches of thumb and forefinger. Superficial Layer of Muscles on the Back of the Forearm, with some Vessels. (Illustrations of Dissections.) The superficial layer contains seven muscles, which arise mostly by a com- mon tendon from the outer condyle of the humerus, and have the under- mentioned position one to another from without inwards ; — tlie long supi- 284 DISSECTION OF THE FOREARM. nator, A, tlie two radial extensors of the wrist, b and c (long and short), the common extensor of the fingers, d, the extensor of the little finger, e, and the ulnar extensor of the wrist, f. There is one other small muscle near the elbow, the anconeus, G. The SUPINATOR RADII LONG US, A, reaches upwards into the arm, and limits on the outer side the hollow in front of the elbow. The muscle arises from the upper two-thirds of the outer condyloid ridge of the hu- merus, and the front of the external intermuscular septum. The fleshy fibres end about the middle of the forearm in a tendon, which is inserted into the lower end of the radius, close above the styloid process. In the arm the margins of the supinator are directed towards the sur- face and the bone, but in the forearm and muscle is flattened oyer the others, with its edges forwards and backwards. Its anterior border touches tlie biceps and the pronator teres ; and the posterior is in contact with both radial extensors of the wrist. Near its insertion the supinator is covered by two extensors of the thumb. Beneath the muscle are the brachialis anticus and musculo-spiral nerve, the extensors of the wrist, the radial vessels and nerve, and the radius. Action. The chief use of this supinator is to bend the elbow-joint. But if the radius is either forcibly proiiated or supinated the muscle can put the hand into a state intermediate between pronation and supination, — the thumb beiim brought above the forefin«;er. o o o If the radius is fixed as in climbing, the muscle will bring up the hu- merus, bending the elbow. The EXTENSOR CARPI RADiALis LONGiOR, B, arises from the lower third of the outer condyloid ridge of the humerus, and the front of the contigu- ous intermuscular septum ; and from the septum between it and the next muscle. The muscle lies on the short radial extensor, being partly cov- ered by the supinator longus ; and its tendon passes beneath the extensors of the thumb, and the annular ligament, to be inserted into the base of the metacarpal bone of the index finger. Along its outer border lies the radial nerve. Action. The long extensor straightens first the wrist, and bends next the elbow joint. If the hand is fixed in climbing, it will act on the humerus like the long supinator. The EXTENSOR CARPI RADIALIS BREViOR, c, is attached to the outer condyle of the humerus by a tendon common to it and the three following muscles, viz., common extensor of the fingers, extensor of the little finger and ulnar extensor of the wrist : it takes origin also from the capsular ligament of the elbow joint. The tendon of the muscle is closely con- nected with the preceding, and after passing with it through the same com- })artment of the annular ligament, is inserted into the base of the meta- carpal bone of the middle finger. Concealed on the outer side by the two preceding muscles this extensor rests on the radius and some of the muscles attached to it, that is to say, on the supinator brevis, and the pronator teres. Along the ulnar side is the common extensor of the fingers; and the extensors of the thumb come between it and the digital ex<^ensor. Both radial extensors of the carpus have usually a bursa at the insertion. Action. Tliis muscle resembles its fellow in extending the wrist, but differs fi-om it in extending the elbow. EXTENSORS OF DIGITS. 285 Acting with the long extensor of the wrist it will move the lower end of the radius in supination. The EXTENSOR COMMUNIS DiGiTORUM, D, is single at its origin, but is divided inferiorly into four tendons. It arises from the common tendon, from aponeurotic se{)ta between it and the muscles around, and from the aponeurosis of the Ifmb. Near the lower part of the forearm the muscle ends in three tendons, which pass through a compartment of the annular ligament with the indicator muscle; beloiv the ligament, the most internal tendon divides into two, and all four are directed along the back of the hand to their insertion into the two last phalanges of the fingers. On the back of the fingers the tendons have the following arrangement. On the dorsum of tlie first phalanx each forms an expansion with the ten- dons of the lurnbricales and interossei muscles (fig. 82). At the front of that phalanx it divides into three parts (fig. 87, : — the central one is fixed into the base of the second phalanx, whilst the lateral pieces unite, and are inserted into the base of the last phalanx. On the fore and little fingers the expansion is joined by the special tendons of those digits ; and oppo- site the first two articulations of each finger the tendon sends down lateral bands to join the capsule of the joint. This muscle is placed between the extensors of the wrist and little finger, and conceals the deep layer. On the back of the hand the tendons are joined by cross pieces, l, wliich are strongest between the ring finger ten- don and its collateral tendons ; they prevent the ring finger being raised if the others are closed. Action. Tlie muscle straightens the three phalanges of the fingers from root to tip, and separates the four digits from each other. It can extend the nearest joint of each finger w'hilst the tw o farthest are kept bent by the flexors ; and it can straighten the last two articulations wlien tlie nearest is bent. The digits being straightened, it will assist the other muscles in extend- ing the wrist and the elbow'. The EXTENSOR MINIMI DiGiTi, E, is the most slender muscle on the hack of tlie forearm, and appears to be but a part of the common extensor. Its origin is in common with that of the extensor communis, but it passes through a distinct sheath of the annular ligament. Beyond the ligament the tendon splits into tw'o, and only one unites by a cross piece with the tendon of the common extensor : both finally join the common expansion on the first phalanx of the little finger. Action. It extends the little finger and moves back the wrist and elbow. As the inner piece of the split tendon is not united with the common ex- tensor it can straighten the digit during flexion of the other fingors. The EXTENSOR CARPI ULNARis MUSCLE, F, arises from the common tendon, and the aponeurosis of the forearm ; it is also fixed by fascia to the posterior border of the ulna below the anconeus muscle (about the middle third). Its tendon becomes free from fleshy fibres near the annu- lar ligament, and passes through a sejiarate sheath in that structure to be inserted into the base of the metacarpal bone of the little finger. Beneath this extensor are some of the muscles of the deep layer, wdth part of the ulna. On the outer side is the extensor of the little finger, M'ith the posterior interosseous vessels. Action. As the name expresses, the muscle puts back the Mu-ist and in- clines the hand tow’ards the ulnar side : it can tlien extend the elbow' joint. The ANCONEUS, G, is a small triangular muscle near the elbow. It arises 286 DISSECTION OF THE FOREARM. from the outer condyle of the humerus by a tendon distinct from, and on the ulnar side of the common tendon of origin of tlic other muscles. From this origin the fibres diverge to their insertion into the outer side of the olecranon, and into the impression on the upper third of the posterior sur- face of the ulna. Fig. 88. Muscles : A. Supinator longus. B. and c. Radial extensors of the carpus, cut. D. Supinator brevis. E. Extensor ossis inetacarpi pollicis. F. Extensor primi internodii. G. Extensor secundi internodii. H. Extensor indicis. I. Posterior annular ligament. Arteries : а. Posterior interosseous. б. Recurrent interosseous. c. Dorsal part of the anterior interosseous. d. Dorsal part of the radial. e. Dorsal branches to the thumb and forefinger. /. Dorsal carpal arch. g. Two posterior interosseous (ulnar) of the hand. Nerves : 2. Radial. 3. Posterior interosseous at its origin, and 4, near its ending in a swelling on the back of the carpus. Dissection of the Deep Later of Mcscles, and the Vessels and Nerve on the Back op THE Forearm. (Illustrations of Dissections.) The upper fibres are nearly transverse, and are contiguous to the lowest of the triceps muscle. Beneath the anconeous lie the supinator bre\is muscle, and the recurrent interosseous vessels. Action. Commonly it acts on tlie ulna, and assists the triceps in ex- tending the elbow. DEEP EXTENSOR MUSCLES. 287 Dissection (fig. 88). For the display of the deep muscles at the back of the forearm, and the posterior interosseous artery and nerve, three of the superficial muscles, viz., extensor communis, extensor minimi digiti, and extensor carpi ulnaris, are to be detached from their origin and turned aside : in this proceeding the small branches of the nerve and artery enter- ing the muscles may be divided. Tlie loose tissue and fat are then to be removed from the muscles, and the ramifications of the artery and nerve ; and a slender part of the nerve, which sinks beneath the extensor of the second phalanx of the thumb about the middle of the forearm, sliould be traced beyond the wrist. The separation of the muscles should be made carefully, because the highest two of the thumb are not always very distinct from each other. Deep layer of muscles (fig. 88). In this layer there are five small muscles, viz., one supinator of the forearm, and four special extensor mus- cles of the thumb and forefinger. The highest muscle, surrounding partly the upper end of the radius, is the supinator brevis, d. Below this are the three muscles of the thumb in the following order: — the extensor of the metacarpal bone, e, the extensor of the first, f, and that of the second phalanx, G. On the ulna the indicator muscle, h, is placed. The EXTENSOR ossis METACARPI POLLicis, E, is the largest and highest of the extensor muscles of the thumb, and is sometimes united with the supinator brevis. It arises from the posterior surface of the radius for three inches below the supinator brevis ; from the ulna for the same dis- tance by a narrow special impression on the upper and outer part of the posterior surface ; and from the intervening interosseous membrane. The tendon is directed outwards over the radial extensors of the wrist, and through the annular ligament, to be inserted into the base of the metacarpal bone of the thumb, and by a slip into the os trapezium. The muscle is concealed at first by the common extensor of the fingers ; but it becomes cutaneous between the last muscle and the extensors of the wrist, about two inches above the end of tlie radius (fig. 87). Opposite the carpus the radial artery winds backwards beneath its tendon. Between the contiguous borders of this muscle and the supinator brevis the posterior interosseous artery {a) appears. Action. By this muscle the thumb is moved backwards from the palm of the hand, and the wrist is extended on the radial side. The EXTENSOR PRiMi iNTERNODii POLLICIS, F, is the Smallest muscle of the deep layer, and its tendon accompanies that of the preceding ex- tensor. Its origin., about one inch in width, is from the radius and the interosseous membrane, close below the attachment of the preceding muscle. The tendon passes through the same space in the annular ligament as the extensor of the metacarpal bone, and is inserted into the metacarpal end of the first phalanx of the thumb. With respect to surrounding parts this muvscle has the same connections as the preceding. Action. It extends first tlie nearest phalanx, and then the wrist, like its companion. The EXTENSOR SECUNDi INTERNODII POLLICIS, G, ai’ises from the ulna for four inches below the anconeus, along the ulnar side of the extensor of the metacarpal bone ; and from the interosseous membrane, below, for one inch. Its tendon passing through a sheath in the annular ligament, dis- tinct from that of the other two extensor muscles, is directed along the dorsum of the thumb to be fixed to the base of the last phalanx. It is covered by the same muscles as the other extensors of the thumb. 288 DISSECTION OF THE FOREARM. blit it becomes superficial nearer the lower end of the radius. Below the annular ligament its tendon crosses the radial artery, and the extensors of the wrist. Action. Its use is similar to that of the extensor of the first phalanx. When the phalanges are straight, the two extensors will assist in carrying back the metacarpal bone. The EXTENSOR iNDicis, H (indicator), arises from the ulna for three or four inches, usually beyond the middle, and internal to the preceding mus- cles ; and from the interosseous ligament below. Near the annular liga- ment the tendon becomes free from muscular fibres, and passing through that band with the common extensor of the fingers, is applied to, and blends with, the external tendon of that muscle in the expansion on the phalanx of the forefinger. Until this muscle has passed the ligament it is covered by the superfi- cial layer, but it is afterwards subaponeurotic. Action. The muscle can point the fore finger even when the three inner fingers are bent, inclining it towards the others at the same time. And it will help the common extensor of the digits in pulling back the hand. Dissection. To lay bare the supinator brevis, it will be necessary to detach the anconeus from the external condyle ot the humerus, and to cut through the supinator longus and the radial extensors of the wrist. After those muscles have, been divided, the fleshy fibres of the supinator are to be followed forwards to their insertion into the radius ; and that j)art of the origin of the flexor profundus digitorurn, which lies on the outer side of the insertion of the bracliialis anticus, is to be removed. The SUPINATOR BREVIS, D, suiTounds the upper part of the radius, except at the tubercle and along a slip of bone below it. It arises from a depression below the small sigmoid cavity of the ulna, from the external margin of the bone for two inches below that pit, and from the orbicular ligament of the radius and the external lateral ligament of the elbow joint. The fibres i)ass outwards, and are inserted into the upper third or more of the radius, except at the inner part, reaching downwards to the insertion of the pronator teres, and forwards to the hollowed anterior surface. The supinator is concealed altogether at the posterior and external aspects of the limb by the muscles of the superficial layer; and anteriorly tlie radial vessels and nerve lie over it. The lower border is contiguous to the extensor ossis metacarpi pollicis, only the posterior interosseous artery (a) intervening. Through the substance of the muscle the posterior interosseous nerve (^) winds to the back of the limb. Action. When the radius has been moved over the ulna as in prona- tion, the short supinator comes into play to bring that bone again to the outer side of the ulna. lihe, posterior interosseons artery (fig. 88, a) is an offset from the com- mon interosseous trunk (p. 269), and reaches the back of the forearm above the ligament between the bones. Aj)pearing between the contiguous borders of the supinator brevis and extensor ossis metacarpi, the artery descends at first between the superficial and deep layers of muscles ; and afterwards, with a superficial position in the lower third of the forearm, along the tendon of the extensor carpi ulnaris as far as the wrist, where it ends by anastomosing with the carpal and anterior interosseous arteries. It furnishes muscular offsets to the contiguous muscles, except the two or three outer ; and the following recurrent branch: — The recurrent branch (6) springs from the artery near the commence- RADIAL ARTERY. 289 ment, and ascends on or through the fibres of the supinator, but beneath the anconeus, to supply both those muscles and the elbow joint, and to anastomose with the superior profunda artery in the last-named muscle, as well as witJi the recurrent radial. The posterior interosseous nerve (^) takes origin from the musculo-spiral trunk (p. 259), and winds backwards through the fibres of the supinator brevis. Escaped from the supinator, the nerve is placed between the superficial and deep layers of muscles as far as the middle of the forearm. Much reduced in size at that spot, it sinks beneath the extensor of the second phalanx of the thumb, and runs on the interosseous membrane to the back of the carpus. Finally the nerve enlarges beneath the tendons of the extensor communis digitorum, and terminates in filaments to the ligaments and the articulations of the carpus. Branches. It furnishes offsets to all the muscles of the deep layer ; and to those of the suj)erficial layer with the exception of the three follow- ing, viz., anconeus, supinator longus, and extensor carpi radialis longior. Radial Arti:ry at the Wrist (fig. 88). The radial artery (c?), with its veme comites, winds below the radius to the back of the carpus, and enters the palm of the hand at the first interosseous space, between the heads of the first dorsal interosseous muscle. At first the vessel lies deeply on the external lateral ligament of the wrist joint, and beneath the tendons of the extensors of the metacarpal bone, e, and first phalanx of the thumb, f ; but afterwards it is more superficial, and is crossed by the tendon of the extensor of the second phalanx of the thumb, G. Offsets of the external cutaneous nerve entwine around the artery, and the radial nerve is superficial to it. Its branches are numerous but incon- siderable in size: — a. The dorsal carpal branch (f) passes transversely beneath the ex- tensor tendons, and forms an arch with a corresponding offset of the ulnar artery ; with this arch the posterior interosseous artery joins. From the carpal arch branches (g) descend to the third and fourth interosseous spaces, and constitute two of the three dorsal interosseous arteries: at the cleft of the fingers each divides into two, which are con- tinued along the dorsum of the digits. In front they communicate with the digital arteries ; and behind they are joined by the perforating branches of the palmar arch. b. The metacarpal or first dorsal interosseous branch (fig. 87, 5), reaches the space between the second and third metacarpal bones, and anastomoses, like the corresponding arteries of the other spaces, with a perforating branch of tlie deep palmar arch. Finally it is continued to the cleft of the fingers, where it joins the digital artery of the superficial palmar arch, and gives small dorsal branches to the index and second fingers. 6*. Two small dorsal arteries of the thumb (c) arise opposite the meta- carpal bone, along which they extend, one on each border, to be distributed on its posterior aspect. d. The dorsal branch of the index finger is distributed on the radial edge of that digit. The different compartments of the annular ligament may be seen more completely by dividing the sheaths of the ligament over the several ten- dons passing beneath. There are six different spaces, and each is luliri- cated by a synovial membrane. The most external one lodges tlie first two extensors of the thumb. The next is a large hollow for the two radial 19 290 DISSECTION OF THE UPPER LIMB. extensors of the wrist ; and a very small space for the extensor of the second phalanx of the thumb follows on the ulnar side. Farther to the inner side is the common sheath for the extensor of the fingers, and that of the fore finger ; and then comes a separate compartment for the exten- sor of the little finger. Internal to all is the space for the extensor carpi ulnaris. The last muscle grooves the ulna ; but the others lie in hollows in the radius in the order mentioned above, with the exception of the ex- tensor minimi digiti, which is situate between the bones. Dissection. If the supinator brevis be divided by a vertical incision, and reflected from the radius, its attachment to the bone will be better understood. The posterior interosseous nerve, and the offsets from its gangliform enlargement, may be traced more completely after the tendons of the ex- tensor of the fingers and indicator muscle have been cut at the wrist. The dorsal surface of the posterior interossei muscles of the hand may be cleaned, so that their double origin, and their insertion into the side, and on the dorsum of the phalanges, maybe observed. Between the heads of origin of these muscles the posterior perforating arteries appear. Section VII. LIGAMENTS OF THE SHOULDER, ELBOW, WRIST, AND HAND. Directions. The ligaments of the remaining articulations of the limb, which are still moist, may be examined at once ; but if any of them have become dry, they may be softened by immersion in water, or with a wet cloth, whilst the student learns the others. Dissection. For the preparation of the external ligaments of the shoulder-joint the tendons of the surrounding muscles, viz., subscapularis, supra and infraspinatus, and teres minor, must be detached from the cap- sule ; and as these are united with it, some care will be needed not to open the joint. Shoulder Joint. This ball and socket joint (fig. 89) is formed be- tween the head of the humerus and the glenoid fossa of the scapula. In- closing the articular ends of the bones is a fibrous capsule lined by a syno- vial membrane. A ligamentous band (glenoid ligament) deepens the shallow scapular cavity for the reception of the large head of the humerus. The bones are but slightly bound together by ligamentous bands, for, on the removal of the muscles, the head of the humerus may be drawn from the scapula for the distance of an inch. The capsular ligament (fig. 75, surrounds loosely the articular ends of the bones ; it is thickened above and below, and receives fibres from the contiguous tendons. At the upper edge it is fixed around the articular surface of the scapula, where it is connected with the long head of the triceps. At the lower edge the ligament is fixed (fig. 89) to the neck of the humerus close to the articular surface above, but at a little distance therefrom below ; and its continuity is interrupted between the tuberosities (5) by the tendon of the biceps muscle, over which it is continued along the bicipital groove (fig. 75). On the inner side there is generally an aperture in the LIGAMENTS OF SHOULDER. 291 capsule, below the coracoid process, through which the synovial mem- brane of the joint is continuous with the bursa beneath the tendon of the subscapularis. The following muscles surround the articulation : above and behind are the supraspinatus, infraspinatus, and teres minor ; below, the capsule is only partly covered by the subscapularis ; but internally it is well sup- ported by the last-named muscle. On tlie front of the capsule is a rather thick band of fibres — the coraco- humeral or accessory ligament (fig. 75, ®), which springs from the base of the coracoid process of the scapula, and widening over the front of the joint, is attached to the margins of the bicipital groove, and to the tube- rosities. Dissection. To see the interior of the articulation, cut circularly through the capsule near the scapula. When this has been done the attachment of the capsule to the bones, the glenoid ligament, and the tendon of the biceps will be manifest. The tendon of the biceps muscle arches over the head of the humerus, and serves the {)urpose of a ligament in restraining the upward and out- ward movements of that bone. It is attached to the upper part of the glenoid fossa of the scapula (fig. 89, c?), and is united on each side with the glenoid ligament. At first fiat, it afterwards becomes round, and en- tering the groove between the tuberosities of the humerus, it is surrounded by the synovial membrane. Fig. View of the Interior of the Shoulder-joint. a. Attacliment of the capsule to the neck of c. Glenoid ligament around the glenoid fossa. the humerus. d. Teudou of the biceps fixed to the top of the b. Interval of the bicipital groove. fossa. The glenoid ligament (fig. 89, c) is a firm fibro-cartilaginous band, which surrounds the fossa of the same name, deepening it for the reception of the head of the humerus. It is about two lines in depth, and is con- nected in part with the sides of the tendon of the biceps ; but most of its fibres are fixed separately to the margin of the glenoid fossa. The synovial membrane lines the articular surface of the capsule, and is continued through the aperture on the inner part to join the bursa beneath the subscapular muscle. The membrane is reflected around the tendon of the biceps, and lines the bicipital groove of the humerus. 292 DISSECTION OF THE UPPER LIMB. Articular surfaces (fig. 89). The convex articular head of the humerus is two or tliree times larger than the hollow in the scapula, and forms rather less than the half of a sphere. The head of the bone is joined to the shaft at an angle as it is in the femur, and a rotatory movement is pos- sessed by the humerus in consequence. The glenoid surface of the scapula is oval in form with the large end down, and is very shallow ; it is not large enough to cover the head of the humerus. Movements. In this joint there is the common motion in four direc- tions, with the circular or circumductory ; and in addition a movement of rotation. In the swinging or to and fro movement., the carrying forwards of the humerus constitutes flexion, and the moving it backwards, extension. Flexion is freer than extension ; and when the joint is most bent the scapula, rotating on its axis, follows the head of the humerus, so as to keep the centre of the glenoid fossa applied to the middle of the articular surface of the arm-bone. In extension the articular surface of the scapula does not move after the humerus. During these movements the head of the hone rests in the bottom of the glenoid fossa, turning forwards and backwards around a line represent- ing the axis of the head and neck ; and it cannot be dislodged by either the rapidity or the degree of the motion. The muscles have more influence than the loose capsule in controlling the swino'ino; motion. Abduction and adducti on. When the limb is raised, it is abducted, and when depressed, adducted ; and in both cases the humerus rolls on the scapula which is fixed. During abduction the head of the humerus, descends to the lower and larger part of the glenoid fossa, and projects beyond it against the cap- sule ; whilst the great tuberosity rubs against the arch of the acromion. In this condition a little more movement down of the head either by muscles depressing it, or by force elevating the farther end of the bone, will throw it out of place, giving rise to dislocation. In adduction the head of the bone rises into the socket, the limb meets the trunk, and the tense capsule is set at rest. After the reduction of a dislocation the limb is fixed to the side in this position of security against further displacement. In circumduction the humerus passes in succession through the four difierent states before mentioned, and the limb describes a cone, whose apex is at the shoulder and base at the digits. notation. There are two kinds of rotatory movement, viz., in and out ; and in each the motion of the head and shaft of the bone has to be considered. In rotation in, the great tuberosity is turned forwards, and the head rolls from before back across the glenoid fossa so as to projec.t behind. The shaft is moved forwards round a line lying on its inner side, which reaches from the centre of the head to the inner condyle. In rotation out, the osseous movements are reversed : thus the tuberosity turns back, the head rolls forward so as to project in front, and the shaft is carried back around the line before said. The upper thickened part of the ca})suie will be tightened in rotation, but the muscles are the chief agents in checking the movements. Dissection. To make the necessary dissection of the ligaments of the LIGAMENTS OF ELBOW. 293 elbow, the brachiiilis anticiis must be taken away from the front, and the triceps from the back of the joint. The muscles connected with the outer and inner condyles of the humerus, as well as the supinator brevis and the flexor profundus, are to be removed. 'With a little cleaning the four ligaments — anterior, posterior, and two lateral — will come into view. The interosseous membrane between the bones of the forearm will be prepared by the removal of the muscles on both surfaces. The Elbow Joint (fig. 90). In this articulation the lower end of the humerus is received into the hollow of the ulna, so as to produce a hinge- like arrangement; and the upper end of the radius assists to form part of the joint. Where the bones touch the surfaces are covered with cartilage, and their articular ends Fig- 90. are kept in place by the following ligaments : — The external lateral ligament is a roundish fas- ciculus, which is attached by one end to the outer condyle of the humerus, and by the other to the orbicular ligament around the bead of the radius. A few of the posterior fibres pass backwards to the external margin of the ulna. The internal lateral ligament is triangular in shape. It is pointed at its upper extremity, and is connected to the inner condyle of tlie humerus. The fibres diverge, and are inserted in this way: — The anterior, which are the strongest, are fixed to the edge of the coronoid process ; the posterior are attached to the side of the olecranon ; whilst a few middle fibres join a transverse ligamentous band over the notch between the olecranon and the coro- noid process. The ulnar nerve is in contact with the ligament; and vessels enter the joint by an aperture beneath the transverse band. The anterior ligament is thin, and its fibres are separated by intervals in which masses of fat are lodged. By its upper edge the ligament is inserted into the front of the humerus, and by its lower into the front of the coronoid process and the or- bicular ligament. The brachialis anticus muscle covers it. The posterior ligament is much thinner and looser than the anterior, and is covered completely by the triceps muscle. Superiorly it is attached to the humerus above the fossa for the olecranon ; and inferiorly it is inserted into the olecranon. Some few fibres are transverse between the mar- gins of the fossa before mentioned. Dissection. Open the joint by an incision across the front near the humerus, and disarticu- The Ligamexts op the El- bow JofNT, AND the Shaft of the Kadius AND Ulna (Bourgery aud Jacob). 1. Capsule of the elbow joint. 2. Oblique ligament 3. Interosseous ligament. 4. Aperture for bloodves- sels. 5. Tendon of the biceps. late the bones, in order that the articular surfaces may be seen. The synovial membrane of the joint can be traced from one bone to another along the inner surface of the connecting ligaments. It projects between the radius and the orbicular ligament, and serves for the articu- lation of the head of that bone with the small sigmoid cavity of the ulna. 294 DISSECTION OF THE UPPER LIMB. Articiilar surfaces. The liumerus presents inferiorly two distinct ar- ticular faces for the bones of the forearm. The one for the radius, on the outer side, consists of a rounded eminence (capitellum) on the front of the bone, which is covered with cartilage only on the interior aspect. The surface in contact with the ulna is limited internally and externally by a prominence, and liollowed out in the centre (troclilea). On the front of the humerus above the articular surface are two depressions which receive the coronoid process and tlie head of the radius during flexure of the joint; and on the posterior aspect is a large fossa for the reception of the olecranon in extension of the joint. On the end of the ulna the large sigmoid cavity is narrowed in the cen- tre, but expanded in front and behind (fig. 91). A slightly raised line extends from front to back, and is received into the hollow of the trochlea of the humerus. Across the bottom of the cavity the cartilage is wanting completely, or for a greater or smaller distance. The end of the radius presents a circular depression with a raised mar- gin. In the bent state of the joint the hollow of the radius fits on the outer eminence of the humerus, and the bone is supported during rotation of the limb. Movement. This joint is like a hinge in its movements, and permits only flexion and extension. In flexion the bones of the forearm move forwards, each on its own articular surface, so as to leave the back of the humerus uncovered. The extent is checked by the meeting of the bones of the arm and forearm. Owing to the slanting surface of the humerus the hand falls inside the limb when the joint is fully bent. The ligaments are relaxed, with tlie exception of the following, viz., the posterior, and the hinder part of the internal lateral. In extension the ulna and radius are carried back over the articular sur- face of tlie humerus until they come into a line with the arm-bone. This movement is checked by the olecranon touching the humerus. The anterior ligament, and the fore part of the internal lateral ligament are made tight, but the hinder fibres of the internal lateral are relaxed. Union of the Radius and Ulna. The radius is connected with the ulna at both ends by means of distinct ligaments and synovial membrane; and the shafts of the bones are united by interosseous ligaments. Upper radio-ulnar articulation. In this joint the head of the radius is received into the small sigmoid cavity of the ulna, and is kept in place by the following ligamentous band : — The annular or orbicular ligament (fig. 91, a) is about one-third of an inch wide, and is stronger behind than before; it is placed around the prominence of the head of the radius, and is attached to the anterior and posterior edges of the small sigmoid cavity of the ulna. Its upper border, the widest, is connected with the ligaments of the elbow joint; but the lower is free, and is applied around the neck of the radius. In the socket formed by this ligament and the cavity of the ulna, the radius moves freely. The synovial membrane is a prolongation of that lining the elbow joint; it projects inferiorly between the neck of the radius and the lower margin of the annular ligament. Ligaments of the shafts of the bones. The aponeurotic stratum con- necting together the bones in nearly their whole length consists of the two following parts : — RADTO-ULNAR JOINTS. 295 The interosseous membrane (fig. 90, is a thin fibrous layer, which is attached to the contiguous margins of the radius and ulna, and forms an incomplete septum between the muscles on the front and back of the fore- arm. Most of its fibres are directed obliquely inwards towards the ulna, though a few on the posterior surface have an opposite direction. Superiorly the membrane is wanting for a considerable space, and through the interval the poste- rior interosseous vessels pass backwards. Some small apertures exist in it for the passage of vessels ; and the largest of these (*) is about two inches from the lower end, through which the anterior interos- seous artery turns to the back of the wrist. The membrane gives attachment to the deep muscles. The round ligament (fig. 90, is a slender band above the interosseous mem- brane, whose fibres have a direction oppo- site to tliose of the membrane. By one end it is fixed to the front of the coronoid process, and by the other to the radius be- low the tubercle. Tlie ligament divides the space above the interosseous membrane into two parts. Oftentimes this band is not to be recognized. The lower radio-ulnar articulation cannot be well seen till after the examination of the wrist joint (p. 297). Movement of the radius. The radius moves forwards and backwards around the ulna. The forward motion, directing the palm of the hand towards the ground, is called pronation ; and the backward, by which the palm of the hand is placed upwards, is named supination. In pronation the upper end of the bone rotates within the band of the orbicular ligament without shifting its position to the ulna. The lower end, on the contrary, moves over the ulna from tlie outer to the inner side, describing half a circle ; and the shaft crosses obliquely that of the ulna. In supination the lower end of tlie radius turns backwards over the ulna ; the shafts come to be placed side by side, the radius being external ; and the upper end rotates from within out in its circular band. In these movements the radius revolves round a line, internal to the shaft, which is prolonged upwards through the neck and head of the bone, and downwards through the centre of a circle of which the small sigmoid cavity of the ulna is a segment (Ward). The upper end of the bone is kept in place by tlie orbicular ligament ; the lower end by the triangblar tibro-(*artilage ; and the shafts are united by the interosseous ligament, which is tightened in supination, and is re- laxed in pronation. In fracture of either bone the movements cease ; in the one case be- cause the radius cannot be moved except it is entire ; and in the other, because the ulnar support is wanting for the revolving radius. Dissection. To see the ligaments of the wrist-joint, the tendons and the annular ligaments must be removed from both the front and back ; and Fi-. 91. View of the Orbicular Ligament ( a) OP THE Radius, which retains THE UPPER END OF THE BONE AGAINST THE Ulna. 296 DISSECTION OF THE UPPER LIMB. the fibrous structures and the small vessels should be taken from the sur- face of the ligaments. Fio-. 92. The Wrist Joint (fig. 92). The lower end of the radius, and the first row of the carpal bones, except the os pisiforme, enter into the wrist- joint. Four ligaments maintain in contact the osseous surfaces, viz., an- terior and posterior, and two lateral. The ulna is shut out from this articu- lation by means of a piece of fibro- cartilage. The external lateral ligament is a short and strong band, which inter- venes between the styloid process of the radius and the outer part of the scaphoid bone. The internal lateral ligament is smaller than the external, but is longer than it. It is attached by one end to the styloid jirocess of the ulna, and by the other to the rough, upper })art of the cuneiform bone. Some of the anterior fibres are continued to the pisiform bone. The anterior ligament (fig. 92, takes origin from the radius and the fibro-cartilage, and is inserted into the first row of carpal bones, except the pisiform, at the anterior surface. The posterior ligament (fig. 95, is membranous, like the anterior, and its fibres are directed downwards and inwards. Superiorly it is attached to the radius and the fibro-cartilage ; and inferiorly it is fixed, like the anterior, three outer carpal bones of the first row, but on the posterior Fkont View of the Articulations of the Wrist Joint, and Carpal and Meta- carpal Bones (Bourgery and Jacob). 1. Anterior ligament of the wrist joint. 2. Capsule of the joint of the metacarpal hone of the thumh with the os trapezium. 3. Pisiform hone, with its separate joint and ligamentous hands. 4. Transverse hands to the head of the meta- carpal bones. to the aspect. Dissection. To see the form of the articulating surfaces, the joint may be opened by a transverse incision through the posterior ligament, near the bones of the carpus. Articular surfaces. The end of the radius, and the fibro-cartilage uniting it with the ulna, form aii arch for the reception of the carpal bones (fig. 93) ; and the surface of the radius is divided by a prominent line into an external triangular, and an internal square imjiression. The three bones of tlie first carjial row constitute, a convex eminence (fig. 94), which is received into tlie hollow before mentioned in this way : The scaphoid bone {a) is opposite tlie external mark of the radius ; the semi- lunar bone (5) touches the square impression, and all or part of the trian- gular fibro-cartilage ; whilst the cuneiform bone (c) is in contact with the capsule (Ileiile), and sometimes with jiart of the fibro-cartilage. The synovial membrane has tlie arrangement common to simple joints. This joint communicates occasionally with the lower radio-ulnar articula- tion by means of an aperture in the fibro-cartilage separating the two. Movement. The wrist is a condyloid articulation, and possesses angular motion in four different directions, with circumduction. LIGAMENTS OF WRIST JOINT. 297 Flexion and extension. In flexion the hand is moved forwards and in- wards, whilst the carpus rolls on the radius from before back, and projects behind, stretching the posterior ligament. In extension the hand is car- ried backwards and outwards, and the row of carpal bones moves in the opposite direction, viz., from behind forwards, so as to cause the anterior ligament to be tightened. The hinder movement is freer than the forward. Abduction and adduction. The row of carpal bones moves transversely inwards in the former, and outwards in the latter state ; and the move- ment is freer towards the ulnar than the radial side. The latter ligaments are put on the stretch, the inner in abduction and the outer in adduction ; and the motion is limited on the outer side by the meeting of the styloid processes of the radius with the scaphoid bone. Circumduction. The hand describes a cone in this movement, whose apex is at the wrist and base at the digits ; and it moves more freely in extension and adduction than in the opposite directions. Lower Radio-ulnar Articulation. In this articulation the con- vexity of the end of the ulna is received into a concavity on the radius ; an arrangement just the opj)osite to that be- tween the upper ends of the bones. Fig- 93. The chief bond of union between the bones is a strong fibro-cartilage ; but a kind of capsule consisting of scattered fibres, sur- rounds loosely the end of the ulna. The triangular jibro-cartilage (fig. 93, c) is placed transversely beneath the end of the ulna, and is thickest at its margins and apex. By its base the cartilage is fixed to the ridge which separates the carpal from the ulnar articulating surface of the radius ; and by its apex to the styloid process of the ulna, and the depression at the root of that point of bone. Its margins are united with the con- tiguous anterior and posterior ligaments of the wrist joint ; and its surfaces enter into different joints, viz., the wrist, and the lower radio-ulnar. It serves to unite the radius and ulna, and to form part of the socket for the carpal bones. Occasion- ally it is perforated by an aperture. The synovial membrane (membrana sacciformis) is very loose, from which circumstance it has received its name, and ascends between the radius and the ulna : it is separated from that of the wrist-joint by the triangular fibro-cartilage. The Wrist Joint opened to show THE ARCH FORMED BY THE Bones OF THE Forearm with the unit- ing Fibro-cartilage, c. a . Radius, ft. Ulua. The use of this articulation is referred to with the movements of the radius (p. 295). Union of the Carpal Bones. The several bones of the carpus are united into two rows by dorsal, palmar, and interosseous bands : and the two rows are connected to each other by separate ligaments. Dissection. The articulation of the carpal bones with each other will be prepared by taking away all tlie tendons from the hand, and cleaning carefully the whole of the connecting ligamentous bands. Two distinct ligaments of the pisiform bone to the unciform and fifth metacarpal are to be defined in the palm. 298 DISSECTION OF THE UPPER LIMB. At tlie same time the ligamentous bands uniting the metacarpal with the carpal^bones and with one another should be dissected. Bones of the first row (fig. 94). The os semilunare is united to the lateral bones, viz., scaphoid and cuneiform by a dorsal (fig. 94, d), and a 'palmar transverse band ; as well as, it is said, by an interosseous ligament at the upper part of the continuous surfaces.^ The pisiform bone is articulated to the front of the cuneiform by a dis- tinct capside and a synovial membrane (fig. 92, ^). It has further two special firm ligaments : one of tliese is attached to the process of the os unciforrne, and the other to tlie base of the fifth metacarpal bone. The hones of the second row are connected together in the same way as those of tlie first, viz., by a dorsal and palmar band of fibres from one bone to another. Between the contiguous rough surfaces of the several ossicles are interosseous ligaments, one in each interval. Movement. Only a small degree of gliding motion is permitted between the ditferent carpal bones, in consequence of the fiattened articular sur- faces, and the interosseous ligaments uniting one to another ; and this is less in the second than in the first row. One row with another (transverse carpal joint, fig. 94). The two rows of carpal bones are connected by an anterior and posterior, and two lateral ligaments. The anterior ligament (p) consists of strong irregular fibres, and inter- venes between the two rows (except the pisiform) on the palmar, aspect. The posterior ligament, which is longer and looser, and the greater num- ber of whose fibres are transverse, has a corresponding attachment on the dorsal aspect of the same bones. Fig. 94. a. Scaphoid hone. b. Semilunar. c. Cuneiform. d. Dorsal transverse bands between those bones. e. Trapezium bone. /. Trapezoid. g. Os magnum. h. Unciform. i. Dorsal transverse bands joining the bones. Ic. External lateral ligament of the iuteicarpal joint. 1. Internal lateral. p Anterior ligaments. Articulations of one Carpal Bone with another, and of the two rows with each OTHER. The Joint between the two rows is opened behind. Of the lateral ligaments the external {f) is the best marked, and ex- tends between the os trapezium and the scaphoid bone ; the internal liga- ment (/) reaches between tlie cuneiform and unciform bones. Dissection. After the division of the lateral and posterior ligaments, 1 Interosseous ligaments in this row, distinct from the other bands, can scarcely be said to exist. CARPO-METAC ARPAL JOINTS. 299 tlie one row of bones may be separated far enough from the other, to allow a sight of the articular surfaces. Articular surfaces. The first row of carpal bones (except pisiform) forms internally an arch with the scaplioid (a), semilunar (t/), and cunei- form bone (c), whose hollow is turned towards the second ; and externally a prominence with the scaphoid (a) which is received into a concavity in the otliei' row. In the second row the os magnum (^) and os unciforme (k) present a condyloid projection, which is received into the arch before mentioned ; but the two outer bones (trapezium and trapezoid, e and /') are much below the level of the others, and form a slight hollow for the reception of the outer part of the scaphoid bone. One synovial membrane serves for the articulation of all the carpal bones, except the pisiform with the cuneiform. Lining the joint between the two rows of the carpus, tlie membrane sends upwards and downwards prolongations between the individual bones. The offsets upwards are two, and they sometimes join the synovial membrane of the wrist joint ; but the offsets in the opposite direction are three, and may be continued to all, or only to some of the articulations between the four inner metacarpal with their carpal bones. Alovements. The transverse carpal joint is partly condyloid, but only forward and backward motion is permitted. All lateral and circumduc- tory movement is arrested, if the rows are closely applied together, by tlie scaphoid striking against the os magnum on the one side, and the cunei- form against the unciform on the other. Flexion. As the hand is bent forwards the lower row of carpal bones moves backwards, and renders pro- minent the posterior ligament. This motion is also brought into play in full bending of the wrist. Extension. The backward move- ment is freer than flexion. As the lower car{)al row moves towards the palm, its progress is checked by the anterior ligament of the joint, and by the strong flexor tendons. Union of the Metacarpal Bones. The metacarpal bones of the four fingers are connected at their bases by the following liga- ment : A superficial dorsal (fig. 95) and 'palmar fasciculus of fibres passes transversely from one bone to the next ; and the bands in the palm are the strongest (fig. 92). Besides, there is a short interosseous ligament between the contiguous rough sur- faces of the bones. Lateral union. Where the meta- carpal bones touch they are covered by cartilage ; and the articular sur- faces are furnished with prolongations of the synovial membrane serving for their articulation with the carpus. At the anterior extremities the same four metacarpal bones are con- Fig. 95. PosTEKiOR Ligaments of the Wrist, and Carpal and Metacarpal Bones (Bour- gery and Jacob), 3. Posterior radio-carpal. 2. Carpo-metacarpal joint of the thumb. .3, 3. Transverse bands between the bases of the metacarpal bones. 300 DISSECTION OF THE UPPER LIMB. nected by the deep transverse ligament which was seen in the dissection of the hand (p. 280). Union of the Metacarpal and Carpal Bones. The metacarpal bones of tlie fingers are articulated with the carpal bones after one plan ; but tlie bone of the thumb has a separate joint. Tlie metacarpal hone of the thumb articulates with the os trapezium ; and the ends of the bones are incased in a separate capsular ligament (fig. 92, ^). The joint is furnished with a synovial membrane which is simple in its arrangement. Tlie thumb-joint possesses angular movement in opposite directions, with opposition and circumduction, thus : — Flexion and extension. When the joint is flexed the metacarpal bone is brought into the jialm of the hand, without the ball of the thumb being turned to the tips of the fingers. Extension of the joint is very free, and by it the metacarpal bone is removed from the palm towards the outer border of the forearm. Abduction and adduction. By these movements the metacarpal bone is placed in contact with, or removed from the fore finger. Opposition. In this movement the ball of the thumb is turned towards the tij) of each finger by a half circumductory motion of the metacarpal bone ; and in picking up a pin the joints of the thumb, and the two last joints of the fingers will be bent. The metacarpal bones of the fingers receive longitudinal bands from the carpal bones on both aspects, thus : — The dorsal ligaments (fig. 9o) are two to each, except to the bone of the little finger. The bands of the metacarpal bone of the fore finger come from the os trapezium and os trapezoides; those of the third metacarpal are attached to the os magnum and os trapezoides ; the bone of the ring finger receives its bands from the os magnum and os unciforme ; and to the fifth metacarpal bone there is but one ligament from the unciform. The palmar ligaments (fig. 92) are weaker and less constant than the dorsal. There is one to each metacarpal bone, except that of the little finger. These ligaments may be oblique in direction ; and a band may be divided between two, as in the case of the ligament attached to the os tra- pezium and the second and third metacarpals. Sometimes one or more may be wanting. On the ulnar side of the metacarpal bone of the middle digit is a longi- tudinal lateral band, which is attached above to the os magnum and unci- forme, and below to the rough uinar side of the base of the above mentioned bone. Sometimes this band isolates the articulation of the last two meta- carpals with the unciform bone from the remaining carpo- metacarpal joint; but more frequently it is divided into two parts, and does not form a com- plete {)artition. This band may be seen by opening behind the articulation between the unciform and the last two metacarpal bones ; and by cutting through the transverse ligaments joining the third and fourth metacarpals so as to allow their separation. Movement. Scarcely any appreciable antero-posterior movement exists in the articulations of the bases of the metacarpal bones of the fore and middle fingers; but in the ring and little fingers the motion is greater, with slight abduction and adduction. Dissection. The articulating surfaces of the bones in the carpo-meta- METACARPAL BONE AND FIRST PHALANX. 301 carpal articulation may be seen by cutting througb the rest of the liga- ments on the posterior aspect of the hand. Articular surfaces. Tlie metacarpal bone of the fore finger presents a hollowed articular surface, which receives the prominence of the os tra- pezoides, and articulates laterally with the os trapezium and os magnum. The middle finger metacarpal articulates with the os magnum. The metacarpal bone of the ring finger touches the unciform bone and the os magnum. And the little finger bone is opposed to the os unciforme. Synovial membranes. Usually two synovial membranes are inter[)Osed between the carpal and metacarpal bones, viz., a separate one for the bone of the thumb, and offsets of the common carpal synovial sac (p. 299) for the others. Sometimes there is a distinct synovial sac for the articulation of the os unciforme with the two inner metacarpals. Interosseous ligaments. The interosseous ligaments between the bases of the metacarpal bones may be demonstrated by detaching one bone from another. There are also strong fibrous pieces between all the carpal bones in the second row ; and slight ones are described as present on each side of the os semilunare in the first row. Dissection. For the examination of the joint between the head of the metacarpal bone and the first phalanx of the finger, it will be requisite to clear away the tendons and the tendinous expansion around it. A lateral ligament on each side, and an anterior thick band are to be defined. One of the joints may be opened to see the articular sui-faces. The same dissection may be made for the articulations between the pha- langes of the finger. 96). into In the Fio:. 96. Union of Metacarpal Bone and First Phalanx (fig. this joint the convex head of the metacarpal bone is received glenoid fossa of the phalanx, and the two are retained in contact by the extensor and flexor tendons, and by the following liga- ments : — The lateral ligament (a) is the same on both sides of the joint. Each is triangular in form : it is attached by its upper part to the tubercle on the side of the head of the metacarpal bone, and below it is inserted into the side of the phalanx and the anterior ligament. The anterior ligament fh') is a longitu- dinal band, which is fixed firmly to the phalanx, but loosely to the metacarpal bone. It is fibro-cartilaginous in texture, and is grooved for the flexor tendon : to its sides the lateral ligaments are attached. Covering the upper part of the joint is the extensor tendon ; this takes the place of a dorsal ligament, and sends down an expansion on each side which serves as a capsule to the articulation. The synovial membrane of the joint is a simple sac. In the articulation of the thumb two sesamoid bones are connected with the anterior ligament, and receive most of the fibres of the lateral liga- ments. Movements. Motion in four opposite directions, and circumduction, exist in these condyloid joints. 302 DISSECTION OF THE UPPER LIMB. Extension and flexion. The phalanx moves ba-ckwards in extension, so as to give an angle with the metacarpal bone. The anterior ligament and the flexor tendons are stretched, and control the movement. In flexion the phalanx glides forwards under the head of the metacarpal bone, and leaves this exposed to form the knuckle when the finger is shut. The lateral ligaments and the extensor tendon are put on the stretch as the joint is bent. Abduction and adduction are the lateral movements of the finger from or towards the middle line of the hand. The lateral ligament of the side of the joint which is convex will be tightened, and the other will be relaxed. The circumductory motion is less impeded in the thumb, and in the fore and little fingers than in the others ; and in the thumb it allows the turn- ing of the last phalanx towards the other digits in the movement of oppo- sition. Union of the Phalanges. The ligaments of the first joint are simi- lar to those in the metacarpo-phalangeal articulation, viz., two lateral and an anterior. The lateral ligaments are triangular in form. Each is connected by its apex to the side of the phalanx near the anterior part ; and by its base to the contiguous phalanx and the anterior ligament. The anterior ligament has the same mode of attachment between the extremities of the bones as in the metacarpo-phalangeal joint, but it is not so strong ; and the extensor tendon takes the place of a posterior band as in that articulation. There is a simple synovial membrane present in the joint. The joint of the second with the last phalanx is like the preceding in the number and disposition of its ligaments ; but all the articular bands are much less strongly marked. Articular Surfaces. The anterior end of each phalanx is marked by a pulley-like surface. The posterior end presents a transversely hollowed fossa, and is provided with a crest which fits into the central depression of the opposed articular surface. Movements. Tlie two interphalangeal joints can be bent and straight- ened like a hinge. Flexion and extension. In flexion, the farther phalanx moves under the nearer in each joint, and the motion is checked by the lateral ligaments and the extensor tendon : in the joint between the middle and the meta- carpal phalanx this movement is most extensive. In extension the farther phalanx comes into a straight line with the nearer one and the motion is stopped by the anterior ligament and the flexor tendons. CHIEF ARTERIES OF THE UPPER LIMB 303 TABLE OF THE CHIEF ARTERIES OF THE UPPER LIMB. r 1. Axillary I artery. f Superior thoracic acromial thoracic long tlioracic alar thoracic I subscapular . . . external mammary anterior circumflex L posterior circumflex. C Muscular < inferior acromial ( humeral thoracic. Dorsal artery muscular Tnfrasca- pular 2. brachial artery. f To coraco-brachialis superior profunda . nutritious inferior profunda . . anastomotic ! Muscular to triceps and anconeus anastomotic. S Muscular to triceps ( anastomotic. muscular. The subclavian is continued in the j arm by ... . f Recurrent muscular superficial volar posterior carpal 3. radial artery. anterior carpal metacarpal dorsal of the thumb of the index finger princeps pollicis raJialis indicis deep arch . , r Recurrent t ' perforating interosseous communicating. 4. ulnar artery. f Anterior recurrent posterior recurrent interosseous / . . muscular V Anterior . posterior. i Nutritious ( muscular. < Recurrent ( muscular. dorsal of the hand, or metacarpal . . . Dorsal carpal metacarpal or inter- osseous. anterior carpal superficial arch r Communicating t ' four digital branches cutaneous muscular. 304 SPINAL NERVES OF THE UPPER LIMB TABLE OF THE SPINAL NERVES OF THE UPPER LIMB. r Anterior thoracic . J f Superior subscapular . . . < inferior ( long. circumflex . Articular cutaneous to teres minor to deltoid. nerve of Wrisberg. C Small cutaneous iuternal cutaneous . < anterior of forearm ( posterior of forearm. BkACHT AL Plexus gives j off" below the ’ clavicle . . r To coraco-brachialis I biceps and musculo-cutaueous brachialis anticus cutaneous external of forearm t articular to carpus. I To pronator teres to muscles of forearm, except flexor iilnarus and part of profundus anterior interosseous cutaneous palmar to muscles of thumb in part five digital branches. ulnar L Articular to elbow to flexor carpi ulnaris to flexor profundus in part cutaneous branch of forearm and palm dorsal cutaneous of the hand superficial palmar division deep palmar nerve. ( Communicating < two digital ( branches. musculo-spiral ' Internal cutaneous to triceps and anconeus external cutaneous to supinator and extensor radialis , ^ long us ^ . . , S Muscular posterior interosseous . . . . j articular. r Cutaneous of back of J thumb, and of first L radial -j fingers and half the next. CAVITY OF THE THORAX. 305 CHAPTER lY. DISSECTION OF THE THORAX. Section I. CAVITY OF THE THORAX. The cavity of the thorax is the space included by the spinal column, the sternum and ribs, and by certain muscles in the intervals of the bony framework. In it the organs of respiration, and the heart with its great vessels are lodged : and through it the gullet, and some vessels and nerves are transmitted. Dissection. When the soft parts covering in front the bony parietes of the thorax have been examined and taken away, the cavity is to be opened by removing a portion of the anterior boundary. To make a sufficient opening in tlie thorax, the sternum is to be sawn through opposite the in- terval between the first two ribs, and again between the cartilages of the fifth and sixth ribs. After detaching the lining membrane (pleura) from the inner surface of the chest, the student is to cut through the true ribs, except the first and seventh,^ as far back as he can conveniently reach. The loose sternum and the ribs can be removed by dividing the internal mammary vessels, the triangularis sterni, and the intercostal muscles in the first and sixth spaces. The bag of the pleura, and the cavity with its contents will be now ready for examination. The sternum and the cartilages of the ribs will be required hereafter for the dissection of the ligaments. Form. Tlie included cavity is irregularly conical, with the apex above and the base down ; and it appears, from the collapsed state of the lungs, to be only partly filled by the contained viscera, but during life the whole of the now vacant space is occupied by the expanded lungs. On a hori- zontal section its shape would appear somewhat cordiform ; for the cavity is flattened on the sides, is diminished in the middle line by the prominent spinal column, and is projected backwards on each side of the spine. Boundaries. On the sides are the ribs with their intercostal muscles ; whilst in front is the sternum ; and behind is the spine. Tlie base is constructed at the circumference by the last dorsal vertebra behind, by the end of the sternum before, and by the ribs on the side ; whilst the space included by the bones is closed by the diaphragm. The base is wider transversely than from front to back, and is convex towards the chest ; though at certain spots it projects more than at others. • The student must be mindful to leave those ribs uncut ; the division of them will not be advantageous to him, and will injure the dissection of the neck and abdomen. 20 806 DISSECTION OF THE THORAX. Thus in the centre it is lower than at the sides, and is on a level with the base of’ the xi})hoid cartilage. On the right side it rises to a level with the upper border of the fifth rib near the sternum ; and on the left to the corresj)onding part of the upj)er border of the sixth rib.^ From the lateral projections, the diaphragm slopes suddenly towards its attachment to the ribs, but more behind than before, so as to leave a narrow interval be- tween it and the wall of the chest. The level of this attached part will be marked by an oblique line over the side of the chest from the base of the xiphoid cartilage to the tenth rib ; but it differs slightly on the two sides, being rather lower on the left (fig. 97). The apex of the space is continued higher than the osseous boundary, and reaches into the root of the neck. Its highest point is not in the middle line, for there the windpipe, bloodvessels, &c., lie ; but it is pro- longed on each side for an inch or an inch and a half above the first rib, so that the apex may be said to be bifid. Each point projects between the scaleni muscles, and under the subclavian bloodvessels ; and in the interval between them lie the several parts passing between the neck and the thorax. Dimensions. The extent of the thoracic cavity does not correspond with the apparent size externally ; for the space included by the ribs be- low is occupied by the abdominal viscera, and the cavity reaches above into the neck. In consequence of the arched condition of the diaphragm, the depth of the S})ace varies greatly at different points. At the centre, where the depth is least, it measures about seven inches, but at the back as much again ; and the other vertical measurements can be estimated by means of the data given of the level of the base on the wall of the thorax. Alterations in capacity. The size of the thoracic cavity is constantly varying during life with the condition of the ribs and diaphragm in breathing. The horizontal measurements are increased in inspiration, when the ribs are raised and separated from one another ; and are diminished in expi- ration as the ribs approach and the sternum sinks. An alteration in depth is due to the condition of the diaphragm in res- piration ; for the muscle descends when air is taken into the lungs, in- creasing thus the cavity ; and ascends when the air is expelled from those organs, so as to restore the previous size of the space, or to diminish it in violent efforts. But the movement of the diaphragm is not equal through- out, and some parts of the cavity will be increased more than others. For instance, the central tendinous piece, which is joined to the heart-case, moves but sliglitly ; but the lateral, bulging, fleshy valves descend freely, and add greatly to tlie size of the lateral part of the chest by their separa- tion from the thoracic parietes. The thoracic cavity may be diminished by the diaphragm being pushed upwards by enlargement, either temporary or permanent, of the viscera in the iq)per part of tlm abdcmen ; or by the existence of fluid in the latter cavity. • This is the height in the dead body. The level to which it may reach in great respiratory efforts during life will be stated with the account of the Dia- phragm. REFLECTIONS OF PLEURA. 307 THE PLEURA. The pleura are two serous membranes, or closed sacs, which are re- flected around the lungs in the cavity of the thorax. One occupies the right, and the other the left half of the cavity ; they approach each other along the middle line of the body, forming a thoracic partition or medias- tinum. Each pleura is conical in shape ; its apex projects into the neck above the first rib (fig. 97), and its base is in contact with the diaphragm. The outer surface is rough, and is connected to the lung and the wall of the thorax by areolar tissue, but the inner surface is smooth and secerning. Surrounding the lung, and lining the interior of one-half of the chest, the serous membrane consists of a parietal part — pleura costnlis, and of a vis- ceral part — pleura pulmonalis. There are some differences in the shape and extent of the two pleural bags. On the right side the bag is wider and shorter than on the left ; and on the latter it is narrowed by the projection of the heart to that side. The continuity of the bag of the pleura over the lung and the wall may be traced circularly from a given point to the same, in the following man- ner: — Supposing the membrane to be followed outwards from the sternum, it may be traced on the wall of the chest as far as the spinal column ; here it is directed forwards to the root of the lung, and is reflected over the viscus, covering its suri'ace, and connecting together its different lobules. From the front of the root the pleura may be followed over the side of the pericardium to the sternum. Below the root the pleura gives rise to a thin fold, the ligamentum latum pulmonis, which intervenes be- tween the inner surface of the lung and the side of the pericardium. If the serous sac be traced above the root of the lung, it describes a circle without deflection over a viscus. The mediastinum. The median thoracic partition, or the mediastinum, is formed by the approximation of the pleural bags along the middle line, and is constructed of two layers — one being derived from each sac. About midway between the sternum and the spine the contiguous strata of the mediastinum are widely separated by the heart ; but in front of, and be- hind the heart they approach near each other. To the parts before and behind that viscus the terms ‘‘ anterior and posterior mediastina” are sometimes applied. T\\e part in front of the heart (anterior mediastinum) extends from the back of the sternum to the pericardium. Behind the second piece of the sternum the |)leural bags touch each other, but above and below that spot they are separated by an interval ; so that the space between them (inter- pleural) is narrowed at the centre, and is inclined below to the left of the middle line. In the upper part of the space are the remains of the thymus gland, and the origin of some of the hyoid and thyroid muscles ; and in the lower part is some areolar tissue, together with the triangularis sterni muscle of the left side. The part behind the heart (posterior mediastinum) intervenes between the back of the pericardium with the roots of the lungs, and the spinal column. Its lateral boundaries are the opposite pleural sacs, which are separated here by a larger interpleural interval than in front of the heart. If the pleura be divided behind the lung on the right side, the extent of the space and its contents will appear: in it are contained the different bodies on the front of the spine, viz., the aorta, the vena azygos, the thoracic 308 DISSECTION OF. THE THORAX. duct, the oesophagus with its nerves, the trachea, the splanchnic nerves at the lower part, and some lymphatic glands. Dissection. The pleura and the fat are now to be cleaned from the side of the pericardium. The root of the lung is to be dissected out by taking away the pleura and the areolar tissue from the front and back, without injuring its several component vessels. In this dissection the phrenic artery and nerve will be found in front of the root, together with a few nerves (anterior pul- monary) ; the last are best seen on the left side. Behind the root of the lung is the vagus nerve, dividing into branches; and arching above it is the large azygos vein. For the present, the arch of the aorta and the small nerves on it may be left untouched. The thymus body is a foetal organ, like the thyroid body, whose use is unknown. It occupies chiefly the upper part of the thorax ; and it may be best examined in a full-grown foetus. At birth it is about two inches in length, and is of a grayish color ; it possesses two lobes of a conical form, which touch each other. Its upper end is pointed and extends on the trachea as high as the thyroid body ; and the lower wider part reaches as far as the fourth rib. In the thorax it rests on the aortic arch and large vessels, on the left innominate vein, and on the pericardium. In the adult all that remains of the thymus is a brownish rather firm material in the interpleural space beneath the upper part of the sternum. In its perfect state it resembles much the thyroid body ; and a whitish fluid, containing lyrnph-like corpuscles, escapes from it when it is cut. CONNECTIONS OF THE LUNGS. The lungs are two in number, and are contained in the cavity of the thorax, one on each side of the spinal column. In these organs the blood is changed in respiration. The lung is of a somewhat conical form, and takes its shape from the space in which it is lodged. It is unattached, except at the inner part where the vessels enter ; and it is covered by the bag of the pleura. Its base and apex, borders and surfaces can be distinguished by differences in form ; it is divided also into lobes by fissures ; and it has a root formed out of its vessels and nerves. The base of the lung is hollow in the centre and thin at the circumfer- ence, and fits on the convexity of the diaphragm. Following the shape of that muscle, it is sloped obliquely from before backwards, and reaches in consequence much lower posteriorly than anteriorly. Its position with respect to the wall of the tliorax may be ascertained externally by taking the level of the diaphragm as a guide (p. 306) ; and it will be a rib’s breadth lower in front on the left, than on the right side (fig. 97). The apex is rounded, and projects an inch to an inch and a halt above the first rib, where it lies beneath tlie clavicle, the anterior scalenus muscle, and the subclavian artery. The anterior edge or border is thin, and overlays in part the pericar- dium. On the right side it lies along the middle of the sternum as low as the sixth costal cartilage (fig. 97). On the left side it reaches the mid- line of the cliest as low as tlie fourth costal cartilage ; but below that spot it presents a V-shaped notch (fig. 97), whose apex is opposite the outer CONNECTIONS OF THE LUNGS. 309 part of the cartilage of the fifth rib. Two fissures are seen in the border of the right lung, but only one in that of the left. The posterior border is as long again as the anterior, and projects inferiorly between the lower ribs and the diaphragm ; it is thick and vertical, and is received into the hollow by the side of tlie spinal column. The outer surface of the lung is convex, and is in contact with the wall of the thorax : a large cleft divides it into two pieces (lobes of the lung), and on the right side there is second smaller fissure. The inner surface is flat when compared with the outer ; altogether in front is the hollow cor- responding with the heart and its large vessels, which is greatest on the left lung ; and behind this, but nearer the posterior than the anterior border, is a fissure about three inches long, hihim pulmonis, which receives the vessels forming the root of the lung. Fig. 97. Diagram to show the difference in the Anterior Border of the Right and Left Lcng, the edge being indicated by the dark line; and to mark the different level of the base on the two sides. Each lung is divided incompletely into two parts or lobes by an oblique fissure, which begins near the apex, and ends in the anterior border near the base : from the form of the lung and the direction of the fissure the lower lobe is necessarily tlie^ largest. In the right lung a second horizontal fissure is directed forwards from the middle of the oblique one to the ante- rior border, and cuts olF a small triangular piece from the upper lobe : this is the third lobe of the lung. Occasionally there may be a trace of the third lobe in the left lung. Besides the difference in the number of the lobes, the right lung is larger and heavier, and is wider and more hollowed out at tlie base than tlie left ; it is also shorter by an inch. The increased length and the narrowness of the left lung are due to the absence of a large projecting body like the liver under it, and to the direction of the heart to the left side. 310 DISSECTION OF THE THORAX. The root of the lung consists of the vessels entering the fissure on the inner surface ; and as these are bound together by the pleura and some areolar tissue they form a foot-stalk, which fixes the lung to the heart and the windpipe. The root is situate at the inner surface, about midway be- tween the base and apex, and about a third of the breadth from the poste- rior border of the lung. In front of the root on both sides, are the phrenic and the anterior pul- monary nerves, the former being at some little distance from it; and an- terior to the right root is the descending cava. Behind on both sid(‘s, is the posterior pulmonic plexus; and on the left side there is, in addition, the descending aorta. Above on the right side is the vena azygos ; and on the left side, the arch of the aorta. Below each root is the fold of pleura called ligamentum latum pulmonis. In the root of the lung are collected a branch of the pulmonary artery, two pulmonary veins, and a division of the air tube (bronchus) ; small nutritive bronchial arteries and veins, and some nerves and lymphatics. The large vessels and the air tube have the following position to one another : — On both sides the bronchus is most posterior, the pulmonary veins most anterior, and the pulmonary artery between the other two. In the direc- tion from above down the position on the riglit side is, bronchus, pulmo- nary artery, and pulmonary veins ; but on the left side the bronchus and artery have changed places, consecpiently the relative position will there be artery, bronchus, and veins. Tliis difference in the two sides may be accounted for by the left branch of the air tube being at a lower level than the right. THE PERICARDIUM. The bag containing the heart is named the pericardium. It is situate in the middle of the thorax, in the interval between the pleurae of opposite sides. Dissection, Supposing the surface of the pericardium to be already cleaned, the student should next dissect out the large vessels connected with the heart, and the nerves. The large artery curving to the left above the heart is the aorta, which furnishes three trunks to the head and the upper limbs, viz., innominate to the right, next left common carotid, and left subclavian. On its left side lies the pulmonary artery. Above the arch of the aorta a large venous trunk, left innominate, crosses over the three before said arteries, and ends by uniting on the right side with the right innominate vein in the upper cava. Several small veins, which may be mistaken for nerves, ascend over the aorta, and enter this trunk. Define the branches of this vein, and especially one crossing the aortic arch towards the left side, which is the left superior intercostal vein. The large vein by the side of the aorta wdiich enters the top of the heart is the upper cava : look for the azygos vein opening into it behind. Seek the following nerves of the lel't side wdiich cross the arch of the aorta : — The nerve most to the left, and the largest, is the vagus ; the next largest in size on ' the right of the vagus is the })hrenic. Between the preceding nerves, and close to the coats of the artery, are the two following, the left superficial cardial nerve of the sympathetic, and the STRUCTURE OF PERICARDIUM. 311 cardiac branch of the left vagus ; of the two, the last is the smaller, and on the right of the other. The cardiac nerves from the left vagus and sympathetic are to be pur- sued onwards to a small plexus (superficial cardiac) in the concavity of the aorta. An offset of the [)lexus is to be traced downwards between the pulmonary artery and the aorta towards the anterior coronary artery of the heart ; and another prolongation is to be found coming forwards from the deep cardiac to the superficial plexus : this dissection is difficult, and will require care. When the pericardium is afterwards opened the nerves will be followed on the heart. Oftentimes these small nerves are destroyed in injecting the body. The pericardium is larger than the viscus it contains. Somewhat conical in form, the wider part of the bag is turned towards the diaphragm, and the narrower part u[)wards to the large vessels of the heart. Occupying the interpleural space, it is situate behind the sternum, and projects below on each side of that bone, but much more towards the left than the right side. Laterally the pericardium is covered by the pleura, and the phrenic nerve and vessels lie in contact with it. Its anterior and posterior surfaces correspond with the objects in the inter{)leural space ; and on the anterior aspect the bag is partly covered by the margin of the lungs, especially the left. The heart-case consists of a fibrous structure, which is lined internally by a serous membrane. ^\\e fibrous part surrounds the heart entirely, and is pierced by the dif- ferent vessels of that organ : it gives j)rolongations around the vessels, and the strongest of these sheaths is on the aorta. Interiorly it is united by fibres to the central tendon of the diaphragm. Tliis membrane is thickest at the upper part, and is formed of fibres crossing in different directions, many being longitudinal. When the peri- cardium has been cut open, the serous lining will be discernible. The serous sac lines the interior of the fibrous pericardium, and is re- flected over the surface of the heart. Like other serous membranes, the arachnoid for example, it has a parietal and a visceral part. After lining the interior of the fibrous case, to which it gives the shining appearance, the membrane is conducted to the surface of the heart by the different vessels. As it is reflected on the aorta and the pulmonary artery it con- tains those vessels in one tube, not passing between their contiguous sur- faces ; and at the posterior part of the pericardium it forms a pouch between the pulmonary veins of opposite sides. In front of the root of the left lung tlie serous layer forms a vertical band, the restigial fold of the pericardium (Marshal), which includes the remains of the left innomitlate vein of the foetus. On separating the pul- monary artery and bronchus, the band will be better seen. The vessels of the pericardium are derived from the aorta, the internal mammary, the bronchial, the msophageal, and the phrenic arteries. Nerves. According to Luschka the pericardium receives nerves from the phrenic, sympathetic, and right vagus. 312 DISSECTION OF THE THORAX. THE HEART AND ITS LARGE VESSELS. The heart is a hollow muscular viscus, and is the agent in the propul- sion of the blood through the body. Into it, as the centre of the vascular system, veins enter ; and from it the arteries issue. Form. When the heart is distended, its form is conical, but it is rather flattened from before backwards. Its surfaces and borders have the fol- lowing differences ; the anterior surface is slightly convex, whilst the pos- terior is nearly flat : the left border is thick and round, but the right is thin, sharp, and less firm. Size. The size varies greatly, and in general the heart of the woman is smaller than that of the man. Its avera"e weight is from ten to twelve ounces in the male, and from eight to ten in the female. The measure- ments may be said to be about four inches and three-quarters in length, three inches and a half in width, and two inches and a half in thickness. Position and Direction. The heart lies beneath the lower two-thirds of the sternum, and projects on each side, but more on the left than the right. Its axis is not parallel to, but is inclined obliquely across that of the body ; and its ])Osition is almost horizontal with the base directed backwards and to the right, and the apex forwards and to the left side. The left margin of the viscus is undermost, whilst the right is foremost. In consequence of the direction of the heart in the thorax, only some parts can be near, or in contact with the parietes ; thus the right half and the apex will correspond with the thoracic wall, though mostly with lung intervening, whilst the base is directed away from the sternum and the costal cartilages : and the left half will be undermost and deep in the cavity. Limits 98.) The limits of the whole heart are the following: the base is opposite the spinal column, and corresponds with four dorsal vertebrje (5th to 8th). The apex strikes the wall of the thorax during life just below the fifth rib, near the junction with the cartilage. The upper limit would be shown by a line across the sternum on a level with the upper edge of the third costal cartilage. And the lower limit would be marked by a line over the junction of the sternum with the xiphoid cartilage, drawn from the articulations of the sixth and seventh cartilages of the right side to the spot where the apex touches. Its lateral limits are the following. On the right it projects from one to one inch and a half beyond the middle line of the sternum, and its in- crease in this direction is constantly varying with the degree of distension of the right half of the heart. On the left side the apex projects three inches to three inches and a half from the centre of the breast bone. Component parts. The heart is a double organ, and is made up of two similar halves. In each half are two hollow portions, an auricle and a ventricle ; these on the same side communicate, and are provided with vessels for the entrance and exit of the blood. On the surface are grooves indicatory of this composition. Thus, passing circularly round the heart, nearer the base than the apex, is a groove which cuts ofi' the thin auricular from the fleshy ventricular part. A longitudinal sulcus on each surface marks the situation of a median partition between the ventricles : this sul- cus does not occu})y the mid space either on the anterior or the posterior as|)ect, but it is nearer the left border of the heart in front, and the right border behind ; so that most of the anterior sur'ace is formed by the right, and the greater part of the posterior surface by the left ventricle. COMPOSITION OF HEART. 313 The auricles are two (right and left) and receive tlieir appellation from the resemblance of the appendices to the dog’s ears : they are placed so deeply at the base of the heart, that only the tip of the right one comes forwards to the sternum. The auricles are much thinner than the ven- tricles. Fig. 98. Diagram xShowixg the Position of the Heart to the Ribs and Sternum, the soft parts being removed from the exterior of the thorax. The edge of each lung is shown by a dotted line. The ventricles reach unequal distances on the two aspects of the heart: thus the right one forms the thin right border and the greater part of the anterior surface; but the left enters alone into the apex, and constructs the left border, and most of the posterior surface of the heart. Dissection. Before 0[)ening the heart the coronary arteries are to be dis- sected on the surface, with the small nerves and veins that accompany them. The two arteries appear on the sides of the pulmonary artery, and occupy the grooves on the surface of the heart, where they are surrounded by fat : one branches over the right, and the other over the left side. With the anterior artery is a plexus of nerves, which is to be followed upwards to the superficial cardiac plexus ; and with the remaining artery another plexus is to be sought. In the groove at the back of the heart between the aui-icles and ven- tricles, the student will find the large coronary vein, and the dilated coro- nary sinus in which it ends on the right : the last should be defined and followed to its ending in the right auricle. The coronary arteries are two small vessels which are so named from their course around tlie heart : they are the first branches of tlie aorta. One is distributed mostly on the right, and the other on the left side of the heart. The right coronary branch appears on the right side of the pulmonary 314 DISSECTION OF THE THORAX. artery, and is directed onwards in the depression between the right auricle and ventricle to end in the left half of the heart on the posterior aspect. In its course branches are distributed upwards and downwards to the right half of the viscus. Two of these are of larger size than the rest: one runs on the anterior aspect of the right ventricle towards the free margin ; the other descends on the back of the heart towards the apex, along the septum between the ventricles. The left coronary hranoh is inclined behind the pulmonary artery to the left side of that vessel, and in the groove between the left auricle and ven- tricle to the back of the same side of the heart. Like the preceding artery, it furnishes offsets t€ the substance of the auricle and ventricle of its side : the largest of These descends in the anterior sulcus over the septum ven- triculorum towards the apex. The veins of the substance of the heart (cardiac) are not the same in number, nor have they the same arrangement as the arteries. There may be said to be three sets, but for the most part they are collected into one large trunk, the coronary sinus, which opens into the right auricle. The coronary sinus (fig. 99, will be seen on raising the heart to be placed in the sulcus between the left auricle and ventricle. About an inch usually in extent, it is joined at the one end by the great coronary vein (^) ; and at the other it opens into the right auricle. It is crossed by the mus- cular fibres of the left auricle. Interiorly and at its right end it receives some branches from the back of the ventricles (® and t) ; ‘^d nearly at its left extremity another vein (^), — the oblique vein (Marshall), which ascends along the back of the left auricle. On slitting the sinus with a scissors the openings of its different veins will be seen to be guarded with valves, with the exception of the oblique vein ; and at its right end is the large Thebesian valve of the right auricle. The great cardiac or coronary vein begins in front near the apex of the heart, in the substance of the ventricles. The vessel turns to the posterior surface in the sulcus between the left auricle and ventricle, and opens into the coronary sinus (fig. 99, *). It receives collateral branches in its course, and its ending in the sinus is marked by two valves. Anterior and posterior cardiac veins. Some small veins on the ante- rior part of the right ventricle open separately, by one or more trunks, into the lower part of the right auricle. Similar small veins exist over the back of the ventricles ; and one, larger than the rest, lies over the septum ventriculorum : they enter the coronary sinus by separate valved openings. Smallest cardiac. A third set of veins (venm minimm) lie in the sub- stance of the heart, and are noticed in the description of the right auricle. Cardiac nerves. The nerves for the supply of the heart are derived from a large plexus (cardiac) around the roots of the aorta, and pulmonary artery. Part of this plexus is superficial to the pulmonary artery, and ))art beneath ; and an offset is sent from each with a coronary artery. Only the superfi- cial part of the plexus can now be seen. The superficial cardiac plexus is placed below the arch of the aorta, and by the side of the ductus arteriosus. The nerves joining it are the left suj)erficial cardiac of the sympathetic, the lower cardiac of the left vagus (p. 331), and a considerable bundle from the deep cardiac plexus. A small ganglion is sometimes seen in the plexus. Inferiorly it sends off nerves on the right coromiry artery to the heart. A few filaments pass on the left division of the pulmonary artery to the left lung. NERVES OF HEART SUBSTANCE. 815 The right coronary nerves pass from the plexus to the right coronary artery, and receive near the heart a communicating offset from tlie deep cardiac plexus. The left coronary nerves are derived, as will be subsequently seen from the deep cardiac plexus, and accompany the left coronary artery to the heart. At first the nerves surround the arteries, but they soon leave the vessels, and becoming smaller by subdivision, are lost in the muscular substance of Fig. 99. A. Right auricle. B. Left auricle, with the auricula, c. 1. Coronary sinus. 2. Oblique vein. .3. Vein from the right side of the heart. 4. Left or great cardiac vein. •j--}- Veins joining the sinus from the back of the ventricles. Back of the Heart with the Coronary Sinus and its Veins. (Marshall.) the ventricles. On and in the substance of the heart the nerves are marked by small ganglia. The CAVITIES OF THE HEART may be examined in the order in which the current of the blood passes through them, viz., right auricle and ven- tricle, and left auricle and ventricle. Dissection. In the examination of its cavities the heart is not to be re- moved from the body. To open the right auricle, an incision may be made in it near the right or free border, and from tbe superior cava nearly to the inferior cava; from the centre of that incision the knife is to be carried across the anterior wall to. the auricula. By means of those cuts an open- ing will be made of sufficient size ; and on removing the coagulated blood, and raising the flaps with hooks or pieces of string, the cavity may be ex- amined. The CAVITT OF THE RIGHT AURICLE (fig. 100) is of an iiTcgular form,^ though when seen from the right side, witli the flaps held up, it has some- what the appearance of a cone, with the base to the right and the apex below and to the left. The base or wider part of the cavity is turned towards the right side, • Tfie term cavity of the auricle lias been sometimes applied to the apiiendix, and the term sinus venosus to the rest of the space here named auricle. 316 DISSECTION OF THE THORAX. and its extremities are the openings of the superior and inferior cavje. Between those vessels the cavity projects a little, and presents a slight elevation in some bodies (tubercle of Lower). Tlie apex is prolonged downwards towards the junction of the auricle with the ventricle, and” in it is the opening into the right ventricular cavity. The anterior wall is thin and loose. Near its upper part is an opening leading into the pouch of the appendix or auricula (/?), which will admit the tip of the little finger. Around and in the interior of the appendix, are fleshy bands, named musculi pectinati, which run mostly in a trans- verse direction, and form a network that contrasts with the general smooth- ness of the auricle. Fig. 100. a. Upper cava. Lower cava. e. Right auriculo-ventricular opening. d. Fossa ovalis. e. Opening of the coronary sinus. /. Foramina Thebesii, the openings of veins. g. Aperture of the pulmonary artery. h. Auricular appendix. Diagram of the two Cavities of the right side of the Heart. The posterior wall corresponds for the most part with the septum be- tween the auricles, in consequence of the position of the heart. On it, close to the inferior cava, is a large oval depression, the fossa ovalis (t/), which is tlie remains of an opening between the auricles in the foetus. In- feriorly it merges into the lower cava. A thin semi-transparent structure forms the bottom of the fossa ; and tliere is oftentimes a small oblique aperture at its upper part. Around the upper three-fourtlis of that hollow is an elevated band of muscular fibre, called annulus sen isthmus Yieus- senii, which is most prominent above and on the left side, and gradually subsides interiorly. Altogetlier at the lower part of the posterior wall is the aperture of the coronary sinus (e). Other small apertures are scattered over this surface : some lead only into de[)ressions ; but others are the mouths of veins of the substance of the heart (venm cordis minimie), and are named foramina Thebesii (/). The chief apertures in the auricle are those of the two cavre, coronary sinus, and ventricle. The opening of the superior cava (a), is in the front RIGHT AURICLE OF HEART. 317 and top of the auricle, and its direction is forwards. The inferior cava (b) enters the back part of the cavity near the septum, and is directed back- wards to the fossa ovalis (d). The auriculo-ventricular opening (e) is the largest of all, and is situate at the lowest part of the cavity. Between this and the septum is placed the opening of the coronary sinus (e) which is about as large as a turkey-quill. All the large vessels, except the superior cava, have some kind of valve. In front of the inferior cava is a thin fold of the lining membrane of the cavity, the Eustachian valve, which is only a remnant of a much larger structure in the foetus. This valve in its perfect state is semilunar in form, with its convex margin attached to the anterior wall of the vein, and the other free in the cavity of tlie auricle. It is wider than the vein opening, and its surfaces are directed forward and backwards : its free margin is often reticular. The aperture of the coronary sinus is closed by a thin fold of the lining membrane — valve of Thebesius. Tlie auriculo-ventricu- lar opening will be seen, in examining the right ventricle, to be provided with valves, which prevent blood running back into the auricular cavity. In the adult there is but one current of blood in the right auricle towards the ventricle. But in the fcetus there are two streams in the cavity : one of pure, and the other of impure blood, which cross one another in early life, but become more commingled as birth approaches. The placental or pure blood entering by the inferior cava, is directed by the Eustachian valve chiefly into the left auricle, through the foramen ovale in the sep- tum ; whilst the current of systemic or impure blood, coming in by the superior cava, flows downwards in front of tlie otlier to the right ventricle. Dissection. To see the cavity of the right ventricle, the student should pierce it with the scalpel below the opening from the auricle, and cut out interiorly near the apex of the heart without injuring the septum ventricu- lorum. A flap is thus formed, like the letter V, of the anterior part of the ventricle. In the examination of the cavity of the right ventricle, both the flap and the apex of the heart should be raised with hooks or string, so that the space may be looked into from below. The CAVITY OF THE RIGHT VENTRICLE (fig. 100) is triangular in form, and has the base turned upwards to the auricle of the same side. On a cross section the cavity would appear semilunar in shape, with the sep- tum between the ventricles convex towards the cavity. The apex of the cavity reaches tlie right border of the heart at a short distance from the tip. The base of the ventricle is sloped, and is perfo- rated by two apertures; one of these, on the right, leading into the auri- cle, is the right auriculo-ventricular opening (c) ; the other on the left, and much higher, is the mouth of the pulmonary artery {g). Tlie part of the cavity communicating with the pulmonary artery is funnel-shaped, and is named infundibulum or conus arteriosus. The anterior wall, or the loose part of the ventricle, is comparatively thin, and forms most of the anterior surface of the ventricular portion .of the heart. The posterior wall corresponds with the septum between the ventricles, and is much thicker. Over the greater part of the cavity the surface is irregular, and is marked by projecting fleshy bands of muscular fibres, the colanince carnece ; but near the aperture of the pulmonary artery the wall becomes smooth. The fleshy columns are of various sizes, and of three different kinds. Some form merely a prominence in the ventricle, as on the septum. Others are attached at each end, but free in the middle (trabeculce carnete). And a 318 DISSECTION OF THE THORAX. third set, which are fewer in number and much the largest, project into the cavity, and form rounded bundles, named muscnli papillares ; these give attachment by their free ends to the little tendinous cords of the valve of the auriculo-ventricular opening. The aiiriculo-ventricular orifice (c) is situate in the base of the ventri- cle, and is opposite the centre of the sternum, between the third costal car- tilages. It is slightly larger than the corresponding aperture of the left side of the heart. It is oval from side to side, its shape being maintained by a strong fibrous band around it ; and it measures one inch and a quar- ter in diameter. Prolonged from the circumference of the opening is a thin membranous valve, which projects into the cavity of the ventricle. Near its attach- ment to the heart the valve is undivided, but it presents three chief points at its lower margin, and is named tricuspid ; to the lower margin are attached small tendinous cords (chordte tendinese), which unite it to the muscular bundles of the ventricle. Its three slips or tongues are thus placed : — one touches the front of the ventricle ; another is in contact with the posterior wall ; and the remaining slip, the largest and most movable, is interposed between the aperture into the auricle and pulmonary artery. The tricuspid valve is constructed by the lining membrane of the heart, which incloses fibrous tissue. The central part of each tongue is strong, whilst the edges are thin and notched ; and between the primary pieces there are sometimes secondary points (Kiirschner). The chordce tendince which keep the valve in position ascend from the musculi papillares into the intervals between tlie pieces of the valve, and are connected with both.^ They end on the surface of the valve turned away from the opening ; — some reaching the attached upper margin ; others entering the central thickened j art, and the thin edge and point of the tongue. As tlie blood enters the cavity, the valve is raised so as to close the opening into the auricle ; and its protrusion into the other cavity during the contraction of the ventricle is arrested by the small tendinous cords. The valve participates in the production of the first sound of the heart. The mouth of the pulmonary artery (g) will be seen when the incision in the anterior wall of the ventricle is prolonged into it. Round in shape, it is situate on the left of the opening into the auricle, and is opposite the inner end of the second intercostal space of the left side. Its diameter is rather less than an inch. Into it the funnel-shaped part of the right ventri- cle is prolonged, and in its interior are three semilunar or sigmoid valves. Semilunar valves. Each valve is attached to the side of the vessel by its convex border ; and is free by the opposite edge, in whicli there is a slightly thickened nodule — the corpus Arantii. In the wall of the artery op[)Osite each valve is a sliglit hollow, the sinus of Vcdsalva., which is better marked in the aorta. The valves resemble the tricuspid in structure, for they are formed of fibrous tissue with a covering of the lining membrane. In each valve tlie fibres have this arrangement : there is one band along the attached mar- gin ; a second along the free edge, which is connected with the projecting nodule ; and a third set of fibres is directed from the nodule across the • The papillary muscles are collected into two principal groups, whose tendons enter the interval on each side of the anterior tongue of the valve. In the inter- val between the left and posterior segments of the valve the tendinous cords are very small, and are connected with tlie septum ventriculornm. LEFT VENTRICLE OF HEART. 319 Fi-. 101. valve, so as to leave a semilunar interval on each side near the free edge, wliich has been named lunula. The use of the valves is obvious, viz., to give free passage to fluid in one direction, and to prevent its return. Whilst the blood is entering the artery the valves are placed against the wall ; but when tlie elasticity of the vessel acts on the contained blood, the valves are thrown towards the centre of the vessel, and arrest the flow of the fluid into the ven- tricle. They are concerned also in giving rise to the second sound of the heart. Dissection. To open the cavity of the left auricle the apex of the heart is to be raised, and a cut is to be made across the p)sterior surface of the auricle from the right to the left pulmonary veins. Another short incision should be made downwards at right angles to the first. The apex of the heart must necessarily be raised during the exami- nation of the cavity. The CAVITY OF THE LEFT AURICLE (fig. 101) is smaller than that of the right side. Irregularly conical in shape, the wider part is turned towards the spinal column, and re- ceives the pulmonary veins ; and the nar- rowed part (1) opens inferiorly into the left ventricle. On the left side towards the upper part, is the aperture of the pouch of the auricula (/«), which is narrower than that in the right au- ricle. In the interior of the pouch, as well as around the entrance, are fleshy fibres (mus- culi pectinati) which resemble those before seen in the other auricle. On the part of the wall corresponding with the septum auricularum, is a superficial fossa (fig. 101, o), the remains of the oval aperture through that partition ; this is bounded below by a projecting ridge, concave upwards, which is the edge of the structure or valve that closed the opening in the foetus. This im- pression in the left auricle is above the fossa ovalis in the right cavity, because the aper- ture between the two in the foetus is an oblique canal through the septum. The apertures in this auricle are those of the four pulmonary veins, two on each side, together with the opening of communication with the left ventricle. The mouths of each pair of pulmonary veins are close to one another; those from the right lung (^) open into the extreme right of the auricle near the sep- tum, and those from the left lung {h) enter the opposite part of the cavity, near the auricula. The pulmonary veins are not provided with valves. The aperture into the ventricle (/) will be subsequently seen to have a large and complicated valve to guard it, as on the right side. In the adult the blood enters this cavity from the lungs by the pulmo- nary veins, and passes to the left ventricle by the large inferior opening Diagram of the two Cavities op THE LEFT SIDE OF THE HeART. Zf. Left pulmonary veins. i. RiKht pulmonary veins. 0 . Remains of the foramen ovale. 1. Left auriculo-ventricular open- ing. TO. Auricular appendix. n. Aperture of the aorta. 320 DISSECTION OF THE THORAX. between the two. In the foetus the lungs are impervious to the air and the mass of the circulating fluid ; and the left auricle receives its pure blood at once from the right auricle througli the aperture in the septum (foramen ovale). Dissectio7i. Tlie left ventricle may be opened by an incision along both the anterior and the posterior surface, near the septum ; these are to be joined to the apex, but are not to be extended upwards so as to reach the auricle. On raising the triangular flap the interior of the cavity will be visible. Tlie CAVITY OF THE LEFT VENTRICLE (fig. 101) is longer, and more conical in shape than that of the opposite ventricle ; and is over or almost circular, on a transverse section. The apex of the cavity reaches the apex of the heart. The base is turned towards the auricle, and is not sloped like that of the right ventri- cle; in it are the openings into the aorta (y^) and the left auricle (/). The ivalls of this ventricle are thickest, and the anterior boundary is formed by the septum ventriculorum. Its surface is irregular, like that of the right ventricle, in consequence of the projections of the fleshy columns, or carneae columnjie; but near the great artery (aorta) the surface is smoother. There are three sets of fleshy columns in this as in the right ventricle. But the set (musculi papillares), which project into the cavity, and receive the small tendinous threads of the valve, are the most marked: these are arranged chiefly in two large bundles, and spring from the anterior and posterior walls of the cavity. Tlie aperture into the left auricle {V) (auriculo-ventricular) is placed beneath the orifice of the aorta, but close to it, only a thin fibrous band intervening between the two. It is rather smaller than the corresponding aperture of the right side, being somewhat more than an inch in diameter, and is longest in the transverse direction. Placed, as before said, beneath the aortic aperture, it extends also to the right, so as to lie beneath the left extremity of the right auriculo-ventricular opening. It is furnished with a membranous valve (mitral) which projects into the ventricle. The mitral valve is stronger and of greater length than the tricuspid, and has also firmer and more tendinous cords : it takes its name from a fancied resemblance to a mitre. Attached to a fibrous ring around the aperture, as well as to the aortic fibrous ring, it is divided below by a notch on each side into two pieces. Its segments lie one before another, with their edges directed to the sides, and their surfaces towards the front and back of the cavity. The anterior tongue of the valve intervenes between the auricular and aortic openings, and is larger and looser than the posterior segment. The mitral resembles the tricuspid valve in its structure and office. Its segments consist of thicker and thinner parts; and in the notches at the sides there are also secondary pieces between the two primary segments. The tendinous cords ascend to be attached to the valve in the notches between the tongues; and they end on the segments in the same way as in the tricuspid valve, hlach of the large papillary muscles acts on both portions of the valve. When the blood enters the cavity, the pieces of the valve are raised as on the right side, and meet to close the passage into the left auricle. In combination with the tricuspid it assists in producing the first sound of the heart. STRUCTURE OF THE HEART. 321 • The opening of the aorta^ anterior to that of the auricle, is next the septum of the ventricles. Its aperture is round, and rather smaller than that of the pulmonary artery, and measures about three-quarters of an incli in diameter. It is situate opposite the inner end of the third left intercos- tal space. In its interior are three semilunar or sigmoid valves, which are larger and stronger than tlie corresponding parts in the pulmonary artery, but have a like structure and attachment. The projection in the centre of each valve, viz., the corpus Arantii, is better marked. Opposite each valve the coat of the aorta is bulged as in the pulmonary artery, though in a greater degree, and presents a little hollow on the inner side, named sinus of Valsalva. The apertures of the coronary arteries are placed behind two of the valves. Like the valves in the pulmonary artery these meet in the middle line to stop the blood passing back into the ventricle, and combine with them in causing the second sound of the heart. Position of the ventricular apertures. Two openings have been seen in each ventricle — one of the auricle of its own side of the heart, and one of an artery. The apertures of the arteries (aorta and pulmonary) are nearest the septum; and as the two vessels were originally formed from one tube, they are close together, but the pulmonary artery is the more anterior of the two. The aperture of communication with each auricle is nearer the circumference of the heart, and is posterior to the artery issuing from the lore part of the ventricle. The position of the openings to one another from before backwards has been before referred to, viz., the right is partly before the left auriculo- ventricular; and the opening of the pulmonary artery is anterior to that of the aorta, and rather higher than it. Structure. The heart is composed of strata of muscular fibres, and of certain fibrous rings with a fibro-cartilage. The structure may be studied in the heart of the sheep or ox, in which the fibres have been hardened and the connective tissue destroyed by boil- ing, so as to allow of the fibres being separated. The description of the structure of the heart may be omitted by the student till a suitable prepara- tion of the fibres can be made. The fibrous structure forms rings around the auriculo-ventricular and arterial orifices, and is prolonged into the valves connected with those openings. The auriculo-ventricular rings give attachment to the framework of fibrous tissue in the tricuspid and mitral valves. They are distinct from the bands encircling the mouths of the arteries, except at the front of the left auriculo-ventricular opening, where the auricular and arterial circles blend. An arterial ring surrounds each large artery (aorta and pulmonary), fixing those vessels, and giving attachment to some muscular fibres. It is a circular band, with three notches in the margin towards the artery; these are filled by corresponding projections of the artery, and give attach- ment internally to the sigmoid valves along their semilunar edges. The artery is connected with the band of fibrous tissue in the following manner: — Its middle coat presents three projections, which are received into the notches of the fibrous ring, being joined thereto by fibrous tissue; and the junction between the two is strengthened externally by the outer arterial coat and the pericardium, and internally by the endocardium. 21 322 DISSECTION OF THE THORAX. Fiff. 102. Behind the aortic aperture, between it and the auriculo-ventricular orifices, is a piece of Jibro-cartilage, with wliich the fibrous rings are united. The muscular fibres belong to the involuntary class, though marked with transverse strife, and form concentric layers, which inclose the cardiac cavities. In the auricles the fibres are separate from those in the ventricles. In the wall of the auricles the fibres are mostly transverse (fig. 102, or), and are best marked at the lower part, though they form there but a thin layer; and some of the fibres dip into the septum between the auricular cavities. Besides this set there are annular fibres around the appendages of the auricles, and the endings of the different veins. Lastly a few oblique fibres {c and d) pass upwards over the auricles both in front and behind. Dissection. The auricles having been learnt, separate them from the ventricles by dividing the fibrous auriculo-ventricular rings. Next clean the fieshy fibres of the ventricles by removing all the fat from the base of the heart around the two arteries (aorta and pulmonary), and from the anterior and posterior surfaces. Before cutting into the heart let the student note that the anterior surface is to be recognized by the fibres turning in at the septum, with the exception of a small band above about half an inch wide ; and that at the posterior aspect the fibres are continued from the left to the right ventricle aross the septum. Separate partly the ventricles in front along tlie septum by dividing the band near the base, and sinking the knife for about an inch into the groove be- tween them. Disjoin then the aorta and pulmonary artery along the mid- dle line, so as to leave one attached to each ventricle as in fig. 103. To show the laminar composition of the left ventricle divide its fibres in front longitudinally near the septum, and transversely about half an inch below the left auriculo-ventricular opening ; but the cut is to be very shallow, because seven layers, each about as thick as the thin end of the sc{d[)el, are to be demonstrated. From the lines of incision reflect the different layers downwards to the apex, upwards to the auriculo-ventricular aperture, and backwards into the septum. As the layers are raised the fleshy fibres will be seen to chanfire their direction ; and the outer three to be thinner than the three internal. The LEFT VENTRICLE is a hollow cone, and its wall is formed of layers of fibres, as if a flat muscle had been rolled up into a conical figure (fig. 103). Seven layers enter into the construction of the wall ; and they are Muscular Fibres of the Auricles. f Inferior cava, and e, superior cava of the right auricle. g. Right, and h, left pulmonary veins of tlie left auricle. a. Transverse fibres of the right, and 6, transverse fibres of the left auricle, entering the septum auricularum. c. Oblique fibres of the left, and d, of the right auricle. Annular fibres surround the auriculae and the veins. VENTRICULAR FIBRES OF HEART. 323 Fiff. 103. arranged into three external (1, 2, 3), tliree internal (7, 0, 5), and a central one (4). All are not prolonged equal distances on tlie ventricle, for the outermost and the innermost i-each farthest towards apex and base ; and the second external and its corresponding inner layer (sixth) extend farther than the third and the fifth. The fourth is tlie shortest of all. Consequently tlie wall is thickest about the middle third where all the layers are present, and gradually be- comes thinner upwards and down- wards, until there is only the outmost layer at the apex, and the most ex- ternal and internal (1st and 7th) at the base. (Dr. Pettigrew, Phil. Trans. 1864.) Direction of the fibres. Each stratum is formed of fleshy fibres with the undermentioned direction, sup- posin o; the ventricle standing; on the A Diagram of the arrangement of the Fibres in Layers in the Left Ventri- cle. 1. First or external layer. 2. Second external. 3. Third external. 4. Central layer. 5. The outermost of the three inner strata. apex, and the anterior surface towards the dissector. In the three external strata (1, 2, 3) the fibres are inclined downwards from the base and septum to the apex of the ventricle, and become less vertical in each. The fourth or mid layer (4) pos- sesses transverse fibres ; and it is nearer the outer than the inner surface of the wall. In the three inner strata the fibres change their direction, as is shown by 5, and are directed upwards from the apex and septum to the base of the ventricle ; so that they cross the fibres oi' the outer layers like the legs of the letter X, and, becoming more oblique in each layer, are almost vertical in the internal. Continuity of the fibres. With a piece of muscle rolled into a cone, as before said, the fibres of the different layers would be necessarily continu- ous at the apex ; but in the heart they are united at apex and base. Thus the outermost layer is continuous at tlie apex and base with the innermost, the fibres being curved in at tlie tip and out at the base. In like manner the fibres of the second layer are united with those of the sixth, and the third stratum with the fifth. From the three outer layers, fibres are con- tinued to the right ventricle at the back of the heart, forming the “ com- mon fibres.” Each of the three outer layers consists of two sets of fibres, which occupy the front and back of the ventricle. By the turning inwards of the two bundles on opposite sides of the apex, the wall is prevented from having a slanting side, like a piece of paper rolled into a cone. And by the turn- ing outwards of two sets of fibres (anterior and posterior) at the base of the ventricle from each inner layer, the sides of the auriculo- ventricular opening are made level like those of the apex. Many of the fibres of the outer layers are attached to the fibrous ring around the aorta. 324 DISSECTION OF THE THORAX. The fibres of the fourth layer are continued into the septum ventri- culorum. Dissection. To display the layers and fibres of the right ventricle, great care will be needed because of the thinness of the wall ; but the same number of layers exists in this, as on the other side of the heart. Make a vertical cut along the anterior as[)ect from the root of the ])uU monary artery to the a| ex of the ventricle ; and reflect the several layers forwards and backwards from that incision. As the three outer are raised let them be traced on the one hand into the part of the septum detached from the left ventricle ; and on the other into the left ventricle through the continuity of the common fibres behind. The RIGHT VENTRICLE possesscs seveii layers in its wall, like the left, though they are much thinner. They are arranged as in the other ven- tricle into three external, three internal, and a fourth or intermediate. In like manner the wall decreases from the centre towards the base and apex, but at the tip it is thicker than the apex of the left half of the heart (Pettigrew). Directions of the fibres. In this as in the other ventricle, the fibres of the three outer layers run down from the base to the fore part of the sep- tum and the aj ex of the heart : the outer being most vertical. In the fourth stratum the fibres have a transverse direction, as in the correspond- ing layer of the left ventricle. And in the three inner layers they are directed upwards from the apex to the base of the ventricle across the fibres of the three outer strata, the deepest being the most vertical. Continuity of the fibres. The fibres are not distinct from those of the left ventricle, but are derived in the three outer layers from the “ common fibres” and the septum, and from the auriculo-ventricular opening. They are then continued forwards to the front of the septum ventriculorum, where they leave the surface, and bending back construct the right part of the septum ; at the back of that partition they blend with the “ common fibres” of the left ventricle. The fourth layer fibres are continuous for the most part with the “ common fibres” crossing the posterior groove. At the apex the three cuter layers do not enter in a whorl as in the left ventricle ; but at the base they are continuous with the three inner as on the other side of the heart. Many of the fibres of the external layer are attached to the ring of the pulmonary artery ; and the narrow slip from the right to the left ventricle, near the base in front, receives its fibres from the two outer strata. In this ventricle the fibres are arranged as if there had been originally one common cavity in the heart — the left ventricle, from which the right had been detached during the growth by a pushing inwards of a partition from the fore part. Septum ventriculorum. This partition between the two cavities has been divided anteriorly into right and left parts by the previous dissection ; and the layers of the ventricles may be traced into them. It is rather thicker than the wall of the left ventricle, and is formed by the fibres of both ventricles. About one-third belongs to the right, and two-thirds to the left ventricle. Where the two portions touch the fibres mingle, and altogether behind lie the “ common fibres” of the two ven- tricles. Endocardium . Lining the interior of the cavities of the heart is a thin membrane, which is named endocardium. It is continuous on the one hand with the lining of the veins, and on the other with that of the arteries. PULMONARY ARTERY. 325 'VYliere the membrane passes from an auricle to a ventricle, or from a ven- tricle to an artery, it forms duplicatures or valves, in which fibrous tissue is inclosed ; and in the ventricles it covers the tendinous cords of the valves, and the projecting muscular bundles. The thickness of tlie membrane is greater in the auricles than in the ventricles, and in the left than in the right half of the heart. In its struc- ture it resembles a serous membrane. Great Vessels of the Heart. The arteries which take origin from the heart are the aorta and the pulmonary. The large veins entering the heart, besides the coronary, are the superior and inferior cava, and the pulmonary. The PULMONARY ARTERY is a short thick trunk, which conveys the dark or impure blood from the right side of the heart to the lungs. From its commencement in the right ventricle the vessel is directed upwards on the left of the aorta ; and at a distance of an inch and a half or two inches, it divides into two branches of nearly equal size fo-r the lungs. The trunk of the pulmonary artery is contained in the pericardium ; and beneath it is the beginning of the aorta. On each side are the coronary artery and the auricular appendix. Fig. 104. The Formation of the Septum Ventriculorum by the Fibres of both Ventricles IS REPRESENTED IN THIS CUT. Near the bifurcation of the artery is a ligamentous cord about as large as a crow-quill, the remnant of the arterial duct, which passes from the left branch of the vessel to the arch of the aorta, and is named ligarnentiim ductus arteriosi. The right branch is longer than the left. In its course to the lung it lies beneath the aorta and the vena cava superior, and rests on the bron- chus or piece of the air tube : and as it passes outwards it lies above the level of the right auricle of the heart. At the lung the artery divides, into three primary branches, one for each lobe. The left branch is rather smaller than the right ; it is directed in front of the descending aorta and the left bronchus to the fissure of the root of the lung, where it ends in two branches for the two pulmonic lobes. 326 DISSECTION OF THE THORAX. As the riglit and left branches of the pulmonary artery pass outwards, they cross the air-tubes resulting from the division of the trachea, and inclose with them a lozenge-shaped space which contains some bronchial glands. Ductus arteriosus. The ligamentous structure was the continuation in the foetus of the trunk of the pulmonary artery, and was larger than either branch to the lung. At that period the vessel receives the name arterial canal or duct (ductus arteriosus, Botalli), and opens into the aorta rather beyond the origin of the last great vessel of the head and neck from the arch. As the lungs do not give passage to the circulating fluid before birth, the impure blood in the pulmonary artery passes through the arterial duct into the aorta below the attachment of the vessels of the head and neck, in order that it may be transmitted to the placenta to be purified. But after birth, when the function of the lungs is established, the current of blood is directed along the branches of the pulmonary artery instead of through the arterial duct ; and this tube becoming gradually smaller, is obliterated before the eighth or tenth day, and forms finally the ligament of the arterial duct. The AORTA is the great systemic vessel which conveys the blood from the heart to the different parts of the body. It arches backwards at first to reach the spinal column, and is continued on the spine through the chest and abdomen. In the thorax the vessel is divided into two parts — arch of the aorta, and the descending or thoracic aorta. Arch of the aorta (fig. 105). The aorta has its origin in the left ventri- cle, and curving backwards over the windpipe and the gullet, forms an Fig. 105. a. Aortic arch. h. Innominate artery. c. Left common carotid. d. Lett subclavian. c. Ligamentum ductus arteriosi. /. Vena cava superior. g. Left innominate vein. li. Right innominate vein. X. Left upper intercostal vein. h. Vena azygos major. Z. Left subclavian vein. XI. Thoracic duct. 0. Coronary artery . arch which ceases on the left side of the spinal column, at the lower bor- der of the fifth dorsal vertebra. The arch has its convexity upwards and to the right, and its concavity to the root of the left lung ; and from it the large vessels for the sujiply of the upper part of the body take their origin. For the purjiose of reducing to order the numerous connections of this AORTIC ARCH AND BRANCHES. 327 portion of the aorta, it is divided into three parts — ascending, transverse, and descending. Thcj^r^^ or ascending part is about two inches in length, or slightly more, and is directed upwards behind, and close to the sternum : it reaches as high as the upper border of tlie cartilage of tlie second rib on the right side, and is contained nearly altogether in tlie pericardium. At first the j)ulmonary artery is superficial to it ; but, as the vessels take different directions, the aorta is soon uncovered, and remains so to its termination. Behind it are the right branches of the pulmonary vessels. On the right side is the descending cava; and on the left, the pulmonary artery. Near the heart the vessel bulges opposite the semilunar valves (fig. 105). There is sometimes another dilatation along the right side, which is named the great sinus of the aorta. The second or transverse portion recedes from the sternum and reaches from the second right costal cartilage to the left side of the body of the fourth dorsal vertebra (the lower border). It rests upon the trachea above the bifurcation, and is placed over the oesophagus and the thoracic duct. Lying in front of this part of the artery are the vagus, phrenic, and super- ficial cardiac nerves of the left side — the first nerve sending backwards its recurrrent branch beneath the vessel. Along the upper border is the left innominate vein (< 7 ), to which the left upper intercostal vein (f) is directed over the left part of the arch ; and to the lower border near the termina- tion, the remnant of the arterial duct (e) is attached. From this part arise the three great vessels of the head and upper limbs. The third or descendmg part of the arch is very short, extending from the lower edge of the fourth to that of the fifth dorsal vertebra.* It lies against the fifth vertebra, and the fibro-cartilage between this and the fourth, and is covered by the pleura of the left side of the chest. In the concavity of the arch of the aoi-ta are contained the root of the left lung, the branching of the pulmonary artery with its arterial duct, and the left recurrent nerve. Deeper than those parts, the oesophagus and the thoracic duct, with some lymphatic glands, may be recognized. The branches of the arch of the aorta are five in number; two come from the ascending, and three from the transverse part. The first two are the coronary arteries of the heart ( 0 ), which have been already no- ticed (p. 313). The other three are much larger in size, and supply the neck, the head, and the upper limbs. First on the right is the large trunk of the innominate artery {h) ; close to it is the left carotid (c) ; and last of all comes the left subclavian (^d). The INNOMINATE ARTERY (5) (brachio-cephalic), the first and largest of the three branches, measures from one inch and a half to two inches in length. Ascending to the right beneath the sternum, it divides opposite the sterno-clavicular articulation into the right common carotid and the subclavian artery. The artery is crossed by the left innominate vein (^), and li^s behind the upper piece of the sternum, and the origin of the hyoid and thyroid muscles. At first it rests on the trachea, but as it ascends it is placed on ^ It is usually said that the second part of the aortic arch ends opposite the left side of the body of the second dorsal vertebra, and the third part, opposite the lower edge of the third vertebra. After examination, I have adopted the state- ment of Mr. Wood respecting the position of the aortic arch to the dorsal vertebrae. (Journal of Anatomy and Physiology for 1868.) 328 DISSECTION OF THE THORAX. the right side of the air tube. On its right is the innominate vein of the same side {h). Usually no lateral branch arises from the artery. Left Common Carotid Artery (c). The common carotid artery of the left side of the neck is longer than the right by the distance between the arch and the top of the sternum. In tlie thorax the artery ascends ‘obliquely to the left sterno-clavicular articulation, but not close to the first piece of the sternum and the origin of the depressor muscles of the hyoid bone and larynx. In this course it passes beneath the left innominate vein (^), and the remains of the thymus gland. At first it lies on the trachea, but it crosses afterwards to the left of that tube, so as to be placed over the oesophagus and the thoracic duct. To its outer side is the left vagus, with one or more cardiac branches of the sympathetic nerve. In the neck the connections of the vessels of opposite sides are not the same (p. 120). The LEFT SUBCLAVIAN ARTERY (c?) ascends to the neck through the upper aperture of the thorax. Beyond the first rib the vessels of opposite sides are alike (p. 118). Tlie trunk is directed almost vertically from the arch of* the aorta to tlie inner margin of the first rib. In the thorax the vessel lies deeply, resting at first on the oesophagus, and afterwards on the vertebral 'column and the longus colli muscle. It is invested by the left pleural bag in all its extent. On its inner side is the tracliea, and near the upper opening of the thorax the oesophagus with the thoracic duct is inside it. Some- what anterior to the lev^el of the artery, though running in tlie same direc- tion, are some of the cardiac nerves. Veins of the Heart (fig. 105). In addition to the cardiac veins (p. 314) there are the superior and inferior cava, and the pulmonary veins : the former are the great systemic vessels which return impure blood to the riglit auricle ; and the latter convey pure blood from the lungs into the left auricle. ' Tlie SUPERIOR or descending cava ( /) results from the union of the right and left innominate veins, and brings to the heart the blood of the head and neck, upper limbs, and thorax. Its origin is placed on the riglit side of the sternum, opposite the interval between the cartilages of the first two ribs. From that spot the large vein descends to the pericardium, perforates the fibrous layer of that bag about one inch and a half above the heart, and ends in the right auricle. Oir its outer surface the vein is covered by the pleura, and the phrenic nerve is in contact with it. To the inner side is the ascending part of the arch of the aorta. Behind the vein is the root of the right lung. ' When the cava is about to perforate the pericardium it is joined by the large azygos vein of the thorax (Z^) ; and higher up it receives small veins from the pericardium, and the parts in the mediastinal space. The innominate veins are united inferiorly in the trunk of the descend- ing cava. They are two in number, right and deft; and each is formed near the inner end of the clavicle, hy the union of the subclavian and in- ternal jugular veins. The trunks differ in length and direction, and in their connections Avith the surrounding parts. The right vein (/») is about one inch and a half long, and descends ver- tically, on the right side of the innominate artery, to its junction Avith the vein of the ojiposite side. Ou the outer surface the pleura covers it, and along it the phrenic nerve is placed. CAVA AND INNOMINATE VEINS. 329 ' The left vein (( 7 ) is twice ns long as the right, and is directed obliquely downwards above the level of the arch of the aorta. It crosses behind the sternum, and the remains of the thymus gland; and it lies on the three large branches of the aortic arch, as well as on the several nerves descend- ing over the arch. The branches of the veins are nearly alike on the two sides. Pkach re- ceives the internal mammary, the inferior thyroid, and the superior inter- costal of its own side ; and the left vein is joined in addition by some small thymic and pericardiac veins. Sometimes the innominate veins are not united in the vena cava, but descend separately to the heart, where each has a distinct opening in tlie right auricle. When such a condition exists, the right vein takes the course of the upper cava in front of the root of the right lung ; but tlu^ lelt vein descends in front of the root of the left lung, and turning to the back of the heart, receives the cardiac veins, before it opens into the right auricle. A cross branch connects the two above the heart. ^ This occasional condition in the adult is a regular one in a very early period of the growth of the foetus ; and two vessels are also persistent in some mammalia. Chan(je of the two veins into one. The changes taking place in the veins during the growth of the foetus, to produce the arrangement common in the adult, con- cern the trunk on the left side. The following is an outline of them. First the cross branch between the two trunks enlarges, and forms the future left innomi- nate vein. Next the left trunk below the cross branch disapj^ears at its middle, and undergoes transformations at each end : — At the upper end it becomes con- verted into the sujjerior intercostal vein. At the lower part it remains pervious for a short distance as the coronary sinus ; and even the small oblique vein open- ing into the end of that sinus in the adult (p. 314), is a remnant of the trunk of the vein that lay beneath the heart. In the adult there is a vestige of the occluded vessel in the form of a fold of the serous membrane of the pericardium in front of the root of the left lung ; this Mr. Marshall names the vestigial fold of the pericardium (p. 311 ). 2 The INFERIOR or ascending cava enters the right auricle as soon as it has pierced the diaphragm. No branches join the vein in the tliorax. Tlie anatomy of this vein will be given with the vessels of the abdomen. The PULMONARY VEINS are two on each side. They issue from the fissure of the root of the lung, and end in tlie left auricle : their position to the other vessels of the root has been noticed at p. 310. The right veins are longer than the left, and lie beneath the aorta and the right auricle of the heart. The superior receives its roots from the upper and middle pulmonic lobes, and the inferior vein is formed by branches of the lower lobe. The left veins cross in front of the descending aorta ; and one s[)rings from each lobe of the lung. NERVES OF THE THORAX. The pneumogastric and the sympathetic nerves supply the viscera of the thorax. Through the cavity courses the phrenic nerve to the diaphragm. ' An example of two large vessels, “ double vena cava,” opening into the right auricle in the adult, is contained in the Museum of 'University College. 2 See a paper by Mr. Marshall on the development of the veins of the nock (Philosoph. Transac., 1850). 330 DISSECTION OF THE THORAX. Dissection. The phrenic nerve is sufficiently denuded for its examina- tion ; but the student should trace the vagus nerves through the thorax. Tlie vagus is to be followed, on botli sides, behind the root of the lung, .and its large plexus in that position is to be dissected out: a few filaments of the gangliated cord of the sympathetic coming forwards over the spinal column to the plexus, must be looked for. In front of the root on the left side, tlie nerv^e supplies a few pulmonary filaments. Beyond the root the vagus is to be pursued along the (Bsophagus by raising the lung and re- moving the pleura. The piiKp:Nic nerve is a branch of the cervical plexus (p. 80). In its course through the tliorax it lies along the side of the pericardium, and at a little distance in front of the root of the lung, with a small companion artery. When near the diaphragm it is divided into brandies ; these per- forate the muscle, and are distributed on the under surface. The nerves of opposite sides difier in length, and in their connections above the root of the lung. Tlie riyht nerve is deeper at first, and is also shorter and straighter than the left. In entering the chest it crosses behind tlie subclavian vein, but in front of the internal mammary artery ; and it lies afterwards along the riglit side of the innominate vein and superior cava till it reaches the root of the lung. The left nerve crosses the subclavian artery, but has the same position as the right to the mammary vessels when entering the cavity. In the thorax it is directed in front of the arch of the aorta to the root of the lung, and makes a curve lower down around the projecting heart. Before reaching the aorta the nerve is placed external to the left common carotid artery; and crosses the left vagus from without inwards, so as to be inter- nal to that nerve on the arch. Branches. Some small filaments are said to be furnished from the nerve to the pleura and pericardium. Internal rnammary artery. A small part of this artery, which lies be- neath the first rib, and winds round the phrenic nerve and the innominate vein to reach the side of the sternum, is now to be learnt. It gives the following offset : — The superior phrenic branch (comes nervi phrenici) is a very slender artery, which accompanies the phrenic nerve to the diapliragm, and is dis- tributed to that muscle, anastomosing therein with other branches of the aorta, and with the musculo-phrenic branch of the internal mammary (p. 239). The PNEUMOGASTRic NERVE (p. 181) passes through the thorax to the abdomen. In the lower part of the thorax the nerves of op})Osite sides have a similar position, for they pass behind the root of the lung, each on its own side, and along the oesophagus to tlie stomach. But above the root of the lung, the right and left nerves differ mucli. Each supplies branches to the viscera, viz., to the heart, the windpipe and lungs, and the gullet. The right vagus is posterior to the left in position. It enters the tho- rax between the subclavian artery and the innominate vein, and is directed obliquely backwards, by the side of the trachea, and between tliis tube and the oesoiihagus, to tlie posterior aspect of the root of the lung, where it gives rise to the jiosterior pulmonary plexus. From tlie plexus two large offsets are continued to the back of the gullet, and unite below into one trunk, which reaches the posterior surface of the stomach. The left nerve appears in the thorax on the outer side of the left com- VAGUS NERVE AND BRANCHES. 331 mon carotid artery, and courses over the arch of the aorta, and beneath the root of the lun^, forming there a larger plexus than on the riglit side. From the pulmonic plexus one or two branches pass to the front of the cesophagus, and join with offsets of the right nerve in a plexus ; but its piec(*s are collected finally into one trunk, which is continued on the front of the gullet to the anterior part of the stomach. The branches of the pneumo-gastric nerve in the thorax are the follow- ing a. Tlie recurrent or inferior laryngeal nerve, arising on the right side on a level with the subclavian artery, and on the left, at the lower border of the arch of the aorta, bends backwards to the trachea, along which it ascends to the larynx. On each side this branch is freely connected with the cervical cardiac branches of the sympathetic nerve, especially on the left side beneath the arch of the aorta. h. Cardiac branches {iXiomcic). Besides the cardiac branches furnished by the vagus in the neck, other offsets pass in front of the trachea to the cardiac plexus. On the right side they come from the trunk of the vagus and the recurrent branch, but they are supplied by the recurrent nerve alone on the left side. The termination of the lower cervical cardiac branch of each vagus nerve (p. 114) maybe now seen. The branch of the right lies by the side of the innominate artery, and joins a cardiac nerve of the sympathetic of the same side ; and the branch of the left vagus crosses over the arch of the aorta, to end in the superficial cardiac plexus. c. Pulmonary branches. There are two sets of nerves for the lung, one on the anterior and the other on the posterior aspect of the root. The anterior branches are two or three in number, and small in size, and communicate with filaments of the sympathetic on the pulmonary artery: these nerves are b^‘st seen on the left side. The posterior branches are the largest and much the most numerous. Forming a plexiform arrangement (posterior pulmonary plexus) behind the root of the lung by the flattening and splitting of the trunk of the nerve, they are joined by filaments from the third and fourth ganglia of the knotted cord of the sympathetic, and are conveyed into the lung on the divisions of the air tube. d. (Esophageal branches are furnished to the gullet, but in greatest abundance in the lower half. Below the root of the lung the branches of the pneumo-gastric nerves surround the cesophagus with a network (j>lexus guloe). Sympathetic Nerve. In the thorax the sympathetic nerve consists of a knotted cord along each side of the spinal column, which communi- cates with the spinal nerves : and of a large pre vertebral or cardiac plexus, which distributes branches to the heart and the lungs. The gangliated cord will be seen in a future stage of the dissection after the heart and the lungs have been removed. The CARDIAC PLEXUS lies at the base of the heart around the great bloodvessels. A part of this network, the superficial cardiac plexus, has been already described (p. 314). The remaining part, or the deep cardiac plexus, is placed beneath the arch of the aorta. Dissections. The cardiac plexus has been injured by the previous ex- amination of the heart, so that it should be dissected in a body in which the heart and the large vessels are entire. Dissection. The arch of the aorta is to be cut across near the heart 332 DISSECTION OF THE THORAX. and close above the pulmonary artery, and is to be drawn over to the left side : next the upper cava is to be divided above the entrance of the vena azygos, and its lower part is to be thrown down. By the removal of some fibrous and fatty tissues and lymphatic glands, the right part of the plexus,’ in which the nerves of the right side are united, will be seen in front of the trachea, above the right branch of the pulmonary artery. The offsets to the heart should be followed downwards on the trunk of the pulmonary artery ; and those to the lung should be traced along the right branch of that vessel. To lay bare the part of the plexus into which the nerves of the left side of the body enter, the arch is to be cut through a second time, to the right of and close to the junction of the ligamentum arteriosum with it ; and the transverse part of the arch is to be turned upwards with the great vessels attached. The lymphatic glands and the areolar and fatty tissue being cleared away from the plexus as on the opposite side, the offsets to the posterior coronary plexus of tlie heart are to be cleaned. Deep cardiac plexus. This large centre is situate between the trachea and the arch of the aorta, above the branches of the pulmonary artery. In it are united the cardiac nerves of the symipathetic of both sides of the neck, except the highest nerve of the left side : and the cardiac branches of the vagus in the neck and chest, with the exception of the lowest cervical branch of the left side. From it nerves are furnished to the heart and lungs. The several nerves entering the plexus are not intermingled in a plexi- form mass in front of the trachea ; but those of the right side unite together on the right of the air tube, and tliose of the left have a like junction on their side. right part of the plexus placed above the right branch of the' pulmonary artery, and receives the nerves of the riglit side, viz., the car- diac nerves of the sym})athetic in the neck ; the cardiac brandies of the trunk of the vagus, in both the neck and chest ; and the cardiac offsets of the recurrent branch. The branches of tliis half of the plexus are distributed mostly to the right side of the heart, and pass downwards before and behind the right branch of the pulmonary artery : those in front running on the trunk of the pulmonary artery to end in the anterior coronary plexus (p. 315) ; and the nerves behind supjily the right auricle of the heart. Ofi*sets are sent laterally on the branch of the artoiy to the root of the lung. The left half of the plexus lies close to the ligamentum arteriosum, and rather on the left of the trachea. In it are collected the cardiac nerves of the sympathetic ganglia of the left side of the neck, except the highest ; and numerous and large branches of the left recurrent nerve of the vagus. Nerves descend from it to the Iieart around tlie left branch and trunk of the })ulmonary artery, and after supplying branches to the left auricle, ter- minate in the jiosterior coronary plexus (p. 315). A considerable offset is directed forwards by the side of the ligamentum ductus arteriosi to the su[)erHcial cardijic {)lexus ; and some nerves reacli the left anterior pulmo- naiy plexus by })assing along the branch of the pulmonary artery. Termination of the cardiac branches of the sympathetic nerve of the neck (j). 117). On the right side tiiere are usually only two cardiac nerves entering the thorax, for the highest nerve is blended commonly with one of the others. The middle and inferior nerves pass beneath the subclavian artery to the TRACHEA AND BRONCHI. 383 right half of the deep plexus : they communicate with the branches of the recurrent laryngeal nerve of the vagus. On the left side the highest cardiac nerve lies over the arch of the aorta, and ends in the superficial cardiac plexus ; it may give a branch beneath the arch to the deep plexus. Only one other nerve, the lower cardiac, may be seen entering the left side of the deep plexus, as the mid- dle one throws itself oftentimes into it. THE TRACHEA AND THE LUNG. Dissection. To see the pieces of the air tube in the root of the lung, it will be necessary to remove the pu’monary artery with its branches, and the pulmonary veins. And when the transverse part of the arch of the aorta, which has been already cut through, is turned to one side, the dis- sector will be able to clear away the bronchial glands, the nerves, and the fibrous tissue from the part of the trachea in the thorax, and from the branches into which it bifurcates. The TRACHEA, or the air tube, reaches from the larynx to the lungs, and lies on the front of the spinal column. The tube begins opposite the fifth cervical vertebra ; and it ends commonly at the I’ourth dorsal vertebra by dividing into two pieces (bronchi), one for each lung. Its point of splitting may be a vertebra lower. Its connections in the neck are described in p. 121, and its structure in p. 162. The j;art in the thorax remains to be studied. In the thorax the trachea is situate with the great vessels in the space between the pleural bags. Here it is covered by the arch of the aorta, by the innominate and left carotid arteries, and by the cardiac plexus of nerves. Behind the air tube is the msophagus, which is slightly inclined to the left near the arch of the aorta. On the right side are the vagus, and the innominate artery, for a short distance, after this has passed over the trachea ; and on the left side lie the left subclavian artery, and the vagus with its recurrent branch. The bronchi, or the branches of the air tube, are contained in the roots of the lungs, and are surrounded by vessels, glands, and nerves. Near the lung each is divided into as many primary pieces as there are lobes. In their structure and form the bronchi resemble the windpipe, for they are round and cartilaginous in front, but flat and muscular and membranous behind. Their position behind the other pulmonary vessels has been de- scribed at p. 310 ; but the characters of each are now to be noticed. The right branch is about an inch in length, and is larger than the left ; it passes outwards, on a level with the fourth dorsal vertebra, beneath the arch of the aorta and the upper cava, and above the right pulmonary artery : the vena a/.ygos arches above it. The left branch, about two inches long, is directed obliquely downwards through the arch of the aorta, and joins the root of the left lung a vertebra lower than on the opposite side. The tube lies on the oesophagus and thoracic duct, and on the aorta ; it is at fii-st below the level of the corre- sponding pulmonary artery. Dissection. The lungs are to be removed now from the body by cutting through the vessels of the root. The remains of the heart and pericardium are to be taken away after- wards. For their remo\al the inferior cava is to be divided, and the peri- cardium to be detached from the surface of the diaphragm ; in removing 334 DISSECTION OF THE THORAX. the pericardium, the dissector should be careful not to injure the parts contained in the interpleural space in front of the spine. Physical Characters of the Lung. The surface of the lung is smooth and shining, and is invested by the pleura. Through the serous covering the mass of the lung may be seen to be divided by septa, into small irregularly-sized pieces or lobules. On looking closely at it, espe- cially at a thin margin, minute cells will be perceived in it. The tint of the lung varies with age. In infancy the color is a pale red; but in the adult the texture becomes grayish, and presents here and there dark gray spots or lines of pigment, whose shade deepens with in- creasing age, and becomes even black in old people. After death, the color of the posterior border may be bluish-black from the accumulation of blood. To the touch the lung is soft and yielding, and on a section the pulmo- nary substance appears porous and spongy ; but the lung which is deprived of air by pressure has a tough leathery feel. Slight pressure with the thumb and finger drives the air from the containing cells through the pul- monary structure, and produces the noise known as crepitation. If the lung contains serum, a frothy red fluid will run out when it is cut. The texture of the lung is very elastic ; this elasticity causing the organ to diminish greatly when the thorax is opened, and to expel air that may be blown into it. The specific gravity of the lung varies with the conditions of dilatation and collapse, or of infiltration witli fluid. When the pulmonary substance is free from fluid, and filled with air, it floats in water; but when it is quite deprived of air it is slightly heavier than water, and sinks in that fluid. The weight of the lung is influenced greatly by the quantity of other material contained in its texture; ordinarily it ranges from eighteen to twenty-one ounces, and the right lung is about two ounces heavier than the left. In the male the lungs are larger, and slightly heavier than in the female. Dissection. By tracing the large branches of the bronchi, and the bloodvessels and nerves into the lung, the mode of branching of the air tubes will be apparent; and by inflating a part of the lung, the cellular structure may be seen. But the arrangement of the small air cells about their tube, and the disposition of the different vessels, cannot be ascer- tained without fine injections and a microscope. Structure of the Lung. The spongy pulmonary tissue consists of minute recesses or cells, in which the smallest branches of the air tube terminate; and the mass of the lung is formed by the collection of those cells into small groups or lobules, and by the aggregation of the lobules into larger masses or lobes. Each lobule is distinct from its fellows, and is furnished with its air tube and nerves, and with its set of vessels con- cerned in the function and nutrition. The parts of the lung are united by a serous covering, prolonged con- tinuously over the surface; and by a subserous layer of areolar tissue which penetrates into the anterior, subdividing it into pieces. These several' parts are examined more in detail below. Serous and subserous coverings. The casing derived from the pleura is thin and transparent, and forms an entire capsule for tlie lung, except at the root where tlie vessels enter. The subserous areolar layer contains fibres of elastic tissue, and not only covers the surface, but extends in- STRUCTURE OF LUNG. 335 wards, establishing tlie division of the mass into lobules: where it sepa- rates the lobules it is named interlobular tissue, and is free from fat. Bronchial branches in the luruj. When a bronchus is followed into the pulmonary structure it is found to divide generally in a binary order, and to diminish in size at each subdivision, until one terminal offset ap- pertains to a lobule. In the lobule the tube has a diameter of to 3^^ of an inch. When this last degree of diminution is reached, the tube gives origin to the air cells. The larger broncliial branches have the same composition as the trachea, but they are round in the lung, instead of being semi-elliptical as in the trachea. The smallest branches want some of the elements found in the larger bronchi; and those from which the cells spring are irregular in shape, appearing to be spaces amongst the cells rather than tubes with continuous walls. Changes in the bronchi. The modifications of the component parts of the bronchi are the following: — The 'pieces of cartilage are broken up in the smaller bronchial tubes, and are scattered over the wall as irregular fragments. Becoming thinner and smaller as the subdivision of the air tube proceeds, they at last disappear, and are absent from the terminal branches. The fibrous and elastic tissues of the bronchial tubes are con- tinued to the air cells, but in the small cell-bearing branches, the bundles of elastic tissue are diffused, and, much diminished in strength, blend with the fibrous or areolar tissue to form the wall. The muscular fibres are diffused over the inner surface of the smaller bronchi, where they have an annular arrangement; they extend beyond the limit of the pieces of carti- lage, but they cease where the cells begin to be formed. The mucous membrane becomes thinner as it extends onwards in the bronchial pieces, and is finally continued to the cells, where it is transparent. Its epithe- lium is columnar and ciliated in the bronchial tubes, but is changed to squamous or laminar in the air cells. Lobules and lobes. A lobule is a cluster of air cells around a terminal branch of the air tube. Varying in size and shape, each lobule is invested by areolar tissue, and possesses its own offset of the air tube, as well as distinct branches of vessels and nerves. The lobes are produced by the aggregation of the lobules. The air cells are the little recesses or dilatations connected with the smallest branches of the air tube. They are polyhedral in form, except on the surface of the lung, and are distinct one from another, save through the channel of the air passage. The cells are clustered in groups around the terminal branches of the air tube, with which they communicate by large orifices. These small spaces are about of an inch across, but they are larger on the surface and at the edges than in the deeper parts of the lung. The cell wall is formed by areolar and elastic tissue, and is lined by a transparent mucous membrane possessing laminar epithelium. Beneath the mucous lining is a network of capillaries of the pulmonary vessels. Vessels of the Lung. Two sets of vessels are furnished to the lung, one being concerned in its function, the other in the nutrition. The ves- sels conveying blood to the lung to be aerated, and carrying that fluid away after it has been subjected to the respiratory process, are named pulmonary. The vessels connected with the nutrition of the texture are called bronchial. The pulmonary artery divides like the bronchus, which it accompanies 386 DISSECTION OF THE THORAX. to tlie lobule. At the lobule the arterial branch is minutely subdivided, and its ramifications enter the interlobular fissure to end in the cell Avail in the following way: — Over the bottom of the cell they form a very fine capillary network, but at the circumference they give rise to a circular vessel; and the circles of several cells communicate with each other. The 'pulmonary veins begin in the vascular network before mentioned. The twigs issuing from the several lobules are destitute of valves, and are united in larger tubes which course to the root of the lung. Although the small lobular branches of the arteries remain separate from one another, the corresponding veins anastomose together. The bronchial arteries enter the lung on the air tube, and supply deep branches to it and the contiguous glands, to the large bloodvessels, and to the interlobular areolar tissue of the lung. On the smallest air tubes minute branches anastomose with offsets of the pulmonary arteries. Superficial tortuous offsets of the artery ramify beneath the pleura, form- ing a capillary network. The bronchial vein begins by twigs corresponding with the superficial and deep branches of the artery. Leaving the lung at the root, the vein ends differently on opposite sides of the body (p. 337). , Nerves and lymphatics. The lung receives nerves from the vagus and the sympathetic ; and the offsets follow the branches of the air tube, but their ending is uncertain. Remak describes small ganglia on the sympa- thetic filaments. The lymphatics of the lung are both superficial and deep, and enter the bronchial glands at the root of the lung. PARTS ON THE SPINE AND THE SYMPATHETIC CORD. In front of the spinal column are the several parts lying in the inter- pleural space of the posterior half of the mediastinum, viz., the aorta, azygos veins, thoracic duct, oesophagus, and splanchnic nerves^ Dissection. The thoracic duct should be found first near the diaphragm by removing the pleural; there it is about as large as a crow quill, and rests against the right side of the aorta : this slender vessel may be in- jected with tallow. The areolar tissue and the pleura are to be cleared aAvay from the dif- ferent parts before mentioned ; and the azygos or intercostal .veins, one on the right and two on the left aorta, should be dissected. Next follow the thoracic duct upwards beneath the arch of the aorta, and along the oeso- phagus beneath the pleura, till it leaves the upper aperture of the thorax. After raising the pleura also from the inner surface of the chest, the' gaugliated cord of the sympathetic nerve will be seen lying over the heads of the ribs. Branches are to be followed outwards from the ganglia to the intercostal nerves ; and others inwards over the bodies of the vertebrae, — the lowest and largest of these forming the three trunks of the splanchnic nerves. The DESCENDING THORACIC AORTA is the part of the great systemic vessel above the diaphragm. Its extent is from the lower border of the fifth dorsal vertebra (the left side), where the arch ceases, to the front of the last dorsal vertebra. Contained in the interpleural space in front of the spine, the vessel is rather curved, lying at its iq)per part on the left, but below on the front of the spinal column. Beneath it are the vertebrae and the smaller azygos veins. In front of the vessel is the root of the left lung with the pericar- INTERCOSTAL ARTERIES. 337 dinm. On its left side it is eovered throughout by the pleura ; and on its right side are the oesophagus and the thoracic duct, though near the dia- phragm the gullet is placed over tlie aorta. The branches of the vessel are distributed to the surrounding parts, and are named from their destination bronchial, pericardial, oesopliageal, medi- astinal, and intercostal. a. Tlie bronchial arteries supply the structure of the lungs, and adhere to the posterior part of the bronchial tubes, on which they ramify (p. 336) ; they give some twigs to the bronchial glands and the oesophagus. For the left lung there are two arteries (su[)erior and inferior), which arise from the front of the aorta at a distance from each other. The artery of the right lung arises in common with one of the left bron- chial arteries (superior), or from the first intercostal artery of the right side. Bronchial veins. A vein issues from the root of each lung, and ends in the following manner : the right joins the larger azygos vein ; and the left ends in the superior intercostal vein of its own side. b. The pericardial branches are some irregular twigs, which are fur- nished to the posterior part of the cardiac bag. c. (Esophageal branches arise at different points of the aorta, and are four or five in number. Ramifying in the gullet, the vessels anastomose with one another; above, they communicate with branches of the inferior thyroid artery near the pharynx ; and below, with twigs of the coronary artery of the stomach. d. Small mediastinal branches (posterior) supply the areolar tissue and the glands in the interpleural space. e. The intercostal arteries are ten on each side ; nine are furnished to the same number of lower intercostal spaces, whilst the last lies below the twelfth rib : to the upper two spaces branches are supplied from the inter- costal artery of the subclavian trunk. These small vessels arise from the posterior part of the aorta, and run outwards on the bodies of the vertebne, beneath the cord of the sympathe- tic nerve, to the intercostal spaces, where each divides into an anterior and a posterior branch. In this course the upper arteries have a somewhat oblique direction ; and as the aorta lies on the left of the spine the right vessels are the longest : the right also pass beneath the cesophagus, the thoracic duct, and the azygos vein. Many twigs are supplied to the bodies of the vertebriE. In the spaces bounded by the true ribs, the anterior branch, the larger of the two, continues onwards between the muscular strata nearly to the anterior third of the intercostal space, where it ends in two pieces, which anastomose with the intercostal arteries of the internal mammary (p. 239). At first the artery lies in the middle of the intercostal space, beneath the pleura and a fascia from the internal intercostal muscle, and resting on the external intercostal layer ; but near the angle of the rib it ascends to the upper boundary. Accompanying the artery are the intercostal vein and nerve, the vein being commonly above, and the nerve below it ; but in the upper spaces the nerve is, at first, higher than the artery. Below the true ribs the vessels are contained partly in the thoracic and partly in the abdominal wall. Behind they have the same course and connections as the higher intercostals ; but in the wall of the abdomen they lie between the two deep muscles ; they will be noticed hereafter. Branches are furnished to the intercostal and abdominal muscles, and 22 838 DISSECTION OF THE THORAX. to the ribs. About the centre (from front to back) of the intercostal space a superficial twig arises, which accompanies the cutaneous nerve. The highest artery of the aortic set of intercostals anastomoses with the superior intercostal branch of the subclavian artery; and the lowest (below the true ribs) enters the abdominal wall, and anastomoses with the arteries of that part. The 'posterior branch turns backwards between a vertebra and an as- cending costo-transverse ligament, and is distributed in the Back. As it passes by the intervertebral foramen it furnishes a small spinal branch to the vertebrae and the spinal cord. (See Vessels of the Spinal Cord.) The intercostal vein resembles closely the artery in its course and branching. Near t^he head of the rib it receives a contributing dorsal branch, and then joins an azygos vein. The superior intercostal artery of the subclavian trunk (p. 78) descends over the neck of the first rib, external to the ganglion of the sympathetic, and supplies a branch to the first intercostal space : continuing to the second space, which it supplies in like manner, it anastomoses with the upper aortic branch. Its intercostal offsets divide into an anterior and a posterior branch, like the arteries from the aorta. The vein accompanying the artery opens into the innominate vein of the same side. The left superior intercostal vein (fig. 105, f), formed by branches from the two or three highest spaces, is joined by the left bron- chial vein, and ends in the left innominate vein, after crossing the arch of the aorta. The INTERCOSTAL or AZYGOS VEINS are two in number on the left, and one on the right side, and receive branches corresponding with the offsets furnished by the thoracic aorta. The right or larger azygos (fig. 106, begins in the lumbar veins on the right side of the spine, and its origin is discribed with the vessels of the abdomen. It enters the thorax through the aortic opening of the diaphragm, and ascends on the right side of the thoracic duct, over the intercostal arteries and the bodies of the vertebra?. Opposite the fourth intercostal space the vein arches forwards above the root of the right lung, and enters the superior cava as this vessel pierces the pericardium. Its valves are very incomplete, so that blood may flow either way ; and the intraspinal and intercostal veins may be injected through it. Branches. In this vein are collected the intercostals of the right side below the upper two spaces ; some of the intercostals of the left side of the thorax, through the left azygos veins ; and some small oesophageal, me- diastinal, and vertebral veins, with the right bronchial vein. By means of the right vein the inferior communicates with the superior cava, so that the blood may reach the heart from the lower part of the body, or the opposite, if one of the cava? should be obstructed. The left lower azygos vein (fig. 106, *) begins in the abdomen in the lumbar veins of the left side of tlie vertebral column. Entering the thorax along with the aorta, or through the crus of the diaphragm, the vein as- cends on the left of tlie aorta as higli as the seventh or eighth dorsal ver- tebra, where it crosses beneath that vessel and the thoracic duct to end in the right azygos. It receives the four or five lower intercostal veins of the left side, and some cesophageal and mediastinal brandies. Tlie left upper azygos vein (fig. 106, ^) is formed by offsets from the space between the superior intercostal and the preceding. Receiving three (ESOPHAGUS. 839 or four branches, the trunk either joins the lower azygos of its own side, or crosses the spine to open into the right vein. Tlie CESOPHAGUS or gullet is a hollow muscular tube, which extends from the pharynx to the stomach : the cervical portion has been described at p. 121, and the thoracic part is now to he examined. Appearing in the thorax rather to the left of the middle line, the gullet is directed beneath the arch of the aorta, and reaches the middle of the spine about the fifth dorsal vertebra. From that spot it is continued through the interpleural space on the right of the aorta, till near the diaphragm, where it takes a position over the aorta, to gain the oesopha- geal opening of that muscle. As far as the aortic arch the oesophagus lies beneath the trachea, though it is inclined somewhat to the left of the air tube ; beyond the arch it is crossed by the left bronchus, and is concealed by the pericardium as far as the diaphragm. At the upper part of the thorax the gullet rests on the longus colli muscle and the vertebra3 ; but below the arch of the aorta it is separated from the spine by the intercostal vessels, and tlie aorta. Laterally it touches the left pleura above the arch, and both pleurae be- low, but more of the right than the left. Below the bronchus the pneu- mogastric nerves surround tlie oesophagus with their branches ; and above the same spot the thoracic duct is in contact with it on the left. Structure. If* a piece of the gullet be removed and distended with tow, it will be easy to show a muscular, fibrous, and mueous coat, one^ within another. The muscular coat is thick and strong, and possesses two layers of fibres, of which the external is longitudinal, and the internal circular in direc- tion, like the muscular tunic of tlie other parts of the alimentary tube. In the upper third of the oesophagus the fibres are red, but below that spot the color becomes paler. The external layer is formed of parallel longitudinal fibres, which form an entire covering, and end below on the stomach. The fibres begin opposite the cricoid cartilage (p. 131) ; and at intervals varying from half an inch to an inch and a half, they are connected with tendinous points (^V iV inch long) like the fibres of the rectus abdominis muscle. The internal layer of circular fibres is continuous above with the fibres of the pharynx ; they are more oblique at the middle than at either end of the oesophagus. The fibrous layer is situate between the muscular and mucous coats, and attaches the one to the other loosely. The mucous coat will be seen on cutting open the tube : it is reddish in color above but pale below, and is very loosely connected with the muscu- lar coat, so that it is thrown into longitudinal folds when the oesophagus is contracted. Lining the interior is a thick layer of scaly epithelium ; and the surface is studded with minute papillae. Some compound glands (oesophageal) are scattered along the tube ; at the lower part of the gullet they are most numerous, and form a ring (cardiac) close to the stomach. Lymphatics of the Thorax. In the thorax are lymphatic vessels of the M^all and the viscera, which enter collections of glands, and end in one or other of the two lymphatic ducts. Besides these, the large thoracic duct traverses the thorax in its course from the abdomen to tlie neck. Lymphatic glands. Along the course of the internal mammary artery lies a chain of sternal or mediastinal glands, which receive lymphatics 340 DISSECTION OF THE THORAX. from the front of the chest, the thymus body, the pericardium, and the upper surfaces of the diaphragm and liver. On each side of the spine, near the heads of the ribs, as well as between the intercostal muscles, is placed a group of intercostal glands for the re- ception of the lymphatics of the posterior wall of Fig. 106. the thorax. Numerous bronchial glands are situate at the division and along the side of the trachea, through which the lymphatics of tlie lung pass ; and be- neath the arch of the aorta are a few cardiac glands, to which the lymphatics of the heart are directed. Along the side of the aorta and oesophagus is a chain oesophageal glands, which are joined by the lymphatics of the oesophagus, and communi- cate with those of the lungs. The thoracic duct (fig. 106,^) is the main channel by which the lymphatic and lacteal fluid of the lower half of the body, and of the left side of the upper half of the body, is conveyed into the blood. The duct begins in the abdomen in an enlargement (chyli receptaculum), and ends in the left subclavian vein of the neck. It is about eighteen inches in length, and is contained in the thorax, except at its origin and termination. It has the undermentioned connections : — Entering the cavity on the right of the aorta and through the same opening, the duct ascends on the right side of that vessel, as high as the arch. Opposite the fifth dorsal vertebra it passes beneath the aortic arch, and is applied to the left side of the oesophagus, on which it is conducted to the neck under the left subclavian artery. At the lower part of the neck the duct arches out- wards, as before described (p. 119), to open into the left subclavian vein. In this course the tube is oftentimes divided in two, which unite again ; or its divisions may even form a plexus. Near its termination it is frequently branched. It is provided with valves at intervals, like a vein ; and these are in greatest number at the upper part. Branches. In the thorax the duct receives the lymphatics of the left half of the cavity, viz., from the sternal and intercostal glands ; also the lymphatics of the left lung, the left side of the heart, and the trachea and oesophagus. The right lymphatic duct (fig. 27) receives large branches from the viscera of the thorax. It is a short trunk, about half an inch in length, and opens into the angle of union of the subclavian and jugular veins of the same side (p. 79) : its opening is guarded by valves. Branches. Into this trunk the lymphatics of the right upper limb, and View of the Thoracic Duct, and the Inter- costal Veins. 1. Thoracic duct. 2. Ending of the duct in the left subclavian vein. 3. Large or right azygos vein. 4. Left lower azygos or in- tercostal vein. 5. Left upper azygos or inter- costal. 6. Vena cava superior. 7. Left internal j ugular vein, cut through,. SYMPATHETIC NERVE AND OFFSETS. 341 right side of the head and neck pour their contents. In addition, the lymphatics of the right side of the chest, right lung and right half of the heart, and some from the right lobe of the liver, after passing through their respective glands, unite into a few large trunks, which ascend beneath the innominate vein to reach the duct in the neck. Structure of the ducts. The wall of the tube resembles that of the bloodvessels in structure (p. 119). Cord of the Sympathetic Nerve. The thoracic part of the gan- gliated cord of the sympathetic nerve is covered by the pleura, and is placed over the heads of tlie ribs, and the intercostal vessels. The ganglia on it are usually twelve, one being opposite each dorsal nerve, but this number varies much. The upper ganglion is the largest ; and the last two are rather anterior to the line of the others, being situate on the side of the bodies of the corresponding vertebrae. Each ganglion furnishes external branches to communicate with the spinal nerves, and internal for the supply of the viscera. External or connecting branches (fig. 107). Two offsets pass outwards from each ganglion to join a spinal nerve (intercostal). In the branches Fig. 107. a. Posterior root of a spinal nerve, with a ganglion, c. h. Anterior root. d. Posterior primary branch. e. Anterior primary branch of the spinal nerve, /. Knotted cord of the sympathetic. g. Ganglia on the cord. U. White offset from the spinal to the sympa- thetic nerve. i. Gray offset from the sympathetic to the spinal nerve. Scheme to Illustrate the connection between the Spinal and Sympathetic Nerves. (Todd and Bowman.) of communication both spinal and sympathetic nerve fibrils are combined : but one {Ji) consists almost entirely of spinal, and the other {%) nearly al- together of sympathetic nerve fibres. The internal or visceral branches differ in size and distribution, accord- ing as they are derived from the upper or lower six ganglia. The offsets of the upper six are very small, and are distributed to the aorta, and the vertebrie with the ligaments. Mr. Swan describes a plexus in front of the spine, from the union of the branches of opposite sides. 842 DISSECTION OF THE THORAX. From the third and fourth ganglia offsets are sent to the posterior pulmo- nary plexus. The branches of the lower six are larger and much whiter than the others, and are united to form visceral or splanchnic nerves of the abdo- men : these are three in number (large, small, and smallest), and pierce the diaphragm to end in the solar and renal plexuses. The great splanchnic nerve is a large white cord, which receives roots apparently from only four or five ganglia (sixth to the tenth), but its fibres may be traced upwards on the knotted cord as high as the third ganglion. Descending on the bodies of the vertebrae, it pierces the fibres of the crus of the diaphragm, and ends in the semilunar ganglion of the abdomen. At the lower part of the thorax the nerve may present a ganglion. The small splanchnic nerve begins in the tenth and eleventh ganglia, or in the intervening cord. It is transmitted interiorly through the crus of the diaphragm, and enters the part of the solar plexus by the side of the coeliac artery. The smallest splanchnic nerve springs from the last ganglion, and ac- companies the other nerves through the diaphragm ; in the abdomen it ends in the renal plexus. This nerve may be absent, and its place may be taken by an offset of the preceding. PARIETES OF THE THORAX. Between the ribs are lodged the two layers of intercostal muscles, with the intervening nerves and arteries ; and inside them lies a thin fleshy layer behind, — the infracostals. At the base of the thorax is the diaphragm. The INFRACOSTAL MUSCLES are small slips of fleshy fibres, which are situate on the inner surface of the ribs, where the internal intercostals cease. Apparently part of the inner intercostals, they arise from the inner surface of one rib, and are attached to the like surface of the rib next succeeding. They are uncertain in number, but there may be ten : they are smaller above than below, and the upper and lower may pass over more than one space. Action. These thin muscles approach the ribs to one another, dimin- ishing the size of the thoracic cavity, and act thus as expiratory muscles. Intercostal Muscles. The anterior part of the muscles has been described (p. 237) ; and the posterior part may be now examined from the inner side. The inner muscle begins at the sternum, and reaches backwards to the angle of the ribs in the middle spaces, but, higher and lower, the muscu- lar fibres approach nearer the s[)ine. Where the fibres cease, a thin fascia is continued backwards over the outer muscle. The inner surface is lined by the pleura, and the opposite surface is in contact with the intercostal nerve and vessels. External muscle. When the fascia and the infracostal muscles have been removed, the external intercostal will be seen between the posterior border of the internal muscle and the spine. Its fibres cross those of the inner intercostal layer. Whilst this muscle extends backwards to the tubercle of the rib, it does not reach further forwards than the rib carti- lages, as before said. Action. The use of the intercostal muscles in respiration is given in p. 238. INTERCOSTAL NERVES. 343 Dissection. In a few spaces the internal intercostal muscle may be cut through, and the intercostal nerve and artery traced outwards. The INTERCOSTAL NERVES are the anterior primary branches of the dorsal nerves. Twelve in number, they occupy the intercostal spaces, witliout communicating in a plexus ; and the last is placed below the twelfth rib. The upper six lie between the ribs, and are confined to the wall of the thorax ; whilst the lower six are prolonged into the abdominal wall, where the ribs cease in front. Upper six. At first the nerves lie between the pleura and subjacent fascia and the external intercostal muscle, with an artery and vein ; but they enter soon between the intercostals and extend forwards to the middle line of the body. Near the head of the rib each is joined by filaments from the sympathetic. In its course each supplies branches to the inter- costal muscles and the ribs, and cutaneous offsets to the surface ; these are described in the dissections of the upper limb and wall of the abdomen. There are some deviations in the first and second nerves from the ar- rangement above specified. The, first nerve ascends in front of the neck of the highest rib, and ends in the brachial plexus. Before it leaves the chest it sup{)lies to the first intercostal space a branch, which furnishes muscular offsets, and becomes cutaneous by the side of the sternum. There is not any lateral cutaneous offset from this branch, except in those cases in which the second nerve is not as large as usual. The second nerve may extend a considerable way on the wall of the chest before entering between the intercostal muscles, and may ascend even to the first space. It is remarkable in having a very large lateral cutaneous branch (p. 225). In front it ends like the others. Upper surface of the diaphragm. The centre of the muscle is tendinous, and the sides are fleshy. In contact with the upper surface are the lungs laterally, and the pericardium in the middle : the phrenic vessels and nerves pierce this surface, external to the pericardium. In the diaphragm are the following apertures : one for the oesophagus and the pneumogastric nerves, a second for the vena cava, a third for the aorta with the thoracic duct and the vena azygos, and a fourth on each side for the splanchnic nerves. Beneath it the sympathetic passes into the abdomen. The arch of the diaphragm towards the thorax has been before referred to (p. 306). Directions. The dissector of the thorax now waits wdiile the examina- tion of the Back is made. Afterwards he is to learn the ligaments of the ribs and spine : a notice of these will be found in the following Section. Section II. LIGAMENTS OF THE TRUNK. The ligaments of the vertebrje, ribs, and sternum, are included in this Section. Articulation of the Ribs. The osseous part of each rib is united to the spinal column on the one side, and the rib cartilage on the other, by three sets of ligaments, viz., one between the head of the bone and the 344 DISSECTION OF THE THORAX. bodies of the vertebrce; a second from the neck and tubercle to the trans- verse processes of the vertebrie ; and a third between it and thet^artilage. Dissection. For the purpose of examining the ligaments between the rib and the vertebrae, take a piece of the spinal column with three or four ribs attached. After removing the intercostal and other muscles, and the loose tissue from the surface of the bones, the student will be able to define, as below, the ligaments passing from the head and neck of the rib to the bodies and transverse ])rocesses of the vertebrm. The ligaments attaching the costal cartilage to the rib and sternum are to be dissected on the part of the thorax which was removed in opening the cavity. Ligaments of the Head of the Rib. Where the head of the rib is received into a hollow in the bodies of two continuous vertebrae, the articulation is pro- vided with two retaining ligaments — costo- vertebral and interarticular, with two syno- vial sacs. The costo-vertehral ligament (fig. 108, ^), named stellate from its form, is composed of radiating fibres, and is placed in front of the joint. Attached by one end to the rib, it is divided at the other into three sets of fibres : The upper, the largest, ascends to the body of the vertebra above the rib head ; the lower descends to the vertebra below the head; and the central part is united with the fibro-cartilage between the vertebrae. Where the rib is in contact with only one vertebra, as in the first, eleventh, and twelfth, the ligament has but two sets of fibres. The chief fibres in those three joints are fixed into the body of that vertebra which is touched by the costal head ; whilst the as- cending band is attached to the body of the vertebra immediately above. In the first rib-joint the ascending band is continued to the last cervical vertebra. The interarticular ligament will be seen when the stellate is divided. It is a short thin band of fibro-cartilage, which is attached on one side to the ridge separating the articu- lar surfaces on tlie head of the rib, and on the other to the fibro-cartilage between the vertebrae. In the joints of the first, eleventh, and twelfth ribs, where the head is not in contact with the intervertebral substance, the ligament is absent. Synovial sacs. There are two sacs in the articulation, one on each side of the interarticular ligament. In the three joints before mentioned (1st, 11th, and 12th) there is but one sac. Movements. In the costo-vertebral articulation there is a gliding of the rib up and down, and forwards and backwards. Tlie movement of tlie head is more limited in tlie first seven ribs which are fixed to the sternum tlian in the others; and is greatest in the last two, in consequence of the Fig. 108. Ligaments of the Ribs and Ver- tebra (Bourgery). 1. Anterior ligament of the bodies of the vertebrae. 2. Lateral part of the anterior liga- ment of the spine. 3. Ligament (stellate) between the vertebrae and head of the rib. 4. Ascending costo transverse liga- ment. 5. Interspinovis ligament. LIGAMENTS OF THE RIB. 345 ribs being free anteriorly, and not fixed behind by a joint to the transverse process. During the increase and decrease of tlie chest tlie body of the rib is rotated out and in, around a line subtending the arc of the circle of vvliich its fore part is a segment. The degree of motion is greatest in the long- est ribs. Ligaments of the Neck and Tubercle. Three ligaments (costo- transverse) pass from the neck and tubercle of the rib to two transverse processes. And there is a synovial sac between the rib and its transverse process. The anterior costo transverse ligament (fig. 108, is larger and longer than the others. It ascends from the upper edge of the neck to the trans- verse process of the upper of the two vertebrm with wliich the head articu- lates: it is wanting to the first rib. Between this ligament and the verte- bra the posterior branches of the intercostal vessels and dorsal nerve pass ; and externally it is joined by the fibrous membrane between the strata of the intercostal muscles. The posterior costo-transverse (fig. 115, is placed at the posterior aspect of the rib. It is a short band of fibres between tlie rough part of the tubercle and the tip of the transverse process of the lower of the two vertebrae touched by the rib head. This band is longest in the lowest two articulations. The middle or interosseous costo-transverse is placed horizontally be- tween the neck of the rib and the transverse process with which the tubercle articulates. It will be best seen by sawing horizontally through the rib and the transverse process. Its fibres are mixed with reddish areolar tissue. In the lowest two ribs the interosseous costo-transverse blends in one band with the posterior costo-transverse ligament. Synovial sac. If the posterior ligament is divided, a synovial mem- hrane will be exposed in the joint between the tubercle of the rib and the transverse process. In the lowest two ribs, which do not touch transverse processes, the synovial sac is absent. Movement. In the motion of the rib, tlie bone glides upwards and downwards on the articular facet of the transverse process ; and the degree will be limited by the surrounding costo-transverse ligaments. Ligaments of the Sternal Cartilages. The cartilages of the true ribs except the first are united to the sternum by a fibrous capsule, which covers a synovial membrane; and externally they are joined to the osseous part of the rib. The first is generally ossified to the sternum ; and some of the lower cartilages touch each other, and are connected to- gether by fibrous bands with synovial membranes. In the cho7idro-sternal articulation (fig. 51, *), the cartilages are re- ceived into the depressions on the side of the sternum, and are fixed in their position by a capsule of surrounding fibres. In front and behind the capsule are thickened bands, which have been described as anterior and posterior ligaments. Between the cartilage and the bone is a synovial membrane. In the joint of the second cartilage there is an interarticular ligament (fig. 51, ®), as in the head of the rib, which joins the cartilage between the pieces of the sternum. A synovial sac exists on each side of the interarticular ligament. 346 DISSECTION OF THE THORAX. A separate band of fibres joins the cartilage of the seventh rib to the xiphoid cartilage, and is named costo-xiphoid ligament. Costal cartilage with the rib. The bony part of the rib is hollowed to receive the costal cartilage, and the posterium of the rib is the investing membrane between the two. Costal Cartilages to one Another. The contiguous surfaces of the costal cartilages from the sixth to the ninth are flattened, and are con- nected by ligamentous fibres ; each articulation is provided with a synovial membrane. Movement. There is only a limited gliding motion in the chondro- sternal and the interchondral articulations. The second rib-cartilage joint is the most movable. Asternal Cartilages. The cartilages of the three first false ribs are united only by end-bands of fibrous tissue, and are freer to move than those which are attached to the sternum. The lowest two, which are separate from one another, are the least fixed of all. Articulation of the Sternum (fig. 51). As the two pieces of the bone are united by cartilage without any synovial membrane, the kind of articulation is sometimes named synchondrosis. The articulation is strengthened by anterior and posterior longitudinal fibres. Movement. In articulations through the medium of cartilage, as here and in the pelvis, there is very little motion to be perceived, even when the osseous pieces are forcibly pulled by the hands. Articulation of the Vertebra. The vertebrae of the spinal col- umn are united together by two sets of ligaments — one for the bodies, and the other for the arch and processes. Along the spinal column the ligaments have a general resemblance, and one description will suffice except for those between the first two vertebrae and the head, and in the pelvis. Dissection. After the articulations of the ribs have been examined, the same piece of the spinal column will serve for the preparation of the ligaments of the bodies of the vertebrie. The anterior ligament of the bodies will be defined with very little trouble, by removing the areolar tissue. It is supposed that the spinal canal has been opened to examine the spinal cord, and that the posterior ligament of the bodies of the vertebrm is laid bare ; but if the canal should not be open, the neural arches of the vertebrie are to be removed by sawing through the pedicles. The remaining ligaments between the neural arches, spines, and articular processes of the bones, may be dissected on the piece taken away in open- ing the spinal canal. Ligaments of the Bodies. The bodies of the vertebrae are united by an anterior and a posterior common ligament, with an intervening piece of fibro- cartilage. The anterior common ligament (fig. 109, a) reaches from the atlas to the sacrum : it is widest opposite the lumbar vertebrae, and is narrowed upwards. It consists of a central wide and thick part («), and of a thinner ])ortion (5), on each side of the body of the vertebra?. If the central piece be cut across at intervals it will be seen to be thickest opposite the hollow of the bodies. The fibres of the middle part are longitudinal in direction. By detach- ing parts of the ligament, the superficial fibres will be seen to reach three or more vertebrae, whilst the deep extend from bone to bone. A greater LIGAMENTS OF VERTEBRA. 347 number of the fibres are attached to the intervertebral fibro-cartilages than to the bones ; and more are fixed to the margins than the centre of the body. The posterior common ligament (fig. 110), much thinner than the anterior, is contained in the spinal canal, lying on the posterior surface of the vertebrae, and extends from the sacrum to the occipital bone. Tliis ligament is Fig. 109. wide above, and diminishes in size down- wards, just the opposite of the anterior. In the neck, a, it is loose, and extends across the bodies. In the back and loins it is a narrow band, b, which sends off on each side a pointed process to be at- tached to the pedicle of the neural arch; and it is wider opposite tlie intervertebral disks than on the bodies, so that the margins are dentate. One surface of the ligament is in contact with the dura mater ; and between the band and the vertebra? are the intraspinal vessels. Its fibres are superficial and deep as in the anterior ligament, and are more closely united witli the intervertebral sub- stance than with the bone. ^ anterior Common Ligament op the Dissection. To see the intervertebral bodies of the Vertebrje. substance, the anterior and posterior com- Middle strong part, and ft, lateral mon ligaments must be taken away. One thin part of the ligament, vertebra should be detached from the fibro-cartilage to obtain a horizontal view of this structure ; and two other vertebra? sliould be sawn vertically to see the difference in the consistence and arrangement of the laminte. Fig. 110a. Fig. 110b. Two Views of the Posterior Common Ligament, c, of the Bodies of the Vertebra, to Show the Difference in Shape. A, refers to its form in the neck, and B, to its shape in the loins. The intervertebral substance (fig. Ill) is placed between the contiguous surfaces of the bodies of the vertebra?, from the axis to the sacrum. It 348 DISSECTION OF THE THORAX. forms a flattened disk between each pair of the vertebrae, and its width is determined by the size of tlie bones. It is connected in front and behind with the anterior and posterior common ligaments, and on the sides with the stellate ligament of the head of the rib. By means of the dissection before made, the intervertebral substance may be observed to consist of two distinct parts ; an external, firm and laminar, and an internal, soft and elastic (fig. 112). The outer laminar part (fig. 113, a) forms more than half of the disk, and is composed of pieces of fibro-cartilage with layers of fibrous tissue. All the strata are arranged one within another, like the scales of an onion, and are connected by their edges to the bodies of the vertebrae ; but all have not a vertical direction, for whilst the outer pieces are straight, the inner are bent with the convexity outwards (fig. 112) (Humphry). The laminm do not form comjdete rings, but those composed of fibrous tissue reach farther than those of fibro-cartilage : the free ends of both layers overlap. Each layer is constructed of oblique fibres ; and the fibres of one layer are directed across those of another like the parts of the letter X (fig. 111). This disposition of the fibres will be best seen on the disks between the lumbar vertebrae ; and it may be rendered evident by dissecting layer after layer. Fig. 111. Fig. 112. Intervertebral Substance in the Lum- Vertical Section of the Intervertebral Sub- bar Region, with its laminae displayed. stance, to show the direction of the layers. a. Superficial, and b, deeper layer, the fibres a. Circumferential layers bent outwards. in each taking a different direction. b. Central pulpy part. The central or pulpy portion of the disk (fig. 113, h) is very soft and elastic, and projects when two vertebra? and the interposed mass are sawn through. Placed nearer the back than the front of the disk, it is more marked in the loins and neck than in the dorsal region. It has a yellow- isli color, and is deficient in the stratiform arrangement so conspicuous at the circumference. Towards the confines of the two portions of the intervertebral substance, there is an alternating arrangement of fibrous tissue and fibro-cartilage, thougli the former is gradually diminishing ; but towards the centre a loose fibro-cartilaginous material with large cells preponderates. LIGAMENTS OF VERTEBRA. 349 The surfaces of the vertebrje in contact with tlie disk have a cartilagin- ous covering ; this may be seen by cutting tlie intervertebral substance from the bone. Over the centre of the osseous surface it forms a continuous layer, but towards the circumference it consists of separate pieces. The disks are thicker between the lum- bar and cervical, than between the upper and middle dorsal vertebra?; and where the spinal column is arched forwards, as in the loins and neck, they are deepest at the an- terior edge, being wedge-shaped. The tliin- nest piece is situate between the second and tliird cervical vertebrm, and the thickest between the fifth lumbar and the sacrum. Use. The intervertebral substance unites together the vertebrje so firmly as to pre- a Horizoxtal Cut through an In- vent displacement of those bones without tervkrtebral Fibro-carilaoe. runture of it part. T) r- .1 i. 1 1 X Pulpy central part of the fibro-carti- By means of the central elastic part the revolving motion of one bone on anotlier is produced ; and the degree of the movement is limited by the circumferen- tial laminar portion. Through its wedge-shaped form the disk is chiefly instrumental in giving rise to the convexity of the spinal column in the loins and neck ; and through its elasticity it moderates the effect of jars or shocks transmitted from bone to bone. The depth of its several pieces amounts to about a fourth of the length of the movable part of the spinal column ; but as it yields under pressure, the height of the body will be shorter from half an inch to an inch in the course of the day, according to the fatigue undergone. Ligaments of the Neural Arch and Processes. The several pro- cesses of the vertebra? have special uniting ligaments : thus the articular processes are joined by a capsule and a synovial membrane ; the neural arches are connected by yellow ligaments ; the spinous processes have one band along the tip and another between them ; and the transverse pro- cesses are provided with intervening bands of fibres. Ligaments o f Articulating processes. Between the articulating processes there is a movable joint, in which the bones are covered with cartilage, and are surrounded by a loose capsular ligament of scattered fibres, en- closiug a synovial membrane. In the cervical part of the spine the cap- sular ligaments are looser than in the dorsal or lumbar region. Movement. With flattened articular surfaces is combined a gliding of one bone upon another. This movement is least limited in the neck, the loins, and the lower dorsal vertebne. By the difference in the shape of the articulating processes, the kind of motion in the spine is determined ; and by their arrangement the degree is limited, and the vertebrae are partly maintained in situ. In dislocation of the S{)inal column they are generally broken before a vertebra can be dislodged from its imbricated position. Ligaments of the arches. The ligamenta suhjlava (fig. 114,^) so named from their color, are situate between the neural arclies of the vertebne, and close the spinal canal behind. Between each pair of arches are two Fig. 113. 350 DISSECTION OF THE THORAX. ligaments, one for each half of the arch, which approach one another along the middle line, and reach on each side from the pedicle of the arch to the root of the spinous process. Each consists of elastic yellow tissue. It is attached above to the inner surface of the one, but below to the upper border and outer surface of the other neural arch. Between the first two vertebrae and the skull there are special fibrous ligaments in the corresponding situation (see p. 166). Ligaments of the spines. Along the tips of the spinous processes of the dorsal lumbar vertebrae is a longitudinal band of fibres (fig. 115, — the Fig. 114. Fig. 115. An Inner View of the Neural Arches OF THE Vertebra, with their Inter- posed Ligaments. 1 and 2. Ligamenta subflava. (Bourgery and Jacob.) Ligaments of the Processes of the Vertebr.®, AND of the Ribs. (Bourgery.) 1. Supraspinous band of ligament. 2. Ligamentum subflavum. 3. Posterior costo-transverse ligament : on the op- posite side the band has been removed and the joint opened. 4. Intertrausverse ligament. supraspinous ligament. It is thickest in the lumbar region of the spine, and is formed by the superficial and deep fibres ; the former reach over three or more spines, whilst the latter pa.ss from bone to bone. It is closely united with the tendons of the muscles. The band of the ligamentum nuchae, which is composed of fibrous tissue, takes its place in the neck. Along the spinal column there are also thin membranous interspinous ligaments (fig. 108, ®), which reach from the root to the tip of the spinous processes. The strength of these bands is dependent upon the interval they fill ; they are more marked in tlie lumbar than the other vertebrae, and they are least strong in the cervical region. Ligaments of the transverse process. In the loins i\\Q inter-transverse MOTION, OF SPINAL COLUxMN. 351 ligaments are thin membranous bands in the intervals between the pro- cesses. In the dorsal vertebraR they are round bundles of fibres (fig. 115, ^). And in the neck the fibres exist only at the apex of the processes, or they may be wanting here and there. Ligaments of Special Vertebra. The ligaments of the first two cervical, and the sacral and coccygeal vertebrae, will be given with the dissection of the neck (pp. 166, 167) and of the pelvis (Section vii.). Movements of Spinal Column. The spinal column can be bent for- M^ards, backwards, and to each side ; and can be rotated. \xv jiexion the vertebrae between the axis and sacrum are bowed for- M’ards. The greatest movement takes place between the last two lumbar vertebrae and the sacrum (Humphry) ; there is an intermediate degree in the neck ; and the least is in the upper half of the dorsal region, where the ribs are united to the sternum. The bodies of the bones are brought nearer together in front, whilst they are separated behind. The inferior pair of articular processes of the second vertebra glide upwards on the upper articular of the third vertebra ; the inferior of the third bone move in like manner on the upper processes of the fourth ; and so on throughout the movable column. The ligament in front of the bodies is loose, but the posterior, and those uniting the neural arches and processes, are stretched. The fore part of each intervertebral disk is squeezed and thinner, and the back is elongated. In extension^ the vertebrae are arched backwards, but not to so great a degree as when the spine is bent forwards. The motion is most in the neck ; and is least in the dorsal vertebrae, which are fixed by the true ribs and the sternum, and are impeded in their movement by the overlapping spinous processes. The posterior parts of the vertebrae are approximated, whilst the ante- rior are separated ; and the inferior articular processes of each (from the second cervical to the sacrum) glide downwards, on the upper articular processes of the next succeeding bone. The condition of the ligaments is the opposite to that in flexion. Thus, the intervertebral disks are compressed behind and widened before ; the spinous and subflaval are relaxed ; the anterior common of the bodies is tightened, and the hinder band is slackened. Lateral inclination. The spine can be curved to the right or the left side. Like the other movements, this is least in the more fixed upper dorsal vertebrae, and is greatest in the neck. On the concave side of the curve, say the right, the bodies are brought nearer together ; and are carried away from each other on the opposite aspect. The right inferior articular surface glides down, and the left up, in the joints with the vertebra beneath. On the right side the ligaments will be relaxed and the intervertebral substance compressed ; and on the left those structures will be tightened so as to check the movement. Rotation is the twisting of the bodies of the vertebrae around a line through their centres, the fore part being turned to the right and to the left. Its degree is greatest in the cervical and the upper dorsal vertebrae, but is absent in the lumbar part of the column. The vertebral bodies are directed horizontally, and the articular pro- cesses move differently on the two sides. Supposing the face turned to the right, the processes of the right side glide inwards towards, and those of the left side outwards from the spinal canal. 352 DISSECTION OF THE THORAX. The flat ligaments and the intervertebral disks of the bodies, and the ligaments of the neural arches, will be less tight on the side to which the face is directed than on the other. Dislocation of one vertebra from another without fracture seldom occurs, in consequence of the way in which the inferior pair of articular processes are placed behind the superior of the next following bone, like scales. In the cervical region, Avhere the articular surfaces are more horizontal, sim- ple displacement may occasionally take place. DISSECTION OP THE BACK. 353 CHAPTER Y. DISSECTION OF THE BACK. Directions. The dissection of the Back may be undertaken by one stu- dent ; or conjointly by the dissectors of the head and up{)er limbs^ — the former preparing the neck, and the latter making ready the parts in the dorsal and lumbar regions. If the Back should be allotted to more than one student, the dissector of the upper limb may attend chiefly to the paragraphs marked with an asterisk ; and the dissector of the neck may study specially the paragraphs which are not so marked. But as many of the dissections in the earlier stages require the co-operation of the students employed on the same side of the body, a genei-al attention may be given to the whole by each. The dissector of the abdomen is to examine the arrangement of the fas- cia lumborum, after the first layer of muscles has been learnt. Position. The body lies with the face downwards ; and the trunk is to be raised by blocks beneath the chest and the pelvis, so that the limbs may hang over the end and sides of the dissecting table. To make tense the neck, the head is to be depressed and fastened with hooks. In this region there are five successive strata of muscles, amongst which vessels and nerves are interspersed. Dissection. The first step is to raise the skin in two flaps, by means of the following incisions : — One cut is to be made along the middle of the body from the occipital protuberance to the back of the sacrum. Another is to be carried from the last dorsal vertebra to the acromion process of the scapula. The flap of skin above the last cut is to be turned outwards by the dissectors of the head and upper limb. By another transverse incision opposite the iliac crest, the remaining piece of integument may be detached, and reflected by the dissector of the upper limb in the same direction as the other flap. Under the upper flap of skin is placed the trapezius, and underneath the lower one the latissimus dorsi muscle. The cutaneous nerves may now be sought in the superficial fatty layer : they are accompanied by small cutaneous arteries which will guide the student to their position. The nerves vary much in size in the different parts of the Back, and their number is also irregular ; as a general rule, there is one opposite each vertebra except in the neck. To find them in the cervical region look near the middle line, from the 3d to the Gth vertebra, and trace an offset from the third nerve upwards to the head : the branch of the second nerve (large occipital) has been laid bare at the back of the head (p. 20). Opposite the upper part of the thorax, they will be best found near the spines of the vertebrae, where they lie at first beneath the fat ; but at tlie lower part, and in the loins, they issue in a line with the angles of the ribs. The cutaneous branches of the sacral nerves are included in the dissec- tion of the lower limb. 23 354 DISSECTION OF THE BACK. Cutaneous Nerves. Tlie tegumentary nerves are derived from the posterior primaiy branches of the spinal nerves, which subdivide amongst the deep muscles into two pieces, inner and outer. Arteries accompany- ing the greater number of the nerves, bifurcate like them, and furnish cutaneous offsets. Cervical nerves. In the neck the nerves are derived from the inner of the two pieces into whicli the posterior trunks bifurcate : they perforate the trapezius, and supply the neck and the back of the head. They are four in number, viz., one from eacli, except the first and the three last. The branch of the second nerve is named large occipital, and accom- panies the occipital artery to the back of tlie head (p. 2o). The branch of the third cervical nerve supplies a transverse offset to the neck, and then ascends to the lower part of the head, where it is dis- tributed near the middle line, uniting with the great occipital nerve * Dorsal nerves. These are obtained from both the inner and outer pieces — the upper six from the inner, and the lower six from the outer. On the surface they are directed outwards in the integument over the trapezius and latissimus dorsi muscles. The upper six perforate the trapezius near the spines of the vertebrae ; and the branch of tlie second, which is larger than the rest, reaches as far as the scapula. The lower six pierce the latissimus dorsi mostly in a line with the angles of the ribs ; they are oftentimes uncertain in number. * Lumbar nerves. In the loins the nerves are derived from the outer pieces of the first three ; they perforate the latissimus dorsi muscle at the outer border of the erector sjtinm, and crossing the iliac crest of the in- nominate bone, are distributed in the integuments of the buttock. * First Layer of Muscles (fig. 110). Two muscles, the trapezius and the latissimus dorsi, are included in this layer. Dissection. The sujierficial fatty layer is to be taken from the trape- zius and latissimus dorsi in the direction of the fibres of each, viz., from the shoulder to the s}iinal column ; and the upper limb is to be carried backwards or forwards according as it may be necessary to put on the stretch different portions of the muscles. Some of the cutaneous nerves and vessels may be left, in order that they may be traced afterwards through the muscles to their origin. * The TRAPEZIUS YiuscLE (fig. IIG, is triangular in sliape, with the base towards the spine, but the two have a trapezoid form. Tlie muscle has an extensive aponeurotic origin along the middle line from the spines of all the dorsal vertebrce and their supraspinous ligament ; from the spinous process of the seventh cervical vertebra ; from the ligamentum nuchaj between the last point and the head ; and lastly from the inner third of the sujierior transverse ridge of the occipital bone. From this origin the fibres are directed outwards, converging to the shoulder, and are inserted into the outer third of the clavicle, at its posterior aspect ; into the pos- terior border of the acromion ; and into the upper edge of the spine of the scapula as far as an inch from the root of that process, as well as into a rough impression on the surface of the spine near the hinder part. The muscle is subcutaneous. At the outer side the lowest fleshy fibres end in a small triangular tendon, which glides over the smooth surface at the root of the S[)ine of the scapula. The anterior border bounds behind the posterior triangular space of the neck. By its insertion the trapezius corresponds with the origin of the deltoid muscle. Action. If all the fibres of the muscle act, the scapula gliding on the TRAPEZIUS MUSCLE. 355 ribs is moved upwards and towards the spinal column ; but the upper fibres can assist other muscles in elevating, and the lower fibres will help in depressing that bone. When the scapula is prevented from gliding on tlie ribs, the trapezius imparts a rotatory movement to it, and raises the acromion. Fig. 116. MnscLES OF THE Back. On the left side the first layer is shown, and on the right side the second layer, with part of the third. A. Trapezius. e. Khomboideus major. B. Latissimus dorsi. F. Splenius. c. Levator anguli scapulaj. G. Serratus posticus inferior. D Khomboideus minor. Dissection. The fibres of the trapezius are to be divided near the sca- pula, over the situation of tlie S[)inal accessory nerve, so tliat the ramifica- tions of that nerve in the muscle, and its junction witli the brandies of the cervical plexus may be observed. A small artery to the trapezius (art. superficialis colli) accompanies the nerve. 356 DISSECTION OF THE BACK. The spinal accessory cranial nerve (p. 114), having crossed the poste- rior triangle of the neck, passes beneath the trapezius, and forms a plexi- form union with branches of the third and fourth nerves of the cervical plexus. The nerve is distributed nearly to the lower border of the muscle. Dissection. To see the parts covered by the trapezius, the pieces of the divided muscle are to be thrown inwards and outwards. The dissector of the neck should now clean the splenius, and define the parts beneath the clavicle, viz. the posterior belly of the omo-hyoid mus- cle with the suprascapular nerve and vessels ; the transverse cervical ves- sels ; and the small branches of nerves to the levator anguli scapulae, and rhomboid muscles. If tlie trapezius be detached along the middle line, the ligamentum nuchae, from which it takes origin, will be brought into view. * The dissector of the upper limb should clean the fibres of the rhom- boidei and levator anguli scapulae muscles, which are fixed to the base of the scapula ; and whilst this is being done, the scapula is to be drawn away from the trunk to make tense the fleshy fibres. * Parts covered by the trapezios. The trapezius conceals in the neck the splenius, a small part of the complexus, and the levator anguli scapu- l^e ; in the dorsal region it covers the following muscles, the rhomboidei, the erector spinae, and the latissimus dorsi. Near the insertion it lies over the supraspinatus muscle. The ligamentum nuchce is a narrow fibrous band, which extends from the spinous process of the seventh cervical vertebra to the occipital protuber- ance. From its under part processes are attached to the spines of the six lower cervical vertebrae, so that it serves as a partition between the muscles of the opposite sides of the neck. In man it is not formed of elas- tic tissue. * The LATISSIMUS DORSI (fig. 116,®) is the widest muscle in the back, and is thin and aponeurotic at its inner attachment. It arises along the middle line from the spinous processes of the six lower dorsal, all the lum- bar, and the upper two sacral vertebrie, as well as from the supraspinous ligament. On the outer side it arises by an aponeurosis from the outer edge of the posterior half of the iliac crest ; and by three or four fleshy processes from as many of the lower ribs, which digitate with pieces of the external oblicpie muscle of the abdomen. And between the outer and inner attachments it is inseparably blended below with the subjacent ten- don of the multifidus spinae. All the fibres converge to the inferior angle of the scapula, and after crossing that point of bone, are continued for- wards to be inserted by tendon into the bottom of the bicipital groove of the humerus (p. 236). The muscle is subcutaneous, except a small part of the upper border which is covered by the trapezius. Near the scapula there is a space be- tween the two, in which the rhomboid muscles appear. The lower or anterior overlays the edge of the external oblique muscle of the abdominal wall in the interval between the last rib and the iliac crest, with the ex- ception of a small part below. Frequently the latissimus has a distinct fleshy slip from the inferior angle of the scapula. Action. If the arm is hanging loose the muscle can move it behind the back, rotating it in at the same time. If the limb is raised, the latissimus, combining with the pectoralis and teres, will depress the humerus. From its attachment to the sca[)ula this bone can be depressed with the arm. Supposing the arm fixed, the fibres may elevate the ribs as an inspira- FASCIA LUMBORUM. 357 tory muscle ; or they may assist the pectoralis major in drawing the movable trunk towards the humerus, as in the act of climbing. * Dissection. The latissimus is to be divided about midway between the spines of the vertebrae aud the angle of the scapula, and the pieces are to be reflected inwards and outwards. In raising the inner part of the muscle, care must be taken not to destroy either the thin lower serratus with which it is united, or the aponeurosis continued upwards from the serratus. In the interval between the last rib and the iliac crest the latis- simus is adherent to the aponeurosis of the transversalis abdominis muscle, and should not be detached from it. * Parts covered by the latissimus. The latissimus dorsi lies on the erector spinse, the serratus posticus inferior, and the lower ribs with their intercostal muscles. As it rests on the angle of the sca[)ula, it conceals the teres major, and })art of tlie rhomboid muscle. Its position to the teres is worthy of note : — at the angle of the sca|)ula it covers the posterior surface of the teres, but nearer the humerus it turns round the lower bor- der, and is inserted in front of that muscle. Between the angle of the scapula and the humerus the latissimus forms part of the posterior boundary of the axilla. Dissection of fascia lumhorum. After the latissimus dorsi has been reflected, the dissector of the abdomen can look to tlie disposition of the posterior tendon of the transversalis abdominis (fascia lumborum) between the last rib and the innominate bone. In the spot referred to are portions of the external and internal oblique muscles, left in the dissection of the wall of the abdomen. After the removal of those muscles the aponeurosis of the transversalis muscle (fas- cia lumborum) appears, and perforating it are two nerves — one, the last dorsal with an artery near the last rib: and the other, the ilio-hypogastric with its vessels, close to the iliac crest. Two offsets are prolonged backwards from this fascia to the transverse processes. To see the more superficial layer which passes beneath the erector spinac to the apices of the processes, the latissimus dorsi is to be cut through (both its aponeurosis and fleshy part) by a horizontal incision directed outwards from the spinous processes, on a level with the third lumbar vertebra. On raising the outer border of the erector spinae muscle which comes into view, the strong process of the fascia will be apparent. After dividing transversely this first prolongation, another muscle (quad- ratus lumborum) will be seen; and on raising its outer border the second thin offset of the fascia will be evident on the abdominal aspect of that muscle. The fascia lumborum (fig. 13G, '^) is the posterior aponeurosis or tendon of the transversalis abdominis muscle, and occupies the interval between the last two ribs and the crest of the hip-bone. By its cutaneous surface it gives attachment to the internal oblique muscle, and sometimes to the external oblique. The last dorsal (’^) and ilio-hypogastric if) nerves, ac- companied by vessels, pierce it in their course from the abdomen. From the inner part of the aponeurosis two offsets are prolonged to the trans- verse processes of the lumbar vertebrae, and inclose the quadratus lum- borum in a sheath. The more superficial of the two is the strongest ; it lies beneath the erector spinae in this position of the body, and is connected to the apices of the transverse processes, but it also fills the intervals between them : at 358 DISSECTION OF THE BACK. the outer border of the erector spinae it blends with the aponeurosis of the latissimus dorsi and inferior serratus. The deeper or anterior prolongation passes on the abdominal surface of the quadratus lumhorum, and is fixed to the tips and borders of the trans- verse processes. In like manner the erector spinoe lies in another sheath, which is formed by tlie vertebral aponeurosis and the tendons of the latissimus and serratus on the one side, and by tlie superficial of tlie two prolongations of the fascia lumborum on tlie other. * Second Layer of Muscles (fig. IIG). This stratum contains the elevator of the angle of *tlie scapula, and the large and small rhomboid muscles; besides these, the posterior belly of the omo-hyoid muscle, and some vessels and nerves turning backwards towards the scapula are included. Dissection. By the reflection of the trapezius and latissimus, and by the dissection made subsequently (p. 3o5), the several parts in this layer will have been sufficiently prepared for learning. * The LEVATOR ANGULi SCAPULA-: (fig. 116, ai’ises by tendinous slips from the posterior transverse processes of the ujiper three or four cervical vertebras. The fibres form rather a roundish muscle, and are inserted into the base of the scapula between the spine and the superior angle. At its origin the muscle lies beneath the sterno-mastoideus, and at its insertion beneath the trapezius, where it touches the serratus magnus mus- cle ; the rest of the muscle ap})ears in the posterior triangular space of the neck. Beneath it are some of the other cervical muscles, viz., splenius colli and cervicalis ascendens. Action. The muscle raises the angle and hinder part of the scapula, and de})resses the acromion; but united with the up])er part of the trape- zius, which prevents the rotation down of the acromion, it shrugs the shoulder. When the shoulder is fixed, the neck can be bent laterally to the same side. * Rfiomboidei Muscles. The thin muscular layer of the rhomboidei is attached to the base of the sca})ula, and consists of two pieces, large and small, which are separated by a slight interval. * The rhonihoidens minor (fig. 116, ®) is a thin narrow band, which arises from the spines of the seventh cervical and first dorsal vertebra3, and the ligamentum nuchoe; it is inserted into the base of the scapula, opposite the smooth surface at the root of the spine. * The rhomhoideus major (fig. 116, is larger than the preceding by the width of three or more spinous processes. It arises from the spines of four or five dorsal vertebrae below the rhomhoideus minor, and from the supraspinous ligament; and its fibres are directed outwards and downwards to be fixed to the base of the scapula between the spine and the lower angle. Sometimes all the fibres do not reach the scapula directly, some ending on a tendinous arch near the bone. The rhomboidei muscles are covered chiefly by the trapezius and latis- simus; but a portion of the larger rhomboid is subcutaneous near the angle of the scapula. Action. From the direction of their fibres both rhomboidei will draw the base of the scapula upwards and backwai'ds, so as to depress the acro- mion. In combination with the trapezius they will carry the scapula SCAPULAR VESSELS. 359 directly back ; for as one tends to raise, and the other to depress the acro- mion, the bone will be moved in a direction between the two forces. By their united action the muscles help to fix the scapula. The OMO-iiYOiD MUSCLE cotisists of two fli^shy bellies, anterior and posterior, which are united by an intervening tendon. Only the posterior half is now seen. The muscle arises from the upper border of the scapula behind the notch, and from the ligament converting the notch into a foramen. The fibres form a thin, riband-like muscle, which is directed forwards across the lower part of tlie neck, and ends anteriorly in a tendon beneath the sterno-mastoideus (p. 72). The fleshy belly of the muscle is placed partly beneath the trapezius ; and is partly superficial in the posterior triangular space of the neck, where it lies above the clavicle and the subclavian artery. It crosses tlie suprascapular vessels and nerve, and the brachial plexus near the sca[)ula. Action. For the supposed use of the posterior belly of the omo-hyoideus, see page 72. The suprascapular artery., a branch of the subclavian (p. 78), is directed outwards across the lower part of the neck to the dorsum of the scapula. The vessel courses behind the clavicle with the suprascapular nerve, but beneath the trapezius and omo-hyoid muscles to the supraspinal fossa. Before entering tlie fossa it furnislies a small branch (supra-acroniial) to the upper surface of the acromion. The suprascapular nerve., an offset of the brachial plexus (p. 79), is inclined backwards to the superior border of the scapula. It passes through the notch in the upper costa of the bone, and terminates beneath the supra- spinatus in the muscles of the dorsum of the scapula (p. 248). The transverse cervical artery, also a branch of the subclavian (p. 78), has the same direction as the suprascapular, towards the upper part of the scapula, but it is higher than the clavicle. Crossing the upper part of the space in which the subclavian artery lies, it passes beneath the trapezius, and divides into the two following branches — superficial cervical and pos- terior scapular : — a. The superficial cervical branch is distributed chiefly to the under surface of the trapezius, though it furnishes offsets to the levator anguli scapulae and the cervical glands. h. The posterior scapular branch crosses beneath the elevator of the angle of the scapula, and turns along the base of the scapula beneath the rhomboid muscles. If the rhomboid muscles are divided, the artery will be seen to furnish branches to them ; and to give small anastomotic twigs to both surfaces of the scapula. This branch arises very frequently from the third part of the subclavian trunk. The suprascapular and transverse cervical veins have the same course and branches as the arteries above described ; they open into the external jugular, near its junction with the subclavian vein. Nerve to the rhomboid muscles. This slender nerve of the brachial plexus (p. 79) courses beneath the elevator of the angle of the scapula, and is distributed to the rhomboidei on the under surface. Before its termination it supplies one or two twigs to the elevator of the scapula. * Third Layer (fig. 117). In this stratum are the following muscles : — the serratus posticus superior and inferior, with the splenius. * Dissection. By reflecting the rhomboidei muscles towards the spinous 360 DISSECTION OF THE BACK. processes, and removing loose areolar tissue, the thin upper serratus muscle beneath them will be laid bare. The splenius and the inferior serratus have been previously exposed by the reflection of the trapezius and latissimus. * The SERRATi muscles are very thin, and receive their name from their toothed attachment to the ribs. They are two in num- ber, superior and inferior, and have aponeurotic origins from the spines of the vertebrae. * The serratus posticus supe- rior (fig. 117, arises from the ligamentum nuchie, and from the spinous processes of the last cer- vical, and two or three upper dorsal vertebrje. The fleshy fibres are inclined down and out, and are inserted by slips into the second, third, and fourth ribs, external to their angles. The muscle rests on the sple- nius, and is covered by the rhom- boideus major. * The serratus posticus infe- rior (fig. 116,®) occupies the lumbar region, and is wider than the preceding muscle. Its apo- neurosis of origin is inseparably united with that of the latissimus dorsi, and with the fascia lumbo- rum, and is connected to the spinous processes of the last two dorsal and first three lumbar ver- tebrae. Tlie fleshy fibres ascend to be inserted into the last four ribs in front of their angles, each successive piece extending further forwards than the one below. This muscle lies on the mass of the erector spinae ; and with its tendon the vertebral aponeurosis is united. Action. The superior serratus raises the upper ribs, and officiates as an inspiratory muscle ; and the inferior, depressing the lower ribs, becomes an ex[)iratory muscle. Theile supposes the inferior to act indirectly as a muscle of ins])iration, because, by fixing the lower ribs, it enables the dia- phragm to contract more effectively. * The vertebral aponeurosis is a fibrous expansion, which is spread over the fourth layer of muscles, and confines the erector spinae in the vertebral groove. Interiorly it is thickened by the tendons of the latissimus and lower serratus; but it is continued above beneath the splenius, without joining the up})er serratus, and blends with the deep fascia of the neck. Fig. 117. Part of the Third Later of the Back- Muscles. A. Serratus posticus superior, B. Splenius capitis, c. Splenius colli. D. Ilio-costalis. E. Longissimus dorsi. F. Spinalis dorsi. SERRATI AND SPLENIUS MUSCLES. 361 Internally it is attached to the spinous processes. Externally it is con- nected to the posterior third of the iliac crest, uniting with the tendon of the latissimus ; between the hip-bone and the ribs, to the fascia lumborum; and in the dorsal region to the ribs and a fascia over the intercostal mus- cles. Below, between the pelvic and vertebral attachments, it blends with the underlying tendon of the erector spinje and multitidus. * Dissection, The upper serratus is to be cut through, and the subja- cent vertebral aponeurosis to be taken away ; and the part of the splenius muscle under the serratus should be cleaned. The SPLENIUS muscle (fig. 117) is thin and elongated; it is undivided internally, but is split externally into two parts. It takes origin along the middle line from the six upper dorsal s|)ines, from the seventh cervical, and from the ligamentum nuclne as high as the third cervical vertebra. Some fibres ascend to the head (splenius capitis), and others to the neck (splenius colli). The splenins colli, c, is inserted by tendinous slips into the posterior transverse processes of the upper three cervical vertebrce with, but behind the attachment of the elevator of the angle of the scapula. The splenins capitis, b, much the largest, is inserted by a thin tendon into the aj)ex and hinder border of the mastoid process, and into the bone behind it for about an inch and a half. This muscle is situate beneath the trapezius, the rhomboidei, and the serratus superior; and the insertion into the occipital bone is beneath the sterno-mastoideus. The complexus muscle projects above the upper border of the splenius capitis. Action. The cranial parts of both muscles will carry the head directly back; and one will turn the face to the same side. The splenius colli of both sides will bend back the upper cervical verte- bras ; but one muscle will turn the face to the same side, being able to rotate the head by its attachment to the transverse jirocess of the atlas. * Fourth Layer. In this layer are included the spinalis dorsi ; the erector spinas, with its divisions, and accessory muscles to the neck ; and the complexus muscle. Most of the vessels and nerves of the Back are to be learnt with this layer of muscles. Dissection (fig. 118). To lay hare the complexus muscle in the neck, the sjdenii must be detached from the spinous processes, and thrown out- wards. And whilst the large erector spinm is being displayed in the dorsal and lumbar regions by the dissector of the upper limb, two prolongations from it to the cervical vertebrae and the head are to be defined by the dissector of the neck : One, a thin narrow muscle, the cervicalis ascendens, is con- tinued beyond the ribs from the outer piece of the erector (ilio-costalis), and is to be separated from the muscles around. The other is a larger offset of the inner piece of the erector (longissimus dorsi); blended at first with the fibres of the longissimus, it is divided afterwards, like the sple- nius, into a cranial part (trachelo-mastoid) and a cervical part (transversalis colli). * The serratus inferior is to be detached with the vertebral aponeurosis from the spines in the dorsal region, and the areolar tissue is to be cleaned from the surface of the large mass of the erector sf)ime which now comes into view. Op{)osite the last rib is the beginning of an intermuscular in- terval, which divides the erector spime into an outer piece (sacro-lumbalis), and an inner (longissimus dorsi). By sinking the knife into this interval 862 DISSECTION OF THE BACK. the sacro-lumbalis may be turned outwards, so as to uncover the fleshy slips of its accessory muscle, which are fixed to the angles of the ribs : a muscular slip (cervicalis ascendens) is prolonged from this to the neck. * In preparing the sacro-lumbalis muscle, the external pieces of the dor- sal nerves with their accompanying arteries will appear. * Before the longissimus can be displayed, it will be needful to detach, and raise towards the spinous processes the thin muscular fasciculus of the spinalis dorsi, which lies between that muscle and the spines of the verte- bne in the dorsal region. Then the attachments of the longissimus dorsi are to be traced out. Externally it has thin muscular processes of insertion into about the eight lower ribs. Internally it is inserted into the trans- verse processes of the lumbar and dorsal vertebrae by rounded tendons ; and for the purpose of seeing these tendons, the longissimus should be drawn away from the spinous processes, and its superficial aponeurosis should be cut through below the ribs, along the line of separation between the muscle and the fleshy multifidus spinae on the inner side. F rom this muscle, as from the sacro-lumbalis, a fleshy piece (transversalis colli and trachelo-mastoid) is continued into the neck. * Between the longissimus and the multifidus spinae are the internal pieces of the dorsal and lumbar nerves, and of the intercostal and lumbar arteries and veins. * The SPINALIS DORSI is placed on the side of the spines of the dorsal vertebrae, and is united with the longissimus dorsi. Interiorly it arises by tendinous processes from the spines of the last two dorsal and first two lumbar vertebrae, and by fleshy fibres from the contiguous tendon of the longissimus. From this origin the fibres ascend, forming arches, whose concavity looks inwards, and are connected by tendinous processes to the spines of the dorsal vertebrae as low as the eighth or ninth, or only for half that extent. Action. Both muscles contracting will extend the dorsal region of the spine. Perhaps the muscle of one side may tend to incline the spine laterally. * The ERECTOR SPINAE is the muscular mass on the side of the spine in the lumbar region. It is single and pointed below ; and its cutaneous sur- face is covered near the sacrum by a wide and strong tendon, which is common to it and the multifidus spinae. The muscle arises at the pelvis from the posterior fifth of the crest of the hip-bone at the inner aspect, exce[)t opposite the upper spinous process : in the lumbar region it is at- tached by fleshy and tendinous pieces to the transverse processes, to the tubercle (process, accessorius) at the root, and to the layer of the fascia lumborum external to each. Opposite the last rib it divides into ilio-cos- talis and longissimus dorsi. * The iLio-cosTALis (sacro-lumbalis) is the smallest of the two [)ieces resulting from the division of the erector spinic. Its fibres end in six or seven flat tendons, which are connected together by their margins, and are inserted into the angles of as many of the lower ribs. The muscle is continued onwards to the other ribs and the neck by a fleshy part, which constitutes the two under-mentioned muscles : — * 'riie mnscnhis accessorius ad sacro-lumhaium begins by a series of tendinous and fleshy bundles on the angles of the lower six ribs, internal to the insertion of the ilio-costalis ; and it ends in tendons, which are in- serted into the remaining ribs (upper six), in a line with the ilio-costalis, and into the posteidor transverse process of the seventh cervical vertebra. LONGTSSIMUS DORSI. 363 The cervicalis ascendens is a muscular slip prolonging the accessorius into the neck : this muscle is attached to four ribs (third, fourth, fifth, and sixth), and is inserted into the posterior transverse processes of three cer- vical vertebrae, viz., sixth, fifth, fourth. * The LONGissiMus DOKSi gradually decreases in size as it ascends along the thorax. Internally the muscle is inserted into the transverse processes of all the dorsal vertebrae by a series of tendinous and fleshy bun- dles ; and externally it is attached to the ribs, except the first two or three, by thin fleshy processes between the tubercle and angle. Its mus- cular prolongation to the neck is united with the upper fleshy fibres, and splits into the two following pieces: — The transver satis colli (fig. 118, ®) arises from the transverse pro- cesses of the upper six dorsal vertebra?, and is inserted into the posterior transverse processes of the cervical vertebra?, except the first two and the last. The trachelo-mastoid muscle (fig. 118, (transversalis capitis?) arises in common witli the preceding, and is attached, besides, by distinct ten- dons to the articular processes of the last three or four cervical vertebne. The muscle is thin, and is inserted beneath the sjdenius into the upper half of the posterior part of the mastoid process: its insertion is about three-quarters of an inch wide.* * Connections of the erector spince. The erector spin* and its prolonga- tions occupy the lumbar, thoracic, and cervical parts of the Back. In the loins the muscle is contained in an aponeurotic sheath (p. 3o8), and has the multifidus spime on its inner side : its attachment on the in- ner surface of the innominate bone corresponds in part with the origin of the gluteus maximus on the outer side. The superficial tendon, which is common to it and the multifidus, will be described with the last-mentioned muscle (p. 371). Opposite the ribs the ilio-costalis and longissimus dorsi are concealed by the muscles of the other layers already examined. In the neck its accessory small muscles lie underneath the splenius and the trapezius : — the cervicalis ascendens is attached in a line with, but below the sydenius colli ; and the transversalis colli and trachelo-mastoid are more internal, or between the splenius and cervicalis and the com- plexes. Action. Taking their fixed point at the pelvis, both erectors will keep the spine straight in sitting and standing ; and, in rising from stooping to the ground, they will bring the trunk into the erect jiosture. In laborious respiration, the spine being fixed, the muscles are able to depress the ribs, and assist in the expulsion of the air from the thorax. One muscle will incline the spinal column laterally and to its own side. The cervical prolongations of the erector act on the neck and head, as below : — The cervicalis ascendens. Taking their fixed point below, both mus- cles will extend the cervical part of the spine : and acting from the trans- verse processes they will elevate the ribs. One muscle will give a lateral movement to the neck. 1 The anatomy of the prolongation from the longissimus might he simplified by describing it as the transvei'salis muscle with a double insertion, like the splenius, into the head and neck. In accordance with the nomenclature of the splenius the part to the head might be named transversalis capitis, and the yiart to the neck transversalis colli, as at yiresent. 364 DISSECTION OF THE BACK. The transversali s colli bends back the neck if the muscles of both sides contract together; or laterally towards its own side, if only one is used. The trachelo-mastoideus will extend the head in concert with its fellow ; or by itself will turn the face to its own side, and then help to approximate the head to the shoulder. The cOMPLExus (tig. 118, ®) is internal to the prolongations from the longissimus dorsi, and converges towards its fellow of the opposite side at Fig. 118. Dissection of the Muscles underneath the Splenius. A. Longus colli. B. Transversalis colli, c Trachelo-mastoid. D. Coinplexus. F. Splenius capitis, cut. Q. Splenius colli, cut. H. Semispinalis dorsi. o. Occipital artery. I. Great occipital nerve. 2. Exterual piece of the second nerve. 3. Outer piece of the third nerve. the occipital bone. Narrow at its lower end, the muscle arises by ten- dinous pieces from the transverse ])rocesses of tlie upper six dorsal verte- bra% from the spine of the last cervical, and from tlie articular processes of tlie cervical vertebra? as high as tlie third. The fleshy fibres pass up- wards to be inserted into an impression between the curved lines of the os occipitis, Avhich reaches outwards nearly two inches from the occipital crest towards the trachelo-mastoideus. The inner jiart of the coinplexus having two fleshy bellies with an in- tervening tendon, is described often as a separate muscle with the name biventer cei'vicis. POSTERIOR CERVICAL NERVES. 365 The complexiis is concealed by the splenis and trapezius : and the cuta- neous surface is marked by a tendinous cross intersection towards the upper end. Two or three of the cervical nerves perforate it. Along the inner side is the semispinalis muscle, with the ligamentum nuchas. Be- neath it are the small recti and obliqui muscles, the semispinalis, and the cervical nerves and vessels. Action. Both muscles will move the head directly back. One will draw the occiput down and back towards its own side. Dissection of vessels and nerves (fig. 110). In the neck the nerves and vessels will be brought into view by detaching the complexus from the occipital bone and the spine of the seventh vertebra, and throwing it out- wards carefully from the subjacent parts. Beneath the muscle is a dense fascia, in which are contained the ramifications of the cervical nerves, and the deep cervical and other vessels. Each nerve except the first divides into an inner and an outer piece. Dissect out first the inner pieces of the seven lowest, which lie partly over and partly beneath the fibres of the semispinalis muscle (g). The exter- nal pieces (^) are very small ; they are given off between the transverse processes close to where the trunks ap[)e^r ; they are to be looked for outside the complexus, and enter the muscles prolonged from the erector spin^e. The first or suboccipital is the most difficult of the set to find : this little nerve is a short trunk, which is contained in the interval between the small recti and obliqui muscles near the head ; it will be best found by looking for the small twigs furnished by it to the muscles around. The deep cervical artery is met with on the semispinalis muscle ; a part of the vertebral artery will be found in contact with the suboccipital nerve ; and the occipital artery will be seen crossing the occipital bone. * Opposite the thorax the dorsal nerves and vessels will be readily dis- played on the inner side of the longissimus dorsi muscle, on the removal of a little fatty tissue from between the transverse processes. External and internal pieces are to be traced from each nerve and vessel into the muscles ; some of the former have been seen in the interval between the ilio-costalis and the longissimus dorsi. * The two pieces of the lumbar nerves and vessels will be found in the same line as the dorsal ; but the inner set are the most difficult to be dis- covered. * The small sacral nerves are placed beneath the multifidus spinoe, and will be dissected after the examination of that muscle (p. 372). * Posterior Primary Branches of the Spinal Nerves. The spinal nerves, with a few exceptions in the cervical and sacral groups, bifurcate in the intervertebral foramina into anterior and posterior primary branches (p. 165). The posterior supply the integuments and the muscles of the back, and are now to be learnt. In the neck. The posterior primary branches of the cervical nerves are eight in number, and issue between the transverse processes ; but those of the first and second, which begin on the neural arches of the atlas and axis, cross those arches. All, except the first, divide into internal and external pieces. The external pieces (fig. 118) are very inconsiderable in size, and end in the splenius, and in the muscles prolonged from the erector spinas. The internal -pieces (fig. 110) are larger than the external; they are directed towards the spinous processes, the three lowest nerves passing beneath the semispinalis, and the four next over that muscle. By the side 366 DISSECTION OF THE BACK. of the spine cutaneous branches are furnished to the neck and the head by the nerves that are superficial to the semispinalis ; these cutaneous offsets ascend to the surface through the splenius, the complexus, and trapezius muscles, and are distributed as before seen (p. 354). In their course to Fig. 119. Deep Dissection of the Back of the Neck. (Illustrations of Dissections.) Muscles : A. Rectus posticus major. B. Rectus posticus minor, c. Obliquus inferior. D. Obliquus superior. E. Splenius capitis. F. Complexus, cut across. G. Semispinalis colli. Arteries ; a. Occipital, and h, its cervical branch, e. Vertebral artery, and d, its cervical bran e. Deep cervical artery of tlie subclavian. Nerves : 1. Suboccipital nerve (posterior branch), 2. Inner piece of the posterior primary branch of the second nerve. 3. Inner piece of the third nerve. 4. Inner piece of the fourih. And the remaining figures point to the inner pieces of the respective nerves. the spine the nerves supply the surrounding muscles, viz., complexus, semispinalis, multitidus spinaB, and interspinales. The cutaneous hranches of the second and third nerves reach the head, and require a separate notice. Tluit of the second nerve (fig. 119, ^), named great occipital, appearing POSTERIOR CERVICAL NERVES. 36T beneath the inferior oblique muscle to which it gives offsets, is directed upwards through the complexus and trapezius to end on the occiput (p. 23). The branch of the third nerve (fig. 119, supplies an offset to the in- teguments of the neck ; and ascending to the head through the trapezius, is distributed to the lower part of the occiput, internal to the great occi- pital nerve. Usually this nerve joins the preceding both beneath, and superficial to the trapezius. The ^posterior primary branch of the suboccipital or first spinal nerve (fig. 119, is very short, and appears in the interval between the recti and obliqui muscles. In passing from the spinal canal it is placed between the arch of the atlas and the vertebral artery. The following branches radiate from its extremity: — One enters the under surface of the complexus near the cranial attach- ment. A slender branch is furnished to each of the small muscles bound- ing the space in which the nerve is contained, viz., the rectus major and minor, and the superior and inferior oblique : the offset to the last muscle joins the inner branch of the second cervical nerve. Occasionally this nerve gives a cutaneous branch to the occiput. Posterior cervical plexus. Sometimes there is an intercommunication between the suboccipital nerve and tiie internal pieces of the next two cervical nerves beneath the complexus ; this forms the posterior cervical plexus of M. Cruveilhier. * In the dorsal region. The posterior primary branches of the dorsal nerves are twelve in number, and appear between the transverse processes. Each divides into an internal and an external piece ; and these are distri- buted after the same plan as in the neck. * The external pieces increase in size from the first to the last, and are differently distributed above and below. The upper six or eight pass be- neath the longissimus and its cervical prolongation, as far as the interval between the longissimus and the ilio-costalis, and end by supplying these muscles and the levatores costarum. The lower six or four have a similar arrangement and distribution with respect to muscles ; but, after reaching the interval between the ilio-costalis and the longissimus dorsi, they are continued to the surface through the serratus and latissimus muscles, nearly in a line with the angles of the ribs. * The internal pieces decrease in size from above downwards, and are directed inwards between the semispinalis dorsi and multifidus spin* mus- cles ; offsets are supplied to the muscles between which they are placed. The upper six become cutaneous along the sides of tlie spinous processes by perforating the seratus, rliornboideus, and trapezius. The lower six are small in size, and end in the multifidus spin* muscle. * In the loins. The posterior ])rimary branches of the lumbar nerves, five in number, appear between the erector and multifidus spin*. In their mode of dividing and general arrangement they resemble the dorsal nerves. Cutaneous offsets are furnished by the external set of branches. * The externcd pieces enter the erector spin*, and supply it and the small intertransverse muscles. The first three pierce the erector spin*, and become cutaneous after perforating the aponeurosis of the latissimus. The branch of the last nerve is connected with the corresponding part of the first sacral nerve by an offset near the bones. * The internal pieces are furnished to the multifidus spin* muscle. Near their origin they are difficult to find, in consequence of being con- tained in grooves on the articular processes. 368 DISSECTION OF THE BACK. * Vessels in the back. The vessels now dissected are the occipital and the deep cervical ; part of the vertebral ; and the posterior branches of the intercostal and the lumbar arterids of the aorta. Veins accompany the arteries for the most part. In the neck. The vessels in the neck are the occipital, the vertebral, and the deep cervical. The occipital artery (fig. 119, «) courses along the occipital bone. Ap- pearing from beneath the digastric muscle, the vessel is directed back- wards beneath the sterno-mastoideus, the splenius, and sometimes the trachelo-mastoideus, but over tjie obliquus superior and complexus muscles. Near the middle line it perforates the trapezius, and ascends to the occi- put, on which it is divStributed (p. 21). It supplies the surrounding muscles, and furnishes the following branch to tlie neck : — The cervical branch {h) (ram. princeps cervicalis) distributes twigs to the under part of the trapezius, and })assing beneath the complexus, anas- tomoses with the vertebral and deep cervical arteries. Tlie vertebral artery (fig. 119, c) lies on the neural arch of the first vertebra, behind the articulating process, and appears in the interval be- tween the straight and oblique muscles. Beneath it is the suboccipital nerve. Small branches are given to the surrounding parts, and to anasto- mose with the contiguous arteries. The deep cervical artery (fig. 119, e) is a branch of the superior inter- costal (p. 78), and resembles the posterior branches of the other inter- costal ai'teries. Passing back between the transverse process of the last cervical vertebra and the neck of the first rib, it ascends between the com- plexus and semispinalis muscles, as high as the upper border of the latter, and anastomoses with the cervical branch of the occipital artery. The contiguous muscles receive branches from it, and anastomoses are formed between its offsets and those of the vertebral. * h the dorsal region. The posterior branches of the intercostal ves- sels (p. 337) pass back between the vertebrue and the anterior costo-trans- verse ligament, and are divided like the nerves into inner and outer pieces. * The inner branches end in the fleshy mass of the multifidus spinse and semispinalis, and furnish small cutaneous offsets with the nerves. * The external branches cross beneath the longissimus dorsi,and supply it and the ilio-costalis. Like the nerves, the lowest branches of this set are the largest and extend to the surface. As the dorsal branch of the intercostal artery passes by the interverte- bral foramen, it furnishes a small intraspinal artery to the spinal canal. * In the loins. The posterior branches of the lumbar arteries divide, like the intercostal, into internal and external pieces, as soon as they reach the interval between the longissimus dorsi and multifidus spinas. Each gives also a spinal branch to tlie spinal canal. * The internal branches are small, and end in the multifidus spinse muscle. * The external branches supply the erector spinse ; and offse'ts are con- tinued onwards to the integuments with the superficial nerves. Veins. With the deep cervical sirtery is a large vein, vena profunda cervicis^ which communicsites with the occipital and other deep veins in this region, forming the posterior plexus of the neck, and passes forwards witli its artery, between the transverse processes, to join the vertebral vein. RECTI AND OBLIQUr. 869 The occipital vein lies with its artery, and communicates sometimes with the lateral sinus of the skull through the mastoid foramen. The dorsal and Inmhar veins correspond in their branching and distri- bution with the arteries they accompany, and end in the intercostal veins and the vena cava. In contact with the spinous processes and [dates of the vertebrce is a deeper set of veins {dorsi spiyial)^ which anastomose freely together, and open into the veins in the interior of the spinal canal. * Fifth Layer. In this layer are the following small muscles: the recti and obliqui, semispinalis, interspinales, multifidus spinse, and inter- transversales. Dissection. Most of the remaining muscles of the Back are uncovered by the previous dissection. Between the first two vertebrae and the occi- pital bone the small straight and oblique muscles extend. * In the cervical and dorsal regions the semispinalis muscle ap[)ears, with the small interspinales internal to it ; and occupying a corresponding position in the loins, is the multifidus S[)in8e. * Tlie small intertrans verse muscles of the lumbar region will be found by removing the erector spinae. The RECTUS CAPITIS POSTICUS MAJOR (fig. 119, a) is the largest of the muscles between the occipital bone and the first two vertebrai, and arises from the side of the spinous process of the axis. It is inserted into the outer part of the inferior curved line of the occipital bone for about an inch, as well as into the surface below it. The muscle is directed outwards very obliquely, and forms one side of the triangular space which contains the suboccipital nerve and the verte- bral artery. Its upper attachment lies beneath the superior oblique muscle. Action. By the action of both muscles the head will be put backwards. By one rectus the face will be turned to the same side; and after the head has been so rotated, the muscle will assist in extending the head. The RECTUS CAPITIS POSTICUS MINOR (fig. 119, b) is internal to tlie preceding, and is shorter than it. Arising from the neural arch of tlie atlas, the muscle is inserted., close to the middle line, into the inferior curved ridge of the occipital bone, and between this and the foramen magnum. This small muscle is fan-shaped, and is deeper than the rectus major : it covers the ligament between the atlas and the occipital bone. The two small recti muscles correspond with the inter-spinales between the other vertebrse. Action. Both muscles, or one, will have the same use, viz., to approach the occiput to the atlas. The OBLiQuus INFERIOR (fig. 119, c) slants between the first two vertebrae. It arises from the spinous process of the axis, external to the rectus major muscle, and is inserted into the tip of the transverse pro- cesses of the atlas. Action. One muscle turns the face to the same side by rotating the atlas on the axis. If both muscles act at the same time they will assist in keeping the head straight. The OBLIQUUS SUPERIOR (fig. 119, d) takes origin from the upper part of the transverse process of the atlas, where the preceding muscle termi- nates ; and is directed inwards to be inserted between the curved lines of the occipital bone, near the mastoid process. 24 370 DISSECTION OF THE BACK. This muscle is concealed by the complexus and trachelo-mastoideus, and crosses the vertebral artery. Its insertion is beneath the splenius (e), but above the rectus major muscle. Action. With its fellow the upper oblique will assist in carrying back- wards the head. By the action of one muscle the occiput will be inclined backwards to the same side. The SEMispiNALis (fig. 119, g) occupies the vertebral groove in the dorsal and cervical regions, and extends from the transverse and articular j)rocesses to the spines of the vertebrae ; it is undivided at the outer, but bifurcated at the inner attachment. It arises externally from the trans- verse processes of the ten upper dorsal vertebrae, and from the articular processes of the four lower cervical ; and it is inserted by two pieces, as below : — The lower piece, sernispinalis dorsi, is inserted into the spinous processes of the upper four dorsal and the last two cervical vertebrae. The upper piece, semispinalis colli., is inserted into the spines of the cervical vertebrae above the attachment of the semispinalis dorsi, the atlas not receiving any slip. The semispinalis muscle is covered by the complexus, and the deep cer- vical artery. Some of the cervical nerves are superficial, and others beneath it. To its inner side is the multifidus spinae muscle. Action. The muscles of both sides acting together will extend the spine. One muscle will rotate the cervical and dorsal parts of the spine, so as to turn the face to the opposite side. * The INTERSPINAL MUSCLES are placed, as their name expresses : they are arranged in pairs, one on each side of the interspiiious ligament ; and they are best seen in the neck and loins. In the cervical region the muscles are absent from the interval between the first two vertebrae. They are small round bundles, and are attached above and below to the bifurcated apices of the spines. * In the dorsal region the muscles are rudimentary ; they exist between the first two, and the lowest two pair of spinous processes, and between the last dorsal and the first lumbar vertebra. * In the lumbar region they are thin flat muscles, which reach the length of the spines. Action. By the approximation of the spinous processes these small muscles will help in extending the spine. Necessarily the movement of each pair is very slight, but the aggregate of all would amount to percep- tible motion. * The INTERTRANSVERSE MUSCLES lie between the transverse pro- cesses of the vertebrae ; but only those in the loins and the back are now dissected. In the neck they are double, like the interspinal muscles of the same vertebrae (p. 165). * In the dorsal region they are single rounded bundles, and are found only between the lower processes : their number varies from three to six. * In the lumbar region the anterior set are four thin and fieshy planes. The posterior set are rounded bundles, which are attached to the accessory points at the roots of the transverse processes : these have been named inter accessorii. Action. The small intertransversales help to incline laterally tlie spine by approximating the transverse processes ; the motion between a single 371 MULTIFIDUS SPIN^.. pair of bones would be scarcely appreciable, as in the case ot the inter- spinales. Dissection. The multifidus spinre muscle, which fills the hollow by the side of the spinous processes, may be now dissected. Tlie upper part of the muscle is to be prepared and learnt by the dissector of the head and neck. It will be laid bare by cutting througli the insertion of tlie semi- spinalis, and everting tliis. * Over tlie sacrum the thick aponeurosis covering the multifidus and the erector spime must be turned aside. In the dorsal region the muscle will appear on detacliing, and drawing the semispinalis from the spines. * The MULTIFIDUS spinye muscle extends from the sacrum to tlie second vertebra, and is much larger towards the pelvis than in the neck. On the back of' the sacrum it takes origin between the central and ex- ternal row of processes, as low as the fourth aperture ; from the inner surl'ace of the iliac spine (posterior superior) of the hip bone; and from the ligaments connecting tliis bone to the sacrum. It is attached differ- ently along its outer edge (origin) in the several regions of the spine : — In the loins it arises by large fasciculi from the accessory and the articular processes. In the dorsal region, from the transverse processes. And in the neck, from the articular processes of the five lower vertebrae. From these attachments the fibres are directed obliquely inwards, some extend- ing more than the length of one vertebra to be inserted into the spines and the neural arches of the vertebrie from the second cervical to the third sacral. This muscle fills chiefly the vertebral groove, and is concealed by the erector spinag and the semispinalis. The internal branches of the vessels and nerves in the back lie along its outer border. The small muscles de- scribed below may be said to be parts of the multifidus. Action. By the use of the muscle of both sides, the spinal column can be extended ; and by the contraction of one, the spine will be rotated in the dorsal region and the neck, the face being turned to the opposite side. * Rotatores dorsi (Theile). These are eleven small muscles beneath the multifidus spinae in the dorsal region, and are separated from that muscle by fine areolar tissue. Each is attached inferiorly to the tip and upper edge of a transverse process, and superiorly to the lower border of the neural arch of the vertebra next above. The first springs from the trans- verse process of the second vertebra. Action. These small rotators will assist the larger muscle (multifidus) in turning the trunk to the opposite side. * The aponeurosis common to the multifidus and erector spinae is fixed firmly to the surrounding bones, and furnishes attachment to the muscu- lar fibres. In the middle line it is united with the spines of the lower lumbar vertebrae and sacrum. On the outer side it is attached to the pos- terior part of the iliac crest, and to the outer row of tubercles on the back of the sacrum, being connected at the last spot with the great sacro-sciatic ligament. Above, it is continued some way on the surface of the erector spinae, but further on the longissimus dorsi than the ilio-costalis. Below, the latissimus dorsi and the vertebral aponeurosis blend with its cutaneous surface (p. 360). * Dissection (fig. 120). To find the branches of the sacral nerves, it will be necessary to remove the part of the multifidus spinae which covers the sacrum. The first three are split into two each : their external pieces will be found readily on the great sacro-sciatic ligament, from which they 872 DISSECTION OF THE BACK. may be traced inwards ; tlie inner branches are very slender and difficult to be recognized. The lowest two nerves are very small, and are to be sought on the back of the sacrum, below the attachment of the multifidus spinse. They are not bifurcated like the others, but unite together, and with the coccygeal nerve in loops. The fourth comes through a sacral aperture, the fifth between the sacrum and coccyx ; and the coccygeal is still lower. Sacral Nerves (fig. 120) — The posterior primary branches of the sacral nerves are five in number. Four issue from the spinal canal by the apertures in the back of the sacrum, and the fifth between the sacrum and the coccyx. The first three have the common division into inner and outer pieces, like the other spinal nerves ; but the last two are undivided. * The^r^^ three nerves are covered by the multifidus spinae; and divide regularly. The inner pieces {^) are distributed to the multifidus ; and the last of this set is very fine. The outer pieces (^) are larger, and have communicating offsets from one to another on the back of the sacrum : further, the branch of the first Fig. 120. Muscles : A. Multifidus spina3, and B. Erector spinse ; both cut. c. Gluteus maximus detached from its origin, and thrown down. D. Great sacro-sciatic ligament. Nerves : 5 1. Last lumbar. 1 /S to 5 /S, the five sacral nerves issuing from the sacrum. 1 c. The coccygeal nerve, escaping by the opening of the sacral canal. 1. Internal offsets of the last lumhar and first three sacral (these are too large in the cut) : and 2. External offsets of the same nerves. 3. Anterior primary branch, and 4. Posterior of the coccygeal nerve. 5. The nerve derived from the anterior primary branches of the lower sacral nerves, which pierces the sacro-sciatic ligament. Dissection of the Sacral Nerves (Lond. Med. Gazette, 1843). nerve is conneeted with the corresponding part of the last lumbar ; and the branch of the third joins in a similar manner the sacral nerve next below. After this looping they jiass outwards to the surface of the great sacro-sciatic ligament, where they join a second time, and become cuta- neous. (Dissection of the Buttock.) * Last two nerves (4 N and 5 S). These nerves, which are below the multifidus, are much smaller than the jireceding, and want the regular branching of the others : they are conneeted with each other and the coc- LEVATORES COSTARUM MUSCLES. 873 cygeal nerve by loops on the back of the sacrum. A few filaments are distributed to the back of the sacrum and the coccyx. Coccygeal nerve (1 c). Its posterior primary branch issues through the lower aperture of the si)inal canal, and a[)pears by the side of the coccyx. It is joined by a loop from the last sacral nerve, and ends on the posterior surface of the coccyx. * Sacral Arteries. Small branches leave the spinal canal with the sacral nerves ; they sup[)ly the muscular mass of the erector spinie, and anastomose with branches on the back of the sacrum from the gluteal and sciatic arteries. * Dissection. The examination of the posterior part of the wall of the thorax may be made before the body is again turned. By removing, oppo- site the ribs, the ilio costalis and longissimus dorsi, the small levatores cos- tarum will be uncovered. The hinder part of the external intercostal muscle will be denuded at the same time. * The LEVATORES COSTARUM are twelve small fan-shaped muscles, which are connected with the hinder part of the ribs. Placli, except the first, arises from the apex and lower border of the transverse process of a dorsal vertebra ; and is inserted., the fibres spreading out, into the upper border of the rib beneath, from the tubercle to the angle. The muscles increase in size from above down, and their fibres have the same direction as the external intercostal layer. The first is fixed above to the transverse process of the last cervical vertebra,- and below to the outer border of the first rib. Some of the four lower muscles are continued beyond one rib to that next succeeding : these longer slips have been named levatores longiores costarum. Action. The muscles raise the hinder part of the ribs, as the name sig- nifies, and the lowermost draw the bones somewhat back. * The external intercostal muscle is continued backwards along the ribs as far as the tubercle, and is overlaid by the elevator muscle. Beneath the muscle are the intercostal nerve and artery. Dissection. To trace the anterior and posterior primary branches of the dorsal nerves to their common trunk, the elevator of the rib and the ex- ternal intercostal muscle are to be cut through in one or more spaces. The intercostal artery with its posterior branch is laid bare by this proceeding. * The dorsal nerves split in the intervertebral foramina into anterior and posterior primary branches. * TXxo, 'posterior branches are directed backwards, internal to the anterior costo-transverse ligament, and have been examined (p. 367). The anterior., named intercostal, is continued between the ribs to the front of the chest : its anatomy is learnt in the dissection of the thorax (p. 343). ^ The intercostal artery has an almost exact correspondence with the dorsal nerve in its branching and distribution. 374 DISSECTION OF THE SPINAL CORD. CHAPTER YI. THE SPINAL CORD AND ITS MEMBRANES. The spinal cord (medulla spinalis) gives origin to the spinal nerves, and is lodged in the osseous canal formed by the bodies and neural arches of the vertebrae. It is invested by prolongations of the membranes of the brain, which form sheaths around and su[)port it. Dissection. After all the muscles have been taken from the arches and spines of the vertebrae, the spinal canal is to be opened by sawing through the neural arches, on each side, close to the articular processes ; and the cuts of the saw should extend to the lower end of the sacrum, but not higher in the neck than the fourth cervical vertebra. As it is difficult to use the saw in the hollow of the lumbar region, a chisel and a mallet will be found useful to complete the division of the vertebral arches. The tube of the dura mater is covered by some veins and fat ; and by a loose areolar tissue containing fluid sometimes, especially at the lower part. Tlie fat may be scraped away witli the handle of the scalpel ; and the lateral prolongations of the membrane through the intervertebral foramina are to be defined. Membranes of the Cord (fig. 122). Three membranes, like those on the brain, surround the cord, viz., an external tube of dura mater, an internal sheath of pia mater, and an intervening arachnoid or serous covering. The dura mater (a) forms a strong tube, and is continuous with the membrane lining the interior of the skull. It forms a loose sheath along the spinal canal, as far as the second or third piece of the sacrum (fig. 121) ; but beyond that point it is continued by a slender impervious cord to the back of the coccyx (fig. 121, d). Tlie capacity of the sheath is greater than is needed for the contents ; and its size is larger in the neck and loins than in the back. On the outer aspect the dura mater is smooth, when a comparison is made between it and the part in the skull, for it does not act as a perios- teum to the hones. Between it and the osseous surfaces are some vessels and fat ; and it is connected to the posterior common ligament of the ver- tebra by a few fibrous bands. On each side the dura mater sends offsets along the spinal nerves in the intervertebral foramina ; and these several offsets become gradually longer interiorly (fig. 121), where they form tubes which enclose the sacral nerves, and lie for some distance within the spinal canal. In the midst of the tubes, below, is the slender impervious cord (/>), which blends Mutli the pei-iosteum covering the back of the coccyx. Dissection. To remove the spinal cord with the sheath of the dura jnater from the body, the lateral })rocesses in the intervertebral apertures nre to be cut ; and one or two of them in the dorsal region sliould be fol- lowed outwards beyond tlie intervertebral Ibramen by cutting away the surrounding bone. The central prolongation may be now detached from SPINAL DURA MATER 375 the coccyx ; and the cord and its membranes are to be divided opposite the lower cervical vertebrne, and to be removed by cutting the bands tliat attach the dura mater to the posterior ligament of the bodies of the ver- tebra. When the cord is taken out, [dace the anterior surface uppermost with the lateral offsets widely separated. To show the arachnoid covering, the dura mater is to be slit along the middle as far as the small terminal fibrous cord before referred to; but the membrane is to be raised whilst it is being cut through, so tliat the loose arachnoid on the cord may not be injured. Lastly, fasten back the dura mater with pins. Fig. 121. Lowkr End of the Dura Mater, with its Centrai. and Lateral Processes. (Mu- seum University College, Loudon.) а. Large sheath of the dura mater. б. Central fibrous hand fixing it to the coc- cyx. The lateral offsets encasing the last two lumbar, and the five sacral nerves, with the coccygeal nerve, are also shown. Each nerve is marked by the numeral, and the first letter of its name. Fig. 122. View of the Membranes of the Spinal Cord. а. Dura mater cut open and reflected. б. Small part of the translucent arachnoid, left. h. Pia mater closely investing the spinal cord. c. Idgamentum denticulatum on the side of the cord, shown by cutting through the ante- rior roots of the nerves. d. Processes joining it to the dura mater. g. Anterior spinal artery and the fibrous band (linea splendens) on the cord. e. Anterior roots of the nerves, cut. /. Posterior, each entering a separate hole in the dura mater. The arachnoid membrane (fig. 122, b) is the thin serous covering of the cord which is immediately beneath the dura mater. Like the correspond- ing membrane in the skull, it invests the spinal cord and lines the dura mater, and consists thus of a visceral and a parietal part. 376 DISSECTION OF THE SPINAL CORD. The outer or 'parietal part is inseparably joined to the inner surface of the dura mater, and gives to that membrane a shining appearance^ The inner or visceral layer surrounds the cord loosely, vSO as to leave a considerable interval between the two (sub-arachnoid space). At the lower part of the S[)inal canal the loose sheath is largest, and envelops the mass of nerves forming the cauda equina. As the different spinal nerves extend to the intervertebral foramina, they receive loose tubes from the arachnoid, but lose the same when they perforate the dura mater. Dissection. The sub-arachnoid space may be made evident by placing the handle of the scalpel beneath the visceral layer ; or by putting a piece of the cord in water, with the posterior aspect uppermost, and blowing air beneath the serous membrane. The suh -arachnoid space separates the loose or visceral part of the arachnoid membrane, from the spinal cord invested by pia mater. Larger at the lower than the upper part of the spinal canal it contains a special daid — cerehro-spinal ; and it communicates with the cavity in the interior of the brain by an aperture in the fourth ventricle. Crossing the space, at’^the posterior part of the cord, are bundles of fibrous tissue, which are most marked in the neck. In the space are contained the serrations of the ligamentum denticulatum, and the roots of the spinal nerves, with some vessels. Dissection. For the purpose of seeing the next covering of the cord with the ligamentum denticulatum, the araclinoid membrane is to be taken away ; and two or three of the anterior roots of the upper dorsal nerves may be cut through and reflected, as in the wood-cut 122. The pia 'mater (fig. 122, h) is much less vascular on the spinal cord than on the brain. Thicker and more fibrous in its nature, the membrane closely surrounds the cord with a sheath, and sends a thin prolongation into the anterior median fissure ; it furnishes coverings to the roots of the spinal nerves. The outer surface of the pia mater is rough. Along the front is a cen- tral, anterior fibrous band (linea splendens, Haller) ; and on each side another fibrous band, the ligamentum denticulatum, is attached to it. Scattered through the membrane are branched pigment cells, which give a dark appearance in tlie cervical region. Where the medulla spinalis ceases, viz., about the lower part of the body of the first lumbar vertebra, the tube of the pia mater is suddenly reduced in size, and has the appearance of a round fibrous cord (fig. 124, h). This cord-like part (filum terminale) is provided with nervous sub- stance above ; and blends, below, with the central impervious prolongation of the dura mater. It serves to fix the lower end of the medulla spinalis, and has been named, from that circumstance, the central ligament of the cord. A vein and artery accompany this fibrous piece, and distinguish it from the surrounding nerves. The ligamentum denticulatum (fig. 122, c) is the white, fibrous toothed band, on each side of the spinal cord. It is named from its serrated ap- pearance ; and it has the same structure as the dura mater, except that it wants an epithelial covering. Situate between the anterior and posterior roots of the nerves, the band reaches upwards to the medulla oblongata, and ends inferiorly on the > According to the opinion of Kolliker, the arachnoid membrane is a simple tube corresponding with the visceral layer in the text. SPINAL NERVES. 377 lower pointed extremity of the cord. Internally it is united to the pia mater. Externally it ends in a series of triangular or tooth-like projec- tions (c/), which are fixed at intervals into the dura mater, each being about midway between the apertures of the roots of the spinal nerves. There are twenty or twenty-one denticulations ; of which the first is at- tached to the dura mater opposite the margin of the occipital foramen, and the last, opposite the twelfth dorsal, or the first lumbar vertebra. This fibrous band supports the spinal cord, and has been called a liga- ment from that circumstance. Vessels and nerves of the membranes. The dura mater of the cord has but few vessels in comparison with that in the skull, for its office is differ- ent. Nerves are said to be furnished to it from offsets on the vessels sup- plying the cord. The arachnoid is sparingly supplied with vessels like serous membranes in general ; and proof of its containing nerves, in man, is yet wanting. The fia mater has a network of vessels in its substance, though this is less marked than in the part on the brain ; and from them offsets enter the cord. In the membrane are many nerves, derived from the sympa- thetic. Dissection. The arachnoid membrane is to be taken from the fibrils of the roots of the nerves on one side ; and the roots are to be traced out- wards to their transmission through two apertures in the dura mater for each nerve. One of the offsets of the dura mater, which has been cut of some length, is to be laid open to show the contained ganglion. The student should define one ganglion, showing its bifid condition at the inner end (fig. 123, ®), and should trace a bundle of threads of the posterior root into each point. The anterior root, consisting of two bundles of threads, is to be followed over the ganglion to its union with the posterior beyond the ganglion. Spinal Nerves. There are thirty-one pairs of spinal nerves; and each nerve is constructed by the blending of two roots (anterior and pos- terior) in the intervertebral foramen (fig. 123). They are divided into groups corresponding with the regional subdi- visions of the spinal column, viz., cervical, dorsal, lumbar, sacral, and coccygeal. In each group the nerves are the same in number as the ver- tebrie, except in the cervical region of the spine where they are eight, and in the coccygeal region where there is only one. In consequence of the number of nerves in the neck, exceeding that of the vertebraB, the last is placed below the seventh vertebra ; and the lowest nerve of each group, except the coccygeal, will be below its corresponding vertebra. Each nerve divides into two primary branches, anterior and posterior, the former of these is distributed to the front of the body and the limbs, and the latter is confined to the hinder part of the trunk. Roots op the Nerves (fig. 123). Two roots (anterior and posterior) attach the nerve to the spinal cord ; and these unite together to form a common trunk in the intervertebral foramen. The posterior root is marked by a ganglion, but the anterior root is aganglionic. The posterior or ganglionic roots (fig. 123, 6) surpass in size the an- terior, and are formed by larger and more numerous fibrils. They are attached to the side of the cord between the posterior and lateral columns in a straight line, which they keep even to the last nerve. In their course to the trunk of the nerve the fibrils converge to an aper- 378 DISSECTION OF THE SPINAL CORD. ture in tlie dura mater, opposite the intervertebral foramen ; as they ap- proach that aperture they are collected into two bundles (fig. 123 b, b) which, lying side by side, receive a sheath from the dura mate”, and enter the two points of the intervertebral ganglion. Fig. 123. A. Plan of the origin of a spinal nerve from the spinal cord. a. Anterior root. b. Posterior root. c. Ganglion on the posterior root. d. Anterior primary banch. e. Posterior primary branch of the nerve trunk. B. A drawing to show the arrangement of the nerve-roots, and the form of the ganglion in a lumbar nerve. b. Posterior root gathered into two bundles of threads. c. The ganglion, bifid at the inner end. a. Threads of the anterior root, also gathered into two bundles. The intervertebral ganglion (fig. 123). Each posterior root is provided with a ganglion (c). The ganglia are reddish in color, and oval in shape whilst tliey are surrounded by the dura nniter ; and their size is propor- tioned to that of the root. By means of the previous dissection, the gan- glion may be seen to be bifid at the inner end (fig. 123 b), wliere it is joined hy the bundles of fibrils of the root (J>) ; it might be said to possess two small ganglia, one for each bundle of fibrils, which are blended at their outer ends. Sometimes the first or suboccipital nerv^e is without a ganglion. The anterior or aganglionic roots (fig. 123 a) arise from the side of the spinal cord by filaments which are attached irregularly — not in a straight line, and approach near the middle fissure at the lower end of the cord. Taking the same direction as the posterior root to the intervertebral foramen, the fibrils enter a distinct opening in, and have a separate sheath of the dura mater. In their further course to the trunk of the nerve they are gathered into two hundles (fig. 123, b, o), and pass over the ganglion without joining it. Finally the anterior root blends with the posterior beyond the ganglion, to form the trunk. Characters of the roots. Besides variations in the relative size of the two roots, the following characters are to be noted : — Union of the fbrils. The fibrils of contiguous anterior roots may be intermingled, and the fibrils of tlie neighboring posterior roots may be connected in a like manner ; but the anterior is never mixed with the posterior root. VESSELS OF THE SPINAL CORD. 379 Size of the roots to each other. The posterior root is larger than the an- terior, except in the suboccipital nerve ; and the number of the fibrils is also greater. Further, the postei'ior is proportionally larger in the cervical than in any other group ; in the dorsal nerves there is but a very slight difference in favor of the hinder root. Size of both roots along the cord. Both roots are larger where the nerves for the limbs arise, than at any otl)er part of the cord ; and they are greater in the nerves to the lower than in those to the upper limbs. They are smallest at the lower extremity of the cord. Direction and length of the roots. As the apertures of transmission from the sj)inal canal are not opposite the place of origin of the nerves, the roots must be directed more or less obliquely. This obliquity increases from above down ; for in the upper cervical nerves the roots are horizontal, but in the lumbar and sacral nerves tliey have a vertical direction around the end of tlie medulla spinalis. The appearance of the long fibrils around the end of the cord (fig. 124) resembles the extremity of a horse’s tail, and bears appropriately the term cauda equina. The length of the roots increases in ])roportion to their obliquity. Be- tween the origin and the place of exit of the roots of the lower cervical nerve the increase amounts to the depth of one vertebra : in the lower dorsal nerve it e(iuals the de))th of two vertebrae ; and in the lumbar and sacral nerves each succeeding root becomes a vertebra longer, for the cord does not reach beyond the first lumbar vertebra. Place of union of the roots. Commonly the roots unite as before state in the intervertebral foi'amina ; and the trunk of the nerve bifurcates at the same spot into anterior and posterior primary branches (fig. 123, d and e). But deviations from this arrangement are found at the upper and lower ends of the spinal column in the following nerves. The roots of the first two cervical nerves join on the neural arches of the corresponding vertebrte ; and the anterior and posterior primary branches diverge from tlie trunks in tliat situation. In the sacral nerves the union of the roots takes place within the spinal canal ; and the primary branches of the nerves issue by the apertures in the front and back of the sacrum. The roots of the coccygeal nerve are also united in the spinal canal ; and the anterior and posterior branches of its trunk escape by the lower aper- ture of that canal. Situation of the ganglia. The ganglia are placed commonly in the in- tervertebral foramina, but where the position of those apertures is irregu- lar, as at the upper and lower extremities of the spinal column, they have the following situation : In the first two nerves they lie on the neural arches of the atlas and axis. In the sacral nerves they are contained in the spinal canal. In the coccygeal nerve the ganglion is also within the canal, and about the middle of the long posterior root (Schlemm). Vessels of the Spinal Cord. The arteries on the surface of the cord are anterior and posterior spinal. The anterior spinal ar/er;/ occupies the middle line of the cord beneath the fibrous band before alluded to in that position. It begins by the union of two small branches of the vertebral artery (p. 174) ; and it is continued to the lower part of the cord by a series of anastomotic branches, which are derived from the vertebral and ascending cervical arteries in the neck, and from the intercostal arteries in the Back. Inferiorly it supplies the roots of the nerves forming the cauda equina, and ends on the central 380 DISSECTION OF THE SPINAL CORD. Fiff. 124. fibrous prolongation of the cord. The branches of this artery ramify in the pia mater, some entering the median fissure. The posterior spinal arteries, one on each side, are continued from the upper to the lower part of the cord, behind the roots of the nerves. These vessels are furnished from the same source as the ante- rior, and their continuity is maintained by a series of anostomotic branches, which enter the canal along the spinal nerves. Dividing into small branches, the vessels of opposite sides form a free anostomosis around the pos- terior roots, and some ofisets enter the poste- rior fissure of the cord. The veins of the spinal cord are very tor- tuous and form a plexus on the surface. At intervals larger trunks arise, which accompany the spinal nerves to the intervertebral fora- mina, and end in the veins outside the spinal canal. Near the top of the cord the veins are united into two or more small branches; after communicating with the intraspinal veins, these join in the skull the inferior cerebellar veins, or the inferior petrosal sinuses. The SPINAL CORD (medulla spinalis) is the cylindrical elongated part of the cerebro- spinal centre, which is inclosed within the spinal canal. Invested by the membranes before examined, the medulla occupies about two-thirds of the length of the vertebral canal, and is much smaller than the bony case sur- rounding it. The extent of the spinal cord is from the upper border of the atlas to the lower border of tlie first lumbar vertebra, but its termina- tion interiorly may be a little higher or lower than that spot. In the embryo before the third month the medulla reaches throughout the spinal canal, but it gradually recedes as the surrounding bones enlarge faster than it, until it takes the position it has in the adult. Its length is usually from fifteen to eighteen inches. Superiorly the cord joins the medulla ob- longata ; and inferiorly it becomes pointed, being sometimes marked by one or two swell- ings, and ends in the fibrous prolongation, named the central ligament of the cord or filum terminale (fig. T24, d). The size of the spinal cord is much in- creased where the nerves of the limbs are attached. There are therefore two enlarge- ments on it, viz., cervical and dorsal: the one in the neck reaches from the third cer- Membranes of the Spinal Cord LAID open, to show the lower end of the cord with the filum terminale. a. Dura mater, and 5, the fibrous baud fixing it to the coccyx. c. Pointed lower end of the cord. . d. Filum terminale of the cord. FISSURES OF THE CORD. 381 vical to the first dorsal vertebra ; the other in the Back is smaller, and is on a level with the last dorsal vertebra. In the upper enlargement the greatest thickness is from side to side ; but in the lower swelling the measurement from before back rather exceeds the other. Whilst the pia mater remains on the cord, the anterior surface is dis- tinguished from the posterior by a central fibrous band and the anterior spinal artery ; and by the irregular line of the anterior nerve-roots, which approach the middle towards the lower end. Dissection. For the examination of the structure the student should possess a piece of the medulla which has been hardened in spirit, for the cord which is obtained from the spinal canal at this period, is not fitted for the purpose of dissection. Supposing the pia mater removed from the surface, with the roots of the nerves left on one side, the student will be able to observe the following divisions of the medulla. Fissures of the Cord (fig. 125). On the anterior and posterior aspects of the cord is a median longitudinal cleft — the anterior and poste- rior median fissures, which mark its division into halves ; and along the line of the posterior roots of the nerves, in each half, is another slit — the lateral fissure. Fig. 125. d. The lateral fissure. e. The slight groove between the lateral and the posterior median fissure, which marks the limit of the posterior median column. Columns : a. Antero-lateral. b. Posteriaj-. c. Posterior median. Composition : g. Gray crescent, surrounded by white fibres. h. Gray transverse commissure, and i, canal of (he cord in it. J. Posterior, and k, anterior root of a nerve entering the gray crescent. A Sectiov of the Spinal Cord, TO SHOW ITS Composition, and ITS Divisions. Fissures in the MIDDLE LINE ARE THE ANTERIOR AND Posterior Median — the Anterior beino the wider. The anterior median fissure (fig. 125) is wider than the posterior, and penetrates about one-third of the thickness of the medulla: it is lined by a piece of the pia mater, and is deepest towards the lower end of the cord. White medullary substance lines the fissure; and in the bottom of it the white fibres are transverse, and are separated by apertures for blood- vessels. The posterior median fissure (fig. 125) is not so wide, or so well marked as the anterior; but it is best seen at the upper part of the neck, and in the lower or dorsal enlargement. Vessels of the posterior surface of the cord enter it. The lateral fissure is situate along the line of attacliment of the fibrils of the posterior roots (fig. 125, d). Between the lateral and posterior median fissures is a slight groove on the surface (fig. 125, e). Sometimes a lateral fissure is described along the line of origin of the anterior roots (k), but there is not any cleft in that situation. 382 DISSECTION OF THE SPINAL CORD. Segments of the Cord. Each half of the cord between the median fissures is divided into two parts by the lateral sulcus (fig. 125, c?) : the piece in front of that slit and the posterior roots of the nerves is called the antero-lateral column (a); and the piece behind, the posterior col- umn (b). The antero-lateral column (fig. 125, «) includes rather more than two- thirds of the half of the cord, extending backwards to the posterior roots of the nerves, and gives attachment to the anterior roots. The posterior column (fig. 125, h) is situate between the lateral fissure (c?), with the posterior roots of the nerves, and the central median fissure. Near the median fissure is a slight groove (c), which marks off a slender piece, the posterior median column (c) : this portion is best seen in tiie cervical part of the cord. A central piece, or the commissure of the cord, connects the halves of the medulla, and limits the depth of the median fissures. Different division of the cord. Each half of the cord is sometimes di- vided into three columns — anterior, lateral, and posterior, whose limits are the following : — The anterior reaches from the anterior roots of the nerves to the median fissure in front. The lateral column is limited be- fore and behind by the roots of the nerves. Tlie posterior with its small posterior median segment, is placed between the posterior roots and the median fissure behind. Composition of the Cord (fig. 125). A horizontal section of the medulla shows more distinctly its division into halves, with the commis- sural or connecting piece between them. The same cut demonstrates the existence of a mass of gray matter in the interior, which is arranged in the form of two crescents (one in each half) united by a cross piece, and surrounded by white substance. The commissure (fig. 125, h) consists of two parts, viz., a transverse band of gray matter, with a white stratum in front. The gray transverse band {gray commissure) connects the opposite crescents, and consists of nerve cells, and of transverse nerve fibres de- rived from the halves of the cord and the roots of the nerves. In its centre is the shrunken canal of the spinal cord (fig. 125, g'), which is best seen in the foetus. It reaches the whole length of the me- dulla, and a cross section of the cord shows it as a round spot. Above, it opens on the floor of the fourth ventricle, and below it is continued into the filum terminale. It is lined by a columnar ciliated epithelium, and is obstructed by a granular material near the upper opening (Clarke). The white piece of the commissure is formed partly by fibres of the an- terior column ; and partly by fibrils of the anterior roots of the nerves, which here decussate as they cross from the one half to the other. It is best marked opposite the enlargements on the cord, and is least developed in the dorsal region. The half of tile medulla. In the half of the cord as in the commissure, gray and white portions exist; tlie former is elongated I'rom before back, being crescentic in shape as before said, and is quite surrounded by the latter. » The gray crescent {g) is semilunar in form, with the horns or cornua of the crescent directed towards the roots of the nerves, and the convexity to the middle line (fig. 125). Tlie crescentic masses in the opposite halves of the cord are united by the gray commissure. The posterior cornu is long and slender (fig. 126, ^) and reaches near ORIGIN OF THE NERVES. 383 the fissure along the attachment of the posterior nerve-roots. At its ex- tremity, where it is slightly enlarged, it is incased with a rather transpa- rent stratum of small nerve cells, which has been named substantia (jelati- nosa (fig. 126, ^). The anterior cornu (fig. 126, is shorter and thicker than the other, and projects towards the anterior roots without reaching the surface. Its end has an irregular or zigzag outline. Mr. Clarke describes two special collections of cells, one on the outer and the other on the inner side of tire gray crescent, which extend through the cord below the cervical swelling, and with which the roots of the nerves are connected.^ The inner group, or the posterior vesicular column (fig. 126, ®) is close behind the transverse commissure (^) ; whilst the outer group, or the inter- 1. Posterior cornu (caput cornu, Clarke) of the crescent. 2. Anterior cornu. 3. Casing of the substantia gelatinosa. 4. Central canal of the cord. 5. Transverse commissure. 6. Tractus intermedio-lateralis. 7. Cervix cornu of Clarke, reaching from the anterior points of the substantia gelatinosa to the level of the canal. S. Posterior vesicular column A Eepresrntation of the Gray Substance in the Interior of the Spinal Cord, near the Middle OF THE Dorsal Keuion (Clarke). Fig. 126. mediate tract (®), is placed outside the crescent, about midway from front to back. The first is best marked in the dorsal enlargement, and the last in the upper part of the dorsal region. Above the cervical swelling of the cord only rudiments of those tracts remain ; and the cells in a line with the intermediate tract are traversed by the roots of the spinal accessory nerve. The white substance of the cord is composed chiefly of nerve fibres dis- posed longitudinally in bundles, so as to give passage to intermediate vessels. A framework of very fine areolar tissue extends through the substance of the spinal cord, supporting the fibres and cells : this is continuous with the pia mater on the surface. Modifications of the gray and white substance. The white substance exceeds the gray in quantity in the neck and back ; but it is less abundant in proportion to the gray matter in the lumbar region. The cornua of the gray crescents decrease in length from above down, especially the posterior, and towards the end of the cord they blend in one indented or cruciform mass. Origin of the Nerves. The deep origin of the spinal nerves is un- certain, like that of the cranial nerves, but the fibrils in each root enter the gray matter of the cord (fig. 125). The anterior root (k) traverses the longitudinal fibres of the antero- lateral column in distinct bundles ; and entering the anterior coi-nu of the • Fnrtlier researches on the gray substance of the spinal cord. By J. Lockhart Clarke, F.R.S., Philosoph. Trans, of the Royal Society for 1859. Part i. 384 DISSECTION OF THE SPINAL CORD. gray crescent, it is resolved into three sets of fibres, external, internal, and middle. The outer set penetrate into the antero lateral column. The inner set pass through the anterior column and across the median fissure to the opposite half of the cord, decussating with like fibres of the op])Osite side. The middle set enter the substance of the crescent, and are lost in it and in the cells of the intermediate tract. 'Y\\q posterior root (j) pierces chiefly the posterior column of the cord, and enters the j)CSterior cornu of the crescent : but a few fibres penetrate by the lateral fissure. It terminates in two bundles of fibres. One bundle courses round the outer side of the vesicular column, some fibres enclosing, and others entering it ; and a few fibrils escape into the posterior column of the cord, becoming longitudinal. The second bundle is prolonged into the crescent and the intermediate tract, as well as into the transverse commissure behind the central canal of the cord. Intraspinal Vessels (fig. 127). Arteries supply the cord and its Fig. 127. Intraspinal Arteries in the Loins (Museum of University College, London). a. Branch of the lumbar artery. b. Ascending, and c, its descending offset. d. Offsets to the body of the vertebra on each side. e. Central artery formed by offsets from the lateral loops. Fig. 128. Intraspinal Veins in the Loins. a. Branch to join a lumbar vein. h. Anterior longitudinal vein, one on each side. c. Veins from the bodies of the vertebrae. membranes, and the bodies of the vertebras. The veins form a remark- able plexus within the canal, but this will not be seen unless the veins have been specially injected. The intraspinal arteries (a) are derived from the vessels along the sides and front of the spinal column, viz., from the vertebral and ascending cervical in the neck, from the intercostal in the Back, and from the lum- bar and lateral sacral below. They are distributed after the following plan : — As each artery enters the spinal canal by the intervertebral foramen, it divides into two branches, ujiper and lower. From the point of division the branches are directed, one (6) upwards and the other (c) downwards, INTRASPINAL VESSELS. 385 behind the bodies of the two contiguous vertebrae, and join in anastomotic loops with an offset of the intraspinal artery above and below. And from the loops offsets (d) are furnished to the periosteum and the bodies of the vertebrae. Anastomotic twigs connect tlie arches across the vertebrae. Tlie intraspinal vessels produce also a central longitudinal artery (e), like that on the front of the spinal cord, which lies on the bodies of the vertebrae, and is reinforced at intervals by offsets from the loops. The intraspinal veins (fig. 128) consist of two anterior longitudinal vessels, which extend the whole length of the spinal canal ; of veins inside tlie bodies of the vertebraB ; and of a plexus of veins beneath the neural arches. The anterior longitudinal (a) are close to the bodies of the vertebras, one on each side of the posterior common ligament ; and they are irregu- lar in outline, owing to certain constrictions near the intervertebral fora- mina. They receive opposite the body of each vertebra the veins (c) from that bone ; and through the intervertebral foramina they have branches of communication (a) with the veins outside the spine in the neck, the dorsal region, the loins, and the pelvis. Fei?is of the bodies of the vertehrce. Within the canals in the bodies of the vertebrae are large veins, which join on the front of the bone with veins in that situation. Towards the back of the body they are united in an arch, from which two trunks issue by the large apertures on the poste- rior surface. Escaped from the bone, the trunks diverge to the riglit and left, and open into the longitudinal veins. The posterior spinal veins form a plexus between the dura mater and the arches of the vertebr®. A large vein may be said to lie on each side of the middle line, which joins freely with its fellow, and with the ante- rior longitudinal vein by lateral branches. Off'sets from these vessels are directed through the intervertebral foramina, to end in the veins (a) at the roots of the transverse processes. 2o 386 DISSECTION OF THE PERINEUM. CHAPTER yil. DISSECTION OF THE PERIN.EUM. Section I. PERINiEUM OF THE MALE. Directions. The perinneiim may be allotted with greatest advantage to the dissector of the abdomen ; and its examination should be made first, as the distinctness of many of the ])arts is destroyed soon after death. Before the body is placed in the position suited for the dissection, the student may practise passing the catheter along the urethra. Position of the body. Whilst the body lies on the Back it is to be drawn to the end of the dissecting table, till the buttocks project slightly over the edge ; and a moderately-sized block is to be placed beneath the pelvis, to raise the perinasum to a convenient height. The legs are to be raised and kept out of the way by the following means : After the knees have been bent, and the thighs bent upon the trunk, the limbs are to be fastened with a cord in their raised position. F'or this purpose make one or two turns of the cord around one bent knee (say the right) ; carry the cord beneath the table, and, encircling the opposite limb in tlie same man- ner, fasten it tinally round the riglit knee. When the position has been arranged, let the student raise the scrotum, and place a small piece of cotton wool or tow within the anus, but let him avoid distending the rectum. Superficial limits and marhiny. The perinatal space in the male is limited, on the surface of the body, by the scrotum in Iront, and by the thighs and buttocks on the sides and behind. Tliis region is of a dark color, and is covered with hairs. In the middle line is the aperture of the anus, which is posterior to a line extended from the anterior part of the one ischial tuberosity to the other. In front of the anus the surface is slightly convex over the urethra, and presents a longitudinal prominent line or raphe., wliich divides this part of the space into two halves. Between the anus and the tuberosity of the hi[) bone the surface is somewhat depressed over the hollow of the subjacent ischio-rectal fossa, especially in emaciated bodies. The margin of the anal aperture possesses numerous converging folds, but these are more or less obliterated by the position of the body and the distension of the rectum ; and projecting oftentimes through and around the opening are some dilated veins (luernorrhoids). Deep boundaries. The deep boundaries of the perinmal s[)ace will be ascertained, in the progress of the dissection, to correspond with the infe- rior aperture or the outlet of the pelvis. The limits may be seen on a dry POSTERIOR HALF OF THE SPACE. 38T or prepared pelvis, on which the ligaments remain entire ; and the student sliould trace on the body the individual boundaries with his finger. In front is the arch of the pubes ; and at tlie posterior part is the tip of the coccyx, with the great gluteal muscles. On each side in front is the por- tion of the innominate bone which forms the pubic arch, viz., from the pubes to the ischial tuberosity ; and still further back is the great sacro- sciatic ligament extending from the tuber iscliii to the tip of the coccyx. This region sinks into tlie outlet of the pelvis as far as the recto-vesical fascia, which forms its floor. Form and size. The interval included witliin the boundaries above said has the form of a lozenge, and measures about four inches Irom before backwards, and three inches between the ischial tuberosities. Depth. The depth of the perinieum from the surface to the floor may be said to be generally about three inches at the anus, but this measure- ment varies in different bodies ; and it amounts to about an inch near tlie pubes. Division. A line from the front of the tuberosity of one side to the corresponding point on the other, will divide the perinmal space into two triangular jiarts. The anterior half (urethral) contains the penis and the urethra, with their muscles and vessels and nerves. The posterior half (rectal) is occupied by the lower end of the large intestine, with its mus- cles, etc. POSTERIOR HALF OF THE SPACE. This portion of the perinreal space contains the lower end of the rectum, surrounded by' its elevator muscle and the muscles acting on the anus. The gut does not occupy however the whole of the interval between the pelvic bones ; for on each side is a space, the ischio-rectal fossa, in which is con- tained much loose fat, with the vessels and nerves for the supply of the end of the gut. Dissection (fig. 120). The skin is to be raised from this part of the perinmum by the employment of the following cuts : One is to be made across the perinmum at the front of the anus, and is to be extended rather beyond the ischial tuberosity on each side. A second is to be carried a little behind the tip of the coccyx in the same direction, and for the same distance. The two transverse cuts are to be connected by carrying the knife along the middle and around the anus. The fla})S of skin thus marked out, are to be raised and thrown outwards from the middle line : in detach- ing the skin from tlie margin of the anus, the superficial subcutaneous sphincter muscles may be injured without care, for they are close to the skin, without the intervention of fat. The dissector should trace the sphincter back to the coccyx, and forwards for a short distance beneatli the skin ; and define a fleshy slip at each side in front and behind to the subcutaneous fatty layer. The next step is to bring into view the ischio-rectal hollow between the side of the rectum and the tuberosity of the hip bone. On the left side the fat is to be cleaned out of it without reference to the vessels and nerves, but on the opposite side a special dissection is to be made of them. To take out tlie fat from the left fossa, begin at the outer margin of the sphincter ani, and proceed forwards and backwards. In front the dissec- tion should not extend farther than the anus, whilst behind it should lay bare the margin of the gluteus maximus. On the inner side of the hollow the levator ani (sometimes very pale) is to be dissected. On the outer 388 DISSECTION OF THE PERINEUM. boundary the pudic vessels and nerve should be denuded: they lie in a canal formed by fascia, and at some distance from the surface. On the right side it is not necessary to clean the muscular fibres, when following the vessels and nerves. If the student begins at the outer bor- der of the sphincter, he will find the inferior hsemorrhoidal vessels and nerve, which he may trace outwards to the pudic trunks : some of tlie branches, which join the superficial perin^eal and inferior pudendal nerves, are to be followed forwards. In the posterior angle of the space seek a small ofi’set of the fourth sacral ne’we ; and external to it, one or more branches of the sciatic nerve and vessels turning round the border of ^the gluteus. Near the front of the fossa is a superficial perinaeal artery and nerve (of the pudic) ; and the last, after communicating with the haemor- rhoidal nerve, leaves the fossa. A second perinaeal nerve with a deeper position may be found at the front of the hollow. The iscmo-RECTAL fossa (fig. 129) is the space intervening between the rectum and the ischial part of the innominate bone. It is a somewhat A View of the Dissection of the Rectal half of the Perineum. (Illustrations of Dissections.) Muscles : A. External sphincter. B. Corrugator cutis, only part left, c. Internal sphincter. B. Levator ani. E. Gluteus maximus. Arteries : a. Trunk of the pudic artery. 5. Inferior hsemorrhoidal. c. Branches of the sciatic. Nerves : 1. Inferior hsemorrhoidal. 2. Superficial perinseal. 3. Perinseal branch of the fourth sacral. 4. Small sciatic. conical interval, uncovered by muscle, which is larger behind than before, and diminishes in width as it sinks into the pelvis. Its width is about one inch at the surface; and its depth about two inches at the outer part. It is filled by a soft granular fat. MUSCLES OF ANUS. 389 The inner or longest side of the space is very oblique, and is bounded by the levator ani (d), together with the coccygeus muscle posteriorly; but the outer side is vertical, and is formed by the obturator muscle and the fascia covering it. In front it is limited by the triangular ligament (to be afterwards seen) ; and behind are the great sacro-sciatic ligament, and the largest gluteal muscle. Towards the surface it is covered by the teguments, and is overlaid in part by the gluteus e and the sphincter externus a. Position of vessels. Along the outer wall lie the pudic vessels and nerve (a), which are contained in a tube of fascia ; opposite the ischial tuberosity, they are situate an inch and a half from the surface, but to- wards the fi-ont of the space they approach to about half an inch from the edge of the pubic arch. Crossing tlie centre of the hollow are the inferior hsemorrhoidal vessels and nerves (h ) — branches of the pudic. At the an- terior part, for a short distance, are two superficial perinaeal nerves (f) (of the pudic) ; and at the posterior part is a small branch of the fourth sacral nerve (^), with cutaneous offsets of the sciatic vessels (c) and nerve (^) bending round the gluteus. Into this space the surgeon sinks his knife in the first incisions in the lateral operation of lithotomy ; and as he carries it from before backwards, he will divide the superficial ha^morrhoidal vessels and nerve. Muscles. Connected with the lower end of the rectum are four mus- cles, viz., a fine cuticular muscle, and two sphincters (external and inter- nal) with the levator ani. Corrugator cutis ani^ (fig. 129, ®). This thin subcutaneous layer of involuntary muscle surrounds the anus with radiating fibres. Externally it blends with the subdermic tissue outside the internal sphincter; and in- ternally it enters the anus and ends in the submucous tissue within the sphincter. Action. By the contraction of the fibres the skin is raised into ridges radiating from the anus, sucli as may be seen when that aperture is firmly closed. The EXTERNAL SPHINCTER (fig. 129, ^) (spliinctcr ani externus) is a flat, thin, orbicular muscle, which surrounds the lower part of the rectum. The fibres form ellipses around a central aperture, as in other orbicular muscles. It arises posteriorly by a fibrous band from the back of the coccyx near the tip, and by fleshy fibres on each side from the subcuta- neous fatty layer. Its fibres pass forwards to the anus, where they sepa- rate to encircle that aperture ; and in front they are inserted into the central point of the perinaeum, and into the superficial fascia by a rather wide fleshy slip on each side. The sphincter is close beneath the skin, and conceals partly the levator ani. The outer border projects over the ischio-rectal fossa, and the inner is contiguous to the internal sphincter. Action. The muscle gathers into a roll the skin around the anus, and occludes the anal aperture : by its contraction it makes tense also the cen- tral point of the perinseum. Commonly the fibres are in a state of involuntary slight contraction, but they may be firmly contracted under the influence of the will. The INTERNAL SPHINCTER (fig. 129, ®) (sphincter ani internus) is situate around the extremity of the intestine, internal to the preceding * Illustrations of Dissections, p. 243. Lond. 1865. 390 DISSECTIOX OF THE PERINEUM. muscle, and its edge will be seen by removing the corrugator and the mucous membrane. The fibres of the muscle are pale, fine in texture, quite separate from the surrounding external sphincter, and encircle the lower part of the rectum in the form of a ring about half an inch in depth. The muscle is a thickened band of the involuntary circular fibres of the large intestines, which is not attached to the bone. Action. This sphincter assists the external in closing the anus ; and its contraction is altogether involuntary. The LEVATOR ANi muscle (fig. 129, can be seen only in part; and the external spliincter may be detached from the coccyx, in order that its insertion may be more apparent. The muscle descends from its origin at the inner aspect of the hip bone, and is inserted along the middle line from the coccyx to the central point of the perinieum : — The most posterior fibres are attached to the side of the coccyx ; and between that bone and the rectum the muscles of opposite sides are united in a median tendinous line. The middle fibres are blended with the side of the intestine (rec- tum). And the anterior are joined with the opposite muscle, in front of the rectum, in the central point of the perinaeum. This muscle bounds the ischio-rectal fossa on the inner side, and unites with its fellow to form a fleshy layer, convex downwards, through which the rectum is transmitted. Deeper than the muscle is the recto-vesical fascia. Along the hinder border is })laced the coccygeus. Action. Its action on the rectum is to elevate and invert the lower end of the gut after this has been protruded and everted in the passage of the feces. With the description of the muscle in the pelvis its action on the urethra will be referred to. Arteries (fig. 129). The pudic artery, with its inferior haemorrhoidal brand), and other small oftsets of it and the sciatic, are now visible. The pudic artery (a) is derived from the internal iliac in the pelvis, and ascending to the genital organs, distributes offsets to the perinicum ; one portion will be laid bare in the hinder, and the other in the anterior half of the periniEum. As now seen, the vessel enters the posterior part of the ischio-rectal fossa, and courses forwards along the outer wall at the depth of one inch and a half behind, but of only half an inch at the fore part. It is con- tained in an aponeurotic sheatli which attaches it to the obturator fascia. The usual companion veins lie by its side ; and two nerves accompany it, viz., the trunk of the pudic, and the perimeal branch of the same nerve wliicli is nearer the surface. Its offsets in the posterior half of its course are the following : — The inferior hcemorrhoidal branch (b) arises internal to the iscliial tuberosity ; it sends offsets inwards across the ischio-rectal fossa to the teguments, and the sphincter and levator ani muscles. On the rectum it anastomoses with the upper luemorrlioidal branch, and witli the artery of the opposite side. In a well injected body cutaneous branches may be seen to run forwards to tlie anterior part of the perinieum, and to commu- nicate witli the superficial perimeal branch. Small muscular branches cross the front of the ischio-rectal fossa, and supply tlie anteiior ])art of the levator ani muscle. The branches of the sciatic artery (c) appear on the inner aspect of the gluteus maximus at tlie back of the fossa ; some end in that muscle, and others are continued round its border to the fat. URETHRAL HALF OF THE REGION. 391 Veins accompany the different arteries, and have a like course and ramification : the pudic end in the internal iliac. Nerves (fig. 129). The nerves to be learned in this part of the peri- neum are, the trunk of the pudic and its inferior hemorrhoidal and peri- neal branches ; an offset of the fourth sacral ; and some branches of the small sciatic. The pudic nerve comes from the sacral plexus, and accompanies the artery to the genitals. In the anal half of the perineum it is placed deeper than the artery, and furnishes the two subjoined branches. The inferior hcemorrhoidal branch (1) crosses the ischio-rectal fossa, and reaches the margin of the anus, where it terminates in off'sets to the integument and the S[)hincter muscle. Other cutaneous offsets of the nerve turn forwards over the fossa, and communicate with one of the superficial perinmal nerves, and with the inferior pudendal (of the small sciatic) on the margin of the thigh. The perinceal branch arises about half way along the fossa, and becomes superficial to the bloodvessels. It is larger in size than the continuation of the nerve to the penis, and divides into cutaneous, muscular, and geni- tal offsets. Its two cutaneous offsets (superficial perinceal) may be seen on the right side, where they lie for a short distance in the ischio-rectal fossa. The hcemorrhoidal branch of the fourth sacral nerve (f) reaches the ischio-rectal fossa by piercing the tibres of the levator ani. Appearing in the posterior part of the fossa, near the coccyx, the nerve ends by supply- ing the external sphincter, and the integuments behind the anus. One or two cutaneous branches of the small sciatic nerve (f) turn round the lower border of the gluteus, in their course to the integuments on its surface. ANTERIOR HALF OF THE PERINEAL SPACE. In the anterior part of the perinceal space are lodged the crura of the penis, and the tube of the urethra as it courses from the interior of the ]ielvis to the surface of the body. Placed about midway between the bones, the urethra is supported by the triangular ligament of the perinseum, and by its union with the penis. Muscles are collected around the urethra to aid in the expulsion of the contents of that tube : some of these are superficial to, and some within the triangular ligament. The vessels and nerve lie along the outer side, as in the posterior half, and send inwards offsets. Dissection (fig. 130). To raise the skin from the anterior part of the perinceum, a transverse cut is to be made at the back of the scrotum, and is to be continued for a short distance (two inches) on each thigh. A second incision cdong the middle line will allow the flaps of skin to be re- flected outwards. After the removal of the skin the subcutaneous fat (superficicd fascia) which covers the front of the perinaeal S})ace, is to be blown up by means of a pipe introduced beneath it posteriorly. Each side is to be inflated to demonstrate a partition along the middle line, and a septum between the perinseal space and the thigh which prevents the air passing to the limb. The student is next to cut through the sui)erficial fascia on the left side from the scrotum to the ischio-rectal fossa ; and after reflecting it, and 392 DISSECTION OF THE PERINEUM.. removing loose fatty tissue, its line of attachment to the bones externally, and to the triangular ligament posteriorly, will be brought into view. The septum along the middle line should be also defined. To demonstrate more completely the attachment of this subcutaneous layer to the pubic arch between the perinatal sj)ace and the thigli, it will be necessary to take away from the left limb the fat on the fascia lata, external to the line of the bone. In the fat of the thigh on the right side the student should seek the in- ferior pudendal nerve, which pierces the fascia lata one inch anterior to the tuber iscliii,and about the same distance from the margin of the pubic arch ; and should trace its junction in the fat with the inferior haemor- rhoidal nerve. Afterwards the nerve is to be followed forwards to where it enters beneath .the superficial fascia in the middle line. Fig. 130. Superficial Dissection of the Anterior Half of the Perin^eum. (Illustrations of Dissections.) Muscles : A. Ejacnlator urinse. B. Erector penis. c. Transversalis perinaei. D. Levator ani. E. Gluteus inaximus. G. Crus penis. H. Urethra. Arteries : a. Transverse perinseal. b. Superficial perinseal. c. Brauch of sciatic. Nerves : 1. Inferior hsemorrhoidal. 2 and 3. Superficial perinseal. 4. Inferior pudendal. Tlie snh cutaneous fatty layer or the superficial fascia of the anterior half of the perimeum is continuous with that cf the adjoining regions; and its depth, and the quantity of fat in it, will vary with the condition of tlie body. It resembles the corresponding stratum of the groin and upper part of tlie thigh, in consisting of two difierent portions. One, a subcutaneous fatty part, continuous with that of the rest of the body, which loses its fat towards the scrotum, and obtains there involun- tary muscular fibres. PERINiEAL ARTERY AND NERVES. 393 The other deeper, but more membranous part, is of limited extent, and is connected with the firm subjacent structures. Externally it is fixed to the pubic arch of the hip-bone, outside the line of the crus penis and its muscle, extending as low as the ischial tuberosity. Posteriorly the stratum bends down to join the triangular ligament of the urethra ; but in front it is unattached, and is continued to the scrotum and penis. By means of similar connections of the membrane on both sides, a space is enclosed over the anterior half of the perina^um. ' From its under surface a septum dips downwards in the middle line, and divides posteriorly the subjacent space into two ; but anteriorly this partition is less perfect, or may disap- pear. Air blown beneath the fascia passes forwards to the scrotum ; and this direction is given to it by the deep connections of that membrane with parts around. Should urine be effused beneath the superficial fascia, the fluid will necessarily be directed forwards, like the air, through the scrotum to the penis and the front of the abdomen. Dissection. The superficial vessels and nerves are to be dissected on the right side of the perinneum, by cutting through the superficial fascia in the same manner as on the left side. The long slender artery then visible is the superficial perinreal, which gives a transverse branch near its com- mencement. Two superficial perina?al nerves accompany the artery; and the inferior pudendal nerve is to be traced forwards to the scrotum. Com- munications are to besought between these nerves anteriorly, and between one of the perineeal and the inferior hcemorrhoidal posteriorly ; and all the nerves are to be followed backwards. Arteries (fig. 130). The superficial and transverse perimeal arteries beneath the fascia are branches of the pudic, and are two or three in number. The superjicial perinceal branch (fig. 130, J), arising at the fore part of the ischio-rectal fossa, runs over or under the transverse muscle, and beneath the superficial fascia to the back of the scrotum, where it ends in flexuous branches. As the vessel lies internal to the pubic arch, it sup- plies offsets to the muscles beneath ; and in front it anastomoses with the external or superficial pudic branches of the femoral artery. Sometimes there is a second perinseal branch. The transverse artery of the perinseum (fig. 130, a) arises from the preceding, and is directed transversely to the middle of the perimeal space, where it is distributed to the integuments and the muscles between the urethra and the rectum. It anastomoses with the one of the opposite side. Branches of vei?is accompany the arteries, and open into the trunk of the pudic vein ; those with the superficial perinjeal artery are plexiform at the scrotum. Nerves (fig. 130). There are three cufaneous nerves of the scrotum on each side, viz., inferior pudendal of the small sciatic, and two superficial perinaeal branches of the pudic nerve. The superjicial perinceal nerves., two in number, are named anterior and posterior from their relative position : both arise in the ischio-rectal fossa from the perinaeal branch of the pudic nerve (p. 391). The posterior branch (j is continued forwards, beneath the superficial fascia, with the artery of the same name to the back of the scrotum. Whilst in the fossa the nerve gives inwards an offset to the integuments in front of the anus ; and this communicates with the inferior haemorrhoidal nerve. 394 DISSECTION OF THE PERINEUM. Tlie anterior hranch (■^) passes under the transverse muscle, and accom- panies tlie other to the scrotum. Muscular offsets are furnished by it to the levator ani and the other superficial muscles. The superficial perinreal branches communicate with one another, and the posterior is joined by the inferior pudendal nerve. At the scrotum they are distributed by long slender filaments, which reach as far as the under surface of the penis. In the female these nerves supply the labia pudendi. Other muscular hranches of the pudic will be afterwards examined (p. 399). Tlie inferior pudendal nerve f) is a branch of the small sciatic. It pierces the fascia lata about one inch in front of the ischial tuberosity, and enters beneath the superficial fascia of the perinaeum, to end in the outer and fore parts of the scrotum. Communications take place between this nerve, the inferior ha;morrhoidal, and the posterior of the two superficial perinaial branches. In the female the inferior pudendal nerve is distri- buted to the labium. Dissection. For the display of the muscles, the fatty layer, as well as the vessels and nerves of the left side, must be taken away from the ante- rior half of the perimeal space. Afterwards a thin subjacent aponeurotic layer is to be removed from the muscles. Along the middle line lies the ejaculator urinse ; and in cleaning it the student is to follow two fasciculi of fibres from it on the same side — one in front, the other behind. On the outer part of the space is the erector penis. And behind, passing obliquely between the other two, is the transverse muscle. The student should seek, on the right side, the branches of the two superficial perinaeal nerves to the underlying muscles ; and beneath the transversalis, an offset of the perinaeal branch which supplies the deep muscles and the urethra. Muscles (fig. 130). Superficial to the triangular ligament in the ante- rior half of the perinaeal space, are three muscles, viz., the erector penis, the ejaculator urinae, and the transversalis perimci. Other muscles of the urethra are contained between the layers of the triangular ligament, and will be subsequently seen. Central point of the perinceum. Between the urethra and the rectum is a white fibrous spot, to which this term has been applied. It occupies the middle line, half an inch in front of the anus. In it the muscles acting on the rectum and the urethra are united ; and it serves as a common point of support to the space. The ERECTOR PENIS (fig. 130, ®) is the most external of the three mus- cles, and is narrower at each end than in the middle. It covers the crus penis; and its fibres arfse from the ischial tuberosity farther back than the attachment of the penis, and from the bone on each side of the crus. Su- ])eriorly the muscle is inserted into the inner and outer surfaces of the crus penis. It rests on the root of the penis and the bone. Action. The muscle compresses the crus penis against the subjacent bone, and retards the escape of the blood from that organ by the veins : in tliat way it will contribute to the continuance of distension. The EJACULATOR URIN^ muscle (fig. 130, lies on the urethra. The muscles of opposite sides unite by a median tendon along the middle line and in the central point of the periineum (origin). The fibres are directed outwards, curving around the convexity of the urethra, and give rise to a thin muscle, which has the following insertion: — The most posterior fibres SUPERFICIAL MUSCLES OF URETHRA. 395 are lost on tlie front of the triangular ligament. The anterior fibres, whieli are the longest and best marked, are inserted into tlie penis on its outer aspect before the erector ; and, according to Kobelt,^ send a tendinous expansion over the dorsal vessels of the penis. Whilst the middle or in- tervening fibres turn round the urethra, surrounding it for two inches, and join its fellow by a tendon. The ejaculator muscle covers the bulb and the urethra for three inches in front of the triangular ligament.^ If the muscle be cut through on the right side, and turned off the urethra, the junction with its fellow above that tube will be apparent. Action, The two halves, actino; as one muscle, can diminish tlie urethra, and eject forcibly its contents. During the flow of fluid in micturition the fibres are relaxed, but they come into use at the end of the process, wlien the passage has to be cleared. The action is involuntary in the emission of the semen. The TRANSVERSALS PERiN^i (fig. 130, is a small thin muscle, which lies across the perimeum opposite the base of the triangular ligament. Arising h'om the inner surface of the pubic arch near the ischial tuberosity, it is inserted into the central point of the perimeum with the muscle of the opposite side, and with the sphincter ani and the ejaculator urime. Be- hind this muscle the superficial fascia bends down to join the triangular ligament. Sometimes there is a second small fleshy slip, anterior to the transver- salis, which has been named transversalis alter ; this throws itself into the ejaculator muscle. Action. From the direction of the fibres tlie muscle will draw back- wards the centnil point of the perinjeum, and help to fix it, preparatory to the contraction of the ejaculator. The three muscles above described, when separated from eacli other by the dissection, limit a triangular space, of which the ejaculator urinm forms the inner boundary, the erector penis the outer side, and the trans- versalis ))eriniei muscle the base. In the area of this interval is the trian- gular ligament of the urethra, with the superficial perinoeal vessels and nerves. Should the knife enter the posterior part of this s[)ace during the deeper incisions in the lateral operation of lithotomy, it will divide the transverse muscle and artery, and probably the superficial perimval vessels and nerves. Dissection (fig. 131). For the display of the triangular ligament, the muscles and the crus penis, which are su[)erficial to it, are to be detached in the following way: — On the left side the ejaculator uringe is to be re- moved completely from the front of the ligament, and the erector muscle from the crus of the penis. Next, the crus penis is to be detached from the bone; but this must be done with care so as not to cut the triangular ligament, nor to injure, near the pubes, the terminal branches of the pudic artery and nerve to the penis. On the right side the dissector should trace out beneath the transversalis * Die Miinnlichen und Weibliclien Wollust-Organe, von G. L. Kobelt, 1844. 2 Some of the deeper fibres which immediately surround the bulb, have been described as a separate stratum by Kobelt. These are separated from the sui)er- ficial layer by thin areolar tissue, and join the corresponding part of the other muscle by a small tendon above the urethra. The name compressor heynisphcerium bidbi has been proposed for it by that anatomist. 396 DISSECTION OF THE PERINEUM. the offsets of the perinseal nerve to the deep muscles and the urethra, witli the vessels accompanying them. The TRIANGULAR LIGAMENT OF THE URETHRA (fig. 131, (perinaeal aponeurosis) occupies the anterior part of the pubic arch, and supports the urethral canal. The ligament is triangular in form, with its base below ; and it is about one inch and a half in depth. Fig. 131. Deep Dissection of the Perin^eum. Muscles : A. Erector penis. B. Ejaculator urinae, cut. c. Triangular ligament. B. External sphincter. F. Bulbous part of the urethra. 6. Levator ani. H. Deep transverse, i. Constrictor urethrae. K. Crus penis, cut. (Illustrations of Dissections.) Arteries : a. Pudic, in the triangular ligament. 6. Dorsal of penis. c. Cavernous. d. Deep muscular and urethral branch. Nerves : 1. Pudic trunk. 2. Deep perinaeal or muscular branch. 3. Dorsal of the penis. On each side it is fixed to the pubic arch beneath the crus penis. Its apex is connected with the symphysis pubis. Its base is turned towards the rectum, and is partly attached and partly free; in the middle line it is eonnected with the central point of the periufeum, whilst laterally it is sloped towards the bone, so that it is less deep at the centre than at tlie sides: eonnected with tlie lower border is a thin fascia which covers the surface of the levator ani muscle in the ischio-rectal fossa. Superficial to it are the muscles in the anterior half of the perinaeal space; and the super- ficial fascia is united to it near the lower border. The ligament is comjiosed of two layers of membrane (anterior and pos- terior) which are united below. The posterior layer is derived from the recto-vesical fascia. The anterior is a separate membrane, formed chiefly of transverse fibres, but it is so thin as to allow the vessels and the mus- cular fibres to be seen through it. DEEP MUSCLES OF URETHRA. 397 Perforating the fore part of the ligament, about one inch below the symphysis pubis, is the canal of the urethra, f ; but the margin of the opening giving passage to that tube is blended with the tissue of the cor- pus spongiosum urethroe. About midway between the preceding opening and the symphysis pubis is the aperture for the dorsal vein of the penis ; and external to this, near the bone on each side, the terminal parts of the pudic artery and nerve to the penis {h and 3) perforate the ligament by separate apertures. Between the layers of the ligament are contained the membranous part of the urethra, with its muscles, vessels, and glands ; and the bloodvessels and nerves of the penis. Dissection. The muscles between the layers of the ligament will be reached by cutting through with care, on the left side, the superficial stratum near its attachment to the bone, and raising and turning inwards that piece of membrane. By a little cautious dissection, and the removal of some veins, the following objects will come into view with the under- mentioned position : — Parts between the layers of the ligament. Near the base is a narrow transverse muscle, ii, which is directed to the bulb of the urethra. Higher up, and crossing inwards from behind tlie pubic arch, is the fasci- culus of fibres of the constrictor urethra muscle, i, which surrounds the membranous part of the urethra. And below the urethra are the glands of Cowper. Beneath the bone are the pudic vessels (a) and nerve, the former giving its branch to the bulb, and the latter being deeper in posi- tion ; and below tlie pubes is the sub-pubic ligament. Deeper tlian all, the student will recognize the posterior layer of the ligament, continuous with the recto-vesical fascia, which separates those parts from the cavity of the pelvis. Muscles. The two muscles connected with the membranous part of the urethra are, deep transverse, and constrictor of the urethral passage. The DEEP TRANSVERSE MUSCLE (fig. 131, n) (elevator urethra Santo- rini) is a thin fiat band on a level with the base of the triangular ligament. It arises externally from the pubic arch of the innominate bone, and is directed below the tip of the bulb and the membranous part of the urethra to the middle line, where it joins the muscle of the opposite side, and is inserted into the central point of the perinaBum. The muscle conceals Cowper’s gland, and is frequently placed over the artery of the bulb. The transverse muscle is not always separate from the following. Action. Like the superficial muscle it will fix the central point of the perinaeum. The CONSTRICTOR MUSCLE (fig. 131, (constrictor isthmi urethralis) incloses the membranous part of the urethra, and consists of transverse fibres above and below that tube. The muscle arises by aponeurotic fibres from the pubic arch above the preceding, and from the posterior layer of the triangular ligament, but this attachment is not evident unless it has been dissected from behind. The fibres pass inwards, and separate near the urethra into two layers (fig. 132), of which one (c) passes over, the other (d) under that canal; in the middle line they unite (sometimes by tendon) with the like parts of the muscle of the opposite side. It may be considered a single muscle extending across the perinceum 398 DISSECTIO^^ OF THE PERINEUM. from one lateral attachment to the other, and inclosing the urethra, like the sphincter ani encircles the rectum. Action. The muscles of both sides act as a single sphincter in dimin- ishing the membranous part of the urethra, and ejecting the contents of the tube. Like tlie ejaculator, they are relaxed whilst tlie urine is passing, but the two contract forcibly in expelling the last of that fluid. Involuntary circular fibres within the constrictor muscle surround the urethra from the bulb to the prostate, and form a layer about g^th of an inch thick ; they are not fixed to bone, and are continuous behind with the circular fibres of the prostate. This layer is a portion of the large involuntary muscle, of which the })rostate is chief part, surroundino; the bejxinnin" of the urethra.^ Action. This involuntary layer as- sists in moving forwards the urine and the semen. The glands of Cowper will be found by cutting through the transverse mus- cle. Tliey are situate below the mem- branous part of the urethra, one on each side of the middle line, and close behind the bulb. Each gland is about the size of a pea, and is made up of lobules; and the lobules are composed of small vesicles, which are lined by flattened epithelium. Connected with each is a minute duct, nearly an inch in length, which perforates obliquely the wall of the urethra (corpus spongiosum), and opens into the urethral canal about half an inch in front of the triangular ligament. Its a})erture in the ordinary state does not admit a bristle. In the wall of the duct are unstriated muscular fibres ; and the interior is lined by a columnar epithelium. The nature of the secretion of the gland is not known. These bodies are sometimes so small as to escape detection, and they appear to decrease in size with advancing age. Dissection. The student may complete the examination of the perinaeum by tracing out the j)udic vessels and nerve, and their remuining branches. From the })oint of its division beneath the crus into two branches (dorsal of the [)enis, and cavernous), the artery is to be followed backwards, along the pubic arch of the left side. The pudic nerve will be by the side of, but deeper than the artery. Pudic Arteky (n). Tlie ])osterior half of this artery has been already dissected (p. 300). In the anterior half of the perimeum it ascends be- tween tlie layers of the triangular ligament, and along the pubic arch nearly to the pubes ; there it perforates the su[)erficial part of the liga- ‘ See a jiaper on tlie Arrangement of the Muscular Fibres of the Urethra, in vol. xxxix. 185G, of the Trans, of the Med.-Chir. Society. Fig. 132. The Symphysis Pubis seen from behind WITH PART OF THE URINARY BLADDER ANDTHE Prostate, and with the Tube OF THE Urethra surrounded by the Constrictor Muscle (Santorini). a. Bladder cut open: tlie swelling of the prostate surrounds it in front. h. Constrictor urethrae : — c. Part of the muscle above, and d. Part underneath the urethra. PUDIC ARTERY AND NERVE. 399 ment, and divides into the arteries of the cavernous structure and dorsum of the penis. In this course it is placed beneath the constrictor urethrae, and is accompanied by venm comites and the pudic nerve. Its offsets are subjoined : — a. The artery of the bulb of the urethra is a branch of considerable size, and arises near the base of the triangular ligament. Passing almost transversely inwards between the layers of that ligament, about half an inch from the base, the artery reaches the back of the bulb, and enters the spongy structure. Near the urethra it furnishes a small branch to Cow- per’s gland. The distance of this branch from the base of the ligament will be in- fluenced by its origin near the front or back of the perinatal space. If the vessel arises farther behind than usual, it may be altogether below the ligament, and may cross the front of the ischio-rectal fossa, so as to be liable to be cut in the operation of lithotomy. b. Deep nwscular branches {d). As the artery is about to enter between the layers of the triangular ligament it furnishes one or more branches to the levator ani and sphincter, and fine twigs through the ligament to the constrictor and the urethra. c. The artery of the cavernons structure of the penis (c) (art. corporis cavernosi) is one of the terminal branches of the pudic. At first this small vessel lies between the crus penis and the bone, but it soon enters the ci'us, and ramifies in the cavernous structure of the penis. d. The dorsal artery of the penis (h) is in direction and size the con- tinuation of the })udic ; it runs upwards between the crus and the bone, and reaches the dorsum of the penis by passing through the suspensory ligament. Its distribution with the accompanying nerve is noticed at page 408. It is much smaller in the female than in the male. Accessory pudic artery. In some cases the pudic artery is not large enough to supply the branches above described to the penis and the ure- thra. One or more offsets will be then contributed by an accessory vessel, which leaves the pelvis in front by piercing the triangular ligament. The source of this accessory artery is the internal iliac. The pudic veins., two in number, have the same connections as the artery ; they receive similar branches, except that the dorsal vein of the penis does not join them. The PUDIC NERVE has been examined in the ischio-rectal fossa (p. 391). In the anterior half of the perinmum it is much diminished in size, in con- sequence of the emission of the’ large perinaeal branch, and courses with the artery between the layers of the triangular ligament ; near the pubes it pierces the ligament (fig. 131, ®), and is continued to the dorsum of the penis with the dorsal branch of the pudic artery ; its termination is de- scribed at page 408. The deep muscles and the corpus spongiosum are supplied by the following branch. Perinceal branch (p. 391). Arising in the ischio-rectal fossa it suj)[)lies superficial nerves, and ends near the base of the triangular ligament in deep muscular offsets: some of these (fig. 131, pass beneath the trans- versals, and piercing the triangular ligament, sui)ply the muscles within it. A long slender branch, nerve of the bulb, is distributed like the artery to the spongy structure investing the urethra : its filaments reach some way on the surface before disappearing in the corpus spongiosum ui-ethra^. Parts cut in the lateral operation of lithotomy. This 0 [)eration for stone in the bladder may be divided into three stages, viz., cutting down to the 400 DISSECTION OF THE PERINEUM. urethra, opening the canal, and slitting that tube and the neck of the bladder. In the external incisions the knife is entered in the middle line of the perinoeum, half an inch in front of the anus, and is drawn back- wards on the left side as far as midway between the ischial tuberosity and the anus. The skin and superficial fascia, and the inferior hemorrhoidal vessels and nerve lying across the ischio-rectal fossa, will be cut in this first stage of the operation ; and the transverse perinreal muscle and artery, and, possibly, the superficial perinoeal vessels and nerves, may be divided, if the first incision is begun farther forwards. In the subsequent attempt to reach tlie staff, when the knife is intro- duced into the anterior part of the wound, tlie lower part of the triangular ligament, the deep transverse urethral muscle, and the fore part of the levator ani will be divided ; and when the knife is placed within the groove of the staff, the membranous part of the urethra will be cut, with the muscular fibre about it. Lastly, as the knife is pushed along the staff into the bladder, it incises in its progress the membranous portion of the urethra, part of the prostate with large veins around it, and the neck of the bladder. When the last two parts are being cut, the handle of the knife is to be raised, and the blade depressed ; and the incision is to be made downwards and outwards in the direction of a line from the urethra through the left lateral lobe of the prostate, above the level of the ejaculatory duct. Parts to be avoided. In the first incisions in the ischio-rectal fossa, the rectum may be cut if the knife is turned inwards across the intestine, instead of being kept parallel with it ; and if the gut is not kept out of the way with the fore hnger of the left hand. The pudic vessels on the outer waill of the ischio-rectal fossa can be wounded near the anterior part of the hollow, where they approach the margin of the triangular ligament; but, pos- teriorly, they are securely lodged inside the projection of the tuber ischii. Whilst making the deeper incisions to reacli the staff, the artery of the bulb lies immediately in front of the knife, and will be wounded if the in- cisions are made too far forwards; but the vessel must almost necessarily be cut, when it arises farther back than usual, and crosses the front of the iscliio-rectal fossa in its course to the bulb of the urethra. In the last stage of the operation the neck of the bladder should not be cut to a greater extent than is necessary for the extraction of the stone, lest the recto-vesical fascia separating the perinoeum from the pelvis should be divided, and the abdominal cavity opened. Too large an incision through the prostate may wound also an unusual accessory pudic artery on the side of that body. Directions. When the dissection of the perinoeum is completed, the flaps of skin are to be fastened together, after salt has been used, and the limbs are to be put down for the examination of the abdomen. Section II. PERINiEUM OF THE FEMALE. The perinnsum in tlie female differs from that in the male more in the external form than the internal anatomy. On the surface it has special parts distinguishing it, viz., the aperture of the vagina, and the opening of the vulva with the labia. PERINiEUM OF THE FEMALE. 401 Surface-marking. In the middle line, there are the two apertures of the anus and vulva, which are separated from one another by an interval of about an inch. The anus is situate rather farther back than in tiie male. And the vulva with the labia majora on the sides is placed in the situation of the scrotum of the other sex. Within the vulva at the upper part, is the clitoris, and two small mem- branous folds, labia minora, extend downwards from it. Below the clitoris is the small aperture of the urethra; and still lower. down is the vagina, whose opening is sometimes partly closed by a thin piece of membrane, the hymen. Deep houndaries. The deep boundaries of the perina3um are alike in both sexes; but in the female the outlet of the pelvis is larger than in the male. Fig. 133. The Female Perin;ehm (from D: 1 . Pudic artery. 2. Branch to levator ani. 3. Inferior hseinorrhoidHl artery. 4. Transverse artery. 5. Great labial (superficial perineal) artery. 7. Dorsal artery of clitoris. 8. Artery of bulb. 9. Artery to crus clitoridis. 10. Inferior hsemorrhoidal nerve. 11. Pudic nerve. 12. Muscular branch. 13. Internal superficial perinseal nerve. 14. External superficial perinseal nerve. 1.0. Its junction with — 16. Inferior pudendal nerve. 17. Small sciatic nerve. 18. IS. Dorsal nerve of clitoris. '. Savage’s “Illustrations”). 19. Ilio-inguinal nerve. A. Anus. C. Clitoris. M. Meatus urinarius. L. Great sacro-sciatic ligament. V. Vagina. 0. Coccyx. T. Tuberosity of ischium. a. Gluteus maximus c. Levator ani. d. Superficial transverse muscle. e. Compressor bulbi. g. Erector clitoridis. h. Triangular ligament (cut). 1. Biceps and semi-t,endiuosus. j. Adductor magiius. k. Gracilis. Dissection. The steps of the dissection are much the same in both sexes, and the same description will serve, generally, for the male and female perinaeum. First, the dissection of the ischio-rectal fossa is to be made. After- 26 402 DISSECTION OF THE PERINiEUM. wards the muscles, vessels, and nerves of the posterior half of the perinosal space are to be examined. (See description of the male perinseum, p. 386 to 392.) Next the skin is to be taken from the interior half of the perinseal space, as in the male; and the transverse incision in front is to be made at tlie anterior part of the vulva. The attachments of the superficial fascia are then to be looked to, and the cutaneous vessels and nerves are to be traced beneath it (p. 392 to 394). Superjicial fascia. The description of this fascia in the male will serve for the like part in the female, with these modifications: that in the female it is interrupted in the middle line, and is of less extent, in conse- ({uence of the aperture of the vulva; and that it is continued forwards through the labia majora (the representative of the scrotum) to the in- guinal region. The Muscles of the Female Perineum, Superficial on Right, and Deep on Left Side (from Savage and Luschka). 1. Clitoris. 2. Erector clitoridi.s. 3. Jarjavay’s muscle. 4. Bulb of vagina. 5. Transversus perinsei (reflected). 6. Compressor bulbi (sphincter). 7. Constrictor vaginaj 8. Gland of Bartholin. 9. Deep transversus perinsei. 10. Superficial transversus perinzei. 11. Posterior layer of triangular ligament. 12. Sphincter ani. 13. Tx-iangular ligament. 14. Levator ani. 15. Ischio-perineal ligament. Dissection. Tlie labia and the superficial fascia are to be removed, to .follow the sphincter muscle around the opening of the vagina. Two other muscles are exposed at the same time, viz., the erector clitoridis on the pubic arch, and the transversalis perintni passing across the perinaoum to the central jioint. The SPHINCTER VAGINJ2 is ail orbicular muscle around the orifice of the vagina, and corresponds witli the ejaculator urime in the male. Pos- teriorly it is attached to the-central point of the perinamm, where it mixes with the sphincter ani and transversalis muscles; and its fibres are directed DEEP URETHRAL MUSCLES. 403 forwards on each side of the vagina, to be inserted into the body of the clitoris, and front of the triangular ligament. Action. Like the other orbicular muscles the sphincter diminishes that part of the vagina which it encircles; and it assists in fixing the cen- tral point of the perinaeum. The ERECTOR CLiTORiDis resembles the erector of the penis in the male, though it is much smaller (p. 394). The TRANSVERSALis is similar to the muscle of the same name in the male. The one description will suffice for those muscles in both sexes (p. 395). Dissection. To see the triangular ligament of the urethra, the erector and the crus clitoridis are to be detached from the bone, and the outer fibres of the sphincter vaginae are to be removed. The triangular liganient transmits the urethra, but is not quite so strongly marked as in the male (p. 396); its extent is partly interrupted behind by the large aperture of the vagina. Dissection. By cutting through the superficial layer of the ligament in the same way as in the male (p. 397), the deep muscles, with the pudic vessels and nerve and their branches, will be arrived at. The DEEP TRANSVERSE MUSCLE (depressor urethrae, Santorini) has the same origin externally as in the male (p. 397); and it meets its fellow at the middle line, like the muscle answering to it in the other sex. Santo- rini described the muscle as passing over, instead of below the urethra; hence the name given to it by its discoverer. The CONSTRICTOR MUSCLE of the urethra resembles that of the male in its origin from the pubes, and its disposition around the uretlira (p. 397). Within it is a circular layer of involuntary fibres, as in the other sex. The description of the pudic artery (p. 398) will serve for both sexes, except that the branch in the female, which is the representative of the artery of the bulb in the male, is furnished to the vagina. The terminal branches are much smaller in the female. The pudic nerve has the same peculiarity as the artery with respect to the branch to the vagina, and the smaller size of the terminal part of the nerve on the clitoris. 404 DISSECTION OF THE ABDOMEN. CHAPTEE YIII. DISSECTION OF THE ABDOMEN. Section I. WALL OF THE ABDOMEN. The examination of the abdomen is to proceed as far as the end of vSection III. before the body is turned for the dissection of the Back. Position. The body will be sufficiently raised by blocks beneath the thorax and head for the dissection of the upper limbs and neck, but the dissector should see that the chest is higher than the pelvis. If the ab- domen is flaccid, let it be inflated by an aperture through the umbilicus, but if it is firm, proceed with tlie dissection without blowing it up. Surface-rnarking. On its anterior aspect the abdomen is for the most part convex, especially in fat bodies ; but on the sides, between the ribs and the crista ilii, the surface is somewhat depressed. Along the middle line is a slight groove over the linea alba, which presents about its centre the hollow of the umbilicus. Inferiorly the groove ceases a little above the pelvis in the prominence of the pubes ; and superiorly it subsides below the ensiform cartilage in a hollow named the epigastric fossa. On each side of the middle line is the projection of the rectus muscle, and this is intersected in adult well-formed bodies by two or three transverse lines Underneath the eminence of the pubes the student will be able to recog- nize with his finger the symphysis pubis, and to trace outwards from it the osseous pubic crest which leads to the pubic spinous process. Bather above and to the outside of the pubes, the opening of the external abdomi- nal ring may be felt ; and the prominence of the spermatic cord descend- ing through it to the testicle may be detected. The internal abdominal ring is still to the outer side, though it cannot be recognized on the sur- face with the finger ; but its position may be ascertained by taking a point midway between the symphysis pubis and the crest of the innominate bone, and a little above Poupart’s ligament. If the finger is carried upwards and outwards between the abdomen and the thigh, it will detect the firm band of Poupart’s ligament, and sometimes one or two inguinal glands. Dissection. The recpiisite incisions for raising the skin from the sides and front of the belly are the following : One cut is to extend outwards over the side of the chest from the ensiform cartilage to about midway between the sternum and the spine. A second incision is to be begun in the middle line midway betAveen the umbilicus and the pubes, and to be carried outwards to the iliac crest, and along the crest till it ends opposite the first cut. Lastly, the hinder extremities of the two incisions are to 405 SUPERFICIAL PARTS, HOW SHOWN. be connected along the side of the chest and the belly. The piece of skin thus marked out is to be raised towards the middle line, but is not to be taken away ; and the cutaneous vessels and nerves are to be sought in the fat at the side and middle line of the abdomen. Along the side of the abdomen look for the lateral cutaneous nerves, five or six in number, which issue in a line with the corresponding nerves of the thorax. At first they lie beneath the fat, and divide into two : one offset is to be traced forwards, and the other backwards, with small cuta- neous arteries. On the iliac crest, near the front, is a large branch from the last dorsal nerve ; and usually farther back on the crest, and deeper, is a small brancli of the iliohypogastric nerve. Near the middle line the small anterior cutaneous nerves will be recognized with small arteries; these are uncertain in number and size, and are to followed outwards in the integuments. The piece of skin covering the lower part of the abdomen or the groin is next to be thrown downwards, on botli sides, by an incision along the middle line to the root of the penis. After its reflection the cutaneous vessels and nerves are to be dissected on the right side, and the superfi- cial fascia on the left. To make the necessaiy dissection on the right side, all the fascia super- ficial to the vessels is to be raised in the same manner as the piece of skin. The vessels which will then appear are the superficial pudic internally, the superficial epigastric in the centre, and an offset of the superficial circumflex iliac artery externally. Some inguinal glands lie along the line of the reflected fascia. Two cutaneous nerves are to be sought : one, the ilio-inguinal, comes through the abdominal ring, and descends to the thigh and scrotum ; the other, ilio-hypogastric, appears in the superficial fascia above, and rather outside the abdominal ring. In the examination of the fatty layer on the left side two strata are to be made out, one over and one beneath the vessels. The layer that is superficial to the vessels is to be reflected by means of a transverse cut from the front of the iliac crest, about two inches above Poupart’s liga- ment ; and by a vertical one near the middle line to the pubes. The sub- jacent vessels mark the depth of this layer ; and when these are reached, a flap of the fascia, like that of the skin, is to be thrown towards the thigh. To define ’tlie thinner under stratum, cut it across in the same manner as the other layer, and detach it with the vessels from the tendon of the external oblique muscle. This stratum, like the preceding, is to be traced around the cord to the scrotum ; and as the student follows it downwards, he will find it connected with Poupart’s ligament, and blended with the fascia lata close below that structure. The subcutaneous fat, or the siiperjicial fascia^ is a single layer over the greater part of the abdomen ; but in the groin it is divided into a sub- cutaneous and a deeper stratum by the vessels and the glands. The snhcutcmeous layer contains fat, and varies therefore in appear- ance and thickness in different bodies ; for it is sometimes divisible into strata, whilst at others it is very thin, and somewhat membranous near the thigh. It is continuous with the fatty covering of the thigh and ab- domen ; and when traced to the limb, it is separated from Poupart’s liga- ment beneath by the superficial vessels and glands. Internally it is con- tinued to the penis and scrotum, where it changes its adipose tissue for involuntary muscular fibre ; and after investing the testicle, it is prolonged to the perinaeum. 406 DISSECTION OF THE ABDOMEN. The deeper layer (aponeurosis of the fascia lata, Scarpa) is thinner and more membranous than the other, and is closely united to the tendon of the external oblique by fibrous bands, especially towards the linea alba. Like the subcutaneous part, this layer is continued upwards on the abdo- men, and inwards to the penis and the scrotum : here it becomes very thin, and reaches the perinaeum, where it has attachments to the subjacent parts, as before specified (p. 393). Towards the limb, it ends a little be- low Poupart’s ligament in the fascia lata across the front of the thigh ; as it passes over the ligament it is closely joined to that band by fibrous tissue. Urine effused in the perinaeum from rupture of the urethra will be directed through the scrotum and along the spermatic cord to the abdo- men (p. 393). From the arrangement of the deeper layer of the fascia across the thigh, it is evident that the fluid cannot pass down the limb, though its progress over the front of the abdomen is uninterrupted. In the female the fatty layer of the groin is separable into two' layers, and the disposition of each is nearly the same as in the male ; but the part that is continued to the scrotum in the one sex enters the labium in the other. In the female the round ligament of the uterus is lost in it. Cutaneous Nerves. The nerves in the teguments are derived from the trunks of the lower intercostal nerves ; thus the cutaneous branches, along the side of the belly, are offsets from five or six of those nerves ; and the cutaneous branches, along the front, are the terminal parts of the same trunks. Two other cutaneous offsets from the lumbar plexus, viz., ilio-hypogastric and ilio-inguinal, appear at the lower part of the ab- domen. The lateral cutaneous nerves of the abdomen emerge between the digi- tations of the external oblique muscle, in a line with the same set of nerves on the thorax ; and the lowest are the most posterior. As soon as they reach the surface they divide, with the exception of the last, into an an- terior and a posterior branch : — The posterior branches are small in size, and are directed back to the integuments over the latissimus dorsi muscle. The anterior branches are continued nearly to the edge of the rectus muscle, and in increasing in size from above down, supply the integu- ments on the side of the belly ; they furnish offsets to the digitations of the external oblique muscle. The lateral cutaneous branch of the last dorsal nerve is larger than the rest, and does not divide like the others. After piercing the fibres of the external oblique muscle, it is directed over the iliac crest to the sur- face of the gluteal region. The anterior cutaneous nerves of the abdomen pierce the sheath of the rectus : in the integuments they bend outwards towards the lateral cuta- neous nerves. The number, and the situation of these small nerves, are very uncertain. The ilio-hypogastric nerve is distributed by two pieces : one passes over the crista ilii (iliac branch), the other ramifies on the lower part of the abdomen (hypogastric branch) : — The iliac bra7ich lies close to the crest of the hip bone near the last dorsal nerve, and enters the teguments of the gluteal region. The hypogastric branch pierces the aponeurosis of the external oblique muscle above the abdominal ring, and is distributed, as the name ex- presses, to the lower part of the abdomen. CUTANEOUS VESSELS. 40T The ilio-inguinal nerve becomes cutaneous through the external abdo- minal ring, and descends to the teguments of the scrotum, and upper and inner parts of the thigh. Cutaneous Vessels. Cutaneous vessels run with both sets of nerves on the abdomen : with the lateral cutaneous nerves are branches from the intercostal arteries ; and with the anterior cutaneous are otfsets from the intercostal, internal mammary, and epigastric vessels. In the groin are three small superficial branches of the femoral artery, viz., pudic, epigas- tric, and circumflex iliac. The lateral cutaneous arteries have the same distribution as the nerves they accompany. The anterior or chief offsets are directed towards the front of the abdomen, and end about the outer edge of the rectus muscle. Tlie anterior cutaneous vessels are irregular in number and in position, like the nerves. After piercing the sheath of the rectus, they run out- wards with the nerves towards the other set of branches. Branches of the femoral artery. Three cutaneous offsets ascend from the thigh between the layers of the subcutaneous fat, and ramify in the integuments of tlie genital organs and lower part of the abdomen. The greater portion of these vessels appears in the dissection of the thigh. The external 'pudic branch (superficial) crosses the spermatic cord, to which it gives offsets, and ends in the integuments of the under part of the penis. The superficial epigastric branch ascends over Poupart’s ligament, near the centre, and is distributed in the fat nearly as high as the umbilicus. The circumflex iliac branch lies usually below the level of the iliac crest, and sends only a few offsets upwards to the abdomen. Small veins accompany the arteries, and join the internal saphenous vein of the thigh. The glands of the groin are three or four in number, and lie over the line in Poupart’s ligament. They are placed between the strata of the superficial fascia ; and receive lymphatics from the abdominal wall, from the upper and outer portion of the thigh, and from the superficial parts of the genital organs. Their efferent ducts pass downwards to the saphenous opening in the thigh to enter the abdomen. Dissection. After the examination of the superficial fat with its ves- sels and nerves the student may prepare the cutaneous coverings of the penis and scrotum. The skin may be divided along the dorsum of the penis, and thrown to each side ; and the skin of the scrotum is to be re- flected on the left side by means of a vertical incision. Cutaneous coverings of the penis and scrotum. The penis is attached to the front of the pubes by a suspensory ligament, and is provided with a tegumentary covering which is continuous with that of the abdomen, but it loses the fat and acquires special characters. Around the end of the penis it forms the loose sheath of the prepuce in the following way : When the skin has reached the extremity, it is re- flected backwards as far as the base of the glans, constituting thus a sheath with two layers — the prepuce; it is afterwards continued over the glans, and joins the mucous membrane of the urethra at the orifice on the sur- face. At the under part of the glans, and behind the aperture of the urethra, the integument forms a small triangular frcenum prceputii. Where the skin covers the glans, it is inseparably united witli that part, is very thin and sensitive, being provided with papilla3, and assumes in 408 DISSECTION OF THE ABDOMEN. some cases the characters of a mucous membrane. Behind the glans are some sebaceous follicles — glandulce odoriferce. In the scrotum, the superficial fascia becomes thin, and of a reddish color. The prolongation around the testicle on one side, is separate from that on the other side ; and the two pouches coming in contact in the middle line, form the septum scroti. The subcutaneous layer in tlie scrotum, penis, and front of the jierineum, contains involuntary muscular fibres, to which the corrugation of the skin is owing. This contractile structure is named the dartoid tissue. Dissection. By removing all the fatty tissue from the root of the penis and the front of tlie symphysis pubis, tlie suspensory ligament will be de- fined. And the dorsal arteries and nerves, with the dorsal vein of the penis, which will be partly laid bare, are to be followed forwards in the teguments. The suspensory ligament of the penis is a band of fibrous tissue, of a triangular form, which is attached by its apex to the front of the symphy- sis pubis near the lower part. Widening below, it is fixed to the upper surface of the body of the penis, and is prolonged on it for some distance. In the ligament are contained the dorsal vessels and nerves of the penis. Dorsal vessels and nerves. The arteries and nerves on the dorsum of the penis are the terminal parts of the pudic trunks of both sides (p. 399). The vein accompanying the arteries enters the pelvis through the triangu- lar perinasal ligament. The dorsal artery., one on each side, pierces the suspensory ligament, and extends forwards to the glans, where it ends in many branches for that structure: in its course the vessel supplies the integuments and the body of the penis. It may be derived from the accessory pudic (p. 399). The dorsal vein is a single trunk, and commences by numerous branches from the glans penis and the prepuce. It runs backwards by the side of the artery, through the suspensory ligament and the triangular ligament of the urethra, to join the prostatic plexus of veins. The vein receives branches from the erectile structure and the teguments of the penis. P^ach dorsal nerve takes the same course as the artery, and ends like it in numerous branches to the glans penis. It furnishes a large branch to the corpus cavernosum penis, and other offsets to the integuments of the dorsum, sides, and prepuce of the penis. In the female these vessels are much smaller than in the male ; they occupy the upper surface of the clitoris — the organ that represents the penis. Dissection of the muscles. The surface of the external muscle of the abdominal wall (fig. 135) is now to be freed from fascia on both sides of the body. • It is not advisable to begin cleaning this muscle in front, because there it has a thin aponeurosis, which is taken away too readily with the fat. Beginning the dissection at the posterior jiart, the student is to carry the knife oblicjiiely upwards and downwards in the direction of the fibres. The thin aponeurosis before referred to is in front of a line extended up- wards from the anterior part of the iliac crest; and as the dissector ap- proaches that spot, he must be careful not to injure it, more particularly at the u})per part, where it lies on the margin of the ribs, and is very indistinct. On the right side the external abdominal ring, c, may be defined, to show the cord passing through it; and on the left side a thin fascia (inter- EXTERNAL OBLIQUE MUSCLE. 409 columnar), wliich is connected with the margin of that opening, is to be preserved. Lastly the free border of the external oblique should be made evident between the last rib and the iliac crest. Muscles of the abdominal avall. On the side of the abdomen are three large flat muscles, which are named from their position to one another, and from the direction of their fibres. The most superficial mus- cle is tlie external oblique; the underlying one, the internal oblique; and the deepest, the transversalis. Along the middle line are placed other muscles which have a vertical direction. In front lie the rectus and pyramidalis, and beliind is the quadratus lurnborum : these are encased by sheaths derived from the aponeuroses of tlie lateral muscles. The EXTERNAL OBLIQUE MUSCLE (fig. 135, is fleshy on the side, and aponeurotic on the fore part of the abdomen. It arises by fleshy processes from the eight lower ribs; the five highest pieces alternating with similar })arts of tlie serratus magnus, and the lowest three with digitations of the latissimus dorsi muscle. From the attach- ment to the ribs the fibres are directed over the side of the abdomen in the following manner: — the lower ones descend almost vertically to be inserted into the anterior half or more of the iliac crest, at the outer margin: and the upper and middle fibres are continued forwards obliquely to the aponeurosis on the front of the belly. The aponeurosis occupies the anterior part of the abdomen, in front of a line from the eighth rib to the fore part of the crista illi; and it is rather narrower about the centre, than either above or below. Along the middle line this expansion ends in tlie linea alba^ — the common point of union of the aponeuroses of opposite sides. Above, it is thin, and is continued on the thorax to the pectoralis major and the ribs. Below, its fibres are stronger and more separate than above, and are directed obliquely downwards and inwards to the pelvis: some of them are fixed to the front of the pubes; and the rest are collected into a firm band b (Poupart’s ligament) between the pubic spine and the iliac crest. Connections. The muscle is subcutaneous. Its posterior border is unattached between the last rib and the iliac crest, but is overlaid com- monly by the edge of the latissimus dorsi, except a small part below. Appearing through the aponeurosis, external to the linea alba, is a white line, the linea semilunaris, marking the outer edge of the rectus muscle (fig. 139); and crossing between the two are three or four whitish marks, the line^E transversal. Numerous small apertures in the tendon transmit cutaneous vessels and nerves ; and near the pubes is the large opening of Dissection of the first Lateral Muscle in the Wall of the Belly. A. External oblique. B. Ponpart’s ligament. c. External abdominal ring. D. Gimbernat’s ligament. 410 DISSECTION OF THE ABDOMEN. the external abdominal ring, which gives passage to the cord in the male, and the round ligament in the female. Action. Both muscles taking their fixed point at the pelvis will bend the trunk forwards as in stooping; but supposing the spine fixed they will draw down the ribs. If they act from the thorax they will elevate the pelvis. Should one muscle contract, it will incline the trunk or the pelvis to the same side, according as the upper or the lower attachment may be movable : and it will turn the thorax to the opposite side. Parts of the aponeurosis. Besides the general arrangement of the aponeurosis over the front of the abdomen, the student is to examine more minutely the linea alba in the middle line ; the external abdominal ring with the fascia prolonged from its margin ; and the rounded border named Poupart’s ligament. Linea alba (fig. 139). This white band on the front of the abdomen marks the place of meeting of the aponeuroses of opposite sides. It ex- tends from the xiphoid cartilage to the pubes, and serves as a ligament between the chest and pelvis. Its breadth Is wider above than below ; and it is perforated here and there by small apertures, which allow pellets of fat to protrude in some bodies. A little below the centre is the um- bilicus, which projects now beyond the surface, though before the skin was removed, a hollow indicated its position. External abdominal ring (fig. 135, ®). This opening is situate near the pubes between the diverging fibres of the aponeurosis. It is somewhat triangular in form, with the base of the crest of the pubes, and the apex pointing upwards and outwards. The long measurement of the aperture is about an inch, and the transverse about half an inch. Its margins are named pillars, and difier in form and strength. The inner one, thin and straight, is attached below to the front of the symphy- sis pubis, where it crosses the corresponding piece of the opposite side — that of the right muscle being superficial. The outer margin is the strong- est, and is not straight like the inner, but forms a kind of groove for the support of the spermatic cord : this margin is continuous with Poupart’s ligament, and is attached below to the pubic spine or tuberosity. A thin membrane (intercolumnar) covers the opening, and is derived from some fibres on the surface of the aponeurosis. The ring gives passage in the male to the spermatic cord, and in the female to the round ligament ; and in each sex the transmitted part lies on the outer pillar as it passes through, and obtains a covering from the intercolumnar fibres. Through this aperture the inguinal hernia protrudes from the wall of the abdomen. The intercolumnar jibres form a layer over the aponeurosis, and bind together its parallel fibres, so as to construct a firm membrane. Inferiorly, where they are strongest, a bundle is connected with the outer third of Poupart’s ligament, and is continued back to the crista ilii. At the ex- ternal abdominal ring the fibres stretch from side to side, and becoming stronger and aggregated together, close the upper part of that opening ; and as they are ])rolonged on the cord from the margin of the ring, they give rise to the membrane named intercolumnar fascia. On the left side, where the fascia is entire, this thin covering will be manifest on the surface of the cord, or on the round ligament in the female. Dissection. To see the attachments and connections of Poupart’s liga- ment, it will be necessary to refiect, on both sides of the body, the lower INTERNAL OBLIQUE MUSCLE. 411 part of the aponeurosis towards the thigh, as in fig. 140. For this pur- pose an incision is to be carried through the aponeurosis from the front of the iliac crest to about three inches from the linea alba ; and the tendon is to be detached from the subjacent parts with the handle of the scalpel. When the aponeurosis cannot be separated farther from the tendons be- neath, near the linea alba, it is to be cut in the direction of a vertical line to the symphysis pubis. After the triangular piece of the aponeurosis has been thrown towards the thigh, the spermatic cord is to be dislodged from the surface of Pou- part’s ligament, to see the insertion of this band into the pubes, and to lay bare the fibres (triangular ligament) which ascend therefrom to the linea alba. Pouparfs ligament (fig. 136, is the lower border of the aponeurosis of the external oblique, which intervenes between the front of the crista ilii and the pubes. Externally it is round and cord-like, and is attached to the anterior superior iliac spine. Internally it widens as it approaches the pubes (fig. 135, ®), and is inserted into the pubic spine and the pec- tineal line of the hip-bone for about three-quarters of an inch, forming a triangular-looking piece with its base directed outwards, which is named Gimhernaf s ligament. Poupart’s ligament is not straight between its outer and inner attach- ments, but is curved downwards to the thigh ; and it retains this position as long as the fascia lata remains uncut. Its outer half is oblique, and is firmly united with the subjacent iliac fascia ; along the line of union of the two, tlie otlier lateral muscles of the abdominal wall are attached. Its inner half is placed over the vessels passing from the abdomen to the thigh. Triangular ligament. From the insertion of Gimbernat’s ligament into the peetineal line, some fibres are directed upwards and inwards to the linea alba, where they blend with the other tendons. As the fibres ascend, they diverge and form a thin band, to which the above name has been given. Dissection. The upper part of the external oblique is now to be taken away, on both sides of the body, to see the parts underneath. The muscle may be detached by carrying the scalpel through the digitations on the ribs back to the free border, and then through the insertion into the crista ilii. It may be thrown forwards as far as practicable, after the nerves crossing the iliac crest are dissected out ; but in raising it care must be taken not to detach the rectus muscle from the ribs above, nor to cut through the tendon of the internal oblique at the upper part. By the removal of the fatty tissue the underlying internal oblique muscle, with some nerves on its surface below, will be prepared. At the lower border of the internal oblique the cremaster muscle on tlie cord is to be defined (fig. 137) : it is about as wide as the little finger, and consists of fleshy loops which issue through the external abdominal ring. Its inner attachment is tendinous, and is easily taken away. Parts covered by external oblique (fig. 136). Beneath the external, is the internal oblique muscle, with the ribs and the intercostal muscles. At the lower part of the abdomen the muscle conceals the spermatic cord, and the branches of the lumbar plexus in the abdominal wall. The INTERNAL OBLIQUE 3IUSCLE (fig. 136,^) is flcshy bclow and a|)0- neurotic above, just the reverse of the preceding ; and its fibres (except the lowest) ascend across those of the external oblique. The muscle arises 412 DISSECTION OF THE ABDOMEN. along tlie outer half of Poiipart’s ligament ; along the anterior two-thirds of tlie crest of the hip bone ; and from the tendon of the transversalis muscle, c, (fascia lumborum) in the interval between that bone and the last rib. The fibres diverge on the abdomen to their destination : The upper are fleshy and ascend to be inserted into the cartilages of the lower three ribs, where they join the inter- nal intercostal muscles of the lowest two spaces. The remaining fibres pass obliquely to the aponeurosis. Tlie aponeurosis covers tlie fore part of the abdomen from the pelvis to the chest, and blends with its fellow along the middle line. For the most part it incases the rectus; but midway between the umbilicus and the pubes it is undivided, and lies in front of that muscle. Supe- riorly it is attached to tlie thorax after the following manner: The stratum superficial to the rectus is fixed to the ninth rib, and blends with the aponeurosis of the external oblique ; and tlie stratum beneath tlie muscle joins the cartilages of the eighth and seventh ribs, and the en- siform cartilage. Inferiorly its fibres become more distinct and separate, and are inserted into the front of the pubes, and into the pectineal line for half an inch behind the attachment of Gimbernat’s ligament. Connections. The internal is cov- ered by the external oblique muscle. It is attached on all sides, except between Poupart’s ligament and the pubes where it arches over the cord, and has the cremaster muscle con- tiguous to it. The parts covered by the internal oblique cannot be seen till the muscle is reflected. Action — Both muscles will depress the ribs ; and will assist in forcing back the viscera of the belly, which have been carried down by the descent of the diaphragm. One muscle may incline the body laterally ; and contracting with the external oblique of the otlier side (the fibres of the two having the same direction) it will rotate the trunk to the same side. The CREMASTER MUSCLE (fig. 137, is a fascictdus of fibres, which lies along the lower border of the internal oblique muscle, and is named from suspending the testicle. The muscle has attachments, at the inner and outer sides, similar to those of the internal oblique. Externally it is fleshy, and arises from Poupart’s ligament below, and in part beneath the internal obli({ue, 'with Mdiich some of the fibres are connected. Internally it is small, and is inserted by tendon into the front of the pubes, joining the tendon of the internal oblique. Fig. 136. Internal Obliqce Musci,e of the Abdomi- nal Wall. A. Internal oblique. B. Latissimus dor.si, cut. c. Part of the binder tendon of the transver- .salis muscle. D. Poupart’s ligament. K External: F. Internal intercostals. TRANSVERSALIS MUSCLE. 413 Between the two points of attachment the fibres descend on the front and sides of the cord, forming loops, with the convexity downwards, which reach to and over the testis. The bundles of fibres are united by areolar tissue so as to give rise to a covering on the front of the cord, which in hernia is named the fascia cremasterica. Occasionally the fibres may be behind as well as on the sides and front of the cord. Fig. 137. Action. It elevates the testicle towards the abdomen under the in- fluence of the will; but it may be excited to contract involuntarily by cold, fear, etc. Dissection. On the left side of the body the student is not to make any further dissection of the abdo- minal wall ; and the layers that have been reflected in the groin should be replaced, until the examination of those parts in connection with hernia is resumed. On the right side the dissection is to be carried deeper by the removal of the internal oblique and the cre- master. The last muscle may be reflected from the cord by means of a longitudinal incision. To raise the internal oblique, it will be necessary to cut it through firstly near the ribs ; secondly near the crest of the hip bone and Pou- part’s ligament; and lastly at the hinder part, so as to connect the two first incisions. Its depth will be in- dicated by a fatty layer between it and the transversal is. In raising the muscle towards the edge of the rectus, let the student separate with great care the lower fibres from those of the transversalis, with which they are often conjoined ; and dissect out, between the two, the intercostal nerves and arteries, and the two branches of the lumbar plexus (ilio-hypo- gastric and ilio-inguinal) near the front of the crest of the hip bone : the offsets of the intercostals entering the muscle must be cut. Parts covered by the oblique (fig. 138). The internal oblique conceals the transversalis muscle, and the vessels and nerves between the two. Near Poupart’s ligament it lies on the spermatic cord and the fascia trans- versalis. The rectus muscle is concealed below by the aponeurosis. The TRANSVERSALIS MUSCLE (fig. 138, foiTRS the third stratum in the wall of the abdomen, and differs from the two oblique in having a posterior as well as an anterior aponeurosis. Like the former muscle it is attached on all sides, except where the spermatic cord lies. At the pelvis it arises along the outer third of Poupart’s ligament, and the anterior two- thirds of the iliac crest. At the chest it takes origin from the lower six View of the Lower Part of the Internal Oblique with the Cremaster Muscle and THE Testicle. A. External oblique, reflected. B. Internal oblique, c. Rectus abdominis. D. Cremaster, with its loops over the sperma- tic cord and the testicle. 414 DISSECTION OF THE ABDOMEN. ribs, viz., by tendon from the lowest two, and by fleshy processes from the under surface of the cartilages of the four next above. And between the chest and the pelvis it is connected with the lumbar vertebrae by means of the posterior aponeurosis or the fascia lumborum. All the fibres are directed to the aponeurosis in front. Its anterior a'poneurosis is widest below, as in the most external muscle. Internally it is continued to tlie linea alba, passing beneath the rectus as low as midway between the umbilicus and the pubes, but in front of the muscle below that spot. Its attachment below to the pelvis is nearly the same as the internal oblique ; for it is fixed to the front of the pubes^ and to the pectineal line for about an inch, but beneath the oblique muscle : some of the fibres are spent on the trail sversalis fascia, and are con- nected with a thickened band of that fascia beneath Poupart’s ligament, which is called the deep crural arch. Action. The chief use of the muscle will be applied to diminish- ing the size of the abdominal cavity, and compressing the viscera ; but it will assist the internal oblique in re- placing tlie viscera pushed down in inspiration. Conjoined tendon. The aponeu- rosis of the internal oblique and transversalis muscles are united more or less near their attachment to the pubes, and give rise to the conjoined tendon. The aponeurosis of the oblique muscle extends about half an inch along the pectineal line ; whilst that of the transversalis reaches an inch along the bony ridge, and forms the greater part of the conjoined tendon. The posterior' aponeurosis of the transversalis, or the fascia lumbo- rum, c, is described in the dissection of the Back, p. 357. Connections. Superficial to the transversalis are the two muscles be- fore examined ; and beneath it is the thin fascia transversalis. Its fleshy attachments to the ribs digi- tate with like processes of the diaphragm. The lower border is fleshy in the outer, but tendinous in the inner half, and is arched above the internal abdominal ring. Dissection. To remove the aponeurotic layer from the rectus muscle of the right side, make a longitudinal incision through the tendinous slieath, and turn it to each side. As the fascia is reflected, its union with three or more tendinous bands across the rectus will have to be cut tlirough ; and near the pubes a small muscle, the pyramidalis, will be ex Fig. 138. Disskction of the Third Lateral Muscle IN the Wall of the Belly, with the ves- sels and nerves on it. A Transversalis muscle, with B, its anterior, and c, its posterior tendon (fascia Inm- borum). D. Poupart’s ligament. 1. Last dorsal nerve with its accompanying artery. ‘‘ 1 . Ilio-hypogastric nerve with its artery. If Intercostal neves and arteries. RECTUS MUSCLE. 415 Fiff. 139. posed. The dissector should leave the nerves entering the outer border of the rectus. On the left side of the body the rectus should not be laid bare below the umbilicus, for the sake of the hernia to be seen on this side. The RECTUS MUSCLE (fig. 139, extends along the front of the abdo- men from the pelvis to the chest. It is narrowest inferiorly, and is at- tached to the [)ubes by two tendinous processes ; — one, internal and the smaller, arises from tlie front of the symphysis, where it joins the muscle of the opposite side ; and the external process is attached to the pubic crest. Becoming wider towards the thorax, the rectus is inserted by three large fleshy processes into the ensiform cartilage, and the cartilages of the last three true ribs. The muscle is contained in an aponeurotic sheath, except above and below ; and its fibres are interrupf- ed at intervals by irregular tendi- nous lines — the inscriptiones ten- dineae. Action. It will draw down the thorax and the ribs, or raise the pelvis, according as its fixed point may be above or below. Besides imparting movement to the trunk, it will diminish the cavity of the thorax, and compress the viscera. Sheath of the rectus., d. This sheath is derived from the s})litting of the aponeurosis of the internal oblique at the outer edge of the muscle. One piece passes before and the other under tlie rectus ; and the two unite at the inner border so as to inclose it in a sheath. Inseparably blended with the stratum in front of the rectus is the aponeurosis of the external oblique ; and joined in a similar manner with that behind, is tlie ajioneurosis of the transversalis. The sheath is deficient behind, both at the upper, and lower part of the muscle. Above, the muscle rests on the ribs, without the in- tervention of the sheath which is fixed to the margin of the thorax. Below, midway between the um- bilicus and the pubes, the internal oblique ceases to split, and ))asses altogether in front of the rectus, with the other aponeuroses ; at the spot where the sheath is wanting inferiorly the muscle is in contact with the fascia transversalis, and a white semilunar line (the fold of Douglas) may be sometimes seen, when the outer edge is raised, marking the cessation. The linem transversce (fig. 137), on the surface of the abdomen, are caused by tendinous intersections of the rectus. They are usually three Rectl's Muscle of the Abdomen, dissected on the right side, and in its sheath on the left. Close to the pelvis is the pyramidalis exposed. A. Rectus, B. Internal oblique. c. Poupart’s ligament. D. Sheath of the rectus. 416 DISSECTION OF THE ABDOMEN. in number, and have the following position : one is opposite the umbilicus, another at the ensiform cartilage, and the third midway between the two. If there is a fourth, it will be placed below the umbilicus. These mark- ings seldom extend the whole length or breadth of the muscular fibres, more particularly above and below. Linea semilunaris (fig. 139). This line corresponds with the outer edge of the rectus, and reaches from the eighth rib to the pubic spine of the hip-bone : it marks the line of division of the aponeurosis of the internal oblique muscle. The PYRAMiDALis MUSCLE (fig. 139) is triangular inform, and is placed in front of the rectus near the pelvis. The muscle arises by its base from the front of the pubes, and is inserted into the linea alba about midway between the umbilicus and the pelvis. This small vessel is often absent. Action. The muscle renders tight the linea alba ; and when large it may assist the rectus slightly in compressing the viscera. Nerves of the abdominal wall (fig. 138). Between the internal oblique and transversalis muscles are situate the intercostal nerves ; and near the pelves are two branches of the lumbar plexus. Some arteries accompany tlie nerves, but they will be referred to with the vessels of the abdominal wall. The hmer six intercostal nerves (fig. 138ttt) enter the wall of the abdomen from the intercostal spaces. Placed between the two deepest lateral muscles, the nerves are directed forwards to the edge of the rectus, and through this muscle to the surface of the abdomen near the middle line. About midway between the spine and the linea alba, the nerves furnish cutaneous branches to the side of the abdomen (lateral cutaneous, p. 40G) ; and whilst between the abdominal muscles they supply muscular branches, and offsets of communication with one another. A greater part of the lower than of the upper nerves is visible, owing to the shortness of the last intercostal spaces. The last dorsal nerve (*) is placed below the twelfth rib, and therefore not in an intercostal space, but it has connections and a distribution like the preceding. As it extends forwards to the rectus it communicates sometimes with the ilio-hypogastric nerve. Its lateral cutaneous branch perforates the two oblique muscles (p. 40G). 'Two branches of the lumbar plexus^ viz., ilio-hypogastric and ilio-ingui- nal, are contained for a certain distance between the muscles of the wall of the abdomen, as they course forwards to the surface of the body. The ilio-hypogastric nerve (^) perforates the back of the transversalis muscle near the iliac crest, and gives off the iliac branch. The nerve is then directed forwards above the hip bone, and is connected with its com- panion (ilio-inguinal). Perforating the fieshy part of the internal oblique near the front of the iliac crest, and the aponeurosis of the external oblique near the linea alba, the nerve becomes cutaneous (p. 40 G). Its iliac branch pierces both oblique muscles close to the crista ilii, to reach the gluteal region. The ilio-inguinal nerve perforates the transversalis muscle near the front of the iliac crest. It })ierces afterwards tlie internal oblique, and reaches the surface of the thigh through the external abdominal ring (p. 407); it furnishes offsets to the internal obli(iue, the cremaster, and the pyramidal is. Dissection. For the puiq)Ose of seeing the transversalis fascia, it will ])e necessary to raise, on the right side, the lower part of the transversalis FASCIA TRANSVERSALIS. 417 muscle by two incisions ; one of these is to be carried through the fibres attached to Foupart’s ligament; the other, across the muscle from the front of the hip bone to the margin of the rectus. With a little care the muscle may be separated easily from the thin fascia beneath. The fascia transversalis (fig. 140, is a thin fibrous layer between the transversalis muscle and the peritoneum. In the groin or inguinal region, where it is unsupported by muscles, the fascia is considerably stronger than elsewhere, and is joined by fibres of the aponeurosis of the transversalis muscle; but fartlier from the pelvis it gradually decreases in strength, until at the thorax it becomes very thin. In tlie part of the fascia now laid bare, is the internal abdominal ring, which gives passage to the spermatic cord, or the round ligament, accord- ing to the sex ; this opening resembles the finger of a glove in being visible internally, but indistinguishable externally in consequence of a prolonga- tion from the margin. On the inner side of the ring the fascia is thinner than on the outer, and is there fixed into the pubes and the pectineal line of the hip bone, behind the conjoine 1 tendon with which it is united. At Poupart’s ligament the fascia is joined to the posterior margin of that band along the outer half; but along the inner half it is directed down to the thigh, in front of the bloodvessels, to form the anterior part of a loose sheath (crural) around them. Internal abdominal ring (fig. 140). This opening is situate midway between the symphysis pubis and the anterior superior iliac spine, and half an inch above Poupart’s ligament. From its margin a thin tubular prolongation of the fascia is continued around the cord, as before said. Dissection, The tubiform prolongation on the cord may be traced by cutting the fascia transversalis horizontally above the opening of the ring, and then longitudinally over the cord. With the handle of the scalpel the thin membrane may be reflected to each side, so as to lay bare the subperitoneal fat. The subperitoneal fat forms a layer betw^een the fascia transversalis and the peritoneum. Its thickness varies much in different bodies, but is greater at the lower part of the abdomen than higher up. This structure will be more specially examined in the dissection of the wall of the abdomen from the inside. Dissection. After the subperitoneal fat has been seen, let it be reflected to look for the remains of a piece of peritoneum along the cord, in the form of a fibrous thread. The peritoneum,, or the serous sac of the abdominal cavity, projects for- wards slightly opposite the abdominal ring. Connected with it at that spot is a fibrous thread (the remains of a prolongation to the testis in the fcetus) wdiich extends a certain distance along the front of the cord. It is generally impervious, and can be followed only a very short way, but it may be sometimes traced as a fine band to the tunica vaginalis of the testis. In some bodies the process may be partly open, being sacculated at in- tervals; or it may form occasionally a single large bag in front of the cord. Lastly, as a rare state, the tube of peritoneum accompanying the testis in its passage in the foetus may be unclosed, so that a coil of intestine could descend in it from the abdomen. In the female the foetal tube of peritoneum remains sometimes pervious for a short distance in front of the round ligament; that unobliterated passage is named the canal of Nuck. 27 418 DISSECTION OF THE ABDOMEN. The SPERMATIC CORD (fig. 140, extends from the internal abdominal ring to the testis, and consists mainly of the vessels and the efferent duct of the gland, united together by coverings from the structures by or through which they pass. In the wall of the abdomen tlie cord lies obliquely, because its aperture of entrance amongst, is not opposite its aperture of exit from the muscles; but escaped from the abdomen, it descends almost vertically to its destina- tion. As it lies in this oblique passage named the inguinal canal, it is jdaced (externally) beneath the internal obliqoe, and rests against the fascia transversalis ; but beyond the lower border of the oblique muscle, it lies on the upper surface of Poupart’s ligament, with the aj)oneurosis of the external oblique between it and the surface of the body, and the con- joined tendon behind it. Its several coverings are derived from strata in the wall of the abdomen. Thus, from within out come, the subperitoneal fat, the tube of the fascia transversalis, the cremaster muscle continuous with the internal oblique, the intercolumnar fascia from the external oblique muscle, and lastly the superficial fascia and the skin. Tlie round ligament, or the suspensory cord of the uterus, occupies the inguinal canal in the female, and ends in the integuments of the groin. Its coverings are similar to those of the spermatic cord, except it wants the cremaster. Dissection. The constituents of the cord will be displayed by cutting through longitudinally, and turning aside the different surrounding layers, and removing tlie areolar tissue. The dissector should trace branches of the genito-crural nerve and epigastric artery into the cremasteric covering. Vessels and nerves of the cord. In the cord are collected together the spermatic artery and vein which convey the blood to, and take it away from the testis ; the nerves and lymphatics of the testicle ; and the vas deferens or the efferent duct. In the female a branch from the ovarian artery enters the round ligament. The vas deferens reaches from the testicle to the urethra, and is placed behind the other vessels of the cord ; it will be recognized by its resem- blance in feel to a piece of whipcord, when it is taken between the finger and the thumb. As it enters the abdomen through the opening in the fascia transversalis (internal ring), it lies on the inner side of the vessels of the testicle; and as it begins its descent to the pelvis, it winds behind the e[)igastric artery. Cremasteric artery and nerve. The cremasteric covering of the cord has a separate artery and nerve. The artery is derived from the epigastric, and is distributed to the coverings of the cord. The genital branch of the genito-crural nerve enters the cord by the internal abdominal ring, and ends in the cremaster muscle. Cutaneous vessels and nerves are supplied to the teguments of the cord from the superficial pudic artery and the ilio-inguinal nerve. Dissection. By cutting through the spermatic cord near the pubes, and raising it towards the inner abdominal ring, a fibrous band below Pou- part’s ligament, the deep crural arch, will appear : it passes inwards to the pubes, and is to be defined with some care. The remaining vessels of the abdominal wall, viz., the epigastric and circumflex iliac, and the ending of the internal mammary artery are to be next dissected. The epigastric and mammary arteries will be observed on VESSELS IN ABDOMINAL WALL. 419 raising the outer edge of the rectus, one above and the other below, rami- fying in the muscle. The epigastric, with its earliest branches, may be traced by removing tlie fascia transversalis from it near Poupart’s ligament. The circumflex iliac artery lies behind the outer half of Poupart’s ligament, and sliould be pursued along the iliac crest to its ending. Deep crural arch. Below the level of Poupart’s ligament is a thin band of transverse fibres over the femoral vessels, which has received the name deep crural arch from its position and resemblance to tlie superficial crural arch (Poupart’s ligament). This fasciculus of fibres, beginning about tlie centre of the ligament, is prolonged inwards to the pubes, where it is widened, and is inserted into the pectineal line at the deep aspect of the conjoined tendon of tlie broad muscles of the abdomen.^ It is closely connected with the front of the crural sheath. Vessels in the Wall of the Abdomen. On the side of the abdomen are the intercostal and lumbar arteries with the intercostal nerves. In the sheath of the rectus lie the epigastric and internal mammary vessels ; and around the crest of the hip-bone bends the circumflex iliac branch. The intercostal arteries (fig. 138) issue between the false ribs (p. 337), and enter the abdominal wall between the transversalis and internal ob- lique muscles: they extend forwards with the nerves, supplying the con- tiguous muscles, and some end in the teguments. In front they anasto- mose witli the internal mammary and epigastric : behind they communicate with the lumbar arteries. The lowest artery accompanies the last intercostal nerve below the last rib, and is distributed with the nerve. The internal mammary artery. The abdominal branch of this vessel (p. 239) enters the wall of the abdomen beneath the cartilage of the seventh rib. Descending in the sheath of the rectus, the vessel soon enters the substance of the muscle, and anastomoses in it with the epigastric artery. The epigastric artery (fig. 140, a') arises from the external iliac about a quarter of an inch above Poupart’s ligament ; it ascends in the sheath of the rectus and divides above the umbilicus into branches which enter that muscle, and anastomose with the internal mammary. As the artery courses to the rectus it passes beneath the cord, and on the inner side of the internal abdominal ring ; and it is directed obliquely inwards across the lower part of the abdomen, so as to form the outer boundary of a triangular space along the edge of the rectus. It lies at first beneath the fascia transversalis ; but soon perforates the fascia, and enters the sheath of the rectus over the semilunar border at the posterior aspect. The branches of the artery are numerous, but inconsiderable in size : — a. The pubic branch is a small transverse artery, which runs behind Poupart’s ligament to the posterior aspect of the pubes, and anastomoses with a similar branch from the opposite side. Behind the pubes it com- municates with a small offset from the obturator artery (fig. 141,/) : the size of this anastomosis varies much, but its situation is internal to the crural ring. • Sometimes this structure is a firm distinct band, which is joined by some of the lower fibres of the aponeurosis of the external oblique. At other times, and this is the most common arrangement, it is only a thickening of the fascia trans- versalis with the fibres added from the tendon of the transversalis muscle. 420 DISSECTION OF THE ABDOMEN. h. A cremasteric branch is furnished to the muscular coverine: of the cord. c. Muscular branches are given from the outer side of the artery to the abdominal wall, which anastomose with the intercostal arteries (p. 419), and others enter the rectus. Cutaneous offsets pierce the muscle, and ramify in the integuments with the anterior cutaneous nerves. Two epigastric veins lie with the artery; they join finally into one, which opens into the external iliac vein. The circumflex iliac artery arises from the outer side of the external iliac, opposite the epigastric, and courses around the iliac crest, as the name expresses. Having perforated the crural sheath, it passes beneath the transversalis muscle to the middle of the crest of the hip-bone. Here it pierces the transversalis, and is continued backwards between this and the internal oblique, to anastomose with the ilio-lumbar branch of the in- ternal iliac artery. Its ofisets are muscular and anastomotic. Branches. Near the front of the iliac crest a small branch ascends be- tween the internal oblique and transversalis muscles, supplying them, and anastomoses with the epigastric and intercostal arteries. As the vessel extends backwards it gives lateral offsets, which supply the neighborin" muscles, and communicate on the one side with the ilio- lumbar, and on the other with the gluteal artery. The circumflex iliac vein is formed by the junction of two collateral branches, and crosses the external iliac artery nearly an inch above Pou- part’s ligament, to open into the external iliac vein. Section II. HERNIA OF THE ABDOMEN. The lower part of the abdominal wall, which has been reserved on the left side of the body, should now dissected for inguinal hernia. Dissection. The teguments and the aponeurosis of the external oblique having been thrown down in the previous examination of the wall of the abdomen, the necessary dissection of the inguinal region will be completed by raising the internal oblique muscle, as in fig. 140. To raise the oblique muscle, let one incision be made across the flesliy fibres from the iliac crest towards the linea alba ; and after the depth of the muscle has been ascertained by the layer of areolar and fatty tissue beneath it, let the lowest fibres be carefully cut through at their attach- ment to Poupart’s ligament. By raising the muscle cautiously, the stu- dent will be able to separate it from the subjacent transversalis, so that it may be turned upwards on the abdomen. The separation of the two mus- cles just mentioned is sometimes difficult, in consequence of their fibres being blended together, but a branch of the circumflex iliac artery will mark their intermuscular interval. The cremaster muscle is next to be divided along the cord, and to be reflected to the sides. Let the dissector then clean the surface of the transversalis muscle, without displacing its lower arched border; and trace with care the conjoined tendon of it and the internal oblique to show the EXTERNAL OR OBLIQUE HERNIA. 421 exact extent outwards. The fascia transversalis and the spermatic cord should be likewise nicely cleaned. Crossing the interval apparent below the border of the transversalis muscle, are the epigastric vessels, which lie close to the inner side of the internal abdominal opening, but beneath the fascia transversalis. A small piece of the fascia may be cut out to show the vessels. Inguinal Hernia. A protrusion of intestine through the lower part of the abdominal wall near Poupart’s ligament (the part answering to the inguinal region), is named an inguinal hernia. The escape of the intes- tine in this region is predisposed to by the deficiencies in the muscular strata, by the passage of the spermatib cord through the abdominal parietes, and by the existence of fossae on the inner surface of the wall. The gut in leaving the abdomen either passes through the internal ab- dominal ring with the cord, or is projected through the part of the abdom- inal wall between the epigastric artery and the edge of tlie rectus muscle. These two kinds of hernia are distinguished by the names external and internal, from their position to the epigastric artery; or they are called oblique and direct, from the direction they take through the abdominal wall. Thus, the hernia protruding through the internal abdominal ring with the cord is called external from being outside the artery, and oblique from its slanting course ; whilst the hernia between the edge of the rectus and the epigastric artery is named internal from being inside the artery, and direct from its straight course. External or Oblique Inguinal Hernia leaves the cavity of the abdomen with the spermatic cord, and traversing the inguinal canal, makes its exit from that passage by the external abdominal ring. Anatomy of the external hernia. To acquire a knowledge of the anatomy of this hernia it will be necessary that the space in which it lies (inguinal canal), the apertures by which it enters and leaves the wall of the abdo- men (abdominal rings), and the coverings it receives in its progress to the surface of the body, should be studied. The inguinal canal (fig. 140) is the interval between the flat muscles of the abdominal wall, which contains the spermatic cord in the male, and the round ligament in the female. Its direction is oblique down- wards and inwards, being nearly parallel to, but above Poupart’s ligament; and its length is about one inch and a half. Superiorly it ceases at the in- ternal abdominal ring ; and inferiorly it ends in the external abdominal ring. Towards the surface of the body the canal is bounded by the teguments, and the two oblique muscles in this way: — The skin with the subjacent fatty layer, and the aponeurosis of the external oblique, a, reach the whole length of the passage ; but the internal oblique, b, extends only along its outer third (half an inch). Towards the cavity of the abdomen the wall of the canal is constructed by the conjoined tendon of the internal oblique and transversalis, and by the deep membranous strata in the wall of the abdomen in this wise : — The conjoined tendon, ii, placed in front of the other structures, reaches along the inner two-thirds of the space (about an inch) ; and beneath or behind it come the fascia transversalis, G, the subperitoneal fat, and the peritoneum, in the order mentioned, which are continued all along the passage. Along the lower part, or the floor, the canal is limited by the union of the fascia transversalis with Poupart’s ligament, and by the fibres of the 422 DISSECTION OF THE ABDOMEN. ligament inserted into the pectineal line; whilst along the upper part its extent is determined only by the apposition of the muscles. In the female, the canal has the same length and boundaries, though it is usually somewhat smaller. In that sex it lodges the round ligament. The internal abdominal ring (fig. 140) is an aperture in the fascia transversalis, which is situate midway between the symphysis pubis and the iliac crest, and half an inch above Poupart’s ligament. It is oval in form, the extremities of the oval being directed upwards and downwards, and measures about half an inch; the fascia at its outer and lower parts is stronger than at the opposite sides. Fig. 140. I)issi;cTiox FOR Inguinal Hernia. (Illustrations of Dissections.) Muscles : Arteries : A. External otlique tendon, thrown down. a. Epigastric vessels. B. Internal oblique, the lower part raised. h. Offset of the circumflex iliac muscles, c. Cremaster muscle in its natural position. D. Transversalis muscle with a free border. F. Spermatic cord. G. Fascia transversalis. H. Conjoined tendon. Arching above and on the inner side of the aperture, is the lower border of the transversalis muscle, d, which is fleshy in the outer, but tendinous in the inner half. Below, it is bounded by Poupart’s ligament. On the inner side lie the epigastric vessels {a). This opening in the fascia transversalis is the inlet to the inguinal canal, and through it the cord, or the round ligament, glasses into the wall of the abdomen. The external hernia enters the canal the same spot. All the EXTERNAL OR OBLIQUE HERNIA. 423 protruding parts receive as a covering the prolongation from the margin of the opening. The external abdominal ring (fig. 135, is the outlet of the inguinal canal, and through it the spermatic cord reaches the surface of the body. This aperture is placed in the aponeurosis of the external oblique muscle, near the crest of tlie pubes ; and from the margin a prolongation is sent on the parts passing through it (p. 410). Course and coverings of the hernia. A piece of intestine leaving the abdomen with the cord, and passing through the inguinal canal to the surface of the body, will obtain a covering from every stratum in the lateral part of the wall of the abdomen, except from the transversalis muscle. It receives its investments in tliis order: As the intestine is thrust out- wards, it carries before it first the peritoneum and the subpeiltoneal fat, and enters the tube of the fascia transversalis, f (infundibuliform fascia), around the cord. Still increasing in size it is forced downwards to the lower border of the internal oblique muscle ; where it will have the cre- masteric fascia, c, applied to it. The intestine is next directed along the front of the cord to the external abdominal ring, and in passing through that opening receives the investment of the intercolumnar or spermatic fascia. Lastly, as the hernia descends towards the scrotum, it has the additional coverings of the superficial fascia and the skin. In a hernia which has passed the external abdominal ring, the cover- ings from without inwards are the following: the skin and the superficial fascia, the spermatic and cremasteric fasciae, the fascia transversalis, the subperitoneal fat, and tlie peritoneum or hernial sac. Two of the cover- ings, viz., the peritoneal and subperitoneal, originate as the gut protrudes, but the rest are ready formed around the cord, and the intestine slips in- side them. The different layers become much thickened in a hernia that has existed for some time. Diagnosis. If the hernia is small and is confined to the wall of the belly, it gives rise to an elongated swelling along the inguinal canal. If it has proceeded farther, and entered the scrotum, it forms a flask-shaped tumor with the large end below, and the narrow neck occupying the in- guinal passage. Whilst efforts are being made to force back a piece of protruded intes- tine during life, the direction of the canal, and the situation of the internal abdominal ring should be borne in mind. Seat of stricture. Lhe protruded intestine may be constricted at the internal abdominal ring; in the inguinal canal by the fleshy internal ob- lique muscle ; and at the external abdominal ring. The stricture is placed usually at the inner abdominal ring, and may be produced in two ways : either by a constricting fibrous band outside the narrowed neck of the tumor, or, by a thickening and contraction of the peritoneum itself at the inner surface of the neck. Division of stricture. To set free the intestine, an incision is made down to the internal abdominal ring ; and, all fibrous bands outside the peritoneum being divided, the intestine is to be returned into the abdo- men by gentle pressure. Supposing the intestine cannot be replaced in the abdomen after the previous steps have been taken, the surgeon proceeds to lay open the peri- toneum, and to divide the internal stricture, from within out, on a director 424 DISSECTION OF THE ABDOMEN. placed beneath it. With a view of avoiding the surrounding vessels, the cut is directed upwards on the front and mid-part of the hernia. Other designations. This kind of hernia has other names applied to it sometimes hy surgeons, according as it has passed certain points in the wall of the abdomen. If the intestine remains in the inguinal canal, the term bubonocele is applied to the swelling ; but if it has extended into the scrotum, the appellation scrotal rupture, or oscheocele, is given to the tumor. Varieties of the external hernia. There are two varieties of the oblique inguinal hernia (congenital and infantile), which are distinguished by the condition of the peritoneal covering. Congenital hernia. This kind is found for the most part in the infant and the child, though it may occur in the adult male. In it the tube of peritoneum, which accompanies the testicle from the abdomen in the foetus, remaining unclosed, the intestine descends into a sac already formed for its reception. As it takes the course of the inguinal canal, it will possess the cover- ings before enumerated for the external hernia ; and it passes at the first to the bottom of the scrotum, instead of being arrested at the top of the testis. With care it may be distinguished, whilst it is of moderate size, by its position in front of the testicle. For the seat, cause, and division of the stricture, refer to what is before stated for external hernia. Infantile hernia, is much rarer than congenital, and cannot be distin- guished from the common external hernia during life. It was first recog- nized in the young child, and received its name from that circumstance ; but, like the congenital, it may be met with in the adult. Its chief dif- ferential character is derived from the state of the peritoneum. The peritoneum has tlie following condition : — the tube of that mem- brane passing with the testicle in the foetus, is closed only at the internal abdominal ring, instead of being obliterated from that point down to the testicle, so that a large serous sac will be situate in front of the spermatic cord, and may occupy the inguinal canal. With this state of the perito- neum, should an external hernia with its coverings descend along the cord in the usual way, it will pass behind the unobliterated sac, like a viscus into serous membrane. In this way there will be two sacs ; an anterior (the tunica vaginalis), containing serum, and a posterior inclosing the intestine. The infantile hernia is first recognized during an operation by the knife opening the tunica vaginalis. The operator then proceeds to lay bare the neck of the hinder or hernial sac, and to treat the stricture of it as before described (p. 423). The Internal or Direct Inguinal Hernia escapes on the inner side of tlie epigastric artery, and has a straight course through tlie abdominal parietes. Its situation and coverings, and the seat of stricture, will be better understood after the examination of the part of the abdominal wall throiigh which it passes. Anatomy of the internal hernia. At the lower part of the abdominal wall is a triangular space (fig. 140) wliich is bounded by the epigastric artery on one side, the outer edge of the rectus muscle on the other, and the inner half of Pouj)art’s ligament below : it measures about two inches from above down, and one inch and a half across at the base. INTERNAL OR DIRECT HERNIA. 425 The constituents of the abominal wall in this spot are, the teguments; the strata of the muscles ; and the layers lining the interior of the abdo- men, viz., fascia transversalis, subperitoneal fat, and peritoneum. The muscles have the undermentioned arrangement: — The aponeurosis of the external oblique is pierced by an aperture (external abdominal ring) towards the lower and inner angle of the space through which the inguinal hernia is transmitted. The internal oblique and transversalis, which come next, are united together in the conjoined tendon ; as this descends to its in- sertion into the pectineal line, it covers the inner two-thirds (about an inch) of the space, and leaves uncovered about half an inch between its outer edge and the epigastric vessels, where the fascia transversalis appears. Any intestine protruding in this spot must make a new path for itself, and elongate the diderent structures, because there is not any opening by which it can descend, as in the external hernia. Further, the coverings of the hernia, and its extent and direction in the abdominal wall, must vary according as tlie gut projects through the portion of the space covered by the conjoined tendon, or through the part external to that tendon. Course and coverings of the hernia. The common kind of the internal hernia (inferior) passes through the part of the triangular space which is covered by the conjoined tendon. The intestine in protruding carries before it the peritoneum, the sub- peritoneal fatty membrane, and the fascia transversalis ; next it elongates the conjoined tendon, or as in a sudden rupture, separates the fibres, and escapes between them. Then the intestine advances into the lower part of the inguinal canal, opposite the external abdominal ring ; and passes through that opening on the inner side of the cord, receiving at the same time the covering of the fascias perrnatica. Lastly, it is invested by the superficial fascia and the skin. In number the coverings of the internal hernia are the same as those of the external ; and in kind they are the same, with this exception, that the conjoined tendon is substituted for the cremasteric fascia. The position of the openings in the abdominal wall should be kept in mind during attempts to reduce this kind of hernia ; and the straightness of the course of the internal, in comparision with the external hernia, should be remembered. Diagnosis. This rupture will be distinguished from external hernia by its straight course through the abdominal wall, and by the neck being placed close to the pubes. After this hernia has acquire d a large size, an examination during life cannot determine whether it began originally in the triangular space, or at the internal abdominal ring ; for as an external hernia increases, its weight drags inwards the internal idng into a line with the external, and in this way the swelling acquires the appearance of a direct rupture. Seat of stricture. The stricture in this form of hernia occurs most frequently external to the neck of the tumor, though it may be inside from thickening of the peritoneum ; and it may occasionally be found at the external abdominal ring. Division of the stricture. The neck of the tumor is to be laid bare, and all fibrous bands around it are to be divided without injury to the peritoneum ; but if, after this has been done, the intestine cannot be put backwards into the abdomen, the sac is to be opened, and the internal constricting band is to be divided directly upwards on a director. In the operation on. a large rupture appearing to be direct, the operator 426 DISSECTION OF THE ABDOMEN. sliOLild cut on the front and mid-part of the tumor, so as to avoid the epi- gastric vessels, whose lateral position cannot be known. Variety of internal hernia. Another kind of internal hernia (superior) occurs through that part of the area of the triangular space which is ex- ternal to the conjoined tendon. Its existence is determined by the unusual j)Osition of the obliterated hypogastric artery inside the abdominal wall (p. 427). Tlie intestine protrudes through the wall of the abdomen close to the epigastric artery, and descends along nearly the whole of tlie inguinal canal to reach the external abdominal ring ; so that the term “ direct” would not ai)ply strictly to this form of internal hernia. Coverings. As the gut traverses nearly the whole of the inguinal canal, it has exactly the same coverings as the external hernia, viz., the skin and the su})erficial fascia, the spermatic and cremasteric fascice, the fascia transversalis, and the subperitoneal fat and the peritoneum. Diagnosis. This form of internal hernia would be considered external during life from its course and its form ; and yet it must be remembered that the epigastric vessels are placed on the outer part of its neck, whilst in the hernia which it stimulates, they lie on the inner side. Its nature can be ascertained with certainty only after death. Seat of stricture. The constriction of the intestine will take place from similar causes, and at the same spots as in the external lieriiia. Division of the stricture. From an inability to decide always in the living body whether a small hernia is internal or external, the rule ob- served in dividing the stricture of the neck of the sac is, to cut down upon the mid-part of the tumor; and if it is necessary to open the peritoneum, to cut directly upwards, as in the other kinds of inguinal hernia. Umbilical Hernia, or exomphalos, is a protrusion of the intestine through or by the side of the umbilicus. It is very variable in size, and its course is straight through the abdominal wall. Coverings. The coverings of the intestine are few in number : They are the skin and the superficial fascia ; a prolongation from the tendinous margin of the umbilical opening ; together with coverings of the fascia transversalis, the subperitoneal fat, and the peritoneum. Over the end of the tumor the superficial fascia blends with the other contiguous struc- tures, and its fat disappears. If the hernia is suddenly produced, it may want the investment other- Avise derived from the edge of the umbilicus. Seat of stricture. The stricture on the intestine is generally at the margin of the tendinous opening in the abdominal wall ; and it may be either outside, or in the neck of the sac, as in the other kinds of hernia. It should be remembered that the narrowed neck is at the upper part and not in the centre of the swelling. Division of the stricture. The constriction may be removed by cutting externally the parts around the neck. Or if the sac is to be opened, the knife may be carried upwards in cutting through the stricture ; but there is not any vessel liable to injury in the operation. Other Forms of Hernia. At each of the other apertures in the parietes of the abdomen, a piece of intestine may be protruded, so as to form a hernial tumor. For instance there may be femoral hernia below Poupart’s ligament, Motli the femoral vessels ; obturator hernia through tlie thyroid foramen, with the artery of the same name ; and ischiatic hernia through the ischiatic notch. ANATOMY OF FEMORAL HERNIA. 427 The femoral hernia, as the most important, will be noticed presently ; but the student must refer to some sjjecial treatise for information re- specting the other abdominal liernim. Dissection. Tlie abdomen may be now opened to see the cords and the depressions on the posterior surface of the abdominal wall. A trans- verse cut may be made through the umbilicus across the front of the ab- domen ; and on holding up the lower half of the wall, fibrous cords will be seen ascending to the umbilicus from the pelvis. Cords of the abdominal wall. In the middle line is the prominence of the remains of the urachus, which reaches from the summit of the bladder to the umbilicus. On each side is another cord of the obliterated hypo- gastric artery ; this is directed from the side of the pelvis to the umbili- cus, and lies usually behind or close to the epigastric artery, near Poupart’s ligament. Fossw. With this disposition of the cords, two fossa? are seen near Poupart’s ligament, one on each side of the obliterated hy[)Ogastric artery ; tliey correspond with the situation of the internal and external abdominal rings, and with the places where the external and internal (common kind) hernia? occur. But occasionally the cord of the obliterated hypogastric is moved in- wards from the epigastric artery, to the line of junction of tlie outer with the inner two-thirds of the triangular space through which the direct hernia comes. In this position of the cord there will be three fossae on the lower part of the abdominal wall ; viz., an inner between it and the urachus, a middle one between it and the epigastric vessels, and an exter- nal outside the epigastric artery. And there may be one, two, or three inguinal hernim, on each side of the body, according to the depth of the fossa?, and the predisposition to protrusion of the intestine. Femoral Hernia. In this hernia the intestine leaves the abdomen below Poupart’s ligament, and descends in a loose membranous sheath around the femoral vessels. Only so much of the structures will be de- scribed here as can be now seen, the rest are noticed fully in the dissection of the thigh. Dissection. The dissection for the femoral hernia is to be made on the left side of the body. The lower portion of the abdominal wall is to be divided from the um- bilicus to the pubes. The peritoneum is to be detached from the inner surface of the wall near Poupart’s ligament, by means of a transverse cut just above that band; and is to be raised from the iliac fossa. The layer of the subperitoneal fat is to be separated in the same way, but before this can be done, it will be necessary to cut through the spermatic cord at the abdominal ring; as this layer is raised, some lymphatic glands will be laid bare by the side of the iliac vessels. Any loose tissue remaining is to be taken away to show the upper opening of the membranous crural sheath containing the femoral vessels, and the interval (crural ring) on their inner side (tig. 141). In this dissection the genito-crural nerve is seen on the iliac artery. Afterwards the fascia transversalis and the iliac fascia are to be traced to Poupart’s ligament, to see the part that each takes in the production of the crural sheath. Anatomy of femoral hernia. The membranes concerned in the femoral hernia are, the peritoneum; the subperitoneal fat ; the transversalis and 428 DISSECTION OF THE ABDOMEN. iliac fasciae lining the interior of the abdominal cavity, with the sheath on the femoral vessels to which they give origin at Poupart’s ligament. The peritoneum lines the inner surface of the abdominal wall, witliout having any aperture for the escape of the intestine; and its thinness and weakness are apparent now it is detached. The suhperitoneal fat extends as a continuous layer beneath the perito- neum, but is thickest and most fibrous at the lower part of the abdomen, where the iliac vessels pass under Poupart’s ligament. At that spot it extends ov^er the upper opening of the membranous sheaths around the vessels; and internal to the vein, it covers the space of the crural ring, as well as a lymphatic gland which occupies that space. Where this layer stretches over the crural ring it is named by M. Clo- quet septum crurale ; and it is described by him as being concave towards tlie abdomen, and convex towards the thigh. An inguinal gland is gen- erally attached to its under surface. The fascia transversalis has been before noticed (p. 417). At Pou- part’s ligament it joins tlie iliac fascia, outside the situation of the large iliac artery (fig. 141); but internal to that spot it is continued downwards to the thigh in front of the femoral vessels, and forms the anterior part of the crural sheath. The iliac fascia covers the iliacus muscle, and lies beneath tlie iliac vessels. At Poupart’s ligament its disposition is similar to that of the transversalis fascia; for, external to the iliac vessels, it joins the fascia transversalis along the line of the ligament ; but opposite the vessels it is prolonged into the posterior part of the crural sheath. Fig. 141. Muscles : A. Iliacus covered by the iliac fascia. B Rectus. C. Transversalis, covered by the traus ver- salis fascia. D. Crural ring. E. Gimbernat’s ligament. Vessels : а. Iliac artery. б. Iliac vein. c. Epigastric branch. d. Circumflex iliac. e. Obturator, with its nerve. /. Small branch joining obturator and epi- gastric arteries. View of the Parts concerned in Femokal Hernia (Quain’s plates). The crural sheath is a loose membranous tube, which incloses the femo- ral vessels as they enter the thigh, and is obtained from the fascim lining tlie abdomen. Its anterior half is continuous with the fascia transversalis, and its posterior is derived from the fascia iliaca. The sheath is not en- tirely filled by the vessels, for a space (crural ring) exists on the inner side of the vein, through which the intestine descends in femoral hernia. The crural ring (fig. 141, ®) is referred to also in the dissection of tlie thish, but its boundaries are better seen in the abdomen. It is the inter- val in the sheath, at the inner side of the femoral vein, which is about half an inch wide, and is filled by a lymphatic gland. Bounding it inter- nally, are Gimbernat’s ligament, e, and the conjoined tendon; and limit- STRICTURE OF FEMORAL HERNIA. 429 ing it externally is the femoral vein (b) without the intervention of the sheath. In front is Poupart’s ligament, with the deep arch ; and behind is the pubes, covered by the pectineus and the fascia lata. Along the front of the space, but at some little distance from it, lies the spermatic cord in the male, and the round ligament in the female. Two of the boundaries, anterior and inner, are firm and sharp-edged, though their condition varies with the position of the limb; for if the thigh is raised and approximated to its fellow, those bounding parts will be relaxed. Position of vessels around the ring (fig. 141). On the outer side is the femoral vein {b) ; and above this are the epigastric vessels (c). In front is a small branch (pubic) from the epigastric artery to the back of the pubes ; and the vessels of the spermatic cord may be said to be placed along the anterior aspect of the ring. The ring is bounded in the male by vessels in front and on the outer side. But in some bodies the obturator artery takes origin from the epigastric, and lies along the ring as it passes to the pelvis. It may have two posi- tions with respect to the crural ring : — either it is placed close to the iliac vein, so as to leave the inner side of that space free from vessels ; or it arches over the aperture, descending on the inner side at the base of Gim- bernat’s ligament ; in this last condition the ring will be encircled except at the posterior part. Course of femoral hernia. The intestine leaves the abdomen by the opening of the crural ring ; and it descends internal to the vein in the large crural sheath, as far as the saphenous opening in the thigh, where it projects to the surface. Coverings. In its progress the intestine will push before it the peri- toneum, and the subperitoneal fat (septum crurale) ; and it will displace, or cause to be absorbed, the gland which fills the crural ring. Having reached the level of the saphenous opening, the intestine carries before it the inner side of the crural sheath, and a layer called the cribriform fas- cia ; and, lastly, it is invested by the teguments of the thigh. The dissec- tion of the thigh may be referred to for fuller detail. Seat of stricture. The stricture of a femoral hernia is placed opposite the base of Gimbernat’s ligament, or lower down at the margin of the saphenous opening in the thigh. And the constriction may be caused either by a fibrous band outside the upper narrow end of the tumor, or by the thickening of the peritoneum inside that j art, as in inguinal hernia. Division of the stricture. To free the intestine from the constricting fibrous band arching over it, an incision is to be made down to the neck of the sac at the inner and upper part. And to relieve the deep stricture within the neck of the sac, the peri- toneal bag is to be opened and a director introduced, and the knife is to be carried horizontally inwards, or upwards and inwards, through the thickened sac and a few fibres of the edge of Gimbernat’s ligament. Danger to vessels. Wlien the incision is made upwards and inwards to loosen the constricting band in the neck of the tumor, there will not be any vessel injured unless the cut should be made so long as to reach the spermatic cord in the male, or the small pubic branch of the epigastric artery. And when the incision is made directly inwards with the same view, there is not usually any vessel in the way of the knife. But in some few instances (once in about eighty operations, Lawrence), the obturator artery 430 DISSECTION OF THE ABDOMEN. takes its unusual course in front of and on the inner side of the neck of the hernia, and will be before the knife in the division of the stricture. As this condition of the vessel cannot be recognized beforehand, the sur- geon will best avoid the danger of wounding the artery by a cautious and sparing use of the knife. Section III. CAVITY OF THE ABDOMEN. The abdominal cavity is the space included between the spinal column behind, and the visceral arches of the vertebroe with their intervening muscles in front. It is lined by a serous membrane (peritoneum), and contains the digestive, urinary, and generative organs, with vessels and nerves. Dissectioji. To prepare the cavity for examination, the remainder of the abdominal wall above the umbilicus is to be cut, along the left side of the linea alba, as far as the xiphoid cartilage. The resulting flaps may be thrown to the sides. Size and form. This space is the largest in the body. It is ovoidal in form, with the ends u[)wards and downwards, so that it measures more in the vertical than the transverse direction ; and it is much wider supe- riorly than inferiorly. Boundaries. Above it is limited by the diaphragm ; below by the recto-vesical fascia and the levatores ani, and the structures closing the outlet of the pelvis: both these boundaries are concave towards the cavity, and are in part fleshy, so that the space will be diminished by their con- traction and flattening. In front and on the sides the parietes are partly osseous and partly muscular : — thus towards the upper and lower limits is the bony frame- work of the skeleton, viz., the ribs in one direction and the pelvis in the other ; but in the centre are stretched the muscles of the abdominal wall. Behind is placed the spinal column with the muscles contiguous to it, viz., the psoas and the quadratus lumborum. Alterations in size. The dimensions of the cavity are influenced by the varying conditions of the boundaries. Its depth is diminished by the contraction and descent of the diaphragm, and the contraction and ascent of the levatores ani ; and the cavity is restored to its former dimensions by the relaxation of tliose muscles. The width is lessened by the contraction of the abdominal muscles ; but it is increased, during their relaxation, by the action of the diaphragm forcing outwards the viscera. The greatest diminution of the space is eflected by the simultaneous contraction of all the muscular boundaries, as in the expulsion of the excreta. Division of the space. A division has been made of the space into the abdomen proper and the cavity of the pelvis. The abdominal portion reaches from the diaphragm to the brim of the pelvis, and lodges the alimentary tube and its appendages, together with the kidneys. CONNECTIONS OF STOMACH.. 431 Tlie 'pelvic portion is situate below the brim of the pelvis, and contains chiefly the generative and urinary organs. The following description concerns the part of the cavity between the diaphragm and the brim of the pelvis. Towards the end of the dissection of the abdomen, the pelvic portion will receive a separate notice. Regions. The upper })art of the abdominal cavity is divided into re- gions by lines extended between certain points of the parietes. If two circular lines are carried round the body, so that one shall be opposite the cartilage of the nintli rib, and the other on a level with the most prominent point of the crest of the hip-bone, the cavity will be divided into tliree circles or zones, upper, middle, and lower. Each of these circles has been further subdivided into three by a line, on each side, from the cartilage of the eighth rib to the centre of Poupart’s ligament. The piece marked off’, on each side, from the three circles by the vertical line is named respectively, from above downwards, hypochon- driac, lumbar, and iliac ; whilst the central part of each circle is desig- nated from above down, epigastric, umbilical, and hypogastric. In addition, the middle and lower part of the hypogastric space is named pubic region, whilst the contiguous portions of the hypogastric and iliac parts constitute the inguinal region. Contents and their position. The alimentary tube, the liver, pancreas, spleen, and kidney, occupy the abdomen proper. The alimentary tube presents differences in form, and is divided into stomach, small intestine, and large intestine ; and the two last are further subdivided, as it will afterwards appear. The several viscera have the following general position : The small intestine is much coiled, and occu- pies the greater part of the cavity ; whilst the great intestine arches around it. Botli are fixed in position by pieces of the serous lining. Above the arch of the great intestine are situate the stomach, the liver, the spleen, and the pancreas ; and below it, is the convoluted small gut. Behind the large intestine, on each side, is the kidney with its excretory tube. Superficial view of the contents. On first opening the abdomen the following viscera appear: On the right side is the liver, which is partly concealed by the ribs. On the left side a piece of the stomach is visible ; but this viscus lies for the most part beneath the ribs and the liver. De- scending from the stomach is a fold of peritoneum (the large omentum), which reaches to the pelvis, and conceals the small intestine : in some bodies the omentum is raised into the left hypochondriac region, and leaves the intestine uncovered. If the bladder is distended, a small part of it may come into view just above the pelvis, but commonly it is not seen. Before the natural position of the viscera is disturbed, their situation in the different regions of the abdomen, and their connections with surround- ing parts should be examined. CONNECTIONS OF THE VISCERA. The stomach (fig. 142, a) intervenes between the gullet and the small intestine, and is partly retained in position by pieces of the serous mem- brane. It is somewhat of a conical form, witli the larger end to the left side ; and it occupies the left hypochondriac, the epigastric, and part of the right hypochondriac region. 432 DISSECTION OF THE ABDOMEN. Connections of the Liver, Stomach, Spleen, and Large Intestine, the small intestine having been taken away. a. Stomach, and 5, oesophagus. h. Transverse. c and ti. Right and left lobes of ihe liver, with i. Descending, and k, sigmoid flexure of the e, the suspeusoi’y ligament. colon. /. Caecum. 1. Duodenum. y. Ascending colon. m. Spleen. np the tliuphragm, and encroaches on the space for the heart and the left lung. The right extremity ends in the small intestine, and reaches towards the gall bladder ; it is in contact with the under part of the liver. The anterior surface touches, from left to right, the diapliragm, the ab- dominal wall, and the liver ; and tlie posterior surface corresponds with tlie pancreas, the pillars of the dia[)hragm, tlie aorta and vena cava, and the solar plexus. The up[)er border is connected to the liver by a process of peritoneum, the small omentum ; and the lower border gives attachment to another peritoneal fold, the great omintum or epiploon, which floats freely over the intestine. Tlie form, and the connections of the stomach with the surrounding parts will vary with tlie size. For when the viscus is empty it is flattened, At the left end it receives the cesophagus (/;), by which it is firmly fixed to the diaphragm ; here it lies beneath the ribs, and is in contact with the spleen (/??), to which it is connected by a fold of peritoneum (splenic omentum) : when this part of the stomach is distended it pushes Fig. 142. CONNECTIONS OF INTESTINES. 433 its surfaces looking forwards and backwards, and its borders upwards and downwards ; but when distended, it becomes somewhat circular, and makes a rotatory movement, so as to bring forwards the border usually lowest, and to turn upwards that surface which is directed forwards at other times. The position and connections of the stomach may be altered by varia- tions in the size of any of the surrounding organs, or by the accumulation of fluid in the chest, or in the belly. The stomach may be dragged down likewise by the great omentum entering a hernia ; or it may be forced down towards the pelvis by the pressure of tight stays. In these different changes in position, the right end moves more than the left, because it is attached mainly by peritoneum to the parts around. The small intestine (intestinum tenue) reaches from the stomach to the right iliac region, where it ends in the large intestine. It is divided into three parts, duodenum (twelve fingers’ length), jejunum, and ileum : of the last two, the former receives its name from its em[)ty condition, and the latter from its numerous coils. The duodenum (fig. 142, 1) cannot be satisfactorily seen at present, and it will be examined afterwards (p. 445). 'The jejunum and ileum (fig. 143) begin on the left side of the second lumbar vertebra, without any distinct mark of separation from the duode- num. Two-fifths of the intestine belong to the jejunum, and the remain- ing three-fifths to the ileum. This part of the intestinal tube forms many convolutions in the umbili- cal, hypogastric, lumbar, and iliac regions of the abdomen ; and it de- scends oftentimes, but more frequently in the female, into the cavity of tl e pelvis. In front of the convolutions is the great omentum. Beyond the duodenum the intestine is fixed posteriorly to the spine by a process of peritoneum named the mesentery, which contains the vessels and nerves. Surrounding the jejunum and ileum is the large intestine or colon : but on the left side of the body the colon is concealed by the small intestine. The large intestine^ or the colon (fig. 142), is sacculated, and is more fixed than the jejunum and ileum. It begins in the right iliac region in a rounded part or head (caput caecum coli), and ascends to the liver through the right iliac, lumbar, and hypochondriac regions. Crossing then the abdomen below the stomach, it reaches the left hypochondriac region ; and it lies in this transverse part of its course between the epigastric and um- bilical regions, or altogether in the latter. Finally, it descends, on the left side, through the regions corresponding with those it occupied on the right, and forms a remarkable bend (sigmoid flexure) in the left iliac fossa ; then becoming straighter it passes through the pelvis to end on the surface of the body. It is divided into six parts, viz., ccecum, ascending colon, transverse colon, descending colon, sigmoid flexure, and rectum. The ccecum (fig. 142,/) (caput caecum), or the commencement of the colon, is placed in the right iliac fossa, in which it is fixed by the perito- neum being stretched over it. In front usually are convolutions of the sttiall intestine, but when it is distended it touches the abdominal wall. Behind, it rests on the iliac fascia, only fatty and areolar tissues interven- ing. On the inner side it is joined by the small intestine ; and it presents interiorly a worm-like piece — the vermiform appendix. Sometimes the peritoneum surrounds the caecum, and attaches it by iv process to the abdominal wall. The ascending colon (fig. 142, g') reaches from the caecum to the under 28 484 DISSECTION OF THE ABDOMEN. surface of the liver, on the right of the gall bladder. It lies against the quadratus lumborum inferiorly, but higher up it is placed in front of the kidney. To its inner side are the convolutions of the small intestine. The peritoneum fixes the colon immovably to the wall of the abdomen, and surrounds commonly about two-thirds of the circumference ; but it may encircle the tube, and form a fold behind, as in the caecum. The transverse colon (fig. 142, h) passes obliquely upwards and to the left, along the curvature of the stomach, as far as the spleen ; in this course it is deeper at each end than in tlie middle, and forms the arch of the colon by being thus bent. Above the arch are placed the liver and the gall bladder, the stomach and the spleen : and below, is the small intestine. In front lies the great omentum ; and behind is a long process of peritoneum, the transverse meso-colon, which attaches it to the back of the abdomen, and contains the vessels and nerves. The transverse colon is more movable than any other part of the large intestine, — its peritoneal fold allowing it to be raised on the margin of the ribs. Small pieces of peritoneum, containing fat, the appendices epipldirce^ are attached along it. The descending colon (fig. 142, i') commences below the spleen, and reaches to the left iliac fossa. At first it is placed deeply in the left hypo- chondriac region ; and its whole course is deeper than that of the right colon. In front of it are the convolutions of the small intestine; and be- hind it are the diaphragm, the outer part of the kidney, and the quadratus lumborum. This part of the intestine is smaller than either the right or the trans- verse portion, and is less surrounded, commonly, by the peritoneum ; but its upper end is attached to the diaphragm by a firm process (pleuro-colic) of that membrane. The sigmoid flexure of the colon (fig, 142, Ic) is lodged in the left iliac fossa, to which it is attached by a process of the peritoneum, the sigmoid mewso-colon, but it often hangs in the cavity of the pelvis. The intestine makes two turns like the letter S, and has obtained its name from that circumstance. Its extent is from the crest of the hip bone to the sacro- iliac articulation, where it ends in the rectum. It is concealed by the small intestine, which is directed more to the left than the right side. The rectum^ or the termination of the large intestine, which is contained in the pelvis, will be examined in the dissection of that cavity. The liver (fig. 142, c, d) is situate in the right hypochondriac, and epi- gastric regions, and reaches slightly into the left hypochondriac. Pieces of peritoneum (ligaments) retain it in place. The upper surface, convex, is turned to the vault of the diaphragm, and is divided into two parts by the suspensory ligament {e) ; the right ])ortion, more prominent than the left, reaches to the level of the fifth in- tercostal space. The under surface is in contact with the stomach and the duodenum, with the ascending colon, and with the right kidney and suprarenal body ; attached to this surface is a fold of the peritoneum (small omentum), containing the hepatic vessels. The anterior border is thin, and lies in the adult male usually within the margin of the ribs, but in women and children it reaches below that line. The gall bladder projects beyond this edge. The posterior border is thick, and is connected to the diaphragm by certain ligaments or pieces REFLECTIONS OF PERITONEUM. 435 of the peritoneum ; it lies on tlie large vessels (aorta and cava) and on the pillars of the diaphragm. The liver changes its situation with the ascent and descent of the dia- phragm in respiration ; for in inspiration it descends, and in expiration it regains its former level. In the upright and sitting postures, too, this viscus descends lower than in the horizontal condition of the body ; so that when the trunk is erect, the anterior border may be felt underneath the edge of the ribs, but when the body is reclined it is withdrawn within the margin of the thorax. The connections of the liver with the surrounding parts may be changed by the growth of tumors, by collections of fluid in the chest or in the abdomen, or by constricting the space for its lodgment, as in tight lacing. The spleen (fig. 142, m) lies deeply in the left hypochondrium, between the stomach and the ribs, and is connected by peritoneum to the great end of the stomach on the one side, and to the diaphragm on the other. Its position is almost vertical. The outer surface is convex, and touches the diaphragm opposite the ninth, tenth, and eleventh ribs. At the inner surface, which is concave, the vessels enter (p. 465), and to it is attached a process of peritoneum, the gastro-splenic omentum : the part in front of the vessels touches the stomach ; and the part behind them is in contact with the tail of the pan- creas, the suprarenal capsule, and the left crus of the diaphragm. Below the spleen is a transverse piece of the peritoneum (pleurocolic fold), the kidney, and the beginning of the descending colon. When the stomach is distended the spleen is somewhat behind it. The kidney should be examined on the left side of the body, so that the duodenum may not be displaced. In order that it may be seen, the de- scending colon and the peritoneum must be separated from the abdominal wall, and its casing of fat should be torn through. This viscus is surrounded with fat, and is situate in the lumbar region opposite the last dorsal, and the upper two or three lumbar vertebra3. Its position is somewhat oblique, and the upper end is nearer than the lower to the spinal column. In front of the kidney are the peritoneum and the colon ; and behind it are the quadratus lumborum and psoas muscles, with the diaphragm and the last rib. Above each kidney and resting on it, is the suprarenal cap- sule. The inner border looks to the spine and receives the vessels. Difference on opposite sides. The right kidney is placed rather lower than the left ; it reaches as high as the lower border of the eleventh rib, whilst its fellow is opposite the upper border of the corresponding rib. In front of the right, besides the common connections before specified, is the duodenum : and before the left one is the lower end of the spleen. Above the right is the liver, and above the left the spleen. The connections of the pancreas may be omitted for the present. This viscus is described at page 446. THE PERITONEUM. This is the largest serous membrane in the body. Like other mem- branes of the kind it is a closed sac in the male, but in the female its cavity is continuous with the canals of the Fallopian tubes. One part of it lines the wall of the abdomen (parietal layer), and another is reflected over the different viscera (visceral layer), except where the vessels enter. 436 DISSECTION OF THE ABDOMEN. The inner surface is smooth ; but the outer is rough, when it is detached from the parts with which it is naturally in contact. The membrane forms processes or folds as it passes from viscus to viscus along the ves- sels ; and the folds attaching the viscera to the abdominal wall consist lor the most part of two layers, one on each side of the vessels. The continuity of the sac may be traced in a horizontal and a vertical direction. Horizontal circle around the abdomen. The membrane, when followed outwards from the umbilicus, surrounds partly the large intestine on the left side, and fixes it to the abdominal wall. From the colon it may be traced over the kidney as far as the middle line, where it is reflected along the front of the vessels supplying the small intestine, thence around the intestine, and back to the spine along the same vessels. Lastly, it may be pursued outwards to the right kidney, to the colon which it encircles like the left, and along the wall of the abdomen to the umbilicus. The piece of membrane fixing the colon on each side to the abdominal wall, is named meso-colon, and that attaching the small intestine is the mesentery. Vertical circle from above downivards. From the under’surface of the liver the peritoneum may be followed along the hepatic vessels, one piece before and the other behind them to the upper border of the stomach, the two forming the small omentum. At the stomach the two pieces disunite, one passing before, and the other behind it; but beyond that viscus they are applied to each other to form the great omentum or epiploon. After descending in contact to the lower part of the abdomen they bend back- wards, separating to inclose the transverse colon like the stomach, and they are then continued to the spine, giving rise to the transverse meso- colon. At the attachment of the transverse meso-colon to the abdominal wall, the two companion pieces part from each other — one passing up- wards, the other downwards.^ The ascending piece is continued in front of the pancreas and the pillars of the diaphragm, and blends with the peritoneum on the under surface of the liver. The descending piece or layer may be follow’ed from the transverse meso-colon over the duodenum and the great vessels on the spine (aorta and cava), till it meets with the artery to the small intestine, along which it is continued to form the mesentery, as before explained in tracing the peritoneum in a circular direction. From the root of the mesenteric artery the peritoneum descends to the pelvis, and covers partly the viscera in that cavity. For instance, sur- rounding the upper part of the rectum, it attaches this to the abdominal wall by the meso-rectum ; next, it is continued forwards between the rec- tum and the bladder in the male, or between the rectum and the uterus in the female, where it forms a pouch. Thence it passes from the pelvis over the back and sides of the bladder. Lastly, the serous membrane is continued to the inguinal region, where it presents the fossa^. before alluded to (p. 427); and it can be traced up- wards on the wall of the abdomen, and over the diaphragm and upper surface of the liver, to the under surface of this viscus. ’ Sometimes the two pieces ascend over tlie transverse colon, being slightly attached to it and the transverse meso-colon, as high as the pancreas before they separate. In that case the descending layer would form a distinct mesentery for the transverse colon, like that for the small intestine. REFLECTIONS OF PERITONEUM. 437 Folds of the Peritoneum. After tracing the continuity of the serous sac over the viscera, the student is to learn the chief processes or folds of the membrane in connection with tlie alimentary tube. The pieces of the peritoneum fixing the liv'erwill be examined afterwards; and the processes on the viscera of the pelvis will be seen with the dissection of that cavity. Folds on the stomach. The processes connected with the stomach are named omenta. They are three in number — one, small omentum, is at- tached to the upper curve; another, great omentum, to the lower curve; and the third, splenic omentum, is fixed to tlie great end of the viscus. The small or gastro-hepatic omentum is stretched between the under surface of the liver and the upper border of the stomach, and contains the vessels and nerves of the liver. It is formed by two pieces of peritoneum, as before explained, and presents a free border on the right side. Behind it is the space called foramen of Winslow. Its lower edge is fixed to the small curve of the stomach; whilst its upper border is attached to the transverse fissure, as well as to the posterior half of the longitudinal fissure of the liver, blending behind with the left lateral ligament of that viscus. The gastro-colic or great omentum is the largest fold of the peritoneum, and consists of two pieces. It is attached above to the spleen and the lower border of the stomach, and descends in front of the large intestine, but lower on the left than the right side of the body. At the lower part of the abdomen the process is bent backwards, and returns to the spine, the pieces of which it is composed separating to inclose the transverse colon. The anterior part of the omental fold is separated from the poste- rior by a space (cavity of the omentum). Between its layers are contained some fat, vessels, and nerves; and the power of detaching the one layer from the other diminishes with the in- crease of the distance from the stomach, until below tliey are not to be separated, and the membrane they form is thin and net-like. Cavity of the omentum. When an opening is made through the great omentum near the stomach, and this viscus is raised, a space is seen to extend upwards to the liver, and downwards into the omentum: this is the omental cavity. In front the space is bounded by the small omentum, the stomach, and the anterior part of the great omentum. Behind it, are the posterior part of the great omentum, the transverse colon, and the ascend- ing layer of the transverse meso-eolon. This space communicates with the rest of the peritoneal cavity, through a hole (foramen of Winslow), behind the small omentum. If the sac of the omentum were perfect, it could be inflated through the foramen of Winslow. Supposing it to be detached and removed, there would not be any membrane in the way of the vessels reaching the difler- ent viscera; and it may be readily conceived how the peritoneum could be replaced over the viscera, and around the vessels without being perfo- rated by them. ^\\o, foramen of Winslow is the space behind the small omentum, through which the omental bag opens into the general cavity of tlie peri- toneum. In front of it is the small omentum, and behind, are the vena cava and the spine. Above it is the liver (lobulus Spigelii), and below is the duodenum. The splenic omentum reaches from the great end of the stomach to the concave surface of the spleen, and does not consist usually of two strata or 438 DISSECTION OF THE ABDOMEN. pieces, like the other omenta. It covers the vessels passing between the two viscera, and is continued interiorly into the great omentum. Folds on the large intestine. The large intestine is connected to the wall of the abdomen by processes of the peritoneum (meso-colic), which are formed of two pieces, like the other folds, thougli they are at some distance from each other. Each part of the colon has a separate meso- colon attaching it, thus there is an ascending, a transverse, a descending, and a sigmoid meso-colon. The caecum is fixed by a meso-cjecum, and the rectum by a meso-rectum. The meso-ccecum attaches the caput caecum coli to the right iliac fossa. Usually the peritoneum does not surround the gut so as to form a fold be- hind it, but in some bodies the serous membrane furnishes a suspensory process to this part of the intestine. By the ascending and descending meso-colon the ascending and the descending part of the colon are kept in place. In these folds, as in that of the cKcum, the peritoneum does not commonly surround the intestine, though it may meet behind the gut and form processes of some length. The upper end of the left colon has a distinct fold (pleuro-colic), fixing it to the wall of the abdomen. Attached by a wide part to the diaphragm opposite the eleventh or tenth rib, it passes transversely below the spleen, and forms the lower boundary of a hollow in which the spleen rests. The transverse meso-colon is a more perfect fold than either of the others connected witli the large intestine, and serves as a partition between the small intestine and the stomach, liver, and spleen. By one side it is fixed to the colon, and by the other to the abdominal wall below the pan- creas. It incloses the vessels of the colon between its layers. The sigmoid meso-colon is a long process of the serous membrane, and attaches the sigmoid flexure of the colon to the left iliac fossa. ■ The meso-rectum contains the hemorrhoidal vessels, and connects the rectum to the front of the sacrum. Small processes of the peritoneum are attached along the tube of tlie great intestine, chiefly to the transverse colon ; they are the appendices epipldicce, and contain fat. Folds to the small intestine. The small intestine is not enveloped by the peritoneum after the same manner throughout. For whilst the jejunum and ileum are attached to the abdominal wall by one process (mesentery), the duodenum has special connections with the serous membrane. Serous covering of the duodenum. The first part of tlie duodenum is surrounded by peritoneum, like the stomach. The second part is covered only in front. And the last part, which crosses the aorta, is but sliglitly in contact with the serous membrane ; for it lies at first between the strata of the transverse meso-colon, and then beneath the superior mesen- teric vessels. Fold of the jejunum and ileum. The mesentery supports the rest of the intestine, and is stronger than any other piece of the serous membrane. Its inner end is narrow, and is attached to the s])ine from the left side of the second lumbar vertebra to the junction of the right hip bone with tlie sacrum. The other end of the fold is wide, and is connected with the intestine. Between its two layers are the superior mesenteric vessels and nerves, with lympliatic glands and lacteals. Ligaments of the liver. Along the upper part is a suspensory process of the peritoneum, and there is a wide piece along the posterior border. UPPER MESENTERIC VESSELS. 439 The suspensory or falciform ligament is placed between the upper con- vex surface of the liver and the parietes of the abdomen. It is triangular in shape, with its base forwards. The lower border is concave, and is attached to the liver; whilst the upper border is convex, and is connected to the abdominal wall, on the right side of the linea alba, and to the under part of the diaphragm. In its base or free part is the remains of the um- bilical vein, which is named the round ligament. Tliis fold allows the umbilical vein to reach the liver without piercing the peritoneum ; and with a little care the dissector will be able to detach the serous membrane from the vein, and to trace it on each side into the suspensory ligament. The coronary ligament is a short but wide process of the peritoneum, which connects the hinder part of tlie liver to the diaphragm. It reaches all across the liver, but at each side it is enlarged, and forms a triangu- larly-shaped piece ; to these larger portions of it the terms right and left lateral ligaments have been applied. The left lateral ligament is attached to the liver above the edge of the left lobe, and is formed by two pieces of peritoneum, which are in contact; it lies in front of the oesophagean opening in the diaphragm. The right lateral ligament lies deeply in the hypochondriac region, in front of the vena cava inferior : it consists of two pieces of peritoneum not touching each other. MESENTERIC VESSELS AND SYMPATHETIC NERVE. Directions. The vessels and nerves (mesenteric) which are distributed to the greater part of the alimentary tube, may be first dissected. After these have been examined, and the connections of the aorta and vena cava have been learnt, most of the intestine can be taken out to give room for the display of the viscera in the upper part of the abdomen. Mesenteric Vessels. The superior and inferior mesenteric arteries are two large branches of the aorta, which supply the intestine, except a part of the duodenum and the lower end of the rectum. Each is accom- panied by a vein, and by a plexus of the sympathetic nerve. Dissection (fig. 143). For the dissection of the superior mesenteric vessels and nerves, the transverse colon and the great omentum are to be placed on the margin of the ribs, and one layer (anterior) of the mesen- tery is to be removed. Whilst tracing the branches of the artery to the small intestine, corresponding veins, and offsets of the sympathetic nerve on the arteries, will be met with ; these last are removed in cleaning the vessels. Mesenteric glands and a few lacteal vessels will come into view at the same time. The branches from the right side of the vessel to the large intestine are to be next followed : and after all the branches have been cleaned, the trunk of the artery should be traced back beneath the pancreas. The plexus of surrounding nerves should be also defined. The superior mesenteric artery (fig. 143, a) supplies branches wholly to the small intestine beyond the duodenum, and to half the large intes- tine, viz., as far as the end of the transverse colon. Arising from the aorta near the diaphragm, the vessel is directed down- wards between the layers of the mesentery, forming an arch with the con- vexity to the left side, and terminates in offsets to the caecum and the end of the small intestine. At first the artery lies beneath the pancreas and 440 DISSECTION OF THE ABDOMEN. the splenic vein ; and as it descends to the mesentery it is placed in front of the duodenum and the left renal vein. This vessel is surrounded by the mesenteric plexus of nerves, and is accompanied by the vein of the same name. Branches. Whilst the vessel is covered by the pancreas it gives a small branch to that body and the duodenum. Its other branches are intestinal: those from the left or convex side of the vessel (rami intestinales) are fur- nished to the jejunum and ileum ; and those from the opposite side supply the colon, and are named colic arteries. Fig. 143. Superior Mesenteric Artery and its Branches (Tiedemann). a. Superior mesenteric. d. Eight colic. &. Inferior pancreaiico-duodenal. c. Ileo-colic. c. Middle colic. /. Intestinal branches to the jejunum and ileum. a. payicreatico-duodenal branch (inferior) is of small size (fig. 143, h)\ after giving twigs to the pancreas, it runs to the right along the con- cavity of the duodenum, and anastomoses with the other duodenal branch (p. 448). b. The intestinal branches for the jejunum and ileum (fig. 145,/) are about twelve in number, and pass from the left side of the artery between the layers of tlie mesentery. About two inches from their origin the branches bifurcate, and the resulting pieces unite witli similar offsets from the collateral arteries, so as to form a series of arches. From the con- vexity of the arclies other branches take origin, which divide and unite as before. This [)rocess is repeated four or five times between the origin LOWER MESENTERIC VESSELS. 441 and the distribution, but at each branching the size of the vessels dimin- ishes. From the last set of arches twigs are sent to the intestine on both aspects of the tube, and anastomose, round it. The branches of the large intestine are three in number, ileo-colic, right colic, and middle colic arteries. c. The ileo-colic artery (o) arises from the right side of the trunk, and divides at the caecum into brandies which encircle the head of the colon. A descending offset is distributed to the lower part of the ileum, and to the caecum and the vermiform appendix ; whilst an ascending offset sup- plies the beginning of the ascending colon, and anastomoses with the right colic artery. d. The right colic artery (c?) is commonly an offset of the preceding, instead of a separate branch from the trunk. Near the ascending colon it divides into ascending and descending pieces, which anastomose with the ileo-colic artery on one side, and with the middle colic on the other. e. The middle colic branch (c) springs from the upper part of the artery, and entering between the layers of the transverse meso-colon divides into two diverging branches : — the right one anastomoses with the artery to the ascending colon, and the left inosculates on the descending colon with a left colic branch (fig. l44, c) of the inferior mesenteric artery. The intestinal twigs are united in arches before entering the gut, like those to the small intestine. The superior mesenteric vein (fig. 146, b) commences in that part of the intestinal tube to which the artery is distributed. Its radicles unite into one trunk, which accompanies the artery beneath the pancreas, and there joins the splenic vein to form the vena portae. At the lower border of the pancreas it receives the right gastro-epiploic branch of the stomach, and the pancreatico-duodenal veins (fig. 146, c). The mesenteric lymphatic gands are numerous between the layers of the mesentery. An upper group lies by the side of the artery, and contains the largest glands ; and a lower group, near the intestine, is lodged in the intervascular spaces. The chyliferous vessels of the small intestine, and the absorbents of the part of the large intestine su})plied by the superior mesenteric artery, pass through the mesenteric glands in their course to the thoracic duct. Along the side of the ascending and the transverse colon are a few other small lymphatic glands meso-colic^ which receive some absorbents of the large intestine. Dissection (fig. 144). By drawing the small intestine over to the right side, the dissector will observe the inferior mesenteric artery on the front of the aorta a little above the bifurcation. The peritoneum should be re- moved from it, and the branches should be traced outwards to the remain- ing half of the large intestine : a part of the artery enters the pelvis, but this will be dissected afterwards. On the artery and its branches the in- ferior mesenteric plexus of nerves ramifies. The mesenteric vein is to be followed upwards, away from the trunk of the artery, to its junction with the splenic, or with the superior mesenteric vein. On the aorta the dissector will meet with a plexus of nerves, which is to he left uninjured. The inferior mesenteric artery (fig. 144, b') supplies branches to the };art of the large intestine beyond the transverse colon ; and communi- 442 DISSECTION OF THE ABDOMEN. eating with the superior nnesenteric, assists to maintain the chain of anas- tomosis along the intestinal tube. This vessel is of smaller size than the superior mesenteric, and arises from the aorta, from one to two inches above the bifurcation. At first the vessel descends on the aorta, and crosses the left common iliac artery, as it courses to the pelvis to end in branches for the rectum (superior liEemorrhoidal). The following branches are furnished by it to the de- scending colon and the sigmoid flexure. Fig. 144. The Lower Mesenteric Artery, and the Aorta, seen by turning aside tlie upper rneseute ic artei-y and the small intestine. (Tiedemann). a. Aorta. /. Upper mesenteric. h. Inferior mesenteric artery. g. Renal. c. Left colic. h. Spermatic of the left side. d. Sigmoid, and c, Superior hajmorrhoidal branches. a. The left colic artery (c) ascends in front of the left kidney, and divides into an ascending and a descending branch for the supply of the descending colon : by the ascending offset it anastomoses with the middle colic branch of the superior mesenteric. b. The sigmoid artery {d) is distributed to the sigmoid flexure, and divides into offsets which anastomose above with the preceding colic, and below with the haimorrhoidal branch. Here, as in the rest of the intestinal tube, arches are formed by the arteries before they reach the intestine. VISCERAL PLEXUSES OF SYMPATHETIC. 443 c. The superior hcemorrhoidal artery (e) enters between the layers of the meso-recturn, and is distributed to the lower part of the great intes- tine : it will be described in the dissection of the pelvis. The inferior mesenteric vein (fig. 146, d) begins in the part of the great intestine to which its companion artery is distributed, and ascends along the psoas muscle to open into the splenic vein beneath the pancreas. Oc- casionally it joins the superior mesenteric vein. Both mesenteric veins are without valves, and may be injected from the trunk to the branches, like an artery. Lymphatic glands are ranged along the descending colon and the sig- moid fiexure. The absorbents of the intestine, after parsing through those glands, enter the left lumbar lympliatic glands. Sympathetic Nerve. The following plexuses of the sympathetic on the vessels, viz., superior mesenteric, aortic, spermatic, and inferior mesenteric, are derived from the solar plexus beneath the stomach. Tlie remaining portion of the sympathetic nerve in the abdomen will be subse- quently referred to. Dissection. On the two mesenteric arteries the dissector will have made out, already, the plexuses of nerves distributed to the intestinal tube beyond the duodenum. He has now to trace on the aorta the connecting nerves between the mesenteric plexuses, by taking tlie peritoneum from the aorta between the mesenteric vessels. From the upper part of the aortic plexus an offset is to be followed along the spermatic artery ; this may be done, on the left side, where the vessel is partly laid bare. By removing the peritoneum from the front of the sacrum, and follow- ing downwards, over the iliac arteries, tlie nerves from the aortic plexus and the lumbar ganglia, tlie dissector will arrive at the hypogastric plexus of the pelvis, opposite the top of the sacrum. The superior mesenteric plexus is a large offset, and is distributed to the same extent of the intestinal tube as the mesenteric artery. The nerves surround closely the artery wdth a sheath, but near the intestine some of them leave the vessels, and divide and communicate before enter- ing the gut. Branches. The secondary plexuses are the same as the off- sets of the artery, viz., intestinal nerves to the small intestine ; and an ileo-colic, a right colic, and a middle colic plexus to the large intestine. The aortic plexus is the network of nerves covering the aorta below the superior mesenteric artery ; it is stronger on the sides than the front of the aorta, in consequence of its receiving accessory branches from the lumbar ganglia, especially the left. At the upper part the plexus derives an offset, on each side of the aorta, from the solar and renal plexuses. It ends interiorly, on each side, in branches wdiich cross the common iliac artery, and enter the hypogastric plexus of the pelvis. From it offsets are furnished to the spermatic and inferior mesenteric arteries. The spermatic plexus., formed by roots from both the aortic and the renal plexus, runs on the spermatic artery to the testicle; in the cord it joins other filaments on the vas deferens. In the female, the nerves on the ovarian (spermatic) artery are furnished to the ovary and the uterus. The inferior mesenteric plexus supplies the part of the intestinal tube to which the artery is distributed. This plexus is furnished from the left part of the aortic plexus ; and the nerves composing it are whiter and larger than in either of the preceding plexuses of the sympathetic. Near 444 DISSECTION OF THE ABDOMEN. the intestine (sigmoid flexure) the branching of the nerves and the union of contiguous twigs are well marked. Branches. Its secondary plexuses are named from the arteries they accompany^ viz., left colic, sigmoid, and superior lieemorrhoidal : they ramify on the vessels, and have a like distribution. The hypogastric plexus., or the large prevertebral centre for the supply of sympathetic nerves to the viscera of the pelvis, is situate in front of the upper part of the sacrum. It is developed more on the sides than in the centre ; and the nerves, which are large and flat, have a plexiform arrangement, but without any intermixed ganglionic masses. By its upper part it receives the nerves on the aorta, and is joined by some filaments from one or two of the upper sacral ganglia. Interiorly the plexus ends in two parts, right and left, the last being the largest : each is continued forwards by the side of the internal iliac artery to the pelvic plexus of the same side, and to the viscera. CONNECTIONS OF AORTA AND VENA CAVA. Before the viscera are removed from the body, the connections of the abdominal aorta and vena cava may be learnt. Dissection. To see the aorta above the origin of the superior mesen- teric artery, it will be necessary to detach the great omentum from the stomach, without injuring the gastro-epiploic artery along the great curve ; and after raising the stomach and the spleen, to remove the peritoneum from the surface of the pancreas. A short arterial trunk (cmliac axis) above the pancreas is not to be cleaned now, otherwise the nerves about it would be destroyed. The vena cava on the right side of the aorta may be followed as far as the posterior border of the liver, where it disappears. The connections of its upper part can be better observed after the dissection of the ves- sels of the liver. The aorta enters the abdomen between the pillars of the diaphragm, and divides into iliac arteries opposite the left side of the fourth lumbar vertebra. At the beginning the vessel occupies the middle line of the spine, but it gradually inclines to the left as it descends. In the abdomen the aorta lies behind all the viscera ; but it is crossed more immediately by the pancreas and duodenum, which it touches with- out the intervention of peritoneum. Its connections are the following : at first it is covered by the solar plexus, and by the pancreas and the splenic vein ; still lower (beyond the superior mesenteric artery) by the left renal vein and the duodenum ; and thence to its termination by the peritoneum and the aortic plexus. The vessel lies'on the lumbar vertebrce, with the pillars of the diaphragm embracing it at the beginning. To its right side is the vena cava. Its relation to other deep parts is mentioned in p. 489. The vena cava inferior commences on the right side of the fifth lumbar vertebra by the union of the common iliac veins, and reaches thence to the heart. The venous trunk is placed on the right side of the vertebral column. It lies close to the aorta, and is concealed by the same viscera as high as the crus of the diaphragm ; but above that spot it is inclined away from the artery, and ascending on the right of the crus of the diaphragm, is imbedded in the posterior part of the liver for an inch or more. Lastly, DUODENUM AND PANCREAS. 445 it leaves the abdomen by an aperture in the tendinous centre of the dia- phragm, on the right of, and higher than the aortic opening. Its connections with vessels are not the same as those of the aorta. Beneath it are the right lumbar, renal, capsular, and diaphragmatic arteries; and crossing over it below the kidney is the spermatic. Super- ficial to it beneath the pancreas is the beginning of the vena portie. Off- sets of the solar plexus of nerves descend on it, as on the aorta. CONNECTIONS OF THE DUODENUM AND PANCREAS. Dissection. To see satisfactorily the duodenum and the pancreas the intestinal tube, beyond the duodenum, is to be removed in the following way : — a double ligature is to be placed on the upper part of the jejunum, another on the lower end of the sigmoid flexure of the colon, and the gut is to be cut through at the points at which it is tied. The detached piece of the intestinal tube is to be taken away by cutting through the vessels, and the peritoneum connecting it to the wall of the abdomen. After it has been separated, it is to be set aside for future study whilst the body is turned. The student should moderately inflate the stomach and duodenum from the cut extremity of the latter, and remove the loose peritoneum and the fat ; whilst cleaning them, he should lay bare the larger vessels and nerves. On turning upwards the stomach the pancreas may be traced from the spleen on the one hand to the duodenum on the other (fig. 145). By pulling forwards the duodenum, the common bile duct may be found, posteriorly, between the intestine and the head of the pancreas ; and some of the pancreas should be removed, to show its duct entering the duodenum. Duodenum (fig. 145, d). The first part of the small intestine, or the duodenum, begins at the pyloric end of the stomach, and crossing the spinal column, ends on the left side of the second lumbar vertebra. It makes a curve around the head of the pancreas, and occupies the right hypochondriac, right lumbar, and umbilical regions of the abdomen. From its winding course around tlie pancreas it is divided into three parts — superior transverse, vertical, and inferior transverse. The superior transverse part is free and movable, like the stomach ; it measures about two inches in length, and is directed from the pylorus to the neck of the gall bladder, ascending slightly between one point and the other. In front it is overlapped by the liver, as well as by the gall blad- der when tliis is distended ; and behind it are the bile duct and the vena portae. The vertical part is fixed almost immovably by the peritoneum and the pancreas. It is nearly three inches in length, and descends from the gall bladder as far as the third lumbar vertebra. Superficial to this [)art is the right bend of the colon ; and beneath it are the kidney and its vessels. On its inner side is the head of the pancreas, with the common bile-duct. The ducts of the liver and pancreas pour their contents into this portion of the duodenum. The inferior transverse part is the longest of the three, and is continued across the spinal column to end in the jejunal jjortion of the small intes- tine. As it crosses the spine, it ascends from tlie thii'd to the level of the 446 DISSECTION OF THE ABDOMEN. second lumbar vertebra, and lies between the layers of the transverse meso-colon. It has the following connections with the parts around : — In front of it are the superior mesenteric vessels with their plexus of nerves. Beneath it lie the vena cava and tlie aorta, with the pillars of the diaphragm ; and the left renal vein is sometimes between it and the aorta. Above it is the pancreas. Pancreas (fig. 145, ’^). The pancreas is situate behind the stomach, and lias numerous and complicated connections. Of an elongated form, it extends across the spine from the spleen to the duodenum, and occupies the left hypochondriac, the umbilical, and the right lumbar region of the abdomen. The gland is covered anteriorly by the ascending layer of the transverse meso-colon. It is in contact posteriorly with the aorta, the vena cava, and the pillars of the diaphragm ; and it conceals likewise the splenic vein and the commencement of the vena portae. Projecting above the upper border, near the centre, is the arterial trunk of the coelic axis : to the left of that vessel, along the same border, is placed the splenic artery ; whilst to the right of it lie the hepatic artery and the first part of the duodenum. At the lower border the superior mesenteric vessels emerge opposite the ccelic axis ; to the right of that spot lies the third part of the duodenum, and to the left the inferior mesen- teric ascending to join the splenic vein. The left end or the tail of the pancreas touches the spleen, and is placed over the left kidney. The right extremity or the head is received into the concavity of the duodenum, the two being partly separated by the common bile duct and the pancreatico-duodenal arteries. This part pro- jects above and below the body of the gland, like the head of a hammer beyond the handle ; and the lower projecting piece is directed to the left along the duodenum beneath the superior mesenteric vessels. COiLIC AXIS AND VENA PORTA:. A short branch of the aorta — the cceliac axis, furnishes arteries to the stomach and duodenum, the liver, pancreas, and spleen ; it subdivides into three chief branches — coronary, hepatic, and splenic. The veins corresponding with the arteries (except the hepatic) are col- lected into one trunk — the vena portae. Dissection. The vessels have been in part laid bare by the previous dissection, and in tracing them out fully the student should spare the plexuses of nerves around each. Supposing the liver well raised, he may first follow to the left side the small coronary artery, and show its branches to the oesophagus and the stomach. Next the hepatic artery, with the vena porta3 and the bile duct, may be traced to the liver and the gall bladder; and a considerable branch of it should be pursued beneath the pylorus to the stomach, duodenum, and pancreas. Lastly, the splenic artery, which lies along the upper border of the pancreas, is to he cleaned ; and its branches to the pancreas, stomach, and spleen should be defined ; this is a difficult task without the aid of some one to hold aside the stomach and spleen. The veins will have been dissected for the most part with the arteries ; but the origin of the vena portie is to be made out beneath the pancreas, and in front of the vena cava. The ccELiAC AXIS (fig. 145, c) is the first visceral branch of the ah- CCELIAC ARTERY AND BRANCHES. 447 (lominal aorta, and arises between the pillars of the diaphragm. It is a short thick trunk, about half an inch long, which projects above the upper border of the pancreas, and is surrounded by the solar plexus of the sym- pathetic. Its branches — coronary, hepatic, and splenic — radiate from the trunk (whence the name axis) to their distribution to the viscera in the upper part of the abdomen. a. The coronary artery {d) is the smallest of the three, and passes be- tween the layers of the little omentum to the left end of the stomach. At that spot it furnishes some oesophageal branches, and turns from left to right, along the upper border of the stomach, to anastomose with a branch (pyloric) (o) from the hepatic artery. Its offsets to the oesophagus and the stomach are thus distributed : — (Esophageal branches ascend on the gullet through the opening in the diaphragm, supplying that tube; and they anastomose on it with branches of the thoracic aorta. Gastric branches are given to both sides of the stomach, and those on the left end communicate with twigs (vasa brevia) of the splenic artery. b. The splenic artery (e) is the largest branch of the coeliac axis in the adult. It is a tortuous vessel, and runs almost horizontally to the spleen, along the upper border of the pancreas. Near the spleen it divides into terminal branches, about seven in number (from four to ten), which enter that viscus by the surface towards the stomach. It is accompanied by the splenic vein, which is below it; and it distributes branches to the pan- creas and the stomach. Pancreatic branches. Numerous small branches are supplied to the gland; and one of these, art. pancreatica magna., arises near the left end, and runs to the right in the substance of the viscus with the duct. Branches for the stomach arise from the divisions of the artery near the spleen. Some of these, vasa brevia, turn upwards to the left end of the stomach, beneath the gastro-splenic omentum, and ramify in the coats of that organ. Another longer branch, art. gastro-epiplo'ica sinistra (f) turns to the right between the layers of the great omentum along the great curvature of the stomach, and inosculates with the right gastro-epiploic branch of the hepatic artery. This artery distributes twigs to both surfaces of the stomach, and between the pieces of peritoneum forming the great omentum. c. The hepatic artery {g') is intermediate in size between the other two, and is encircled by the largest plexus of nerves. In its course to the liver the vessel is bent first to the right towards the small end of the stomach, where it supplies its principal branches (superior pyloric and gastro-epiploic). It ascends then between the layers of the little omen- tum, on the left side of the bile duct and vena portre, and divides near the transverse fissure of the liver into two — the right and left hepatic. Branches are distributed not only to the liver, but freely to the stomach, the duodenum, and the pancreas, as below: — The superior pyloric branch (o) descends to the upper border of the stomach, and running from right to left anastomoses with the coronary artery; it distributes small arterial tw'igs on both surfaces of the stomach. The right gastro-epiploic branch (7/)^ (art. gast. epiploica dextra) de- • This artery is named commonly gastro-duodenal as far as to the spot where it gives off the branch to the duodenum and pancreas. 448 DISSECTION OF THE ABDOMEN. scencls beneath the duodenum near the pylorus, and turning to the left along the great curvature of the stomach, inosculates with the left gastro-epiploic of the splenic artery. To the surfaces of the stomach some offsets are given; and others descend between the layers of the omentum. It furnishes the following named branches to the stomach, and the pan- creas and duodenum : — Small inferior pyloric branches end in the small extremity of the stomach. A. Liver. B. Gall-bladder, c. Stomach. D. Duodenum, E. Pancreas. F. Spleen. Vessels : a. Aorta. b. Upper mesenteric. c. Coeliac axis. d. Coronary. e. Splenic. /. Left gastro-epiploic, g. Hepatic. h. Right gastro-epiploic. i. Superior, and ft', inferior pan- creatico-duodenal. Z. Diaphragmatic arteries. n. Cystic. 0. Superior pyloric. The pancreatico-duodenal branch (?) (superior) arises opposite the duo- denum, and runs between the intestine and the pancreas ; it anastomoses below with the pancreatico-duodendal branch (inferior) of the superior mesenteric (fig. 146, b). Both the duodenum and the pancreas receive offsets from this vessel. On the posterior aspect of the same viscera is another small offset of the pancreatico-duodenal with a similar position and distribution. The hepatic branches (right and left) sink into the liver at the trans- verse fissure, and ramify in its substance : — The right branch is divided when about to enter the transverse fissure, and supplies the following small artery to the gall bladder. The cystic artery (??) bifurcates on reaching the neck of the gall bladder, and its two twigs ramify on the opposite surfaces. The left branch is smaller than the other, and enters the liver at the left end of the transverse fissure : a branch to the Spigelian lobe of the liver arises from this piece of the artery. Portal Veins. The veins of the intestinal tube, and of the spleen and pancreas, pour their blood into the vena portae. The two mesenteric veins and their branches have been referred to (p. 441); and the two following, with the trunk of the portal vein, remain to be noticed. The superior coronary vein (fig. 146,y) lies alonjr the upper border of the stomach. It begins in the oesophagus and the left part of the stomach, and joins the vena portae at the pylorus. The splenic vein (fig. 146) is large in size, and is formed by the union of branches from the spleen. It takes much the same course as, but below VENA PORT^ AND BRANCHES. 449 the artery, and runs beneath the pancreas to the front of the vena cava, where it joins the superior mesenteric vein (b) to form the vena portae. Between its origin and termination it receives branches corresponding with the following arteries : — vasa brevia (g')^ left gastro-epiplo'ic (e), and pancreatic. The inferior mesenteric vein (c?) opens into it about its middle. The vena portce (fig. 146, a) is formed by the union of the splenic and superior mesenteric veins. Its origin is placed in front of the vena cava, but beneath the pancreas, and two inches from the right end. The vessel is about four inches long, and is directed upwards in the small omentum, behind the bile duct and the hepatic artery, to the transverse fissure of the liver, where it divides into a right and a left branch. Fig. 146. a. Trunk of the vena portae. h. Upper mesenteric. c. Right gastro-epiploic. d. Inferior mesenteric. e. Left gastro-epiploic. /. Coronary of the stomach. g. Vasa brevia. Vejs'A Port^-e and the Veins Joining it (Henle: Anatomie des Menschen). In its course it is joined by the coronary vein (/), and by the cystic vein near the liver. The right branch enters the transverse fissure to ramify in the right lobe of the liver. The left branch is distributed to the left part of the liver, and gives a small branch to the Spigelian lobe. 29 450 DISSECTION OF THE ABDOMEN. This vein commences by roots in the viscera above mentioned, like any other vein, but it is deficient in valves ; and it ramifies through the struc- ture of the liver in the same manner as an artery. Its radicles communi- cate with the systemic veins on some parts of the intestinal tube, but more particularly on the rectum. Bile Ducts. Two hepatic ducts issue at the transverse fissure of the liver (fig. 158), one from each lobe,- and unite to form the following : — The common hepatic duct is an inch and a half long, and receives at its termination the duct of the gall bladder, the union of the two giving origin to the common bile duct. The common hile duct (ductus communis choledochus) is about three inches long. It descends almost vertically beneath the upper transverse portion of the duodenum ; then passing between the pancreas and the vertical piece of the duodenum, it opens into this portion of the intestine at the inner side, and above the middle. Whilst in the small omentum the duct lies to the right of the hepatic artery, and somewhat before the portal vein. Before piercing the coats of the intestine it is joined commonly by the pancreatic duct, but the two may enter the duodenum separately. SYMPATHETIC AND VAGUS NERVES. Sympathetic Nerve. In the abdomen, as in the thorax, the sympa- thetic nerve consists of a gangliated cord on each side of the vertebral column, and of pre vertebral centres or plexuses, which furpish branches to the viscera. Two prevertebral plexuses exist in the abdomen. One of these, the epigastric, is placed behind the stomach, and supplies nerves to all the viscera above the cavity of the pelvis. The other, the hypogastric plexus, is situate in the pelvis, and distributes nerves to the pelvic viscera. The knotted or ganq-liated cord will be met with in a subsequent stage of the dissection ; and only the great solar plexus with its offsets is to be now examined. Dissection. To denude the epigastric plexus, the following dissection is to be made : After the air has been let out of the stomach and duode- num, the portal vein, the common bile duct, and the gastro-epiploic ves- sels are to be cut through near the pylorus; and the stomach, duodenum, and pancreas are to be drawn over to the left side. On raising the liver the vena cava appears : the vein is to be cut across above the junction of the renal vein wdth it, and the lower end is to be drawn down with hooks. Beneath the vein the dissector will find the large reddish semi-lunar ganglion ; and mixed up with the nerves of the plexus are numerous lymphatic glands, and a dense tissue, which require to be removed with care. From its inner part he can trace the numerous nerves and ganglia around the coeliac and superior mesenteric arteries, and the secondary })lexuses on the branches of those arteries. From the outer part of the ganglion offsets are to be followed to the kidney, the suprarenal body, and the diaphragmatic arteries : at its upper part the junction with the large splanchnic nerve may be seen ; and deeper than the last, one or two smaller splanchnic nerves may be observed in a fissure of the diaphragm, which throw themselves into the coeliac and renal plexuses. The student should then trace the ending of the pneumogastric nerves on the stomach. The left nerve will be found at the upper border in front EPIGASTRIC OR SOLAR PLEXUS. 45.1 near the oesophagus ; and the right nerve will be seen at a corresponding point on the opposite aspect. Branches from the right nerve are to be followed to the plexus of the sympathetic by the side of the coeliac axis, and from the left, to the hepatic plexus. The EPIGASTRIC or solar plexus is a large network of nerves and ganglia, which lies in front of the aorta and the pillars of the diaphragm : it fills the space between the suprarenal capsules of opposite sides, and extends downwards to the pancreas, surrounding the cccliac axis and the superior mesenteric artery. The plexus is connected on each side with the large and small splanchnic nerves ; and it is joined also by an offset of the right pneumo-gastric nerve. Large branches are furnished to the different viscera along the vessels. The semilunar ganglia^ one on each side, are the largest in the body, and each is joined at the upper end by the great splanchnic nerve. Each is situate at the outer part of the plexus, close to the suprarenal body, and on the pillar of the diaphragm : the ganglion on the right side is beneath the vena cava. Irregular in shape, the mass is oval, or divided into smaller ganglia : from its outer side nerves are directed to the kidney and the suprarenal capsule. Offsets of the plexus. The nerves supplied to the viscera form plexuses around the vessels ; thus there are coeliac, mesenteric, renal, spermatic, diaphragmatic, &c. Diaphragmatic plexus. This plexus comes from the upper part of the semilunar ganglion, but it soon leaves the artery to enter the substance of the diaphragm : a communication takes place between the phrenic nerve of the cervical plexus (p. 80) and these branches of the sympathetic. On the right side is a small ganglion where the plexus is joined by the spinal nerve; and from it filaments are supplied to the vena cava and the supra- renal body. The ganglion is absent on the left side. (Swan.) The suprarenal nerves are very large and numerous, in comparison with the size of the part supplied, and are directed outwards to the suprarenal body. One of the splanchnic nerves communicates with this plexus. The renal plexus is derived from the semilunar ganglion and outer part of the plexus, and is joined by the smallest splanchnic nerve. The nerves surround the renal artery, liaving small ganglia on them, and enter the kidney with the vessels. An offset is given from the renal to the sper- matic plexus (p. 443). The coeliac plexus is a direct continuation of the plexus around its artery : it is joined by the small splanchnic nerve on each side, and by an offset from the right pneumo-gastric nerve. The plexus divides like the artery into three parts — coronary, splenic, and hepatic. a. The coronary plexus accompanies the vessel of the same name to the upper border of the stomach, where it ends : it communicates with the left vagus nerve. h. The splenic plexus furnishes offsets to the pancreas, and to the stomach along the left gastro-epiplo’ic artery : and it is joined by an offset from the right pneumo-gastric nerve. c. The hepatic plexus is continued on the vena porta3, the hepatic artery, and the bile duct into the liver, and ramifies on those vessels : in the small omentum, the plexus is joined by offsets from the left vagus. The follow- ing secondary plexuses are furnished around the branches of the hepatic artery, and have the same name and distribution as the vessels : — A pyloric plexus is distributed along the upper border of the stomach. 452 DISSECTION OF THE ABDOMEN. Two other plexuses — g astro -epiploic (right) pancreatico-diiodenal^ correspond in distribution with the branches of each artery. A cystic plexus ramifies in the coats of the gall bladder with its artery. The remaining ofisets of the plexus, viz., superior and inferior mesen- teric, aortic, and spermatic, have been already noticed (p. 443) ; but the derivation of the superior mesenteric and aortic plexuses from the epigas- tric centre can be now seen. Ending of the splanchnic nerves. The large nerve perforates the crus of the diapliragm, and generally ends altogether in tlie semilunar gan- glion. The small nerve comes through the same opening in the diaphragm as the preceding, and joins the coeliac plexus. The smallest nerve., which is often absent, throws itself into the renal plexus. Ending of the vagus nerve. The pneumo-gastric nerves end in the stomach : — The left nerve divides into branches, which extend along the small cur- vature, and over the front of the stomach ; these send offsets to the hepatic plexus. , Tlie right nerve is distributed to the posterior surface of the stomach near the upper border ; it communicates with its fellow, and with the coeliac and splenic plexuses. Dissection. The viscera are now to be removed from the abdomen, in order that the body may be turned for the dissection of the Back and lower limbs. The stomach and the spleen, with the duodenum and the pancreas, are to be taken away together by cutting through the oeosphagus near the dia- phragm, as well as the vessels and nerves they receive. The liver is to be removed from the abdomen by dividing its ligaments, and incising the vena cava between the posterior border and tlie diaphragm. At the same time the left testicle, and the right kidney with the supra- renal body, should be removed for examination whilst the body is turned ; the former can be taken out by cutting through the spermatic cord, and the latter by dividing the vessels about the middle. Directions. Supposing the body to be now turned for the dissection of the Back, and to lie with the face downwards for the usual time, the dissector may look first to the fascia lumborum, which is described in the Dissection of the Back, p. 357. The rest of the time should be occupied in learning the viscera included in the following Section. Section IV. ANATOMY OF THE VISCERA OF THE ABDOMEN. THE STOMACH. The stomach is the dilated part of the alimentary tube between the oesophagus and the small intestine, into which the masticated food is re- ceived to be changed into chyme. Dissection. To see the form, the stomach must be blown up moder- STRUCTURE OF STOMACH. 453 ately, and the surface cleaned ; but, previously, let the student detach the spleen, and cut through the duodenum close to the pylorus. Forms and Divisions. The stomach is somewhat conical in form (fig. 147). Its size varies much in different bodies, and is sometimes much diminished by a constriction in the centre ; when it is moderately dis- tended, it is about twelve inches long and four wide. There are two ends, two orifices, two surfaces, and two borders or curves to be examined. Extremities. The left end or tuberosity (fundus ventriculi) is the largest part of the stomach, and projects about three inches to the left of the opening of the msophagus. The right or pyloric end, much smaller than the other, is cylindrical, and forms the apex of the cone to which the stomach is likened. Openings. The left opening (cardiac), which communicates with the oesophagus, is at the highest part of the stomach, and is funnel-shaped towards the cavity of the organ. The right of pyloric orifice opens into the duodenum, and is guarded internally by a muscular band (pylorus) : at the same spot the stomach is slightly constricted externally, where a firm circular ring may be felt. " Surfaces. The surfaces (anterior and posterior) are somewhat flattened when the viscus is empty, but rounded when it is distended : the parts in contact with them have been referred to (p. 431). Borders. The upper border or small curve is concave towards the left opening, but convex at the opposite end ; and the lower border or large curve is convex, except near the right end, where it is concave — the con- cavity of the one border corresponding with the convexity of the other. An arterial arch, and a fold of peritoneum (omentum) are fixed to each border. Structure. In the wall of tlie stomach are four coats, viz., serous, muscular, fibrous, and mucous ; and belonging to these there are vessels, nerves, and lymphatics. Serous coat. The peritoneum gives a covering to the stomach, and is adherent to the surface, except at each margin, where an interval exists corresponding with the attachment of the small and large omentum : in those spaces are contained the vessels, nerves, and lymphatics. During distension of the stomach the spaces above mentioned are much di- minished. The muscular coat will be laid bare by the removal of the serous cover- ing. It consists of three sets of fibres — longitudinal, circular, and oblique ; these lie from without inwards in the order mentioned, and are unstriated or involuntary. The longitudinal fibres (fig. 147, a) are derived from the oesophagus; they spread over the surfaces, and are continued to tlie pylorus and the small intestine. The fibres are most marked along the borders, particu- larly at the smaller one ; and at the pylorus they are stronger than in the centre of the stomach. The circular fibres (fig. 147, b) form the middle stratum, and will be best seen by removing the longitudinal fibres near the pylorus. They reach from the left to the right end of the stomach ; but at the pylorus they are most numerous and strongest, and form a ring or sphincter (e) around the opening. The oblique fibres (fig. 147, e) are continuous with the circular or deep layer of the cesophagus. On the left and right of the cardie orifice they are so arranged as to form a kind of sphincter {d and e) (Henle); but 454 DISSECTION OF THE ABDOMEN. those on the left (e), the strongest, arch over the great end of tlie stomach, and spread out on tlie anterior and posterior surfaces, gradually disappear- ing on them. Fibrous coat. By removing the muscular layer over a small space, the fibrous coat will appear as a white shining stratum of areolar tissue. This coat gives strength to the stomach, and serves as a bed in which the larger vessels and nerves ramify before their distribution to the mucous, layer. If a small opening is made in this membrane, the mucous coat will project through the stomach to be distended with air. Fig. 147. Diagram Eepkesenting the Arrangement of the Muscular Fibres of the Stomach. Part of each of the two external coats is removed. а. External or longitudinal fibres. e. Oblique fibres, more numerous, on the right of б. Middle or circular. the cardiac orifice, and covering the great c. Sphincter of the pylorus. end of the stomach. d. Oblique fibres on the left of the cardiac opening. The mucous coat will come into view on cutting open the stomach, but the appearances now described can be recognized only in a recent stomach. This coat is a thickish layer, of a pale rose color soon after death in the healthy condition. In the empty state of the stomach the membrane is less vascular than during digestion ; and in infancy the natural redness is greater than in childhood or old age. When the stomach is contracted the membrane is thrown into numerous wavy ridges or rugce, which become longitudinal along the great curve, towards the pylorus. Tlie thickness of the mucous membrane is greatest near the pylorus ; and at that spot it forms a fold, opposite the muscular ring, which assists in closing the opening. If this membrane and its submucous layer are removed from the pyloric part of the stomacli, the ring of muscular fibres (sphincter of the pylorus) will be more perfectly seen. Microscopic structure of the mucous membrane. With the aid of a lens, the surface of the mucous membrane, when well washed, may be seen to be covered by shallow depressions or alveoli (fig. 148), which measure from ^^oth to across. Generally hexagonal or polyjG-o- nal in outline, the hollows become larger and more elongated towards the small end of the stomach ; and near the pylorus the margins of the alveoli ])roject, and become irregular. In the bottom of each depression are the apertures of minute tubes. STRUCTURE OF STOxMACH. 455 By means of a thin section under the microscope the membrane may be observed to be composed almost altogether of minute vertical tubes, which lie side by side, and project into the submucous tissue. Measuring from ^^gtli to ^^gth of an inch in length, the tubes are closed at the deep end ; but they open on the surface of the stomach both in the alveoli (tig. 148) and in the interalveolar spaces. They are formed of a homogeneous membrane, and are for the most part straight, but towards the pylorus they increase in length, and are somewhat sacculated at the deep extrem- ity; some are divided into two or more pieces (fig. 149). Fig. 148. Fig. 149. Alveolar Depressions op the Mucous Membrane op the Sto- mach, magnified 32 diameters, with the minute tubes opening into them (Sprott Boyd.) (7 Enlarged Representation op the Tubes of the Stomach. a. Gastric tube from the pyloric end lined, throughout, by columnar epithelium (Kolliker). h. Gastric tube from the cardiac end, with a columnar epithelium lining near the mouth, and fiattened nu- cleated granular cells beyond (Thomson). At the cardiac end of the stomach the tubes are lined at the free end by columnar epithelium (fig. 149, 6); but in the closed end by flattened and granular nucleated cells, which are named peptic glands^ and are sup- posed to giv^e origin to the gastric fluid. Towards the pylorus the tubes are closed throughout by columnar epithelium (fig. 149, a) and secrete mucus. A columnar epithelium covers the surface of the mucous membrane, and enters the small tubules. On the attached surface of the mucous membrane is a thin layer of in- voluntary muscular fibres, separating it from the fibrous coat : it is said to send offsets amongst the tubules. Blood^'essels. The arteries of the stomach, after supplying the mus- cular coat, ramify in the submucous tissue ; from this anastomosis fine offsets are continued on the tubes to the inner surface of the mucous mem- brane, where they form a network. The veins begin in the mucous mem- brane, receive branches from the muscular coat, and deliver their blood into the portal system. Lymphatics, Two layers of absorbents, superficial and deep, exist in the stomach : tjie latter begin in a plexus beneath the tubules, and form a 456 DISSECTION OF THE ABDOMEN. network in the fibrous layer. Both sets leave the stomach with the bloodvessels. Nerves. The nerves are derived from the pneumo-gastric and sympa- thetic (p. 451), and can be followed to the fibrous coat; small ganglia have been observed on them. SMALL INTESTINE. The three parts into which the small intestine is divided, have the fol- lowing characters : — The duodenum measures as much as the breadth of twelve fingers, viz., about ten inches, and is more fixed than the rest of the intestinal tube. It is wider than either the jejunum or the ileum, and its muscular coat is also thicker. Into it the common bile and pancreatic ducts pour their contents. The jejunum and the ileum together measure about twenty feet in length, and are connected with the mesentery. There is not any percep- tible difference between the termination of the one and the commencement of the other, but two-fifths of the length are assigned to the jejunum, and three-fifths to the ileum. Between the ends, however, a marked dif- ference may be perceived ; for the upper part of the jejunum is thicker and more vascular than the lower part of the ileum, and its width is also greater. Structure. In the small intestine the wall is formed by the same number of layers as in the stomach, viz., serous, muscular, fibrous, mucous, and submucous. Dissection. The different layers are to be examined on pieces, about three inches long, taken from the duodenum, the upper part of the jejunum, and the lower end of the ileum. After the pieces have been cut off, they are to be distended with air ; and the serous covering is to be torn off for a sliort distance, to show the muscular coat, but in doing this, the external longitudinal fibres will be taken away without great care. The serous coat is closely connected with the subjacent muscular layer. To the jejunum and ileum it furnishes a covering, except at the attached part where the vessels enter : at this spot tlie peritoneum is reflected off to form the mesentery, and a space exists resembling that at the borders of the stomach. The peritoneum surrounds the duodenum only partly; this peculiarity has been described at p. 438. The muscular coat is constructed of two sets of fibres, a superficial or longitudinal, and a deep or circular. The fibres are pale in color, and are not striated. The longitudinal fibres form a thin covering, which is most marked at the free border of the gut. The circular fibres are much more distinct than the others, and give the chief strength to the muscular coat : they do not form complete rings around the intestine. Dissection. On the removal of a part of the muscular stratum from the jejunum or the ileum, the submucous fibrous layer will come into view. Tlie fibrous coat has the same position and use as the corresponding layer in the stomach. Dissection. In the upper part of the duodenum the student is to seek some small compound glands — tliose of Brunner, which are imbedded in the submucous tissue. They lie beneath the mucous membrane, and will COATS OF SMALL INTESTINE. 457 be seen shining through the fibrous layer, when the muscular coat has been taken away. The pieces of intestine may be opened and washed to show the mucous coat, but the gut should be cut along the line of attachment of the mesen- tery, so as to avoid Peyer’s glands on the opposite side. Mucous coat. The lining membrane is thicker and more vascular at the beginning than at the ending of the small intestine. It is marked by numerous prominent folds (valvulae conniventes) ; and the surface of the membrane is covered with small processes (villi) like the pile of velvet. Occupying the substance of the mucous coat are numerous glands ; and covering the whole is a columnar epithelium. A thin layer of non-striated muscular fibres {muscularis mucosce) covers the outer surface of this coat (fig. lo4, d), and sends inwards prolonga- tions between the tubules into the villi. The valvulce conniventes (fig. 150) (valves of Kerkring) are permanent ridges of the mucous membrane, which are arranged circularly in the intestine, and project into the alimentary mass. Crescentic in form, they extend round the intestine for half or two-thirds of its circle, and Fig. 150. The Duodenum opened showing the Valvul;e Conniventes, and the opening op the Bile Duct. The duct of the paucreas is also represeuted in greater part of its course. a. Duodenum. d. Pancreatic duct. h. Pancreas. e. Opening of the common duct in the intestine c*. Common bile duct. (Henle). some end in bifurcated extremities. Larger and smaller folds are met with, sometimes alternating ; and the larger are about two inches long, with one-third of an inch in depth towards the centre. Each is formed of a doubling of the mucous membrane, which incloses vessels between the layers. They begin in the duodenum, about one or two inches beyond the py- lorus, and are continued in regular succession to the middle of the jeju- num ; but beyond that point they become smaller and more distant from one another, and finally disappear about the middle of the ileum, having previously become irregular and rudimentary. The folds are largest and most uniform beyond, and not far from the opening of the bile duct. The aperture of the common bile pancreatic ducts (fig. 150, e) is a 458 DISSECTION OF THE ABDOMEN. narrow orifice, from three to four inches from the pylorus, and is situate in a small prominence of the mucous membrane, at the inner and posterior part of the duodenum (p. 445). A probe passed into the bile duct will show the oblique course (half an inch) under the mucous coat. Some- times the pancreatic duct opens by a distinct orifice. Microscopic structure of the mucous membrane. With the use of the microscope, and with pieces of fresh intestine, the student will be able to make out the nature of the villi, the glandular bodies, and the epitlielium. Villi. When a piece of the lower part of the duodenum, from which the mucus is washed away, is examined in water, the mucous membrane will be seen to be studded over thickly with small projections, like those on velvet. These bodies exist along the whole of the small intestine, and are irregular in form (fig. 153, some being triangular, others conical or cylindrical with a large end. Their length is from ^^th to -goth of an inch ; and they are best marked where the valvuhn conniventes are largest. In the duodenum their number is estimated at 50 to 90 in a square line, but in the lower end of the ileum at only 40 to 70 on the same surface (Krause). Each villus is an extension of the mucous coat, and is covered by col- umnar epithelium. One or sometimes two arterial twigs form a capillary network beneath the mucous covering (fig. 144, ^), and end generally in a single emerging vein. A single lacteal, or two forming a loop with cross branches (fig. 151, ®), occupies the centre, and communicates with A. Vessels of the Villi in the Mouse, In- jected BY Gerlach (Kollicker). a. Artery, and 6, vein. B. Lacteals and Plexus of Vessels in two Villi, Injected by Teichman. a. Lacteal vessel, single in one villus, double in the other. h. Plexus of vessels c. Plexus of lacteals below the villi. (Quain’s Anatomy.) })lexus below the villus. Around the lacteals a thin layer of unstriated muscular fibre is arranged longitudinally (Briicke). Nerves have not been detected in the villus. Glands. In the glandular apparatus of the small intestine are included PATCHES OF PEYER. 459 the crypts of Lieberkiihn, solitary glands, and Peyer’s and Brunner’s glands. The crypts of Lieherkiihn (fig. 154, a) are minute simple tubes, similar to those in the stomach, though not so closely aggregated, which exist throughout the small intestine. They open on the surface of the mucous membrane by small orifices between the villi, and around the larger glands ; but closed at the opposite end, they project into the submucous layer, and are seldom branched. Their length is from inch : they are filled with a translucent fluid containing granules, and are lined by a columnar epithelium. The so-called solitary glands (fig. 153, ®) are roundish white eminences, about the size of mustard seed if distended, which are scattered along the small intestine, but in greatest numbers in the ileum. Placed on all parts of the intestine, and even on or between the valvulje conniventes; they are covered by the villi of the mucous membrane, and are surrounded at Fig. 152. A B A. Patch of Peyer’s Glands four times en- larged. a. Surface of the mucous membraue covered with villi. h. Pits over the follicles where the villi are ab- sent. B. Magnified Representation of an Injec- tion IN the Rabbit, by Frey, of the Vessels Surrounding and Penetrating THE Follicles in a Patch of Peyer (Kol- licker). tbe’r circumference by apertures of the crypts of Lieberkiihn. They are closed lymph follicles beneath the mucous coat, which project into the gut; and they are formed of a network of reticular connective tissue with lymph-corpuscles between the meshes. Fine capillary vessels permeate the mass; and it is surrounded by a plexus of lymphatic vessels. The glands of Peyer (fig. 153, ■^) (glanduloe agminatae) exist chiefly in the ileum, in the form of oval patches, which measure from half an incli to two inches or more in length, and about half an inch in width. They are situate on the part of the intestine opposite to the attaehment of the mesentery, and their direction is longitudinal in the gut: usually they are from twenty to thirty in number. In the lower part of the ileum they are largest and most numerous; but they decrease in number and size up- 460 DISSECTION OF THE ABDOMEN. wards from that spot, till at the lower part of the jejunum they become irregular in form, and may consist only of small roundish masses. The mucous membrane over them is hollowed into pits (fig. 152, 5), and is generally destitute of villi on the subjacent follicles (fig. 153, ^), but between the pits it has the same characters as in other parts. Fig. 153. A B A. A PIECE OF Mpcors Membrane enlarged, with its villi and tubules. Part of a patch of Fever’s glands is also represented with the follicles (a), each having a ring of tubes at the cir- cumference. B. A “solitary gland” of the small intestine, also enlarged, covered by villi (Boehm). A patch, when examined by the microscope, appears to be but a collec- tion of lymph follicles like the “solitary glands” (fig. 153), which are round or oval in form, and are covered by the mucous membrane. Around each follicle is a ring of apertures of the crypts before described. The follicles have the same composition as the scattered “solitary glands.” Fine arterial twigs (fig. 152, ramify on the follicles, and send inwards capillary offsets which form a network in the inte- rior, and converge to the centre. Lacteal vessels form plexuses around and beneath the follicle, but do not penetrate the wall. The Glands of Brunner (fig. 154, 5) are small compound bodies, similar to the buc- cal and labial glands of the mouth, which exist in the duodenum. For a few inches near the pylorus they are most numerous, and there they are visible without a lens, being nearly as large as hemp seed. The glands consist of lobules, with appertaining excretory tubes: and each ends on the sur- face of the mucous membrane by a duct (c), whose aperture is slightly larger than the mouths of the contiguous crypts of Lieberkiihn ; they secrete mucus. Epithelium. The epithelial lining of the mucous membrane of the small intestine is of the columnar or cylindrical kind. On the villi it forms a distinct covering of elongated pieces. It sinks into the crypts Magnified View of the Mucous Membrane of the Duodenum, with the tubules of Lieberktlha and a gland of Brunner. a. Tubules. h. G land of Brunner. c. Duct of the gland. d. Submucous layer of muscular fibres (KOlliker). LARGE INTESTINE. 461 of Lieberkiihn, and into the ducts of the glands of Brunner, and gives them a lining. Dissection. To demonstrate the areolar tissue between the coats of the intestine, a piece of the bowel turned inside out is to be inflated forcibly ; and to insure the success of the attempt, a few cuts maybe previously made through the peritoneal coat. The air enters the wall of the intes- tine where the peritoneal covering is injured, and spreads through the whole gut ; but opposite the solitary glands, and the patches of Peyer, the mucous coat is more closely connected with the contiguous structures, and the subjacent portion will not be distended with the air. The piece of the intestine may be examined when it is dry. Vessels of the intestine. The branches of arteries ramify in the sub- mucous layer, and end in a network of small twigs in the mucous mem- brane, which supplies the folds, the villi, and the glands. Opposite Peyer’s patches the intestine is most vascular ; and the vessels form circles around the follicles, before supplying offsets to them. The vehis have their usual resemblance to the companion arteries. The absorbents consist of a superficial set (lymphatics) in the muscular coat ; and of a deep plexiform set (lacteals) in both the mucous and sub- mucous layers. The two sets join, and all end in larger trunks in the mesentery. Nerves of the small intestine come from the upper mesenteric plexus, and entering the coats by the side of the arteries, form plexuses with in- terspersed ganglia. One such plexus is contained in the muscular coat between the longitudinal and circular fibres (Auerbach) ; and another is placed in the submucous layer (Meissner) : they join freely by branches through the intestinal coats, and reach from the pylorus to the extremity of the alimentary tube. Structure of the common bile duct. The bile duct consists of an exter- nal or strong fibrous layer, and of an internal or mucous coat which is lined by columnar epithelium. On the surface of the inner membrane are the openings of numerous branched mucous glands, which are imbedded in the fibrous coat ; some of them are aggregated together, and are visible with a lens. LARGE INTESTINE. The large intestine is the part of the alimentary canal between the termination of the ileum and the anus. Its division and its attachment by peritoneum to the abdominal wall, have been described (p. 4d3). In length tliis part of the alimentary canal measures about five or six feet — one-fifth of the length of the intestinal tube. The diameter of the colon is largest at the commencement in the ccecum, and gradually de- creases as far as the rectum, where there is a dilatation near the end. When compared with the small intestine, the colon is distinguished by the following characters : It is of greater capacity, being in some parts as large again, and is more fixed in its position : it is also free from convolu- tion, except in the left iliac fossa, where it forms the sigmoid flexure. Instead of being a smooth cylindrical tube, the colon is sacculated, and is marked by three longitudinal muscular bands, which alternate with as many rows of dilatations ; but at the lower part of the large intestine (rectum), the surface is smooth, and the longitudinal bands have disap- peared. Attached to the surface at intervals, especially along the trans- 462 DISSECTION OF THE ABDOMEN. verse colon, are processes of peritoneum containing fat — the appendices epiploicae. Dissection. For the purpose of examining the large intestine the student should cut off and blow up the caecum, with part of the ileum entering it ; he should prepare in a similar way a piece of the transverse colon, and a piece of the sigmoid flexure (about four inches of each). The areolar tissue and the fat are to be removed with care from each, after it has been inflated. The C^CUM, or the head of the colon (fig. 15o, a) (caput caecum coli) is the rounded part of the large intestine which projects, in the form of a pouch, below the junction of the ileum with it. It measures about two inches and a half in length, and though gradually narrowing inferiorly, the caecum is the widest part of the colon — hence the name caput coli. At its inner side it is joined by the small intestine (J)) ; and still lower there is a small worm4ike projection (c) — the ver- miform appendix. Appendix vermiformis (fig. 155, c). This little convoluted projection is attached to the lower and hinder part of the caecum, of which it was a continuation, at one period, in the embryo. From three to six inches in length, the appendix is rather larger than a goose- quill, and is connected to the inner part of the caecum by a fold of peritoneum. It is hollow, and has an aperture of communica- tion with the intestine (c?). In structure it resembles the rest of the colon. Dissection. To examine the interior of the caecum, and the valve between it and the small intestine, the specimen should be dried, and the following cuts should be made into it : One oval piece is to be taken from the ileum near its termination ; another from the side of the caecum, opposite the entrance of the small intestine. lleo-ccecal valve (fig. 155). This valve is situate at the entrance of the ileum into the caecum. It is composed of two pieces, each with a different inclination, which project into the interior of the caecum, and bound a narrow, nearly transverse aperture of communication between the two differently-sized portions of the alimentary canal. The upper piece of the valve, ileo-colic (e) projects horizontally into the large intestine, opposite the junction of the ileum with the colon. And the lower piece, ileo-ccecal {/)■, which is the larger of the two, has a ver- tical direction between the ileum and the caecum. At each extremity of the opening the pieces of the valve are blended together; and the result- ing prominence (y) extends transversely on each side of the intestine, forming the frcena or retinacula of the valve. Fig. 155. Interior of a C-®cum dkieo and LAID OPEN. <1. Caecum, h. Small intestine c. Vermiform appendix, and its aperture. e. Ilio-colic piece of the valve at the j unction of the small in- testine. /. llio-csecal piece of the valve. g. Retinaculum of the valve on each side. STRUCTURE OF THE COLON. 463 The size of the opening depends upon the distension of tlie intestine ; for when the retinacula of the valve are stretched the margins of the aperture are approximated, and may be made to touch. Each piece of the valve is formed by circular muscular fibres of the in- t ‘stinal tube, covered by mucous membrane; as if the ileum was thrust obliquely through the wall of the csecum, after being deprived of its peri- toneal coat and layer of longitudinal fibres. This construction is easily seen on a fresh specimen by dividing the peritoneum and the longitudinal fibres, and gently drawing out the ileum from the ciecum. The opening of the appendix into the caecum (o?) is placed below that of the ileum. A piece of mucous membrane partly closes the aperture, and acts as a valve. Folds or ridges are directed transversely in the interior of the gut, and correspond with depressions on the outer surface : these Iblds result from the doubling of the wall of the intestine, and the largest inclose vessels. Structure of the Colon. The coats of the large are similar to those of the small intestine, viz., serous, muscular, fibrous, and mucous. Serous coat. The peritoneum does not clothe the large intestine, throughout, in the same degree. It covers the front of the ccecum, and the front and sides of the ascending and descending colon ; but in neither does it reach commonly tlie posterior aspect (p. 438). The transverse colon is incased like the stomach, and has intervals along the borders, where the transverse meso-colon and the great omentum are attached. The muscular coat is formed by longitudinal and circular fibres, as in the small intestine. The longitudinal fibres may be traced as a thin layer over the surface, but most are collected into three longitudinal bands, about a quarter of an inch in width. On the vermiform appendix the fibres form a uniform layer ; but they are continued thence into the bands on the csecum and colon : on the rectum they are diffused over tiie surface. When the bands are divided the intestine elongates — the sacculi, and the ridges in the interior of the gut, disappearing at the same time. The circular fibres are spread over the whole surface, but are most marked in the folds projecting into the intestine. In the rectum (to be afterwards seen) they form the band of the internal sphincter muscle. The fibrous coat resembles that of the small intestine. It will be ex- posed by removing the peritoneal and muscular coverings. The mucous coat., which may be examined on opening the intestine, is smooth, and of a pale yellow color ; and it is not thrown into special folds, except in the rectum. The surface is free from villi ; and by this circum- stance the mucous membrane of the large, can be distinguished from that of the small intestine. This difference in the two portions of the alimen- tary tube is well marked on the ilio-ccecal valve ; for the surface looking to the small intestine is studded with villi, whilst the lower surface, covered by the lining membrane of the ccecum, is free from those small eminences. Microscopic appearances. In a piece of fresh intestine the microscope will show the mucous membrane to possess small tubes or crypts, and some larger solitary follicles; with an epithelial covering on the free sur- face, and a thin muscular layer {rnuscidaris mucosce') on the other, whose arrangement is similar to that of the small intestine. The tubules (fig. loG, ®) occupy the whole length of the large gut, and resemble those of the small intestine, but are more numerous and closer together. Their orifices on the surface are circular (’), and are more uni- 464 DISSECTION OF THE ABDOMEN. formly diffused than the apertures of the tubules in the small gut. A vertical section of the membrane will show the tubes to ex- tend vertically from the surface into the sub- mucous coat, and to be longer than the crypts of Lieberkuhn in the jejunum and ileum ; they measure from gL th to th of an inch in length. The so-called solitary glands (fig. 156, are scattered here and there through the large intestine ; but they are in greatest number in the caecum and vermiform appendix. They are whitish rounded bodies from J^th to of an incli in diameter, and are situate in the submucous layer amongst the tubules. They are lymph follicles with a structure like that in the small intestine. The epithelium is of the columnar kind, and enters the tubules. Vessels. The distribution of the vessels in the wall of the large intes- tine is the same as in the smaller bowel. Nerves. In the coats of the large intestine the nerves have the plexi- form arrangement like that in the small gut. The absorbent vessels form two sets as in the small intestine; after leav- ing the gut they join the lymphatic glands along the side of the colon. THE PANCREAS. The pancreas (fig. 1 45, e) is a narrow flattened gland, from six to eight • inches in length, which has some resemblance to a dog’s tongue. It is larger at the right than the left end ; and it is divided into head, tail, and body. The head, or the right extremity, occupies the concavity of the duo- denum; and the left extremity, or the tail, is rounded, and touches the spleen. The body of the gland is narrowest a little to the right of the vertebral column, and is thickest at the upper border ; it measures about one inch and a half in breadth, and from half an inch to an inch in thickness. The connections of the pancreas with surrounding parts are described at p. 446. Dissection. Let the pancreas be placed on the anterior surface, and let the excretory duct be traced from the head to tlie tail by cutting away the substance of the gland. The small duct will be recognized by its whiteness. Structure. The pancreas is a gland consisting of separate lobules, and is provided with a special duct. It is destitute of a distinct capsule ; but it is surrounded by areolar tissue, which projects into the interior, and connects together its smaller pieces. The fluid secreted by it assists in the digestion of the aliment. The lobules are soft and loose, and of a grayish-white color, and are united into larger masses by areolar tissue, vessels, and ducts. Each con- sists ultimately, as in the parotid, of the branchings of the excretory duct, which end in closed vesicular extremities, and are surrounded by a plexus of vessels. In the vesicles the epithelium is spheroidal. Fig. 156. A B Enlarged View of “a Solitary Gland,” and of the tubules of the mucous coat. (Boehm.) A. Gland of the large intestine. B. Tubules of the mucous mem- brane. 1. Surface opening. 2. Side view of the tubes. 3. Pits for the closed ends of the tubes in the submucous tissue. THE SPLEEN. 465 The duct of the pancreas (fig. 150, d) (canal of Wirsung) extends the entire length of the gland, and is somewhat nearer the lower than the upper border. It begins in the tail of the pancreas, where it presents a bifurcated extremity; and as it continues onwards to the head, it receives many branches. It finally ends by opening into the duodenum, either in union with, or separate from the common bile duct (p. 457). Of the tribu- tary branches, the largest is derived from the head of the pancreas. The duct measures from y^gth to y\)th of an inch in diameter near the duodenum. It is formed ol' a fibrous and a rnucons coat : the latter is lined by a cylindrical epithelium^ and is provided with small glands in the duct and its largest branches. Vessels^ lymphatics, and nerves. The arteries and veins have been described (p. 447); and the lymphatics join the lumbar glands. The nerves are furnished by the solar plexus. THE SPLEEN. The spleen is a vascular spongy organ of a bluish or purple color, some- times approaching to gray. Its texture is friable, and easily broken under pressure. The use of the spleen is unknown. The viscus is somewhat elliptical in sliape, and is placed vertically against the great end of the stomach. Its size varies much. In the adult it measures commonly about five inches in length, three or four inches in breadtii, and one inch to one inch and a half in thickness. Its weight lies between four and ten ounces, and is rather less in the female than the male. At the outer aspect it is convex towards the ribs, the inner surface is marked by a longitudinal ridge, nearer the posterior than the anterior border, into which the vessels plunge to ramify in the interior. Before and behind the ridge, the surface is flattened or somewhat hollowed. The spot where tlie vessels enter is named the hilum of the spleen. The anterior border is thinner than the posterior, and is often notched. Of the tvv'o extremities, the lower is more pointed than the upper. Small masses or accessory spleens (splenculi), varying in size from a bean to a moderate-sized plum, are found occasionally, near the fissure of the spleen, in the gastro-splenic omentum, or in the great omentum. Structure. Enveloping the spleen are two coverings, a serous and a fibrous. It is formed by a network of fibrous or trabecular tissue, which contains in its meshes the splenic pulp, with the Malpighian corpuscles. Throughout the mass the bloodvessels and the nerves ramify. No duct exists in connection with this organ. The serous or peritoneal coat incases the spleen, and covers the surface except at the hilum and the posterior border. It is closely connected to the subjacent fibrous coat. The Jibrous coat (tunica propria) gives strength to the spleen, and forms a complete case for it. At the fissure on the inner surface this investment passes into the interior with the vessels, to which it furnishes sheaths : and if an attem[)t is made to detach this coat, numerous fibrous processes will be seen to be connected with its inner surface. Its color is whitish ; and its structure is made up of areolar and elastic tissues. Dissection. The spongy or trabecular structure will best appear, by washing and squeezing a piece of fresh bullock’s spleen under water, so as to remove the grumous-looking material. 30 466 DISSECTION OF THE ABDOMEN. Fis. 157. The trabecular tissue (fig. 157) forms a network through the whole in- terior of the spleen, similar to that of a sponge, which is joined to the external casing, and forms sheaths around the vessels. Its processes or threads are white, flattened or cylindrical, and average from y^otli to ^^^th of an inch : they consist of fibrous and elastic tissues, with a few muscular fibres. The interstices communicate freely together, and contain the proper substance of the sjdeen, and the vessels. Microscopic appearances. The characters of the spleen substance can- not be ascertained without the aid of the microscope. The splenic pulp is a soft red-brown mass, which is lodged in the areol^e of the trabecular structure. Under the microscope this material is seen to be composed of a fine network of ramifying connective tissue corpuscles, with blood-cells in its meshes. The Malpighian corpuscles are small rounded whitish bodies, about g’oth of an inch in diameter, and are connected with the outer coat of the smallest branches of the arteries ; they project into the pulp of the spleen, and are surrounded by it. In structure they are like the lymph follicles of the intestine, consisting of reticular tissue, with lymph corpuscles in its meshes, through which blood-ca])illaries pass. Bloodvessels. The larger branches of the splenic artery are surrounded by sheaths of fibrous tissue in the trabeculic ; but the smallest branches leave the sheathing, and break up into tufts of capil- laries, which open into the fine meshes of the spleen substance. In the smallest branches, with which the Malpighian corpuscles are united, the outer coat is thickened by lymphoid tissue, and is directly continuous with those bodies in structure. The splenic vein begins in the meshes of the splenic pulp by open channels. From the union of these radicles arise small branches, which unite into trunks larger than the accompanying arteries, and issue by the fissure of the spleen ; in their course they receive acces- sory branches, some joining at a right angle. Nerves and lymphatics. The lymphatics are superficial and deep, and enter the glands in the gastro-splenie omentum. In the spleen they begin in the corpuscles of Malpighi, and in the outer coat of the smallest arteries ; they are conveyed to the hilum of the spleen on the vessels. The nerves come from the solar plexus, and surround the artery and its branches. h Drawing of the Tra- becular Structure of THE Spleen of the Ox, at some distance from the hilum. THE LIVER. The liver secretes the bile, and is the largest gland in the body. Its duct opens into the duodenum with that of the pancreas. Dissection (fig. 158). Preparatory to examining the liver, the vessels at the under surface should be dissected out. This proceeding will be facilitated by distending tlie vena cava and vena portie with tow or cotton wool, and the gall-bladder with air through its duct. The several vessels and the ducts are then to be defined, and the gall-bladder to be cleaned. LOBES AND FISSURES OF LIVER. 467 On following outwards tlie left branch of the vena porta3 to the longi- tudinal or antero-posterior fissure, it will be found united anteriorly with the round ligament or the remains of the umbilical vein, and posteriorly with the fine fibrous remnant of the ductus venosus. The liver is of a red-brown color and firm consistence ; and weighs commonly in the adult from three to four pounds (fifty to sixty ounces). Transversely the gland measures from ten to twelve inches ; from front to back between six and seven inches ; and in thickness, at the right end, about three inches ; but this last measurement varies with the spot ex- amined. In shape the liver is somewhat square. It has many named parts, viz., two surfaces, two borders, and two extremities ; and the under surface is further marked by lobes and fosste, and by fissures which contain vessels. The connections and the ligaments of the liver are described at p. 434 and p. 438. Surfaces. On the upper aspect the liver is convex : extending from front to back in the suspensory ligament, which divides the upper surface into two unequal parts, of which the right is the larger. The under sur- face is rendered irregular by lobes, fissures, and fossiu : in contact witli it is the gall-bladder ; and a longitudinal sulcus divides it into a right and a left lobe. Borders. The anterior border is thin, and is marked by two notches : one is opposite the longitudinal sulcus on the under surface before alluded to, and the other is over the large end of the gall-bladder. The posterior border is much thicker at the riglit than at the left end ; and at tlie thick- ened part it touches the right kidney and the diaphragm. Opposite the vertebral column is a hollow in this border ; and the vena cava is partly imbedded in it on the right of tlie spine. Extremities. The right extremity is thick and rounded; and the left is thin and flattened. Lobes. On the under surface the liver is divided primarily into two lobes, a right and a left, by the antero-posterior or longitudinal fissure ; and occupying this surface of the right lobe are three others, viz., the square, the Spigelian, and the caudate lobe : — The left lobe, b, is smaller and thinner than the right, and there is a sliglit dejiression inferiorly where it touches the stomach. The right lobe, a, forms the greater part of the liver, and is separated from the left by the longitudinal fissure on the one aspect, and by the sus- pensory ligament on the other. To it the gall-bladder is attached below ; and the following lobes are projections on its under surface : — The square lobe, c (lobulus quadratus), is situate between the gall- bladder and the longitudinal fissure. It reaches anteriorly to tlie margin of the liver, and posteriorly to the fissure (transverse) by which the ves- sels enter the interior of the viscus. The Spigelian lobe, d, lies beliind the transverse fissure, and forms a roundish projection on the surface. On its left side is the longitudinal fissure; and on its right, the vena cava inferior. The caudate lobe, e, is a slight, elongated eminence, which is directed from the Spigelian lobe behind the transverse fissure, so as to form the posterior boundary of that sulcus. AVhere the fissure terminates this pro- jection subsides in the right lobe. Fissures. Extending horizontally half across the right part of the liver between the Spigelian and caudate lobes on the one hand, and the square 468 DISSECTION OF THE ABDOMEN. lobe on the other, is the transverse or portal fissure. It is situate nearer tlie posterior tlian the anterior border, and contains the vessels, nerves, ducts, and lymphatics of the liver. At the left end it is united at a right angle with the longitudinal fissure. Fig. 158. Under Surface of the Liver. A. Eight, and B, left lobe, c. Quadrate lobe. D. Spigelian, and E, caudate lobe. F. Longitudinal fissure. G. Gall-bladder. a. Vena cava. h. Vena portae. c. Round ligament. d. Obliterated ductus venosus. e. Cominou hepatic duct. /. Cystic duct. g. Common bile duct. k. Hepatic artery. The longitudinal fissure, F, extends from the front to the back of the liver, between the right and left lobes. In the part anterior to the trans- verse fissure lies the remnant of the umbilical vein (c), whicli is called I’ound ligament, and is oftentimes arched over by a piece of the hepatic substance (pons hepatis). In the part behind that fissure is contained a small obliterated cord (c/), the remains of the vessel named ductus venosus in the fmtus. The groove for the vena cava is placed on the right side of the Spigelian lobe, and is freipiently bridged over by the liver. If the cava be opened, two large and some smaller hepatic veins will be observed entering it. Fosscb. On the under surface of the right lobe are three depressions — one for the gall-bladder to the right of tlie square lobe ; another for the colon, near the anterior edge; and a third for the kidney near the posterior border. Vessels of the transverse fssure. The vessels in the transverse fissure, viz., vena portm, hepatic artery and duct, have the following position: the duct is anterior, the portal vein posterior, and the artery between the otlier two. The hepatic duct (fig. IdS, e) is formed by two branches from the liver, one I'rom each lobe, wliich soon blend in a common tube. After a distance of one inch and a half it is joined by the duct of the gall-bladder (/) ; and the union of the two gives rise to the common bile duct (^). STRUCTURE OF LIVER. 469 The hepatic artery {h) is divided into two, one for each lobe, and its branches are surrounded by nerves and lymphatics. The vena portce (h) branches, like the artery, into two trunks for the right and left lobes, and gives an offset to the Spigelian lobe; its left branch is the longest. Foetal condition of the amhilical vein. Before birth the previous um- bilical vein occupies tlie longitudinal fissure, and opens posteriorly into the vena cava; the portion of the vessel behind the transverse fissure re- ceives the name ductus venosns. Branches are supplied from it to both lobes of the liver; and a large one, directed to the right lobe, is continuous with the left piece of the vena portae. Purified or placental blood circu- lates through the vessel at that period. Adrdt state. After birth the part of the umbilical vein in front of the transverse fissure is closed, and becomes eventually the round ligament (fig. 158, c). The ductus venosus is also obliterated, only a thin cord (d) remaining in its place. Whilst the lateral branches, which are in the same line as, and continuous with the left branch of the vena portoB, remain 0 {)en, and subsequently form part of the left division of the vena portic. Occasionally the ductus venosus is found more or less pervious. Structure of the Liver. The substance of the liver consists of small bodies called lobules or acini; together with vessels which are con- cerned both in the production of the secretion, and in the nutrition of the organ. The whole is surrounded by a fibrous and a serous coat. Serous coat. The peritoneum invests the liver almost completely, and adheres closely to the subjacent coat. At certain spots intervals exist be- tween the two, viz., in the fissures occupied by vessels, along the line of attachment of the ligaments, and at the surface touching tlie gall-bladder. The jibrous covering is very thin, but it is rather stronger where the peritoneum is not in contact with it. It invests the liver, and is continu- ous at the transverse fissure with the fibrous sheath (capsule of Glisson) surrounding the vessels in the interior. When the membrane is torn from the surface, it will be found connected with fine shreds entering into the liver. Size and form of the lobules. The lobules (fig. 161, T) constitute the proper secreting substance, and can be seen either on the exterior of the liver, on a cut surface, or by means of a rent in the mass. As thus ob- served, these bodies are about the size of a pin’s head, and measure from J^th to y^gth of an inch in diameter. Closely massed together they pos- sess a dark central point; and there are indications of lines of separation between them, though they communicate by vessels. By means of trans- verse and vertical sections of the lobules, their form will appear flattened on the exterior, but many sided in the interior of the liver. They are clustered around tlie smallest divisions of the hepatic vein, to which each is connected by a small twig issuing from the centre, something like the union of the stalk with the body of a small fruit. To study the minute structure of the lobules, a microscope will be neces- sary ; and the different vessels of the liver should be minutely injected. Constituents of the lobules. Plach lobule is composed of minute hepatic cells, which are arranged web-like amongst the ducts and vessels ; and it is provided with a capillary network of vessels, and with a plexus of the bile duct. Cells of the lobules. The hepatic or biliary cells (fig. 159, a) form the chief part of the lobule ; they are irregular in form, being rounded or 470 DISSECTION OF THE ABDOMEN. many sided, and possess size they vary from jo^ooth to inch. Fiff. 159. bright nucleus, or even more than one. In They are of a yellowish color, and inclose granular particles, together with fat and yellow coloring matter. These nucleated cells adhere together by their surfaces so as to form rows radiating from the centre, with spaces {h) between them for the blood- vessels and ducts. The cells are con- cerned in the secretion of the bile. Vessels of the lohule (fig. 160 , b). The smallest branches of the vena portm, after uniting in a circle around the lo- bule, where they are named interlobular (a), enter its substance, and form therein a network of capillaries (c) near the cir- cumference. A small branch of the hepatic vein {d) occupies the centre of the lobule ; its radicles communicate M'ith the portal network, and it issues from the base of A Magnified Representation of the lobule as the intralohular vein. HepaT'c CEILS „i,h their arrange- radicles of tile bile duCt (fig. ICO, A) begin within the lobule in a fine in- ti. Intercellular spaces. tralobular plcXUS of ductS betv' CCll A. Two lobule.s of the liver showing the plexus of ducts in the interior, near the circum- ference (Kiernau); recent inquiries de- monstrate the existence of a plexus tlu-oughout the lobule. g. Intralobular plexus. /. Intel lobular ducts. e. Small branches of the hepatic ducts. B. Lobules of an injected liver to show the arrangement of the veius. a. Smallest branches of the vena portse end- • ing in the interlobular veins, h. c. Plexus of portal veins Avithiu the lobule. d. Intralobular commeucement of the hepa- tic vein joining the plexus of the portal vein. the hejtatic cells (Chrzonszczewsky) ; they leave tlie lobule at the cir- cumference, and are joined together outside it in the smallest interlobular branches (/). VESSELS AND DUCT OF LIVER. 471 From the arrangement of the vessels, it appears that the portal vein conducts the blood from which bile is secreted ; that the hepatic vein car- ries away the superfluous blood ; and that the secreted bile is received by the plexus of the biliary duct. Vessels of the Liver. Two sets of bloodvessels ramify in the liver : One enters the transverse fissure, and is directed transversely in spaces (portal canals) where it is enveloped by areolar tissue. The other set (hepatic veins) run from the anterior to the posterior border of the liver without a like sheath. The ramifications of these different vessels are to be followed in the liver. The capsule of Glisson is a layer of areolar tissue, which envelops the vessels and the ducts in the transverse fissure. In this sheath the vessels ramify, and in it they are minutely divided before their termination in the lobules. If a transverse section is made of a portal canal, the vessels will retract somewhat into the loose surrounding tissue. The vena portce ramifies in the liver like an artery; and the blood cir- culates through it in the same manner, viz., from trunk to branches. After entering the transverse fissui-e the vein divides into large branches ; these lie in the portal canals or spaces, with offsets of the hepatic artery, the hepatic duct, and the nerves and lym- phatics (fig. IGl, f). Tlie division is repeated again and again until the last branches of the vein (interlobular, fig. 160, 6) penetrate between the lobules; there they unite, and end in the interior as before explained. In the portal canals the offsets of the ve7ia portcE are joined by small vagi- nal and surface veins, which convey blood from branches of the hepatic artery. The hepatic artery (fig. 161, c), whilst surrounded by the capsule, fur- nishes vaginal branches, which ramify in the sheath, giving it a red appear- ance in a well-injected liver, and sup- ply twigs to the coats of the vena portie and biliary ducts, and to the areo- lar tissue : from the vaginal branches a few offsets (capsular) are given to the coat of the liver. Finally the artery ends in fine interlobular branches, from which offsets enter the lobule, and con- vey blood into the network between the branches of the vena portae and hepatic vein (Chrzonszczewsky). The hepatic vein (venae cavae hepaticae) begins by a plexus in the inte- rior of each lobule (fig. 160, d), and its smallest radicle issues from the base of the lobule as tlie intralobular vein ; these are received into the snblobular brandies, which anastomose together, and unite into larger vessels. Finally, uniting with neighboring branches to produce larger trunks, the hepatic veins are directed from before backwards to the vena cava inferior, into which they open by large orifices. Tlie vena3 cavae he- Fig. 161. Vessels in a Portal Canal, and the Lobules of the Liver (Kiernan). 1. Lobules of the liver. P. Branch of the vena portae, with, or, a, vaginal branches which supply inter- lobular offsets. c. Hepatic artery. d. Hepatic duct. i, i. Openings of the interlobular branches of the portal vein. 472 DISSECTION OF THE ABDOMEN. paticoB may be said to be without a sheath, except in the larger trunks ; so that wlien they are cut across the ends remain patent, in consequence of their close connection with the liver structure. Hepatic duct (fig. 160, e). The duct commences in the biliary plexus within the lobules. On leaving the lobules the radicles communicate by the interlobular branches (/) ; and the smaller ducts soon unite into larger vaginal branches (c?), which lie in the portal canals with the other vessels. Lastly, the ducts are collected into a right and a left trunk (fig. 158, e), and leave the liver at the transverse fissure.^ Structure. The moderately-sized hepatic ducts consist of a fibrous coat, lined by a mucous layer with cylindrical epithelium ; and penetrating the wall is a longitudinal row of openings, on each side, leading into sacs, and into branched tubes which sometimes communicate. In the fine inter- lobular ducts the coat is formed by a homogeneous structure, with colum- nar epithelium (Henle). Lymphatics of the liver are superficial and deep. The superficial of the upper surface join the lymphatics in the thorax by piercing the dia- phragm, and end for the most part in the sternal glands; those on the under surface enter chiefly the glands by the side of the abdominal aorta, a few' uniting w'ith the deep lymphatics, and the coronary of tlie stomach. The deep lymphatics accompany the vessels through the liver, and communicate with one of the large contributing trunks of the thoracic duct. Nerves come from the sympathetic and the pneumo-gastric, and ramify w ith the vessels ; but their mode of ending is not ascertained. THE GALL-BLADDER. The gall-bladder (fig. 162) is the receptacle of the bile. It is situate in a depression on the under surface of the right lobe of the liver, and to the right of the square lobe. It is pear-sl'.a})ed, and its larger end (^fundus) is directed forw'ards beyond the margin of the liver ; whilst the smaller end (neck) is turned in the opposite direction, and bends downwards to termidate in the cystic duct by a zigzag part. In length the gall-bladder measures three or four inches, and in breadth rather more than an inch at the w'idest part. It holds rather more than an ounce. By one surface it is in contact with the liver, and on the opposite it is covered by peritoneum. The larger end touches the abdominal wall oppo- site the tip of the cartilage of the tenth rib, w'here it is contiguous to the transverse colon ; and the small end is in contact w'ith the duodenum. Structure. The gall-bladder possesses a peritoneal, a fibrous and mus- cular, and a mucous coat. The serous coat is stretched over the under or free surface of the gall- bladder, and surrounds the large end. The Jihro7(s coat is strong, and forms the framew'ork of the sac ; inter- mixed w ith it are some involuntary muscular fibres., the chief being lon- gitudinal, but others circular. • Aberrant ducts exist between the pieces of the peritoneum in the left lateral ligament of the liver, and in thei)ons bridging over tlievena j)orta? and vena cava ; they anastomose together, and are accompanie) ascends by the side of its accom- panying artery, the right almost vertically, and the left obliquely, to the right side of the body of the fifth lumbar vertebra (the upper part), where it blends with its fellow in one trunk — the vena cava. The right vein is the shortest, and lies at first behind, but afterwards outside the artery of the same name. The left is altogether below the artery of its own side, and crosses beneath the right common iliac artery. Each vein receives the ilio-lumbar, and the lateral sacral branch ; and the common iliac of the left side is joined by the middle sacral vein. 492 DISSECTION OF THE ABDOMEN. The VENA CAVA INFERIOR (fig. 171, w) collects and conveys to the heart the blood of the lower half of tlie body. Taking the origin on the right side of the fifth lumbar vertebra, below the bifurcation of the aorta, this large vein ascends on the right side of the vertebral column, and reaches the heart by perforating the diaphragm. Its connections with the surrounding parts have been already noticed (p. 444), but the description may be referred to, as the position of the branches of tlie aorta to it can be better seen now. Branches. The cava receives parietal branches (lumbar and dia- phragmatic), from the wall of the abdomen and the diapliragm ; and vis- ceral branches from the testicle, the kidney, the suprarenal body, and the liver. The veins belonging to the digestive apparatus, viz., the intestinal canal, the spleen, and the pancreas, are united to form the vena portje (p. 448) ; and the blood contained in those veins reaches the cava by the venae cavae hepaticie, after it has circulated througli the liver. The spermatic vein (fig. 171, o) enters the abdomen by the internal abdominal ring, after forming tlie spermatic plexus in the cord (p. 484). At first there are two branclies in the abdomen, which lie on the sides of tlie spermatic artery; but these soon join into one trunk. On the left side it ofiens into the renal vein at right angles, and a small valve exists sometimes over the aperture ; on the right side it enters the inferior cava below the renal vein. As the vein ascends to its destination, it receives one or more branches from the wall of the abdomen, and from the fat about the kidney. In the female this vein (ovarian) has the same ending as in the male, and it forms a plexus in the broad ligament of the uterus. Valves are absent from the vein and its branches, but occasionally there is one at its union with the renal. The renal or eniulgent vein (fig. 171, ti) is of large size, and joins the vena cava at a right angle. It commences by many branches in the kid- ney ; and the trunk resulting from their union is superficial to the renal artery. Tlie rifflit is the shortest, and joins the cava higher up usually than the other. The left vein crosses the aorta close to the origin of the superior mesenteric artery : it receives separate branches from the left spermatic and suprarenal veins. The suprarenal vein is of considerable size when it is compared with the body from which it comes. The right opens into the cava, and the left into the renal vein. The hepatic veins enter the vena cava where it is in contact with the liver. These veins are described in the dissection of the liver (p. 4G8). The lumbar veins correspond in number and course with the arteries ot the same name : they will be dissected after. The diaphragmatic veins (inferior), two with each artery, spring from the under surface of the diaphragm. They join the cava either as one trunk or two. DEEP IMUSCLES OF THE ABDOMEN. The deep muscles in the interior of the abdomen are the psoas, iliacus, and quadratus lumborum. The PSOAS MAGNUS (fig. 171, ^) reaches from the lumbar vertebras to the femur, and is situate partly in the abdomen and partly in the thigh. PSOAS AND ILTACUS MUSCLES. 493 The muscle arises from the front of the transverse processes of the lumbar vertebrae; from the bodies and intervertebral disks of the last dorsal and all the lumbar vertebrae by five fieshy pieces — each piece being connected with the intervertebral substance and the borders of two con- tiguous vertebrae, and with tendinous bands over the bloodvessels opposite the middle of the vertebrae. The fibres give rise to a roundish belly, which gradually diminishes towards Pou[)art’s ligament, and ends inte- riorly in a tendon on the outer aspect, which receives fibres of the iliacus, and passes beneath Poupart’s ligament to be inserted into the small tro- chanter of the femur. The abdominal part of the muscle has the following connections: — In front {ire the internal arch of the diaphragm, the kidney with its vessels and duct, the spermatic vessels, and the genito-crural nerve, and, near Poupart’s ligament, the ending of the external iliac artery. Posteriorly the muscle is in contact with the transverse processes, with part of the quadratus lumborum, and with the innominate bone. The outer border touches the quadratus and iliacus; and branches of the lumbar plexus issue from beneath it. The inner border is partly con- nected to the vertebra^, {ind is partly free along the m{irgin of the pelvis: — along the attached part of this border lies the sympathetic nerve, with the cava on the right, and the aorta on the left side; along the free or pelvic part are the external iliac {irtery and vein. Action, If the femur is free to move it is raised towards the belly; and as the flexion proceeds, the limb is rotated out by the attachment of the muscle to the trocluinter minor. The psoas is alw{iys combined with the ili{icus in flexion of the hip-joint. When the lower limbs are fixed the two muscles will draw down the lumbcar part of the spine, {ind bend the hip-joints, as in stooping to the ground. One muscle under the same circumstances can incline the spine laterally. The PSOAS PARVUS (fig. 171, is a small muscle with a long and fliit tendon, which is placed on the front of the large psoas, but is rarely pre- sent. Its fibres arise from the bodies of the last dorsal iind first lumbiir vertebrie, with the intervening fibro-cartilage. Its tendon becomes broader inferiorly, and is inserted into the ilio-pectineal eminence and the brim of the pelvis, joining the fascia over the iliacus muscle. Action. If the spine is immovable the two muscles will make tense the pelvic fascia. The pelvis being fixed they may assist in bending the lumbar part of the spinal column. The ILIACUS MUSCLE (fig. 171, **) occupies the iliac fossa on the inner aspect of the hip-bone, and is blended inferiorly with the psoas. It is triangular in form, and has a fleshy oriejin from the iliac fossa and the ilio-lumbar ligament, from the base of the sacrum, and from the capsule of the hip-joint in front. The fibres pass inwards to the tendon of tlie psoas, uniting with it even to its insertion into the femur, but some reach separately the femur near the sm{ill trochanter. Above Poupart’s ligament the muscle is covered by the iliac fascia; but over the right iliacus is placed the ciecum, and over the left, the sigmoid flexure. Beneath it are the innominate bone and the c.apsule of the hip- joint; and between it and the grooved anterior margin of the bone, above the joint, is a bursa. The inner m{irgin is in contact with the pso{is and the anterior crural nerve. The connections of the united psoas and iliacus below Poupart’s ligament are given with* the dissection of the thigh. 494 DISSECTION OF THE ABDOMEN. Action. The iliacus flexes the hip-joint with the psoas when the femur is movable, and bends forwards the pelvis when tlie limb is flxed. In consequence of its union with the psoas, the two are described as the flexor ot the hip-joint by Tlieile. The QUADRATus LUMBORUM (fig. 171 is a short thick muscle be- tween the crest of the hip-bone and the last rib. About two inches wide inferiorly, it arises from the ilio-vertebral ligament, and from the iliac crest of the hip-bone behind, and an incli outside that band. The fibres ascend to be inserted by distinct fleshy and tendinous slips into the apices of the transverse processes of the four upper, or all the lumbar vertebras ; and into the body of the last dorsal vertebra, and the lower border of the last rib for a variable distance. This muscle is encased in a sheath derived from the fascia lumborum. Crossing the surface are branches of the lumbar plexus, together with tlie last dorsal nerve and its vessels. Beneath the quadratus is the mass of the erector spinas muscle. Action. Both muscles keep straight the spine (one muscle antagonizing the other) ; and by fixing the last rib they aid in the more complete con- traction of the diaphragm. One muscle will incline laterally the lumbar part of the spine to the same side, and dejJress the last rib. Fascia of the quadratus. Covering the surface of the quadratus is a thin membrane, which is derived from the hinder aponeurosis of the trans- versalis abdominis (fascia lumborum, p. 357); it passes in front of the quadratus to be fixed to the tips and borders of the lumbar transverse pro- cesses, to the ilio-lumbar ligament below, and to the last rib above. This fascia forms the thickened band called ligamentum arcuatum externum, to which the diaphragm is connected. Fascia of the iliacvs and psoas. A fascia covers the two flexor muscles of the hip-joint, and extends in different directions as far as their attach- ments. Over the iliacus muscles the membrane is thickest ; and a strong accession is received from the tendon of the small psoas. Its disposition at Poupart’s ligament, and the part that it takes in the formation of the crural sheath, have been before explained (p. 428). Op})Osite the pelvis the membrane is inserted into the brim of that cavity for a short distance, and into the hip bone along the edge of the psoas. Opposite the spinal column it becomes thin, and is .fixed on the one side to the lumbar vertebrm and the ligamentum arcuatum internum, but is blended on the other with the fascia on the quadratus. The fascia should be divided over the psoas on the left side, and reflected towards the brim of the pelvis. jDissection. The student is now to clean the lymphatic glands lying along the vertebra3, and to trace upwnrds some lymphatic vessels to the thoracic duct. To show the origin of the duct, the diaphragm is to be divided over the aorta, and its pillars are to be thrown to the sides ; a piece may be cut out of the aorta opposite the first lumbar vertebra. The beginning of the duct (chyli receptaculum), and of the vena azygos, may be well seen ; and the two may be followed upwards into the thorax. On the left side the student may trace the splanchnic nerves and the small vena azygos through the pillar of tlie diapliragm ; and may show the trunk of the symjiathetic nerve entering the abdomen beneath the arch over the psoas muscle. SPINAL AND SYMPATHETIC NERVES. 495 Lymphatic glands. A chain of glands is placed along the side of the external iliac artery, and along the front and sides of the lumbar vertebra; they are connected by short tubes, which increase in size and diminish in number, until at the upper part of the lumbar vertebrae three or four trunks unite in the thoracic duct. Into the glands the lymphatics of the lower limbs, and those of the viscera and wall of the abdomen are received. Receptaculiim chyli (Pecquet). The thoracic duct begins in the ab- domen by the union of three or four large lymphatic vessels. Its com- mencement is marked by a dilatation, which is placed on the right side of the aorta, about opposite the first lumbar vertebra. The duct enters the thorax by passing through the diaphragm with the aorta. Beginning of the azygos veins. The right vein (vena azygos major) begins opposite the first or second lumbar vertebra by a small branch, which is united with a lumbar vein. It enters the thorax with the tho- racic duct and the aorta, to the right of which it lies. The left or small azygos vein begins on the left side of the spine, joining one of the lumhar veins, and passes through the pillar of the diaphragm, or through the aortic opening. The anatomy of these veins is given in the description of the thorax, p. 338. Section VI. SPINAL AND SYMPATHETIC NERVES. The spinal nerves of the loins are united in a plexus, and supply the limb and the contiguous parts of the trunk. Dissection. The lumbar nerves and their plexus are to be learnt on the left side, although the woodcut shows them on the right side ; and to bring them into view, the dissector should cut through the external iliac vessels, and afterwards scrape away the psoas. P"or the most part the fleshy fibres may be removed freely ; but a small branch (accessory of the obturator) should be first looked for at the inner border of the muscle. In the sub- stance of the quadratus lumborum a communication may be sometimes found between the last dorsal and the first lumbar nerve. The cord of the sympathetic nerve lies along the edge of the psoas, and offsets of it join the spinal nerves ; these are to be followed back along the lumbar arteries. On the right side the psoas is to be left untouched, in order that the place of emergence of the different nerve branches from it may be noticed. Lumbar Spinal Nerves. The anterior primary branches of the lum- bar nerves enter the lumbar plexus, with the exception of the last. F'ive in number, they increase in size from the first to the last, and are joined by filaments of the sympathetic near the intervertebral foramina. Before entering the plexus they supply branches to the psoas and quadratus lum- borum muscles. The fifth nerve (fig. 177) receives a communicating branch from the fourth, and is to be followed into the pelvis to its junction with the sacral plexus. After the two are united, the name lumbosacral is applied to 496 DISSECTION OF THE ABDOMEN. the common trunk ; and from this, before it enters the sacral plexus, arises the superior gluteal nerve (^). The LUMBAR PLEXUS (tig. 172) is formed by the intercommunication of the first four lumbar nerves. Contained in the substance of the psoas near the posterior surface, it consists of communicating loops between the several nerves, and increases in size from above downwards, like the in- dividual nerves. Superiorly it is sometimes united by a small branch with the last dorsal nerve ; and inferiorly it joins the sacral plexus through the large lumbo-sacral cord. Fig. 172. а. External iliac artery, cnt across. б. Thoracic duct. c. Azygos vein. Nerves : The figures 1 to .'5 naark the trunks of the five lumbar nerves. d. Splanchnic nerves. e. Last dorsal. /. Ilio-hypogastric. g. Ilio-inguinal. h. Genito-crural. i. External cutaneous. k. Anterior crural. l. Accessory to obturator. n. Obturator. o. Gangliated cord of the sympathetic. DissECxrox OF the Lumbar Plexus and its Branches. (Illustrations of Dissections.) The branches of the plexus are six in number, and supply the lower part of tlie abdominal wall and muscular covering of the spermatic cord, the fore part of the thigh, and the inner side of the leg. The first two branches (ilio-hy[)ogastric and ilio-inguinal) end as cutane- ous nerves of the buttock, lower part of the abdomen, and the scrotum. a. The ilio-hypogastric branch (fig. 172, /*) is derived from the first nerve, and tipjiears at the outer border of the jisoas muscle, near the ujiper part. It is directed over the quadratus lumborum to the iliac crest, and enters the wall of the abdomen by penetrating the transversalis abdominis. LUMBAR PLEXUS AND BRANCHES. 497 Its termination in the integuments of the buttock and abdomen, by means of an iliac and a hypogastric brancli, has been already mentioned (p. 41 G). b. The ilio-inguinal branch (^) arises with the preceding from the first nerve, and issues from tlie psoas nearly at the same spot. Of smaller size than the ilio-hypogastric, this branch courses outwards over the cpjadratus and iliacus muscles towards the front of the crest of the hip bone, where it pierces the transversalis abdominis. The farther course of the nerve in tlie abdominal wall, and its distribution over the scrotum and the groin, are before noticed (p. 416). c. The genito-crural nerve (h) is distributed to the cremaster muscle and the limb. It arises from the second lumbar nerve, and from the con- necting loop between the first two ; it pierces the fibres of the psoas, and descending on the surface of the muscle divides into the two following pieces. Sometimes the nerve is divided in the psoas, and the pieces per- forate separately the muscle. The cremasteric branch descends on the external iliac artery, and fur- nishes offsets around it : it passes from the abdomen with the spermatic vessels, and is distributed in the cremaster muscle. In the female the nerve is lost in the round ligament. The crural branch issues beneath Poupart’s ligament to supply the in- tegument of the thigh. d. The external cutaneous nerve of the thigh (^) arises from the second nerve of the plexus, or from the loop between it and the third, and appears about the middle of the outer border of the psoas. The nerve then crosses the iliacus to the interval between the anterior iliac spinous processes, and leaves the abdomen beneath Poupart’s ligament, to be distributed on the outer aspect of the limb. e. The anterior crural nerve (k) is the largest offset of the plexus, and supplies branches mainly to the extensor muscles of the knee joint, and to the teguments of the front of the thigh and inner side of the leg. 4'aking origin from the third and fourth nerves, and receiving a fasciculus also from the second, this large trunk appears towards the lower part of the psoas, where it lies between that muscle and the iliacus. It passes from the abdomen beneath Poupart’s ligament ; but before the final branch- ing in the thigh, the nerve furnishes the following twigs : — Some small branches are furnished to the iliacus from the upper part of the nerve. ' A branch to the femoral artery^ whose place of origin varies much, is distributed around the upper part of that vessel. f. The obturator nerve {ii) appertains to the adductor muscles of the thigh. Derived from the third and fourth nerves in the plexus, it is di- rected beneath the psoas to the inner or pelvic border; escaped from be- neath the muscle the nerve crosses the pelvic cavity below the external iliac, but above the obturator vessels, and enters the thigh through the aperture in the upper part of the thyroid foramen. Occasionally the ob- turator gives origin to the following branch: — The accessory obturator nerve il) arises from the trunk of the obturator, or from the third and fourth nerves of the plexus. Its course is along the inner border of the psoas beneath the investing fascia, and over the hip bone to the thigh, where it ends by joining the obturator nerv^e, and sup- plying the hip joint. Gangliated cord op the sympathetic. The lumbar part of the gangliated cord of the sympathetic in the abdomen is placed on the side 32 498 DISSECTION OF THE ABDOMEN. of the spinal column (fig. 172) ; it lies along the inner border of the psoas muscle, nearer the front of the vertebra3 than in the thorax, and is some- what concealed on the right side by the vena cava. The cord possesses four or five oblong ganglia opposite the bodies of the vertebrae, which sup- ply connecting and visceral branches. Connecting branches. From each ganglion two small branches are di- rected backwards along the centre of the body of the vertebra, with the lumbar artery ; these unite with one or two spinal nerves near the inter- vertebral foramen. The connecting branches are long in the lumbar region in consequence of the gangliated cord being raised by the psoas muscle to the fore part of the vertebrae. Branches of distribution. Most of the internal branches throw them- selves into the aortic and hypogastric plexuses, and so reach the viscera indirectly. Some filaments enter the vertebrae and their connecting liga- ments. Last dorsal nerve (fig. 172, e). The anterior primary branch of the last dorsal resembles the intercostal nerves in its distribution, but differs from them in not being contained in an intercostal space. Lying below the last rib, the nerve is directed outwards across the upper part of the quadratus lumborum, and beneath the fascia covering that muscle, as far as the aponeurosis of the transversalis abdominis (fascia lumborum); here it enters the wall of the abdomen, and ends in an abdominal and a cuta- neous branch (p. 416). The lowest intercostal artery accompanies it. Near the spine it furnishes a small branch to the quadratus muscle ; and it may communicate by means of this with the first lumbar nerve. The LUMBAR ARTERIES of the aorta (p. 489), are furnished to the Back, the spinal canal, and the wall of the abdomen : they resemble the aortic intercostals in their course and distribution. Commonly four in number on each side, they arise opposite the centre of the lumbar vertebrae, and the vessels of opposite sides are sometimes joined in a common trunk ; they then pass backwards beneath the pillar of the diapliragm and the psoas, to reach the interval between the transverse processes, where each ends in an abdominal and a dorsal branch. The arteries of the right side lie beneath the vena cava. The dorsal branch continues to the Back between the transverse pro- cesses, and supplies an offset to the spinal canal (pp. 368, 384). The abdominal branches are directed outwards beneath the quadratus lumborum, and enter the posterior part of the abdominal wall, where they anastomose with the lower intercostal above, and with the circumflex iliac and ilio-lumbar arteries below : these branches supply the psoas and quad- ratus muscles; and the last furnishes an offset to tlie teguments with the ilio-hypogastric nerve. The LUMBAR VEINS are the same in number, and have the same course as the arteries. Commencing by the union of a dorsal and an abdominal branch at the root of the transverse process, each trunk is directed for- wards to the vena cava. They open into the posterior part of the cava, either singly, or conjointly with those of the opposite side. On the left side the veins are longer than on the right, and pass beneath the aorta. Around the transverse processes, and beneath the psoas muscle, the lum- bar veins communicate freely with one another, with the ilio-lumbar, and sometimes with the common iliac, so as to form a plexus of veins. Issuing from the upper part of the plexus is a small branch, tlie ascending lumbar vein., which joins the azygos vein of the corresponding side of the body. CAVITY OP THE PELVIS The cavity of the pelvis is a part of the general abdominal space (p. 431), and is situate below the brim or inlet of the true pelvis. Boundaries. Tlie space is surrounded by the firm bony ring of the pelvic bones : it is bounded behind by the sacrum and the coccyx, with the pyriformis muscles and the sacro-sciatic ligaments ; and laterally and in front, by the innominate bones covered by tlie obturator muscles. Inferiorly, or towards the perinaeum, the cavity is limited by tlie fascia reflected from the wall to the viscera, and by tlie levatores ani and coccygei muscles : only in this last direction, where the bounding structures are movable, can alterations be made in the size of the space. Contents. In the pelvis are contained the urinary bladder, the lower end of the large intestine or the rectum, and some of the generative or- gans, according to the sex. All the viscera possess vessels, nerves, and lymphatics ; and the serous membrane is reflected over them. Section I. PELVIC FASCIA AND MUSCLES OF THE OUTLET. On the wall of the pelvis is a thin fascia (pelvic) which extends from the brim to the outlet, and covers the obturator muscle. Dissection. To bring into view the pelvic fascia, the internal iliac ves- sels, and the psoas (if this has not been removed in the dissection of the lumbar plexus), are to be taken away on the left side of the body. The obturator vessels and nerve are to be cut through on the same side ; and the peritoneum being detached from the wall of the pelvis, the fascia will be seen on scraping away with the handle of the scalpel a large quantity of fat. By this proceeding the membrane is dissected in its upper half, or as low as the situation of a piece of fascia (recto-vesical) which is at- tached to the viscera. To display the lower half, the student must raise the outlet of the pelvis ; and, should the perinreum be undissected, the fat must be taken from the ischio-rectal hollow. The lower part of the fascia will now appear on the outer side of that fossa, as it covers the obturator muscle. An additional step for showing the arrangement of the fascia may be taken, by removing the external obturator muscle and the obturator mem- brane, and then scraping away through the thyroid hole the obturator in- ternus muscle, so as to look at the fascia through that aperture. 500 DISSECTION OF THE PELVIS. The PELVIC FASCIA is a thin membrane in close contact with the obturator muscle, and is fixed to the bone around the attachment of the fleshy fibres, so that it might be called the sj;ecial fascia (obturator) of that muscle. Superiorly it is fixed into the brim of the pelvis for a short distance at the lateral aspect of the cavity. In front of that spot it does not extend so high as the brim, but is inserted into the bone around the attachment of tlie muscle, except opposite the hole for the obturator vessels and nerve, where it is united with the obturator membrane. Inferiorly the fascia is attached to the hip bone along the side of the pubic arch, and to the margin of the great sacrosciatic ligament where the obturator internus issues from the pelvis. The outer surface of the fascia is in contact with the obturator muscle. The inner surface corresponds above with the cavity of the pelvis, and below, with the ischio-rectal fossa. With this surface the thin membrane (recto-vesical) supporting the viscera of the pelvis is united ; the place of union being indicated, on looking into the pelvis, by a whitish line near to, and on a level with the ischial spine. At the posterior border of the obturator muscle the fascia is joined by a thin membrane (fascia of the pyriformis) which coveis the ])yriformis muscle and the sacral plexus, but is beneath the iliac vessels by branches of which it is perforated. The recto-vesical fascia may be now seen in part ; but it will be better displayed after the hip bone has been taken away. Dissection. To obtain a side view of the pelvis it will be necessary to detach the left innominate bone. The pelvic fascia is first to be separated from the bone and the obturator muscle. The innominate bone is next to be sawn through, in front, rather external to tlie symphysis, and, behind, at the articulation with the sacrum. After the bone has been pulled some- what away from the rest of the pelvis, the ischial spine with the recto- vesical fascia attached to it may be cut off with a bone-forceps ; and the rest of the bone may be then removed by cutting through the })yriformis muscle, the vessels and nerves passing through the sacro-sciatic notch, and any other structure that may retain it. A block is afterwards to be placed beneath the pelvis. The bladder is to be moderately distended Muth air through the ureter, and the urethra is to be tied. Some tow is to be introduced into the rectum, also into the vagina if it is a female pelvis ; and a small piece is to be })laced in the pouch of peritoneum between the bladder and the rectum. After the viscera are thus made pi-ominent, the ischial spine and the recto-vesical fascia should be raised with hooks whilst the levator ani and coccygeus muscles below it are cleaned. Parts closing the pelvis below. In addition to the recto- vesical fascia, the following parts close the pelvic cavity on each side, between the sacrum and the pubic sympliysis. Behind, the student will meet with the pyriformis passing through the great sacro-sciatic notch, with the gluteal vessels and nerve above it. Abjxt comes the coccygeus muscle, c, on the small sacro-sciatic ligament, between the ischial spine and the coccyx : one border of the muscle reaches towards the pyriformis, the other to the levator ani ; and between its hinder border and the pyriformis lie the sacral plexus of nerves (f), and the sciatic and pudic vessels. Tlie greater part of the rest of the pelvic outlet is closed by the levator ani, D, which extends forwards from the coccygeus to the symphysis pubis. PARTS IN OUTLET OF PELVIS. 501 It meets its fellow inferiorly, but the muscles of opposite sides are sepa- rated in front by the urethra, with the vagina in thafemale ; and the inter- val between them is closed by the triangular ligament of the perineum, h. The COCCYGEUS MUSCLE (fig. 173, is flat and triangular, and assists to close the outlet of the pelvis. It arises from the upper part of the ischial spine, and some fibres are attached to the small sacro-sciatic ligament. Widening as it passes inwards the muscle is inserted mio ttie side, and the contiguous anterior surface of the coccyx, and into the side of the lower piece of the sacrum. Fig. 173. Side view of the Muscles in the outlet of the Pelvis (Illustrations of Dissections). Muscles : A. Gluteus maximus, cut. B. Psoas and Iliacus, cut. c. Coccygeus. D. Levator ani. F.. External and sphincter. F. Ejaculator urinse. G. Ischial spine, cut off. H. Triangular ligament. Arteries : a. External iliac artery, cut. b. Its accompanying vein. c. Obliterated hypogastric cord, d. Upper vesical, and e. Lower vesical. /. Internal pudic. Nerves : 1. Sacral plexus. 2. Inferior hemorrhoidal. 3. Pudic. The inner surface looks to the pelvis, and is in contact with the rec- tum on the left side; the opposite surface rests on the small sacro-sciatic ligament. The upper or hinder border is contiguous to the pyriformis muscle, vessels and nerves intervening ; and the anterior or lower border is parallel with the levator ani muscle. Action. Uniting in its action with the hinder fibres of the levator ani, the muscle will draw slightly forwards the coccyx. The LEVATOR ANI (fig. 173, ’“) is a thin flat muscle, which is attached above to the side of the pelvis, and descends below into the outlet of the cavity, where it joins its fellow and supports the viscera. , It arises anteriorly by fleshy fibres from an oblique line above the ob- turator internus ; lower down from the fascia on that muscle, and from tlie back of the triangular ligament. Posteriorly it is fixed to the lower and inner surface of the ischial spine. And between those osseous attach- ments the muscle takes origin from the under part of the recto-vesical fas- cia, but not in a straight line. All the fibres are directed downwards to 502 DISSECTION OF THE PELVIS. be inserted after the following manner : The anterior, the longest, descend by the side of the prostate and join, in front of the rectum, with the mus- cle of the opposite side in the central point of the perinoeum ; the middle fibres blend with the side of the rectum ; whilst the posterior meet the opposite muscle behind the gut, and are attached in part to the side of the coccyx (p. 390). The anterior fibres of the levator are in contact with the triangular perineal ligament f and there is an interval between the two muscles, Avliich allows the urethra, with the vagina in the female, to pass from the pelvis. The posterior border is parallel to the coccygeus muscle. The upper surface is contiguous to the recto- vesical fascia ; and the under sur- face looks to the perinauim (ischio-rectal fossa). The two muscles, by their union, form a fleshy layer or diaphragm across the outlet of the pel- vis, similar to that which separates the abdomen from the chest ; this par- tition is convex below and concave above, and gives passage to the rec- tum. Action. By the union of the muscles of opposite sides below the urethra this tube can be raised, and compressed during their contraction. Whilst the urine is flowing the fibres are passive, but towards the end of micturi- tion they contract suddenly, and help the other muscles in clearing the passage. As the levatores descend by the side of the vesiculos seminales, and the prostate, they will compress and evacuate the contents of those viscera. The hindmost fibres, wliich are fixed to the coccyx, will assist the coc- cygeus in moving forwards that bone. Dissection. The recto-vesical fascia will be seen by detaching the fleshy fibres of the levator ani and the coccygeus at their origin, and throwing both downwards. The thin membrane descends on the levator ani to the side of the bladder and the rectum, and sends downwards sheaths around the prostate and the gut. To demonstrate those sheaths one incision is to be made along the prostate, and another along the lower end of the rectum, below the fascia ; and the tubes are to be isolated from the viscera. Tlie recto-vesical fascia supports and partly invests the viscera of the pelvis. Covering the pelvic surface of the levator ani it is fixed above, like that muscle, to the wall of the pelvis in front and behind, and between those attachments it joins the pelvic fascia. Below it meets the fascia of the oi)posite side, in the centre of the pelvis, and forms a partition across th(5 cavity, like that of the levatores ani, which is perforated by the blad- der and the rectum. The partition is supported anteriorly by being fixed to the pubes, and posteriorly, where it blends witli the fascia on the cocy- geus, by being inserted into the coccyx : it is concave above and convex below, and divides the cavity of the pelvis from the perinteal space. This septal piece is attached to the viscera which pierce it, forming ligaments for them ; and from the under surface tubes are prolonged on the rectum and the prostate. Tlie sheath on the rectum incloses the lower three inches of the intestine, and gradually becomes very thin towards the anus ; between it and the intestine are interposed the branches of the upper hemorrhoidal vessels, witli a layer of fat. ' The anterior part of the muscle which descends by the side of the prostate, and unites with its fellow Ixdow the membranous part of the urethra, thus supporting that canal as in a sling, is named sonietinies levator seu compressor prostates. VISCERA IN THE MALE. 503 On the prostate the sheath is thinner than on the rectum, and is con- tinued forwards to the apex of that body, where it blends with the trian- gular ligament of the urethra : it is separated from the capsule of the prostate by a jdexus of veins, and by some small arteries. In the female the fascia has much the same arrangement as in the male ; but the vagina perforates the membrane, and receives a tube from it, like the prostate. The true ligaments of the bladder are two on each. side, anterior and lateral, and are parts of the recto-vesical fascia. The anterior reaches from the posterior part of the pubes to the upper surface of the prostate, and the neck of the bladder ; it is a narrow white band, and incloses some muscular fibres of the bladder. Between the ligaments of o|)posite sides, the recto-vesical fascia dips down to reach the triangular ligament of the perinaeum, and closes the pelvis between the levatores ani. The lateral ligament is a piece of the same fascia, which is fixed to the upper border of the prostate gland, to the side of the bladder close above the vesicula seminalis, and to the back of the bladder between the vesi- culm ; from this part of the fascia an offset is continued downwards over the vesicula seminalis, so as to join a like piece from the other side, and form a slieath for those bodies. There are other ligaments of the bladder (false ligaments), which are derived from the peritoneum investing it, and will be described in the fol- lowing Section. Ligament of the rectum. On each side of the rectum is a strong wide {fiece of the recto-vesical fascia, which is connected externally to the ischial part of the hip bone, and supports that viscus like the bladder. Section II. CONNECTIONS OF THE VISCERA IN THE MALE. Directions. If the student dissects a female pelvis, he will find the description of it at page 509. Contents and position (fig. 174). The viscera in the cavity of the male pelvis are, the lower end of the large intestine (rectum) ; the bladder with its excretory tube — the urethra ; together with some generative organs. Tluise liave the following relative situation : — The rectum (k) is behind all, and takes a curved course, with the con- vexity backwards, along the front of the sacrum and coccyx. The bladder (a) is placed in the concavity of the rectum, its neck being surrounded by the prostate gland (5) ; and the urethra (c?) curves forwards from it above the intestine. Beneath the bladder — between it and the rectum — are the little seminal sacs {g) with the vasa deferentia/. Some of these organs are partly surrounded by the })eritoneum. Dissection. All the recto-vesical fascia, except the anterior true liga- ment of the bladder, may be taken from the prostate and rectum. The obliterated (hypogastric) cord from the internal iliac artery should be fol- lowed forwards along the bladder from the back of the pelvis ; and the branches of the same artery to the bladder should be cleaned. AVhen the 504 DISSECTION OF THE PELVIS. fat lias been cleared from tlie rectum without injuring its arteries, the pouch of the peritoneum, in which tow has been placed, will be brought into vicM^, with the ureter (h) passing to the bladder across its side. The part of the lladder below the peritoneum is to be cleaned, and the vas deferens (/), which lies on the lateral aspect of the viscus, is to be followed down to the seminal sac. Take av/ay with care the remains of the sheath of the vesicula seminalis, defining at the same time the vas deferens inside the latter. The 'peritoneum does not envelop the viscera in the pelvis so completely as in the upper part of the abdomen. After partly surrounding the upper portion of the rectum, and fixing it by a process — meso-rectum, the mem- brane clothes the back of the bladder, projecting for some way between this viscus and the rectum, where it forms the recto-vesical pouch : on each side the serous membrane is arrested by the obliterated hypogastric artery, and gives rise to a fold, the posterior ligament of the bladder. It covers the posterior surface, and each lateral region of the bladder as far forwards as the obliterated hypogastric ; but at that cord it is reflected to the wall of the pelvis and abdomen. All the anterior surface of the blad- der is therefore uncovered by peritoneum ; and when the bladder is dis- tended it rises above tlie pubes, so as to allow of its being punctured in front without injury to the serous membrane. The recto-vesical pouch is wide behind, where it corresponds with the interval between the iliac arteries, and is narrow in front between the rectum and the bladder. Anteriorly it extends slightly into the interval between the vesiculac seminales, and ends usually about one inch and a half from the tip of the coccyx. The distance of the pouch from the anus is commonly about four inches ; but it will vary with the state of the bladder, for if this viscus is distended the peritoneum will be raised, and removed farther from the end of the intestine. False ligaments of the Madder. Where the peritoneum is reflected from the bladder to the pelvic wall, it gives rise to a wide piece of mem- brane, which constitutes the false ligaments of that viscus, tliough without any subdivision of it into pieces. These are said to be five in number — two posterior, two lateral, and one superior. The posterior ligament (one on each side) reaches from the back of the pelvis to the bladder, and contains the obliterated hypogastric artery, the ureter, and smaller vessels, and nerves. Between these is the hollow of the recto-vesical pouch. The lateral ligament., also one on each side, the widest, is reflected from the side of the bladder to the iliac-fossa and the wall of the pelvis. Along its line of attachment to the bladder is the obliterated hypogastric artery. The superior ligament is prolonged from the top of the . bladder to the abdominal wall, along the remains of the obliterated hypogastric vessels. The RECTUM, or the lower part of the great intestine (fig. 174, 4-) ex- tends from the articulation between the sacrum and the left hip bone to the anus, and is kept in place by the peritoneum, the recto-vesical fascia, and the levatores ani. Idie intestine is about eight inches long, and has a winding course, for it follows the curve of the sacrum and coccyx: it is divided into three parts — upper, middle, and lower. The upper part., longer than the others, extends obliquely from the sacro-iliac articulation to the centre of the third piece of the sacrum. Sur- rounded almost entirely by the ])eritoneuni, it lies against the sacrum, and on the pyriformis muscle and sacral plexus of the left side. In contact RECTUM. 505 with it, are the branches of the left internal a^terj, and the left ureter. In some bodies this part of the intestine is much curved to the right side.^ The middle piece lies beneath the bladder, and reaches to the tip of the coccyx: it is about three inches in length, and is covered by ])eritoneum bn the front and sides above, but only in front below. Resting on it is the triangular part of the bladder, with the back of the prostate and the Vesiculm seminales and vasa deferentia; and beneath it are the sacrum and coccyx. On each side is the coccygeus muscle. Fig. 174. Side view of the а. Urinary bladder. б. Prostate. c. Membranous part of the urethra. d. Spongy part of the urethra. e Crus penis, detached. /. Vas deferens. issECTED Male Pelvis. g. Vesicula seminalis. h. Ureter. i. Recto-vesical fascia. h. Rectum. 1. Levator ani, cut. The lower part is about an inch and a half long, and is curved from the tip of the coccyx to the anus: at first it is dilated, but at the anus it is contracted. Tliis end of the intestine is without peritoneal covering, and is supported by the lower part of the triangular ligament of the urethra, and by the leva tores ani muscles. Above the extremity of the rectum (in this position of the body) are the fore part of the prostate, the membranous part of the urethra, and the ' It is not uncommon to see the rectum on the right side of the sacrum. In the dissecting-room of University College in one winter (1854-1855), I saw three ex- amples of the rectum in that situation. In two bodies the lower end of the left colon crossed the spine at the top of the sacrum, and the rectum descended through the pelvis, on the right of the middle line, to the end of the coccyx. In the third the large intestine crossed the spine twice, once at top of the sacrum, and again about the middle of that bone. 506 DISSECTION OF THE PELVIS. bulb of the corpus spongiosum urethroe ; but as the gut recedes from the urethra tliere is an angular interval left between them. The levatores ani muscles descend on its sides, and unite beneath it, supporting it in a sling; and the sphincter muscles surround the aperture. Sometimes the end of the intestine within the anus is very much enlarged, especially in women and old men ; and in that condition in the male it rises up on each side of the prostate. The URINARY BLADDER (vesica urinaria) is situate in the fore part of the pelvis (fig. 174, a), and is the receptacle for the fluid secreted by the kidneys. When the bladder is contracted it is flattened, and of a triangular form, and lies against the anterior wall of the pelvis; but when distended it be- comes of a conical shape, with the larger part towards the rectum, and the apex to the abdominal wall. In distension during life it is slightly curved over the anterior part of the pelvis, as it projects above the bone ; and if a line through its centre were prolonged, it would touch anteriorly the abdominal wall somewhere (according to the distension) between the umbilicus and the pubes, and posteriorly the end of the sacrum or the coccyx. The position and form of the bladder are not the same in early life as in the adult. For in the child this viscus rises above the brim of the pelvis into the hypogastric region of the abdomen, and the cervix is the lowest part. But in the adult the bladder is contained within the space inclosed by the pelvic bones, and the base projects inferiorly. The organ is maintained in position by the recto-vesical fascia and the peritoneum, which form its ligaments (pp. 502 and 504). The connec- tions of the bladder moderately full are the following : — The summit or apex is rounded, and from its anterior part three liga- mentous cords are prolonged to the umbilicus ; the central one of these is the remains of tlie urachus; and the two lateral are formed by the oblite- rated hypogastric arteries. If the bladder is distended the apex is above, but otherwise below the pubes. All the surface behind the obliterated vessels is covered by peritoneum. Tlie base (fundus) is large, and rests on the middle piece of the rectum : in the state of emptiness of the bladder the base is scarcely prominent, but in distension of the viscus, it extends lower, and becomes widened. Connected with the fundus are the vesiculae seminales and the vasa defe- rentia; and between these is a triangular space, from which the perito- neum is partly absent. Surfaces of the body. The front of the body is in contact with the posterior surface of the symphysis pubis, and with the abdominal wall if it is distended, and is altogether free from peritoneum ; whilst the posterior surface is entirely covered by the serous membrane, and is touched often by the small intestine. Extending along the upper part of each lateral region is the obliterated hypogastric vessel ; and running down behind this is the vas deferens, which passes internal to the ureter. Near the under part the ureter enters the bladder. All the side of the bladder behind the hypogastric vessel is covered by peritoneum, but the rest is uncovered. Tlie neck (cervix) is the narrow anterior part of the bladder that joins the urethra : in the state of contraction it is the lowest part of the viscus, but in distension it is above the level of the fundus. It is surrounded by the prostate gland. CONNECTIONS OF BLADDER. 507 The ureter (fig. 174, li) crosses the common or the external iliac artery, and forms an arch below the level of the obliterated hypogastric vessel ; it enters the bladder near the lower part, and somewhat on the side, at the distance of one inch and a half or two inches from the prostate gland. The PROSTATE GLAND (fig. 174, h) SLirrouiids the neck of the bladder. It is placed about an inch below the level of the symphysis pubis, and is supported by the rectum. Its shape is conical with the base turned back- wards, and its size equals nearly that of a large chestnut. In the present position of the ])elvis, a line from the apex through the middle of the gland would be directed obliquely downwards and backwards towards the end of the sacrum ; but in the erect state of the body, upwards and backwards from the triangular ligament. The upper surface is about an inch below the symphysis pubis, and is connected to it by the anterior true ligaments of the bladder. On this surface are branches of the dorsal vein of the penis. The under surface has the greatest extent, and is contiguous to the rectum ; this is the part that is felt by the finger introduced into the bowel through the anus. The apex touches the posterior layer of the triangular ligament ; and the base surrounds the neck of the bladder, and the vesiculie seminales with the vasa deferentia. The prostate is enveloped by a sheath obtained from the recto-vesical fascia (p. 502), and a plexus of veins (prostatic) surrounds it. Through the gland the urethra takes its course to the penis ; and the ejaculatory ducts pierce it obliquely to open into the urethra (fig. 180,/). The size of the prostate alters much, and in old men it may acquire a considerable magnitude. The VESicuL.E SEMINALES (fig. 174, g) are two small sacculated bodies, each about two inches long, between the under part of the bladder and the rectum. Each is pyramidal in form, and has the larger end turned backwards towards the ureter, whilst the smaller is surrounded by the prostate. Along the inner side is the vas deferens. At the prostate gland the vesiculae approach one another, only the vasa deferentia intervening ; but further backwards they diverge, and inclose with the pouch of the peritoneum the triangular space at the under aspect of the bladder. The vesiculae are contained in a membranous sheath, which is derived from the recto-vesical fascia, and is lined by involuntary muscular fibres. The VAS DEFERENS Or the excretory duct of the testis (fig. 174,/) in its course to the urethra enters the abdomen by the internal abdominal ring; and crossing tiie obliterated hypogastric artery, is directed inwards along tlie side and under part of the bladder to the base of the prostate, where it forms the common ejaculatory duct by joining with the duct from the vesicula seminalis. TJie position of this tube to the external iliac artery has been noticed ; on the bladder it passes internal to the ureter and the vesicula of the same side. By the side of the vesicula the duct is much enlarged, and is sacculated. The URETHRA is the excretory passage for the urine and semen (fig. 174), and reaches from the bladder to tlie end of the penis. In length it measures about eight inches, and it presents one or two curves according to the state of the penis. At first the canal is directed forwards through the triangular ligament of the perinoeum to the body of the penis, forming a large curve with the concavity to the pubes. Thence to its termination the urethra is applied to the penis ; and whilst this body remains pendent 508 DISSECTION OF THE PELVIS. the canal forms a second bend with the concavity downwards, but if t1 e penis is raised the tube makes but one curve. The canal is divided into three parts — prostatic, membranous, and spongy. The prostatic part (h) is contained in the prostate gland, and receives its name from that circumstance. Its length is about one inch and a quarter, and in the erect posture it is inclined downwards to the triangular perinasal ligament. Its connections are the same as those of the gland (p. 507). The membranous part (c), about three-quarters of an inch long, inter- venes between the apex of the prostate and the front of the perinaeal trian- gular ligament. It slants downwards in the erect posture to the lore part of the triangular ligament ; and as the bulb of the next portion of tlie urethral tube is directed backwards below it, the under part measures only half an inch. This division of the urethra is the weakest : but it is supported by the triangular ligament {n). Surrounding it are the muscular fibres of the constrictor urethrae ; and close below it are Cowper’s glands with the rectum. The spongy part (d) is so named from its being surrounded by a cellu- lar and vascular structure. It is applied to and assists to form tlie body of the penis, and terminates anteriorly in tlie orifice named meatus uri- narius in the end of the glands. It is the longest part of the urethra, and measures about six inches. At its commencement this division of the excretory canal is covered for two indies by the ejaculator urinse muscle (tig. 130). The curve of the urethra is the fixed bend at tlie inner extremity, which lies below the pubes. It extends from the bladder to an inch and a half in front of the triangular ligament, and consists of the prostatic and mem- branous portions, with a fourth of the spongy part. Its covexity, which is turned downwards, is greatest at the fore part of the triangular ligament in the erect posture : and from this point it curves up and back to the bladder, and up anteriorly to the penis. It is surrounded by voluntary and involuntary muscular fibres : thus, behind the ligament, by the involuntary muscular tissue of the prostate ; within the ligament by the voluntary constrictor urethra, with a thin in- voluntary layer inside that muscle ; and before the ligament by the volun- tary ejaculator urina?. Its size is smallest where the tube pierces the perinaeal ligament ( 71 ), and lies between the layers ; and is largest in the middle of the prostatic part. Dissection. The tegumentary covering of the penis may be removed, to see the component parts of that body ; and after its removal the spongy ])art of the urethra will be better seen: the teguments should be replaced after the part has been learnt. The PENIS is attached to the fore part of the pelvis, and hangs in front of the scrotum. It is constructed of two firm fibrous bodies (fig. 174, e) named corpora cavernosa, wdiicli are filled with a plexus of vessels, and make up tlie principal ])art. Below these is a soft spongy substance (corpus spongiosum) which surrounds the urethra, and forms the head or the glans penis. The tegumentary investment, which covers the whole, is noticed at p. 407. The body of the penis is grooved above and below along the middle line, and is covered anteriorly by the glans penis; along its under surface VISCERA IN THE FEMALE. 509 the urethra is conducted. Besides the attachment of the corpora cavernosa to the bone, the body of the penis is connected vvitli the front of the symphysis pubis by the suspensory ligament. The corpus spongiosum urethrcc incloses the urethral canal in front of the triangular ligament, and forms the head of the penis. It is a vascular and erectile texture, like the corpora cavernosa, but is much less strong. Commencing posteriorly by a dilated part — the bulb, it extends forwards around the urethra to the extremity of the penis, where it swells into the conical glans penis. The hulh (fig. 174, d) is directed backwards, slightly, below the mem- branous part of the urethra, and is fixed by fibrous tissue to the front of the triangular ligament. The ejaculator urin^e muscles cover it. This enlargement presents usually a central depression, with a bulging on each side, and is subdivided into two lobes. The glans penis (fig. 181, /) is somewhat conical in form, and covers the truncated end of tlie corpora cavernosa. Its base is directed back- wards, and is marked by a slightly prominent border — the corona glandis; it is sloped obliquely along the under aspect, from the apex to the base. In the apex is a vertical slit, in which the urethral canal terminates; and below that aperture is an excavation, which contains the piece of the teguments named f rcenum preputii. Section III. CONNECTIONS OF THE VISCERA IN THE FEMALE. In the pelvis of the female are contained the lower end of the intestinal tube, and the bladder and urethra, as in the male ; but there are in addition the uterus with its accessories, and the vagina. Position. The rectum is posterior to tlie rest as in the male pelvis, and forms a like curve. In the concavity of the bent intestine lie tlie uterus with its appendages, and the tube of the vagina. And in front of all are the bladder and the urethral canal. Thus there are three tubes connected with the viscera in this sex, viz., the urethra, the vagina, and the rectum; and all are directed forwards, one above another, to the surface. Directions. The description in Section I. (p. 499) must be used for instructions respecting the removal of the innominate bone, and the dis- tension of the viscera ; also for the muscles of the pelvic outlet and the anatomy of the fasciae. After the student has learnt the muscles and tlie fascia, p. 499, which are nearly alike in both seves, he may make the following special dissection of the viscera of the female pelvis. Dissection. On taking away the recto-vesical fascia and much fat, the viscera will come into view. To maintain the position of the uterus, raise it up with a piece of string passed through the upper [lart. The reflec- tions of the peritoneum on the viscera are to be preserved ; and a piece of cotton wool is to be placed between the rectum and the uterus. The obliterated cord of the internal iliac artery is to be followed on the bladder ; and the ureter is to be traced forwards by the side of the uterus to the bladder. Afterwards the urethra, the vagina, and the rectum are 510 DISSECTION OF THE PELVIS. to be cleaned and partly separated from one another at the anterior part of tlie pelvis ; but the arteries on the rectum are to be preserved. The 'peritoneum gives a partial covering to the viscera, as in the male pelvis. Investing the upper part of the rectum, and forming behind it the meso-rectum, the membrane is continued to the posterior part of the vagina, and the back of the uterus. It covers the posterior, and the greater part of the anterior surface of the uterus, and can be traced to the bladder without again touching the vagina : on each side of the uterus it forms a wide fold (broad ligament), which attaches that viscus to the wall of the abdomen. As the peritoneum is followed upwards it may be observed to cover the posterior surface of the bladder, and the lateral part behind the position of the obliterated hypogastric artery. In the pelvis the serous membrane forms the following ligaments for the uterus and bladder. The broad ligament of the uterus (fig. 175) passes from the side of the uterus to the wall of the abdomen, and supports that organ. By its posi- tion across the pelvis, it divides the cavity into an anterior and a posterior portion : in the former are placed the bladder, urethra, and vagina ; in the latter the upper part of the rectum, and the small intestine when it reaches the pelvis. Each ligament shows traces of a subdivision into three pieces, corre- sponding with the bodies contained between its two layers. Thus there is a posterior piece belonging to the ovary and its ligament, l ; an anterior, near the upper part, which is appropriated to the round ligament, n ; and a middle piece, the highest of all, surrounds the Fallopian tube, m. Anterior and posterior ligaments of the uterus. As the peritoneum is reflected from the rectum to the uterus, and from the uterus to the bladder, it forms two anterior and to posterior folds or ligaments. The anterior or vesico-uterine pair is smaller than the posterior or recto-uterine. The recto -uterine pouch corresponds with the recto-vesical in the male. On each side it is bounded by the obliterated hypogastric artery : and be- low, it reaches beyond the uterus, so as to touch the back of the vagina. The false ligaments of the bladder are the same as in the male, and are fiv'C in number, viz., two posterior, two lateral, and a superior : they are all blended in one large piece of peritoneum that reaches from the bladder to the side and front of the pelvis. In the female the posterior ligament, containing the vessels of the bladder, is less marked than in the male. The RECTUM (fig. 175, ^) is not so curved in the female as in the male, and is generally larger. Descending along the middle of the sacrum and coccyx to the anus, tlie intestine is divided into tliree parts : — ThQ first part ends over the third piece of tlie sacrum, and is enveloped by the peritoneum, except posteriorly: its connections are similar to those of the rectum in the male, p. 504. The middle part reaches to the tip of the coccyx, and has the vagina above and in contact with it. The peritoneum extends on the front fey' a short distance. The lower part curves to the anus away from the vagina so as to leave between tlie two a space, which corresponds, on the surface of the body, with the part of the perimeum between the anus and the vulva. The levatores ani are on tlie sides, and unite below it, and the sphincter mus- cles surround the extremity. The UTERUS (fig. 175, ®) is somewhat conical in shape, and flattened from before backwards. Unless enlarged, it lies below the brim of the CONNECTIONS OF UTEKUS. 511 pelvis, between the bladder and the rectum ; and it is retained in place by the ligaments. Its wider end is free and placed upwards, and the lower end communicates with the vagina. This viscus is directed forwards, so that its position is oblique in the cavity of the pelvis ; and a line through its centre would correspond with the axis of the inlet of the pelvic cavity. Fig. 175. Side View of the Female Pelvis. (Illustrations of Dissections.) Muscles and Viscera : A. Pyriformis muscle, cut. B. Large psoas, cut. c. Gluteus maximus, cut. D. Coccygeus, and e, Levator ani, thrown down. F. Sphincter vaginae. G. Urethra. H. Urinary bladder. I. Vagina. K. Rectum. L. Ovary and its ligament. M. Fallopian tube. N. Round ligament. O . Uterus. Arteries : а. External iliac. б. Internal iliac. c. Middle sacral. d. Uterine. «. Vaginal. /. Upper hajmorrhoidal. g. Gluteal, cut. h. Obliterated hypogastric. i. Inferior vesical. The anterior flattened surface is covered by peritoneum, except in the lower fourth where it is in contact with the bladder. The posterior sur- face, rounded, is invested altogether by the serous membrane. The upper end (fundus) is the largest part of the organ, and is in con- tact with the small intestine. The lower end, or the neck (cervix) is received into the vagina. To each side are attached the broad ligament with the Fallopian tube, the round ligament, and the ovary. The Fallopian tube, m, four inches long, is contained in the upper or free border of the ligament. One end is connected to the upper angle of 512 DISSECTION OF THE PELVIS. the uterus, whilst the other is loose in the cavity of the pelvis. At the uterine end the tube is of small size, but at the opposite extremity it is dilated like a trumpet, and fringed, forming the corpus Jimhriatam. The round or suspensory ligament^ n, is a fibrous cord about five inches long, which is directed outwards through the internal abdominal ring and the inguinal canal to end in the groin. This cord lies over the obliterated hypogastric, and the external iliac artery ; and it is surrounded by the peritoneum, which accompanies it a short way into the canal. The ovary ^ l, is placed nearly horizontally, and bulges at the posterior aspect of the broad ligament ; it is connected to the uterus at the inner end by a special fibrous band, one inch and a half in length, the ligament of the ovary. Its form is oval, and its margins are turned forwards and backwards. Its size is very variable. The VAGINA (fig. 175, is the tube by which the uterus communicates with the exterior of the body. It is somewhat cylindrical in shape, tliough flattened from above down ; and its length is about five inches. As it follows the bend of the rectum it is slightly curved ; and its axis corre- sponds at first with the centre of the outlet, but higher up with that of the cavity of the pelvis. Above the vagina are the base of the bladder, and the urethra ; and beneath or below it is the rectum. To each side is attached the recto- vesical tascia, which sends a sheath along the lower half of the tube. The upper end receives the neck of the uterus by an aperture in the an- terior or upper wall ; and the lower end, the narrowest part of the canal, is encircled by the sphincter vaginse muscle. A large plexus of veins surrounds the vagina. In children, and in the virgin, the external aperture is partly closed by the hymen. The BLADDER (fig. 175, is placed at the anterior part of the pelvis, above the vagina and in contact with the back of the pubes. Its position and connections so closely resemble those of the bladder in the male body, as to render unnecessary any further description of them (p. 50G). The chief differences in the bladder of the two sexes are the following. In the female the bladder is larger than in the male, and its transverse exceeds its vertical measurement. The base is of less extent, and is in contact with the vagina and the low(;r part of the uterus ; and it does not reach below the orifice of the urethra. On the side of the viscus there is not any vas deferens ; and the prostate does not project around the neck. The ureter has a longer course in the female than in the male pelvis before it reaches the bladder. After crossing the internal iliac vessels, it passes by the neck of the uterus ere it arrives at its destination. The urethra (fig. 175, is a small narrow tube about one inch and a half long, vdiich curves slightly below the symphysis pubis, the concavity being upwards. Its situation is above the vagina, and its external open- ing is placed within the vulva. In its course to the surface it is embedded in the tissue of the vaginal wall, and perforates the triangular ligament of the perinmum. It is sur- rounded by the muscular fibres of the constrictor and orbicularis urethrai ([). 398) ; and correspoiuls with the two hinder parts (prostatic and mem- branous) of the male urethra. A plexus of veins surrounds the urethra as well as the vagina. VESSELS AND NERVES OF THE PELVIS. 518 Section IV. VESSELS AND NERVES OF THE PELVIS. In the pelvis are contained the internal iliac vessels, and their branches to the viscera ; the sacral plexus and its nerves ; and the sympathetic nerve. This Section is to be used by the dissectors ot‘ botli the male and female pelvis. Directions, The internal iliac vessels are to be dissected on the right side. But the air should be previously let out of the bladder ; and this viscus and the rectum, with the uterus and the vagina in the female, should be drawn aside from their situation in the centre of the pelvis. Dissection, The loose tissue and fat are to be removed from the trunks of the vessels, as well as from the branches of the artery that leave the pelvis, or supply the viscera ; and the obliterated cord of the hypogastric artery is to be traced on the bladder to the umbilicus. With the vessels are offsets of the hypogastric plexus of nerves, but these will probably not be seen ; but in dissecting the vessels to tlie bladder and rectum, branches of the sacral spinal nerves will come into view. The veins may be removed in a general dissection, to make clean the arteries. When the vessels are prepared the bladder may be again distended, and the viscera replaced. The INTERNAL ILIAC ARTERY (fig. 176, g) is One of, the trunks result- ing from the division of the common iliac artery, and furnishes branches to the viscera and wall of the pelvis, to the generative and genital organs, and to the limb. In the adult the vessel is a short trunk of large capacity, which meas- ures about an inch and a half in length. Directed downwards as far as the sacro-sciatic notch, the artery terminates generally in two large pieces, from which the several offsets are furnished. From the extremity a partly obliterated vessel (hypogastric) extends forwards to the bladder. In entering the pelvis the artery lies in front of the lumbo-sacral nerve. It is accompanied by the internal iliac vein, which is posterior to it, and somewhat to the outer part on the right side. The branches of the artery are numerous, and arise usually in the fol- lowing manner: From the posterior piece of the trunk three arise, viz., the ilio-lumbar, lateral sacral, and gluteal. And from the anterior portion come the vesical (upper and lower), haemorrhoidal, obturator, sciatic, and pudic : in the female there are in addition the uterine and vaginal bi*anches. Artery in the foetus. In the foetus the hypogastric artery takes the place of the internal iliac, and leaves the abdomen by the umbilicus. At that time it is larger than the external iliac artery ; and, entering but slightly into the cavity of the pelvis, it is directed forwards to the back of the bladder, and along the side of that viscus to the apex. Beyond the bladder the artery ascends along the posterior aspect of the abdominal wall with the urachus, converging to its fellow. Finally at the umbilicus the vessels of opposite sides come in contact with the um- bilical vein, and passing from the abdomen through the aperture at that spot, enter into the placental cord, and receive the name umbilical. In the foetus, branches similar to those in the adult are furnished by the artery, though their relative size at the two periods is very different. 33 514 DISSECTION OF THE PELVIS. Change to adult state. AYhen uterine life has ceased the hypogastric artery diminishes in consequence of the arrest of the current of blood through it, and finally becomes obliterated, more or less completely, as far back as an inch and a half of its commencement. The part ol the trunk which is unobliterated becomes the internal iliac ; and commonly a portion of the vessel remains pervious as far as the upper part of the blad- der, and gives origin to the vesical arteries. Peculiarities. The length of the internal iliac arteries varies from half an inch to three inches, its extreme measurements ; but in two-thirds of a certain number of bodies (Quain) it ranged from an inch to an inch and a half. Size. When the femoral trunk is derived from the internal iliac, and is placed at the back of the thigh, the parent vessel is larger than the external iliac. Fig. 176. Dissection of the Inteknai. Iliac Artery (Tiedemaiin). A. Bladder. o. Vas deferens, H. Vesicula seminalis. B. Lower end of the rectum, c. Levator ani. D. Psoas magnus. K. Psoas parvus. F. Iliacus. Arteries : a. Aorta splitting into the common iliacs. b. Middle sacral branch. c. Common iliac. ) ascends at the anterior border of the internal lateral ligament, and after taking its share in the free anastomoses over the joint, ends in offsets for the articulation and the head of the tibia. e. The azygos branch enters the back of the joint through the posterior ligament, and is distributed to the ligamentous structures, the fat, and the synovial membrane of the interior. 596 DISSECTION OF THE THIGH. The POPLITEAL VEIN (fig. 203, h) originates in the union of the venas comites of the anterior and posterior tibial vessels, and has the same ex- tent and connections as the artery it accompanies. At the lower border of the popliteus muscle the vein is internal to the arterial trunk ; between the heads of the gastrocnemius it is superficial to that vessel ; and thence to the opening in the adductor magnus it lies to the outer side, and close to the artery. It is joined by branches corresponding with those of the artery, as well as by the short saphenous vein (fig. 203). The POPLITEAL NERVES (fig. 202) are the two large trunks derived from tlie division of the great sciatic in the thigh ; they are named inter- nal and external from their relative position. In the popliteal space each furnishes cutaneous and articular offsets, but only the inner one supplies branches to muscles. The INTERNAL POLITE AL NERVE (^) is larger than the external, and occupies the middle of the ham : its connections are similar to those of the artery, that is to say, it is partly superficial and partly covered by the gas- trocnemius. Like the vessel it extends through the back of the leg, and retains the name popliteal only to the lower border of the popliteus mus- cle. Its position to the vessels has been already noticed. The branches arising from it here are the following : — a. Two small articular twigs (fig. 203, are furnished to the knee joint with the vessels. One which accompanies the lower internal articu- lar artery to the fore part of the articulation is the Ij^’gest ; and another takes the same course as the azygos artery, and enters the back of the joint with it. h. Muscular branches arise from the nerve between the heads of the gastrocnemius. One supplies both heads of the gastrocnemius and the ])lantaris. Another descends beneath the gastrocnemius, and enters the cutaneous surface of the soleus. And a third penetrates the popliteus at the under aspect, after turning round the lower border. c. The external saphenous WQYYQ, (fig. 207,®) (ram. communicans tibialis) is the largest branch, and is a cutaneous offset to the leg and foot. It lies on the surface of the gastrocnemius, but beneath the fascia, as far as the middle of the leg, where it becomes cutaneous, and will be afterwards seen. The EXTERNAL POPLITEAL NERVE (fig. 202, ®) (pei’oneal) lies along the outer boundary of the ham as far as the knee joint; at that level it leaves the space and follows the edge of the biceps muscle for two inches, till it is below the head of the fibula. There it enters the fibres of the peroneus longus, and divides beneath that muscle into three — musculo- cutaneous, anterior tibial, and recurrent articular. Its branches wliilst in the popliteal space are cutaneous and articular. a. The articular nerve, arising high in the space, runs with the upper external artery to the outer side of the knee, where it sends a twig along the lower articular artery : both enter the joint. h. The peroneal corn muni eating branch (fig. 207, ^) (ram. communi- cans fibularis) joins the external saphenous branch of the internal popli- teal about the middle of the leg. It soon becomes cutaneous, and offsets are given by it to the back of tlie leg. c. One or two cutaneous nerves are furnished by the external popliteal to the integument on the outer side of the leg in the upper half. The articular branch of the obturator nerve (fig. 203, ^) perforates the adductor magnus, and is conducted by the popliteal artery to the back of HAMSTRING MUSCLES. 59T the knee joint. After supplying filaments to the vessels, the nerve enters the articulation through the posterior ligament. The lymphatic glands of the popliteal space are situate around the large arterial trunk. Two or three are ranged on tlie sides ; whilst one is superficial to, and another beneath the vessel : they are joined by the deep lymphatic vessels, and by the superficial set with the saphenous vein. THE BACK OF THE THIGH. Dissection (fig. 203). Now the popliteal s})ace has been examined, the student may proceed with the dissection of the back of the thigh. The piece of skin between the buttock and the popliteal space should be di- vided, and reflected to the sides. In the fat on the sides of the limb fine offsets of the internal and external cutaneous nerves of the front of the thigh may be found ; and along the middle line some filaments from the small sciatic nerve pierce the fascia. l^emove the deep fascia of the limb, taking care of the small sciatic nerve and its artery. Lastly, clean the hamstring muscles ; trace out tlie perforating arteries to the front of the thigli, and clean the branches of the great sciatic nerve and profunda artery to the muscles. Muscles. The muscles behind the femur act mainly as flexors of the knee joint. Tliey extend from the pelvis to the bones of the leg, and are named hamstrings from their cord-like appearance on the sides of the ham : they are three in number, viz., biceps, semitendinosus, and semimembra- nosus. The first of these lies on the outer, and the others on the inner side of the popliteal space. The BICEPS (fig. 203, has two heads of origin, long and short, which are attached to the pelvis and the femur. The long head arises from an impression on the back of the ischial tuberosity, in common with tlie semitendinosus muscle. The short head is fixed to the femur below the gluteus maximus, viz., to all the linea aspera, to nearly the whole of the line leading inferiorly to the outer condyle, and the external intermuscular septum. The fibres end inferiorly in a tendon, which is inserted into two prominences on the head of the fibula by slips which embrace the exter- nal lateral ligament ; and a slight piece is prolonged to the head of the tibia. The muscle is superficial, except at the origin, where it is covered by the gluteus : it rests on the upper part of the semimembranosus, and on the great sciatic nerve and the adductor magnus muscle. On the inner side is the semitendinosus as far as the ham. Its tendon gives offsets to the deep fascia of the limb. Action. It can bend the knee if the leg-bones are not fixed, and after- wards rotate out the tibia; and the long head, which passes upwards beyond the femur, will extend the bent hip joint when the knee is straight. The leg being supported on the ground, the long head will assist in balancing and erecting the pelvis ; and the short head will draw down the femur so as to bend the knee in stoo[)ing. The SEMITENDINOSUS (fig. 203, is a slender muscle and receives its name from appearance. It arises from the tuberosity of the hip bone with the long head of the biceps, and by fleshy fibres from the tendon of that muscle. Inferiorly it is inserted into the inner surface of the tibia, close below the gracilis, and for a similar extent. This muscle, like the biceps, is partly covered by the gluteus maximus. 598 DISSECTION OF THE THIGH. About its middle a tendinous intersection may be observed. It rests on the semimembranosus, and on tlie internal lateral ligament of the knee- joint. The outer border is in contact with the biceps as far as the popli- Fig. 203. Muscles : A. Gluteus maxiraus, cut below, and partly raised. B. Quadratus femoris. c. Adductor inagnus. D. Biceps. E. Semitendinosus. F. Semimembranosus. G. Outer, and H. Inner bead of the gastrocnemius. Arteries: а. Small sciatic, cut. б. Ending of internal circumflex to the hamstrings. c. First, d, second, and e, third perforating of profunda. /. Muscular branch of profunda. g. Popliteal trunk. h. Popliteal vein. i. Short saphenous vein. h. Upper external, and Z, upper internal articular artery. Nerves : I. Small sciatic. 2. Large sciatic. 3. Branch to hamstrings from large sciatic. 4. External popliteal ; and 5. Communicating peroneal, 7. Articular branch of obturator to knee. 8. Internal popliteal. 9. Articular branch to knee of the internal popliteal. 10. Short saphenous. Dissection of the Back op the Thigh (Illustrations of Dissections). teal space. As the tendon turns forwards to its insertion, an expansion is continued from it to the fascia of the leg; and it is attaclied, with the gracilis, below the level of the tubercle of the tibia, the two being separated from the tendon of tlie sartorius by a bursa (p. 567). Action. If the leg is movable the muscle bends the knee ; and con- tinuing to contract, rotates towards the tibia. Supposing the knee-joint straight but tlie hip-joint bent, the femur can be depressed, and the hip extended by the semitendinosus and the other hamstrings. Should the limbs be fixed on the ground, the muscle will assist in balancing the pelvis, or in erecting the trunk from a stooping posture. The SEMIMEMBRANOSUS luuscle (fig. 203, *’) is tendinous at both ends, and its name is given from the membraniform appearance of the upper BRANCHES OF PROFUNDA ARTERY. 599 tendon. The muscle is attached above to the highest impression on the back of the tuber ischii, above and external to the semitendinosus and biceps ; and it is inserted below into the hinder and inner part of the head of the tibia. The muscle is thick and fleshy inferiorly, where it bounds the popliteal space. On it lies the semitendinosus, which is lodged in a hollow in the upper tendon ; and beneath it is the adductor magnus. Along the outer border lie the great sciatic, and internal popliteal nerves. Between its tendon and the inner head of the gastrocnemius is a large bursa. The insertion of the muscle will be dissected with the knee-joint. Action. This hamstring is united with the preceding in its action, for it bends the knee and rotates in the tibia ; and with the knee straight it will limit flexion of the hip, or extend this joint after the femur has been carried forwards. When the foot rests on the ground, the semimembranosus acts altogether on the pelvis. The GREAT SCIATIC NERVE (fig. 203, lies on the adductor magnus muscle below the buttock, and divides it into the two popliteal nerves about the middle of the thigh, though its point of bifurcation may be car- ried upwards as far as the pelvis. In this extent the nerve lies along the outer border of the semimembranosus, and is crossed by the long head of the biceps. Branches. At the upper part of the thigh it supplies large branches to the flexor muscles, and a small one to the adductor magnus. Small sciatic nerve (fig. 203, ^). Between the gluteus maximus and the ham this small nerve is close beneath the fascia ; but it becomes cuta- neous below the knee, and accompanies the external saphenous vein for a short distance. Small cutaneous filaments pierce the fascia of the thigh ; and the largest of these arises near the popliteal space. Dissection. To see the posterior surface of the adductor magnus, and the branches of the perforating and muscular arteries, the hamstring muscles must be detached from the hip bone and thrown down ; and the branches of arteries and nerves they receive are to be dissected out with care. All the parts are to be cleaned. Adductor magnus muscle (fig. 203, ®). At its posterior aspect the large adductor is altogether fleshy, even at the opening for the femoral artery ; and the fibres from the pubic arch appear to form a part almost distinct from those connected with the tuberosity of the hip bone. In contact with this surface are the hamstring muscles and the great sciatic nerve. Ending of the 'perforating arteries (fig. 203, c, c?, e). These branches of the profunda appear through the adductor magnus close to the femur, and are directed out through the short head of the biceps and the outer intermuscular septum to the vasti muscles ; but as the first branch is placed higher than the attachment of the biceps, it pierces the gluteus maximus in its course. In the vasti they anastomose together, and with the descending branches of the external circumflex artery. IMuscular branches are furnished by the perforating arteries to the heads of the biceps ; and a cutaneous offset is given by each to the tegu- ments of the outer part of the thigh, along the line of the outer inter- muscular septum. 600 DISSECTION OF THE THIGH. Muscular hranches of the profunda (fig. 203, /) pierce the adductor magnus internal to the preceding, and at some distance from the femur. Three or four in number, the highest appears about five inches from the pelvis, and the rest in a line at intervals of about two inches from one another : they are distributed to the hamstring muscles, especially the semimembranosus, and communicate below with offsets of the popliteal trunk. The HIP-JOINT (fig. 204). This articulation is a ball and socket joint, the head of the femur being received into the acetabulum or the cup- shaped hollow of the innominate bone. Connecting the bones are the fol- lowing ligaments : — one to deepen the receiving cavity, which is named cotyloid ; another between the articular surfaces of the bones — the inter- articular ; and a capsule around all. Dissection. The muscles are to be taken away from the back of the hip-joint, and the upper and lower attachments of the capsular ligament are to be especially cleared from areolar tissue. Next, the front of the joint should be cleaned and examined in the same manner, with the body turned over for a short time, if this change in position does not interfere with the other dissec- tions. In the capsule itself the stu- dent has to define a wide thick part in front, and a transverse band near the neck of the femur behind. The capsular ligament (fig. 204) is a thick fibrous case, which is strong enough to check the movements of the joint. Its up- per margin is attached to the circLimfererence of the acetabu- lum at a short distance from the edge, as well as to a transverse ligamentous band over the notch at the inner side of the cavity. Its lower margin is inserted in front into the anterior intertro- chanteric line (fig. 204) ; behind, by a very thin piece, into the neck of the femur about a finger’s breadth from the small trochanter and the posterior intertrochan- teric line (fig. 205) ; and above, into the neck, near the great tro- chanter. The capsule differs much in strength, and in the arrangement of the fibres at the fore and hinder surlaces. On the front it is strengthened by a wide layer of longitudinal fibres (fig. 204, «, 5, c). The central portion — the ilio-femoral ligament («), is fixed above by a narrow piece to the lower anterior iliac spinous pro- cess, and below where it widens, into the anterior intertrochanteric line. By its strength it can arrest extension of the joint ; and the femur being Fig. 204. Fore part of the Capsule op the IIip-joint. a. Ilio-femoral ligament. h. Pubio-femoral edge or baud, c. Ilio-trocbauteric baud. LIGAMENTS OF HIP JOINT. 601 fixed, it will prop the pelvis. The outer edge (e) (ilio-trochanteric band) extends from the hip bone opposite the outer head of the rectus, to the upper and fore part of the great trochanter and neck of the femur; its use is to check adduction of the femur. The inner edge {h) (pubio-femoral band) is attached superiorly to the prominent pubic portion of the hip bone inside the acetabulum, and inferiorly to a roughened surface at the lower part of the neck of the femur on a level Avitli, and in front of, the small trochanter : this band controls the abductory movement of the joint. Fig. 205. а. Longitudinal fibres. c. Thin piece attached to the neck of the femur б, Transverse baud. about half way down. At the back of the capsule close to the neck of the femur is a band of transverse fibres (fig. 205, 5), about as Avide as the little finger, which arches like a collar over the neck of the bone. By its lower edge it is united to the cervix femoris by a thin layer (c) of fibrous tissue and syno- vial membrane ; at the upper edge it is joined by the longitudinal capsular fibres («). It gives insertion to the longitudinal fibres of the capsule, and ])re vents that restriction of the swinging movement which would result from their insertion into the hinder part of the neck. Posteriorly the joint is covered by the external rotator muscles ; and anteriorly by the psoas and iliacus, a bursa being between it and them. Above is the gluteus minimus, whose tendon is united with the upper and outer band of the capsule ; and below is the obturator externus. Dissection (fig. 20G). The capsular ligament is to be now divided over the prominence of the head of the femur, and this bone being disarticu- lated but not detached, the cotyloid and interarticular ligaments inside it will appear. The interarticular or round ligament is attached to the acetabulum by 602 DISSECTION OF THE THIGH. two pieces ; and to bring these into view, the synovial membrane and are- olar tissue must be removed. The transverse ligament over the notch is also to be defined. The cotyloid ligament (fig. 191, is a narrow band of fibro-cartilage, which is fixed to the margin of the acetabulum, and is prolonged across the notch on the inner side, so as to form part of the transverse ligament. Its fibres are not continued around the acetabulum, but are fixed to the margin of the cavity, and cross one another in the band. It is thickest at its attachment to the bone, and becomes gradually thinner towards the free margin, where it is applied to the head of the femur. This ligament fills up the hollows in the rim of the acetabulum, and deepens the socket for the femur in the same manner as the glenoid liga- ment increases the surface for the reception of the head of the humerus. The transverse ligament (fig. 191, is a firm but narrow band, wliich reaches across the upper part of the notch at the inner side of the aceta- bulum. It consists partly of deep special fibres {K) which are attached to the margins of the notch ; and partly of a superficial bundle from the cotyloid ligament (^). Beneath it is an aperture by which vessels and nerves enter the acetabulum to supply the synovial membrane, and the fat in the bottom of that hollow. The inter articular or round ligament (fig. 206, h) (ligam. teres) is a slight band about an inch long, connecting the femur with the innominate bone. One extremity is roundish, and is inserted into the pit in the head of the femur. The other is fiattened, and divides into two parts opposite the transverse ligament. The anterior piece (c) (pubic) is attached with the transverse ligament to the pubic edge of the notch. The posterior part (c?) (ischial) is inserted behind the transverse ligament into the ischial border of the cotyloid notch. Dissection. To see its condition in the different movements of the articu- lation, it should be examined in a joint in which the capsule is entire, and the bottom of the acetabulum has been cut out with a chisel inside the pelvis. When the joint is in the extended state, the ligament is generally lax, the two end attachments being near each other ; but if the femur is ad- ducted, the ischial part of the ligament is rendered tight because the head of the femur rises. In flexion of the joint the ligament is tighter than in extension, as the femoral insertion is removed from the acetabular ; and if, in the bent state, the femur be rotated out or adducted, the round ligament will be most stretched. A synovial membrane lines the capsular ligament, and is continued along it to tlie acetabulum and the head of the femur. In the bottom of the cotyloid cavity it is reflected over the fat in that situation ; and it sur- rounds the ligamentum teres. Dissection. To see the surface of the acetabulum the lower limb is to be separated from tlie trunk by dividing the interarticular ligament, and by cutting through any parts that connect it to the pelvis : at tliis stage the pelvic attachments of the round ligament can be better seen. Surfaces of hone. The articular surfaces of the bones are not completely covered with cartilage. MOVEMENTS OF HIP JOINT. 603 In the head of the femur is a pit into which the round ligament is in- serted. The acetabulum is coated with cartilage at its circumference, except opposite the notch, and touclies the head of the femur by this part : the articular surface is deep above, but gradually decreases towards the notch. Within the cartilage and close to the notch, is a mass of fat (fig. 191, f) covering about one third of the area of the cotyloid cavity, which constitutes tlie gland of Havers : it communicates with the fat of the thigh beneath the transverse ligament. Movement. In this ball and socket joint there are the same kinds of movement as in tlie shoulder, viz., flexion and exten- sion, abduction and adduction, circumduction, and rotation. Flexion and extension. In the swinging movement flexion is freer than extension, the thigh being capable of such elevation as to touch the belly. During swinging the head of the femur revolves in the bottom of the acetabulum, rotating around a line corresponding with the axis of the head and neck ; and the rapidity and extent of the move- ments do not endanger the secu- rity of the joint, tlie head of the bone not having any tendency to escape. In flexion, the back of the H.p Jo,kt Ope»kd, to show the iaterartlcular or capsule and the ilio-trochanteric band are put on the stretch ; and ^ LIgamentam teres: e. it, pubic, and, d, its in extension, the strong ilio and ischial attachment, pubio-femoral bands are tightened. In abduction and adduction the femur is removed from, or brought towards the middle line of the body. Of the two, abduction is the most extensive, because the limb may soon meet its fellow when it is moved inwards, though, if it is carried in front of the other, adduction is con- siderable. In both states the head moves in the opposite direction to the shaft. Thus, as the femur is abducted, the head descends, and the greater part of the articular surface projects below the acetabulum ; and when the limb is raised to its utmost the great trochanter comes to rest on the margin of the acetabulum, so as to limit farther motion. As the limb descends and approaches the other, the head rises into the socket of the joint, and is securely lodged, finally, in the deepest part of the cavity. In abduction, the inner band of the capsule is tightened over the pro- jecting head of the femur, the upper part being relaxed. And in adduc- tion, the outer band of the capsule is rendered tense enough to arrest the movement. 604 DISSECTION OF THE THIGH. Dislocation may take place in both these lateral movements, the edge of the cotyloid cavity serving as the fulcrum by which the femur can be lifted out of the hollow ; in the one case (adduction) the neck of the femur rests on the brim of the acetabulum, and in the other (abduction) the great trochanter is supported on the margin of the joint-socket. After a dislocation has been reduced, the state of adduction, with the knees fastened together, is the securest»position in which the limb can be placed, inasmuch as the head of the femur then occupies the deepest part of the acetabulum. In circumduction^ the four kinds of angular motion above noticed take place in succession, viz., flexion, abduction, extension, and adduction ; and the limb describes a cone, vdiose base is at its extremity, and apex at the union of the neck with the shaft of the femur. This movement is less free than in the shoulder-joint, because of the greater bend between the neck and shaft of the femur. There are two kinds of rotation^ internal and external : in the former, the great toe is turned in ; and in the latter, the more extensive of the two, it is moved outwards. In rotation inwards, the head of the femur rolls backwards horizontally across the acetabulum, the great trochanter being put forwards ; and the shaft of the bone revolves around a line inside it, which passes from the head to the inner condyle. During this movement the posterior half of the capsule is put on the stretch, and the anterior is relaxed. In rotation out the head of the bone rolls forwards across the cotyloid cavity, and the great trochanter is brought backwards, whilst the shaft of the femur moves round the line on its inner side before noticed. The fore part of the capsule is now put on the stretch, and the hinder is rendered loose. The movement of rotation is destroyed by fracture of the neck of the bone. Its degree is proportioned to the length of the neck, and is there- fore greater in the femur than in the humerus. Use of hend of femur. By means of the angle at the union of the neck with the shaft, the pelvis is more firmly })ropped than it would be if the neck was in a line with the rest of the femur. It permits also greater surface contact between the head of tlie femur and the hip bone, since the whole head can be lodged in the cotyloid cavity in progression ; and gives greater security to the joint in flexion and extension, for if the neck and shaft of the bone were in a line, only half of the articular surface could enter the socket of the innominate bone in walking, and running. The important movement of rotation is also due to this angle ; and greater space is obtained through it for the location of the adductor muscles on the inner side of the femur. Dissection. After the limb is removed, the attachments of all the muscles in the thigh are to be examined more minutely before the dissec- tion of the leg is undertaken. The muscles should not be removed from the femur, but about two inches of each should be left for after study. SURFACE MARKING OF LEG. 605 Section IV. THE BACK OF THE LEG. Directions. Before the dissection of the leg is begun, the student sliould make himself acquainted, as in the thigh, with the prominences of bone and muscle on the surface, and with the markings which lead to the posi- tion of the larger vessels. Prominences of bone. The bones of the leg can be traced beneath the skin from the knee to the ankle-joint. On the inner side is the tibia, which is subcutaneous in all its extent, and is limited in front and behind by a sharp ridge : above, it presents in front a prominent tubercle into which the ligament of the patella is inserted ; and below, it ends on the inner side of the ankle in the internal malleolar projection. On the outer side of the leg the lower half of the fibula may be felt with ease, but the upper half with more difficulty in consequence of the prorninence of the muscles of the calf. The head of this bone may be recognized below the knee ; and the lower end forms the eminence (malleolus) on the outer side of the ankle joint. On the side of the ankle joint are the prominent malleoli ; and when the joint is extended, the head of the astragalus can be felt below the tibia. Aluscles and vessels of the leg. On the back of the leg is the swell of the calf : this is formed by the superficial muscles, and from it descends the firm band of the tendo Achillis, by which those muscles are connected with the heel. Between the tendon and the edge of the tibia, but nearest the former, is placed the superficial part of the posterior tibial artery. In front between the tibia and fibula are the flexor muscles of the foot and the extensors of the toes, amongst which the anterior tibial artery lies deeply ; the position of the vessel will be indicated by a line from the centre of the ankle-joint to the inner side of the head of the fibula. Prominences of the foot. At the inner border of the foot, about an inch in front of the internal malleolus, is the prominent scaphoid bone pointing out the spot at which an am[)Utation (Chopart’s) is practised; whilst one inch and a half farther forwards is a slight depression marking the articu- lation between the internal cuneiform and the metatarsal bone of the great toe. About the centre of the outer border of the foot is the eminence of the tarsal end of the fifth metatarsal bone. A line over the dorsum of the foot, from the centre of the ankle joint to the interval between the inner two toes, will lie over the position of the main artery. Position. For the dissection of the back of the leg, the limb is to be placed on its front, with the foot over the side of the dissecting-table ; and the muscles of the calf are to be put on the stretch by fastening the foot. Dissection. For the removal of the skin, one cut may be made along the middle of the leg to the sole of the foot, where a transverse incision is to be carried over the heel. The two resulting flaps of skin may be raised, the outer one as far as the fibula, and the other as far as the inner margin of the tibia. In the fat the cutaneous nerves and vessels are to be followed. On the inner side, close to the tibia, is the internal saplienous vein with the nerve of the same name, together with twigs of the internal cutaneous near the 606 DISSECTION OF THE LEG. knee. In the centre of the leg lies the external saphenous vein, with the small sciatic nerve as its companion above, and the external saphenous nerve below the middle of the leg. On the outer side, in the upper third, cutaneous offsets of the external popliteal nerve will be met with. The superficial fascia, or the fatty layer of the back of the leg, is least thick over the tibia. Over the line of the superficial vessels it may be separated into two layers. ' Superficial Veins. Two veins appear of the dissection of the back of the leg, which are named saphenous — inner and outer. The internal saphenous vein (fig. 208, d) begins in an arch on the dorsum of the foot. Ascending along the leg in front of the inner ankle, and then behind the inner edge of the tibia, it reaches the thigh (p. 555). In the leg tlie vein is joined by superficial branches, and by deep roots from the tibial veins. The external saphenous vein (fig. 207, c) begins at the outer end of the arch on the dorsum of the foot, and appears below the outer ankle. The vein then courses along the back of the leg to the ham, where it ends in the popliteal vein. It receives large branches about the heel, and others on the back of the leg, communicating with the internal saphenous. Cutaneous arteries accompany the superficial veins and nerves of the leg. Cutaneous Nerves (fig. 207). The nerves in the fat of the back of the leg are prolongations of branches already examined in part, viz. the ' internal and external saphenous, external popliteal, small sciatic, and in- ternal cutaneous of the thigh. Tlie internal saphenous nerve (fig. 207, ^) accompanies the vein of the same name beyond the knee (p. 573), and terminates at the middle of tlie inner border of the foot. In the leg the nerve gives off lateral cutaneous offsets, and the outer of these turn over the tibia to the anterior aspect. The external saphenous nerve (207,^) is a branch of the internal pop- liteal. Perforating the deep fascia about the middle of the leg, it is con- tinued with the external saphenous vein below the outer ankle, and is distributed to the outer side of the foot and little toe. As soon as the nerve enters the fat it is joined by the communicating branch of the ex- ternal popliteal ; and near the heel it gives large and long branches to the integuments. Cutaneous nerves of the external popliteal. One branch of the external popliteal trunk, viz., communicating peroneal (fig. 207,*), joins the external saphenous nerve about the middle of the leg ; but not uncommonly this branch extends as a distinct nerve as far as the heel. One or two other small cutaneous offsets of the external popliteal terminate over tlie fore part and outer side of the leg in the upper lialf. The small sciatic nerve (fig. 207,®) perforates the fascia near the pop- liteal space, and reaches to about the middle of the leg with the external saphenous vein : it ramifies in the integuments, and joins the external saphenous nerve. Offset of the internal cutaneous (fig. 207, ®). The inner branch of the internal cutaneous of the thigh (p. 55G) extends to the middle of the leg, and communicates with the internal saphenous nerve. Dissection. The deep fascia will be seen by removing the fat. The superficial vessels and nerves may be either cut or turned aside. The special or deep fascia on the posterior aspect of the leg covers the muscles, and sends a thick process between the deep and superficial layers. CUTANEOUvS VEINS AND NERVES 607 Fig. 207. First View of the Back of the Leo (Illus- trations of Dissections) . Muscles : A. Gastrocnemius. B. Soleus. c. Semimembranosus. D. Biceps. Vessels : а. Popliteal artery. h. Inner saphenous vein, c. External saphenous vein. Nerves : 1. External, and 2, internal popliteal. .3. Short saphenous. 4. Communicating peroneal. б. Common trunk of short saphenous. 6. Small sciatic. 7. Internal saphenous. 8. Internal cutaneous (inner) piece. Fig. 208. Second View of the Back op the Leg (Illus- trations of Dissections). Muscles : A. Gastrocnemius, cut. B. Soleus. c. Plantaris. D. Semimembranosus. E. Semitendinosus: F. Tendo Achillis. Vessels : а. Popliteal artery. б. Inner lower articular. c. External lower articular. d. Internal saphenous vein, c. External saphenous vein. Nerves : 1. External popliteal. 2. Internal popliteal. .3. Short saphenous, cut. 4. Cutaneous plantar branch. 608 DISSECTION OF THE LEG. Above, it is continuous with the investing membrane of the thigh, and receives offsets from the tendons about the knee ; and below, it joins the two annular ligaments. Externally it is continued uninterruptedly from the one aspect of the limb to the other, but internally it is fixed to the edge of the tibia. Veins are transmitted tlirough it from the deep to tlie superficial vessels. Dissection. The fascia is to be divided along the centre of the leg as far as the heel, and is to be taken from the surface of the gastrocnemius muscle. By fixing with a stitch the inner cut head of the gastrocnemius, the fibres of the muscle will be more easily cleaned. Superficial Layer of Muscles. In the calf of the leg there are three muscles, gastrocnemius, soleus, and plantaris, which extend the ankle. The two first are large, giving rise to the prominence on the sur- face, and end below by a common tendon ; but the last, inconsiderable in size, is chiefly tendinous. The GASTROCNEMIUS (fig. 207, ^), the most superficial muscle, is ten- dinous along the middle, and has above two distinct pieces or heads, which connect it with the condyles of the femur. The inner head of origin is attached by a large tendon to an impression at the posterior aspect of the inner condyle, behind the insertion of the adductor magnus, and by fleshy fibres to the line above the condyle. The outer head is fixed by tendon to a pit on the outer surface of the corresponding condyle, above the attachment of the popliteus muscle, and to the upper and back part of the same condyle. The fleshy fibres of the heads are united along the middle line by a narrow thin aponeurosis, and terminate inferiorly with the soleus in the common tendon of insertion. One surface is covered by the fascia. The other is in contact with the soleus and plantaris, and with the popliteal vessels and the internal popli- teal nerve. The heads, by which the muscle arises, assist to form the lateral boundaries of the popliteal space : and the fleshy inner head descends lower than the outer. In the outer head a piece of fibro-carti- lage or a sesamoid bone may exist. Action. When the foot is unsupported, the gastrocnemius extends the ankle ; and when the toes rest on the ground, it raises the os calcis and the weight of the body, as in standing on the toes, and in progression. Taking its fixed point at the os calcis, the muscle draws down the femur so as to bend the knee joint. Dissection. To see the soleus, the gastrocnemius is to be reflected by cutting across the remaining head, and the vessels and nerves it receives. After the muscle has been thrown down, the soleus and plantaris must be cleaned. The SOLEUS (fig. 208, is a large flat muscle, which is attached to both bones of the leg. It arises from the head, and the upper third or half of the posterior surface of the shaft of the fibula ; from the oblicpie line across the tibia, and from the posterior edge of this bone in the middle third ; and between the bones from an aponeurotic arch over the large bloodvessels. Its fibres are directed downwards to the common tendon. The superficial part of the soleus is in contact with the gastrocnemius ; and the opposed surfaces of the two are aponeurotic. Beneath the soleus lie the bones of the leg, the deep layer of muscles, and the vessels and nerves. SUPERFICIAL EXTENSORS OF ANKLE. 609 Tendo Achillis (fig. 208, ^). The common tendon of the gastro- cnemius and soleus is one of the strongest in the body. About three inches wide above, it commences at the middle of the leg, though it re- ceives fleshy fibres on the under surface nearly to the lower end : below it is narrowed, and is inserted into the lower half of the tuber calcis at the posterior aspect. A bursa intervenes between it and the upper part of the tuberosity. The tendon is close beneath the fascia ; and lying along its outer side, but superficial to it^ are the external saphenous vein and nerve. Action. In its action on the foot the soleus, like the gastrocnemius, extends the ankle and points the toes when the foot is free to move, and raises the heel if the toes rest on the ground. By the sudden and power- ful contraction of the fibres of both muscles, the common tendon is sometimes broken across. If it acts from the os calcis, it will draw back the bones of the leg into a vertical position over the foot, as the body is raised to the erect posture after stooping. The PLANTARis (fig. 208, is remarkable in having the longest tendon in the body, which takes the appearance of a ribbon when it is stretched laterally. About three-quarters of an inch wide, the muscle arises from the line above the outer condyle of the femur, and from the posterior ligament of the knee-joint ; and the tendon is inserted into the os calcis with or by the side of the tendo Achillis, or into the fascia of the leg. The belly of the muscle, about three inches in length, is concealed by the gastrocnemius, but the tendon appears on the inner side of the tendo Achillis about the middle of the leg. This little muscle crosses the pop- liteal vessels, and lies on the soleus. Action. It assists the gastrocnemius to extend the ankle if the foot is not fixed ; and to bend the knee-joint if the foot is immovable. Dissection (fig. 209). The soleus is to be detached from the bones of the leg, and the muscles and nerves entering it are to be divided ; but in raising it, the student should take care not to injure the thin deep fascia and the vessels and nerves beneath. The superficial muscles may be next removed by cutting through their tendons near the os calcis ; and the bursa between the tendo Achillis and the os calcis should be opened. The piece of fascia between the muscles of the superficial and deep layers is next to be cleaned ; and the integuments between the inner ankle and the heel are to be taken away to lay bare the annular ligament, but a cutaneous nerve to the sole of the foot, which pierces the ligament, is to be preserved. Deep part of the fascia. This intermuscular piece of the fascia of the leg is fixed to the tibia and fibula, and binds down fhe deep layer of flexor muscles. Beneath the soleus it is thin and indistinct ; but lower in the limb it is much stronger, and is marked by some transverse fibres near the malleoli, which gives it the appearance and office of an annular ligament in that situation. Inferiorly it joins the internal annular ligament between the heel and the inner ankle. Dissection. The deep layer of muscles (in part), the posterior tibial nerve, and the trunk and offsets of the posterior tibial vessels, will be laid bare by the removal of the fascia and the areolar tissue. A muscle be- tween the bones (tibialis posticus) is partly concealed by an aponeurosis which gives origin to the two muscles (flexor communis and flexor pollicis) 39 610 DISSECTION OF THE LEG. on the sides ; and it will not fully appear until after the membrane cover- ing it has been divided longitudinally, and reflected to the sides. To prepare the peroneal artery, evert and partly divide the flexor pollicis in which it is contained ; then follow branches of it to the fore part of the leg, the outer side of the foot, and to join the posterior tibial artery. Deep Layer of Muscles (fig. 209). The deep muscles at the back of the leg are four in number, viz., popliteus, flexor longus pollicis, flexor longus digitorinn, and tibialis posticus. The first of these is close to the knee-joint ; it crosses the bones, and is covered by a special aponeurosis The flexors lie on the bones, the one of the great toe resting on the fihula, and that of the other toes on the tibia. And the tibialis covers the inter- osseous membrane. With the exception of the popliteus, all enter the sole of the foot, and have a fleshy part parallel to the bones of the leg, and a tendinous part beneath the tarsus. The POPLITEUS (fig. 209 arises by tendon, within the capsule of the knee-joint, from the fore part of an oblong depression on the outer surface of the external condyle of the femur ; and external to the capsule of the joint, some fleshy fibres arise from the posterior ligament. The tendon gives rise to fibres, which are inserted into the tibia above the oblique line on the posterior surface. The muscle rests on the tibia, and is covered by a fascia derived in great part from the tendon of the semimembranosus muscle : on it lie the pop- liteal vessels and nerve, and the gastrocnemius and plantaris. Along the upper border are the lower articular vessels and nerve of the inner side of the knee ; and the lower border corresponds with the attachment of the soleus on the tibia. The origin will be seen with the dissection of the ligaments of the knee-joint. Action. The leg being free, the- muscle bends the knee-joint, and then rotates inwards the tibia. The foot resting on the ground, it will support the knee. According to the view of Theile, it retracts the external semi- lunar fibro-cartilage. The FLEXOR LONGUS POLLICIS (fig. 209, ariscs below the soleus from the lower half or two thirds of the posterior surface of the fibula ; from the intermuscular septum between it and the peronei muscles ; and from the aponeurosis over the tibialis. Inferiorly the tendon of the muscle enters a groove in the astragalus, and crosses the sole of the foot to its in- sertion into the great toe. In part the muscle is covered by the soleus ; but in part it is superficial, and is in contact with the fascia. It lies on the fibula and lower end of the tibia, and conceals the peroneal vessels. Along the inner side are the posterior tibial nerve and vessels : and contiguous to the outer margin, but separated by fascia, are the peronei muscles. Action. The foot being unsupported, the flexor bends the last phalanx of the great toe, and extends then tlie ankle. The foot resting on the ground, the muscle raises the heel ; and it moves back the fibula as the body rises from stooping. The FLEXOR LONGUS DiGiTORUiM (fig. 209, (flexoi* perforans) arises from the posterior surface of the tibia, extending from tlie attachment of the soleus to about three inches from the lower extremity ; and from the aponeurosis covering the tibialis posticus. Its tendon enters a partition in the annular ligament, which is superficial to the sheath of the tibialis ; and it divides in the sole of the foot into tendons for the four outer toes. The muscle is narrow and pointed above, and is placed beneath the DEEP LAYER OF MUSCLES. 611 soleus ; but in the lower half it is in contact with the fascia, and the pos- terior tibial vessels and nerve lie on it. The deep surface rests on the tibia and the tibialis posticus. Action. The muscle bends the farthest phalangeal joints of the four smaller toes, and tlien extends the ankle. Fig. 209. Deep Dissection of the Back of the Muscles: A. Popliteus. B. Outer, aud c, inner part of soleus, cut. D. Tibialis posticus. E. Flexor digitoruni. F. Flexor pollicis. G. Peroneus longus. II. Peroneus brevis. I. Tendo Acliillis. Arteries : a. Popliteal. h. Inferior internal, and c, inferior external articular. d. Anterior tibial. e. Posterior tibial, aud /, its coiuinunicatiug branch to peroneal. g. Peroneal artery. h. Continuation of peroneal to outer side of the foot. Nerves : 1. Internal popliteal. 2. Muscular branch of posterior tibial. 3. Posterior tibial. 4. Cutaneous plantar. Lro (Illustrations of' Dissections). If the toes are in contact with the ground, the flexor helps to raise the heel in walking ; and to move back the tibia in the act of rising from stooping. The TIBIALIS POSTICUS (fig. 209, occupies the interval between the bones of the leg, but it crosses over the tibia, interiorly to reach the inner side of the foot. The muscle arises from an aponeurosis superficial to it, and from the interosseous membrane, except about one inch below : from an impression along the outer border of the tibia, which reaches from the head of the bone to rather beyond the attachment of the flexor longus digitorum ; and from the adjacent inner surface of the shaft of the fibula 612 DISSECTION OF THE LEG. as far down as the lowest fifth. In the lower part of the leg the muscle is directed beneath the flexor digitorum ; and its tendon, entering the inner space in the annular ligament, reaches the inner side of the foot to be in- serted into the scaphoid and other bones (p. 625). The tibialis is concealed by the aponeurosis before mentioned, and is overla})ped by the neighboring muscles ; but in the lower part of the leg it is placed between the tibia and the long flexor of the toes. On the mus- cle are the posterior tibial vessels and nerve. The upper part presents two pointed processes of attachment — that to the tibia being the highest — be- tween which the anterior tibial vessels are directed forwards. Action. Its action on the movable foot is to shorten the inner border by drawing down the scaphoid bone, and to extend the ankle joint. The toes resting on the ground, it will aid the muscles of the calf in raising the heel in the progression of the body. In standing, the muscle can raise the inner border of the foot with the tibialis anticus, so as to throw the weight of the body on the outer edge. As the body rises from stooping, the tibialis draws back the bones of the leg, with the soleus. The aponeurosis covering the tibialis is attached laterally to the bones, but has a defined border inferiorly over the muscle. By one surface it gives origin to the flexors of the toes, and by the other to the tibialis. The POSTERIOR TIBIAE ARTERY (fig. 209, e) is one of the branches resulting from the bifurcation of the popliteal trunk. The vessel extends from the lower border of the popliteus muscle to the lower part of the internal annular ligament, where it ends in two plantar branches for the sole of the foot. At its origin the artery lies midway between the tibia and fibula, but as it approaches the lower part of the leg it gradually inclines inwards; and at its termination it is placed below the tibia, internal to the centre of the hollow between the heel and the inner ankle. As far as the middle (in length) of the leg the vessel is concealed by two muscles of the calf, viz., gastrocnemius and soleus ; but below that spot, as it lies between the tendo Achillis and the inner edge of the tibia, it is covered only by the teguments and the deep fascia. At its termina- tion it is placed beneath the annular ligament. For its upper half the trunk lies over the tibialis posticus, but afterwards on the flexor digitorum, and on the lower end of the tibia and the ankle-joint. On the outer side is the flexor pollicis. Between the heel and the ankle, the artery is placed between the ten- dons of the common flexor of the digits and special flexor of the great toe. Venae comites closely surround the vessel. The posterior tibial nerve is at first internal to the artery ; but at the distance of one inch and a half it crosses to the outer side, and retains that position throughout. This artery supplies branches to the muscles and the tibia, and a large l)eroneal trunk to the outer side of the leg. a. Muscular branches enter the deep layer of muscles, and the soleus ; and an offset from the branch to the soleus pierces the attachment of that muscle to the tibia, and ascends to the knee-joint. b. A nutritious artery of the shaft of the tibia is uncertain in its place of origin ; penetrating the tibialis, it enters the canal on the posterior sur- face of the bone, and ramifies in the interior. c. A communicating branch (/*) arises opposite the lower end of the POSTERIOR TIBIAE VEINS. 613 tibia, and passes outwards beneath the flexor pollicis, to unite in an arch with a corresponding offset of the peroneal artery. d. Articular branches arise from the artery opposite the ankle-joint, and enter the articulation. e. Cutaneous offsets appear through the fascia in the lower half of the leg ; the largest of these pierces the annular ligament, and accompanies the cutaneous plantar nerve to the sole of the foot. Peculiarities. If i\\e: posterior tibial artery is smaller than usual, or absent, its de- ficiencies in the foot will be supplied by a large communicating branch from the peroneal artery, which is directed inwards at the lower end of tlie tibia, and either joins the small tibial vessel, or runs alone to the sole of the foot. The PERONEAL ARTERY (fig. 209, g) is often as large as the posterior tibial, and arises from that vessel about one inch and a half from the begin- ning. It takes the fibula as its guide, and lying close to that bone in the fibres of the flexor pollicis, reaches the lower part of the interosseous mem- brane. At this spot it sends forwards a branch to the front of the leg (anterior peroneal) ; and it is directed onwards over the articulation be- tween the tibia and fibula (/^) to the outer side of the heel, where it termi- nates in branches, which anastomose with offsets of the posterior tibial, and with tlie tarsal and external plantar arteries. Two companion veins surround the artery ; and the nerve to the flexor pollicis lies on it generally. Branches. Besides the anterior peroneal, it furnishes muscular, nutri- tious, and communicating offsets. a. Muscular branches are distributed to the soleus, tibialis posticus, and flexor pollicis ; and some turn round the fibula to the peronei muscles, lying in grooves in the bone. b. The nutritious artery is smaller than that to the tibia, and is trans- mitted through the tibialis posticus to the aperture about the middle of the fibula. c. The anterior -peroneal branch passes forwards through an opening in the lower part of the interosseous membrane, and is continued to the dorsum and outer part of the foot ; on the front of the leg and foot it anas- tomoses with the external malleolar and tarsal branches of the anterior tibial artery. d. A communicating offset near the ankle joins in an arch with a simi- lar branch of the posterior tibial. Sometimes there is a second arch be- tween the same vessels. Peculiarities. The anterior branch of the peroneal may take the place of the anterior tibial artery on the dorsum of the foot. A compensating principle may be observed amongst the arteries of the foot as in those of the hand, by which the deficiency in one is supplied by an enlarged oil- set of another. The POSTERIOR TIBIAL VEINS begin on the inner side of the foot by the union of the plantar: they ascend one on each side of the artery, and unite with the anterior tibial at the lower border of the popliteus to form the large popliteal vein. They receive the peroneal veins, and branches cor- resj)onding with the offsets of the artery ; branches connect them with the saphenous veins. The POSTERIOR TIBIAL NERVE (fig. 209, a Continuation of the inter- nal popliteal, reaches, like the artery, from the lower border of the popli- teus muscles to the interval between the os calcis and the inner malleolus. 614 DISSECTION OF THE FOOT. Whilst beneath the annular ligament, or somewhat higher than it, the nerve divides into the internal and external plantar branches of the foot. Its connections with surrounding parts are the same as those of the artery ; but its position to the vessel changes, for it lies on the inner side above the origin of the peroneal offset, but thence to the termination, on the outer side. Its branches are muscular and cutaneous. Muscular branches enter the deep flexors, and arise either separately along the trunk, or together from the upper part of the nerve. There is an offset for each of the muscles except tlie popliteus ; but the branch for the tibialis is the largest, and that for the flexor pollicis lies on the pero- neal artery. A cutaneous nerve of the sole of the foot (fig. 209, *) begins above the os calcis, and piercing the internal annular ligament as two or more pieces, ends in the integuments of the inner and under parts of the heel ; this nerve will be followed to its termination in the dissection of the foot (fig. 210). The internal annular ligament stretches between the heel and the inner ankle, and serves to confine the tendons of the deep layer of muscles of the foot and toes. Attached by a pointed piece to the internal malleolus, the fibres diverge, and are inserted into the os calcis. One border (upper) is continuous with the fascia of the leg ; and the opposite gives attachment to the abductor pollicis muscle of the foot. Beneath it are sheaths for the tendons. The innermost incloses the tibialis posticus, lodged in a groove in the malleolus. Immediately be- hind this is another space for the flexor digitorum. And about three- quarters of an inch nearer the os calcis is the interval in which the flexor pollicis lies, resting in a groove in the astragalus. Each sheath is lined by a synovial membrane. Between the tendons of the two flexors of the digits are placed the tibial vessels and nerve. Section V. SOLE OF THE FOOT. Position. The foot is to be placed over a block of moderate thickness with the sole towards the dissector ; and the part is to be made tense by fixing the heel with hooks, and by separating, and by fastening apart the toes. Dissection, The skin is to be raised as two flaps, inner and outer, by means of one incision along the centre of the sole from the heel to the front ; and by another across the foot at the root of the toes. Afterwards the skin is to be removed from each toe, and the digital vessels and nerves on the sides are to be dissected out at the same time. In the fat near the heel the student should follow the cutaneous nerve of the sole {supra) ; and he may trace out, at a little distance from each border of the foot, some small branches of the plantar nerves and arteries. The subcutaneous fat is very abun ant. and forms a thick cushion over the parts that })ress most on the ground in standing, viz., over the os calcis, and the metatarso-phalangeal articulations. PLANTAR FASCIA. 615 Dissection. The fat should be now removed, and tlie plantar fascia laid bare. Beginning the dissection near the heel, follow forwards the fascia towards the toes, to each of which a process is to be traced. In the intervals between those [)rocesses the digital nerves and arteries will be detected amongst much fatty and fibrous tissues ; but the vessels and nerves to the inner side of the great toe and outer side of the little toe, pierce the fascia farther back than the rest. The student is next to define a transverse fibrous band between the toes, over the digital vessels and nerves ; and when this has been dis- played, he may remove the superficial fascia from the toes to see the sheaths of the tendons. Plantar fascia. The special fascia of the sole of the foot is of a pearly- vNdiite color and great strength, arid sends septa between the mus- cles. Its thickness varies in different parts of the foot ; and from this cir- cumstance, and the existence of longitudinal depressions over the two chief intermuscular septa, the fascia is divided into a central and two lateral parts. The central part, which is much the thickest, is pointed at its attach- ment to the os calcis, but widens and becomes thinner as it extends for- wards. A slight depression, corresponding with an intermuscular septum, marks its limit on each side : and opposite the heads of the metatarsal bones it divides into five processes, which send fibres to the teguments near the web of the foot, and are continued onwards to the toes, one to each. Where the pieces sepai-ate from each other, the digital vessels and nerves and the lumbricales muscles become superficial ; and transverse fibres arch over them. If one of the digital processes be divided longitudinally, and its parts reflected to the sides, it will be seen to join the sheath of the flexor ten- dons, and to be fixed laterally into the margins of the metatarsal bone, and into the transverse metatarsal ligament. The lateral pieces of the fascia are thinner than the central one. On the inner margin of the foot the fascia has but little strength, and is con- tinned to the dorsum ; but on the outer side it is increased in thickness, and presents a strong band between the os calcis and the projection of the fifth metatarsal bone. Dissection. To examine the septa, a longitudinal incision may be made along the middle of the foot through the central piece of the fascia, and a transverse one near the calcaneum. On detaching the fascia from the subjacent flexor brevis digitorum, by carrying the scalpel from before backwards, the septal processes will appear on the sides of that muscle. The intermuscular septa pass down on the sides of the flexor brevis digitorum, and a piece of I'ascia reaches across the foot from the one septum to the other, beneath that flexor, so as to isolate it. The inner septum lies between the short flexor and the abductor pol- licis; and the internal plantar nerve and vessels, and the tendon of the flexor pollicis longus, pass through it. The outer partition between the short flexor and the abductor minimi digiti, is pierced by the digital nerve and vessels for the outer side of the little toe. The superficial transverse ligament crosses the roots of the toes, and is contained in the skin forming the rudimentary web of the foot. It is attached at the ends to the sheath of the flexor tendons of the great and 616 DISSECTION OF THE FOOT. little toes, and is connected with the sheath of the others as it passes over. Beneath it the digital nerves and vessels issue. The sheaths of the flexor tendons (tig. 211, are similar to those of the fingers, though not so distinct, and serve to confine the tendons against the grooved bones. The sheath is weak opposite the articulations between the phalanges, but is strong opposite the centre of both the metatarsal and the next phalanx. Each is lubricated by a synovial membrane, and contains the tendons of the long and short flexor muscles. Dissection (fig. 210). In the sole of the foot the muscles are numer- ous, and have been arranged in four layers. To prepare the first layer all the fascia must be taken away ; but this dissection must be made with some care, lest the digital nerves and vessels, which become superficial to the central muscle towards the toes, should be injured. The tendons of the short flexor muscle are to be followed to the toes, and one or more of the sheaths in which they are contained should be opened. First layer of Muscles. In this layer are three muscles, viz., the flexor brevis digitorum, the abductor pollicis, and abductor minimi digiti. The short flexor of the toes lies in the centre of the foot ; and each of the others is in a line with the toe on which it acts. The ABDUCTOR POLLICIS (fig. 210, ^), the most internal muscle of the superficial layer, takes origin from the inner part of the larger tubercle on the under surface of the os calcis ; from the plantar fascia ; and from the lower border of the internal annular ligament, and the inner side of the foot as far as the scaj)hoid bone. In front the muscle ends in a ten- don, which is joined by fibres of the short flexor, and is inserted into the inner side of the base of the metatarsal phalanx of the great toe. The cutaneous surface of the muscle is in contact with the plantar fascia ; and the other touches the tendons of the tibial muscles, the plantar vessels and nerves, and the tendons of the long flexors of the toes with the accessorius muscle. Action. This abductor acts chiefly as a flexor of the metatarso-phalan- geal joint of the great toe, but it will abduct slightly that toe from the others. The FLEXOR BREVIS DIGITORUM (fig. 210, ®) (flexor perforatus) arises posteriorly by a pointed process from the inner part of the larger tubercle of the os calcis, and from the plantar fascia and tlie septa. About the centre of the foot the muscle ends in four small tendons, which are directed for- wards over the tendons of the long flexor, and entering the sheaths of the four smaller toes, are inserted into the middle phalanges. In the sheath of the toe the tendon of this muscle lies at first (in this position of the foot), on the long flexor ; opposite the centre of the metatarsal phalanx it is slit for the passage of the other, {ind is attached by two processes to the sides of the middle phalanx. The short flexor of the toes is contained in a sheath of the plantar fascia, and occupies the middle of the foot. It conceals the tendon of the long flexorvof the toes, the accessory muscle, and the external plantar vessels and nerve. Action. It bends the nearest phalangeal joint of the four smaller toes, like the flexor sublimis in the upper limb, and approximates the toes at the same time. The ABDUCTOR MINIMI DIGITI (fig. 210, ^) has a wide origin behind from the outer tubercle of the os calcis, Irom the fore part of the inner PLANTAR VESSELS AND NERVES. 61T tubercle, and from the plantar fascia and the external intermuscular sep- tum. It ends anteriorly in a tendon which is inserted into the outer side of the base of the metatarsal phalanx of the little toe. The muscle lies along the outer border of the foot, and conceals the flexor accessorius, and the tendon of the peroneus longus. On its inner side are the external plantar vessels and nerve. Sometimes a part of the muscle is fixed into the projection of the fifth metatarsal bone. Action. Though it abducts the little toe from the others, as the name signifies, its chief use is to bend the metatarso-phalangeal joint. Dissection. To bring into view the second layer or muscles and the plantar vessels and nerves, the muscles already examined must be re- flected. Cut through the flexor brevis at the os calcis, and as it is raised, notice a branch of nerve and artery to it. Dividing the abductor minimi digiti near its origin, and turning it to the outer side of the foot, seek its nerve.and vessel close to the calcaneum. The abductor pollicis can be drawn aside if it is necessary, but it may remain uncut till afterwards. Next the internal plantar vessels and nerve are to be followed forwards to their termination, and backwards to their origin ; and the external plantar vessels and nerve, the tendons of the long flexors of the toes, the accessory muscle, and the small lumbricales, should be freed from fat. The PLANTAR ARTERIES (fig. 210) are the terminal branches of the posterior tibial trunk, and supply digital offsets to the toes. They are two in number, and are named external and internal from their rela- tive position in the sole of the foot. Of the two the exteraal is the larger, and forms the plantar arch of arteries. The internal artery {h') is inconsiderable in size, and accompanies the internal plantar nerve, under cover of the abductor pollicis, as far as the middle of the foot, where it ends in four superficial digital branches. (Il- lustrations of Dissections, p. 404.) Branches. The artery furnislies muscular branches, like the nerve, to the abductor pollicis and flexor digitorum perforatus, and to the flexor brevis pollicis and the two internal lumbricales. Its superficial digital branches accompany the digital nerves of the internal plantar, and are thus disposed of: — The first is distributed to the inner side of the foot and great toe; the second lies over the first interosseous space ; the third corresponds with the second space; and the fourth is placed over the third space. At the root of the toes the last three join the deeper digital arteries in those spaces. The external artery (a) takes an arched course in the foot, with the concavity of the arch turned inwards. The vessel is first directed out- wards across the sole, and then obliquely inwards towards the root of the great toe, so that it crosses the foot twice. In the first half of its extent, viz., from the inner side of the calcaneum to the base of the metatarsal bone of the little toe, the artery is comparatively superficial; in the other half, between the little and the great toe, it lies deeply in the foot, and forms the plantar arch. Only the first part of the artery is now laid bare; the remaining part, supplying the digital branches, will be noticed after the examination of the third layer of muscles (p. G23). As far as the metatarsal bone of the little toe, the vessel is concealed by the abductor pollicis and the flexor brevis digitorum ; but for a short dis- tance near its termination it lies in the interval between the last muscle 618 DISSECTION OF THE FOOT and the abductor minimi digiti. In this extent it is placed on the os calcis, and the flexor accessorius: and it is accompanied by venae comites, and the external plantar nerve. Fig. 210. First View of the Sole of the Foot (Illustrations of Dissections). Muscles : A. Abductor pollicis. B. Flexor brevis dis^itorum. c. Abductor minimi digiti. H. Ligament of the toes. J rterie.R : n. External plantar. h. Internal plantar. Nerves : I. Internal plantar, with its four branches; 2, 3, 4 and .'5, for three toes and a half. 6. External plantar nerve, with two digital branches ; 7 and 8, for one toe and a half. Fig. 211. Second view of the Sole of the Foot (Illustrations of Dissections). Muscles : A. Musculus accessorius. B. Tendon of flexor digitorum longus. c. Tendon of flexor longus pollicis. D. Mp.rks the four lumbricales muscles, but the letters are put ou the tendons of the flexor digitorum perforans. E. Tendon of flexor perforatus. F. Tendon of flexor perforans. G. Sheath of flexor tendons. H. Tendon of peroneus longus. Arteries : a. Internal plantar. 1), External plantar. c. Branch to abductor minimi digiti. d. Branch to outer side of little toe. Nerves : I. Internal, and 2, external plantar. 4. Branch to flexor brevis pollicis. It supplies offsets to the muscles between which it lies, and others to th(i outer side of the foot for anastomosis with the peroneal artery. PLANTAR NERVES. 619 The PLANTAR NERA^ES (fig. 210) are derived from the bifurcation of the posterior tibial trunk behind the inner ankle. They are two in num- ber, like the arteries, and have the same anatomy as those vessels, for each accompanies a plantar artery; but the larger nerve lies with the smaller bloodvessel. The internal 'plantar nerve (’) courses between the short fiexor of the toes and the abductor pollicis, and giving but few muscular offsets, divides into four digital branches (^, for the su})ply of both sides of the inner tliree toes, and half the fourth ; it resembles thus the median nerve of the hand in the distribution of its branches. Muscular otfsets are given by it to the short flexor of the toes (perfo- ratus) and the abductor pollicis; and a few superficial twigs perforate the fascia. The four digital nerves have a numerical designation, and the first is ner.rest the inner border of the foot. The branch (^) to the inner side of the great toe is undivided, but the others are bifurcated at the cleft be- tween the toes. Muscular branches are furnished by these nerves before they reach the toes; thus, the first (most internal) supplies the flexor brevis pollicis; the second gives a branch to the inner lumbrical muscle, and the third, to the next lumbricalis. Digital nerves on the toes. Each of the outer three nerves, being divided at the spot mentioned, supplies the contiguous sides of two toes, whilst the first belongs alone to the inner side of the great toe ; all give offsets to the teguments, and the cutis beneath the nail, and articular fila- ments are distributed to the joints as in the fingers. The external plantar nerve (®) is spent chiefly in the deep muscles of the sole of the foot, but it furnishes digital nerves to both sides of the little toe, and the outer side of the next. It corresponds in its distribution with the ulnar nerve in the hand. It has the same course as the external plantar artery, and divides at the outer margin of the flexor brevis digitorum into a superficial and a deep portion : — the former gives origin to two digital nerves ; but the latter accompanies the arch of the plantar artery into the foot, and will be dis- sected afterwards. Whilst the external plantar nerve is concealed by the short flexor of the toes, it gives muscular branches to the abductor minimi digiti and the flexor accessorius. The digital branches of the external plantar nerve are two. One C^) is undivided ; it is distributed to the outer side of the little toe, and gives offsets to the flexor brevis minimi digiti, and oftentimes to the inter- osseous muscles of the fourth space. Tlie other (®) bifurcates at the cleft between the outer two toes, and supplies their collateral surfaces : this nerve communicates in the foot with the last digital branch of the internal plantar nerve. On tlie sides of the toes the digital nerves have the same distribution as those from the other plantar trunk, and end like them in a tuft of fine branches at the extremity of the digit. Dissection (fig. 211). To complete the preparation of the second layer of muscles, the origin of the abductor pollicis should be detached from the os calcis, and the muscle should be turned inwards. The internal plantar nerve and artery, and the superficial portion of the external plantar nerve, are to be cut across and thrown forwards ; but the external plantar artery 620 DISSECTION OF THE FOOT. and the nerve with it are not to be injured. All the fat, and the loose tissue and fascia, are then to be taken away near the toes. Second layer of muscles (fig. 211). In this layer are'the tendons of the two flexor muscles at the back of the leg, viz., flexor longus digi- torum and flexor longus pollicis, which cross one another. Connected with the former, soon after it enters the foot, is an accessory muscle ; and at its division into pieces four fleshy slips (lumbricales) are added to it. The tendon of the flexor longus digitorum (fig. 211,®), whilst entering the foot beneath the annular ligament, lies on the internal lateral ligament of the ankle joint. In the foot it is directed oblitjuely towards the centre, where it is joined by the tendon of the flexor longus pollicis and the accessory muscle, and divides into tendons for the four outer toes. Each tendon enters the sheath of the toe with, and beneath a tendon from the flexor brevis, e. About the centre of the metatarsal phalanx the tendon of the long flexor, f, is transmitted through the other, and passes onwards to be inserted into the base of the ungual phalanx. Uniting the flexor tendons with the two nearest phalanges of the toes are liga- mentous bands (lig. brevia), one to each, as in the hand ; and the one fixing the flexor perforans is anterior (p. 277). Action. It flexes the last phalangeal joint, and combines with the short flexor in bending the metacarpo-phalangeal joint. If it acted by itself it would tend to bring the toes somewhat inwards, in consequence of its ob- lique position in the foot. The lumbricales (fig. 211, ®) are four small muscles between the tendons of the flexor longus digitorum. Each arises from two tendons, with the exception of the most internal, and this is connected with the inner side of the tendon to the second toe. Each is inserted by a slip into the tibial side of the base of the metatarsal phalanx in the four outer toes, and sends an expansion to the aponeurotic covering on the dorsum of the phalanx. The muscles decrease in size from the inner to the outer side of the foot. Action. These small muscles will assist the flexors in bending the metatarso-phalangeal joint of the four outer toes ; and through their union with the long extensor tendon they will aid that muscle in straightening the two phlangeal joints. The accessorius muscle (fig. 211 ^) has two heads of origin : — One is mostly tendinous, and is attached to the under or the outer surface of the os calcis, and to the ligamentum longum plantae ; the other is large and fleshy, and springs from the inner or concave surface of the calcaneum. The fibres end in aponeurotic bands, which join the tendon of the flexor longus digitorum about the centre of the foot, and contribute slips to the pieces of that tendon going to the second, third, and fourth digits (Turner). The muscle is bifurcated behind, and the heads of origin are separated by the long plantar ligament. On it lie the external plantar vessels and nerve ; and the flexor brevis digitorum conceals it. Action. By means of its offsets to the tendons of certain digits the muscle helps to bend those toes. And from its position on the outer side and behind the long flexor to which it is united, it will oppose the inward action of that muscle, and will assist the other flexors in bending the toes directly back. The tendon of the flexor longus pollicis (fig. 211,^) is deeper in the sole of the foot than the flexor longus digitorum ; and, directed to the root of the great toe, it enters the digital slieath, to be inserted into the liase of the ungual phalanx. It is united to the long flexor tendon by a THIRD LAYER OF MUSCLES. 621 strong: tendinous process which, joined by bands of the accessorius, is con- tinued into the pieces of that tendon belonging to the second and third toes (Turner). Between tlie calcaneum and the internal malleolus this tendon lies in a groove in the astragalus ; and in the foot it occupies a hollow below the inner projection (sustentaculum tali) of the os calcis, being enveloped by a synovial membrane. Action, For the action of this muscle on the great toe, see page 610. Through the slip that it gives to the tendons of the flexor longus going to the second and third toes, it may bend those digits with the great toe. Dissection (fig. 212). For the dissection of the third layer of muscles, the accessorius and the tendons of the long flexor are to be cut through near the calcaneum, and turned towards the toes. Whilst raising the tendons the external plantar nerve and artery are not to be interfered with ; and two small nerves and vessels to the outer two lumbricales are to be looked for. Afterwards the areolar tissue is to be taken from the muscles now brought into view. Third layer of muscles (fig. 212). Only the short muscle of the great and little toes enter into this layer. On the metatarsal bone of the great toe the flexor brevis pollicis lies, and external to it is the adductor pollicis ; on the metatarsal bone of the little toe is placed the flexor brevis minimi digiti. Crossing the heads of the metatarsal bones is the trans- versalis pedis muscle. The fleshy mass between the adductor pollicis and the short flexor of the little toe consists of the iiiterossei muscles of the next layer. The FLEXOR BREVIS POLLICIS musclc (fig. 212, is tendinous and pointed posteriorly, but bifurcated in front. It is attached behind to the inner part of the under surface of the cuboid bene, and to a prolongation from the tendon of the tibialis posticus. Near the front of the metatarsal bone of the great toe it divides into two heads, which are inserted into the sides of the base of the metatarsal phalanx. Resting on the muscle at one part, and in the interval between the heads at another, is the tendon of the flexor longus pollicis. The inner head joins the abductor, and the outer is united with the adductor pollicis. A sesamoid bone is developed in the tendon connected with each head. Action. By its attachment to the first phalanx it flexes the metatarso- phalangeal joint of the great toe. The ADDUCTOR POLLICIS (fig. 212, ®), which is larger than the pre- ceding muscle and external to it, arises from the sheath of the tendon of the peroneus longus, and from the bases of the second, third, and fourth metatarsal bones. Anteriorly the muscle is united with the outer head of the short flexor, and is inserted with it into the base of the metatarsal phalanx of the great toe. To the inner side is the flexor brevis ; and beneath the outer the exter- nal plantar vessels and nerve are directed inwards. Action. Its first action will be to adduct the great toe to the others, and it will help afterwards in bending the matatarso-phalangeiil joint of the toe. The TRANSVERSALis PEDIS (fig. 212, is placed transversely over the heads of the metatarsal bones. Its origin is by fleshy bundles from the capsule of the metatarso-phalangeal articulations of the four outer toes (frequently not from the little toe), and from the fascia covering the inter- ossei muscles. Its insertion into the great toe is united with that of the adductor pollicis. 622 DISSECTION OF THE FOOT. Fig. 212. Third View of the Sole of the Foot, (Illustrations of Dissections.) Muscles : A. Flexor brevis pollicis. B. Adductor pollicis. c. Flexor brevis minimi digit!. D. Transversalis pedis. Arteries : a. Internal plantar, cut. h. External plantar; and c*. Its four digital branches. Nei ves : 1. Internal plantar. 2. External plantar. 3. Its superficial part, cut. 4. The deep part, with the plantar arch. 5. Two offsets to the outer two lumbricales muscles. Fig 213. Fourth View of the Sole of the Foot. (Illustrations of Dissections.) Muscles : 0 . Three plantar interossei. 1, Four dorsal interossei. Arteries : a. Internal plantar, cut. b. External plantar. c. Its four digital branches. d. Plantar arch. e. Anterior tibial entering the sole. /. Arteria magiia pollicis y. Branch to inner side of great toe. b. Branch for the supply of great toe and the next. Nerves : 1. Internal plantar, cut. 2. External plantar. 3. Its superficial ; and 4. its deep part, both cut ; the latter supply- ing offsets to the interossei muscles. The cutaneous surface is covered by the tendons, and the nerves of the toes ; and the opposite surface is in contact with the interossei muscles and the digital vessels. Action. It will adduct tlie great toe to the others, and then approxi- mate the remaining toes. PLANTAR ARCH OF VESSELS. 623 Tlie FLEXOR BREVIS MINIMI DiGiTi (fig. 212, Is ii Small narrow muscle on the metatarsal bone of* the little toe, and resembles one of the interossei. Arising behind from the metatarsal bone and the sheath of the peroneus longns, it blends with the inferior ligament of the metatarso- phalangeal articulation, and is inserted into the base of the metatarsal phalanx of the toe; it is united also by fleshy fibres with the fore part of the metatarsal bone. Action. Firstly it bends the metatarso-phalangeal joint, and nextly it draws down and adducts the fore part of the fifth metatarsal bone. Dissection (fig. 2)3). In order that the deep vessels and nerves may be seen, the flexor brevis and adductor pollicis are to be cut through at the posterior part, and thrown towards the toes; but the nerves supplying them are to be preserved. Beneath the adductor lie the plantar arch, and the external plantar nerve, with their branches; and in the first interos- seous S{)ace is the part of the dorsal artery of the foot that enters the sole. All these vessels and nerves with their branches require careful cleaning. The muscles projecting between the metatarsal bones are the interossei; the fascia covering them should be removed. The PLANTAR ARCH (fig. 213, d') is the part of the external plantar artery which reaches from the base of the metatarsal bone of the little toe to the back of the first interosseous space: internally the arch is completed by a communicating branch from the dorsal artery of the foot (e) (p. G24). It is placed across the tarsal ends of the metatarsal bones, in contact with the interossei, but under the flexor tendons, and the adductor pollicis to which it gives many brandies. Venae comites lie on the sides of the artery, and the external plantar nerve accompanies it. From the front or convexity of the arch the digital branches are sup- plied, and from the opposite side small nutritive branches arise. Tliree small arteries, the ^posterior 'perforating., leave the under part: these pass to the dorsum of the foot through the three outer metatarsal spaces, and anastomose with the dorsal interosseous branches of the ante- rior tibial artery. The digital branches (c) are four in number, and supply both sides of the three outer toes, and half the next. One to the outer side of the little toe is single ; but the others lie over the interossei in the outer three metatarsal spaces, but beneath the transversalis pedis (fig. 212), and bi- furcate in front to supply the contiguous sides of two toes. They give fine offsets (fig. 212) to the interossei, to some lumbricales, and the transver- salis pedis; and at the point of division they send small communicating branches — anterior perforating., to join the interosseous arteries on the dorsum of the foot. The first digital runs on the outer side of the little toe, supplying the flexor brevis minimi digiti, and distributes small arteries to the teguments of the outer border of the foot. The second belongs to the sides of the fifth and fourth toes, and fur- nishes a branch to the outer lumbrical muscle. The third is distributed to the contiguous sides of the fourth and third toes, and emits a branch to the third lumbricalis. The fourth^ or most internal, corresponds with the second interosseous space, and ends like the others on the third and second digits; it may assist in supplying the third lumbricalis. 624 DISSECTION OF THE FOOT. The last two digital are joined by superficial digitalis branches of the internal plantar at the root of the toes. On the sides of the toes the disposition of the arteries is like that of the digital in the hand. They extend to the end, where they unite in an arch, and give offsets to the sides and ball of the toe: and the artery on the second digit anastomoses with a branch from the anterior tibial artery. Near the front of both the metatarsal and the next phalanx, they form anastomotic loops beneath the flexor tendons, from which the phalangeal articulations are supplied. Tlie DORSAL ARTERY OF THE FOOT (fig. 213, e) enters the sole at the posterior part of the first (inner) metatarsal space, and ends by inoscu- lating witli the plantar arch. By a large digital artery it furnishes branches to both sides of the great toe and half the next, in the same man- ner as the radial artery in the hand is distribut'd to one digit and a half. The digital branch (/) (art. magna pollicis) extends to the front of the first interosseous space, and divides into collateral branches (Ji) for the contiguous sides of the great toe and the next; near the head of the meta- tarsal bone it sends inwards, beneath the flexor muscles, a digital branch (_^) for the inner side of the great toe. These arteries have the same arrangement along the toes as the other digital branches; and that to the second digit anastomoses at the end of the toe with a branch of the plantar arch. Externa], plantar nerve (fig. 213, ^). The deep branch (^) of this nerve accompanies the arch of the artery, and ends internally in the ad- ductor pollicis. It furnishes branches to all the interossei ; to the trans- versalis pedis; and to the two external lumbrical muscles. The nerve corresponds with the deep portion of the ulnar nerve in the hand. Dissection. It will be needful to remove the transversalis pedis muscle, to see a ligament across the heads of the metatarsal bones. The transverse metatarsal ligament is a strong fibrous band, like that in the hand (p. 280), which connects together all the metatarsal bones at their anterior extremity. A thin lascia covering the interossei muscles is connected to its hinder edge. It is concealed by the transversalis pedis, and by the tendons, vessels, and nerves of the toes. Dissection. To complete the dissection of the last layer of muscles, the flexor brevis minimi digiti may be detaclied and thrown forwards. Di- viding then the metatarsal ligament between tlie bones, the knife is to be carried directly backwards for a short distance in the centre of each inter- osseous space, except the first, in order that the two interossei muscles may be separated from each other. All the interossei are visible in the sole of the foot. The fascia covering the muscles should be taken away if any remains, and the branches of the external plantar nerve to them should be dissected out. Fourth layer of muscles (fig. 213). In the fourth and last layer of the foot are contained the interossei, and the tendons of the tibialis pos- ticus and peroneus longus. The INTEROSSEI MUSCLES (fig. 213) are situate in the intervals between the metatarsal bones : they consist of two sets, idantar and dorsal, like the interossei in the hand. Seven in number, there are three plantar and four dorsal ; and two are found in eacli space, exce[)t tlie innermost. Tlie plantar interossei., o, belong to three outer metatarsal bones (fig. 213), and are slender fleshy slips. They arise from the under and inner FOURTH LAYER OF MUSCLES. 625 surfaces of those bones ; and are inserted partly into the tibial side of the base of the metatarsal phalanx of the same toes, and partly by an expan- sion from each to the extensor tendons on the dorsum of the phalanx. These muscles are smaller than the dorsal, and are placed more in the sole of the foot. The dorsal interossei, i, one in each space, arise by two heads from the lateral surfaces of the bones between which they lie ; and are inserted like the others into the side, and on the dorsum of the metatarsal phalanx of certain toes : Thus, the inner two muscles belong to the second toe, one to each side ; the next appertains to the outer side of the third toe ; and the remaining one to the outer side of the fourth toe. The interossei are crossed by the external plantar artery and nerve, and their digital branches, and lie beneath the transversalis pedis and the meta- tarsal ligament. The posterior perforating arteries pierce the hinder ex- tremities of the dorsal set. Action. Like the interossei of the hand (p. 281) they will contribute to the bending of the metatarso-phalangeal joints by the flexors, and will help the extensors to straighten the last two phalangeal joints. They can act also as abductors and adductors of the toes. Thus the plantar set will bring the three outer towards the second toe ; and the dorsal muscles will abduct from the middle line of the second toe — the two attached to that digit moving it to the right and left of the said line. Dissection. Following the tendon of the tibialis posticus muscle from its position behind the inner malleolus to its insertion into the .scaphoid bone, trace the numerous processes that it sends forwards and outwards. Open also the fibrous sheath of the tendon of tlie peroneus longus, which crosses from the outer to the inner side of the foot. The tendon of the tibialis posticus is continued forwards over the internal lateral ligament of the ankle joint, and over theastragalo scaphoid articulation to be inserted into the prominence of the scaphoid bone. From its insertion processes are continued to many of the other bones of the foot : One is directed backwards to the margin of the groove in the os calcis for the tendon of the flexor longus pollicis. Two offsets are directed forwards ; one to the internal cuneiform bone ; the other, much the largest, is attached to the middle and outer cuneiform, to the os cuboides, and to the bases of the second, third, and fourth metatarsal bones. In other words, pieces are fixed into all the tar.sal bones except one (astragalus) ; and into all the metatarsal bones except two (first and fifth). Where the tendon is placed beneath the articulation of the astragalus, it contains a sesamoid bone, or fibro-cartilage. The tendon of the peroneus longus muscle winds round the cuboid bone, and is continued inwards in the groove on the under surface, to be inserted into the internal cuneiform bone, and the base of the metatarsal bone of the great toe ; and sometimes by a slip into the base of the second metatarsal bone. In the sole of the foot (fig. 213), it is contained in a sheath which is crossed, towards the outer part, by the fibres of the long plantar ligament prolonged to the tarsal ends of the third and fourth metatarsal bones ; but it is formed internally only by areolar tissue. A separate synovial mem- brane lubricates the sheath. Where the tendon turns round the cuboid bone it is thickened, and con- tains fibro-cartilage or a sesamoid bone. 40 626 DISSECTION OF THE LEG. Section VI. THE FRONT OF THE LEG. Position. The limb is to be raised to a convenient height by blocks beneath the knee, and the foot is to be extended in order that the muscles on the front of the leg may be put on the stretch. Dissection. To enable the dissector to raise the skin from the leg and foot, one incision should be made along the middle line from the knee to the toes, and this should be intersected by cross cuts at the ankle and the root of the toes. After the flaps of skin are reflected, the cutaneous vessels and nerves are to be looked for. At the upper and inner part of the leg are some fila- ments from the great saphenous nerve ; and at the outer side others, still smaller, from the external popliteal nerve. Perforating the fascia in the lower third, on the anterior aspect, is the musculo-cutaneous nerve, whose branches should be pursued to the toes. On the dorsum of the foot is a venous arch, which ends laterally in the saphenous veins. On the outer side is the external saphenous nerve ; and about the middle of the instep the internal saphenous nerve ceases. In the interval between the great toe and the next is the cutaneous part of the anterior tibial nerve. The digital nerves should be traced to the ends of the toes by removing the integuments : and after the several vessels and nerves are dissected, the fat is to be taken away, in order that the fascia may be seen. The venous arch on the dorsum of the foot has its convexity turned forwards, and receives digital branches from the toes ; at its concavity it is joined by small veins from the instep. Internally and externally it unites with the saphenous veins. The internal saphenous vein begins at the inner side of the great toe, and in the arch. It ascends along the inner side of the foot, and in front of the inner ankle to the inside of the leg (p. 606). Branches enter it from the inner side and sole of the foot. The external saphenous vein begins on the outside of the little toe and foot, as well as in the venous arch ; and it is continued below the outer ankle to the back of the leg (p. 606). Cutaneous Nerves (flg. 214). The superficial nerves on the front of the leg and foot are derived mainly from branches of the popliteal trunks, viz., from the musculo-cutaneous and anterior tibial nerves of the external popliteal, and from the external saphenous nerve of the internal popliteal. Some inconsiderable offsets ramify on the sides of the leg from the internal saphenous and external popliteal. The musculo-cutaneous nerve (^) ends on the dorsum of the foot and toes. Perforating tlie fascia in the lower third of the leg with a cutane- ous artery, it divides into two principal branches (inner and outer), which give dorsal digital nerves to the sides of all the toes, except the outer part of the little toe and the contiguous sides of the great toe and the next. The branches may be traced in the integument as lar as the end of the last phalanx. The i?iner branch if) communicates with the internal saphenous nerve. CUTANEOUS NERVES ON THE FRONT. 627 and supplies the inner side of the foot and great Fig. 214. toe : it joins also the anterior tibial nerve. » The outer branch (*) divides into three nerves ; these lie over the three outer interosseous spaces, and bifurcate at the web of the foot for the con- tiguous sides of the four toes corresponding with those spaces ; it joins the external saphenous nerve on the outer part of the foot. The anterior tibial nerve (') becomes cutane- ous in the first interosseous space, and is distri- buted to that space, and to the opposed sides of the great toe and the next. The musculo-cuta- neous nerve joins it, and sometimes assists in supplying the same toes. The external saphenotis nerve (fig. 207, comes from the back of the leg below the outer %V // ankle, and is continued along the foot to the out- side of the little toe ; all the outer margin of the foot receives nerves from it, and the offsets to- wards tlie sole are larger than those to the dor- sum. Occasionally it supplies both sides of the little toe and part of the next. Internal saphenous nerve (®). A part of this nerve is continued along the vein of the same name to the middle of the instep, where it ceases mostly in the integuments, but some branches pass through the deep fascia to end in the tarsus. HhQ fascia of the front of the leg is thickest near the knee joint, where it gives origin to muscles. It is fixed laterally into the tibia and fibula. Intermuscular septa are prolonged from the deep surface ; and one of these, which is at- tached to the fibula, separates the muscles on the front from those on the outer side of the leg. Superiorly the fascia is connected to the heads of the leg bones, but inferiorly it is continued to the dorsum of the foot. Above and below tlie ankle joint it is strength- ened by some transverse fibres, and gives origin to the two parts of the anterior annular ligament ; and below the end of the fibula it forms another band, the external annular ligament. Dissection. The fascia is to be removed from the front of the leg and the dorsum of the foot, but the thickened band of the annular ligament above and below the end of the tibia is to be left. In separating the fascia from the subjacent muscles, let the edge of the scalpel be directed upwards. In like manner the fascia may be taken from the peronei muscles on the outside of the fibula, but without destroying the band (external annular ligament) below that bone. On the dorsum of the foot the dorsal vessels with their nerve are to be displayed, and the tendons of the short and long extensors of the toes are THE AND CcTTANEOtrs Nerves of Front of the Leg Foot. 1. Anterior tibial. 2. Musculo-cntaneous, with 3, its inner, and 4, its outer piece ; the usual distri- bution is not shown in the cut. 5. Internal saphenous. 6. Offsets of external popliteal. 628 DISSECTION OF THE LEG. 1o be traced to the ends of the digits. In the leg the anterior tibial nerve and vessels are to be followed from the dorsum into their intermuscular space, and are then to be cleaned as high as the knee. The anterior annular ligament consists of two parts, upper and lower, which confine the muscles in their position : the former serving to bind the fleshy parts to the bones of the leg, and the latter to keep down the tendons on the dorsum of the foot : — The upper part (fig. 215, ^), above the level of the ankle-joint, is at- tached laterally to the bones of the leg ; it possesses one sheath with synovial membrane for the tibialis anticus. The lower part is situate in front of the tarsal bones. It is inserted externally by a narrow piece into the upper surface of the os calcis, in front of the interosseous ligament ; and internally, where it is thin and widened, into the plantar fascia and the inner malleous. In this piece of the ligament there are three sheaths : an inner one for the tibialis anticus ; an outer for the extensor longus digitorum and peroneus tertius ; and an intermediate one for the extensor pollicis. Separate synovial membranes line the sheaths. The external annular ligament is placed below the fibula, and is at- tached on the one side to the outer malleolus, and on the other to the os calcis. Its lower edge is connected by fibrous tissue to the sheaths of the peronei muscles on the outer side of the os calcis. It contains the two lateral peronei muscles in one compartment ; and this is lined by a syno- vial membrane, which sends two offsets below into the sheaths of the peronei muscles. The MUSCLES ON THE FRONT OF THE LEG (fig. 215) are three in num- ber. The large muscle next the tibia is the tibialis anticus ; that next the fibula, the extensor longus digitorum ; whilst a small muscle, appa- rently the lower part of the last, with a separate tendon to the fifth meta- tarsal bone, is the peroneus tertius. The muscle between the tibialis and extensor digitorum, in the lower half of the leg, is the extensor pollicis. On the dorsum of the loot only one muscle appears, the extensor brevis digitorum. The TIBIALIS ANTICUS (fig. 215, reaches the tarsus: it is thick and fleshy in the upper, but tendinous in the lower part of the leg. It arises from the outer tuberosity and the upper half or more of the tibia ; from the contiguous part of the interosseous ligament ; and from the fascia of the leg and the intermuscular septum between it and the next muscle. Its tendon begins below the middle of the leg, and passes through com- partments in the pieces of the annular ligament, to be inserted into the internal cuneiform bone, and the metatarsal bone of the great toe. The muscle is subaponeurotic. It lies at first outside the tibia, resting on the interosseous membrane, but it is then placed, successively, over the end of the tibia, the ankle-joint, and the inner tarsal bones. The outer border touches the extensor muscles of the toes, and conceals the anterior tibial vessels. Action. Supposing the foot not fixed, the tibialis bends the ankle, moves the great toe towards tl.e middle line of the body, and raises the inner border of the foot. If the foot is fixed it can lift the inner border with the tibialis posticus, and support the foot on the outer edge. If the tibia is slanting backwards, as when the advanced limb reaches the ground in walking, it can bring forwards and make steady that bone. FLEXORS OF THE ANKLE-JOINT. 629 The EXTENSOR PROPRius POLLicis (fig. 215) IS deeply plaeed at its origin between the former muscle and the extensor longus digitorum, but its tendon becoms superficial on the dorsum of the foot. The muscle arises from the middle three-fifths of the narrow anterior part on the inner surface of the fibula, and from the interosseous ligament for the same dis- tance. At the ankle it ends in a tendon, which comes to the surface through a sheath in the lower piece of the annular ligament, and continues over the inner part of the tarsus to be inserted into the base of the last phalanx of the great toe. The anterior tibial vessels lie on the inner side of the muscle as low as the sheath in the ligament, but afterwards on the outer side of its tendon, so that they are crossed by it beneath the ligament. Action. It straightens the great toe by extending the phalangeal joints, and afterwards bends the ankle. When the foot is fixed on the ground and the tibia slants backwards, the muscle can draw forwards that bone. The EXTENSOR LONGUS DIGITORUM (fig. 215, is fleshy in the leg, and tendinous on the foot, like the tibial muscle. Its origin is from the head and three-fourths of the narrow part of the inner surface of the fibula; from tlie external tuberosity of the tibia, and about an inch (above) of the interosseous membrane ; and from the fascia of the leg and the intermus- cular septum on each side. The tendon enters its sheath in the annular ligament with the peroneus tertius, and divides into four pieces. Below the ligament these slips are continued to the four outer toes, and are in- serted into the middle and ungual phalanges : — On the metatarsal phalanx the tendons of the long and short extensor join with prolongations from the interossei and lumbricales to form an aponeurosis ; but a tendon from the short extensor is not united to the expansion on the little toe. At the further end of this phalanx the apo- neurosis is divided into three parts — a central and two lateral ; the central piece is inserted into the base of tlie middle phalanx, while the lateral unite at the front of the middle, and are fixed into the ungual phalanx. In the leg the muscle is placed between the peronei on the one side, and the tibialis anticus and extensor proprius pollicis on the other. It lies on the fibula, the lower end of the tibia, and the ankle-joint. On the foot the tendons rest on the extensor brevis digitorum ; and the vessels and nerve are internal to them. Action. The muscle extends the joints of the four outer toes from root to tip, as in the fingers ; and still acting, bends the ankle-joint. If the tibia is inclined back, as when the foot reaches the ground in walking, it will be moved forwards by this and the other muscles on the front of the leg. The 'peroneus tertius is situate below the extensor longus digitorum, from which it is seldom separate. It arises from the lower fourth of the narrow part of the inner surface of the fibula, from the lower end of the interosseous ligament, and from the intermuscular septum between it and the peroneous brevis muscle. And it is inserted into the tarsal end (up- per surface) of the metatarsal bone of the little toe. This muscle has the same conneetions in the leg as the lower part of the long extensor, and is contained in the same space in the annular ligament. Action. The muscle assists the tibialis in bending the ankle, and in 630 DISSECTION OF THE LEG. (IraMniig forwards the fibula when the leg is advanced to make a step in walking. The ANTERIOR TiBJAL ARTERY (fig. 215/) extends from the bifurca- tion of the popliteal trunk to the front of the ankle joint. At this spot it becomes the dorsal artery of the foot. Fig. 215. Anterior Tibial Vessel and Muscles (Quain’s Arteries). 1. Tibialns anticus muscle. 3. Part of anterior annular ligament. 2. Extensor pollicis and extensor longus digi- 4. Anterior tibial artery; the nerve outside it torum drawn aside. is the anterior tibial. The course of the artery is forwards through the aperture in the upper part of the interosseous membrane, along the front of that membrane, and over the tibia to the foot. A line from tlie inner side of the head of the fibula to the centre of the ankle will mark the position of the vessel. For a short distance (about two inches) the artery lies between the ANTERIOR TIBIAL VESSELS. 631 tibialis anticiis and the extensor longus digitorum ; afterwards it is placed between the tibial muscle and the extensor proprius pollicis till near the lower end, where the last muscle becomes superficial, and crosses to the inner side. The vessel rests on the interosseous membrane in two-thirds of its extent, being overlapped by the fleshy bellies of the contiguous muscles, so that it is at some depth from the surface ; but it is placed in front of the tibia and the ankle joint in the lower third, and is compara- tively superficial between the tendons of the muscles. • Venae comites entwine around the artery, covering it very closely with cross branches on the upper part. The anterior tibial nerve approaches the tibial vessels about the middle third of the leg, and continues with them, crossing once or twice : at the lower end of the artery the nerve lies on the outer side. Branches. In the leg the anterior tibial artery furnishes mostly mus- cular offsets, but near the knee and ankle the following named branches take origin. a. Cutaneous branches arise at intervals ; and the largest accompanies the musculo-cutaneous nerve, and supplies the contiguous muscles. b. A recurrent branch arises as soon as the trunk appears above the interosseous membrane, and ascends in the tibialis anticus to the knee joint : on the joint it anastomoses with the other articular arteries. c. Malleolar arteries (internal and external) spring near the ankle joint, and are distributed over the ends of the tibia and fibula. The internal is the least regular in size and origin ; the external anastomoses with the anterior peroneal artery. d. Some small articular branches are supplied from the lower end of the artery to the ankle joint. The DORSAL ARTERY of the foot is the continuation of the anterior tibial, and extends from the front of the ankle joint to the posterior part of the first interosseous space : at this interval it passes downwards between the heads of the interosseous muscle, to end in the sole (p. 624). The artery is supported by the inner row of the tarsus, viz., the astra- galus, and the scaphoid and cuneiform bones ; and it is covered by the integuments and the deep fascia, and by the inner piece of the extensor brevis muscle. The tendon of the extensor pollicis lies on the inner side, and that of the extensor longus digitorum on the outer side, but neither is near the vessel. The veins have the same position with respect to the artery as in the leg ; and the nerve is external to it. Peculiarities. On the dorsum of the foot the artery is often removed further outwards than the line from the centre of the ankle to the posterior part of the first interosseous space. Further, the place of the artery may be taken by a large anterior peroneal branch. Branches. Offsets are given to the bones and ligaments of the foot : those from the outer side of the vessel are named tarsal and metatarsal from their distribution. A small interosseous branch is furnished to the first metatarsal space. a. The tarsal branch arises opposite the scaphoid bone, and runs be- neath the extensor brevis digitorum to the outer side of the foot, where it divides into twigs that inosculate with the metatarsal, plantar, and ante- rior peroneal arteries : it supplies offsets to the extensor muscle beneath which it lies. 632 DISSECTION OF THE LEG. h. The metatarsal branch takes an arched course to the outer part of the foot, near the base of the metatarsal bones and beneath the extensor muscle, and anastomoses with the external plantar and tarsal arteries. c. From the arch of the metatarsal branch three dorsal interosseous arteries are furnislied to the three outer metatarsal spaces ; and the exter- nal of these sends a branch to the outer side of the little toe. They sup- ply the interossei muscles and divide at the cleft of tlie toes into two small dorsal digital branches. At the fore part of the metatarsal space each interosseous branch joins a digital artery in the sole of the foot by means of the anterior per- forating twig ; and from the beginning of each a small branch, posterior perforating^ descends to the plantar arch. d. The first interosseous branch (art. dorsalis pollicis) arises from the trunk of the artery as this is about to leave the dorsum of the foot ; it ex- tends forwards in the space between the first two toes, and is distributed by dorsal digital pieces like the other dorsal interosseous offsets. The ANTERIOR TiBiAL VEINS have the same extent and connections as the vessel they accompany. They take their usual position along the artery, one on each side, and form loops around it by cross branches ; tl)ey end in the popliteal vein. The branches they receive correspond with those of the artery ; and they communicate with the internal saphenous vein. Dissection. To examine the extensor brevis digitorum on the dorsum of the foot, cut through the tendons of the extensor longus and peroneus ter- tius below the annular ligament, and throw them towards the toes. The hinder attachment of the muscle to the os calcis is to be defined. The EXTENSOR BREVIS DIGITORUM arises from the outer surface of the os calcis in front of the sheath for the peroneus brevis muscle, and from the lower band of the anterior annular ligament. At the back of the meta- tarsal bones the muscle ends in four tendons, which spring from as many fleshy bellies, and are inserted into the four inner toes. The tendon of the great toe has a distinct attachment to the base of the metatarsal phalanx ; but the rest are united to the outer side of the long extensor tendons, and assist to form the expansion on the metatarsal phalanx (p. 629). The muscle lies on the tarsus, and is partly concealed by the tendons of the long extensor. Its inner belly crosses the dorsal artery of the foot. Action. Assisting the long extensor, it straiglitens the four inner toes, separating slightly from each other. Dissection. The branches of artery and nerve which are beneath the extensor brevis will be laid bare by dividing that muscle near its front, and turning it upwards. By cutting through the lower band of the annular ligament over the tendon of the extensor pollicis, and throwing outwards the external half of it, — tlie different sheaths of the ligament, the attachment to the os calcis, and the origin of the extensor brevis digitorum from it may be ob- served. The anterior tibial and musculo-cutaneous nerves are now to be followed upwards to their origin from the external poi)liteal : and a small branch to the knee-joint from the same source is to be traced through the tibialis anticus. Nerves to the front of the leg. Between the fibula and the pero- neus longus muscle the external popliteal nerve divides into recurrent articular, musculo-cutaneous, and anterior tibial branches. PERONEI MUSCLES. 633 The recurrent articular branch is small, and takes the course of the artery of the same name through the tibialis anticus muscle to the knee joint. The musculo-cutaneous nerve is continued between the extensor longus digitorum and the peronei muscles to the lower third of the leg, where it pierces the fascia, and is distributed to the dorsum of the foot and the toes (p. 626). Before the nerve becomes cutaneous it furnishes branches to the two larger peronei muscles. The anterior tihial nerve (fig. 215) (interosseous) is directed beneath the extensor longus digitorum, and reaches the tibial artery about the middle third of the leg. From this spot it takes the course of the vessel along the foot to the first interosseous space (p. 627). In the leg it crosses the anterior tibial vessels once or more, but on the foot it is generally external to the dorsal artery. Branches. In the leg the nerve supplies the anterior tibial muscle, the extensors of the toes, and the peroneus tertius. On the dorsum of the foot it furnishes a considerable branch to the short extensor ; this is enlarged, and gives offsets to the articulations of the foot. Muscles on the outer part of the leg (fig. 209). Two muscles occupy this situation, and are named peronei from their attachment to the fibula; they are distinguished by the terms longus and brevis. Intermus- cular processes of fascia, which are attached to the fibula, isolate these muscles from others. The PERONEUS LONGUS (fig. 209, ®), the more superficial of the two muscles, passes into the sole of the foot round the outer border. It arises from the head, and the anterior surface of the shaft of the fibula for two- thirds of the length, gradually tapering downwards ; from the external border nearly to the malleolus ; and from the fascia and the intermuscular septa. Inferiorly it ends in a tendon which is continued through the ex- ternal annular ligament, with the peroneus brevis, lying in the groove at the back of the external malleolus ; and it passes finally in a separate sheath, below the peroneus brevis along the side of the calcis and through the groove in the outer border of the cuboid bone, to the sole of the foot. Its position in the foot, and its insertion are described before (p. 625). In the leg the muscle is immediately beneath the fascia, and lies on the peroneus brevis. Beneath the annular ligament it is placed over the middle piece of the external lateral ligament of the ankle with the peroneus brevis, and is surrounded by a single synovial membrane common to both. The extensor longus digitorum and the soleus are fixed to the fibula late- rally with respect to it, one being on each side. Action. With the foot free the muscle extends the ankle : then it can depress the inner, and raise the outer border of the foot in the movement of eversion. When the foot rests on the ground it assists to lift the os calcis, and the weight of the body as in standing on the toes, or in walking. And in rising from a stooping posture it draws back the fibula. The PERONEUS BREVIS (fig. 209, °) reaches the outer side of the foot, and is smaller than the preceding muscle, and inferior in position to it. It arises from the anterior surface of the shaft of the fibula for about the lower two-thirds, extending upwards by a pointed piece internal to the other peroneus ; and from the intermuscular septum in front. Its tendon passes with that of the peroneus longus through the external annular liga- ment, and is placed next the fibula as it turns below this bone. Escaped 634 DISSECTION OF THE LEG. from the ligament, the tendon enters a distinct fibrous sheath, which con- ducts it along the tarsus to its insertion into the projection at the base of the metatarsal bone of the little toe. In the leg the muscle reaches in front of the peroneus longus. On the outer side of the os calcis it is contained in a sheath above the tendon of the former muscle ; and each sheath is lined by a prolongation from the common synovial membrane behind the outer ankle. Action. If the foot is unsupported this peroneus extends the ankle, and moves the foot upwards and outwards in eversion. Like the long muscle, it is able if the foot is supported to raise the heel, and to bring back the fibula as the body rises from stooping. Section YII. LIGAMENTS OF THE KNEE, ANKLE, AND FOOT. Directions. In examining the remaining articulations of the limb, the student may take first the knee-joint, unless this has become dry ; in that case the ligaments of the leg, ankle-joint, and foot may be dissected whilst the knee is being moistened. Dissection. For the preparation of the ligaments of each articulation, it is sufficient to detach the muscles and tendons from around it, and to remove the areolar tissue or fibrous structure which may obscure or con- ceal the ligamentous bands. In tlie knee a kind of aponeurotic capsule is to be defined on the front of the joint. Some tendons, namely, those of the biceps, popliteus, adductor magnus, and semimembranosus, are to be followed to their insertion, and a part of each is to be left. Articulations of the knee. The knee is the largest hinge joint in the body, and is formed by the contiguous ends of the tibia and femur, with the patella. The articular surfaces of the bones are covered with cartilage, and are maintained in apposition by strong and numerous liga- ments. The capsule (fig. 216) is an aponeurotic covering on the front of the joint, which closes the wide intervals between the anterior and the lateral ligaments ; and is derived from the fascia lata united with fibrous offsets of the extensor and flexor muscles. It covers the anterior and the exter- nal lateral ligament, being inserted below into the heads of the tibia and fibula ; and it blends on the inner side with the internal lateral ligament. It is not closely applied to the synovial membrane, but it is united below with the interarticular fibro-cartilages. Dissection. Four external ligaments, anterior and posterior, internal and external, are situate at opposite points of the articulation. The poste- rior and the internal lateral ligament will appear on the removal of the areolar tissue from their surfaces ; but the anterior and the external lateral are covered by the aponeurosis on the fore part of the joint, and will not be laid bare till this has been cut through. If there is a second external lateral band present, it is not concealed by the aponeurosis. The external lateral ligament (fig. 216, is round and cord-like. It is attached to the outer condyle of the femur below the tendon of the gas- LIGAMENTS OF KNEE. 635 trocnemius, and descends vertically between two pieces of the tendon of the biceps to a depression on the upper and outer part of the head of tlie fibula. Beneath the ligament are the tendon of the popliteus, and the external lower articular vessels and nerve. Fig. 216. Fig. 217. External Ligament of the Knee-joint. (Bourgery). 1. Anterior ligament. 2. External lateral ligament. 8. Interosseous ligament. 4. Part of the capsule. Internal Ligament of the Knee-joint. (Bourgery.) 1. Tendon of the extensor muscle ending below in the ligament of the patella, 2. 3. Internal lateral ligament. 4. Lateral part of the capsule. A second fasciculus is sometimes present behind the other, but it is not attached to the femur: it is connected above with the gastrocnemius, and below with the posterior prominence of the head of the fibula. Tlie tendon of the biceps is inserted by two pieces into the points on the head of the fibula ; and from the anterior of these there is a prolonga- tion to the head of the tibia. The external lateral ligament passes be- tween the pieces into which the tendon is split. The tendon of t\\Q popliteus may be followed by dividing the posterior ligament. It arises from the fore part of the oblong depression on the outer surface of the external condyle of the femur. In its course to the outside of the joint, it crosses the external semilunar fibro-cartilage and the upper tibio-peroneal articulation. When the joint is bent, the tendon lies in the hollow on the condyle ; but slips out of that groove when the limb is extended. The tendon of the adductor magnus is inserted into a tubercle on the internal condyle of the femur, above the attachment of the internal lateral ligament. The internal lateral ligament (fig. 217,^) is attached to the condyle of the femur, where it blends with the capsule ; but becoming thicker beloAv, and separate from the rest of the capsule, it is fixed for about an inch into the inner surface of the tibia, below the level of the ligamentum patellae. The tendons of the sartorius, gracilis, and semitendinosus muscles lie over the ligament ; and the tendon of the semimembranosus, and the internal lower articular vessels and nerve are beneath it. To the posterior edge some fibres of the tendon of the semimembranosus are added. 636 DISSECTION OF THE LEG. The tendon of the semimembranosus muscle is inserted beneath the internal lateral ligament into an impression at the back of the inner tuber- osity of the head of the tibia: between it and the bone is a synovial bursa. The tendon sends some fibres to the internal lateral ligament, a prolongation to join the fascia on the popliteus muscle, and another to the posterior ligament of the knee joint. posterior ligament (ligament of Winslow), wide and membranous, covers the back of the joint between the two lateral, and is joined by fibres from the tendon of the semimembranosus, which are directed across the joint to the outer side. It is fixed below to the head of the tibia behind the articular surface, and above to the femur, but by strongest fibres opposite the intercondyloid notch. Numerous apertures exist in it for the passage of the vessels and nerves to the interior of the articulation ; and the tendon of the popliteus pierces it. The anterior ligament (ligamentum patellae) (fig. 217,^), part of the tendon of insertion of the extensor muscle of the knee (p. 571), is two inches long. Superiorly it is attached to the lower part of the patella, and to the depression on the inner surface of the apex ; and inferiorly it is inserted into the tubercle of the head of the tibia, and into an inch of the bone below it. An expansion of the triceps extensor covers it ; and a bursa intervenes between it and the top of the tubercle of the tibia. Dissection (fig. 218). To see the reflections of the synovial membrane raise the knee on blocks, and open the joint by an incision on each side, Fig. 218. The Capsule of the Knee-joint cut across, and the Patella thrown down to show the NAMED Folds of the Synovial Sac. a. Mucous ligament. 6. Internal, and c, external alar ligament. above the pabdla. When the anterior part of the capsule with the patella is thrown down, a fold (mucous ligament) will be seen extending from the intercondyloid fossa of the femur to a mass of fat below the patella. On each side of the knee-pan is a similar fold (alar ligament) over some fat. The limb may be laid flat on the table, and some of the posterior liga- SYNOVIAL SAC AND FAT ABOUND KNEE. 637 merit may be removed, to show the pouches of the synovial membrane which project behind over the condyles of the femur ; but the limb is to be replaced in the former position before the parts are learnt. The synovial membrane (fig. 218) lines the interior of the capsule, and is continued to the articular ends of the bones. It invests the interarticular cartilages after the manner of serous membranes, and sends a pouch be- tween the tendon of the popliteus and the exteimal fibro-cartilage and the head of the tibia ; it is also reflected over the strong crucial ligaments at the back of the joint. There are three named folds of the synovial membrane. One in the centre of the joint is the mucous ligament (ce), which contains small ves- sels and some fat, and extends from the interval between the condyles to the fat below the patella. Below and on each side of the patella is another fold — alar ligament (h and c), which is continuous with the former below the patella, and is placed over a mass of fat : the inner (5) is prolonged farther than the outer by a semilunar piece of the serous membrane. At the back and front of the articulation pouches are prolonged beneath the tendons of muscles. Beliind there are two, one on each side, between the condyle of the femur and the tendinous head of the gastrocnemius. On the front, the sac projects under the extensor muscle one inch above the articular surface ; and if it communicates with the bursa in tliat situa- tion, it will reach tw^o inches above the joint surface of the femur. When the joint is bent there is a greater length of the serous sac above the patella. Fat around the joint. Two large masses are placed above and beloAV the patella, and some fat is located around the crucial ligaments. The infra-patellar mass, the largest of all, fills the interval between the patella with its ligament and the head of the tibia, and gives origin to the ridges of the synovial membrane. From it a piece is continued around the patella : but it is larger at the inner margin of the bone, than on the outer, and overhangs the inner perpendicular facet. During extension of the joint the infra-patellar pad is applied to, and lubricates the articular surfaces of the femur. The supra-patellar pad is interposed between the triceps extensor and the femur around the top of the synovial sac, and is greater on the outer than on the inner side. Dissection (fig. 219). The ligamentous structures within the capsule will be brought into view, whilst the limb is still in the same position, by throwing down the patella and its ligament, and clearing away the fat behind it. In this step the student must be careful of a small transverse band which connects anteriorly the interarticular cartilages. The remains of the capsule and other ligaments, and the synovial mem- brane are next to be cleared away from the front and back of the crucial ligaments, and from the interarticular cartilages. Whilst cleaning the ^posterior crucial the limb is to be placed flat on the table with the patella down ; and the student is to be careful of a band before it from the exter- nal fibro-cartilage, or of two bands, one before and the other behind it. Ligaments loithin the cay side. The ligamentous structures within the capsule consist of the central crucial ligaments, and of two plates of fibro- cartilage on the head of the tibia. The crucial ligaments (fig. 219) are two strong fibrous cords between the ends of the tibia and femur, which maintain in contact the bones. They cross one another somewhat like the legs of the letter X, and have 638 DISSECTION OF THE LEG. received their name from that circumstance. One is much anterior to the other at the attachment to the tibia. The anterior ligament (/) is most oblique in its direction, and is smaller than the posterior. Inferiorly it is attached in front of the spine of the tibia, close to the inner articular surface, reaching back to tlie inner point of the spine: superiorly it is inserted by its posterior shorter fibres into the back of the outer condyle of the femur, and by tlie anterior or longer into the hinder part of the intercondyloid fossa. 'posterior ligament (e) is almost vertical between the bones at the back of the joint. By the lower end it is fixed to the hindermost impres- sion of the hollow behind tlie spine of the tibia, near the margin of the bone; and above its posterior shorter fibres are in- serted into the inner condyle along the side of the oblique curve, whilst the anterior and longer reach the fore part of the inter- condyloid fossa. Tlie use of these ligaments in the move- ments of the joint, after the external liga- ments have been cut through may now be studied. As long as both ligaments are whole the bones cannot be separated from each other. Rotation in of the tibia is stopped by the anterior crucial. Rotation out is not checked by either ligament ; for the bands uncross in the execution of the movement, and will permit the tibia to be put hind foremost. Supposing the tibia to move, as in straightening the limb, the anterior pre- vents that bone being carried too far for- wards by the extensor tendon, or by force ; and the ligament is brought into action at the end of extension, because the tibia is being put in front of the femur. Its use is shown by cutting it across, and leaving the posterior entire, as then the tibial articulat- ing surfaces can be placed in front of the femoral in the half bent state of’ the joint. The posterior crucial arrests the too great movements backwards of the tibia by the flexors or by force ; and it is stretched in extreme flexion, in which the tibia is being drawn back from the femur. This use will be exemplifled by cutting across the posterior (in another joint or in another dissection) and leaving entire the anterior: when this has been done the articular surfaces of the tibia can be carried nearly altogether behind the condyles of the femur. The inter articular or semilunar Jibro-cartilages (fig. 220) cover partly on each side the articular surface of the tibia. They are thick at the outer margin, where they are united by fibres to the ca[)sule, and are thin at the inner edge ; they are hollowed on the upper surface, so as to assist in giving depth to the fossae for the reception Fig. 219. Intekarticular Ligaments of the Knee-Joint. a. Internal, and b. External semilunar fibro-cartilage ; the latter rather displaced by the bending of the joint, e. Posterior crucial ligament, with (f, the ascending ligamentous band of the external fibro-cartilage. /. Anterior crucial ligament. g. Patellar surface of the femur. INTRA-OAPSULAR LIGAMENTS OF KNEE. 639 of the condyles of the femur, but are flattened below. Inserted into the tibia at their extremities, they are coarsely fibrous at their attachment to the bone, like the crucial ligaments ; and they become cartilaginous only where they lie between the articular surfaces. The synovial membrane is reflected over them. The internal cartilage (a) is ovoid in form, and is a segment of a larger circle than the external. In front it is attached by a pointed part to the anterior margin of the head of the tibia, in front of the anterior crucial liga- ment. At the back, where it is much wider, it is fixed to the inner lip of the hollow behind the spine of the tibia, between the attachment of the other cartilage and the posterior crucial liga- ment. The external cartilage (6) is nearly circular in form, and is connected to the bone within the points of attach- ment of its fellow. Its anterior part is fixed in front of the spine of the tibia, close to the outer articular surface, and opposite the anterior crucial ligament, which it touches ; and its posterior extremity is inserted behind and be- tween the two osseous points of the spine. This fibro-cartilage is less closely united to the capsule than the internal, for the fore part is in the cen- tre of the joint, and the tendon of the popliteus muscle separates it behind from that membrane. The outer fibro-cartilage is provided with two accessory bands, one at the fore part, the other behind. The anterior or transverse ligament (c) is a narrow band of fibres be- tween the semilunar cartilages at the front of the joint. Sometimes it is scarcely perceptible. The posterior or ascendij^g band (c?), thicker and stronger than the other, springs from the back of the outer fibro-cartilage, and is inserted into the femur as a single band (fig. 219, d) in front of the posterior crucial, or as two bands — one being before, and the other behind that ligament. Use. The fibro-cartilages deepen the sockets of the tibia for the recep- tion of the condyles of the femur, and fill the interval between the articu- lar surfaces of the bones at the circumference of the joint ; they moderate the injurious effect of pressure of the one bone on the other ; and cause the force of shocks to be diminished in transmission. In flexion and extension they move forwards and backwards with the tibia. During flexion they recede somewhat from the fore part of the joint, and surround the condyles of the femur ; but in extension they are flattened out on the surface of the tibia. Of the two cartilages the ex- ternal moves the most in consequence of its ends being less attached to the capsule. Fig. 220. View of the He\d of the Tibia with THE FiBRO CARTILAGES ATTACHED ; THE CRUCIAL LIGAMENTS HAVE BEEN CUT THROUGH. a. Inner, and b, outer semilunar flbro-car- tilage. c. Transverse, and d, ascending or poste- rior band (cut) of tke external carti- lage. e. Posterior, and /, anterior crucial liga- ment. 640 DISSECTION OF THE LEG. In rotation the fibro-cartilages follow the tibial movements, but the ex- ternal is most displaced by the projecting outer condyle of the femur. The accessory bands in front and behind serve to retain in place the least fixed external fibro-cartilage ; thus the anterior ligament keeps for- wards the fore part of that cartilage in fiexion, and the posterior secures the back of the same from displacement in rotation. Articular surfaces of the hones. The end of the femur is marked by a patellar and two tibial surfaces. The patellar is placed in the middle line above the others ; it is hol- lowed along the centre, with a slanting surface on each side, the outer being the larger of the two. The surfaces for contact with the tibia, two in number, occupy the ends of the condyles, and are separated from the patellar impression by an oblique groove on each side. On the centre of each is a somewhat flat- tened part, which is in contact with the tibia in standing ; and at the posterior third is a more convex portion, which touches the tibia in rota- tion. The inner condyle of the femur is curved at its anterior third, the con- cavity being directed out : this has been named the “oblique curvature.” Close to the curved part is a semilunar facet, which touches the perpen- dicular surface of the patella in extreme flexion. On the head of the tibia are two sHoflit articular hollows, the inner beino; the deeper and larger, which rise towards the middle of the bone, on the points of the tibial spine. The joint-surface of the patella is marked by the following impressions. Close to the inner edge is a narrow perpendicular facet, and along the lower border is a similar transverse mark. Occupying the rest of the bone is a squarish surface, which is subdivided by a vertical and a trans- verse line into two pairs of marks — upper and lower. (Goodsir, Edinb. Med. Jour., 1855.) Movements of the joint. The chief movements of the knee are two in number, bending and straightening, like the elbow ; but there is, in addi- tion, rotation of the tibia when the joint is bent. Flexion and extension. Each of these movements may be divided into stages for the purpose of particularizing changes in its direction. Inflexion the tibia with its fibro-cartilages moves backwards round the end of the femur ; and its extent is limited by the extensor muscle, and by the meeting of the calf of the leg with the thigh. For the anterior third of the movement the tibia is directed down and in along the oblique curve of the inner condyle, giving rise to rotation inwards of that bone ; but for the posterior two-thirds, the tibia passes straight back over the condyles. All the external ligaments are relaxed, except the anterior ; and both crucials are put on the stretch towards the end of flexion. In extension the tibia is carried forwards until it comes into a straight line with the femur, when the uniting ligaments prevent its farther progress. In the hinder two-thirds of the movement the tibia has a straight course over the condyles of the femur; but in the anterior third the leg- bone is directed up and out over the oblique curve of the inner condyle, and is rotated out. All the external ligaments except the anterior are tightened, and the crucial cords help to limit extreme extension. MOVEME^QTS OF KNEE AND PATELLA. 641 Rotation. A half bent state of the knee is necessary for this movement, for the purpose of relaxing the anterior crucial and the external ligaments ; and the foot must be free. Then, the tibia with its fibro-cartilages rotates around a vertical axis, the great toe being turned in and out. During rotation in the inner articular surface of the tibia touches the condyle of the femur and moves backwards ; and the outer articular sur- face, separated by a slight interval from the thigh bone, passes forwards. Both lateral ligaments are loose ; but the anterior crucial is gradually tightened, and stops finally the motion. In rotation out the opposite mov^ement of the tibia takes place — the in- ner articular surface being directed forwards, and the outer backwards. The internal lateral ligament controls the movement by its fibres being made tense. The crucials have not any influence on the motion (p. 637). Movement of the 'patella. When the knee passes from flexion to exten- sion the })atella crosses it obliquely from the outer to the inner side, touch- ing in succession different parts of the femoral articular surfaces. In complete flexion the knee-pan lies on the outer side of the joint below the femur, where it is scarcely perceptible, and is fixed in its situa- tion. It touches the semilunar surface on the inner condyle by its per- j)endicular facet, and the under part of the outer condyle by the upper and outer mark on its square surface. When the joint is passing from flexion to extension, the upper pair of impressions on the square surface of the patella, and the lower pair rests successively on the pulley-surface of the femur. In complete extension, the patella is situate at the upper and inner part of the knee-joint, Avhere it is very prominent, with its apex and the ligament of the patella directed down and out to the tibia. For the most part the knee-pan articular surface is raised above the trochlea of the femur, which it touches only at the upper edge by its lower trans- verse facet. Pekoxeo-tibial articulations. The tibia and fibula are united by ligamentous bands at the extremities, where they touch ; and by an inter- osseous ligament between the shafts of the bones. Dissection. The muscles are to be taken away from the front and back of the interosseous ligament ; and the loose tissue is to be removed from a small band in front of, and behind the upper and lower ends of the tibia and fibula. The UPPER ARTICULATION has very small movement, and the structures between the ends of the bones are two small bands, anterior and posterior. The anterior ligament extends over the joint from the outer tuberosity of the tibia to the head of the fibula. The posterior ligament, thinner than the anterior, is attached to the bones behind the joint : it is covered by the tendon of the popliteus muscle and a prolongation of the synovial membrane of the knee-joint. The articular surfaces are covered with cartilage : and a synovial mem- hrane lining the articulation projects backwards so as to touch that of the knee-joint. The LOAVER ARTICULATION possesses an anterior and a posterior band, together Avith an inferior ligament between the ends of the bones. The anterior ligament reaches obliquely from the loAver end of the tibia to the fibula ; and the posterior has attachments behind the articulation similar to those of the band in front. The inferior ligament closes the space betAveen the contiguous ends of 41 642 DISSECTION OF THE LEG. the tibiii and fibula, and consists of transverse yellowish fibres distinct from the posterior ligament. It is fixed on one side to the end of the fibula above the pit : and on the other it is inserted into the contiguous part of the tibia, and into the posterior edge of the articular surface so as to assist in deepening the hollow into which the astragalus is received. The interosseous ligament fills the interval between the bones of the leg, and serves as an aponeurotic partition between the muscles on the front and back of the leg. Its fibres are directed downwards for the most part from the tibia to the inner surface of the fibula : but some few cross in the opposite direction. Internally it is fixed to the outer edge of the tibia : and externally, to the oblique line on the inner surface of the fibula along the upper three- fourths, but to the posterior border along the lower fourth of that bone. Both superiorly and inferiorly is an aperture which transmits vessels. The upper opening, about an inch in length, lies along the neck of the fibula, and gives passage to the anterior tibial vessels. Tlie lower aper- ture is close to the fibula, about an inch above the lower end, and is only large enough for the small anterior peroneal vessels. Some strong irregular bundles of fibres, the inferior interosseous liga- ment, extend between the bones below the aperture for the anterior pero- neal artery. It may be seen after tlie examination of the ankle joint by savving longitudinally the lower ends of the leg bones. Movement. Very little movement is allowed in the tibio-peroneal articu- lations, as the chief use of the fibula is to give security to the ankle joint and attachment to muscles of the leg. In the upper joint there is a slight gliding from before back. In the lower articulation the ligaments permit some yielding of the fibula to the pressure of the astragalus, as when the weight of the body is thrown on the inner side of the foot ; but if the force is violent the lower fourth of that bone will be fractured sooner Fig. 221. than the ligaments. fNTEKNAL LATERAL LIGAMENT OF THE AnKLE (altered from Bourgery). 1. Posterior piece. 2. Middle piece. S. Anterior piece of the inner ligament. 4. Inferior calcaneo-scaphoid ligament. Articulation of the ankle (fig. 221). Like the knee, the ankle is a ginglymoid or hinge joint. In this joint the upper surface of the astragalus is received into an arch formed by the lower ends of the tibia and fibula ; and the four liga- ments belonging to this kind of articulation connect together the bones. Dissection. To make the dissec- tion required for the ligaments of the ankle joint, the muscles, and the fibrous tissue and vessels must be removed from the front and back of the articulation. For the purpose of defining the lateral ligaments, the limb must be placed first on one side and then on the other. Tlie internal ligament is wide and strong, and lies beneatli the tendon of the tibialis posticus. LIGAMENTS OF ANKLE-JOINT. 643 Tlie external is divided into three separate pieces ; and to find these the peronei muscles, and the remains of the annular ligament below the outer malleolus, should be taken away. Tlie anterior or tibio-tarsal ligament is a thin fibrous membrane, which is attached to the tibia close to the articular surface ; and to the upper part of tlie astragalus near the articulation with the scaphoid bone. In the ligament are some rounded intervals and apertures for vessels. On the sides it joins the lateral ligaments. The posterior ligament is thinner internally than externally ; and it is inserted into the tibia and the astragalus, close to the articular surfaces of the bones. Towards the outer part it consists of transverse fibres, which are fixed into the hollow on the inner surface of the external malleolus. The internal lateral or deltoid ligament (fig. 221) is attached by its upper or pointed part to the inner malleolus, and by its base to the astraga- lus, the os calcis, and the scaphoid bone, by fibres which radiate to their insertion in this manner : — The posterior Q') are directed to the hinder part of the inner surface of the astragalus ; the middle (^) pass vertically to the sustentaculum tali of the os calcis ; and the anterior (''^), which are thin and oblique, join the inferior calcaneo-scaphoid ligament and the inner side of the scaphoid bone. The tendons of the tibialis posticus and flexor longus digitorum are in contact with this ligament. The external lateral ligament (fig. 222) consists of three separate pieces, anterior, middle, and posterior, which are attached to the astragalus and the os calcis. The anterior piece (') is a short fiat band, which is directed from the foi'e part of the malleolus to the side of the astragalus in front of the lateral articular surface. The middle portion (^) is flattened and de- scends from the tip of the malleolus to the outer surface of the os calcis, about the middle. The posterior ('^) is the strongest, and is almost hori- zontal in direction ; it is connected externally to the pit on tlie inner sur- face of tlie malleolus, and is inserted into the posterior part of tlie astraga- lus behind the upper articular surface, extending to the groove for the flexor pollicis tendon. The posterior and middle fasciculi are placed beneath the peronei mus- cles. The middle part is but slightly in contact above with the synovial membrane of the ankle joint; and both it and the posterior piece touch the synovial membrane between the astragalus and the os calcis. Dissection. Dividing the ligaments of the ankle joint, separate the as- tragalus from the bones of the leg, to see the osseous surfaces entering into the joint. The synovial membrane of the joint lines the capsule, and is simple in its arrangement. Articular surfaces. On the tibia there are two articular faces, one of which corresponds with the end of the shaft, and the other with the mal- leolus. On the fibula the surface of the malleolus which is turned to the astragalus is tip[)ed with cartilage. The astragalus has a central articular surface, wider before than behind and ti'ochlear-shaped, wliich touches the end of the tibia : and on its sides are articular impressions for contact with the malleoli, but the outer one is the largest. Movement. Only the movements of flexion and extension are permitted in the ankle : in the former state the toes are raised towards the fore part of the leg ; and in the latter, they are pointed towards the ground. In flexion the astragalus moves backwards so as to project behind ; and 644 DISSECTION OF THE LEG. all furtlier motion is arrested by the meeting of the anterior edge of the tibia with that bone. The posterior ligament is stretched over the projecting head of the astragalus, and the posterior and middle parts of the external lateral, and the posterior piece of the internal lateral ligament, are made tense. In extension the astragalus moves forwards over the end of the tibia, and projects anteriorly. A limit to the movement is imposed by the meet- ing behind of the astragalus with the tibia. The lateral ligaments are partly made tight as in flexion, for instance the anterior piece of the external, and the fore and middle portions of the internal When the joint is half extended so that the small hinder part of the as- tragalus is brought into the arch of the leg bones, a slight movement of the foot inwards and outwards may be obtained ; but if the foot is forcibly extended the portions of the lateral ligaments, attached to the astragalus, prevent this lateral movement by their tightness. Dissection. The joints of the foot will be demonstrated by removing from both the dorsum and the sole all the soft parts which have been examined. Between the different tarsal bones bands of ligament extend, which will be defined by removing the areolar tissue from the intervals between them (fig. 223). It will be more advantageous for the student to clean all the ligaments before he proceeds to learn any, than to prepare only the bands of one articulation at a time. Articulation of the astragalus and os calcis. These bones are kept together by two joints, and a strong interosseous ligament ; and there are also thin bands at the outer side and behind. The 'posterior ligament (fig. 223, o) consists of a few fibres between the bones, where they are grooved by the tendon of the flexor pollicis ; and the external ligament (^) is connected to the sides of the astragalus and os calcis, near the middle piece of the external lateral ligament of the ankle joint. The interosseous ligament (fig. 223, c) consists of strong vertical and oblique fibres, which are attached above and below to the depressions on the contiguous surfaces of the two bones. This band extends across the bones, and its depth is greatest at the outer side. In a subsequent stage of the dissection (p. G47) articular surfaces will be seen between the bones, viz., one behind the interosseous ligament, and one in front of it, with two synovial membranes. Movement. Under the influence of the weight of the body, as in stand- ing, the astragalus moves down and in (not straight forwards) with External Lateral Ligament op the Ankle (altered from Bourgery). 1. Anterior part. 2. Posterior part. 3. Middle part of the outer ligament. 4. Interosseus of astragalus and os calcis. 5. External calcaueo-scaphoid ligament. LIGAMENTS OF TARSAL BONES. 645 flattening of the arch of the foot, so that its head projects against the calcaneo-scaphoid ligament. In this state the interosseous ligament is put on the stretch. Fig. 223. a. Posterior, ft, external, and e, in- terosseous ligaments between astragalus and os calcis. d. Astragalo-scaphoid. e. External calcaneo-scaphoid. /. Internal, and (j, upper calcaneo- cuboid ligaments. li. Dorsal scaplio-cuboid band, i. It, 1. Dorsal external, middle, and internal scapho-cuneiform longitudinal bands. n. Dorsal transverse bands between the cuneiform and cuboid bones. View op the Dorsal Ligaments of the Tarsus. When the pressure of the leg is removed the nstnigalus is carried up and out by the tightened ligaments and muscles, and the arch of the foot is restored. Astragalus with the scaphoid bone. The head of the astragalus is received into the hollow of the scaphoid bone, and is united to it by a dorsal ligament ; but the place of plantar and external lateral ligaments is supplied by strong bands between the os calcis and the scaphoid bone, which will be noticed below. The dorsal astragalo-scaphoid ligament (fig. 223, d) is attached to the astragalus close to the articulation, and to the dorsal surface of the sca- phoid bone : its attachments will be better seen when it is cut through. Dissection. The external ligament of the articulation may be seen on the dorsum of the foot in the hollow between the os calcis and the scaphoid bone. Supposing the tendon of the tibialis jiosticus removed, the inferior ligament will be defined in the sole of the foot by cutting some fibro-car- tilaginous substance from it. The inferior ligament (fig. 225, c) (calcaneo-scaphoid) is attached behind to the fore part of the sustentacnlum tali of the os calcis, and in front, to the hollow on the sustentaculum tali of the os calcis, and in front, to the hollow on the under surface of the scaphoid bone. In the upright posture of the body the tendon of the tibialis posticus is beneath it in the sole of the foot ; and on it the head of the astragalus rests. The external calcaneo-scaphoid (fig. 223, e) is placed outside the head of the astragalus, and serves as a lateral ligament to the astragalo-sca- ])hoid articulation ; it is about three-quarters of an inch deep. Behind, it is fixed to the upper part of the os calcis, between the articular surfaces for the cuboid bone and astragalus ; and in front it is inserted into the outer side of the os scaphoides. A synovial membrane serves for this articulation, and sends back a pro- longation to the joint between the fore part of the os calcis and the astra- galus. Articular surfaces. The head of the astragalus has two articular faces ; a smaller, below, for the os calcis ; and a larger one, elongated transversely 646 DISSECTION OF THE LEG. and larger externally than internally, for the scaphoid bone. The sca- phoid bone is hollowed, and is widest externally. Movement. The scaphoid moves down and in over the transversely elongated head of the astragalus, or up and out in the opposite direction. As the hone is forced downwards, the upper and external ligaments of the joint are made tight ; and when the scaphoid is moved in the opposite way the strong inferior ligament is put on the stretch. The os calcts avith the ceboid bone. The ligaments in this arti- culation are plantar and dorsal, the former being much the strongest ; and there is also an internal band. The dorsal ligament (fig. 223, g') (superior calcaneo-cuboid) is a rather thin fasciculus of fibres, which is attaclied near to the contiguous end of the os calcis and the cuboid bone ; it is sometimes divided into two parts, or it may be situate at the outer border of the foot. At the inner side of the os cuboides is a stronger internal hand (fig. 223, f) from the os calcis, this is fixed behind to the upper part of the os calcis external to the band to the scaphoid bone, and in front to the contiguous inner side of the os cuboides. Fig. 224. Plantar Ligaments of the Foot (Bourgery). 1. Long plantar ligament. 2. Deep portion of the inferior calcaneo-cu- boid ligament. 3. Tendon of the peroneus longus muscle. View of the Inferior Ligaments of the Tarsal Bones. a. Long plantar, cut. h. Short or deep inferior calcaneo-cuboid liga- ment. c. Inferior calcaneo-scaphoid. d. Plantar transverse scapho-cuboid ligament. e. Dorsal inner scapho-cuneiforrn extending into the sole of the foot. /. Plantar transverse ligament between the inner and middle cuneiform bones. g. Plantar transverse band between the cuboid and outer cuneiform. The in ferior calcaneo-cnhoid ligament in the sole of the foot (fig. 224) is much the strongest, and is divided into a superficial and a deep part : — TRANSVERSE TARSAL ARTICULATION. 647 The superficial portion, ligamentum longum playitce Q) is attached to the under surface of tlie os calcis from near the posterior to the anterior tubercle : its fibres pass forwards to be connected with the ridge on the under surface of the cuboid bone ; but the most internal are continued over the tendon of the peroneus longus muscle, assisting to form its sheath, and are inserted into the bases of the third and fourth metatarsal bones. The deep piece of the ligament (fig. 225, 5), seen on division of the superficial, extends from the tubercle and the hollow on the fore part of the under surface of the os calcis, to the cuboid bone internal or posterior to the ridge. A simple synovial membrane belongs to the articulation. Articular surfaces. Both bones are flattened towards the outer part of the articulation ; but at the inner side the os calcis is hollowed from above down, and the os cuboides is convex to fit into it. Movement. In this joint the cuboid bone possesses two movements, viz., an oblique one, down and in, and up and out. In the downward movement the internal lateral and the upper ligament are made tight ; and in the upward, the calcaneo-cuboid ligaments of the sole are stretched. Transverse tarsal articulation (fig. 223). The joints of the astragalus with the scaphoid, and os calcis with the cuboid bone, form a transverse articulation across the foot in which the movements of inversion and eversion take place. In inversion the great toe is adducted ; the inner border of the foot is shortened, and is raised from the ground so that the sole looks inwards. The scaphoid bone passes down and in over the head of the astragalus, being approximated near to the inner malleolus ; and the cuboid bone moves down and in on the os calcis. The cuneiform bones are raised at the same time and contribute to the movement (p. 648). The ligaments connected with both joints on the dorsum of the foot are tightened. In eversion the inner border of the foot descends and lengthens, the outer border is raised, and the great toe is abducted from the middle line of the body. The same two tarsal bones are directed up and out, and the cuneiforms sink. The ligaments in the sole of the foot of both joints now come into use to prevent over movement. Dissection. Saw through the astragalus in front of the attachment of the interosseous ligament between it and the os calcis; and remove the head of the bone for the purpose of observing the lower and outer calcaneo- scaphoid ligaments. Then the interosseous ligament uniting the astragalus and the os calcis is to be cut through, to demonstrate its attachments, the articular surfaces of the bones, and the synovial sacs (p. 644). Articular surfaces of the two hinder tarsal bones. There are two articular surfaces, anterior and posterior, to both the astragalus and the os calcis. The hinder one of the os calcis is convex transversely and the anterior is concave ; but sometimes the last is subdivided into two. The surface of the astragalus will have a form exactly the reverse of that of the os calcis, viz., the hinder one concave and the anterior convex ; the anterior is seated on the head of the astragalus. 648 DISSECTION OF THE LEG. Dissection. The calcaneo-cuboid joint may be opened to see the articu- lar surfaces: and the student is to keep in mind that all the other articula- tions of the foot are to be opened for the like purpose, even should directions not be given. Articulations of the scaphoid bone. The scaphoid bone articu- lates in front with the three cuneiform bones, and laterally with the os cuboides. In the articulation Avith the cuneiform hones (fig. 223) there are three longitudinal dorsal ligaments (f, /i^, /), one to each bone ; but the inner- most is the strongest and widest, and extends round the inside of the articulation into the sole of the foot (fig. 225, e). The place of -plantar bands is supplied by processes of the tendon of the tibialis posticus. A synovial membrane (common of the tarsus) lines the articulation, and sends forwards prolongation betAveen the cuneiform bones. In the articulation Avith the os cuboides there is a dorsal oblique band of fibres (fig. 223, li) between the contiguous surfaces of the bones ; a plantar transverse band (fig. 225, c?), Avhich is concealed by the tendon of the tibialis posticus ; and a strong interosseous ligament. Where the bones touch, the surfaces are tipped with cartilage, and are furnished Avith a prolongation from the common synovial ynembrane of the tarsus. Articulatoins of the cuneiform bones. These bones are united to one another by cross bands ; and the external one articulates Avith the os cuboides after a similar manner. The three cuneiform bones are connected together by short transverse dorsal bands (fig. 223, ii) betAveen the upper surfaces. Similar plantar ligaments are wanting, except one between the two innermost (fig. 225,/). There are also interosseous ligaments between the contiguous surfaces of the bones. Laterally there are articular surfaces betAveen the bones, Avith offsets of the common synovial membrane. Where the external cuneiform touches the cuboid bone the surfaces are covered Avith cartilage. A dorsal ligament (fig. 223, n) passes transversely betAveen the tAvo ; and a plantar ligament (fig. 225, g') takes a similar direction. Betvv'een the bones there is also an interosseous ligament. This joint is furnished eitlier Avith a distinct synovial sac, or Avith a prolongation of the common tarsal synovial membrane. Tlie synovial membrane of tlie articulations of the cuneiform bones is common to many of the bones of the tarsus. Placed between the scaphoid and the three cuneiforms it sends one prolongation forwards between the inner and middle cuneiform to the joints Avith the second and third meta- tarsal bones ; another, outwards, to the articulation of the scaphoid with tlie cuboid bone ; and sometimes a third to the joint betAveen the external cuneiform and tlie os cuboides. Articular surfaces. On the scaphoid are three articular faces, the inner being rounded, and the other tAvo flattened. The three cuneiforms unite in a shalloAv ellijitical hollow, Avhich is most excaA^ated internally. Movement. The cuneiform bones glide up and out on the scaphoid in inversion of the foot, and down and in in eversion ; and the inner one moves more than the others in consequence of the shape of the articular surfaces, and the attachment to it of the tibialis anticus. When the bones [lass doAvn the dorsal ligaments are made tight : and LIGAMENTS OF TAESUS WITH METATARSUS. 649 as tliey rise the interosseous and transverse plantar bands will keep them united. In standing and in progression these bones are separated somewhat from each other with diminution of the arch of the foot, and stretching of the transverse ligaments which connect them. Articulation of the mktatarsal bones. The bases of the four outer metatarsal bones are connected together by dorsal, plantar, and in- terosseous ligaments ; and where their lateral parts touch, they are covered with cartilage, and have offsets of a synovial sac. The dorsal ligaments (fig. 22 G) are small trans- verse bands from the base of one metatarsal bone to the next. The ligaments (fig. 224) are similar to the dorsal. The interosseons ligaments are short, transverse fibres between the contiguous rough lateral surfaces : they may be afterwards seen by forcibly separating the bones. Lateral union. The four outer bones touch one another laterally ; the second metatarsal lies against the internal and external cuneiforms ; and the fourth is in contact internally with the outer cunei- form. Those articulating surfaces are covered with cartilage ; and are provided with synovial mem- brane, which is derived from the sacs serving for the articulation of the same four metatarsal with the tarsal bones. The metatarsal bone of the great toe, like that of the thumb, is not united to the others at its base by any intervening bands. The digital ends of the five metatarsal bones are united by the transverse metatarsal ligament ; this has been described in page 624. Tarsal with metatarsal bones. These articulations resemble the like parts in the hand, as there is a separate joint for the great toe, and a common one for the four outer metatarsals. Articulation of the great toe. Tlie articular ends of the bones are in- cased by a capsule, and are provided with an upper and a lower longitu- dinal hand to give strengtli to the joint : the lower band is placed between prolongations from the tendons of the tibialis anticus and peroneus longus. A simple synovial membrane serves for the articulation. The articular surfaces are oval from above down, curved inwards, and constricted in the middle ; tliat of the great toe is excavated, and the other is convex. Movement. There is an oblique movement of the metatarsal bone down and in and up and out, like that of the internal cuneiform with the sca- phoid bone ; and this will contribute some motion to inversion and ever- sion of the foot. The joint possesses likewise slight abductory and adductory movement. Articulation of the four outer toes. The three outei* tarsal bones of the last row correspond with four metatarsals ; — the middle cuneiform be- ing opposite the second metatarsal bone, the external cuneiform touching that of the third toe, and the os cuboides carrying the two outer bones. Dorsal Ligaments Uni- ting THE Tarsus to the Metatarsus, and the Me- tatarsal Bones to each OTHER BEHIND (Bourgevy) . 650 DISSECTION OF THE LEG. The bones in contact are tipped with cartilage, and have longitudinal dor- sal, plantar, and lateral ligaments, with some oblique in the sole. The dorsal ligaments (fig. 22G) are thin bands of fibres, which are more or less longitudinal as they extend from the tarsal to tlie metatarsal bones. Each metatarsal bone receives one ligament, except that of the second toe, to which there are three ; — the three bands to the second coming from all the cuneiform bones, one from each. The third bone obtains a liga- ment from the external cuneiform : and the fourth and fifth have a fascicu- lus to each from the os cuboides. Plantar ligaments (fig. 224). There is one longitudinal bamd ^rom each of the two outer cuneiform to the corresponding metatarsal bone ; but be- tween the cuboid and its metatarsal bones there are only some scattered fibres. The lateral ligaments are longitudinal ; they lie deeply between the bones, and are connected with the second and tliird metatarsals : they will be better seen by cutting the transverse bands joining tlie bases of the bones. To the bone of the second toe there are two bands, one on each side : — the inner is strong and is attached to the internal cuneiform ; and the outer is fixed into the middle or the outer cuneiform bone. The me- tatarsal bone of the third toe is provided with one lateral slip on its outer side, which is inserted above into the external cuneiform bone. Oblique 'plantar ligaments, A fasiculus of fibres extends across from the front of the internal cuneiform to the second and third metatarsals ; and from the external cuneiform there is another slip to the metatarsal bone of the little toe. Line of the articidation. The line of the articulation between the tarsus and metatarsus is zigzag, in consequence of the unequal lengths of the cuneiform bones. To open the articulation, the knife should be carried obliquely forwards from the tuberosity of the fifth to the base of the sec- ond metatarsal bone ; then about two lines farther back for the union of the second metatarsal with the middle cuneiform ; and finally, half an inch in front of tl)e last articulation, for the joint of the internal cunei- form with the first metatarsal bone. Two synovial membranes are present in these tarso-metatarsal articula- tions. There is one between tlie cuboid and the two outer metatarsals, which serves for the adjacent lateral articular surfaces of the bones ; this is not always separate from the following. The second is placed in the joint between the external and middle cuneiforms with their metatarsal bones (third and second), and is an offset of the common synovial membrane belonging to the articulation of the scaphoid with the cuneiform bones (p. G48) : prolongations from it are furnished to the lateral articular surfaces of the second, third, and fourth (inner side) metatarsals. Articular surfaces. The osseous surfaces are not flat; for the metatar- sal bones are undulating, and the tarsal are uneven to fit into the others. Movement. F roni the wedge-shaped form of the metatarsal bones a slight movement from above down is obtainable ; and this is greatest in the little toe and the next. In the little toe there is an abductory and adductory motion ; and a small degree of the same exists in the fourth toe. Dissection. All the su})erficial ligaments having been taken away, the interosseous ligaments of the tarsus and metatarsus may be seen by sepa- METATAESO-PIIALANGEAL JOINTS. 651 ratino; forcibly the cuneiform bones from one another and from tlie os cuboides; the latter bone from the os scaphoides : and the bases of the metatarsals from one another. The dissector will find that, in using force, the bones will sometimes tear sooner than the ligaments. Metatarsus with phalanges. These are condyloid joints, in which the head of the metatarsal bone is received into the cavity of the phalanx. Each articulation has two lateral and an inferior ligament^ as in the hand; and the joint is further strengthened above by an expansion derived from the tendons of the extensors of the toes. A distinct synovial mem- brane exists in each joint. In the articulation of the great toe there are two sesamoid bones, which are connected with the inferior and lateral ligaments. All th(‘se structures are better seen in the hand, where they are more distinct; and their anatomy is more fully described with the dissection of that part. (See page oOl.) Surfaces of hone. The metatarsal bone has a rounded head, which is longest from above down, and readiest farthest on the plantar surface. On the end of the phalanx is a cuji-shaped cavity. Movement. In this condyloid joint as in the hand, there is angular motion in four different directions, with circumduction. Flexion and extension. When the joint is bent the phalanx passes un- der the head of the metatarsal bone; and when it is extended the phalanx moves back beyond a straight line witli the metatarsal bone. A limit to flexion is set by the meeting of the bones, by the stretching of the fore part of the lateral ligaments, and by the extensor tendon ; and to extension, by the tightness of the inferior, and the hinder part of each lateral ligament, and by the flexor tendons. Lateral movement. The phalanx passes from side to side across the end of the metatarsal bone. Its motion is checked by the lateral ligament of the side from which it moved, and by the contact witli the other digits. Circumduction., or the revolving of the phalanx over the rounded head of the metatarsal bone, is least impeded in the great toe joint ; but these movements in the foot are not so free as in the hand. Articulations of the phalanges. There are two phalangeal joints to each toe, except the first. Ligaments similar to those in the metatarso-phalangeal joints, viz., two lateral and an inferior, are to be recognized in these articulations. The joint between the last two phalanges is least distinct ; and oftentimes the small bones are immovably united by osseous substance. These ligaments receive a more particular notice with the dissection of the hand (p. 302). A simple synovial membrane exists in each })halangeal articulation. Articular surfaces. In both phalangeal joints, the nearest phalanx presents a trochlear surface ; and the distal one is marked by two lateral hollows or cups with a median ridge. Movement. Only flexion and extension are permitted in the two pha- langeal joints of the toes, as in the hand. In flexion the farther phalanx glides under the nearer; and in extension the two are brought into a straight line. The bending is checked by the lateral ligaments and the extensor ten- don ; and the straightening is limited by the inferior ligament and the flexor tendons. The Femoral Artery gives off 652 ARTERIES OF THE LOWER LIMB TABLE OF THE ARTERIES OF THE LOWER LIMB. f External pudic superficial epi- gastric superflcial cir- ciunfiex iliac Profunda . Muscular Anastomotic Superior inferior. f External circumflex Ascending descending transverse. r Muscular internal circumflex ^ . L transverse . . [ branches. first perforating second perforating third perforating L terminal branch. Superficial deep branch. f Muscular upper internal upper external lower internal lower external azygos articular sural. Arterior tibial . Popliteal . . L Posterior tibial articular articular f Recurrent cutaneous muscular internal malleolar external malleolar articular tarsal n,e,atarsal. . | ‘'“Te first interosseous communicating to deep arch ,, 3 To great toe and aiouai . . . . < r Peroneal . nutritious to tibia communicating to peroneal ^ articular Muscular nutritious to fibula anterior peroneal. internal plantar external plantar . . f Muscular plantar arch ■1 Muscular posterior perfor- ating digital, for three toes and a half anterior perfor- ating. N.B. The branches of the internal iliac artery which end in the limb, will be found in the table of the arteries of the abdomen. The Femoral Vein, continued from the popliteal, receives f Popliteal . Anastomotic Muscular Profunda . Internal sa- l, phenous . VEINS OF THE LOWER LIMB. 653 TABLE OF THE VEINS OF THE LOWER LIMB. f External plantar -I ! 1 f Posterior tihial . internal plantar j articular communicatiug to saphenous nutritious L peroneal . .1 I Anterior tihial ' Communicating to deep arch. . interosseous rnetatai-sal . . . tarsal malleolar communicating to saphenous muscular L recurrent. External saphenous sural articular muscular. Branch from doi’- sal arch of foot, plantar veins from outer side of os calcis cutaneous in the leg. N Superficial ( deep branch. Terminal branch first perforating second perforating . Nutritious, third perforating • ^ ( Ascending External circumflex < transverse ( descening Internal circumflex J Muscular ( articular Muscular plantar- arch f Posterior per- I forating I digital from three toes and a half 1 anterior per- L forating. Anterior pero- neal muscular nutritious. Digital from great toe and half the next. Three interos- seous. Branch from dorsal arch of the foot plantar veins about os calcis communicating with postei-ior and ante- rior tibial « communicating with deep veins of thigh cutaneous from outer and inner parts of thigh external pudic superficial epigastric superficial circumflex iliac. Nerves of the Sacral Plexus in the Limb. Nerves of the Lumbar Plexus in the Limb. 654 NERVES OF THE LOWER LIMB 1. External cutaneous 2. Obturator 3. Anterior crural j 4. Branch 1 of geiiito- L crural . 1. Small sciatic 2. Great sciatic . 3. To gluteus 4. To qua- drat us and gemelli . , 5. Superior ^ gluteal TABLE OF THE NERVES OF THE LOAVER LIMB. ( Posterior aud < anterior ( branches. f f to obturator trunk Accessory . < to pectiueus ( to hip joint. to obturator externus to articulation superficial division . ^ To gracilis ( to abductor longus to plexus in the thigh aud artery Muscular deep divi- sion . . To adductor brevis and magnus articular. r Muscular ^ sartorius j J^l^^cular . ^ pectiueus. J middle cutaneous portion . 1 „ ,1 ) [ cutaneous { interior and inner branches. deep part L Muscular . internal saphenous f To rectus < to vastus externus — articular ( to vastus internus and crureus — articular. t Branch to plexus over patella to ^ leg and fot. f To integu- i meuts. { Inferior gluteal inferior pudendal cutaneous to gluteal region, thigh, and leg. f Articulation to hip to hamstrings. external popliteal ' Articular cutaneous peroneal communicating recurrent articular - musculo- J To peronei cutaneous ( cutaneous to foot and toes anterior tibial . Muscular articular cutaneous to two toes. internal popliteal Articular. f Articular muscular short saphenous f Muscular to flexors posterior tibial . internal plantar I I r 1 external plantar To glutei to tensor vaginte femoris Cutaneous of the sole muscular four digital communicating b'anch articular to the toes. Superficial part . . Muscular two digital arcicuiar deep part < Muscular i articular BALL OF THE EYE. 655 CHAPTEE X. DISSECTION OF THE EYE. The eyeball is the organ of vision, and is lodged in the orbit. Sup- ported in that hollow on a mass of fat, it is surrounded by muscles which impart movement to it ; and a thin membrane (tunica vaginalis oculi) isolates the ball, so as to allow free movement. Two lids protect the eye from external injury, and moderate the degree of light admitted into the interior ; and the anterior or exposed surface is covered by a mucous membrane (conjunctiva). Directions. In the absence of specimens of the human eye, the struc- ture may be learnt on the eye of the ox or pig. Let the student procure half a dozen eyes of the ox for the purpose of dissection. One or two shallow basins will be needed ; and some wax or tallow in the bottom of one, or in a deep plate, may be useful. Dissection. To see the general form of the ball of the eye, and the outer surface of the external coat, the attachments of the different muscles are to be taken away ; and the loose mucous membrane is to be removed from the front. The ball of the eye (fig. 227) is roundish in form and consists of two parts, which differ in aj)pearance, viz., an opaque posterior portion, form- ing five-sixths of the whole, and a smaller transparent piece (cornea) in front ; these two parts are segments of different-sized spheres, the an- terior belonging to the smaller sphere. To the back of the eye the optic nerve is attached, rather to the inner side of tlie axis of the ball ; and around it nutritive vessels and the nerves enter. The antero-posterior diameter of the ball amounts to nearly an inch (y^^ths), but the transverse measures an inch. The organ of vision is composed of central transparent parts, with in- closing membranes or coats. The coats, posited one within another, are named sclerotic, choroid, and retina. Tlie transparent media in the in- terior are likewise three, viz., the lens, the aqueous humor, and the vitreous body. Dissection. To obtain a general idea of the structures to be dissected, the student may destroy one eyeball by cutting through it circularly : he will then be able to recognize the arrangement of the parts mentioned above, with their strength and appearance : and will be better prepared to follow the directions that are afterwards given. F IBROUS COAT OF THE EYEBALL. The outcr Casing of the eye consists of an opaque hinder part called sclerotic, and of an anterior transparent portion, the cornea. The SCLEROTIC (cornea opaca) is the firm, whitish, and opaque portion of the external stratum of the eyeball, which supports the more delicate structures witliin. Dissection. To examine the inner and outer surfaces of this layer it will be necessary to cut circularly with a scissors through the cornea close 656 DISSECTION OF THE EYE. to the sclerotic, and to remove the cornea from the front of the eyeball ; on piercing the cornea the aqueous fluid escapes from the containing chamber. The outer structures may be then abstracted from the interior of the sclerotic covering, and may be set aside with the cornea for subse- quent use. Fig. 227. a. Outer or sclerotic coat, aud d, the cornea. h. Middle or choroidal coat. rn. Ciliary ligament. s. Ciliary process. e. Ciliary muscle, and/, iris. c. Inner c at of retina, continuous with the optic nerve behind, with a dark layer outside it. g. Lens. t. Suspensory ligament of the lens. h. Vitreous body. n. Hyaloid membrane. i. Posterior chamber. o. Canal of Petit r. Sinus circularis iridis. 1. Optic nerve. The dotted line thi-ough the centre is the longitudinal axis of the ball. Section of the Eyeball. The sclerotic tunic of the eye (fig. 227, a) is bell-shaped, and extends from the entrance of the optic nerve to the margin of the cornea, forming about five-sixths of the ball. At its back, and a little to the inner side of the centre (one-tenth of an inch), the optic nerve (T) is transmitted through an aperture in it: this opening decreases in size from without inwards, and is cribriform when the nerve is drawn out — the lattice-like condition being due to the bundles of fibrous tissue between the funiculi of the nerve. Small apertures for the passage of vessels and nerves are situate around the optic nerve ; and there are others for vessels at the front and centre of the ball. Anteriorly the sclerotic is continuous with the transparent cornea. On the outer surface this coat is smooth, except where the muscles are attached ; on the inner aspect it is of a dark color with flocculi of fine areolar tissue (membrana fusca) uniting it to the next coat, and with the ends of ruptured vessels and nerves. The sclerotic covering is thickest at the back of the eyeball, but it be- comes thinner and whiter about a quarter of an inch from the cornea, where it is visible as the “ white of the eye.” Where it joins the cornea it becomes again somewhat thickened. In its substance near the union with the cornea is a small flattened venous space, the canal of Schlemm (sinus circularis iridis) (fig. 23d, ’’). Structure. The sclerotic coat is formed of layers of white fibrous tissue, collected into bundles, with a tine network of yellow or elastic fibres. In STRUCTURE OF CORNEA. 657 Fio-. 228 it are scattered nucleated cells, fusiform in sliape, or possessing rays, and some with ])igment. Though interlaced with one another, the fibres have rather a longitudinal direction towards the back of the ball, and a trans- verse one at the outer surface near the cornea. Only a few vessels ramify in the rnembi’ane, and end in capillaries with large meshes. The presence of nerves in it is a subject for inquiry. Cornea (fig. 227, d). This firm transparent membrane (cornea pellu- cida) forms about one-sixth of the eyeball, and measures about half an inch transversely, but rather less from above down. Its shape is circular; though, when viewed in front, it appears largest in the transverse direc- tion, in consequence of the opaque sclerotic structure encroaching further on it above and below than on the sides. It is convex anteriorly, but concave posteriorly ; and it is of an inch in thickness. Its anterior is of rather less extent than its posterior surface. At the circumference it is thinned, and is blended with the sclerotic coat by continuity of tissue. Supported by the aqueous humor, it deflects the light transmitted to the eye, and influences by its greater or smaller convexity degrees of sight at different distances. After death it becomes flaccid from the transudation of the aqueous humor ; or, if the eye is im- mersed in water, it is rendered o[)aque by infiltration of the tissue by that fluid. Structure (fig. 228). The cornea is laminar in texture. It is constructed of a special thick part called cornea proper : in front of this is the conjunctiva, and behind is the membrane of Demours. The cornea proper^ A (lamellated cornea), is made up of a series of superposed layers, about sixty in number, which join one an- other at numerous points, and cannot therefore be detached for any distance. The lamime are formed of fibres, continuous with those of the sclerotic, and are flattened into membra- nous layers, arranged one over another. This structure possesses great toughness ; and its transparency is destroyed by disturbance of the position of the strata. The tissue when boiled gives chondrin. Between the corneal layers are flattened irregular spaces, which join freely with one another ; and these intervals are occupied by nu- cleated stellate cells, called corneal corpuscles. In the healthy condition bloodvessels do not permeate it, but cease in capillary loops at the circumference. Nerves ramify in it, after los- ing their opacity at the circumference ; they are said to form a subepithelial plexus on the anterior surface, from which varicose fibrils are prolonged amongst the pieces of the epithelium. The membrane at the back of the cornea (fig. 228) — membrane of Demours — consists of a basement layer covered by epithelium. 42 Vertical Section A of the Cornea. b. Basement layer of cornea, with (Z, the conjunctival epithe- lium on it. e. Oblique fibres from it to the layers of the cornea, e. Basement lamina, with /, epi- thelium on it of the mem- brane of Demours. o. Surface view of the epithe- lium of the membi*ane of De- mours. 658 DISSECTION OF THE EYE. The basement layer, e (posterior elastic lamina, Bowman), may be peeled off after a cut has been made across the cornea. It is dense, hard and elastic, measuring thickness ; it is very brittle, tearing readily when an attempt is made to separate it, and curls up when it is free, with the attached surface innermost. Though very elastic, the structure is destitute of fibres. It is always transparent, and remains so after boiling, after the action of acids, and even after mace- ration. At the edge of the cornea this lamina breaks up into processes (“ pil- lars of the iris”) which blend with the outer margin of the iris, and with the sclerotic and choroid coats. A laminar epithelium, G, like that on serous membranes, clothes its free surface (fig. 228). The conjunctiva in front of the cornea (fig. 228) consists chiefly of epi- thelium cells, though there is a subjacent basement-like stratum. The basement layer, b (ant. elastic lamina. Bowman), is transparent, and only from thick. It seems to be a some- what hardened piece of the cornea, without corneal spaces and corpuscles. From it fine threads are prolonged into the proper corneal layers, as in the woodcut. The epithelium, d, is formed of three or four layers of scales, the deeper being columnar, but the superficial laminar in form. Vascular Coat of the Eyeball (fig. 231). The next covering is situate within the sclerotic, and is formed chiefly of bloodvessels and pig- ment cells : the muscles in the interior of the ball are connected with it. It is constructed of three parts : a posterior (choroid) corresponding with Ihe sclerotic ; an anterior (iris) opposite the cornea ; and an interme- diate ring (ciliary muscle) on a level with the union of the sclerotic and cornea. Dissection. Supposing the cornea of an eye cut through circularly, as before directed (p. fioG), it will be necessary to take away the sclerotic to lay bare the choroid coat. With the })oint of the scalpel, or with a shut scissors, detach the fore part of the sclerotic from the front of the choroid by breaking through a soft whitish structure uniting them. Then, the eye being put into water, the outer coat is to be removed by cutting it away piece-meal with a scissors ; in taking it off the slender vessels and nerves beneath are to be preserved. The white ring around the eye in front, which comes into view during the dissection, is tiie ciliary muscle. For the purpose of obtaining an anterior view of the ciliary processes, which are connected with the anterior termination of the choroid coat, let the cornea be removed as before on another eyeball. Detach next the fore part of the sclerotic from the choroid ; and after two or three cuts have been' made in it towards the optic nerve, the resulting flaps may be pinned out, so as to support the eye in an upright position. On removing with care the iris, taking it away from the centre towards the circumference, the ciliary processes beneath will be displayed. A posterior view of the processes may be ])re})ared on another ball by cutting through it circularly with a scissors, about one-third of an inch behind the cornea, so that the anterior can be removed from the posterior half; on taking away the por- tion of the vitreous mass adherent to the anterior part of the ball, and wiping off the pigment from the back of the iris, the small processes will be made manifest. By means of this last dissection the interior of the choroid coat may be seen. CHOROIDAL COAT WITH ITS STRUCTURE. 659 If a vertical section is made of another eyeball, it will show the ciliary processes in their natural position, and will demonstrate the relative situa- tion of all the parts. This section, which is made with difficulty, should be attempted in water with a sharp large knife, and on a surface of wax or wood, after the cornea and sclerotic have been cut with a scissors. When the eye has been divided, the halves should remain in water. The CHOROID COAT (fig. 227, h) is a thin membrane of a dark color, and extends from the optic nerve to the fore part of the eyeball. When viewed on the eye in which the ciliary muscle is entire, it appears to ter- minate there ; but it may be seen in the other dissections to bend inwards behind that muscle, and to end in a series of projections (ciliary processes) behind the iris. This covering is rather thicker and stronger behind than in front. It is supported at the bottom of the eyeball by its close connection to the sclerotic coat, and in front by the ciliary muscle. Posteriorly it is pierced by a round aperture for the passage of the optic nerve ; and anteriorly it is united with the iris. The outer surface (fig. 231) is flocculent, and is covered by the rem- nants of a thin membranous layer (membrana fusca, supra-choroidea) be- tween it and the sclerotic coat : on it may be seen small veins arranged in arches, and the ciliary arteries and nerves. The inner surface is smooth, and touches the thin dark pigmentary layer of the retina (fig. 227). Fig. 229. Fig. 230. Inner View of the Front of the Choroid Coat with its Ciliary Processes, and the Back of the Iris. a. Anterior piece of the choroid coat b. Ciliary processes. c. Iris. d. Sphincter of the pupil. e. Bundles of fibres of the dilator of the pupil. The ciliary processes (fig. 229, h) are solid projections on the inner surface of the choroidal coat, and are arranged in a circle. About 85 in number, they lie side by side, and consist of larger and smaller eminences; at their inner extremity they are united by transverse ridges. About j\pth of an inch in length, they increase in depth internally, and projecting around the lens, bound circumferentially by their free ends the Pigment Cells of the Eyeball (Koiliker). A. Ramified pigment cells of the choroid coat. B. Front view of the hexagonal cells of the pigmentary membrane. 660 DISSECTION OF THE EYE. space (fig. 227, ?’) (posterior chamber) beliind the iris. In front they cor- respond with the back of the iris towards their inner end, but are sepa- rated from it by pigment ; and behind tliey are closely connected with the membrane (^) (suspensory ligament) on tlie front of the vitreous body, and fit into hollows between eminences on the anterior surface of that membrane. Stnicture The choroid coat and its ciliary processes are formed prin- cipally of bloodvessels. Ramified pigment cells make up most of the rest of the coat. The stroma or web of the choroid is formed by the outrunners of spe- cial pigment cells (fig. 230, ®) which unite together, and construct, with fine areolar tissue, a fibrous network. Its meshes are finer towards the inner than the outer surface of the choroid. On the exterior and interior of the fibrous web the vessels ramify, with the following difference in their arrangement. At the outer part (fig. 231) the larger branches of both arteries and veins are situate ; and the veins (A) form curves {vasa rorticosa) as they end in lour or five chief efferent trunks. In the interspaces of the vessels are the ramified pigment cells (fig. 230, which contain a nucleus and molecular grains of dark-brown coloring matter. At the inner part of the choroid the vessels form a network of capillaries without pigment cells, and with meshes smaller than elsewhere, whose interstices are rather less towards the back than the front of the eyeball : this part of the choroidal coat is described sometimes as a separate layer {tunica Rnyschiana). In the ciliary processes there is a similar texture of ramified blood- vessels, though with larger capillary meshes than in the choroid ; and Fig. 231. a. Sclerotic, cut, and reflected. b. Choroid coat. c. Iris. d. Circular. e. Kadiatiiig fibres of ciliary mus- cle. /. Ciliary nerves, and g, ciliary arteries between the two outer coats. h. Veins of the choroid coat. VlEAV OF THE FRONT OP THE ClIOROIDAL CoAT AND I RIS— EXTER.V A L SURFACE (Zinn). the intermixed pigment cells lose their coloring matter towards the free ends. Ciliary muscle (fig. 231). In the eye from which the sclerotic coat has been removed, the white band of the ciliary muscle (e) {annulus CILIARY MUSCLE AND IRIS. 661 albidvs), may be seen in its natural position outside the front of the clioroid coat. It consists of unstriated fibres, and forms a grayish layer, about y^th of an inch wide, on the surface of the choroid coat (fig. 231, e) : tliere are two sets of fibres in it, radiating and circular : — The radiating or superficial, arise in front from the sclerotic coat (fig. 227, «), and the fibres of the posterior elastic layer of the cornea ; its fibres are directed backwards, and are inserted into the choroid coat 0 {)po- site to, and rather behind the ciliary processes. The nerves to the iris pierce it. The circular fibres (ciliary ligament, fig. 231, d) are internal to the radiating, and form a ring about J^th of inch wide around the edge of the iris : they are not attached to the sclerotic or the cornea. Use. The radiating fibres of the muscle draw forwards the fore part of the choroid coat, and the ciliary processes, and thereby relax the suspen- sory ligament of the lens. The circular fibres are said to compress the outer part of the lens. The IRIS (fig. 231, c) is a vascular and muscular structure, about half an inch in diameter, whose vessels are continuous with those of the cho- roidal coat. Its position and connections may be observed in the difierent dissections that have been prepared. Placed within the ring of the ciliary muscle, it is suspended in front of the lens (fig. 227, /'), and is pierced by an aperture for the transmission of the light. It is circular in form, is variously colored in different persons, and is immersed in the aqueous humor. By its circumference it is con- nected with the choroid coat and the posterior elastic layer of the cor- nea. The anterior surface is free in the aqueous humor, and is marked by lines converging towards the pu[)il. The j)Osterior surface is covered with a thick layer of the pigment (fig. 227), to which the term uvea has been applied. The aperture in it (fig. 231 ) is the pupil of the eye ; this is slightly in- ternal to the centre, and is nearly circular in form, but its size is constantly varying (from ^ inch) by the contraction of the muscular fibres, according to the degree of light acting on the 0 [)tic nerve. Membrane of the pupil. In the foetus the aperture of the pupil is closed by a vascular transparent membrane, which is attached to the edge of the iris, and divides into two distinct chambers the space in which the iris is suspended. The vessels in it ai'e continuous behind with those of the iris and the case of the lens. About the eighth month the vessels become im- pervious, and at the time of birth only fragments of the structure remain. Structure (fig. 229). The stronm of the iris is composed of fibres of areolar tissue, arranged circularly at the circumference, and as radiating bundles passing like rays towards the pupil. In it are involuntary mus- cular fibres, both circular and radiating, together with pigment cells. Vessels and nerves ramify through the tissue. Muscidar fibres. The sphincter of the pupil (fig. 229, d) is a narrow band about g^th of an inch wide, which is close to the pupil, on the pos- terior aspect of the iris. The dilator of the pupil (e) is said to begin at the outer border of the iris, and to consist of bundles of fibres which join one another, and end internally in the sphincter. Action. Enlargement of the pupil is effected by shortening of the radi- ating fibres ; and diminution, by contraction of the circular ring. The 662 DISSECTION OF THE EYE. movements of the iris are involuntary and regulate the admission of light into the ball. The 'pigment cells are spread out in the stroma, and are disposed also on both surfaces. In the stroma they are ramified and irregular, as in the choroid (fig. 230, ^), and may contain yellow, brown, or very dark pig- ment. On the front they are ovalish or rounded, but still ramified ; and behind, where there is a thick layer (uvea), the cells are round without outrunners, and are filled with granules. The color of the iris is dependent upon the tint, and tlie position of the pigment. The arteries of the iris (fig. 232, have a looped arrangement : they are derived chiefly from the long and the anterior ciliary branches (c^), but some come from the vessels of the ciliary processes. On arriving at the ciliary muscle the long ciliary arteries form a circle (c) around the margin of the iris ; from this loop other anasto- motic branches are directed towards the pupil, near which tliey join in a second arterial circle ( /'). From the last circle capillaries run to the pupil, and end in veins. The i-^eins resemble the arteries in their arrangement in the iris, and ter- minate in the veins of the choroidal coat. The nerves of the iris (fig. 232, a) divide into branches, which commu- nicate, and extend towards the pupil; they are without dark outline, and their ending is not known. CiLiATiY Vessels and Nerves (fig. 231). The ciliary arteries are offsets of the ophthalmic (p. 56), and supply the choroid, the ciliary processes, and the iris. They are classed into poste- rior and anterior, and two of the first set are named long ciliary ; but they will not be seen without a special injec- tion of the vessels of the eye. The posterior ciliary brandies {g) pierce the sclerotic coat around and close to the optic nerve, and running forwards on the choi*oid, enter its substance at different points. Two of this set (long ciliary) are directed forwards, one on each side of the eyeball, and form a circle ai’ound the iris in the ciliary muscle, as be- fore explained. In the ball the outer one lies rather above, and the inner, rather below the middle. The anterior arteries, five or six in number, are smaller than the posterior, and arise at the front of the oi*bit from muscular branches (p. 56) ; they pierce the sclerotic coat about a line behind the cornea, supjily the ciliary processes, and join the circle of the long ciliary vessels. In inflammation of the iris these vessels are enlarged, and offsets of them form a ring around the cornea. Fig. 232. a Distriedtiox of the Nerves and Ves- sels OF THE Iris. A. Half of the iris representing the nerves, a. Nerves entering the membrane, and uniting in a plexus, &, within it (Kdl- liker). B. Half of the iris with apian of the ves- sels. d. Ciliary artei’ies. e. Arch of vessels at the outer edge of the iris. /. Inner circle of vessels in the iris. g. Sphincter of the iris. CHAMBER OF AQUEOUS HUMOR. 663 The posterior ciliary veins (fig. 231) are commonly four in number, and the branches entering these trunks form arches {h) (vasa vorticosa) on the surface of the choroid coat: they perforate the sclerotic layer at separate points, midway between the cornea and the optic nerve, and end in the ophthalmic vein. Anterior ciliary veins begin in a plexus within the ciliary muscle, and accompany the arteries through the sclerotic to end in the ophthalmic: they communicate with the venous space of the sinus circularis iridis (p. 656). The ciliary nerves (fig. 231, /*) are derived from the lenticular ganglion, and the nasal nerve (p. 55). Entering the back of the eyeball with the arteries, they are continued with the vessels between the sclerotic and choroid, nearly as far as the ciliary muscle: at this spot the nerves send offsets to the cornea, and piercing the fibres of the ciliary muscle, enter the iris, but their manner of ending is unknown. Offsets from the nerves supply the ciliary muscle and the choroid. Chamber of the Aqueous Humor (fig. 227). The space between the cornea in front and the lens behind, in whicli the iris is suspended, contains a clear fluid named the aqueous humor. In tlie foetus before the seventh month this interval is separated into two by the iris and the pu- pillary membrane, but in dhe adult it is only partly divided, for the two communicate through the pupil. The boundaries of the two chambers may be seen in the eye on which a section has been made. The anterior chamber is the larger part of the space; it is limited in front by the cornea, and behind by the iris. The posterior chamber (^) is a narrow interval behind the iris at tlie circumference, which is bounded in front by the iris; behind by the lens capsule, and by a piece oF the membrane (suspensory ligament of the lens) on the front of the vitreous humor : and at the circumference by the ciliary processes. The aqueous humor is quite transparent, and consists nearly of pure water. A small quantity of chloride of sodium, with some extractive matter, is in solution in it. The Retina (fig. 227, c). This layer (tunica nervea) is in part con- tinous with the optic nerve, and is the most delicate of all the coats of the eyeball. On it the image of objects is formed in the bottom of the eye. Dissection. The retina can be satisfactorily examined only on an eye which is obtained within forty-eight hours after death. To bring it into view on the eyeball in which the choroid coat was dissected, the choroidal covering must be torn away carefully with two pair of forceps, whilst the eye is immersed in water or spirit. The retina is the most internal of the three concentric strata in the globe of the eye, and is situate between the choroid coat and the trans- parent mass (vitreous) in the interior. It is moulded upon, and supported by the vitreous body; and its form is tliat of a segment of a sphere, with a large aperture in front. Beginning behind at the 0 [)tic nerve (fig. 227, c) the thin layer extends forwards to tlie ciliary processes (their outer ex- tremities), where it ends in a wavy border — tlie ora, serrata. Where the retina ceases in front, a thin gray layer (ciliary part of the retina) composed of elongated nucleated cells, which are not nerve ele- ments, is continued on as far as the tips of the ciliary processes (fig. 235, j) on which it ends. The retina is of a pinkish gray color, and is semitransparent when 664 DISSECTION OF THE EYE. fresh, so tliat an image can be seen on it when the two external coats of tlie eye have been removed; but it soon loses this translucency, and is moreover rendered opaque by the action of water and other substances. Its thickness is greater at the posterior than the anterior part of the eye- ball, being former, and yloth in the latter situa- tion. On the outer surface of the dissected retina are some fine fragments of a structure (Jacob’s membrane) to be noticed })resently, wliich float in the fluid in which the preparation may be placed. The inner surface is smooth ; it is covered Avitli folds in a preparation of an eye cut in two, but these are accidental, in consequence of the membrane having lost its proper sup- port. At the spot where the optic nerve ex- pands (porus opticus) is the central artery of the retina (fig. 233). In the anterior of the human eye, in the axis of the ball, is a slightly elli|)tical yellow part (fig. 233), yyth of an inch in diameter, which is named the yellow spot (limbus luteus of Sbrnmerring). Almost in the centre of that spot is a minute hollow, the fovea centralis^ which appears black in consequence of the thinness of the wall allowing the dark pigment outside to be seen. Structure (fig. 234). In the retina are layers or strata with bloodvessels, viz., an in- ner (®), composed of nerve elements; an outer Q) (Jacob’s membrane), formed of peculiar bodies ; and an intermediate or granular layer (^) ; and outside all is a pigmentary stratum. Passing through the layers of the retina except Jacob’s and the pigmentary, are minute threads — fibres of Miiller. The layer of nerve substance (f) is made up of nerve fibres, and of a molecular matrix containing different-sized nerve cells ; these constituents have the following arrangement : — The tubules of the optic nerve (A), having become solid in texture and gray in color from the absence of the white substance of Schwann, radiate in bundles from the end of the optic trunk, and communicate together to construct a thin web at the inner asjject of the nervous layer; this delicate network with lengthened meshes diminishes in strength as it is followed O O forwards. Outside the nerve fibres is a stratum of molecular material (_/) with large pale pyriform and roundish nucleated nerve cells (^g) witli offsets ; this layer begins at the entrance of the optic nerve, and becomes thinner as it extends forwards. Around the optic nerve the cells are arranged in a layer one deep, but over the yellow spot they are about six or eight deep ; near the ora serrata they are scattered in clusters. An offset from eacli cell is siq)posed to join internally the nerve fibres ; and other offsets are prolonged externally into the molecular material {f) and seem lost in it. Tlie outer or columnar stratum (^) (Jacob’s membrane) consists of two different elements — rods and cones, which are arranged with their ends inwards and outwards. Fig. 233. Objects on the Inner Surface OF THE Retina. In the centre of the ball is the yellow limbus luteus, here represeuied by shading ; and in its middle the dark spot. To the inner side is the nerve, with its accompany- ing artery. (Sommerring.) STRUCTURE OF RETINA. 665 Tlie rods (a) are elongated solid and grooved particles, wliich are pointed at the inner end, and are more numerous than the other elements ; from their inner ends tine threads (rod-fibres) are prolonged tlirough llie outer set of granules (c), and are there connected with elliptical transversely striated bodies. The co7ies (h) are shaped like a flask with a long neck, and have the larger end turned inwards : they do not jmoject so far out as the rods. When viewed on the outer surface, they form large isolated swell- ings (/w) amongst the ends of the rods, and at a deeper level. By their inner ends they are united with a pear-sha{)ed cell (fig. 234) in the outer part of the granular layer, and are said to reach as far as the molecular material (o?) between the two sets of granules. 1. Columnar layer with rods a, and cones, 6. 2. Granular layer with outer, e, and inner granule®, e, and intermediate iion-granular pai’t, d. 3. Nervous layer wiUi g, nerve cells, and h, nerve fibres : outside the cells is a finely granular part,/, and in- side the fibres a limiting layer, i, formed by fibres of Miiller. On the left of the vertical section is an ideal plan of the connection of the several parts. Thus the nerve cell, g, unites internally with nerve fibres, and externally with the inner granular layer; and the inner granular layer is further joined by a thread (fibre of Muller) to the outer granular layer. k. Microscopic apjiearance of the outer surface of the retina over the yellow spot, where there are only cones l. Appearance of the retina near the yellow spot — a single circle of rods surrounding each cone. rn. Appearance of the middle of the retina, a large number of the rods surrounding each cone. In all three figures the larger r.ngs represent the cones, and the smaller ones the rods seen endwise. Magnified Vertic.-m. Section of the Retina (altered from Kolliker). In the fresh state botli are soft, clear, and homogeneous, with a glisten- ing appearance, but these characters are soon destroyed by water and other fluids : their structure is very uncertain. The granular layer (^) consists of innumerable rounded and ovalish bodies with nuclei, whicli are collected into two sets (c and e), with an intervening fine molecular material {d). In the inner set (e) there are several kinds of cells, whose nature is unknown : two sets, which are oval and nucleated, are said to have this arrangement : One is connected with the fibres of Miiller ; and the other has a fibre at each end, like a bipolar ganglion-cell, which is continued outwards and inwards into the molecular material {d and /’). In the outer set (c) two kinds of nucleated cells are to be recognized, which are connected with the fibres from the rods and cones in Jacob’s layer. The cells of the rod-fibres, the most numerous, are elliptical, and marked by cross strife (Henle) (fig. 234). The cells of the cone-fibres are 666 DISSECTION OF THE EYE. pyriform in shape, with the base turned to the cone, but are free from cross stripes. The intervening molecular portion (d) has a striated appearance, from the passage of the fibres of Miiller through it. 'Y\\e fibres of Muller (fig. 234) are extremely fine threads, which pierce the substance of the retina, supporting and uniting the several layers, as with a framework of areolar tissue ; tliey reach from Jacob’s layer to the inner surface. As they pass through the granular layer they are connected with very fine threads amongst both set of granules (c and e') ; and in the inner set (c) each possesses an oval nucleated cell. At the inner surface of the retina they are dilated and joined to each other, so as to construct a bound- ing stratum (<') {memhrana limitans interna) ; and at the outer part they are united into another boundary line at the bases of the cones (jnembrana limitans externa). Structure of the yellow spot. Tlie strata of the retina undergo modifi- cations in the yellow spot, the chief of which are the following : externally, the rods of Jacob’s layer (^) are absent, and the cones become less bulged and longer towards the centre. Internally, the nerve cells {g) of the layer (^) are six to eight deep, but the nerve fibres {h) gradually cease at the edge of tlie central fovea. The intermediate strata thin gradually towards the fovea centralis, where they are so blended as to render difficult their identification. The yellow color is due to pigment diffused through the substance, ex- cept through Jacob’s membrane and the outer set of cells (c) of the granu- lar layer. Water removes it easily. Capillary vessels occupy the yellow spot, whilst the larger branches pass around on each side. The, pigmentary layer (fig. 227) covers the outer surface of the retina, and is connected thereto by fine processes.^ It consists of a single stratum of six-sided nucleated cells, with granular contents (fig. 230, which are applied to each other by the edges. Each possesses a nucleus towards the outer surface, and much pigment towards the inner. From the inner surface of the cells project very fine tlireads, which penetrate between the rods and cones of Jacob’s layer. The pigmentary layer is constituted thus as far as the ora serrata of the retina ; but in front of that line, viz., on the ciliary portion of the retina, the cells are rounded and full of pig- ment, and are continuous with the pigment on the ciliary processes and back of the iris. Vessels of the retina,. The central artery of the retina, accompanied by its vein, enters the eyeball through the optic nerve (p. 50). Inside the retina the vessel divides into four or five branches ; these pierce the stratum of fibres (fig. 234, hi)., and end in a network of capillaries amongst the ganglion cells (_ 7 ), and in the molecular material outside them (y). In the yellow spot only eapillaries exist. In tlie foetus a branch of the artery passes through the centre of the vitreous mass to supply the lens capsule. Vitreous Body. A transparent mass fills the greater part of the space witliin the coats of the eyeball (fig. 227, hf which has been named vitreous body, from its resemblance to glass ; it consists of a clear aqueous • In the dissection of tlie retina tliis pigmentary layer is removed with the choroid through the rupture of those processes ; and it has therefore been com- monly described as part of the choroid coat. VITREOUS BODY AND MEMBRANE. 667 fluid, contained in a translucent membrane, and has the consistency of jelly. Dissection. The vitreous body may be seen on the eye on which the retina was dissected, by taking away the retina, the iris, and the ciliary muscle and processes. To obtain a view of its anterior part, with the lens in situation, an eye- ball should be fixed upright ; the sclerotic and choroid coats are to be cut through about a quarter of an inch behind the cornea ; and on removing carefully the cornea, ciliary muscle, and processes with the iris, the vitre- ous body will be apparent. The vitreous body (fig. 227, h) is globular in form, and fills four-fifths of the ball, supporting the retina. In front it is slightly hollowed, and receives the lens with its capsule (^^), to which it is closely united. The fluid of the vitreous body has nearly the same composition as the aqueous humor with some salts and albumen. Enveloping the whole is a thin membrane named hyaloid. The hyaloid membrane ('/^) is a fine transparent covering of the vitreous body. It passes continuously over the surface ; and in the fcjotus it is connected with fibres which penetrate the mass. On the inner aspect are a few delicate nuclei. At the fore part it is joined by the membrane (t) supporting the lens; and it ends by uniting with the back of the lens capsule. At the bottom of the ball the membrane is closely connected with tlie retina. Structure of the vitreous mass. From the slow escape of the fluid after puncture of the hyaloid membrane, it bas been supposed that tliere are membranous partitions, dividing the vitreous mass into compartments which communicate with each otlier. In tlie centre of the vitreous body is a fibrous canal, which reaches to the back of the lens, and transmits a branch from the central artery of the retina to the lens capsule in the foetus. The vitreous mass and the hyaloid membrane are extra-vascular, and receive their nutritive material from the vessels of the ciliary processes and retina. Suspensory ligament of the lens (Zonule of Zinn). This is a transpa- rent membranous structure (fig. 235, t), placed around the lens capsule, d. Cornea. e. Ciliary muscle. /. Iris. g. Lens. i. Posterior chamber. j. Ciliary part of the retina. m. Ciliary ligament. n. Hyaloid membrane. o. Canal of Petit. r. Sinus circularis iridis. s. Ciliary process. f. Suspensory ligament of the lens. Enlarged REPREfeENTATiON of the Parts of the Eyeball on one side opposite the Lens: THE letters refer TO THE SAME PARTS AS IN THE WOODCUT, 227. which joins externally the hyaloid membrane opposite the anterior termi- nation (ora serrata) of the retina. After the ciliary processes of the cho- roid coat are detached from it, dark lines of pigment cover the suri'ace ; Fig. 235. 668 DISSECTION OF THE EYE. and wlien these are washed away plaits {ciliary processes) come into view, which are less prominent and longer than the processes ot‘ the choroid coat, and do not quite reach the lens capsule internally. The two sets of prominences are dovetailed togethej* — the projections of one being received into hollows between the other. In this membrane are stiff longitudinal and elastic fibres. Tiie tenseness or laxness is influenced by the state of the ciliary muscle ; for during its contraction the membrane is rendered lax by the drawing forwards of the ciliary processes. Canal o f Petit. Around the margin of the lens capsule is a small canal (fig. 235, o) about one-tenth of an inch across, which is situate between the susiiensory ligament and the front of the hyaloid membrane. When the canal has been opened, and tilled with air by means of a blowpipe, it is sacculated at regular intervals, like the large intestine, by the inflation of the plaits of the anterior boundary. Tiie margin of the capsule of the lens [)rojects into the space. Lens and its capsule. The lens is situate behind the pupil of the eye (fig. 227, y), and brings to a focus on the retina the light passing through that aperture. The capsule is a firm and very elastic transparent case, which is per- meable to fluid, and closely surrounds the lens : it is seated in a hollow on the front of the vitreous body. The anterior ])art projects towards the pupil ; whilst the posterior is received on the vitreous mass, to which it is inseparably united. The circumference of the case corresponds with the canal of Petit (u). Its anterior surface (fig. 227) is free, and touches the iris (./), but is separated from it by a slight space at the outer part (posterior chamber, i) ; it gives attachment towards the circumference to the suspensory liga- ment {t). The fore part of the capsule is four or five times thicker than the poste- rior, as far outwards as the attachment of the suspensory ligament, and supports itself after the removal of the lens ; it is firm and quite trans- parent, and remains clear for some time when immersed in spirit, acids, and boiling water, like the elastic layers of the cornea. The posterior part of the capsule is thin and membranous, and decreases in thickness towards the centre : it is joined by the hyaloid membrane (n) of the vitre- ous body. In the adult human eye the capsule of the lens is not provided with bloodvessels ; but in the foetus a branch of the central artery of the retina su[)plies it (p. (iOG). Di ssection. The lens will be obtained by cutting across the thin mem- branous cai)sule in which it is inclosed. The lens is a solid and transparent doubly convex body ; but the curves are unequal on the two surfaces (fig. 227, g), the posterior being greater than the anterior. Its margin is somewhat rounded ; and the measurement from side to side is one-third of an inch, but from before back about one- fourth of an inch. The density increases from the circumference to the centre ; for whilst the superficial part may be rubbed off with the finger, the deeper j)ortion is firm, and is named the nncleiis. On each surface are three lines or stellm diverging from the centre, and reaching towards the margin ; they are the edges of planes or septa, and are so situate that those on one side are intermediate in ])Osition to those on the other. In the human eye they are not distinctly seen, because th«y bifurcate repeatedly as they extend outwards. LENS AND ITS CAPSULE. 669 Covering the anterior surface of tlie lens, and connecting it with tlie capsule, is a layer of very transparent nucleated polygonal cells, which can be recognized only in a fresh eye : these become elongated towards the circumference of the lens, and seem to pass into the superficial lens-fibres. Structure. After the lens has been hardened by spirit or boiling, it may be demonstrated to consist of a series of layers (fig. 230) arranged one within another, like those in an onion. Under the microscope each layer may be seen to be constructed of minute parallel fibres. It consists mostly of albumen, and no bloodvessels are found in its texture. The lamince of each surface have their apices in the centre, where the septa meet ; they may be detached from one another at that spot, and may be turned outwards towards the equator of the lens. The constituent fibres of the lamime are about diameter, solid, and flattened at the margin of the lens ; and the deeper Fiff. 236. Fig. 237. A Representation of the Lamina in a Hardened Lens. a. The nucleus. b. Superficial laminse. fibres are narrowed and less distinct. In the superficial softer fibres are contained granular nuclei (fig. 237, a). The edges are slightly waxy ; and each fibre touches six others (fig. 237, b'), viz., two on each side, with one above, aiid an- other below : contiguous fibres are there- fore dovetailed together, and this inter- locking is best seen in the lens of the cod- fish. The ends are soft and not well-defined, and are connected with the partitions on the opposite surfaces of the lens in this way : — those attached at the union of two septa on the one aspect, are fixed to the extremity of a septum on the other aspect: and the fibres ]!assing between two septa are nearer to the pole at one end, and farther from it at the other, while the middle ones are at the same distance from the ends of the septa on both aspects. Changes in the lens with age. The form of the lens is nearly spherical in the foetus ; but its convexity decreases with age, particularly on the an- terior aspect, until it becomes flattened in the adult. In the foetus it is soft, is reddish in color, and is not quite transparent ; in mature age it is firm and clear; and in old age it becomes flatter on both surfaces, denser, and of a yellowish color. a. Surface fibres with their nuclei, in the equatorial region of the lens. b. Transverse section of the fibies of the surface of the lens, showing their union with others. 670 DISSECTION OF THE EAR. CHAPTEE XL DISSECTION OF THE EAR. The organ of bearing is made up of complex parts, which are lodged in, and attached to the surface of the temporal bone. The fundamental structure, as in the eyeball, is an expansion of a spe- cial nerve over a membrane containing fluid. This delicate apparatus is inclosed in bone for its protection ; and it is surrounded by certain acces- sory bodies which convey to it the vibrations produced by the sonorous undulations of the air. The auditory apparatus may be arranged into the parts outside, and those within the substance of the temporal bone. In the EXTERNAL SET wliich may be first examined, are included the pinna or auricle, and tlie auditory canal: the former has been noticed at p. 45, and the latter is described below. The AUDITORY CANAL (fig. 238) {meatus auditorius extermis) is the passage which leads from the pinna to the cavity (tympanum) in the tem- poral bone, and transmits inwards sonorous undulations of the air. Dissection. To obtain a view of this canal, a recent temporal bone is to be taken, to which the cartilaginous pinna remains attached. After the removal of the soft parts, the squamous piece ot‘ the bone in front of the Glaserian fissure is to be sawn off; and the front of the meatus, except a ring internally which gives support to the thin membrana tympani, is to be cut away with a bone forceps. The canal (fig. 238) is about one inch and a quarter in length, and is formed partly by bone, and partly by cartilage. It is directed forwards somewhat obliquely. In shape it is rather flattened from before back- wards; and it is narrowest in the osseous part. The outer extremity is continuous with a hollow (concha) of the external ear, and the inner is closed by the membrana tympani. The cartilaginous part {a) is largest. It is about half an inch in length, and is formed chiefly by the pinna of the outer ear which is at- tached to the margin of the meatus; but at the upper and posterior aspect the cartilage is deficient, and the tube is closed by fibrous tissue. One or two fissures (fissures of Santorini) cross the piece of cartilage. The osseous part (5) is about three-quarters of an inch long in the adult, and is constricted sometimes about the middle. Its outer extremity is dilated, and tlie posterior part projects farther than the anterior; the greater })ortion of the margin is rougli, and gives attachment to the cartilage of the pinna. The inner end is smaller, and is marked in the dry bone by a groove for the insertion of the membrane of the tympanum; it is so sloped that the anterior v.aill juts beyond the [)Osterior by about two lines. In the foetus the osseous part of the meatus is absent. After birth it grows out of the osseous ring (tympanic bone) which supports the mem- brana tympani. Lining of the meatus. A prolongation of the integument lines the BOUNDARIES OF TYMPANUM. 671 auditory passage, and is united more closely to the osseous than the carti- laginous portion; it is continued over the membrane of the tympanum in tlie form of a thin pellicle. At the entrance of the meatus are a tew hairs. In the subcutaneous tissue of the cartilaginous part of the meatus lie some ceruminous glands of a yellow-brown color, resembling in form and ar- rangement tlie sweat glands of the skin ; these secrete the ear wax, and Fig. 238. VKRTicATi Section op the Meatus Auditories and Tympanum (Scarpa). a. Cartilaginous part of the meatus. d. Cavity of the tympanum. h. Osseous portion. e. Eustachian tube, c. Memhrana tympani. open on the surface by separate orifices : they are absent in the osseous part, and are most abundant in that portion of the tube which is formed by fibrous tissue. Vessels and nerves. The meatus receives its arteries from the posterior auricular, the internal maxillary, and the temporal branch of the external carotid. Its nerves are derived from the auriculo-temporal branch of the fifth nerve, and enter the auditory passage between the bone and the carti- lage (p. 96). Inner parts of the ear. The internal constituents of the organ of hearing are inclosed within the temporal bone, and consist of two large spaces — tympanum and labyrinth, with their accessory parts. The TYMPANUM, or drum of the ear (fig. 238, c?), is a liollow interposed between the meatus auditorius and the labyrinth. It communicates with the pharynx by a tube (eti-osus superficialis externus, 33 magnus, 33, 141 parvus, 33, 678 pharyngei, 112, 117 pharyngeus, 113 idirenicus, 80, 330 plantaris externus, 619 profundus, 624 internus, 624 pneumo-gastricus, 112, 181, 330, 452 popliteus externus, 596 internus, 596 portio dura, 47, 142, 180 mollis, (o) 181, (d) 687 pterygoidei, 95 pterygoideus internus, 95, 145 pudendus iuferior, (o) 589, (d) 394, 407 internus, (o) 518, (d) 391, 399, 408 pulmonares anteriores, 331 posteriores, 331 radialis, 263, 270 recurrens, 114, 331, (d) 158 articularis, 633 sacrales, rami anteriores, 518 posteriores, 372, 581 saphenus externus, 606, (d) 627 internus, (o) 573, (d) 557, 573, 627 sciaticus magnus, 519, 589. 599 parvus, 519, 582, 584, 599 spermatici, 443 spheno-palatini, 104 splanchnicus major, (o) 342, 452 minor, (o) 342, (d) 452 minimus, (o) 342, (d) 452 splenici, 451 stylo-hyoideus, 48 708 INDEX. Nerv. — suboccipitalis, ramus anterior, 115 posterior, 3(38 subscapulares, 236 superficialis cordis dexter, (o) 117 (d) 332 sinister, (o) 122, (d) 314 supramaxillares nervi facialis, 48 orbitalis, 22, 51 scapularis, 80, 248, 359 trochlearis, 23, 52 sympatheticus abdominis, 443, 450, 497 cervicis, 115 pelvis, 519 thoracis, 331, 341 temporales nervi facialis, 48 profundi, 95 superficiales, (d) 23, (o) 48 temporo-facialis, 48 malaris, 60, 104 tboracici, auteriores, 236 laterales, 226 thoracicus posterior, 80, 236 tibialis anticus, 627, (d) 632 posticus, 613 trigeminus, 31, 180 trochlearis, 31, 51, 180 tympanicus, (o) 112, (d) 678 ulnaris, 255, 269, 274 uterini, 520 vaginales, 520 vestibularis, 687 vidianus, 141 Ninth nerve, (o) 182, (c) 115, (d) 83, 102 Nipple of the breast, 226 Nodule, 212 Nose, cartilages, 42 cavity of, 133 meatuses of, 134 nerves and vessels of, 139, 141 Nuclei of medulla oblongata, 187 Nucleus caudatus, 203 lenticularis, 203 Nutritious artery of fibula, 613 of femur, 578 of humerus, 254 of tibia, 612 Nymphae, 534 O BLIQUUS abdominis externus, 409 intern us, 411 capitis inferior muscle, 369 superior muscle, 369 oculi inferior, 59 superior, 53 Obturator artery, (o) 515, (d) 580 fascia, 500 ligament, 546 membrane, 54b muscle, external, 580, 591 internal, 543, 590 Obturator nerve, (o) 497, (d) 577 Occipital artery, (o) 86, (c) 368, (d) 21 lobe, 194 vein, 21, 86 sinus, 27 Occipito-atloid articulation, 168 ligaments, 168 Occipito-axoid ligaments, 169 frontalis muscle, 18 Odontoid ligaments, 169 (Esophagus, connections of, 121, 339 structure, 131, 339 (Esophageal arteries, 337, 447 nerves, 331 opening of diaphragm, 487 Olfactory bulb, 179 cells, 137 nerve, (o) 178, (d) 138 region, 137 Olivary body, 183, 185 commissure, 186 fasciculus, 186, 189, 208 Omentum, great, 437 small, 437 splenic, 437 Omo-hyoid muscle, 72 Ophthalmic artery, 33, 56 ganglion, 55 nerve, (o) 31, (c) 32, (d) 51 vein, 57 Opponens pollicis muscle, 278 Optic commissure, 179 nerve, (o) 179, 207, (c) 57, (d) 664 thalamus, 207, 211 tract, 179 Ora serrata, 663 Orbicular ligament of the radius, 294 Orbicularis oris, 37 palpebrarum, 36 Orbit, 50 muscles of, 53, 57 nerves, 51 periosteum of, 50 vessels, 56 Orbital branch of nerve, (d) 60, (o) 104 Organ of Corti, 684 of Giraldes, 483 Orifice of the urethra, 535 of the uterus, 535 of the vagina, 535 Os hyoides, 159 Ossicles of the tympanum, 674 Os tincffi, 537 Os uteri externum, 537 Otic ganglion, 144 Otoliths, 686 Outlet of the pelvis, 386 Ovaries, 512, 539 appendage to, 540 arteries of, 490, 516 Ovicapsule, 540 INDEX 709 Ovisacs, 540 Ovum, 539 P ALATE (soft), 128 Palatine, arteries, superior, 143 artery, inferior, 86 nerve, external, 141 large, 140 small, 141 Palato-glossus, 130, 148 Palato-pharyngeus, 130 Palm of the hand, 272 cutaneous nerves of, 272 Palmar arch, deep, 2S0 superficial, 273 nerve of the ulnar, deep, 280 superficial, 274 cutaneous nerves, 272 fascia, 272 Palmaris brevis muscle, 272 longus muscle, 265 Palpebrse, 43 Palpebral arteries, 45, 57 ligament, 44 nerves, 45 veins, 45 Pancreas, 464 connections, 446 structure of, 464 Pancreatic arteries, 447 duct, 457, 465 veins, 448 Pancreatico-duodenal arteries, 440, 448 Papilla lachrymalis, 45 Papillje of the tongue, 146 Parietal lobe, 194 Parovarium, 540 Parotid gland, 41 arteries, 86 Patellar nerve, 573 plexus, 557 Pectineus muscle, 576 Pectoralis major muscle, 230, 231 minor muscle, 231 Peduncle of the cerebellum, inferior, 215 middle, 215 superior, 215 of the cerebrum, 190, 211 of the pineal body, 208 Peduncular fibres, 207 Pelvis, female, dissection of, 509 male, 499 dissection of, 499 Pelvic cavity, 499 fascia, 500 plexus, 519 Penis, 508 integument of, 407 structure of, 529 vessels of, 532 Peptic glands, 455 Perforating arteries of the femoral, 578, 599 of internal mammary, 239 of the palm, 280 of the sole, 623, 632 Perforans Casserii nerve, (o) 236, (c) 256, (d) 262 Pericardium, 310 vessels of, 311, 337 Perilymph, 681 Perinaeum, female, 400 male, 386 Perinaeal artery, superficial, 393 fascia, deep, 396 superficial, 392 nerves, superficial, 391, 393, 399 Periosteum of the orbit, 50 Peritoneal prolongation on the cord, 417 Peritoneum, 435 of female j)elvis, 510 of male pelvis, 504 Peroneal artery, 613 anterior, 613 nerve, 596 Peroneus brevis muscle, 633 longus muscle, 625, 633 tertius muscle, 629 Peroneo-tibial articulations, 641 Pes hippocampi, 204 Petrosal ganglion. 111 sinus, inferior, 29 superior, 29 nerve, large, 33, 141 small, 33, 678 external, 33 Peyer’s glands, 459 Pharynx, 124 interior, 126 muscles of, 124 openings of, 126 Pharyngeal ascending artery, 109 nerve, 113 vein, 112 Pharyngeo-glossal muscle, 149 Phrenic artery, 330, 490 nerve, 80, 330 Pia mater of the brain, 173 of the cord, 376 Pigmentary layer of retina, 666 Pigment cells of choroid, 660 iris, 662 Pillars of the abdominal ring, 410 of the fornix, 208 of the iris, 658 of the soft palate, 128 Pineal body, 208 Pinna, or auricle of the ear, 45 Pituitary body, 192 Plantar aponeurosis, 615 arch of the artery, 623 arteries, 617, 623 ligament, long, 647 nerve, external, 619, 624 internal, 619 45 * 710 INDEX. Plantaris muscle, 609 riatysma myoides muscle, 62, 67 Pleura, 307 Plexus, aortic, 443 brachial, 79, 235 cardiac, superficial, 314 deep, 332 carotid, 33 cavernous, 33 ■cervical, 80 posterior, 367 choroides cerebri, 205 cerebelli, 218 coeliac, 451 coronary, anterior, 314 posterior, 314 coronary of the stomach, 451 diaphragmatic, 451 gulae, 331 hepatic, 451 heemorrhoidal, 520 liypogastric, 444 lumbar, 496 mesenteric, inferior, 443 mesenteric, superior, 443 cesophagean, 331 ovarian, 520 patellar, 557 pelvic, 519 pharyngeal, 113 prostatic, 520 pterygoid of veins, 94 pulmonary anterior, 331 posterior, 331 renal, 451 supra, 451 sacral, 518 solar, 451 spermatic of nerves, 443 of veins, 492 splenic, 451 tympanic, 678 uterine, ^20 vaginal, 520 vesical, 520 vertebral, 117, 166 Plica semilunaris, 45 Pneumogastric nerve, (o) 181, (d) 112, 181, 330, 452 Pons Tarini, 191 Varolii, 188 structure of, 184 Popliteal artery, 594 glands, 597 nerve, external, 596 internal, 596 space, 593 vein, 596 Popliteus muscle, 610, 635 I’ortal veins, 448 I’ortio dura, (c) 144, (d) 47, (o) 180 mollis, (o) 181, (d) 687 Porxis opticus, 664 Posterior commissure, 207 Posterior — elastic layer of cornea, 658 ligament of knee, 636 medullary vellum, 214 pyramid, 184, 186 triangle of the neck, 63 vesicular column, 383 Poupart’s ligament, 411, 559 Pouch, laryngeal, 155 of the auricula, 316, 319 Prepuce, 583 Princeps cervicalis artery, 368 pollicis artery, 280 of the foot, 624 Processus cochleariformis, 673 vermiformis, 212, 216 Profunda artery, inferior, 254 of the neck, (o) 78, (d) 368 of the thigh, 565, 578 superior, (o) 254, (d) 258 Promontory, 672 Pronator quadratus muscle, 271 radii teres muscle, 264 Prostate gland, 571 connections, 507 structure, 521 Prostatic part of the urethra, 526 sinuses, 527 Psoas magnus muscle, 492, 580 Psoas parvus muscle, 493 Pterygoid arteries, 95 nerve, external, 95 internal, 95, 145 plexus of veins, 94 Pterygoideus externus muscle, 89 internus muscle, 90 Pterygo-maxillary ligament, 124 region, 87 palatine artery, 142 Pubic region of the abdomen, 431 symphisis, 546 Pudendal inferior nerve, (o) 589, (d) 394 Pudic arteries, external, 554, 565 artery, internal, (d) 390, (c) 398, 408, (o) 516 nerve, internal, (o) 408, (d) 390, 398 Pulmonary artery, (d) 318, 325, 335 nerves, 331 veins, 319, 329, 336 Puncta lachrymalia, 43, 60 Pupil, muscles of, 661 Pylorus, 453 Pyloric arteries, 447 Pyramid, anterior, 183, 185 decussation of, 186 of the cerebellum, 213 of the thyroid body, 120 of the tympanum, 672 posterior, 184, 186 Pyramidal fibres of the medulla, 185 masses of kidney, 474 Pyramidalis abdominis muscle, 416 nasi muscle, 34 INDEX. 711 Pyramids of Malpighi, 474 Pyriformis muscle, 542, 587 Q UADRATUS femoris muscle, 590 lumborum muscle, 494 R adial artery, 265, (d) 280, 289 nerve, 262^ 270 veins, 266 cutaneous, 261 Radialis indicis artery, 272 Radio-carpal articulation, 296 Radio-ulnar articulations, 294, 297 Ranine artery, 101 vein, 101 Raphe of the corpus callosum, 200 of the medulla, 186 of the perineum, 386 Receptaculum chyli, 495 Recto-vesical fascia, 502 pouch, 504 Rectus abdominis muscle, 415 capitis anticus major, 164 minor, 165 posticus major, 369 minor, 369 lateralis, 115 femoris, 570, 587 Rectus oculi externus, 57 inferior, 57 internus, 57 superior, 53 Rectum, connections of, in the female, 510 connections of, in the male, 504 structure, 532 Recurrent interosseous artery, 288 radial, 266 tibial, 631 ulnar, anterior, 268 posterior, 268 Recurrent nerve of' pneumogastric, (o) 114, 331, (d) 158 nerve of the tibial, 631 Renal artery, (d) 476, (o) 489 plexus, 451 vein, (o) 476, (c) 492 Restiform body, 184, 186 Rete testis, 482 Retina, 663 structure, 664 Retrahens aurem, 18 Rhomboideus major muscle, 358 minor, 358 Rima of the glottis, 155 Ring, abdominal, external, 410 internal, 417, 421 Risorius Santorini muscle, 39 Rods of retina, 665 Root of the lung, 309, 310 Roots of the nerves, 307, 383 Rotatores dorsi, 371 Round ligament of the hip joint, 602 of the liver, 468 of the uterus, 418, 512, 539 ACCULE of the ear, 686 Sacculus laryngis, 155 vestibuli, 685 Sacral artery, lateral, 515 middle, 489, 517 ganglia, 519 nerves, anterior branches, 518 posterior branches, 372, 581, 584 plexus, 518 Sacro-coccygeal articulation, 544 iliac, 544 vertebral, 544 lumbalis muscle, 362 sciatic ligament, large, 545, 592 small, 545, 592 Salpingo-pharyngeus muscle, 126 Salvatella vein, 361 Saphenous vein, external, 606, 626 internal, 555, 573, 606, (o) 626 opening, 559 nerve, external, 606, (d) 627 internal, (o) 573, (d) 557, 573, 627 Sartorius muscle, 566 Scala tympani, 684 vestibuli, 684 Scalenus anticus muscle, 75 medius, 75 posticus, 75 Scapular artery, posterior, 78, 248, 359 ligaments, 247 muscles, 240, 244 Scapulo-clavicular articulation, 246 humeral, 290 Scarpa’s triangle, 563 Schneiderian membrane, 135 Sciatic artery, (o) 516, (d) 588 nerve, large, 519, 589, 599 small, 519, 582, 588, 599 Sclerotic coat of the eye, 655 structure, 656 Scrotum, 408 Second nerve, (o) 179, (c) 57, (d) 664 Secondary membrane of the tympanum, 672, 673 Segments of the cord, 382 Semicircular canals, 680 Semilunar cartilages, 638 ganglia, 451 valves of aorta, 321 of pulmonary artery, 318 Semi-bulbs of vagina, 527 Semi-membranosus muscle, 598, 636 Seminal ducts, 523 Seminiferal tubes, 481 'Semi-spinalis colli muscle, 370 j dorsi muscle, 370 1 Semi-tendinosus muscle, 597 712 INDEX. Septum aiiricularum, 322 cochleae, 682 crurale, 428, 561 intermuscular, of the arm, 258 of the thigh, 572 lucidum, 202 nasi, 134 pectiniforme, 530 scroti, 408 of the tongue, 147 ventriculorum, 324 Serratus magnus muscle, 236 posticus inferior, 360 superior, 360 Seventh nerve, (o) 180, (c) 142, (d) 47 Sheath of the fingers, 273 of the rectus, 415 of the toes, 616 Shoulder joint, 290 Sigmoid artery, 442 flexure of the colon, 434 valves, 318, 321 Sinus, basilar, 29 of the bulb, 527 cavernous, 28 circular, of Ridley, 29 coronary, 314 lateral, 28 longitudinal, inferior, 27 superior, 25 occipital, 27 petrosal, inferior, 29 superior, 29 pocularis, 526 prostaticus, 527 straight of the skull, 27 torcular, 27 transverse, 29 of Valsalva, 321 Sixth nerve, (o) 180, (c) 32, (d) 57 Small intestine, 429, 456 omentum, 438 Socia parotidis, 41 Soft commissure, 206 Soft palate, 128 muscles of, 128 Solar plexus, 451 Sole of the foot, dissection of, 614 Soleus muscle, 608 Solitary glands, 459, 464 Spermatic artery, (o) 489, (d) 484 cord, 418 fascia, 423 plexus, 443 veins (o) 484, (c) 492 Spheno-palatine artery, 142 ganglion, 139 nerves, 104 Sphincter ani externus, 389 internus, 389 of the pupil, 661 vaginae, 402 vesicae, 525 Spigelian lobe, 467 Spinal accessory nerve, (o) 181, (d) 114 nucleus, 187 arteries, 174, 379 cord, 380 membranes of, 374 structure, 382 nerves, 377 filaments of origin, 383 roots of, 377 veins, 385 Spinalis dorsi muscle, 362 Spiral tube of the cochlea, 682 Splanchnic nerve, large, 342, (d) 452 small, 342, (d) 452 smallest, 342, (d) 452 Spleen, 465 connections, 435 structure, 465 Splenic artery, 447, 466 omentum, 447 plexus of nerves, 451 vein, 448 Splenius capitis muscle, 361 colli, 361 Spongy bones, 134 part of the urethra, 527 Stapedius muscle, 676 Stapes bone, 675 Stellate ligament, 344 Stenson’s duct, 41 Sterno-clavicular articulation, 170 cleido-mastoid muscle, 71 hyoid muscle, 73 thyroid, 73 Stomach, form and divisions, 453 connections of, 431 structure of, 453 Straight sinus, 27 Striate body, 203, 211 Stylo-hyoid ligament, 106 muscle, 83 nerve, 48 glossus muscle, 99, 148 mastoid artery, 94 maxillary ligament, 91 pharyngeus muscle, 106 Subanconeus muscle, 259 Subarachnoid space, 376 of the cord, 376 Subclavian artery, left, 118, (o) 328 right, 75 vein, 79 Subclavius muscle, 232 Subcrureus, 572 Subcutaneous malar nerve, 60, 104 Sublingual artery, 101 gland, 103 Submaxillary ganglion, 101 gland, 97 region, 97 Submental artery, 86 Suboccipital nerve, anterior branch, 115 posterior branch, 367 Subpeduncular lobe, 214 INDEX. 713 Subperitoneal fat, 417, 561 Subpubic ligament, 547 Subscapular artery, 235 nerves, 236 Subscapularis muscle, 241 Substantia gelatinosa, 383 perforata antica, 192 Sulci of brain, 193, 213 Sulcus, longitudinal, of the liver, 467 spiralis, 683 transverse, 467 Superficial fascia of the abdomen, 405 of the perinseum, 392 of the thigh, 553, 554 Superficialis cervicalis artery, 359 volse artery, 266 Supinator radii brevis, 288 longus, 284 Supra-orbital artery, 21, 56 nerve, 22, 52 renal capsule, 478 plexus, 451 scapular artery, 78, 247, 359 nerve, 80, 248, 359 spinal artery, 248 spinatus muscle, 247 trochlear nerve, 23, 52 Suspensory ligament of the lens, 667 of the liver, 439 of the penis, 408 Sympathetic nerve in the abdomen, 443, 452 in the head, 33 in the loins, 497 in the neck, 115 in the pelvis, 519 in the thorax, 341 Symphysis pubis, 446 Synovial gland of Havers, 603 ^vENIA hippocampi, 204 semicircularis, 204 Tarsal artery, 631 articulation, 647 cartilages, 44 Tarso-metatarsal articulations, 649 Taste buds, 147 Teeth, 132 Tegmentum, 191 Temporal aponeurosis, 19 artery, 86 deep, 94 middle, 87 superficial, 21 fascia, 19 muscle, 20, 88 nerves, deep, 95 superficial, 23, 48 vein, 21, 88 Temporo-fascial nerve, 48 malar nerve, 60 maxillary articulation, 90 sphenoidal lobe, 194 Tendo Achillis, 609 palpebrarum, 40 Tendon of triceps extensor, 566 Tensor palati muscle, 129 tarsi, 59 tympani, 676 vaginje femoris, 570 Tentorium cerebelli, 27 Teres major muscle, 245 minor, 245 Testes, 479 Thalamus opticus, 207, 211 Thebesian foramina, 316 valve, 317 Thigh, dissection of, back, 592, 597 front, 552 Third nerve, (o) 180, (d) 54, 57, (c) 30 ventricle, 206 Thoracic duct, 118, 339, 494 ganglia, 339 Thoracic-acromial artery, 234 alar, 234 humeral, 234 long, 234 superior, 234 Thorax, boundaries of, 305 parietes of, 342, 237 Thymus body, 308 Thyro-arytsenoid articulation, 162 ligaments, 156 arytsenoideus muscle, 153 epiglottidean ligament, 162 hyoid membrane, 161 muscle, 73 Thyroid artery, inferior, 78, 121 superior, 85, 121 axis of artery, 78 body, 120 cartilage, 159 plexus of veins, 121 vein, inferior, 78, 121 middle, 82 superior, 85 Tibial artery, anterior, 630 posterior, 612 nerve, anterior, 683, (d) 627 posterior, 613 veins, anterior, 632 posterior, 613 Tibialis anticus muscle, 628 posticus, 611, 625 Tibio-tarsal articulation, 643 Tongue, 146 muscles of, 148 nerves of, 151 vessels of, 101 Tonsil, 131 Tonsilitic artery, 86 Torcular Herophili, 27 Trachea, connections of, 121, 333 structure of, 162 Trachelo-mastoid muscle, 363 Tractus intermedio-lateralis, 383 Tragus, 46 714 INDEX Tragus — muscle, 46 Transverse colon, 434 fissure of the cerebrum, 204 of the liver, 468 ligament of the acetabulum, 602 of the atlas, 169 of the fingers, 273 of the knee, 639 of the metacarpus, 280 of the metatarsus, 624 of the toes, 615 peril! seal artery, 393 sinus, 29 tarsal articulation, 647 Transversalis abdominis muscle, 413 cervicalis artery, (o) 78, (d) 359 colli muscle, 363 faciei artery, (o) 87, (d) 41 fascia, 417, 428 Transversus auriculse muscle, 47 linguse, 150 pedis, 621 perinaei, 395, 403 deep, 397, 403 Trapezius muscle, 354 Trapezoid ligament, 246 Triangle of the neck, anterior, 69 posterior, 69 Triangular cartilage of the nose, 134 fibro-cartilage of wrist, 297 ligament of groin, 411 of the urethra, 396 space of the thigh, 562 surface of the bladder, 525 Triangularis sterni muscle, 238 Triceps extensor cruris, 570 cubiti, 258 Tricuspid valve, 318 Trigeminal nerve, (o) 180, (c) 31 Trigonum vesicse, 525 Trochlea, 53 Trochlear nerve, infra, 54 supra, 23, 52 Tube of the cochlea, 681 Tuber cinereum, 206 Tubercle of Rolando, 187 Tubules of the stomach, 454 of small intestine, 459 of large intestine, 463 Tubuli seminiferi, 481 uriniferi, 474 Tunica albuginea testis, 481 Ruyschiana, 660 vaginalis, 480 oculi, 655 vasculosa testis, 481 Turbinate bones, 134 Twelfth intercostal nerve, 416, 498, 581 Tympanic artery, 93 Tympanum, 674 arteries of, 674 lining membrane, 677 nerves of, 677 U LNAR artery, 267, 273 nerve, (o) 236, (c) 255, (d) 269, 274 veins, 268 cutaneous anterior, 261 posterior, 261 Umbilical hernia, 426 region of the abdomen, 431 vein, 469 Umbilicus, 404 Ureter, 477, 510, 526 Urethra, female, 541 connections, 512 orifice of, 535 structure, 542 male, interior, 526 connections, 507, 526 structure,- 527 Uterine arteries, 516, 539 plexus of nerves, 520 veins and sinuses, 517 Uterus, 537 interior of, 538 ligaments of, 510 connections of, 511 structure of, 538 Utricle of the ear, 685 Uvea iridis, 661 Uvula cerebelli, 212 palati, 128 vesicse, 574 AGINA, connections, 512, 535 structure and form, 536 Vaginal arteries, 516, 537 plexus, 520 veins, 517 Vagus nerve, 112, 181, 330, 452 nucleus, 187 Vallecula, 212 Valve, Eustachian, 317 of csecum, 462 mitral, 320 semilunar, 318, 321 of Thebesius, 317 tricuspid, 318 of Vieussens, 215 Valvulse conniventes, 457 Vas deferens, 418, 483, 523 aberrans, 483 Vasa aberrant] a, 250 brevia, 447 efferentia testis, 482 rete testis, 482 vorticosa, 660 Vascular coat of eye, 658 Vastus externus muscle, 571 internus muscle, 571 Vein, alveolar, 142 angular, 21 ascending cervical, 78 lumbar, 498 pharyngeal, 110 auditory, 687 INDEX. 715 Vein — auricular, posterior, 21 axillary, 235 azygos, large, 338, 495 small, 338, 494 superior, left, 338 basilic, 249 brachial, 255 brachio-cephalic, left, 329 right, 328 bronchial, left, 336, 337 right, 336, 337 cardiac, anterior, 314 great, 314 small, 314 cava, inferior, 329, 444, 492 superior, 328 cephalic, 250 cerebellar, 177 cerebral, 177 choroid, 206 ciliary, anterior, 662 posterior, 663 circumflex iliac, 420, 491 coronary of the heart, 314 of the stomach, 448 of the corpus caver nosum, 531 striatum, 206 deep cervical, 77, 368 diaphragmatic, inferior, 492 dorsal, of the penis, 517 dorsi-spinal, 369 emissary, 21 emulgent, 476, 492 epigastric, deep, 420, 491 superficial, 407, 554 facial, 40, 86 femoral, 565, 568 frontal, 21 of Galen, 208 gastro-epiploic, left, 449 hemorrhoidal, 517, 533 hepatic, 471, 492 iliac, common, 491 external, 491 internal, 517 infraorbital, 40, 105 innominate, 328 intercostal, 338 posterior branch, 368, 385 superior, left, 338 right, 338 intraspinal, 385 interlobular, 471 intralobular, 471 jugular, anterior, 71 external, 42, 62 internal, left, 118 right, 82, 109 laryngeal, 158 lingual, 101 longitudinal, of the spine, anterior, 385 lumbar, 369, 498 Vein — mammary, internal, 238, 329 median, of the arm, 249, 261 basilic, 249 cephalic, 249 maxillary, internal, 94, 329 anterior, internal, 40, 142 mesenteric, inferior, 443 superior, 441 occipital, 21, 80, 369 ophthalmic, 57 ovarian, 492 palpebral, inferior, 40 pancreatic, 448 perineal, superficial, 393 pharyngeal, 110 phrenic, inferior, 492 popliteal, 596 portal, 448, 471 posterior, spinal, plexus of, 385 profunda of the thigh, 579 pterygoid plexus, 94 pudic external, 555 internal, (o) 399, (c) 532 pulmonary, 319, 329 radial cutaneous, 261 ranine, 101 renal, 476, 492 sacral, lateral, 517 middle, 517 saphenous, external, 606, (o) 626 internal, 555, (o) 626 spermatic, 484, 492 spinal, 380 splenic, 448 subclavian, 79 sublobular, 471 supra-orbital, 21 renal, 479, 492 scapular, 78, 248, 359 temporal, 21, 87 superficial, 21 thyroid, inferior, 78, 121, 329 middle, 82 superior, 85 tibial anterior, 632 posterior, 613 transverse cervical, 78, 359 ulnar, 267 cutaneous, anterior, 261 posterior, 261 umbilical, 469 uterine, 517 vaginal, 517 vertebral, 77, 166 vesical, 517 of the vertebrse, 385 Velum interpositurn, 205 pendulum palati, 128 Vena cava, inferior, 444, 492 superior, 328 portae, 449, (d) 471 Venae cavae hepaticae, 471 Venous arch of the foot, 626 716 INDEX. Venous arch — of the hand, 261 Ventricles of the brain, 200 fifth, 202 fourth, 217 lateral, 200 third, 206 of the heart, 313 left, 320 right, 317 structure of, 321 of the larynx, 156 Vermiform appendix, 433, 462 processes, 212, 216 Vertebral artery, (o) 77, (c) 165, (d) 174 plexus, 117, 166 vein, 77, (o) 166 Veru montanum, 526 Vessels of the brain, 174 of the dura mater, 29, 376 Vesica urinaria, 524 Vesical artery, inferior, 515 superior, 515 plexus of nerves, 520 veins, 517 Vesicula prostatica, 526 Vesicular column of cord, 383 Vesiculge seminales, connections, 507 structure, 522 Vestibule of the ear, 679 artery of, 687 nerve of, 687 of the vulva, 535 Vestigial fold of pericardium, 311 Vidian artery, 142 nerve, 141 Villi, intestinal, 458 Vitreous body, 666 fluid, 667 Vocal cords, 156 Vulva, 533 ^ HARTON’S duct, 98, 103 IT White commissure of the cord,, 382 Winslow’s foramen, 437 Wrisberg’s nerve, 236, 251, 256 Wrist-joint, 296 yELLOW spot of eyeball, 664, 666 Z ONULE of Zinn, 667 Zygomaticus major muscle, 39 minor muscle, 39 THE END. HEISTRY C. (LATE LEA k BLANCHARD's) O^T^LOaTJE OF MEDICAL AND SUKGICAL PUBLICATIONS. In asking the attention of the profession to the works advertised in the following pages, the publisher would state that no pains are spared to secure a continuance of the confidence earned for the publications of the house by their careful selection and accuracy and finish of execution. The printed prices are those at which books can generally be supplied by booksellers throughout the United States, who can readily procure for their customers any works not kept in stock. Where access to bookstores is not convenient, books will be sent by mail post-paid on receipt of the price, providing their weight does not exceed the postal limit of four pounds (see page 32); but no risks are assumed either on the money or the books, and no publications but my own are supplied. Gentlemen will therefore in most cases find it more convenient to deal with the nearest bookseller. An Ir.LUSTRATED Catalogue, of 64 octavo pages, handsomely printed, will be for- warded by mail, post-paid, on receipt of ten cents. HENRY C. LEA. Nos. 706 and 708 Sansom St., Philadelphia, April, 1870. ADDITIONAL INDUCEMENT FOR SUBSCRIBERS TO THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES. THREE MEDICAL JOURNALS, containing over 2000 LA SUE PAGES, Free of Postage, for SIX DOLLAES Per Annum. TERMS FOR 1879. The American Journal of the Medical Sciences and 1 Five Dollars per annum, The Medical News and Library, both free of postage, j in advance. OF. The American Journal of the Medical Sciences, published quar- 1 c;;„ i) n terly (1150 pages per annum), with j . o ar , I'lie Medical News and Library, monthly (384 pp. per annum), and [- per annum, The Monthly Abstract of Medical Science (592 pages per j advance annum). J S EPABA TE S UBSCRIPTIONS TO The American Journal of the Medical Sciences, when not paid for in advance. Five Dollars. The Medical News and Library, free of postage, in advance. One Dollar. The Monthly Abstract of Medical Science, free of postage, in advance. Two Dollars and a Half. Advance-paying subscribers can obtain at the close of the year cloth covers, gilt-lettered, for each volume of the Journal (two annually), and of the Abstract (one annually), free by mail, by remitting ten cents for each cover. In commencing the second year of the second half century in the career of the “American Journal op the Medical Sciences,” the publisher has much pleasure in assuring its wide circle of readers, that at no former period has it had the prospect of a more extended sphere of usefulness. Sustained as it is by the profession of the whole United States, and with a circulation extending to every country in which the English language is read, the efforts of the editors will be directed, as heretofore, to render it in every way worthy of its reputation, and of the universal favor with which it is received. With its attendant periodicals, the “Medical News and Library” and the “Monthly A bstract of MedicalSciexce,” it combines the advantages of the elaborate preparation which can be given to a quarterly, and the prompt conveyance of intelligence by the monthly, while, the whole being under a single editorial supervision, the subscriber is secured against the duplication of matter inevitable under other circumstances. These efforts the publisher seeks to second by offering these periodicals at a price unprece- dentedly low — a price which placesthem within the reach of every practitioner, and gives the equivalent of three or four large octavo volumes for the comparatively trifiing (For The “Obstetrical Journal,” see p. 23.) 2 Henry C. Lea’s Publications— (^ m. Journ. Med. Sciences). cost of Six Dollars per annum. The three periodicals thus offered are universally known for their high professional standing in their several spheres. THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES, Edited BY ISAAC HAYS, M.D., and I. MINIS HAYS, M.D., is published Quarterly, on the first of J anuary, April, July, and October. Each num- ber contains nearly three hundred large octavo pages, appropriately illustrated wher- ever necessary. It has now been issued regularly for over fifty years, during the whole ofwhich time it has been under the control of the presentsenior editor. Through- out this long period, it has maintained its position in the highest rank of medical peri- odicals both at home and abroad, and has received the cordial support of the entire profession in this country. Among its Collaborators will be found a large number of the most distinguished names of the profession in every section of the United States, rendering its original department a truly national exponent of American medicine.* Following this is the ‘‘ Revif.w Department,” containing extended and impartial reviews of important new works, together with numerous elaborate “Analytical and Bibliographical Notices” giving a complete survey of medical literature. This is followed by the “Quarterly Summary of Improvements and Discoveries in the Medical Sciences,” classified and arranged under different heads, presenting a very complete digest of medical progress abroad as well as at home. 1'hus, during the year 1878, the “Journal” furnished to its subscribers 77 Original Communications, 133 Reviews and Bibliographiiuil Notices, and 25.5 articles in the Quarterly Summaries, making a total of Four Hundred and Sixty-five articles illustrated with 48 maps and wood engravings, emanating from the best professional minds in America and Europe. That the efforts thus made to maintain the high reputation of the “Journal” are successful, is shown by the position accorded to it in both America and Europe as a leading organ of medical progress: — This is universally acknowledged as the leading American Journal, and has been conducted by Dr. Hays alone until 1869, when his son was associated with him. We quite agree with the critic, that this journal is second to none in the language, and cheer- fully accord to it the first place, for nowhere shall we find more able and more impartial criticism, and nowhere such a repertory of able original articles. Indeed, now that the ‘‘British and Foreign Medicu- Chirurgical Review” has terminated Its career, the American Journal stands without a rival. — London Med. Times and Gazette, Nov. 24, 1877. The Philadelphia Medical and Physical Journal issued its first number in 1820, and. after a brilliant career, was succeeded in 1827 by the American Journal of the Medical Sciences, a periodical of world-wide reputation ; the ablest and one of the oldest periodicals in the world — a journal which has an unsullied record. — Gross’s History of American Med. Literature, 1876. It is universally acknowledged to be the leading American medical journal, and, in our opinion, is second to none in tne language. — Boston Med. and Sarg. Journal, Oct. 1877. The present number of the American Journal is an exceedingly good one, and gives every promise of main tainiug the well-earned reputation of the review Our venerable contemporary has our best wishes, and we can only express the hope that it may con- tinue its work with as much vigor and excellence for the next fifty years as it has exhibited in the past. — London Lancet, Nov. 24, 1877. This is the medical journal ofour country to which the American physician abroad will point with the greatest satisfaction, as reflecting the state of medical culture in his country. For a great many years it has been the medium through which our ablest writ- ers have made known their discoveries and observa- tions — Address of L. P. Yandell, M.D., he fore Inter- national Med. Congress, Sept. 1876. And that it was specifically included in the award of a medal of merit to the Publisher in the Vienna Exhibition in 1873. 'I'he subscription price of the “American Journal of the Medical Sciences” has never been raised during its long career. It is still Five Dollars per annum ; and when paid for in advance, the subscriber receives in addition the “Medical News aud Library,” making in all about 1500 large octavo pages per annum, free of postage. II. THE MEDICAL NEWS AND LIBRARY is a monthly periodical of Thirty-two large octavo pages, making 384 pages per annum. Its “Library Department” is devoted to publishing standard works on the various branches of medical science, paged separately, so that they can be detached for binding, when complete. In this manner subscribers have received, without ex- pense, such works as “Watson’s Practice,” “West on Children,” “Malgaigne’s Surgery,” “Stokes on Fever,” Gosselin’s “Clinical Lectures on Surgery,” and many other volumes of the highest reputation and usefulness. With July, 1878, was commenced the publication of “Lectures on Diseases of the Nervous System,” by J. M. Charcot, Professor in the Faculty of Medicine of Paris, translated from the French by George Sigerson, M.D., Lecturer on Biology, etc., Catholic Univ. of * Communications are invited from gentlemen in all parts of the country. Elaborate articles inserted by the Editor are paid for by the Publisher. 3 Henry C. Lea’s Publications — (Am. Journ. Med. Sciences). Ireland [see p. 17), which will be continued to completion during 1879. New sub- scribers, commencing with January, 1879, can procure the previous portion by a remittance of 50 cents, if promptly made. The “News Department” of the “Medical News and Library” presents the current information of the month, with Clinical Lectures and Hospital Gleanings. A new and attractive feature of this will be found in an elaborate series of Original American Clinical Lectures, specially contributed to the News by gentlemen of the highest reputation in the profession throughout the United States. During 1878 there have appeared Lectures by S. D. Gross, M.D., Prof, of Surgery, Jefferson Med. Coll., Philada. T. Gaillard Thomas, M.D., Prof. Obstetrics, &c.. Coll. Phys. and Surg., N. Y. William Pepper, M.D., Prof. Clin. Medicine, Univ. of Penna. Lewis A. Sayre, M.D., Prof. Orthopaedic Surg., Bellevue Hosp.Med. Coll., N Y. Roberts Bartholow, M.D., Prof. 'Pheory and Practice of Med., Med. Coll, of Ohio. T. G. Richardson, M.D., Prof. Genl. and Clin. Surg., Univ. of La., New Orleans. S. W. Gross, M.D., Surg. to Philada. Hospital. F. Peyre Porcher, M.D., Prof, of Mat. Med. and Clin. Medicine, Med. Coll, of S. C. William Goodell, M.D., Prof. Clin. Gynaecology, Univ. of Penna. N. S. Davis, M.D., Prof. Prin, and Prac. of Med., Chicago Med. Coll. W. H. Van Buren, M.D., Prof. Surgery, Bellevue Hosp. Med. Coll., N. Y. To be followed by others of similar value from Austin Flint, M.D., Prof. Prin. and Prac, of Med., Bellevue Hosp. Med. Coll., N.Y. Fordyce Barker, M.D., Prof. Clin. Midwifery, &c., Bellevue H osp. Med. Coll, N.Y. L. a. Duhring, M.D., Clin. Prof, of Diseases of the Skin, Univ. of Penna. J'heophilus Parvin.M.D., Prof. Obstetrics, &c.. Coll. Phys. and Surg., Indianapolis. J. P. White, M.D., Prof, of Obstetrics, &c., Univ. of Buffalo. John Ashhurst, Jr., M.D., Prof, of Clin. Surg., Univ. of Penna. D. Warren Brickell, M.D., Prof. Obstetrics, &c.. Charity Hosp. Med Coll., N. O. J, Lewis Smith, M.D., Clin. Lee. on Dis, of Chil., Bellevue Hosp. Med. Coll., N. Y. William F. Norris, M.D., Clio. Prof, of Diseases of the Eye. Univ. of Penna. P. S. Conner, M.D., Prof, of Anat. and Clin. Surgery, Med. Coll, of Ohio, Cin. S. Weir Mitchell, M.D., Phys. to the Infirmary for Nervous Diseases, Philada. J. M. DaCosta, M.D., Prof. Prin. and Prac. of Med., Jeff. Med. Coll., Philada. Thomas G. Morton, M.D., Surgeon to Penna, Hospital, Philada. F. J. Bumstead, M.D., late Prof, of Venereal Dis., Coll. Phys. and Surg., N. Y, J. H. Hutchinson, M.D,, Physician to Penna. Hospital. Christopher Johnson, M.D., Prof, of Surgery, Univ. of Md.. Baltimore. William Thomson, M.D., Lecturer on Ophthalmology, Jeff. Med, Coll., Philada. With contributors such as these, representing every portion of the Uiiited States, the publisher feels safe in promising to the subscriber a series of practical lectures unsurpassed in variety, interest, and value. As stated above, the subscription price of the “Medical News and Library” is One Dollar per annum in advance ; and it is furnished without charge to all advance- paying subscribers lo the “American Journal of the Medical Sciences.” III. THE MONTHLY ABSTRACT OF MEDICAL SCIENCE is issued on the first of every month, each number containing forty-eight large octavo pages, thus furnishing in the course of the year about six hundred pages, 'i’he aim of the “ Abstract” is to present— without duplicating the matter in the “Journal” and “News” — a careful condensation of all that is new and important in the medical journalism of the world, and all the prominent professional periodicals of both hemi- spheres are at the disposal of the Editors. To show the manner in which this plan has been carried out it is sufficient to state that during the year 1878 it contained 30 Articles on Anotoniy and l^ltysioUupj. 5ti “ “ Materia Medica and T/ierapeiitics, 230 ‘‘ Medicine. 151 “ ‘‘ Surye/ry. 70 “ Midkciferjf and Gytnecoloyy. 12 Medical Jurispradence and Toxicology — making in all 558 articles in a single year. The subscription to the “Monthly Abstract,” free of postage, is Two Dollars and a Half a year, in advance. As stated above, however, it will be supplied in conjunction with the “American Journal of the Medical Sciences” and the “Medical News and Library,” making in all about Twenty-one Hundred pages per annum, the whole /ree of postage, for Six Dollars a year, in advance. In this effort to bring so large an amount of practical information within the reach of every member of the profession, the publisher confi lently anticipates the friendly 4 Henry C. Lea’s Publications — {Dictionaries). aid of all who are interested in the dissemination of sound medical literature. He trusts, especially, that the subscribers to the “American Medical Journal” will call the attention of their acquaintances to the advantages thus offered, and that he will be sustained in the endeavor to permanently establish medical periodical literature on a footing of cheapness never heretofore attempted. PKEMIUM rOE OBTAINING NEW SUBSOEIBEES TO THE "JOUENAL.” Any gentleman who will remit the amount for two subscriptions for 1879, one of which must be for a neiv fnihsc/nher, will receive as a premium, free by mail, a copy of “ Holden’s Landmarks, Medical and Surgical” (for advertisement of which see p. 6), or of Fothergill’s “ Antagonism of Medicines” (see p. 16), or of “ Browne on THE Use of the Ophthalmoscope” (seep. *29), or of “ Flint’s Essays on Conservative Medicine” (see p. 15), or of “Sturges’s Clinical Medicine” (see p. 14), or of the new edition of “Swayne’s Obstetric Aphorisms” (see p. 21), or of “Tanner’s Clinical Manual” (see p. 5), or of “Chambers’s Restorative Medicine” (see p. 18), or of “West on Nervous Disorders of Children” (see p. 20). Gentlemen desiring to avail themselves of the advantages thus offered will do well to forward their subscriptions at an early day, in order to insure the receipt of complete sets for the year 1879. The safest mode of remittance is by bank check or postal money order, drawn to the order of the undersigned. Where these are not accessible, remittances for the “Journal” may be made at the risk of the publisher, by forwarding in registered letters. Address, HENRY C. LEA, Nos. 706 and 708 Sansom St., Philadelphia, Pa. jnUNGLISON [ROBLEY], M.D., Late Professorof Institutes of Medieinein Jefferson Medical College, Philadelphia. MEDICAL LEXICON; A Dictionary of Medical Science: Con- taining a concise explanation of the various Subjects and Terms of Anatomy, Physiology, Pathology, Hygiene, Therapeutics. Pharmacology, Pharmacy, Surgery, Obstetrics, Medical Jurisprudence, and Dentistry. Notices of Climate and of Mineral Waters; Formulae for Officinal, Empirical, and Dietetic Preparations; with the Accentuation and Etymology of the Terms, and the French and other Synonymes ; so as to constitute a French as well as English Medical Lexicon. A New Edition. Thoroughly Revised, and very greatly Mod- ified and Augmented. By Richard J. Dunglison, M.D. In one very large and hand- someroyaloctavo volume of over 1100 pages. Cloth, $6 50 ; leather, raised bands, $7 50. iJust Issued.) The object of the author from the outset has not been to make the work a mere lexicon or dictionary of terms, but to afford, undereach, a condensed view of its various medical relations, and thus to render the work an epitome of the existing condition of medical science. Starting with this view, the immense demand which has existed for the work has enabled him, in repeated revisions, to augment its completeness and usefulness, until at length it has attained the position of a recognized and standard authority wherever the language is spoken. Special pains have been taken in the preparation of the present edition to maintain this en • viable reputation. During the ten years which have elapsed since the last revision, the additions to the nomenclature of the medical sciences have been greater than perhaps in any similar period of the past, and up to the time of his death the author labored assiduously to incorporate every- thing requiring the attention of the student or practitioner. Since then, the editor has been equally industrious, so that the additions to the vocabulary are more numerous than in any pre- vious revision. Especial attention has been bestowed on the accentuation, which will be found marked on every word. The typigraphical arrangement has been much improved, rendering reference much more easy, and every care has been taken with the mechanical execution. The work has been printed on new type, small but exceedingly clear, with an enlarged page, so that the additions have been incorporated with an increase of but little over a hundred pages, and the volume now contains the matter of at least four ordinary octavos. A book well known to our readers, and of which every American ought to be proud. When the learned author of the work pas.sed away, probably all of us feared lest the book should not maintain its place in the advancing science whose terms it defines. For- tunately, Dr. Richard J. Dunglison, having assisted his father in the revision of several editions of the work, and having been, therefore, trained in the methods and imbued with the spirit of the book, has been able to edit it. not in the patchwork manner so dear to the heart of book editors, so repulsive to the taste of intel- ligent book readers, but to edit it as a work of the kind should be edited — to carry it on steadily, without jar or interruption, along the grooves of thought it has travelled during its lifetime. To show the magnitude of the task which Dr. Dunglison has assumed and car- ried through, it is only necessary to stale that more than six thousand new subjects have been .added in the presentedition. — Diila. Med. Times, Jan. 3, 1874. About the first book purchased by the medical stu- dent is the Medical Dictionary. The lexicon explana- tory of technical terms is simply a sine qua non. In a ' science so extensive, and with such collaterals as medi- cine, it is as much a necessity also to the practising physician. To meet the wants of students and most physicians, the dictionary must be condensed while comprehensive, and practical while perspicacious. It svas because Dunglison’s met the.se indications that it became at once the dictionary of general use wherever medicine was studied in the English language. In no former revision have the alterations and additions been ^0 great. More than six tliousand new subjects and terms have been added. The chief terms have been set in black letter, while the derivatives follow in small caps; an arr.angement which greatly facilitates reference. We may safely confirm the hope ventured by the editor that the work, which possesses for him a filial as well as an individual interest, will be found worthy a con- tinuance of the po.sition so long accorded to it as a standard authority .” — Cincinnati Clinic, Jan. 10, 1874. It has the rare merit that it certainly has no rival in the English language for accuracy and extent of references . — London Medical Gazette. Henry C. Lea’s Publications — {Manuals), 5 A CENTURY OF AMERICAN MEDICINE, 1776-1876. By Doctors K. H. Clarke, H. J. Bigelow, S. D. Gross,!'. G. Thomas, andJ. S. Billings. In one very hand- some 12mo. volume of about 360 pages : cloth, $2 26. (Just Ready.) This work appeared in the pages of the American Journal of the Medical Sciencesduring the year 1876. As a detailed account of the development of medical science in America, by gentle- men of the highest authority in their respective departments, the profession will no doubt wel- come it in a form adapted for preservation and reference. TJOBLYN [RICHARD D.), M.D. ^ A DICTIONARY OF THE TERMS USED IN MEDICINE A]S D THE COLLATERAL SCIENCES. Revised, with numerous additions, by Isaac Bays, M. D., Editor of the “American Journal of the Medical Sciences.” In one large royal 12mo. volume of over 500 double-columned pages ; cloth, SI 60 ; leather, $2 00 It is the best book of defiaitions we have, aud ought always to be upon the student’s t&hle.— Southern Med. and Surg. Journal. IDOD WELL [G. F.), F.R.A.S., A DICTIONARY OF SCIENCE: Comprising Astronomy^, Chem- istry, Dynamics, Electricity, Heat, Hydrodynamics, Hydrostatics, Light, Magnetism, Mechanics, Meteorology, Pneumatics, Sound, and Statics. Preceded by an Essay on the History of the Physical Sciences. In one handsome octavo volume of 694 pages, and many illustrations : cloth, $6. J^EILL [JOHN), M.D., and JQMITH [FRANCIS G.), M.D., ' Prof, of the Institutes of Medicine in the Univ. of Pennc. AN ANALYTICAL COMPENDIUM OF THE VARIOUS BRANCHES OF MEDICAL SCIENCE ; for the Use and Examination of Students. A new edition, revised and improved. In one very large and handsomely printed royal 12m o volume, of about one thousand pages, with 374 wood-cuts, cloth, $4 ; strongly bound in leather, with raised bands, $4 75. ^ARTSHORNE [HENRY), M.D., Professor of Hygiene in the University of Pennsylvania . A CONSPECTUS OF THE MEDICAL SCIENCES; containing Handbooks on Anatomy, Physiology, Chemistry, Materia Medica, Practical Medicine, Surgery, and Obstetrics. Second Edition, thoroughly revised and improved. In one large royal 12mo. volume of more than 1000 closely printed pages, with 477 illustrations on wood. Cloth, $4 25 ; leather, $5 00. (Lately Issued.) We can say with the strictest truth that it is the best work of the kind with which we areacqnainted. It embodies ina condensed form all recent contribu- tions to practical medicine, aud is therefore useful to every busy practitioner throughout our country, besides being admirably adapted to the use of stu- dents of medicine. The book is faithfully and ably executed. — Charleston Med. Journ., April, 1875, The work is intended as an aid to the medical stuient, and as such appears to admirably fulfil its object by itsexcellent arrangement, the full compi- lation of facts, the perspicuity aud terseness of lan- guage, and the clear aud instructive illustrations in some parts of the work — American Journ. of Pharmacy, Philadelphia, July, 1874. The volume will be found useful, not only to stu- dents, but to many others who may desire to refresh their memories with the smallest possible expendi- ture of time. — N. Y. Med. Journal, Sept. 1874. The student will find this the most convenient and useful book of the kind on which he can lay his hand. — Pacific Med. and Surg. Journ., Aug. 1874. This is the best book of its kind that we have ever examined. It is an honest, accurate, and concise compend of medical sciences, as fairly as possible representing their present condition. The changes and the additions have been so judicious and tho- rough as to render it, so far as it goes 'entirely trust- worthy. If students must have a conspectus, they will be wise to procure that of Dr. Hartshorne. — Detroit Rev. of Med. and Pharm., Aug. 1874. rUDLOW[J.L.), M.D. A MANUAL OF EXAMINATIONS upon Anatomy, Physiology, Surgery, Practice of Medicine, Obstetrics, Materia Medica, Chemistry, Pharmacy, and Therapeutics. To which is added a Medical Formulary. Third edition, thoroughly revised and greatly extended and enlarged. With 370 illustrations. In one handsome royal 12mo. volume of 816 large pages, cloth, $3 25 ; leather, $3 75. The arrangement of this volume in the form of question and answer renders it especially suit- able for the office examination of -students, and for those preparing for graduation. rPANNER [THOMAS HAWKES), M.D., A MANUAL OF CLINICAL MEDICINE AND PHYSICAL DIAG- NOSIS. Third American from the Second London Edition. Revised and. Enlarged by Tilbury Fox, M. D., Physician to the Skin Department in University College Hospitay Ac. In one neat volume small 1 2mo., of about 375 p.iges, cloth, $150. On paged, it will be seen that this work is offered as a premium for procuring new subscribers to the “American Journal of the Medical Sciences.” 6 Henry C. Lea’s Publications— (H na^omy). QR^Y {HENRY), F.R.S., Lteturer on Anatomy at St. George's Hospital, London. ANATOMY, DESCRIPTIVE AND SURGICAL. The Drawings by H. V . Carter, M.D., and Dr. Westmacott. The Dissectionsjointly by the Author and Dr. Carter. With an Introduction on General Anatomy and Development by T. Holmes, M.A., Surgeon to St. George’s Hospital. A new American, from the eighth enlargec and improved London edition. To which is added “ Landmarks, Medical and Surgical,” by Luther Holden, F.R C.S., author of “ Human Osteology,” “A Manual of Dissections,” etc. In one magnificent imperial octavo volume of 983 pages, with 522 large and elaborate engravings on^ wood. Cloth, $6; leather, raised bands, $7, {Just Ready.) The author has endeavored in this work to cover a more extendedrange ofsubjectsthan is cus- tomary in the ordinary text-books, by giving not only the details necessary for the student, but also the application of those details in the practice of medicine and surgery, thdsrendering it both a guide for the learner, and an admirable work of reference for the active practitioner. The en- gravings form a special feature in the work, many of them being the size of nature, nearly all original, and having the names of the various parts printed on the body of the cut, in place of figures of reference, with descriptions at the foot. They thus form a complete and splendid series, which will greatly assist the student in obtaining a clear idea of Anatomy, and will also serve to refresh the memory of those who may find in the exigencies of practice the necessity of recalling the details of the dissecting room ; while combining, as it does, a complete Atlas of Anatomy, with a thorough treatise on systematic, descriptive, and applied Anatomy, the work will be found of essential use to all physicians who receive students in their offices, relieving both preceptor and pupil of much labor in laying the groundwork of a thorough medical education. Since the appearance of the last American Edition, the work has received three revisions at the hands of its accomplished editor, Mr. Holmes, who has sedulously introduced whatever has seemed requisite to maintain its reputation as a complete and authority *ive standard text-book and work of reference. Still further to increase its usefulness, there has been appended to it the recent work by the distinguished nnatomist, Mr. Luther Holden — “Landmarks, Medical and Surgical” — which gives in a clear, condensed, and systematic way, all the information by which the prac- titioner can determine from the external surfnce of the body the position of internal parts. Thus complete, the work, it is believed, will furnish all the assistance that can be rendered by type and illustration in anatomical study. No pains have been spared in the typographical execution of the volume, which will be found in all respects superior to former issues. Notwithstanding the increase of size, amounting to over 100 pages and 57 illustrations, it will be kept, as heretofore, at a price rendering it one of the cheapest works ever offered to the American profession. The recent work of Mr. Holden, which was no- ticed hy us on p. 53 of this volume, has been added as an appendix, so that, altogether, this is the moit nractical and complete anatomical treatise available to American students and phy.sicians. The former finds in it the necessary guide in making dissec- tions ; a very comprehensive chapter on minute anatomy ; and about all that can be taught him on general and special anatomy; while the latter, in its treatment of each region from a surgical point of view, and in the valuable edition of Mr Holden, will find all that will be essential to him in his practice. — New Remedies, Aug 1878. This work is as near perfection as one could pos- sibly or reasonably expect any book intended as a text-book or a general reference hook on anatomy to be. The American publisher deserves the thanks of the profession for appending the recent work of Mr. Holden, "Landmarks, Medical and Surgical," which has already been commended as a separate book. The latter work— treating of topographical anatomy — has become an essential to the library of every intelligent practitioner. We know of no hook that can take its place, written as it is by a most distinguished anatomist. It would be simply a waste of words to say anything further in praise of Gray’s Anatomy, the text-book in almost every medical college in’this country, and the daily refer ence book of every practitioner who has occasion to consult his hooks on anatomy. The work is simply indispensable, especially this present Amer- ican edition.— Va. Med. Monthly, Sept. 1878. The addition of the recent work of Mr. Holden, as an appendix, renders this the most practical and complete treatise available to American student-s, who find in it a comprehensive chapter on minute anatomy, about all that can be taught on general and special anatomy, while its treatment of each region, from a surgical point of viev, in the valu- able section hy Mr Holden. is all that will he essen- tial to them in practice.— OAio Mtdical Recorder, Aug 1878. It is difficult to speak in moderate terms of this new edition of ‘‘ Gray.” It seems to be as nearly perfect as it is possible to make a book devoted to any branch of medical science. The labors of the eminent men who have successively revised the eight editions through which it has passed, would seem to leave nothing for future editors to do. The addition of Holden’s “ Landmarks” will make it as indispensable to the practitioner of medicine and surgery as it has been heretofore to the student. As regards completeness, ease of reference, utility, beauty, and cheapness, it has no rival. No stu- dent should enter a medical school without it ; no physician can afford to have it absent from his library — St. Louis Clin. Record, Sept. 1878. Also for sale separate — TTOLDEN {LUTHER), F.R.C.S., Surgeon to St. Bartholomew’’ s and the Foundlin g Hospitals. LANDMARKS, MEDICAL AND SURGICAL. From the 2d London Ed. In one handsome volume, royal l2mo., of 128 pages : cloth, 88 cents. {Now Ready.) The title of this book is very suggestive of its practical value, while the perusal of the work itself verifies the most extravagant expectations. The o-bject of the author has been to collect in compact fo rm the landmarks, or surface-inai ks ofthe difl'erent parts of the body, and indicate their relation to the deeper-seated parts. The value of thissortof know- ledge to the physician, hut especially to the surgeon who, with auHiomical eye, can make the tissues transparent before him, is incalculable. The map- ping out of the human body is one which is most in- structive to the practical man, and he is enabled, after considerable experience, to have landmarks of his own; 1 ut in the little work be'ore us this knowledge is systematized in such an intelligible manner as to {)lace it within the reach of all. It is one of the most interesting lit tie works wehave seen for a long time.— A'. T. Med. Record, May 11, 1878. Henry C. Lea’s Publications — (^Anatomy'). 1 A LLEN {HARRISON), M.D. Pr('fe.S!w to teach practical medicine. The charm of sim- plicity is not the least in teresting feature in the man- ner in which Dr. Fenwickconveysinstruction. There are few books of this sizeon practical medicine that contain so much and convey it so well as c he volume before us. It is a book we can sincerely recommend to the student for direotinstruction, and to the|prac- titioner as a ready and useful aid to his memory. — Am. Journ. of Syphilography, Jan. 1874. (IREEN [T. HENRY), M.D., Lecturer on Pathology and Morbid. Anatomy at Charing-Cross Hospital Medical School, etc. PATHOLOGY AND MORBID ANATOMY. Third Aniericiin, from the Fourth and Enlarged and Revised English Edition. In one very handsome octavo volume of 332 pages, with 132 illustrations j cloth, $2 25. {Just Ready.) This is unquestionably one of the best manuals on the subject of pathology and morbid anatomy that can be placed in the student’s hands, and we are glad to see it kept up to the times by new editions. Each edition is carefully revised by the author, with the view of making it include the most recent ad- vances in pathology, and of omitting whatever may have become obsolete. — N. Y. Med. Jour., Feb. 1879. The treatise of Dr. Green is compact, clearly ex- pressed, up to the times, and popular as a text-book, both in England and America. The cuts are suffi- ciently numerous, and usual y well made. In the present edition, such new matter has been added as was necessary to embrace the later results in patho- logical research. No doubt it will continue to enjoy the favor it has received at the hands of the profes- sion.— Jfed and Surg. Reporter, Feb. 1, 1879. For practical, ordinary daily use, this is undoubt- edly the best treatise that is offered to students of pathology and morbid anatomy. — Cincinnati Lan- cet and Clinic, Feb. 8, 1879. T)AVIS [NATHAN S.), Prof, of Principles and Practice of Medicine, etc., in Chicago Med. College. CLINICAL LECTURES ON VARIOUS IMPORTANT DISEASES; being acollection of the Clinical Lectures delivered in the Medical Wards of Mercy Hos- pital, Chicago. Edited by Frank H. Davis, M.D. Second edition, enlarged. In one handsome royal 12mo. volume. Cloth, $1 75. {Lately Issued.) WHAT TO OBSERVE ATTHE BEDSIDE and AFTER Death in Medical Cases. From the second Lon- don edition. 1 vol royal 12mo., cloth. $100. CH RISTISON’S DISPENSATORY. With copious ad- ditions, and 213 large wood-engravings. By R. EulesfieldGbiffith, M.D. One vol. 8vo., pp. ILOO. cloth. $4 00. CARPENTER’S PRIZE ESSAY ON THE USE OF Alcoholic Liquors in Health and Disease. Nev edition, with a Preface by D. F. Condie, M.D., and explanations of scientificword? . In oneneatI2mc. volume, pp. 178, cloth. 60 cents. GLUGE’S ATLAS of PATHOLOGICAL HISTOLOGY Translated, with Notes and Additions, by Joseph Leidt, M. D. In one volume, very large imperial quarto, with 320 copper-plate figures, plain and colored, cloth. $4 00. LA ROCHE ON YELLOW FEVER, considered in its Historical, Pathological. Etiological, and Thera peutical Relations. In two large and handsome octavo volumes of nearly l.'iOO pp , cloth. $7 00. HOLLAND’S MEDICAL NOTES AND REFLEC- TIONS. 1 vol. 8vo., pp. 500, cloth. $3 50. BARLOW’S MANUAL OF THE PRACTICE OF MEDICINE. With Additions by D. F. Condie, M D. 1 vol. 8vo., pp. 600, cloth. |2 50. TODD’S CLINICAL LECTURES on CERTAIN ACUTE Diseases. In one neat octavo volume, of 320 pp , cloth. $2 50. STURGES'S INTRODUCTION TO THE STUDY OF CLINICAL MEDICINE. Being a Guide to the In- vestigRtion of Disease. In one handsome 12mo. volume, cloth, $1 2.5. {Lately Issxied.) STOKES’ LECTURES ON FEVER. Edited by John William Moore, M. I)., Assistant Physician to the Cork Street Fever Hospital. In one neat Svo. volume, cloth, $2 00. {Just Issued.) THE CYCLOPEDIA OF PRACTICAL MEDICINE: comprising Treatises on the Nature and Treatment of Diseases, Materia Medica and Therapeutics, Dis- eases of Women and Children, Medical Jurispru- dence, etc. etc. By Dunglison, Forbes, Tweedie, and CONOLLV. In four large super royal octavo volumes, of 3254 double columned pages, strongly and handsomely bound in leather, $15; cloth, $tl. 15 Henry C. Lea’s Publications — {Practice of Medicine). ipLINT {A USTIN), M.D., M Professor of the Principles and Practice of Medicine in Bellevue Med. College, N.Y. A TREATISE ON THE PRINCIPLES AND PRACTICE OF MEDICINE ; designed for the use of Students and Practitioners of Medicine. Fourth edition, revised and enlarged. In one large and closely printed octavo volume of about 1100 pp.; cloth, $6 00 ; or strongly bound in leather, with raised bands, $7 00. il.ately Issued. ) By common consent of the English and American medical press, this work has been assigned to the highest position as a complete and compendious text-book on the most advanced condi- tion of medical science. At the very moderate price at which it is offered it will be found one of the cheapest volumes now before the profession. This excellent treatise on medicine has acquired for itsel fin the United States a reputation .similar to that enjoyed in England by the admirable lectures of Sir Thomas Watson. It may not possess the same charm of style,batitha8 like solidity, the fruit of long and patient observation, and presents kindred moderation and eclecticism. We have referred to mauyofthe most important chapters, andfindthere- vision spoken of in the preface is a genuine one, and that the author has very fairly brought up his matter to the level of the knowledge of the present day. The work has this great recommendation, that it is in one volume, and therefore will not be so terrifying to the student as the bulky volumes which several of our English text-books of medicine have developed into. — British and Foreign Med.-Chir. Rev., Jan. 187 {>. It is of course unnecessary toint reduce or eulogize this now standard treatise. All the colleges recom- mend it as a text-book, and there are few libraries in which one of its editions isnottobe found. Tie present edition has been enlarged and revised to bring it up to the author’s present level of experi- ence and reading. Hisown clinical studiesand the latest contributions to medical literature boih in this country and in Europe, have received careful attention, .‘■o that some portions have been entirel y rewritten, and about seventy pages of new matter have been added. — Chicago Med Jour., June, 1 873. Has never been surpassed as a text-book for stu- dents and a book of ready reference for practition- ers The force of its logic, its simple and practical teachings, have left it without a rival in the field. N. Y.—Med. Record, Sept. 15, 1874. It is given to very few men to tread in the steps of Austin Flint, whose single volume on medicine, though here and there defective, is a masterpiece of lucid condensation and of general grasp of an enor- mously wide subject — Lond. Practitioner, Dec.'TS. ^Y THE SAME AUTHOR. CLINICAL MEDICINE; a Systematic Treatise on the Diagnosis nnd Treatment of Diseases. Designed for Students and Practitioners of Medicine. In one large and handsome octavo volume. (J/t Press ) ^Y THE SAME AUTHOR. ESSAYS ON CONSERYATIYE MROICINE AND KINDRED TOPICS. In one very handsome royal l2rao. volume. Cloth, $1 38. {Just Issued.) ^TOODBURY [FRANK), M.D., ' ’ Physician to the German Hospital, Philadelphia,, late Physician to the Out-patient Departmeid of the Jeff. College Hospital, etc. A HANDBOOK OF THE PRINCIPLES AND PRACTICE OF Medicine ; for the use of Students and Practitioners. Based upon Husband’s Handbook of PracticL In one neat volume, royal 12mo. {Li Press.) fJARTSHORNE [HENRY), M.D., Professor of Hygiene in the UniversUy of Pennsylvania. ESSENTIALS OP THE PRINCIPLES AND PRACTICE OP MEI I- CINE. A handy-book forStudents and Practitioners. Fourth edition, revi.'ed and im- proved. With about one hundred illustrations. In one handsome royal 1 2mo volume, of about 550 pages, cloth, $2 63 ; half bound, $2 88. {Lately Issued.) As ahandbook, whichclearly sets forth the essen- tials of the PRINCIPLES AND PRACTICE OP MEDICINE, we do not know of its equal.— Va. Med. Monthly. As a brief, condensed, but comprehensive hand- book, it cannot be improved upon. — Chicago Med. Examiner, Nov. 15, 1874. Without doubt the best book of the kind published in the English language. — St. Louis Med. and Surg . Journ., Nov. 1874. ^ATSON [THOMAS], M.D., ^c. LECTURES ON THE PRINCIPLES AND PRACTICE OF PHYSIC. Delivered at King’s College, London. A new American, from the Fifth re- vised and enlarged English edition. Edited, with additions, and several hundred illustra- tions, by Henry Hartshorne, M.D., Professor of Hygiene in the University of Penn- sylvania. In two large and handsome 8vo. vols. Cloth, $9 00 ; leather, $11 00. {Lately Published.) is a subject for congratulation and for thank- fnlaesB that Sir Thomas Watson, during a period of comparative leisure, after a long, laborious, and most honorableprofessional career, while retaining full possession of his high mental faculties, should have employed the opportunity to submit his Lec- tures toa more thorough revisionthan wa possible during the earlier and busier period of hie life. Carefully passing in review some of the most intri- cate and important pathological and practical ques- tions, the results of his clear insight and his calm judgment are now recorded for the benefit of man- kind, in language which, for precision, vigor, and classical elegance, has rarely been equalled, and never surpassed The revision has evidently been most carefully done, and the results appear in al- most every page. — Brit. Med. Journ., Oct. 14, 1871. 16 Henry C. Lea’s Publications— (P rach'cf^ of 3Iedici7ie). B RISTOWE [JOHN SYER), M.D , F.R.C.P., Physician and Joint Lecturer on Medicine, St. Thomas's Hospital. A MANUAL ON THE PRACTICE OP MEDICINE. Edited, with Additions, by James H. IIuichinson, M.D., Physician to the Penna. Hospital. In one handsome octavo volume of over 1100 pages : cloth, $5 50; leather, $6 50. [j^tst Issued.) This portly volume is a model of coudensation. In a style at once clear, interesting, and concise, Dr. Bristowe passes in review every conceivable subject connected with the practice of medicine. Those practitioners who purchase few books will find this a most opportune publication, because so many top- ics not usually embraced in a work on practice are adequately handled. The book is a thoroughly good one, and its usefulness to American readers has been increased by the judicious notes of the Editor. — Cincinnati Clinic, Jan 7, 1877. Anyone who wants a good, clear, condensed work upon Practice, quite up with the most recent views in pathology, will find this a most valuable work The additions made by Dr. Hutchinson are appropiiate and useful, andso well done that we wish there were more of them.— Am. Practitioner, Feb. 1877. fJABERSHON (S. 0.). M.D. J-J- Senior Physician to and late Lecturer on the Principles and Practice of Medicine at Guy's Hospital, etc. ON THE DISEASES OF THE ABDOMEN, COMPRISING THOSE of the Stomach, and other parts of the Alimentary Canal, (Esophagus, Caecum, Intes- tines, and Peritoneum. Second American, from the third enlarged and revised Eng- lish edition. With illustrations. In one handsome octavo volume of over 500 pages. Cloth, $3 50. {Notv Ready.) This work has remained s )me time out of print owing to the careful and conscientious revision which it has enjoyed at the hands of the author, and which has nearly doubled its size since the appearance of the first edition. Yet there is no work accessible to the profession to take its place, as a careful, practical guide on a class of diseases, which form so large and important a portion of the duties of the physician, and for which the author’s position has given him almost unequalled opportunities for observation and experience. The very extensive scope of the volume will be seen by the subjoined condensed SUMMARY OF CONTENTS. Chapter I. Introduction. II. On Diseases of the Tongue and Mouth. III. On Diseases of the Pharynx. IV. On diseases of the (Esophagus. V On Organic Diseases of the Stomach. VI. On Functional Diseases of the Stomach. VII. On Diseases of the Duodenum VIII. On Muco-Enteritis and Enteritis. IK. On Strumous and Tubercular Disease of the Alimen- tary Canal ; Lardaceous Disease. X. On Diseases of the Caecum and Appendix Caeci. XI. On Diarrhoea. XII. On Dysentery and Catarrhal Inflammation of the Colon. XIII. On Typhoid Disease of the Intestine. XIV. On Colic. XV. On Constipation. XVI. On Organic Obstruction, Internal Strangulation, Intussusception, and Carcinoma of Intestine. XVlI. On Suppuration of the Abdominal Parietes, Perforation of the Intestine from without, and Abscess of the Abdominal Parietes extending into the Intestine; Fecal Abscess. XVIII. On intestinal Worms. XIX. On Peritonitis. XX. On Ascites, Dropsy. XKI. On Abdomi- nal Tumors. Thi.s valuable treatise on diseases of the stomach and abdomen has been out of priutfor several years, and is thei’efore not so well known to the profession as it deserves to be. It will be found a cyclopedia of information, systematically arranged, on all dis- eases of the alimentary tract, from the mouth to the rectum. A fair proportion of each chapter is dev)t- ed to symptoms, pathology, and therapeutics. The present edition is fuller than former ones in many particulars, and has been thoroughly revised and amended by the author. Several new chapters have been added, bringing the work fully up to the times, and making it a volume of interest to the practitioner in every field of medicine and surgery. Perverted nutrition is in some form associated with all diseases we have to combat, and we need all the light that can be obtained on a subject so broad and general. Dr Habershon’s work is one that every practiti'^ner should read and study for himself. — N. Y. Med. Journ., April, 1879. JfOTHERGJLL [J. MILNER), M.D. Edin., M.R.C.P. bond., J- Asst. Phys. to the West Land. Hasp. ; Asst. Phys. to the City of Land. Ho.9p.,etc. THE PRACTITIONER’S HANDBOOK OF TREATMENT; Or, the Principles of Therapeutics. In one very neat octavo volume of about 550 pages : cloth, $4 00. {Now Ready.) Our friends will find this a very readable book ; and that it sheds light upon every theme it touches, causing the practitioner to feel more certain of his diagnosis in ditficult cases. We confidently commend the work to our readers as one worthy of careful perusal. It lights the way over obscure and difficult passes in medical practice. The chapter on the circulation of the blood is the most exhaustive and instructive to be found. It is a book every practitioner needs, and would have, if he knew how suggestive and helpful it would be to him.— (S'!. Louis Med. and Surg. Journ , April, 1877. It is our honest conviction, after a careful permsal of this goodly octavo, that it represents a great amount of earnest thought and painstaking work, and is therefore one of those books which both deserve and are likely to survive. This book, although written ostensibly for the young and inexperienced, may be very profitably studied by those who have been practising tbeir profession more or less empirically for thirty or forty years. We content ourselves with again recommending the book very cordially. — Edin. Med. Journ., Jan. 1S77. We heartily commend his book to themedical student as an honest and intelligent guide through the mazes of therapeutics, and assure the practitioner who has grown gray in the harness that be will derive pleasure and in- struction from its perusal. Valuable suggestions and material for thought abound throughout.— Boston Med. and Surg Journal, Mar 8, 1877. -nr THE SAME AUTHOR. THE ANTAGONISM OF THERAPEUTIC AGENTS, AND WHAT IT TEACHES. Being the Fothergillian Prize Essay for 1878. In one neat volume, royal 12mo. of 156 pages; cloth, $1 00. {Just Ready.) It will be found a highly interesting study and I certain drugs. — Medical and Surgical Reporter, practical application of the antagonistic action of 1 Sept. 11, 1876. Henry C. Lea’s Publications — (Practice of Medicine). n JflNLATSOy [JAMES), Af.D., Phi/.fici an a'”d Lecturer on Clinical MedtHne in. ih" Glasgniv Western Infirmary, etc. CLINICAL DIAGNOSIS; A Hnndhook for Students and Prac- titioners of Medicine. In one handsome 12mo. volume, of 546 pages, with 85 illustra- tions. Cloth, $2 6.3. {Jnst Ready.) The concurrence of gentlemen specially familiar with the several subjects being requisite to the siitisfactory development of a plan so extensive, Dr. Finlayson has secured the co-operation of Prof. Gairdner, who has contributed the chapter on the Physiognomy of Disease ; Prof. Wra. Stephenson that on Disorders of the Female Organs; Dr. Alex. Robertson that on Insanity; Prof. Samson Gemmell those on the Sphygmograph and Physical Diagnosis; and Dr. Joseph Coates those on the Fauces, Larynx, and Nares, and on the method of post-mortem examinations. Other chapters have enjoyed the advantage of revision by gentlemen specially versed in their several subjects; and the volume is presented as thoroughly on a level with the most advanced condition of knowledge in a department which has made such rapid strides of advancement within the last few years. The book is an excellent one, clear, concise, conve- nient, practical. It is replete with the very know- ledge the student needs when he quits the lecture- room and the laboratory for the ward and sick-room, and does not lack in information that will meet the wants of experienced and older men. — Phila. Med. Times, Jan. 4, 1879. The aim of the author is to teach a student and practitioner how to examine a case so as to use “aiZ his knowledge" in arriving at a diagnosis. All the various symptoms of the several systems are grouped together in such a manner as to mike their relations to a final diagnosis clear and easy of apprehension. This work has been done by men of large experience and trained observation, who have been long recog- nized as authorities upon the subj.cts which they treat. There is a profusion of illustrations to illus- trate subjects under discussion. The application of electricity, and instruments of precision in diagnosis, is fully discussed. This book is all good. We com- mend it to all students and praciitioner.s of medicine as a work worthy of a place in their libraries. — Ohio Med. Recorder, Dec. 1878. This is one of the really useful books. It is attrac- tive from pn'face to the final page, and ought to be gi ven a place on every office table, because it contains in a condensed form all that is valuable in semeiology and diagnostics to be found in bulkier volumos, and because in its arrangement and complete index, it is unusually convenient for quick reference in any emergency that may come upon the busy practitioner. —N. O. Med. Journ., Jan. 1879. This is a most important work for students, and one that is dt stined to become rapidly popular. It is composed of contributions from various eminent sources bearing upon this subject. The real secret of successful practice is the accurate diagnosis of disease. This manual teaches the student to arrange his investigation in such system as to enable him, with practice, to acquire this very desirable faculty. The division of the subject, as in this work, among the highest authorities living, is a good idea, and gives us in one compact form a series of monographs written by master.s. — Nashville Journal of Med. and Surg., Jan. 1879. JJAMILTON [ALLAN McLANE), M.D., Attending Physician at the Hospital f or Epileptics and Paralytics, Blackwell's Island, N. Y., and at the Out-Patients' Department of the New York Hospital. NERVOUSDISEASES; THEIR DESCRIPTION AND TREATMENT. In one handsome octavo volume of 512 pages, with 53 illus. ; cloth, $3 50. [Jttst Ready.) This is unquestionably the best and most com- plete text-book of nervous diseases that has yet ap- peared, and were international jealousy in scientific affairs at all possible, we might be excused for a feeling of chagrin that it should be of American parentage. This work, however, has been performed in New York, and has been so well performed that no room is left for anything but commendation. With great skill. Dr. Hamilton has presented to his readers a succinct and lucid survey of all that is known of the pathology of the nervous system, viewed in the light of the most recent researches. From the preliminary description of the methods of examination and study, and of the instruments of precision employed in the investigation of nervous diseases, up till the final collection of formulae, the book is eminently practical. — Brain, London, Oct. 1878, The author tells us in his preface that it has been his object to produce a concise, practical book, and we think he has been successful, considering the ex- tent of the subject which he has undertaken. In fact, it is more extensive than the title properly or accurately indicates, embracing — besides what are usually regarded as nervous diseases — inflammatory affections, both acute and chronic, hemorrhages and tumors of the cerebrum and cerebellum, medulla oblongata, spinal cord and nerves, with thrombosis and embolism of the arteries, sinuses, and veins. The reader may therefore expect information, more or less full and satisfactory, on almost every point connected with the nervous system. We have no hesitation in saying that reliance may be placed on Dr. Hamilton’s conscientious performance of his self- assigned task, on his soundness of judgment, and freedom from empiricism. — Edinburgh Med. Journ., Oct. 1878. From a very careful examination of the whole work, we can justlysay thatthe author has not only clearly and fully treated of diagnosis and treatment, but, unlike most works of this class, it is very com- prehensive in regard to etiology, and exposes the pathology of nervous diseases 1 n the light of the very latest experiments and discoveries. The drawings are excellent and Avell selected. After this careful revision, we can heartily recommend this work to students and general practitioners in particular as being a full exposition of diseases of the nervous sys- tem, their pathology and treatment, to date. — A. Y. Med. Record, Aug. 3, 1878. As stated in the preface, the author’s object has been to write a concise and practical book, for. which there is certainly a place, and we think he has succeeded admirably in fulfilling his object. The usual plan is adopted in the classification of the different diseases, the book not being greatly unlike Hammond’s in this respect, although it is very noticeable throughout that the author’s opin- ions vary widely from those of Dr Hammond. — Am. Supp. Obstet. Journ. Great Britain and Ireland, July, 1878. QRARCOT [J. M.), Professor to the Faculty of Med. Paris, Phys. to La SalpHrikre, etc. LECTURES ON DISEASES OF THE NERVOUS SYSTEM. Trans- lated from the Second Edition by George Sigerson, M.D., M.Ch., Lecturer on Biology, etc., Gath. Univ. of Ireland. With illustrations. {PublLshivg in the Medical News and Library, commencing with the July No. 1878 See page 2 ) 18 Henry C. Lea’s Publications — [Diseases of the Chesty d^c.) ^RO nW [LENNOX), F.R.G.S. Ed., Senior Surgeon to the Central London Throat and Ear Hospital, etc., THE THROAT AND ITS DISEASES. With one hundred Typical Illustrations in colors, and fifty wood engravings, designed and executed by the author. In one very handsome imperial octavo volume of 351 pages ; cloth, $5 00. {Now Ready.) The author’s rare artistic skill has been utilized in the production of one hundred beautiful illustra- tions in colors, the very best of the kind we have seen, a nd which have been distributed in ten plates. Fifty wood eui;ravings, designed and executed by the author, appear in the body of the work — these are unusually accurate. In conclusion, we recom- mend this beautiful volume as a.n acceptable addi- tion to the library of those engaged in the treatment of diseases of the throat. — N. Y. Med. Record, Nov. 9, 1S78. (JEILER (CARL), M.D., Ej Lectvrer on Laryngoscipy at the Univ. of Penna , Chief of the Throat Dispensary at the Univ. Hospital, Phila , etc. ^ HANDBOOK OF DIAGNOSIS AND TREATMENT OF DISEASES OF THE THROAT AND NAS \L CAVITIES. In one handsome royal 12mo. volume. With illustrations, {hi Press.) PLINT [A USTJN), M.D., Professor of the Principles and Practice of Medicine in Bellevue Hospital Med. College, N. Y. PHTHISIS: ITS MORBID ANATOMY, ETIOLOGY, SYMPTOM- ATIC EVENTS AND COMPLICATIONS, FATALITY AND PROGNOSIS, TREAT- MENT, AND PHYSICAL DIAGNOSIS; in a series of Clinical Studies. By Austin Flint, M.D., Prof, of the Principles and Practice of Medicine in Bellevue Hospital Med. College, New York. In one handsome octavo volume: $3 50. {Lately Issued.) This book contains an analysis, in the author’s lucid I mend the book to the perusal of all interested in the style, of the notes w'hich he has made in several hun- •itudy of this disease . — Boston Med. and Surg. Journal, dred cases in hospital and private practice. We com- 1 Feb 10, 1876. THE SAME AUTHOR. A MANUAL OF PERCUSSION AND AUSCUtTATION ; of the Physical Diagno.sis of Diseases of the Lungs and Heart, and of Thoracic Aneurism. In one handsome royal 12mo. volume: cloth, $1 75. {Just Issued.) n Y THE SA ME A UTHOR. A PRACTICAL TREATISE ON THE DIAGNOSIS, PATHOLOGY, AND TREATMENT OF DISEASES OP THE HEART. Second revised and enlarged edition. In one octavo volume of 560 pages, with a plate, cloth, $4. Dr. Flint chose a difficult subject for his researches, and has shown remarkable powers of observation an i reflection, as well as great industry, in his treat- ment of it. His book must be considered the fullest aud clearest practical treatise on those subjects, and ihonld be in the hands of all practitioners and stu- lents. It is a credit to American medical literature. —Arner. Journ. of the Med. Sciences, July, 1860. JQF THE SAME AUTHOR. A PRACTICAL TREATISE ON THE PHYSICAL EXPLORA- TION OF THE CHEST AND THE DIAGNOSIS OF DISEASES AFFECTING THE RESPIRATORY ORGANS. Second and revised edition. In one handsome octavo volume of 595 pages, cloth, $4 50. WILLIAMS S PULMOiXARY CONSUiVIPTIOX ; its Nature, Varieties, and Treatment. With an An- aly.si.s of One Thousand Cases to exemplify its duration. In oue ueat octavo volume of about 350 pages; cloth, $2 50. DIPHTHERIA ; its Nature and Treatment, with an account of the History of its Prevalence in vari- ous Countries. By D. D. Slade, M.D. Second and revised edition. In one neat royal 12mo. volume, cloth, $1 25. WALSHEON THE DISEASE80F THE HEART AND GREAT VESSELS. Third American Edition. In 1 vol. 8vo., 420 pp., cloth, $3 00. LECTURES ON THE DISEASES <'F THE STOMACH. With an Introduction on its .Anatomy and Physio- logy. By William Brtnton, M D., F.R S From the second and enlarged London edition . With il- lustrations on wood. In one handsome octavo volume of about 300 pages; cloth, $3 26. LA ROCHE ON PNEUMONIA. 1 vol. Svo., cloth, of .500 pages. Price, $3 00. LINCOLN’S ELECTRO THERAPEUTICS; a Concise Manual of Medical Electricity. In one very neat royal 12mo. volume, cloth, with illustrations, !jil 50. CLINICAL OBSERVATIONS ON FUNCTIONAL NERVOUS DISORDERS Bv C. H andfield Jones, M.D., Physician to St. Mary’s Hospital, &c. Sec ond American Edition. In one handsome octavo volume of 348 pages, cloth, $3 25. FULLER ON DISEASES OF THE LUNGS AND AIR- PASSAGES. Their Pathology, Physical Diagnosis, Symptoms, and Treatment. From the second and revised English edition. In one handsome ocatvo volume of about 500 pages : cloth, $3 50. CHAMBERS’S MANUAL OF DIET AND REGIMEN IN HEALTH AND SICKNESS. In one handsome octavo volume. Cloth, $2 75. CHAMBERS’S RESTORATIVE MEDICINE. An Har- veian Annual Oration. With Two Sequels. In one very handsome vol. small 12mo , cloth, $1 00. PAVY’S TREAT, SE ON THE FUNCTION OF DI- GESTION ; its Disorders and their Treatment. From the second London edition. In one hand- some volume, small octavo, cloth, $2 00. PAVY’S TREATISE ON FOOD AND DIETETICS. Physiologically aud Therapeutically Considered. In one haudsome octavo volume of nearly 600 pages, cloth, $4 75. SMITH ON CONSUMPTION ; ITS EARLY AND RE- MEDIABLE STAGES. 1 vol. 8vo.. pp. 254 ♦2 2-'’. BASHAM ON RENAL DISEASES: a Clinical Gnide to their Diagnosis and Treatment. With Illustra- tions. In ouel2mo. vol. of 304 pages, cloth, 00. LECTURES ON THE STUDY OF FEVER. By A. Hudson, M.D., M.R.I.A., Physician to the Meath Hospital In one vol. 8vo., cloth, $2 50. A TREATISE ON FEVER. By Robert D. Lyons, K C C. In oue octavo volume of 362 pages, cloth, $2 25. Henry C. Lea’s Publications — {Venereal Diseases^ Sc.). 19 T>UMSTEAD {FREEMAN J.), M.D., Professor of Venereal Diseases at the Gol. of Phys and Surg.. New York dec. THE PATHOLOGY AND TREATMENT OF VENEREAL DIS- EASES. Including the results of recent investigations upon the subject. Third edition, revised and enlarged, with illustrations. In one large and handsome octavo volume of over 700 pages, cloth, $6 00 ; leather, $6 00. In preparing this standard work again for the press, the author has subjected it to a very thorough revision . Many portions have been rewritten, and much new matter added, in order to bring it completely on a level with the most advanced condition of syphilography, but by care- ful compression of the text of previous editions, the work has been increased by only sixty-four pages. The labor thus bestowed upon it, it is hoped, will'insure for it a continuance of its position as a complete and trustworthy guide for the practitioner. A valuable work ou Venereal Di.^eases, which not Only has a wide circulation in this country, and been accepted as the standard, but appears to have formed the basis, to a large extent, of many of the books and articles which have been written on the same subject and published in England.— The Glas- gow Med. Journ., Oct. 1877. 1 1 is the most complete book with which we are ac- quainted in the language. The latest views of the best authoritiesare put forward, and the information Is well arranged — a great point for the student and still more for the practitioner. The subjects of vis- ceral syphilis, syphilitic affections of theeyes, and the treatment of syphilis by repeated inoculations, are rery fully discussed. — Lond. Lancet, Jan. 7, ’71. Dr. Bumstead’s work is already so universally known as the best treatisein the English language on I venereal diseases, that it may seem almost superPn- ous to say more of it than that a new edition has been issued. But the author’s industry has rendered this new edition virtually a new work, and so merits as much special commendation as if its predecessors har not been published. As a thoroughly practical book on a class of diseases which form a large share of nearly every physician’s practice, the vol- ume before us is by far the best of which we have knowledge — N. Y. Medical Gazette, Jan. 28, 1871. It is rare in the history of medicine to find any one book which contains all that a practitioner needs to know ; while the possessor of “Bumstead on Vene- real” has no occasion to look outside of its covers for anything practical connected with the diagnosis, his- tory, or treatment of these affections. — N. Y. Medi- co Journal, March. 1871. flULLERIER [A Surnann. tn f hfi Uh'n Surgeon to the Hbpital du Midi. and JDVMSTEAD {FREEMAN J.), Professor of Venereal Diseases in the. College, of Physicians and Surgeons, N. Y. AN ATLAS OF VENEREAL DISEASES. Translated and Edited by Freeman J. Bumstead. In one large imperial 4to. volume of 328 pages, double-columns, with 26 plates, containing about 150 figures, beautifully colored, many of them the si*e of life; strongly bound in cloth, $17 00 ; also, in five parts, stout wrappers, at $3 per part. Anticipating a very large sale for this work, it is offered at the very low price of Three Dol- lars a Part, thus placing it within the reach of all who are interested in this department of practice. Gentlemen desiring early impressions of the plates would do well to order it without delay. A specimen of the plates and text sent free by mail, on receipt of 25 cents. We wish for once that our province was not re- strict d to methods of treatment, that we might say some hing of the exquisite colored plates in this volume. —London Practitioner , May, 1869. As a whole, it teaches all that can be taught by means of plates and print . — London Lancet, March l.S, 1869. Superior to anything of the kind ever before issued on this continent . — Canada Med. Journal, March, ’69 The practitioner who desires to understand this branch of medicine thoroughly should obtain this, the most complete and best work ever published. — Dominion Med. Journal, May, 1869. This is a work of^master hands on both sides. M. GuJlerier is scarcely second to, we think wemay truly say is a peer of the illustrious and venerable Ricord, while in this country we do not hesitate to say that Dr. Bumstead, as an authority, is without a rival. Assuring our readers that these illustrations tell the whole history of venereal disease, from its inception to its end, we do not know a single medical work, which for its kind is more necessary for them to have . — California Med. Gazette, March, 1869. The most splendidly illustrated work in the lan- guage, and in our opinion far more useful than the French original. — Am. Jour. Med. Sciences, Jan. ’69. The fifth and concluding number of this magnificent work has reached us, and we have no hesitation in saying that its illustrations surpassthose of previous numbers.— Boa# Med. and Srirg . Jl., 3&n. \A 1869. Other writers besides M. Cullerier have given ns a good account of the diseases of which he treats, but no one has furnished us with such a complete series of illustrations of the venereal diseases') There is, however, an additional interest and value pof-sessed by the volnmebefore us; for it is an American reprint and translation of M. Cullerier’s work, with inci- dental remarks by one of the most eminent Ameri- can syphilographers, Mr. Bumstead.— Brif awd Foi . Medico-Chir . Review, July, 1869. TEE (EEMRY), Prof, of Surgery at the. Royal College of Surgeons of England, etc. LECTURES OX SYPHILIS AND ON SOME FORMS OF LOCAL DISEASE AFFECTING PRINCIPALLY THE ORGANS OF GENERATION. In one handsome octavo volume: cloth; $2 25, {^Lately Published.) ulation; the modifications of these proces.se.sin patients previously syphilitic: primary and secondary syphilitic diseases of the mucous membranes and their liability to communicate constitutional syphilis, etc. The book is full of clinical material illustrating these topics, original or quoted . — Archives of Dermatology, April, 1876. The work is valuable, as it treats quite fully of sub- jects which are not dwelt upon in the systematic works of other English authors of the present day. as the jn- oculahility of syphilitic blood; the conditions under which the secretions of primary and secondary syphi- litic manifestations may be inoculated naturally or artificially; the morbid processes produced by such inoc- H ILL {BERKELEY), Surgeon to the Lock Hospital, London. ON SYPHILIS AND LOCAL CONTAGIOUS DISORDERS. one handsome octavo volume ; cloth, $3 26. In 20 Henry C. Lea’s Publications — (Diseases of the SJcin^ <&c.). JfOX [TILBURY), M.D.,F.R.C.P.,and T. C. FOX, B.A., M.R.C.S., Phy.9ieian to the Department for Skin Diseases, University College Hospital. EPITOME OF SKIN DISEASES. WITH FORMULAE. For Sti’- DENTS AND PRACTITIONERS. Second edition, thoroughly revised and greatly enlarged. In one very handsome 12mo. volume of 216 pages. Cloth, $I 38. {Just Ready.) PREFACE. In preparing this edition of our “Epitome” for publication in the United States, we have increased the matter to about three times its original amount. The kindly appreciation mani- fested for the work by the American profession has stimulated us to spare no pains in rendering it more worthy of their approb.ation, and in its enlarged form we believe that it will be found of enhanced value. About two-thirds of the work is newly written, and we may direct attention particularly to the section regarding the Pathology of the Skin, which has been entirely recast, and now contains a concise account of all the important changes taking place in the dermal textures in disease. The clinical descriptions of diseases also have been amplified and occasion- ally remodelled. Lastly, ive may sa}' th.at in adding material to the book we have selected such as bears on the practical side of Dermatology, to the exclusion of that which is as yet hypo- thetical or merely of interest to the curious student. The favorable reception accorded to the work on both sides of the Atlantic would seem to show that it has realized the object with which it was prepared — to afford assistance to the stu- dent in his early study of dermatology, and to serve as a manual for ready reference by the practitioner in his daily practice. For this latter purpose it has been specially adapted, by means of the references made in the sections on treatment to the formulae at the end. -^flLSON [ERASMUS), F.R.S. THE STUDENT’S BOOK OF CUTANEOUS MEDICINE and Dis- eases OP THE SKIN. In one very handsome royal 12mo. volume. $3 60. yELIGAN [J. MOORE), M.D., M.R.I.A. ATLAS OF CUTANEOUS DISEASES. In one beautiful quarto volume, with exquisitely colored plates, &c., presenting about one hundred varieties of disease.. Cloth, $5 50. JJILLIER [THOMAS), M.D., Physician to the Skin Department of University College Hospital, etc. HAND-BOOK OF SKIN DISEASES, for Students and Practitioners. Second Am. Ed. In one royal I2mo. vol, of 358 pp. With Illustrations Cloth, S2 25. We can conscientiously recommend it to the stu- dent ; the style is clear and pleasant to read, the matter is good, and the descriptions of disease, with the modes of treatment recommended, are frequent- ly illustrated with well-recorded cases. — London Med. i’imes and Gazette, April 1, 1865. It is a concise, plain, practical treatise on the var;ou6 diseases of the skin ; just such a work, indeed as was much needed, both by medical stu- dents and practitioners. — Chicago Medical Ex- aminer, Maj 1865. ^EST [CHARLES), M.D., Physician to the Hospital for Sick Children., London, &c. LECTURES ON THE DISEASES OF INFANCY AND CHILF- HOOD. Fifth American from the sixth revised and enlarged English edition. In one large and handsome octavo volume of 678 pages. Cloth, $4 60 ; leather, $5 50. {Lately Issued ) The continued demand for this work on both sides of the Atlantic, and its translation into German, French, Italian, Danish, Dutch, and Russian, show that it fills satisfactorily a want extendvely felt by the profession. There is probably no man living who can speak with the authority derived from a more extended experience than Dr. West, and his work now presents the results of nearly 2000 recorded cases, and 600 post-mortem examinations selected from among nearly 40,000 cases which have passed under his care. In the preparation of the pre- sent edition he has omitted much that appeared of minor importance, in order to find room for the introduction of additional matter, and the volume, while thoroughly revised, is therefore not increased materially in size. Of all the English writers on the diseases of chil- I highestliving authorities in the difficult department dr jn, there is no one so entirely satisfactory to us 1 of medical science in which he is most widely as Dr. West. For years we have held his opinion 1 known.- Boston Med. and Surg. Journal. as judicial, and have regarded him as one of the 1 THE SAME AUTHOR. {Lately Issued.) ON SOME DISORDERS OF THE NERVOUS SYSTEM IN CHILD- HOOD; being the Lumleian Lectures delivered at the Royal College of Physicians of London, in March, 1871. In one volume small l2mo., cloth, $1 00. jD r THE SA HE A UTHOR. LECTURES ON THE DISEASES OF WOMEN. Third American, from the Third London edition. In one neat octavo volume of about 650 pages, clotl, $3 75; leather, $4 75. \ Henry C. Lea’s Publications — (Di^^eases of Childi'en). 21 LEWIS), M.D., Olinical Professor of Diseases of Children in the Bellevue Hospital Med. College, N T. A COMPLETE PRACTICAL TREATISE ON THE DISEASES OF CHILDREN. Fourth EditioH, revised nnd enlarged. In one handsome octavo volume of about 750 pages, with illustrations. Cloth, $4 50 ; leather, $5 50. {Now Ready.') The very marked favor with which this work has been received wherever the English lan- guage is spoken, has stimulated the author, in the preparation of the Fourth Edition, to spare no pains in the endeavor to render it worthy in every respect of a continuance of professional confidence. Many portions of the volume have been rewritten, and much new matter intro- duced, but by an earnest effort at condensation, the size of the work has not been materially increased. In the period which has elapsed since the third ] It is scarcely necessary for us to say the work he- edition of the work, so extensive have been the ad- : fore us is a standard work upon diseases of cliildren, vances that whole chapters required to be rewritten, j and thai no work has a higher standing than it upon and hardly a page could pass without some material those affections. In consequence of its thorough re- correction or addition. This labor has occupied the j vision, the work has been made of more value than writer closely, and he has performed it conscien- ever, and may be regarded as fully abreast of the tiously, so that the book may be considered a faith- times. We cordially commend it to students and ful portraiture of an exceptionally wide clinical ; physicians. There is no better work in the language experience in infantile diseases, c rrected by a. care- on diseases of childi’eu. — tincinnati Med. News, ful study of the recent literature of the subject. — j March, 1879. Med. and Surg. Reporter, April 5, 1879. nONDIE (D. FRANCIS), M.D. A PRACTICAL TREATISE ON THE DISEASES OF CHIL- dren. Sixth edition, revised and augmented. In one large octavo volume of nearly 800 closely-printed pages, cloth, $5 25 ; leather, Sfi 25. ^MITH [EUSTACE), M.D., Physician to the Northwest London Free Dispensary for Sick Children. A PRACTICAL TREATISE ON THE WASTINO DISEASES OF INFANCY AND CHILDHOOD. Second American, from the second revised and en- larged English edition. In one handsome octavo volume, cloth, $2 50. {Lately Issued.) ^WAYNE [JOSEPH GRIFFITHS), M.D., Physician- Accoucheur to the. British General Hospital, &c. OBSTETRIC APHORISMS FOR THE USE OF STUDENTS COM- MENCING MIDWIFERY PRACTICE Second American, from the Fifth and Revised London Edition with Additions by E. R. Hutchins, M.D. With Illustrations. In one neat 12mo. volume. Cloth, $1 25. {Lately Issued.) * See p. 4 of this Catalogue for the terms on which this work is ofi'ered as a premium to subscribers to the ‘ ‘ American Journal of the Medical Sciences.” CHURCHILL ON THE PUERPERAL FEVER AND OTHER DISEASES PECULIAR TO WOMEN. 1 vol. Svo. , pp. l.'in, cloth $2 hQ. DEWEES’S TREATISE ON THE DISEASES OF FE- MALES. With illustrations. Eleventh Editioc, with the Author’slastimprovementpand correc- tions. In one octavo volume of .o36 pages, with plates, cloth. $3 00. MEIGS ON THE NATURE, SIGNS. AND TREAT- MENT OF CHILDBED FEVER. 1 vol. 8vo , pp. 36.’). cloth $2 00. ASHWELL’S PRACTICAL TREATISE ON TH E DIS- EASES PECULIAR TO WOMEN. Third American, from the Third and revised London edition. 1 vol. 8vo., pp. 528, cloth. $3 50. JJODGE {HUGH L.), M.D., Emeritus Professor of Obstetrics, &c., in the University of Pennsylvania. ON DISEASES PECULIAR TO WOMEN ; including Displacements of the Uterus. With original illustrations. Second edition, revised and enlarged. In one beautifully printed octavo volume of 531 pages, cloth, $4 50. Professor Hodge’s work is truly an original one I contribution to the study ofwomen’s diseases, itis rf from beginning to end, consequently no one can pe- great value, and is abundantly able to stand on its ruse its pages without learning something new. At a 1 own merits. — N. Y. Medical Record, Sept. 15, 186f-. QtlURCHILL [FLEETWOOD), M.D., M.R.I.A. ON THE THEORY AND PRACTICE OF MIDWIFERY. A new American from the fourth revised and enlarged London edition. With notes and additioi s by D. Francis Condie, M.D., author of a “Practical Treatise on the Diseases of Chil- dren,” Ac. With one hundred and ninety four illustrations. In one very handsome octavo volume of nearly 700 large pages. Cloth, $4 00 ; leather, $5 00. MONTGOMERY’S EXPOSITION OF THE SIGNS AND SYMPTOMS OF PREGNANCY. With two exquisite colored plates, and numerous wood cuts. In 1 vol. Svo. ,ofnearly600pp., cloth, $3 76. RIGBY’S SYSTEM OF BIIDWIFERY. With notes and Additional Illustrations. Second Ameritan edition. One volume octavo, cloth, 42£ pages, $2 50. 22 Henry C. Lea’s Publications — (Diseases of Women). rPHOMAS [T. GAILLARD) Professor of Obstetrics, Ac., in i M.D., the College of Physicians and Surgeons, N. Y., Ac A PRACTICAL TREATISE ON THE DISEASES OFWOMEN, Fourth edition, enlarged and thoroughly revised. In one large and handsome octavo volume of 800 pages, with 191 illustrations. Cloth, $5 00; leather, $6 00. (Just Issued.) The author has taken advantage of the opportunity afforded by the call for another edition of this work to render it worthy a continuance of the very remarkable favor with which it has been received. Every portion has been subjected to a conscientious revision, and no labor has been spared to make it a complete treatise on the most advanced condition of its important subject. A work which hus reached a fourth edition, and that, too, in tlie sliort space of five years, has achieved a reputation which places it almost beyond the reach of criticism, and the favorable opinions which we have a' ready expressed of the former editions seem to re- quire that we should do little more than announce this new issue. We cannot refrain from saying that, as a practical work, this is second to none in the Eng- lish, or, indeed, in any other language. The arrange- ment of the contents, the admirably clear manner in which the subject of the dilferential diagnosis of several of the diseases is handled, leave nothing to be desired by the practitioner who wants a thoroughly clinical work, one to which he can refer in difficult cases of doubtful diasnosis with the certainty of gain- ing light and instruction. Dr. Thomas is a man with a very clear head and decided views, and thei’e seems to be nothing which he so much dislikes as hazy notions of diagnosis and blind routine and unreasonable thera- peutics. The student who will thoroughly study this b lok and test its principles by clinical observation, will certainly not be guilty of these faults. — London Lancet, Feb. 13, 187.5, Reluctantly we are obliged to close this unsatis- factory notice of so excellent a work, and in conclu- sion'would remark tha t, as a teacher ofgynsecology. both didac'ic and clinical, Prof. Thomas has certainly taken the lead far ahead of his confreres, and as an author he certainly has met with unusual and mer- ited success. — Am. Journ. of Obstetrics, Nov. 1874. This volume of Prof. Thomas in its revised form is classical without being pedantic, full in the details of anatomy and pathology, without ponderous translation of pages of German literature, describes distinctly the details and difficulties of each opera- tion, without wearying and useless minutise, and is in all respects a work worthy of confidence.justify- ing the high regard in which its distinguished au- thor is held by the profession. — Am. Supplement, Ohstet. Journ., Oct. 1874. Professor Thomasfairly took the Profession of the United States by storm when his book first made its appearance early in 1868. Its reception was simply enthusiastic, notwithstanding a few adverse criti- cism.s from our transatlantic brethren, the first large edition was rapidly exhausted, and in six months a second one was issued, and in two yearsathird one was announced and published, and we are now pro- mised the fourth. The popularity of this work wa.s not ephemeral, and itssuccess wasunprecedentedin the annalsof American medical literature. Six years is a long period in medical scientific research, but Thomas’s work on “ Diseases of Women” is still the leading native production of the United States. The order, the matter, the absence of theoretical dispu'a- ti veness, the fairness of statement, and the elegance of diction, preserved throughout the entire range of the book, indicate that Professor Thomas did not overestimate his powers when he conceived the idea and executed the work of producing a new treatise upon diseases of women. — Prof. Fallen, in Louis- ville Med. Journal, Sept. 1874. T>ARNES [ROBERT], M.D., F.R.C.P., Obstetric Physician to St. Thomas's Hospital, d-e. A CLINICAL EXPOSITION OP THE MEDICAL AND SDRGI- CAL DISEASES OF WOMEN. Second American, from the Second Enlarged and Revised English Edition. In one handsome octavo volume, of 784 pages, with 181 illustrations. Cloth, $4 50 ; leather, $6 50. (Just Ready.) The call for a new edition of Dr. Barnes’s work on the Diseases of Females has encouraged the author to make it even more worthy of the favor of the profession than before. By a rear- rangement and careful pruning space has been found for a new chapter on the Gynaecological Relations of the Bladder and Bowel Disorders, without increasing the size of the book, while many new illustrations have been introduced where experience has shown them to be needed. It is therefore hoped that the volume will be found to reflect thoroughly and accurately the present condition of gynaecological science. Dr B.irnes stands at the head of his profession in the old country, and it requires but scant scrutiny of his book to show that it has been sketched by a master. It is plain, practical common sense ; shows very deep research without being pedantic ; is emi- nently calculated to inspire enthusiasm without in- culcating rashness; points out the dangers to be avoided as well as the success to be achieved in the various operations connected with this branch of medicine; and will do much to smooth the rugged path of the young gynaecologist and relieve the per- plexity of the man of mature years. — Canadian Journ. of Med. Science, Nov. 1878. We pity the doctor who, having any consider- able practice in diseases of women, has no copy of ” Barnes” for daily consultation and instruction. It is at once a book of great learning, research, and individual experience, and at the same time emi- nently practical. That it has been appreciated by the profession, both in Great Britain and in this country, is shown by the second edition following BO soon upon the first. — Am. Practitioner, Nov. 1878. Dr Barnes’s work is one of a practical character, largely illustrated from c.a.sesiu his own experience, but by no means confined to such, as will be learned from the ffict that he quotes from no 1e.'s than 628 medical authors in numerous countries. Coming from such an author, it is not necessary to say that the work is a valuable one, and should be largely consulted by the profession. — Am. Sopp Obstetrical Journ. Gt. Britain and Ireland, Oct. 1878. No other gynecological work holds a higher posi- tion, having become an authority everywhere in diseases of women. The work has been brought fully abreast of present knowledge. Every practi- tioner of medicine should have it upon the shelves of his library, and the student will find it a superior text-book. — Cincinnati Med. News, Oct. 1878. This second revised edition, of course, des.erves all the commendation given to its predecessor, with the additional one that it appears to include all or nearly all the additions to our knowledge of its subject that have been made since the appearance of the first edi- tion The American references are, for an English work, especially full and appreciative, and we can cordially recommend the volume to American read- ers — Journ. of Nervous and Mental Disease, Oct. 1878. This second edition of Dr. Barnes’s great work comes to us containing many additions and improve- ments which bring it up to date in every feature. The excellences of the work are too well known to require enumeration, and we hazard the prophecy that they will for many years maintain its high po- sition as a standard text book and guide book for students and practitioners. — N. C. Med. Journ., Oct. 1878. Henry C. Lea’s Publications — (Diseases of Women). 23 JfMMET {THOMAS ADDIS). M.D. Unrge.on to the Woman's Hospital, Ntw York, et^. THE PRINCIPLES AND PRACTICE OF GYNECOLOGY, for the use of Students and Practitioners of Medicine. In one large and very handsome octavo volume of 856 pages, with 130 illustrations. Cl th, $5; leather, $6, {Just Ready.) • Dr. Emmet is so widely known as among the most eminent of those who have made gynae- cology a peculiarly American science that the profession cannot fail to welcome a work in which he has condensed the results of his long and extensive experience. He has sought to consider the whole subject of the diseases peculiar to females in a manner which will adapt the volume, not only to the wants of the student as a text-book, but to those of the practitioner as an aid in the emergencies of daily practice. A special feature of the work will be f-.und in the numerous condensed tables, which convey at a glance, and within the narrowest compass, the conclusions to be drawn from the many thousand cases which have passed under the care of the author. With trifling exceptions, the illustrations are all original, and the volume will be found in every point of typographical execution worthy of the distinguished position which is confidently anti- cipated for it. QUAD WICK {JAMES R.), A.M., M.D. A MANUAL OF THE DISEASES PEOULTAR TO WOMEN. In one neat volume, royal 12mo , with illustrations. {Preparhig.) America has contributed so largely to the advances which have made the treatment of Dis- eases of Women a distinctive department of medical science, that the student will naturally turn to American Books for the latest and most trustworthy instruction on the subject in its most modern aspect. Yet there has thus far been no attempt in this country to produce a handy manual, presenting in a condensed and convenient form the information requisite for the learner or for the general practitioner. This want it has been the effort of Dr. Chadwick to supply, and the special attention which he has devoted to the subject is a guarantee of the value of his labors. A distinguishing feature of the work will be a number of diagrammatic illustrations, facilitating greatly the comprehension of the text. ^INCKEL [F.], ' ' Professor and Director of the Gyncecological Clinic in the University of Rostock. A COMPLETE TREATISE ON THE PATHOLOGY AND TREAT- MENT OF CHILDBED, for Students and Practitioners. Translated, with the consent of the author, from the Second German Edition, by James Read Chadwick, M.D. In one octavo volume. Cloth, $4 00. {Lately Issued.) This work was written, as the author tells us in hi.'! | ready in the field, and the present standpoint of sci- preface, to supp y a want ai’ising from the very hriel ence. The \york has reached a second edition, and consideration given to puerperal disea.'^es by writers bear.s evidence throughout of careful study and prac- on Obstetrics, in which respect it seems the profession tical experience. As its title implies, it is a manual in his country is not different from ours, and to fill a rather than a treatise . — American J out nal ojAltd. Sci~ blank left between the treatises upon the subject al- ences, April, 1871. rpSE OBSTETRICAL JO URNAL. [Free of postage for 1879 .) THE OBSTETRICAL JOURNAL of Great Britain and Ireland; Including Midwifery, and the Diseases op Women and Infants. With an American Supplement, edited by J. V. Ingham, M.D. A monthly ‘of about 06 octavo pages, very handsomely printed. Subscription, Five Dollars per annum. Single Numbers, 60 cents each. Commencing with April, 1873, the Obstetrical Journal consists of Original Papersby Brit- ish and Foreign Contributors ; Transactions of the Obstetrical Societies in England and abroad. Reports of Hospital Practice; Reviews and Bibliographical Notices; Articles and Notes, Editorial, Historical, Forensic, and Miscellaneous; Selections from Journabs; Cor- respondence, Ac Collecting together the vast amount of material daily accumulating in this important and rapidly improving department of medical science, the value of the infor- mation which it preients to the subscriber may be estimated from the oharaoter of the gen- tlemen who have already promised their support, including such names as those of Drs. At- THILL, AveLING, RoB ERT B ARNE S, J. H E NRT Be NNET, NatH A N BozeMAN, Th OM A S Ch A M B E R S , Fleetwood Churchill, Charles Clay, John Clay, Matthews Duncan, Arthur Farre, Robert Greenhalgh, Graily Hewitt, Braxton Hicks, Alfred Meadows, W. Lrish- MAN, Alex. Simpson, Heywood Smith, Tyler Smith, Edward J. Tilt, Lawson Tait, Spencer Wells, Ac. Ac. ; in short, the representative men of British Obstetrics and Gynae- cology. In order to render the Obstetrical Journal fully adequate to the wants of the Ameri- can profession, each number contains a Supplement devoted to the advance.® made in Obstet- rics and Gynaecology on this side of the Atlantic. This portion of the .Journal i.s under the editorial charge of Dr J. V. Ingham, to whom editorial communications, exchanges, books for reziew, Ac., may be addressed, to the care of the publisher. Complete .sets from the beginning can no longer be furnished, but subscriptions can com nence with January, 1879, or Vol. Vll., No 1, April, 1879. 24 Henry C. Lea’s Pubiioations— (M tZwi/ery). pLAYFAIR ( W. S.), M.D., F.R.C.P., Professor of Obstetric Medicine in King's College, etc. etc. A TREATISE OX THE SCIENCE AND PRACTICE OF MIDWIFERY. Second American, from the Second and Revised English Edition. Edited, with Addi- tions, by Robert P. Harris, M.D. In one handsome octavo volume of 639 pages, with 182 illustrations. Cloth, $4 00 ; Leather, $5.00. {Just Ready .) * In reprinting this work from the second London edition, the position which it has assumed in this country as an authoritative text-book seemed to call for such additions as would render it more completely suited to the wants of the American student. A careful scrutiny on the part of the editor has shown that but little was required for this purpose ; the work, though condensed, being very complete and accurate. With the exception of numerous short foot-notes, therefore, his additions have been confined to points in which the experience and practice of American obstetricians diflFer from those of England, and to one or two matters of recent interest. These are chiefly the Caesarean Section ; the varieties of forceps, and their use in the dorsal decubitus; dystocia from tetanoid uterine constriction; and the intra-venous injection of milk, as a substi- tute for the transfusion of blood. The position which this work has so qii’ckly taken in this country as an authoritative text-book readers any extended consideration of its plan and scope unnecessary. Its merits, which are many, have al- ready found their way to the appreciation of students and practitioners alike in the length and breadth of the land. — Am. Supp. Ohstet. Journ. of Gt. Britain and Ireland, Oct. 1S78. This excellent text-book has been submitted to a thorough and careful revision, and will be found fully up to the times in every department. The cotes by the American editor enhance the value of the work for the American student. Those on the use of forceps are particulirly good, and constitute by themselves a valuable chapter. — N. Y. Med. Journ., Nov. 1878. The best work on the subject ever published in the English language. It is written in a cleai*, pleasant style, without that verbosity which characterizes some modern and highly pretentious works. The au- thor is quite up with the times, both in practice and theory. It is the best text-book we have for students, and sufficiently full of detail to supply all the wants of the practitioner. We would gladly see it in the hands of all who practise midwifery. — Canadian Journ. of Med. Sci., Nov. 1878. Probably this is the very best and most useful manual of midwifery now available to the profes- sion. Itiswritten in lucid, scholarly English, which some of our cis-Atlantic writers would do well to imitate. There has been no attempt to swell the magnitude of the work by fine writing, or by lengthy discussions ofobscure points of which no trustworthy solution has yet been reached ; on the contrary, the tendency is throughout obviously towards simplic- ity. The chapter upon the Mechanism of Labor (which ought to be the crowning chapter in a trea- tise on obsteti-ics) is remarkably clear and good, and is divested of those features which in almost every other work we know lets only darkness instead of light in upon the subject. — N. C. Med. Journ., Oct. 1878. JJODGE {HUGH L.), M.D., Emeritus Professor of Midwifery, &c., in the University of Pennsylvania, &c. THE PRINCIPLES AND PRACTICE OF OBSTETRICS. Illns- trated with large lithographic plates containing one hundred and fifty-nine figures from original photographs, and with numerous wood-cuts. In one large and beautifully printed quarto volume of 550 double-columned pages, strongly bound in cloth, $14. The work of Dr. Hodge is something more than a simple presentation of his particular views in the department of Obstetrics; it is something more than an irdinary treatise on midwifery; it is, in fact, a cyclopaedia of midwifery. He has aimed to em- body in a angle volume the whole science and art of Obstetrics. A.n elaborate text is combined with ac- curate and varied pictorial illustrations, so that no fact or principle is left unstated or unexplained. — Am. Med. Times, Sept. 3, 1864. It 18 very large, profusely and elegantly illustrat- ed, and is fitted to take its place near the works of great obstetricians. Of the American works on the subject it is decidedly the best. — Edinb. Med. Jour., Dec. 1864. We have read Dr. Hodge’s book with great pleasure, and have much satisfaction in express- ing our commendation of it as a whole.' It is cer- tainly highly instructive, and in the main, we be- lieve, correct. The great attention which the au- thor has devoted to tne mechanism of parturition, taken along with the conclusions at which he has arrived, point, we think, conclusively to the fact that, in Britain at least, the doctrines of Naegele have been too blindly received. — -Glasgow Med. Journal, Oct. 1864. *** Specimens of the plates and letter-press will be forwarded to any address, free by mail, on receipt of six cents in postage stamps. UNNER {THOMAS H.), M.D. ON THE SIGNS AND DISEASES OF PREGNANCY. First American from the Second and Enlarged English Edition. With four colored plates and illustra- tions on wood. In one handsome octavo volume of about 500 pages, cloth, $4 25. JDAMSBOTHAM [FRANCIS H.), M.D. ^^THE PRINCIPLES AND PRACTICE OF OBSTETRIC MEDI- CINE AND SURGERY, in reference to the Process of Parturition. A new and enlarged edition, thoroughly revised by the author. With additions by W. Y. Keating, M. D., Professor of Obstetrics, &c., in the Jefferson Medical College, Philadelphia. In one l.irgre and handsome imperial octavo volume of 650 pages, strongly bound in leather, with raised bands ; with sixty-four beautiful plates, and numerous wood-cuts in the text, containing in all nearly 200 large and beautiful figures. $7 00. Henry C. Lea’s Publications — {Midwifery^ Surge7'y). 25 TEISHMAN {WILLIAM), M.D., Regius Professor of Midwifery in the University of Glasgow, &c. A SYSTEM OF MIDWIFERY, INCLUDING THE DISEASES OF PREGNANCY AND THE PUERPERAL STATE. Second American, from the Second and Revised English Edition, with additions by John S. Parry, M.D., Obstetrician to the Philadelphia Hospital, &c. In one large and very handsome octavo volume of over 700 pages, with about two hundred illustrations: cloth, $6 ; leather, $6. {Just Issued.) That this book is recommended as a text-book by many of the leading scholars of medicine in this country, is suflicient evidence of the favor in which it is held. In a word, we know of no better book in our language, both for the student and practitioner. The value of the book is enhanced by this second edition, which contains many notes by our late Dr. Parry. — Chicago Med. Journ. and Examiner , March. 1877. But the most valuable additions to the volume are those made by the American editor. One of the best tests of a man’s ability is for him to take a standard work in our profe.ssion, like this of Dr. Leishman, and materially improve it. Many a one, with more ambition than wis- dom, has attempted it with other books and failed. But Dr. Parry has succeeded most admirably. We know no obstetrical work that has anything better on the use of the forceps than that which Dr. Parry has given in this, and no work that has the rational and intelligent views upon lactation with which he hasenriched this. Having used “Leishman” for two years as a text-book for stu- dents, we can cordially commend it.and are quite satisfied to continue such use now. — Am. Practitioner, Mar. 187 G. This new edition decidedly confirms the opinion which we expressed of the first edition of the work-in the May, 1874, number of this Journal, that this is “the best modern work on the subject in the English language.” The excellent practical notes contributed by Dr. Parry refer principally to the use of the forceps, lactation, and the puerperal diseases, and are intended to increase the usefulness of the work in this country. An entirely new chapter on diphtheria of puerperal wounds has been added (Dr. P. has had unusual experience in this form of puerperal fever), and also a number of illustrations of the principal obstetrical instruments in use in Ame- rica. We have no hesitation in saying that the work, iu its present shape, is a great improvement on its prede- cessor, and in recommending it as the one obstetrical text- book which we should advise every English speak- ing practitioner and student to buy. — American Jour- nal of Obstetrics, Feb. 1876. Perhaps the most useful one the student can procure. Some important additions have been made by the editor, in order to adapt the work to the profession in this coun- try, and some new illustrations have been introduced, to represent the obstetrical instruments generally em- ployed in American practice. In its present form, it is an exceedingly valuable book for both the student and practitioner. — New York Med. Journal, Jan. 1876. Since the publication of Tyler Smith’s lectures on midwifery, no text book which was in reality the exponent of British practice has appeared in the English language until Dr. Leishman supplied the want by his system of midwifery, which was pub- lished about three years ago. The chief feature in this work is the exactness in description of the me- chanism of labor ; it exhibits most accurate obser- vation, and is a perfect analysis of the subject, it is clear, precise and masterly. The work is in every way a valuable addition to the works already be- fore the profession on the science and practice of obstetrics, and will, we doubt not, be the favorite text-book used in our schools. — Cftnada Med. and Surg. Journal, Nov. 1876. pARRY [JOHN S.), M.D., Obstetrician to the Philadelphia Hospital, Vice-Prest. of the Obstet. Society of Philadelphia. EXTRA-UTERINE PREGNANCY: ITS CLINICAL HISTORY, DIAGNOSIS, PROGNOSIS, AND TREATMENT. In one handsome octavo volume. Cloth, $2 50. {Lately Isstied.) In this work Dr. Parry ha.s added a most valuable contribution to obstetric literature, and one which meets a want long felt by those of the profession who have ever been called upon to deal with this cla.ss of cases. — Boston Med. and Surg. Journ., March 9, 1876. This work, being as near as po.ssible a collection of the experiences of many per.sons. will afford a most useful guide, both in diagnosis and treatment, for this most interesting and fatal malady. We think it should be in the hands of all physicians practising midwifery. — Cin- cinnati Clinic, Feb. 5, 1876. OTIMSON [LEWIS A.), A.M., M.D., Yj Surgeon to the Presbyterian Hospital. A MANUAL OF OPERATIVE SURGERY. In one very handsome royal 12mo. volume of about 500 pages, with 332 illustrations ; cloth, $2 50. {Now Ready.) The work before us is a well printed, profusely illustrated manual of over four hundred and seventy pages. The novice, by a perusal of the work, will gain a good idea of the general domain of operative surgery, while the practical surgeon has presented to him within a very concise and intelligible form the latest and most approved selections of operative procedure. Theprecision and conciseness with which the different operations are described enable the author to compress an immense amount of practical Information in a very small compass. — N. Y. Medical Record, Aug. 3, 1878. This volume is devoted entirely to operative sur- gery, and is intended to familiarize the student with the details of operations and the different modes of performing them. The work is handsomely illus- trated, and the deicriptions are clear and well drawn. It is a clever and useful volume; every student should possess one. The preparation of this work does away with the necessity of pondering over larger works on surgery for descriptions of opera- tions, as it presents in a nut-shell just what is wanted by the surgeon without an elaborate search to find it. — Md. Med Joxirnal, Aug. 1878. The author’s conciseness and the repleteness of the work with valuable illustrations entitle it to be classed with the text-books for students of operative surgery, and as one of reference to the practitioner. — Cincinnati Lancet and Clinic, July 27, 1878. SKET’S OPERATIVE SURGERY. In 1 vol. 8vo. cl., of660 pages ; withabout lOOwood-cuts. $3 26 COOPER’S LECTURES ON THE PRINCIPLES AND Pbacticeof Surgery. Ini voI. 8vo. cl’h, 750p. $2. GIBSON’S INSTITUTES AND PRACTICE OF 8UR- GERT. Eighth edit’n, improved and altered. With thirty-four plates. In two handsome octavo vol- umes, about 1000 pp., leather, raisdd bands. 50. THE PRINCIPLES AND PRACTICE OF SURGERY. By William Pirrie, F.R.S.E., Profesr of Surgery n the Universiiy of Aberdeen. Edited by John Neill, M. D., Professor of Surgery in the Penca. MedicalCollege,Surg’n to the Pennsylvania Hos- pital, &c. In one very handsome octavo vol. of 780 pages, with 316 illustrations, cloth, $3 lb. MILLER’S FRINCIFLES OF SURGERY. Fourth Ame- rican, from the Third Edinburgh Edition. In one large 8vo. vol. of 700 pages, with 340 illu.strations, cloth, $3 75. MILLER’S PRACTICE OF SURGERY. Fourth Ame- rican, from the last Edinburgh F.dition Revised by the. American editor. In one large 8vo. vol . of nearly 700 pages, with 364 illustrations: cloth, $3 7 5. I 26 Henry C. Lea’s Publications — [Surgery . (IROSS {SAMUEL D.), M.D„ Professor of Surgery in the Jefferson Medical Oollege of Philadelphia. SYSTEM OF SURGERY : Pathological, Diagnostic, Tlierapeiitic, and Operative. Illustrated by upwards of Fourteen Hundred Engravings. Fifth edition carefully revised, and improved. In two large and beautifully printed imperial octavo vol- umes of about 230D pp. , strongly bound in leather, with raised bands, $15. {Just Issued.) The continued favor, shown by the exhaustion of successive large editions ofthis great work, proves that it has successfully supplied a want felt by American practitioners and students. In tht present revision no pains have been spared by the author to bring it in every respect fully up tc the day. To effect this a large part of the work has been rewritten, and the whole en- arged bj nearly one-fourth, notwithstanding which the price has been kept at its former very moderate rate. By the use of a close, though very legible type, an unusually large amount of matter is jondensed in its pages, the two volumes containing as much as four or five ordinary octavos. This, combined with the most careful mechanical execution, and its very durable bind ing renders, it one of the cheapest works accessible to the profession. Every subject properly belonging bo the lomain of surgery is treated in detail, so that the student who possesses this work may be said to have in it a surgical library. We have uow brought our task to a conclusion, and have seldom read a work wiih the practical value of which we have been more impressed. Every chapter is so concisely put together, that the busy practitioner, when in dilficulty, can at once find the information he requires, llis work, on the contrary, is cosmopolitan, the surgery of the world being fully represented in it. The work, in fact, is so historically unprejudiced, and so eminently practical, that it is almost a false compli- ment to say that we believe it to be destined to occupy a foremost place as a work of reference, while a system of surgery like the present system of surgery is the practice of surgeons. The printingand binding of the work is unexceptionable ; indeed, it contrasts, in the latter respect, remarkably with English medical and surgical cloth-bound publications, which are generally so wretchedly stitched as to require re-binding before they are any time in use. — Dub. Journ. of Med. Sci,. March, 1874. Dr. Gross’s Surgery, a great w’ork, has become still greater, both in size and merit, in its most recent form. The difference in actual number of pages is not more than 130, but. the size of the page having been in- creased to what we believe is tecbnically termed '-ele- phant.” there has been room for considerable additions, which, together with the alterations, are improve- ments. — Land. Lancet, Nov. 16, 1872. It combines, as perfectly as possible, the qualities of a text-bf)ok and work of reference. We think this last edition of Qroas’s “Surgery,” will confirm his title of Primus inte,r Pares.” It is learned, schoJar-like. nie- thodical, precise, and exhaustive. We scarcely think any living man could write so complete and faultless a treaHse, or comprehend more solid, instructive matter in the given number of pages. The lalmr must have been immense, and the work gives evidence of great powers of mind, and the highest order of intellectual discipline and methodical disposition, and arrangement of acquired knowledge and personal experience. — M.Y. Med. Journ., Feb. 1873. As a whole, we regard the work as the representative “System of Surgery” in the English language. — St' Louis Medical and Surg. Journ., Oct. 1872. The two magnificent volumes before us afford a very complete view of the surgical knowledge of the day. Some years ago we had the pleasure of presenting the first edition of Gross’s Surgery to the profession as a work of unrivalled excellence; and now we have the re.sult of years of experience, labor. and study, all con- densed upon the great work before us. And to students or practitioners desirousof enriching their library with a treasure of reference, we can simply commend the purchase of these two volumes of immense research — Qincinnati Lancet and Observer, Sept. 1S72. A complete system of surgery — not a mere text-book of operations, but a scientific accountuf surgicallthcorv and practice in all its denartments. — Brit, and For. Med Chir. Rev., Jan. 1873. TJY THE SAME AUTHOR. A PRACTICAL TREATISE ON THE DISEASES, INJURIES, and Malformations of the Urinary Bladder, the Prostate Gland, and the Urethra. Third Edition, thoroughly Revised and Condensed, by Samuel W. Gross, M.D., Surgeon to the Philadelphia Hospital. In one handsome octavo volume of 674 pages, with 170 illus- trations : cloth, $4 50. {Just Issued.) For reference and general information, the physician or surgeon can find no work that meets their necessities more thoroughly than this, a revised edition of an ex- cellent treatise, and no medical library should be with- out it. Replete with handsome illustrations and good ideas, it has the unusual advantage of being easily comprehended, by the reasonable and practical mannei in which the various subjects are systematized and arranged We heartily recommend it to the profession as a valuable addition to the important literature of dis- eases of the urinary organs . — Atlanta Med. Journ.. Oct. 1876. It is with pleasure we now again take up this old work in a decidedly new dress. Indeed, it nmst be re- garded as a new book in very many of its parts. The chapters on ‘‘Diseases of the Bladder,” “Prostate Body,” and “Lithotomy,” are splendid specimens of descriptive writing; while the chapter on '‘Stricture” is one of the most concise and clear that we have ever read . — New York J/ed. Journ., Nov. 1876. J^T THE SAME AUTHOR. A PRACTICAL TREATISE ON FOREIGN BODIES IN THE AIR-PASSAGES. In 1 vol. 8vo., with illustrations, pp. 468, cloth, $ 75. jyRUITT {ROBERT), M.R.G.S.,^c. ■^THE PRINCIPLES AND PRACTICE OF MODERN SURGERY. A new and revised American, from the eighth enlarged and improved London edition . Illui - trated with four hundred and thirty -two wood engravings. In one very handsome octavo volume, ot nearly 700 large and closely printed pages, cloth, $4 00 ; leather, $5 00. All that the surgical student or practitioner could desire . — Dublin Quarterly Journal. It is a most admirable book. We do not know when we have examined one with more pleasure. — Boston Med. and Surg. Journal. In Mr. Druitt’sbook, though containingonly some seven hundred pages, both the principles and the jractice of surgery are treated, and so clearly and jerspicuously, as to elucidateeveryimportanttopic. We nave examined thebook mostthoroughly, and can lay that this euccessis well merited. His book moreover, possesses the inestimable advantages of having the subjects perfectly well arranged and clafsifled and of being written in a style at once clear ind succinct. — Am. Journal of Med. Sciences. Henry C. Lea’s Publications — (Surgery). 2t A SHHURSr {JOHN, Jr.), M.D., Prof, of Clinical Surgery, Univ. of Pa., Surgeon to the Episcopal Hospital, Philadelphia. THE PRINCIPLES AND PRACTICE OF SURGERY. Second edition, enl.arged and revised. In one very large and handsome octavo volume of over 1000 pages, with 542 illustrations. Cloth, $6; leather, $7. {Just Readi/.) Conscieatiousness and thoroughness are two very- marked trails of character in the author of this book. Out of these traits largely has grown the success of his mental fruit in the past, and the pre- sent offer seems in no wise an exception to what has gone before. The general arrangement of the vol- ume is the same as in the first edition, but every part has been carefully revi.sed, and much new matter added. — Phila. Med. Times, Feb. 1, 1S79. We have previously spoken of Dr. Ashhurst's work in terms of praise. We wish to reiterate those terms here, and to add that no more satisfactory representation of modern surgery has yet fallen from the press. In point of judicial fairness, of power of condensation, of accuracy and conciseness of expression and thoroughly good. English, Prof. Ashhurst has no superior among the surgical writers in America. — Am. Practitioner, Jan. 1S79. The attempt to embrace in a volume of 1000 pages the whole fieft of surgery, general and special, would be a hopeless task unless through the most tireless industry in collating and arranging, and the wisest judgment in condensing and excluding. These facilities have been abundantly employed by the author, and he has given us a most excellent treatise, brought up by the revision for the .second edition to the latest date. Of course this book is not designed for specialists, but as a course of general surgical knowledge and for general practitioners, and as a text-book for students it is not surpassed by any that has yet appeared, whether of home or foreign authorship. — N. Carolina Med. Journal, Jan. 1879. Ashhurn’s Surgery is too well known in this country to require special commendation from us. This, its second edition, enlarged and thoroughly revised, brings it nearer our idea of a model text- book than any recently published treatise. Though numerous additions have been made, the size of the work is not materially increased The main trouble of text-books of modern times is that they are too cumbersome. The student needs a book which will furnish him the most information in the shortest time. In every respect this work of Ashhurst is the model text-book— full, comprehensive and com- pact.— Jour of Med. and Surg., Jan. ’79. The favorable reception of the first edition is a guarantee of the popularity of this edition, which is fresh from the editor’s hands with many enlarge- ments and improvements. The author of this work is deservedly popular as an editor and writer, and his contributions to the jiterature of surgery have gained for him wide reputation. The volume now' offered the profession will add new laurels to those already won by previous contributions. We can only add that the work is well arrang. d, filled with practical matter, and contains in brief and clear language all that is necessary to be learned by the student of surgery whilst in attendance upon lec- tures, or the general practitioner in his daily routine practice.— Jfcf. Med. Journal, Jan. 1879. The fact that this work has reached a second edi- tion so very soon after the publication of the first one, speaks more highly of its merits than anything we might say in the way of commendation. It seems to have immediately gained the favor of stu- dents and physicians. — Cincin. Med. News, Jan. ’79. URYANT {THOMAS), F.R.C.S., Surgeon to Ouy’ 8 Hospital. THE PRACTICE OP SURGERY. Second Ainencan, from the Sec- ond and Revised English Edition. With Six Hundred and Seventy two Engravings on Wood. In one large and very handsome imperial octavo volume of over 1000 large and closely printed pages. Cloth, $6 ; leather, $7. (Just Ready.) This work has enjoyed the advantage of two thorough revisions at the hand of the author since the appearance of the first American edition, resulting in a very notable enlargement of size and improvement of matter. In England this has led to the division of the work into two volumes which are here comprised in one, the size being increased to a large imperial octavo, printed on a condensed but clear type. The series of illustrations has undergone a like revision, and will he found correspondingly impro\ed. The marked success of the work on both sides of the Atlantic shows that the author has suc- ceeded in the effort to give to student and practitioner a sound and trustworthy guide in the practice of Surgery; while the simultaneous appearance of the present edition in England and in this country affords to the American reader the benefit of the most recent advances made abroad in surgical science. There are so many text-books of surgery, so many written by skilled and distinguished bauds, that to ob tain the honor of a third edition in England is no light praise. Mr. Bryant merits this, by clearness of style, and good judgment in selecting the operations he re- commends, in his new editions he goes carefully over the old grounds, in light of later research. On these and many allied points, Mr. Bryant is a calm and un- partisan observer, and his book throughout has the great merit of maintaining the true scientific, judicial tone of mind. — Med. and Surg. Heporter, March 22, 1879. / The work before us is the American reprint of the last London edition, and has the advantage over the latter in being of more convenient size, and in being compressed into one volume. The author has rewrit- ten the greater part of the work, and has succeeded, in the amount of new matter added, in making it mark- edly di.-itinctive from previous editions. A few extra pages have been added, and also a few new illustrations introduced. The publishers have presented the work in a creditable style. As a conciso^nd practical manual of British surgery it is perhaps without an equal, and will doubtless always be a favorite text-book with the student and prac.itioner. — N. J'. Jltul. Record, .March 22, 1879. Another edition of this manual having been called for, the author has availed himself of the opportunity to make no few alterations in the substance as wed as in the arrangement of the work, and, with a view to its improvement, has recast the materials and re- vised the whole. We ourselvets are of the opinion that there is no better work on surgery extant — Cincinnati Med. News, March, 1879 Bryant’s Surgery has been favorably received from the first, and evidently grows in the esteem of the profession with each succeeding edition. In glanc- ing over the volume before us we find proof in almost every chapter of the thorough revision which the work has undergone, many parts having been cut out and replaced by matter entirely fresh. — N. Y. Med. Joitrn., April, 1879. Welcome as the new edition is, and as much as it is entitled to commendation, yet its appearance at this time is, in a ceriain sense, a matter of regret, as it will be in competition with another work, lately issued from the s.ime press. But, the difficult task of forming a judgment as to the relative merits of Bryant and Ashnurst we will not attempt, but pre- dict that, considering the liigh excellence of both, many others will likewise be icrced to hesitate long in making choice between them —Ciaciunati Lan- cet and Clinic, Maich 22, lo79. 28 Henry C. Lea’s Publications — {Surgery) J^RIGHSEN {JOHN E.), Professor of Surgery in University College, London, etc. THE SCIENCE AND ART OF SHROERY ; being a Treatise on Siir- gical Injuries, Diseases, and Operations. Carefully revised by the author from the Seventh and enlarged English Edition. Illustrated by eight hundred and sixty two en- gravings on wood. In two large and beautiful octavo volumes of nearly 2000 pages : cloth, $8 50 ; leather, $10 50. {Now Ready.) In revising this standard work the author has spared no pains to render it worthy of a continu- ance of the very marked favor which it has so long enjoyed, by bringing it thoroughly on a level with the advance in the science and art of surgery made since the appearance of the last edition. To accomplish this has required the addition of about two hundred pages of text, while the illustrations have undergone a marked improvement. A hundred and fifty additional wood-cuts have been inserted, while about fifty other new ones have been substituted for figures which were not deemed satisfactory. In its enlarged and improved form it is therefore pre- sented with the confident anticipation that it will maintain its position in the front rank of text-books for the student, and of works of reference for the practitioner, while its exceedingly moderate price places it within the reach of all. The seveath edition is before the world as the last word of surgical science. There may he monographs which excel it upon certain points, hut as a con- spectus upon surgical principles aud practice it is unrivalleL It will well reward practitioners to read it, for it has been a peculiar province of Mr. Erichsen to demonstrate the absolute interdepend- ence of medical and surgical science We need scarcely add, in conclusion, that we heartily com- mend the work to students that they may be grounded in a sound faith, and to practitioners as an invaluable guide at the bedside. — Am. Practi- tioner, April, 1878. It is no idle compliment to say that this is the best edition Mr. Erichsen has ever produced of his well- known book. Besides inheriting the virtues of i’s predecessors, it possesses excellences quite its own. Having stated that Mr. Erichsen has incorporated into this edition every recent improvement in the science and art of surgery, it would be a supereroga- tion to give a detailed criticism. In short, we un- hesitatingly aver that we know of no other single work where the student and practitioner can gain at oncesoclear an insight into the principles of surgery, and so complete a knowledge of the exigencies of surgical practice.— i/oncion Lancet, Feb. 14, 1878 For the past twenty years Erichsen’s Surgery has maintained its place as the leading text-book, not only in this country, but in Great Britain. That it is able to hold its ground, is abundantly proven by the tho- roughness with which the present edition has been revised, and by the large amount of valuable mate- rial that has been added. Aside from this, one hun- dred aud fifty new illustrations have been inserted, including quite a number of microscopical appear- ances of patholjgical processes. So marked is this change for the better, that the work almost appears as an entirely new one. — Med. Record, Feb. 23, 1878. Of the many treatises on Surgery which it has been our task to study, or our pleasure to read, there is none which in all points has satisfied us so Avell as the classic treatise of Erichsen. His polished, clear style, his free- dom from prejudice and hobbies, his u|^surpasscd grasp of his subject, aud vast clinical experience, qualify him admirably to write a model text-book. When we wish, at the least cost of time, to learn the most of a topic in surgery, Ave turn, by preference, to his work. It is a pleasure, therefore, to see that the appreciation of it is general, and has led to the appearance of another edi- tion. — Med. and Siirg. Reporter, Feb. 2, 1S78. Notwithstanding the increase in size, we observe that much old matter has been omitted. The entire Avork has been thoroughly Avritten up, and not merely amend- ed by a few extra chapters A great improvement has been made in the illustrations. One hundred and fifty new ones have been added, and many of the old ones have been redraAvu. The author highly appreciates the fiivor with which his work has been received by Ameri- can surgeons, and has endeavored to render bis latest edition more than ever Avorthy of their approval. That he hasj succeeded admirably, must, we think, be the general opinion. We heartily recommend the book to both student and practitioner. — A. Y.Med. .fournal, Feb. 1878. Erichsen has stood so prominently forward for years as a writer on Surgery, that his reputation is world wide, and his name is as familiar to the med- ical student as to the accomplished and experienced surgeon. The work is not a reprint of former edi tions, but has in many places been entirely rewrit- feu. Recent improvements in surgery have not es- caped his notice, various new operations have been thoroughly analyzed, and their merits thoroughly discussed. One hundred and fifty new wood-cuts add to the value of this work. — N. 0. Med. and Surg. Journal, March, 1878. TJOLMES [TIMOTHY], M.D., J-J- Surgeon to St. George's Hospital, London. SURGERY, ITS PRINCIPLES some octavo volume of nearly 1000 pages. {Just Issued.) This is a work which has been looked for on both sides of the Atlantic with much interest. Mr. Holmes is a surgeon of large and varied experience, and one of the best known, and perhaps the most brilliant writer upon surgical subjects in England. It is a book for students — and an admirable one — and for the busy general practitioner. It will giveastudent all the knowledge needed to pass a rigid examina- tion. The book fairly j ustifies the high expectations that were formed of it. Its style is clear aud forcible, even brilliant at times, and the conciseness needed to bring it within its properlimits has uotimpaired AND PRACTICE. In one hand- with 411 illustrations. Cloth, $6 ; leather, $7. its force and distinctness. — N. Y. Med. Record, April 14, 1876. It will be found a most excellent epitome of sur- gery by the general practitioner who has not the time to give attention to more minute aud extended works and to the medical student. In fact, we know of no one we can more cordially recommend. The author has succeeded well in giving a plain aud practical account of each surgical injury and dis- ease, and of the treatment which is most com- monly advisable. It will no doubt bedome a popu- lar workin the profession, and.especially as a text- book. — Cincinnati Med. News, April, 1876. ASHTON ON THE DISEASES, INJURIES, and MAL- FORMATIONS OF THE RECTUM AND ANUS: with remarks on Habitual Constipation. Second American, from the fourth aud enlarged London Edition. With illustrations. In one 8vo. vol. ol 28/ pages, clot h , ijid 2.7. SARGENT ON BANDAGING ANDOTHER OPERA- TIONS OF MINOR SURGERY. New edition, with an additional chapter on Military Surgery. One 1 2ino. vol. of 383 pagss, wit h 184 wood-cuts. Cloth, $1 7d. Henry C. Lea’s Publications — {Ophthalmology). 29 fJAMILTON {FRANK H.), M.D., Professor of Fractures and Dislocations, Ac., in Bellevue Hosp. Med. College, New York. A PRACTICAL TREATISE ON FRACTURES AND DISLOC^.- TIONS. Fifth edition, revised and improved. In one large and handsome octavo volume of nearly 800 pages, with 344 illustrations. Cloth, $5 75 ; leather. $6 75. {Lately Issued.) This work is well known, abroad as well as at home, asthe highest authority on its important subject — an authority recognized in the courts as well as in the schools and in practice — and again manifested, not only by the demand for a fifth edition, but by arrang-ements now in pro- gress for the speedy appearance of a translation in Germany. The repeated revisions which the author has thus had the opportunity of making have enabled him to give the mostcareful consid- eration to every portion of the volume, and he has sedulously endeavored in the present issue, to perfect the work by the aid of his own enlarged experience, and to incorporate in it whatever of value has been added in this department since the issue of the fourth edition. It will there- fore be found considerably improved in matter, while the most careful attention has been paid to the typographical execution, and the volume is presented to the profession in the confident hope that it will more than maintain its very distinguished reputation. There is no better work on the subject in existence, than that of Dr. Hamilton. It should be in the posses- sion of every general practitioner and surgeon. — The Am. Journ. of Obstetrics, Feb. 1876. The value of a work like this to the practical physi- cian and surgeon can hardly be over-estimated, and the necessity of having such a book revised to the latest dates, not merely on account of the practicalimportance of its teachings, but also by reason of the medico-legal bearings of the cases of which it treats, and which have recently been the subject of useful papers by Dr. Hamil- ton and others, is sufficiently obvious to every one. The present volume seems to amply fill all the requisites. We can safely recommend it as the best of its kind in the English language, and not excelled in*any other. — Joarn. of Nervous and Mental 2>isease, Jan. 1876. IDROWNE [EDGAR A.), Surgeon to the Liverpool Eye and Ear Infirmary, and to the Dispensary for Skin Diseases. HOW TO USE THE OPHTHALMOSCOPE. Being Elementary In- structions in Ophthalmoscopy, arranged for the Use of Students. "W ith thirty-five illustra- tions. In one small volume royal l2mo. of 120 pages : cloth, $1. {Now Ready.) This capita] little work should be in the hands of i could scarcely fail of understanding them. Equally ev-ry medical student, and we had aJmostsaid every .satisfactory are the directions for the use of the in- general practitioner. Its explanation of the optic-d strument and the suggestions to aid in interpreting principles on which the ophthalmoscope is founded, what is seen. — Detroit Med. Journ., ISov. 1877. is 80 clear and simple that the most stupid reader j pARTER [R. BRUDENELL), F.R.C.S., Ophthalmic Surgeon to St. George s Hospital, etc. A PRACTICAL TREATISE ON DISEASES OF THE EYE. Edit- ed, with test-types and Additions, by John Green, M.D. (of St. Louis, Mo.). In one handsome octavo volume of about 500 pages, and 124 illustrations. Cloth, $3 75. {Just Issued.) It would be difficult for Mr. Carter to write an unin- structive book, and impossible for him to write au un- interesting one. Even on subjects with which he is not bound to be familiar, hecan discourse with a rare degree of clearness and effect. Our readers will therefore not be surprised to learn that a work by him on the Diseases of the Eye makes a very valuable addition to ophthal- mic literature. . . . The book will remain one useful alike Jo the general and the special practitioner. — Lon doa Lancet, Oct. 30,1875. It is with great pleasure that we can endorse the work as a most valuable contribution to practical ophthal- mology. Mr. Carter never deviates from the end he has in view, and presents the subject in a clear and concise manner, easy of comprehension, and hence the more valuable. We would especially commend, however, as worthy of high praise, the manner in which the thera- peutics of disease of the eye is elaborated, for here the author is particularly clear and practical, where other writers are unfortunately too often deficient. The final chapter is devoted to a discussion of the uses and selec- tion ofspectacles, and is admirably compact, plain, and useful, especially the paragraphs on the treatment of presbyopia and myopia. In conclusion, our thanks are due the author for many useful hints in the great sub- ject of ophthalmic surgery and therapeutics, afield where of late years we glean but a few grains of sound wheat from a massof chaff. — New York Medical Recwd, Oct. 23, 1875. y^ELLS ( J. SOELBERG), ’ ^ Professor of Ophthalmology in King's College Hospital, Ac. A TREATISE ON DISEASES OF THE EYE. Third American, from the Fourth and Revised London Edition, with additions ; illustrated with numerous engravings on wood, and six colored plates. Together with selections from the Test-types of Jaeger and Snellen. In one large and very handsome octavo volume. {Pre 2 )ariug.) T A URENCE [JOHN Z.), F. R. C.S., Editor of the Ophthalmic Review, Ac A HANDY-BOOK OF OPHTHALMIC SURGERY, for the use of Practitioners Second Edition, revised and enlarged. With numerous illustrations. In one very handsome octavo volume, cloth, $2 75. T AWS.ON [GEORGE], F.R.C.S. Engl, Assistant Surgeon to the Royal London Ophthalmic Hospital, Moorflelds, Ac . IN,TURIES OF THE EYE, ORBIT, AND EYELIDS: their Imme. diate and Remote Effects. With about one hundred illustrations. In one very hand- some octavo volume, cloth, $3 50. 30 Henry C. Lea’s Publications — {Medical Jurisprudence). . JJURNETT {CHARLES H.), M.A , M.D., Aurjtl Surg to the Presb. tioftp., Surgeon-in-<.har ge of the In fir for Bis. of the Ear, Phila. THE EAR, ITS ANATOMY, PHYSIOLOGY, AND DISEASES. A Practical Treatise for the Use of Medical Students and Practitioners. In one hand- some octavo volume of 615 pages, with eighty-seven illustrations : cloth, $4 50 ; leather, $5 50. {Just Ready.) Recent progress in the investigation of the structures of the ear, and advances made in the modes of treating its diseases, wouldseem to render desirable a new work in which all the re- sources of the most advanced science should be placed at the disposal of the practitioner. This it has been the aim of Ur. Burnett to accomplish, and the advantages which he has enjoyed in the special study of the subject are a guarantee that the result of his labors will prove of service to the profession at large, as well as to the specialist in this department. Oa account of the great advances which have been made of late years in otology, and of the increased intf rest manifested in it, the medical profession will welcome this new work, which presents clearly and concisely its present aspect, whilst clearly indi- cating the direction in which further researches can be most profitably carried on. Dr. Burn tt from his own matured experience, and availing himself of the observations and discoveries of others, has pro- duced a work^which as a text-book, stands /recipe prineeps in our language. We had marked several pa-sages as well worthy of quotation and the atten- tion of the general practitioner, hut their number and the space at our command forbid. Perhaps it is bet- ter, as the book ought to be in the hands of every medical student, and its study will well repay the busy practitioner in the pleasure he will derive from the agreeable style in which many otherwise dry and mostly unknown subjects are treated. To the specialist the work is of the highest value, and his sense of gratitude to Dr. Burnett will, we hope, be proportionate to the amount of benefit he can obtain from the careful study of the book, and a constant reference to its trustworthy pages. — Edinbu gh Med. Jour., Aug. 1878. As the title of the work indicates, this volume treats of the anatomy and physiology of the ear, as well as of its diseases, and the author has taken special pains to make this difficult and complicated matter thoroughly clear and intelligible. The book is designed especially for the use of .-tudents and general practitioners, a nd places at their disposal much valuable material. Such a book as the pre- sent one, we think, has long been needed, and we may congratulate the author on his success in fill- ing the gap. Both s udent and practitioner can study the work with a grt at deal of benefit. It is profu-ely and beautifully illustrated.— iV. Y. Hos- pital Gazette, Oct. 15, 1877. The appearanceof thisbookis another proof of the rapidly increasing amount of honest, valuable work that is now being done in the various branches of medical science in this cou n try. Dr. Burnett is to be commended for having written the best book on the subject in the English language, and especially for the care and attention he has given to the scientific side of the subject. — N. Y. Med. Journ., Dec. 1877. rfAYLOR {ALFRED S.),M.D., Lecturer on Med. Jurisp. and 0 herniary in Guy's Hospital. POISONS IN RELATION TO MEDICAL JURISPRHDENCE AND MEDICINE. Third American, from the Third and Revised English Edition. In one large octavo volume of 850 pages ; cloth, $5 50 ; leather, $6 50. {Jttst Issued.) The present is based upon the two previous edi- tions ; * ‘but the completerevision rendered necessary by time has converted it into a new work.” This statement from the preface contains all that it is de- sired to know in reference to the uew edition. The works of this author are already in the library of every physician who is liable to be called upon for medico-legal testimony (and what^neis uot?),sothat all that is required to be known about the present book is that the author has kept it abreast with the times. What makes it now, as always, e.specially valuable to the practitioner is its conciseness and practical character, only those poisonous substances J^Y THE SAME AUTHOR. being described which give rise to legal Uvestiga- tious. — TAc Clinic, JNov. 6, 1875. Dr. Taylor hat brought to hear on the compilation of this volume, stores of learning, experience, and practical acquaintance with Lis subject, probably far beyond what any other living authority on toxicol- ogy could have amassed or utilized. He has fully sustained his reputation by the consummate skill and legal acumen he has displayed in the arrange- ment of the subject-matter, and the result is a work on Poisons which will be indispensable to every stu- dent or practiiiouer in law and medicine. — The Dub- lin Journ. of Med